Figure 6-01 On open water, away from marked channels, one way a person at the helm can maintain the proper course is by keeping an eye on the compass. When possible, sight on a distant object that is ahead in the direction that you want to go—but do not use clouds or other boats.
Helmsmanship • Propeller & Rudder Actions • Single-Screw Inboard Maneuvering • Maneuvering in Tight Quarters • Dock Lines & Their Uses • Twin-Screw Maneuvering • Maneuvering with Directed Thrust
Boat-handling ability is at the very heart of good seamanship. Some of the finest exhibitions of boat handling are given by boaters who have never read a printed page on the subject of seamanship. Their proficiency, developed over long years of meeting every conceivable situation, manifests itself almost as an instinct, prompting the skipper to react correctly whether he can think the problem out beforehand or not.
A recreational boater, particularly a novice, will not have these years of experience. He can gain much from a study of the basic factors involved, and then build up his experience. In approaching a study of the principles of boat handling, keep in mind that the goal is to understand why your boat reacts the way it does when you are out there handling it. If your craft stubbornly refuses to make a turn under certain conditions, or persists in backing one way when you want it to go the other, you are less likely to make the same mistake repeatedly once you understand the reasons behind its behavior.
HELMSMANSHIP
The ability to steer well—called HELMSMANSHIP, whether involving men or women—is a quality that cannot be learned from a book or in a classroom. However, understanding the basic principles of boat handling will make it easier for you to perform in a variety of situations.
It is important to realize that boats are nearly as individualistic as people, particularly in their steering characteristics. Deep-draft and shallow-draft vessels handle differently. Boats that steer by changing their thrust direction (i.e., those powered by outboards, sterndrives, pod drives, or jet drives) or by using bow or stern thrusters respond differently from boats steered by rudders. The response of a heavy displacement hull to helm changes is quite unlike that of a light planing hull.
The secret of good helmsmanship is to know your boat. If you skipper your own craft, this comes quickly as you gain experience with it. If you take the wheel or tiller of a friend’s boat, however, take it easy with helm changes until you get a “feel” for the craft’s responses.
Steering by Compass
Boats are often piloted by running compass courses; see Figure 6-01. You must keep the compass lubber’s line on the mark of the card that indicates the course to be steered. If the course to be steered is 100° and the lubber’s line is momentarily at 95° you must “swing the boat’s head” with right rudder 5° to the right, to bring the lubber’s line around to 100°. Remember, the card stands still while the lubber’s line swings around it. You have to steer to port or starboard as necessary to move the lubber’s line toward the desired heading indication to get on course.
When a vessel swings with a change in course, an inexperienced helmsman tends to allow it to swing too far due to the momentum of the turn and the lag between a turn of the wheel and the response of the craft. The experienced helmsman knows how to steady on the new course without oversteering. In almost all power cruisers, this requires that the helmsman return the rudder to the neutral, midships position before the craft reaches the intended new heading. You will often need to use a slight amount of opposite rudder to check the boat’s swing.
A zigzag course brands the helmsman as inexperienced. The goal is a straight course; this can be achieved, after the boat has steadied, by only slight movements of the wheel. An experienced boater at the helm anticipates the vessel’s swing and, turning the wheel slowly and deliberately, makes corrections with little rudder instead of going well off course before correcting.
A good helmsman will also turn the wheel slowly and deliberately. The actual manner of steering is a characteristic of each craft, and is learned only by experience.
When holding a course, it helps to pick out a distant landmark or other fixed object, if there is one, to steer by. At night, a star can be used, but remember that the apparent positions of stars change over a period of hours. This helps to keep a straight course, as a boat compass is smaller and less steady than one aboard a large vessel. Avoid steering on cloud formations; these move with the wind and change shape. Drop your eyes periodically to the compass to check your course, and always remember to look back frequently at the aids or landmarks you have passed, making sure that you remain on your proper track. Even though you may be steering quite precisely toward your objective, the wind or a crosscurrent may be setting you to one side. If in a narrow channel, you could soon be out of it and aground.
If steering by an electronic device such as an autopilot or following the waypoint-to-waypoint line or “highway screen” on an electronic chartplotter, always monitor the off-course error, called CROSSTRACK ERROR, calculated by your GPS or chartplotter.
BASIC PRINCIPLES OF BOAT HANDLING
The proper approach to boat handling is a balance of study and practice. Learn all you can about the principles by which average boats respond under normal conditions; supplement this with experience in your own boat and others. In this way you will learn to act so that the controlling elements aid rather than oppose you.
In boat handling, there are three primary types of powered craft to consider: inboard single-screw, inboard twin-screw, and outboard (as well as sterndrive, pod drive, and jet drive), whether single or multiple. The first two use a rudder or rudders in combination with the accelerated waterflow from the propeller or propellers; the last uses directed water thrust, usually without a rudder. The handling characteristics of each type are different from the others, but as the single-screw, single-rudder inboard is the basic type, we will cover it in considerable detail. Note that the principles apply equally for a sailboat being moved through the water by inboard auxiliary power.
No two boats will behave in an identical manner in every situation. Just how a boat performs depends on many things, among them the shape of the hull’s underbody; the shape, position, and area of the rudder; the boat’s trim, speed, weight, and load; the strength and direction of wind and current; and the nature of the sea.
Basic Boat-Handling Terms
Certain basic boating terms apply specifically to boats equipped with one or more engines—whether inboard (mounted within the hull), outboard (mounted on the transom and detachable), or the combination inboard-outboard (I/O) type, also called sterndrives. Thrust for the movement of the boat through the water is achieved by the rotation of a propeller (or “screw”), which draws in water from ahead and pushes it out astern. A boat with one propeller is termed a single-screw type. Boats with two propellers are referred to as twin-screw craft. Sailboats fitted with an engine are called auxiliaries; their handling characteristics are similar to those of a single-screw powerboat, although their engines are usually of lesser horsepower.
Steering is accomplished in one of two ways. An inboard engine operates according to a “fixed-screw”: Turning a rudder or rudders diverts the thrust developed by the propeller(s), which in turn turns the boat; see Figure 6-02. An outboard- or I/O-powered boat operates without a rudder. Pivoting the motor and propeller or the outdrive unit redirects the propeller thrust, changing the boat’s direction.
Figure 6-02 Left rudder on a boat going ahead (above, left) causes the stern to move to starboard and the bow to turn to port. Left rudder while going astern (above, right) moves the stern to port. The bow initially moves straight backward in this case, and then turns to starboard.
Just as a person has a left and right side, a boat has a left—or port—side and a right—or starboard—side as you stand on board and look forward. The left and right sides of a person stay the same no matter from which direction you look; similarly, turning around while on board and looking aft will not change the boat’s port and starboard sides.
A boat is said to be making headway when it is going forward in the water and sternway when it is backing up. A boat is turning to port when its bow is moving to the left when making headway. A boat is said to be going to port when making sternway if its stern is moving to the left.
The terms RIGHT RUDDER and LEFT RUDDER refer to how the bow would turn if the boat were making headway. The terms are also used for the same position of the rudder when making sternway. A boat with left rudder applied will turn its bow to port while making headway and swing its stern to port when making sternway. In Figure 6-02, the boat has left rudder in both cases. Right rudder would be just the opposite.
A BALANCED RUDDER is one whose blade surface lies partly ahead of its rudderstock; refer to Figure 1-11. (An UNBALANCED RUDDER, seldom seen, is one whose blade surface is fully behind the rudderstock.) While the portion of this forward balance area may be only 20 percent of the total rudder area, it exerts considerable effect in taking strain off the steering gear and making the steering easier.
Right- & Left-Hand Propellers
Propellers are said to be RIGHT-HAND or LEFT-HAND depending on the direction they turn (looking forward from aft of the propeller). The difference is important because propeller rotation has a considerable bearing on how a boat maneuvers, especially when reversing. A propeller that turns clockwise when driving the boat ahead is right-handed; one that turns counterclockwise is considered left-handed. To determine the “hand” with the boat out of the water, stand astern of the propeller and look forward at the driving face of the blades; the forward edge of each blade cuts through the water. If the propeller will turn clockwise when driving the boat forward, it is right-handed; if it would turn counterclockwise, it is left-handed. In Figure 6-03, the propeller at left is left-handed; the one at right is right-handed. It is not always easy to determine the hand of a propeller by looking at the rotation of the engine alone. The engine is connected to a transmission that may change engine rotation depending on its reduction gearing. The rotation of the coupling connecting the transmission to the propeller shaft is, however, a true indication of the propeller rotation. If, looking forward toward the transmission from aft of it, the shaft and coupling rotate clockwise when the transmission is in forward, then the shaft has a right-hand propeller.
Most, but not all, single-screw boats have right-hand propellers. In the maneuvering situations below, the propeller on a single-screw craft is right-handed unless otherwise noted.
Twin-screw craft almost always have the tops of the blades turning outward when going ahead for best maneuverability. Figure 6-03 can be viewed as the two propellers of a twin-screw craft; the port engine will turn a left-hand propeller, and the starboard engine a right-hand propeller. Skippers sometimes refer to propellers as “wheels,” especially when describing right- or left-handedness, but since most of the discussion in this chapter is about steering, we will use “propeller” exclusively.
Figure 6-03 If you stand at the stern of a boat that is out of the water and look at its propeller, you will be looking at the driving face of the propeller blades. If the propeller must turn to the right (clockwise) to push water toward you, the propeller is right-handed. If it would have to turn in the opposite direction for the same effect, it is left-handed.
Hull Shape
In addition to propeller and rudder configuration, the hull shape of a boat has a strong influence on how it handles. Given the same wind and sea conditions, a trawler with its heavy displacement hull and deeper draft will behave differently than a lighter sport-fishing boat with its shallower draft, planing hull, flying bridge and, possibly, tuna tower; see Figures 6-04 and 6-05.
Figure 6-04 A deep-draft displacement hull, A, will tend to be set off course by adverse water currents, but its low freeboard and superstructure offer less resistance to the wind. Conversely, a typical planing hull, B, floats high in the water, and a wind on the beam will result in considerable leeway.
Displacement-type hulls are heavily built and have a large load-carrying capacity, but are limited in the speed at which they can be driven through the water. Sailboats, recreational trawlers, and many large yachts fall into this category. Planing-type hulls are generally lighter. They have less draft and can be driven through the water fast enough to create a vertical force beneath the hull sufficient to lift a portion of the bottom clear of the water, reducing drag. As a planing hull slows down, it reaches a point where it reverts to displacement mode.
Figure 6-05 This sport-fishing boat with its planingtype hull has only part of its hull in contact with the water when it is on a plane.
Wind & Current
A boat’s handling characteristics are affected by wind and current no matter what type of hull and power combination it has. Keeping a course or maneuvering in close quarters may be straightforward on a calm day during a slack tidal current, but the boat may become quite ill-mannered when coping with a stiff crosswind or crosscurrent. Since bows on many powerboats are higher than the sterns, they tend to fall off the wind when backing. A bow or stern thruster can be helpful;.
Hull type has the most effect on how a boat reacts to the current. Displacement-type hulls with considerable draft are affected by current to a greater extent than shallower-draft, lighter, planing-type hulls. Water is much denser than air, so a half-knot crosscurrent may have more effect on a displacement cruiser than a 15- to 20-knot wind (a moderate to fresh breeze). On the other hand, given the same conditions, a planing-type hull with a high tuna tower could be more affected by wind than by current. But neither a displacement nor a planing boat can remain unaffected by either the wind or the current, one or the other of which will significantly affect the boat’s maneuverability. This becomes most apparent while running at low speed in close quarters.
Two boats of roughly the same size, one with a considerable hull draft forward but little aft and another with relatively greater draft aft but more superstructure forward, will have radically different handling qualities. The governing factor is the relative area presented above the water to the wind, compared with the areas in the water, both forward and aft.
Helmsmen Must Develop Judgment
From the above and other variations in behavior, it is obvious that a boater must develop judgment based on understanding his boat and the forces acting on it. Combinations of conditions can be infinite, so he or she must be able to appraise the situation and act promptly.
Try to foresee possibilities, and have solutions in mind before problems arise. For instance, if you are running down a channel with a strong wind on your beam and you have the choice of which side of the channel to use, the windward side is the better bet. Should your engine stop or your steering fail, you will have more of a chance to get an anchor down before going aground on the leeward side.
By the same reasoning, you shouldn’t skirt the windward side of a shoal too closely. Or suppose that you are approaching a bridge (see Figure 6-06), with a narrow draw opening and a strong wind or current pushing you along. If you approach the opening at an angle and power fails, you will be in a jam. But if you think to straighten out your course while still some distance away, so that you will be shooting down the center of the opening in alignment with it, you will be safer because your straight course will carry you through in the clear.
In developing your “boat sense,” draw from as many sources as possible. Watch how experienced boaters handle their craft, but allow for differences in your own boat when you try similar maneuvers. And it almost goes without saying: if you are at the helm of a strange boat, go more slowly than normal, taking additional precautions.
Figure 6-06 When approaching a bridge with a narrow draw, aim for the center of the opening, so that if power should fail, your course will tend to carry your boat through in the clear.
UNDERSTANDING PROPELLERS & RUDDERS
When under power, boats are driven through the water by the action of their propellers, which act like pumps—drawing in a stream of water from forward (when going ahead), and expelling it astern. Moving these streams of water aft creates an opposite forward thrust at the propellers, which is transmitted to the boat through the propeller shaft and its supporting structure. This drives the boat forward.
How Propellers Create Thrust
The curved blades of a propeller are similar to other curved foils found on boats, including a sailboat’s sail or fin keel. When such a foil passes through a fluid, the flow is divided into two streams, one on either side of the foil. When a rudder is in a straight position, the water flows evenly on both sides. Turning the rudder causes an uneven flow, building pressure on one side and reducing it on the other. This pressure differential creates what is called lift. The rudder—and the stern to which it is attached—moves (is “lifted”) toward the low-pressure side, which turns the bow in the opposite direction.
A propeller blade creates force similarly. If propeller blades were flat rather than curved, and if the blades simply spun around without any angle to their direction of travel, the propeller would turn through the water like a disk, with equal flow on each side. However, this is not the case. The blades of a propeller are both curved and angled; as they pass through the water, they create lift. There is a low-pressure area on the side of the blade facing forward, and a high-pressure area on the side facing aft.
Although the water drawn into the propeller does not actually flow from directly ahead in a thin column, we can consider this to be the case for our purposes here. As the propeller ejects water, it imparts a twist or spiral motion to that water. (The direction of rotation is dependent on the way the propeller turns.) The flow of water into and away from the propeller is called the SCREW CURRENT.
Suction & Discharge Screw Currents
Regardless of whether the propeller is rotating to move the boat ahead or astern, the part of the current that flows into the propeller is called the “suction screw current.” The part of the current ejected from the propeller is called the “discharge current”; see Figure 6-07. Discharge current, spiral in motion, is a compact stream of water that exerts greater pressure than the broader suction current.
Figure 6-07 With a propeller turning ahead, suction screw current is developed by the water flowing toward the propeller, and discharge current is driven out astern.
Placing the rudder behind the propeller in the discharge current increases the steering effect because the rudder is acting in an accelerated flow. (Of course, there is a small rudder action from any flow of water past it even if the propeller is not turning.) A twin-screw cruiser has twin rudders, one behind each propeller, keeping the rudder blades directly in the propellers’ discharge currents.
The pressure difference created by the propeller blade creates lift, and its force is roughly perpendicular to the blade itself. Lift can be divided into two components—a thrust component in the direction of travel and a torque component in the opposite direction of propeller rotation; see Figure 6-08. You can easily see the effect of propeller torque when a runabout with a large engine accelerates; as the propeller begins to accelerate, the boat tends to dip on one side (generally on the port side with a right-hand propeller).
There is also WAKE CURRENT—a body of water that is carried along by a vessel due to the friction on its hull as it moves through the water. This has its maximum effect at the surface, and little effect at keel depth.
Figure 6-08 The blades of a propeller act as foils, providing lift, thrust, and torque.
Unequal Blade Thrust
Turning propellers not only create forward or reverse thrust with their discharge current, they also produce forces that tend to push the propeller to one side or the other, depending on the direction of rotation.
This effect is most noticeable on inboard boats that have a propeller shaft set through the hull at an angle to the horizontal. Since the propeller is attached to the end of this shaft, it is positioned at the same angle, and the water that flows into it meets the blades at different angles depending on whether they are on the downward or upward arcs of their rotations. The pitch of the blades as manufactured is the same, of course, but the effective pitch of one blade is increased, while the other is reduced. For example, a forward-turning right-hand propeller would have the pitch of its starboard (descending) blade increased, while the pitch of the port (ascending) blade would be decreased. The relatively greater blade pitch on the starboard side creates a stronger thrust on that side; see Figure 6-09. The importance of this factor is reduced as the shaft angle is decreased, and naval architects sometimes take pains to have the engine installed as low in the hull as possible so as to keep the propeller shaft nearly parallel to the flow of the water past the blades. This contributes to propeller efficiency and is a factor worth considering if it is consistent with other design requirements. In practical terms, the effect of unequal blade thrust varies with each design.
Figure 6-09 A propeller shaft at an angle to the horizontal has the effect of increasing the pitch of the descending blade relative to that of the ascending blade. This produces greater thrust to starboard in a right-hand propeller. A left-hand propeller would produce a greater thrust to port.
Effect of Unequal Blade Thrust
The relatively greater blade pitch on the starboard side creates a stronger thrust on that side. Unless other factors contravene, the stern of a single-screw boat with a right-hand propeller thus has a natural tendency to go to starboard when the propeller is going ahead. The opposite effect occurs when the propeller is reversing.
When such a craft has headway, its bow tends to turn to port, and a certain amount of right rudder may be needed to maintain a straight course. To correct this tendency, a small trim tab may be attached to the after edge of the rudder and bent to an angle that provides the proper compensation.
The effect of unequal blade thrust is so small for some boats as to be negligible, and quite pronounced on other craft. With left-hand propellers, the effect is, of course, just the opposite of that described above.
However, when the shaft angle is parallel to the flow of water into the propeller, another effect, the paddle wheel, or PROPWALK, may come into play. As an outboard motor is progressively raised, the propeller will eventually break the surface of the water. As this point is approached, a blade sweeping across the top, fanning through aerated water, will not pull as hard in a sideways or propeller torque direction as the fully submerged blade sweeping across the bottom of the propeller arc. This will cause a right-hand rotation propeller to “walk” to the right, much as a paddle wheel would do. This action in turn tries to pull the aft end of an outboard or sterndrive boat to the right, causing the boat to go into a left-hand turn, if not resisted at the steering wheel.
Unequal blade thrust becomes more of a concern to light single-engine craft at high speeds, when the propeller is elevated closer to the water surface; the paddle wheel (propwalk) effect will eventually dominate any steering torque situation.
Ventilation & Cavitation
Since all but a few high-speed, surface-piercing propellers (see Figure 6-10) rely on the smooth flow of water over their blades to create lift, a slight disturbance to this flow limits the overall efficiency of the propeller.
Ventilation occurs when air from the water’s surface or exhaust gases are sucked into the discharge current. The propeller then loses its grip on the water and over-revs, losing much of its thrust. Trying to turn an outboard-powered boat too tightly at too high a speed often results in propeller ventilation.
Figure 6-10 A high-performance system, such as the Arneson Drive, is designed to reduce drag while enhancing positive-thrust steering. It uses surface-piercing propellers.
Cavitation usually occurs at the tip of a propeller that is turning too fast. A spot on the tip of a propeller blade travels farther and faster during each revolution than does one near the hub. As the propeller rpms increase, the tip reaches a point where water simply can’t flow past the tip without creating a vacuum sufficient to cause the formation of water vapor bubbles: see Figure 6-11, A. As these water vapor bubbles move along the surface of the metal, they eventually find an area of higher pressure where they collapse and cause damage. When collapsing, the bubbles release their stored energy onto the metal, acting like tiny jackhammers; the result is known as “cavitation burn”; see Figure 6-11, B.
Figure 6-11 Cavitation results from a partial vacuum formed, A, by the blades of a propeller, with a consequent lost of thrust. There is also the danger of damage to the propeller when the cavitation bubbles collapse, as shown in B.
Cavitation may result from a number of causes, including nicks in the leading edge, sharp leading-edge corners (as shown), improper polishing, poor propeller design, severely bent blades, broken blade tips, or ventilation.
How a Rudder Acts
Most inboard boats have a vertical rudder blade located at the stern, attached to a rudderpost that extends through a watertight stuffing box into the boat. Movement of the steering wheel turns the rudder to port or starboard. As described earlier, turning the rudder develops a higher pressure on one side of the rudder blade and a lower pressure on the other, creating lift. As the rudder is pulled toward its own lower-pressure side, it takes the stern of the boat with it.
Steering wheels on boats are rigged in such a way that they turn with the rudder—turning the helm to port turns the rudder to port. Turning the helm to port therefore gives left rudder; this then moves the stern to starboard, so that the bow in effect moves to port, starting a turn to the left. Conversely, turning the helm to starboard gives right rudder, throwing the stern to port, so that the boat then turns to starboard (to the right). On sailboats with tillers, the opposite is true.
Propeller Current’s Action on Rudder
If a boat is motionless in the water (regardless of motion with respect to the bottom caused by wind or current), turning the rudder will have no effect—there must be a flow of water past the rudder for it to exert a force on the stern of the craft. However, if the propeller is turning, the situation is quite different. Now the rudder blade is directly in the discharge current of the propeller, which is pumping a strong stream of water astern. Turning the rudder to one side deflects the stream, creating a thrust to the opposite side. Small rudders are effective when there is considerable propeller current or when the boat is moving at high speed, but they develop little turning force at slow speeds or when the propeller is not turning. Sailboats and most single-prop, heavy powerboats have large rudders and respond to the helm adequately at slow speeds.
At very slow propeller speeds, the boat’s headway may not be sufficient to provide steering control in wind or current. Take, for example, a strong wind on the port beam. Even with the rudder hard over to port, it may not be possible to turn into the wind until the propeller is speeded up enough to exert a more powerful thrust against the rudder blade. As a vessel travels through the water, the minimum speed at which it can be controlled is what is meant by STEERAGEWAY.
Turning Circles
When any boat has headway and the rudder is put over to make a turn (to starboard, for example), the stern is first pushed to the opposite side (in this example, to port). The boat then tends to slide off obliquely, in a crablike fashion. Its momentum will carry it a short distance along the original course before settling into a turn, in which the bow describes a smaller circle than the stern; see Figure 6-12. The PIVOT POINT is usually one-fourth to one-third of the boat’s length aft of the stem (see Figure 6-13), varying with boat trim and from one boat to the next.
While there is always a loss of speed when making a turn, the size of a boat’s turning circle varies little with changes in speed, assuming a given rudder angle.
Figure 6-12 When a boat has headway and its rudder is turned to one side to make a turn, the stern moves in the opposite direction. Then, after sliding obliquely along the course from 1 to 2, it settles into a turn in which the bow follows a smaller circle (solid red line) than the stern (dotted red line).
The radius of the turning circle is much larger for single-screw inboard boats than for outboards (or sterndrive boats) because the shaft and propeller of the inboard are fixed on the centerline and cannot be rotated. A twin-screw inboard, on the other hand, provides excellent maneuverability, as will be seen later.
Figure 6-13 With forward motion, when the helm is put over to one side, a boat pivots around a point about one-third of its length from the stem. Note that this causes the stern to swing in a wider arc than the bow.
It is important to consider the position of the rudder with respect to the pivot point of the hull when the boat is reversing. In this case, the pivot may be about one-fourth of the hull length from the transom; see Figure 6-14. Therefore, the rudder is acting on a much shorter lever arm as it tries, sometimes in vain, to swing the hull off course.
Figure 6-14 When backing down with the rudder to port, the pivot point is about one-quarter of the boat length forward of the stern. The bow, therefore, describes a wider arc than the stern.
When the boat has sternway (reversing), there is no powerful discharge current past the rudder, only the weaker, more diffuse suction screw current. The rudder normally would be turned to port (left rudder) to turn the stern of the boat to port; right rudder should normally turn the stern to starboard in backing. Under certain circumstances, the effect of the reversing propeller “walking” itself the other way may more than offset the steering effect of the rudder.
The stern of a boat with a left-hand prop may actually continue to turn to the right, for example, despite left rudder. Water depth also has an effect on a boat’s steering. Even though the keel may be a foot or so above bottom, a boat’s response to rudder action in shallow water is almost always sluggish.
Keep Stern Free to Maneuver
If a boater understands the underlying difference between the steering of a boat and a car, he will be aware of the need to keep the stern free to maneuver in close quarters. The stern must have room to swing in the opposite direction from that in which the bow is being turned. This is especially important when the craft lies close to a pile or solid vertical surface; see Figure 6-15.
Figure 6-15 With right rudder, as the boat moves from 1 to 2, the stern is driven against the piles, with risk of damage. The rudder should be centered until the boat is clear (or better yet, the boat should be backed away from the face of the pier after a nudge forward to get the bow in and stern out).
This is also very important when towing either a skier or another boat. To ensure the maneuverability of the towing craft, a towline must be attached forward of the stern; see Figure 6-16.
Figure 6-16 A towline should be attached to a fitting well forward of the transom. This will allow the stern to swing more freely to either side for turning and provide greater overall maneuverability.
The Tendency to Stray Off Course
Some boats require varying rudder angles to compensate for the tendency to wander from a straight course. Depending on differences in construction, arrangement of rudder blade, and the hand of the propeller, the bow may fall off to port or to starboard.
For example, a certain group of boats of almost identical design had a strong tendency to pull off course to port. In some of them, the condition was corrected simply by lowering the rudder blade, without changing its size or shape but merely by lengthening the stock an inch or two.
Before that correction, the boats would make a quick and easy turn to port but would resist turning to starboard. As a matter of fact, unless steering controls were rigged with worm and gear to hold the wheels against pressure on the rudders, the boats would swing into a short circle to port the instant the wheels were left unattended. This exaggerated condition is far from normal, but it does illustrate the handling characteristics the helmsman must pay attention to, especially in an unfamiliar boat.
PROPULSION “PODS”
A recent design feature of many large ships is the use of propulsion “pods.” These are large streamlined bodies beneath the after part of the hull where propellers would normally be. Each pod contains a large electric motor that drives a forward- or aft-facing propeller. The pods can be rotated horizontally through 360° for steering; there are no rudders. Power is supplied by electrical cables from several generators driven by multiple, large diesel engines or gas turbines. The advantages are vastly increased maneuverability and the flexibility to locate the power-generating machinery anywhere in the ship. Increased fuel efficiency is achieved—only those engines or turbines and generators need be run that are sufficient to meet the power needs of the moment.
Most ships have two pods, but some will have three or four, with the additional pods being fixed. Vessels range in size from 40,000 to 142,000 gross tons or more. Individual pods are rated at 9,000 to 21,500 horsepower (6.7 to 16 MW).
A generally similar concept has been developed for medium-size recreational craft.
Steering with Propeller Thrust
Here is a procedure that can often be helpful. In close quarters, a boat can often be turned in a couple of lengths by applying brief bursts of engine power; see Figure 6-17. If, for example, the rudder is set hard to starboard (right rudder) while the craft has no headway, and the throttle is suddenly advanced significantly, then quickly closed, the stern can be kicked around to port before the boat has a chance to gather significant headway. The exact technique of turning in limited space is described in detail later in this chapter.
Figure 6-17 When a boat with a right-hand prop is dead in the water, engaging forward gear walks the stern to starboard. The amount of movement depends upon the boat and the throttle applied. If the rudder is put over to port, the movement is greater.
BOAT HANDLING WITH A SINGLE SCREW
While this section focuses on the handling of single-screw boats, twin-screw boats and craft using directed thrust—outboard motors, sterndrives, pod drives, and jet drives—are also considered in this chapter. Although single-screw inboard-engine boats may be in the minority of modern small craft, the basic principles of boat handling are best explained by first considering the actions and reactions of a craft with one inboard engine, one shaft, one propeller, and one rudder.
A single-screw inboard boat relies on water flowing past the rudder for maneuvering power. This is provided by the movement of the boat through the water and by the discharge current from the propeller (or suction current if backing down). How well your boat responds to the helm in any given situation will depend largely on constant factors such as unequal blade thrust, propwalk, and hull type. The variable factors are wind, current, and the amount of rudder angle being used.
Every time you leave your berth, certain basic maneuvers are necessary—getting underway, turning, stopping, and backing down. Next is a description of how to perform these maneuvers in a single-engine inboard boat with a right-hand propeller. In addition, you will learn about why your boat sometimes seems to have a mind of its own.
Gathering Headway
Getting underway should be straightforward, but when you put the boat into forward gear with the rudder centered, it may not behave as you would expect. When you shift into forward gear and the propeller starts to turn ahead, unequal blade thrust tends to move the stern to starboard. This can be frustrating when pulling away from a starboard-side berth. If you don’t get your boat far enough away from the pier or wharf, the stern may swing in and hit it.
Compensating by using right rudder may help, but it could also hamper the maneuver of getting away from the structure. The proper way to depart a wharf or pier is to back out—here the natural tendency of a boat will pull the stern out, and when the boat is clear of the structure, it can go forward, parallel to the wharf or pier face, at an adequate distance from it. If there is any tendency for wind or current to pin the boat against the wharf or pier face, go ahead on an after bow spring to get the stern out.
As the boat gathers headway, the flow of water past a centered rudder acts to resist any turning action of the craft. This counters the effect of unequal blade thrust, and the average boat will normally hold course in a straight line fairly well.
From a purely theoretical standpoint, unequal blade thrust with a right-hand propeller should tend to move the stern to starboard and the bow to port. Once underway, the effect of unequal blade thrust is quite slight. Only in comparatively few cases will unequal blade thrust have a pronounced effect on steering, and in these it can be corrected by a small rudder tab.
Turning
Now that your boat has headway, assume the rudder is turned to starboard. The water flowing past the hull strikes the rudder on its starboard side, forcing the stern to port. The propeller’s discharge current intensifies this effect by acting on the same side, and the boat’s bow turns to starboard, the same side on which the rudder is set.
How fast a boat will react to its helm depends on the size of the rudder and on hull shape, but the most influential factor is how fast water is flowing past the rudder. At slow speeds, with the engine idling or turning slowly, a heavy boat will register a considerable lag between the time its helm is put over and the time the boat begins to turn. At idle speeds, there is less water flowing past the rudder, and the propeller discharge current is weak; it may take a boat several seconds to begin a turn. You may also have to give the boat considerably more rudder to get the same response you achieve at higher speeds.
Of course, the opposite is also true. A boat traveling fast experiences a powerful flow of water past the rudder; with a strong propeller discharge current, it responds much more quickly to helm movement. At speed, a light, fast, planing-type inboard has a very positive feel to the helm, with no noticeable lag between helm movement and turning.
The boat’s turning radius is determined by how much the helm is turned at both high and slow speeds. How quickly the boat responds to helm movement is basically a factor of how fast it is moving.
Stopping
A boat has no brakes—stopping is achieved by reversing the propeller rotation. Assume that your boat has headway, with the rudder centered, propeller turning in reverse. The rudder has decreasing steering effect as the boat slows, and unequal blade thrust of the reversed propeller tends to throw the stern to port. At the same time, on some boats the propeller blades on the starboard side are throwing their discharge current in a powerful column forward against the starboard side of the keel and bottom of the boat, with little on the port side to offset this pressure. This also adds to the forces moving the stern to port.
If wind and current permit, a skipper should make a port-side approach to a pier or wharf with a single-engine boat that has a right-hand propeller. When the engine is reversed, the propeller will walk the stern toward rather than away from the pier.
Backing Down
If the boat is lying dead in the water with no headway, rudder centered, and the propeller turning in reverse, we again have the strong tendency of the stern to go to port as the discharge current strikes the starboard side of the hull. In each case where the discharge current of the reversing propeller is a factor, the strong current on the starboard side is directed generally toward the boat’s bow, but upward and inward in a spiral movement. The descending blade on the port side, on the other hand, tends to throw its stream downward at such an angle that its lesser force is largely spent below the keel. Therefore, the two forces are never of equal effect.
Until the boat gathers sternway from its backing propeller (right-hand), it would not matter if the rudder were over to port or starboard. The discharge current against the starboard side is still the strong controlling factor, and thus the stern will be moved to port.
Now visualize the boat gathering sternway as the propeller continues to turn in reverse. Here arises one of the seemingly mystifying conditions that baffle many a new helmsman. The novice assumes that in order to back in a straight line the rudder must be centered, just as it must be when going ahead on a straight course. But under certain conditions the boat may even respond to right rudder as the boater reverses by going to port, which is totally unexpected.
If the boater is learning by trial-and-error, it is easy to come to the conclusion that it depends on the boat’s fancy, while rudder position has nothing to do with control. Fortunately, something can be done about it.
Backing with Left Rudder
Consider a boat in reverse with left rudder. Here there are four factors all working together to throw the stern to port. Unequal blade thrust is pushing the stern to port; the discharge current of the propeller is adding its powerful effect; and now we add the steering effect of the wake current acting on the after side of the rudder blade, against which the suction current of the propeller is also working.
Remember this condition well, for it is the answer to why practically every single-screw vessel with right-hand propeller easily backs to port, although it may be obstinate about backing to starboard.
Backing with Rudder Centered
If, while backing to port, you bring the rudder amidships, you eliminate the effects of suction current and steering from the rudder. This leaves unequal blade thrust and the discharge current to continue forcing the stern to port.
Backing with Right Rudder
Assuming further that you have not yet gathered much sternway, you might expect that putting the rudder to starboard should make the boat back to starboard. The forces of unequal blade thrust and discharge current still tend to drive the stern to port, but the suction current of the propeller wants to offset this.
The effect of the discharge current is stronger than the suction, so the overall tendency is still to port. With sternway, the steering effect of the right rudder is to starboard, but as yet you haven’t way enough to make this offset the stronger factors.
Steering while Backing
Opening the throttle to gain more sternway finally has the desired effect; with full right rudder you will find that the steering effect at considerable backing speed is enough (probably) to turn the stern to starboard against all the opposing factors. How well the boat will back to starboard—if at all—depends upon the design of the craft.
All of this means that if the boat will back to starboard with full right rudder, it may also be made to back in a straight line—but not with the rudder centered. There’s no use trying. The boat will need a certain amount of right rudder, depending both on its design and on speed. While most boats always back to port much better than to starboard, a boater can learn to control a particular boat with a reasonable degree of precision.
In some cases, boats may even be steered backward out of crooked slips or channels—not, however, without a lot of backing and filling when there is much wind to complicate the situation. Generally, the trick is to keep the boat under control, making the turns no greater than necessary to keep the boat from swinging too much.
In backing situations, set the rudder first and then add maneuvering power by speeding up the propeller.
Killing Sternway
There is one other situation to be considered, where you want to kill sternway by engaging the propeller to turn ahead. Regardless of the rudder position, unequal blade thrust with the propeller going ahead now tends to throw the stern to starboard, while the suction current is of little or no consequence. In this situation, unequal blade thrust may or may not be offset by the steering effect and the discharge current.
With rudder amidships, there is no steering effect and the discharge current does not enter into calculations. Therefore the stern will go to starboard. Now if you turn the rudder to port, the discharge current of the propeller strikes the rudder and pushes the stern to starboard—even though the normal steering effect of left rudder with sternway would be to send the stern to port. The powerful discharge current from the propeller going ahead is the determining factor.
If the rudder is turned to starboard with sternway, the steering effect works with the unequal blade thrust, tending to move the stern to starboard, but the discharge current strikes the starboard side of the rudder and acts to kick the stern to port. If you apply enough power that the force of discharge current outweighs the other factors, the stern will indeed go to port.
Propeller Action Governs
From the above analysis it is clear that in a single-screw inboard boat you must be constantly aware of what the propeller is doing in order to know how best to use the rudder. What the propeller is doing is even more important than whether the boat has headway or sternway.
It’s Different with Left-Hand Propellers
A significant minority of single-screw powerboats, typically displacement types, and auxiliary-powered sailboats have left-hand propellers. Many commercial boats also have left-hand propellers, as this makes it easier for them to execute a starboard-side approach and departure from a pier or wharf.
If your boat is equipped with a left-hand propeller, you can generally reverse “port” and “starboard” in the foregoing discussions. But to be absolutely sure, make tests for all possible situations.
STEP-BY-STEP DOCKING WITH A SINGLE-SCREW BOAT
With a right-hand propeller, back to port in order to line up with your slip. How fast you can turn your boat determines where to stop and when you should begin backing. A high freeboard and flybridge may react to a crosswind, so choose your moment so as to avoid sudden gusts.
Propeller action will help most single-screw boats turn to port when backing. With the helm hard to port, the boat should begin a turn to line up with the slip.
Usually a boat will need some help kicking its stern farther to port to align itself with the slip. Going ahead with a short burst of power, with helm over to starboard, will accomplish this. Some right rudder will probably be needed to make the boat back in a straight line into the slip, but remember that the torque of the propeller to port (in reverse) often has more influence than the position of the rudder. If a short burst of power is needed, position the rudder first, then apply power.
1 Shift into reverse to stop the boat, then put the helm over hard to port to start the turn into the slip. A slight increase in power will cause the boat to turn a bit quicker.
2 Shift into forward as you enter, put the helm over to starboard and open the throttle for a short burst of power. This kicks the stern to port, aligning the boat with the slip.
3 Shift into reverse and keep the helm to starboard in order to overcome the propeller walk to port and back straight into the slip.
4 When fully in the slip, put the gear in forward briefly to stop sternway. Keep the helm to starboard in order to kick the stern closer to the dock—helm to port if it is too close.
MANEUVERING IN TIGHT QUARTERS
Since most marinas and anchorages are congested places, handling a boat in these confined spaces can be a real test of your skills. In fact, in some harbors, leaving and returning to your berth can be the most harrowing part of a cruise. Most of the basic maneuvers that you will need to get underway from and return to your slip are covered below.
Getting Underway
As skipper, you are responsible for the safe operation of your boat. Before you leave the berth, be sure that all your getting-underway procedures are completed. Make sure that all electrical cords and hoses are disconnected before taking off last-minute dock lines. Avoid spending too much time at the pier warming up the engine; long periods of idling are not good for the engine or transmission, which will warm up faster operating under a light load.
Getting Clear of Your Berth
When the boat is lying alongside a pier or another craft, and the skipper wants to pull away, the wheel should never be put hard over until the stern is clear.
To set the rudder to starboard while lying portside to a pier or wharf, for example, and then attempt to pull away by going ahead (refer to Figure 6-15) only tends to throw the port quarter against the piles and pin it there, possibly slamming into one pile after another and damaging the boat.
Checking Headway
Stopping a boat’s headway will require reversing the propeller. Experiment with stopping the boat from different speeds. This will give you an idea about the propeller’s ability to check the boat’s headway. Consider the following:
• Generally, a larger diameter propeller, acting on a large volume of water, will exert a greater effect. Small propellers, especially those on outboards, may do a lot of churning before they can overcome the boat’s momentum.
• You can stop a fast boat in a short distance by cutting the throttles. Then, as the boat comes off of plane, shift into reverse and apply power.
• When practicing these maneuvers, take the following precaution: When you need to go from forward to reverse or vice versa, slow the engine down before going through neutral. Also warn crewmembers and passengers of your intentions so that they will not be unexpectedly thrown off balance, possibly being injured. Never make a practice of shifting from full ahead into full astern—you will tear up the gears.
• Always remember to approach piers as well as other craft at a very slow speed. Failure of the transmission, or an unexpected stopping of the engine, can result in embarrassment, damage, or both.
Turning in Close Quarters
Although turning a boat in a narrow channel or other confined waterway not much wider than the boat itself may seem impossible to the novice, it is really no more difficult than turning a car around on a narrow road.
Suppose, for example, that you have reached the head of a dead-end canal and must turn around (see the sequential illustrations in Figure 6-18). Assuming you have a single-screw boat with a right-hand propeller, steer to the left side of the channel and make all forward maneuvers to starboard and backing maneuvers to port, to take advantage of the boat’s natural tendencies. Now, running at slow speed, put the rudder hard over to starboard and, as the boat begins to turn, check headway by reversing. Leave the wheel hard over to starboard (right rudder). Very little is gained by applying right rudder while going ahead and left rudder while going astern, since the boat will make little way through the water. As the reversing propeller stops the boat, open the throttle for an instant; the stern will be kicked farther to port. Then put the gear in forward and open the throttle for a short burst of power, to check any sternway and keep the stern swinging to port. As soon as the boat gathers headway, shift into reverse and back down to kick the stern to port; then shift into forward again.
Figure 6-18 Turning in close quarters with a single right-hand propeller: In Step A, at 1, the boat starts to turn at the left side of the channel; make allowance for the stern to swing to port. Headway is checked at 2 by reversing the propeller, with the rudder kept to starboard throughout this series of maneuvers. Unequal blade thrust and discharge current force the stern to port as the boat backs from 2 to 3 in Step B. Going ahead again with a short burst of engine power, Step C, the stern is kicked around more at 4 before the boat has a chance to gain headway. Reversing once more in Step D, headway is checked at 4, and the boat backs to 5. (This forward and backing maneuver can be repeated as necessary.) Finally, in Step E, the boat goes ahead from 5 to 6, completing the change of direction.
Most single-screw inboard boats can be maneuvered in very tight quarters by using this technique. Unequal propeller thrust in combination with rudder action turns the boat. Remember, however, that this applies only for a right-hand propeller; reverse the technique for a left-hand propeller.
Backing to Port from a Slip
When leaving a slip, an experienced skipper will back a single-screw boat with a right-hand propeller to port. Suppose the boat is lying in a slip and you intend to back out into the channel. With left rudder, it will likely turn fast enough as it gathers sternway, aligning with the channel in one maneuver.
Before putting the boat in reverse, pull the boat to the port side of the slip, ensuring as much clearance as possible on the starboard side. Although some room is necessary on the port side because the stern immediately starts to move to port, more room is required on the starboard side because the bow will swing this way as the boat backs.
The starboard bow and port stern are the places to watch in executing this maneuver. If the boat turns sharper than expected, the starboard bow is in danger of touching the adjacent pier (see Figure 6-19) or a boat in the adjacent slip. This could be corrected by going ahead with the propeller a few revolutions while backing out of the slip. Once the bow is clear of the slip, right rudder followed by a short burst of power in forward will help kick the stern over to port if it is not turning fast enough while making sternway.
Figure 6-19 To back out of a slip, a boat should be able to make a short turn to port from 1 to 3 when reversing with left rudder. However, if the bow swings too wide, it may hit at X or Y.
Backing Around to Starboard
In a different scenario, suppose you want to back out of the same situation outlined above or from a slip into a narrow canal that would require a sharp turn to starboard; see Figure 6-20.
Reversing with full right rudder, you will not be able to turn short enough to steer around the 90° angle before you would come up on the opposite canal bank. Most likely, you will back to a position somewhere in the middle of the canal with the stern slightly to starboard. Now, by going ahead with left rudder, the stern is kicked farther over to starboard.
Reversing once more, with full right rudder, the boat backs to starboard and, just as it begins to make sternway, you go ahead once more with left rudder. This checks the sternway and kicks the stern to starboard in alignment with the channel.
Figure 6-20 To back around to starboard where space is limited, the boat starts at 1 with right rudder and backs to 2, as it cannot turn sharply to starboard. At 2, the rudder is turned to port, and the stern is kicked to starboard at position 3 with a brief burst of engine power. From 3, the boat is backed to 4 with full right rudder. Here the rudder is put over to port again, and the boat moves forward to 5. Backing down from 5, it will need a certain amount of right rudder to maintain a straight course.
Backing into a Berth Between Piles
Many marinas and yacht clubs provide slips in which boats are berthed at right angles to a pier or wharf and made fast to piles. Normally, a short secondary pier, often called a FINGER PIER or CATWALK, extends out between each pair of slips. In this situation, it is much easier to board the boat if it is moored with the stern toward the main pier or wharf. This arrangement makes for an easy departure, but requires backing into the slip upon return.
There are many variables that come into play as you back into a slip. Wind, current, and the location of other boats are just a few. At times, some of these factors may be so disconcerting that you may decide not to back into the slip, but instead to dock bow first until conditions improve. A wise man who said “Discretion is the better part of valor” must have been thinking of this situation.
Now let’s consider a typical situation: You have spent a nice day on the water and are returning to your slip—one of hundreds located on a pier in a large marina; you want to back in. As you turn into the channel, the slip is to port and you are moving with a light wind and current astern. The channel is only a couple of boat lengths wide, so there is not much room for maneuvering. In this situation, the port side of the channel should be favored to allow for wind and current. Begin your turn before the slip, in order to position the boat upwind and/or up-current of it.
Depending on how quickly the boat can be turned, put the helm over to starboard well before you reach the slip. Because the channel is narrow, the boat will not be able to turn more than 90°, almost into the wind, in a single maneuver; see Figure 6-21. As the bow approaches the other side of the channel, shift into reverse and open the throttle to stop headway and kick the stern to port. As soon as the boat gathers sternway, reduce throttle, then shift to forward and open the throttle again to kick the stern farther to port; position the boat at about a 45° angle to the slip.
Figure 6-21 Backing into a slip between piles in a basin, if space allows, make a turn ahead under power to maneuver the bow partly into the wind before backing down. Note that the right rudder in positions 7 and 8 keeps the stern from swinging to port.
The turn should be timed so that the final position of the boat is slightly upwind from the slip, with the wind and current off the starboard bow. If you are not upwind of the slip, complete the turn and run upwind until you are. If you are too far upwind, wait for the current to push you down closer to the slip.
Begin backing with right rudder. As soon as you start backing, the current and wind will push the bow to port so that, by the time the stern is entering the slip, the boat will be nearly in line with the slip. Remember, when backing a boat with a right-hand propeller, use left rudder in combination with a short burst of forward power to move the stern to starboard. Left rudder with propeller reversing should move the stern to port.
Getting Clear of a Pile
In maneuvering around slips and piles, you may be caught in a position where the wind and/or current hold the boat against the pile, preventing any maneuver. The solution is to rig a forward spring line from the pile to an aft cleat, preferably on the side of the boat away from the pile; see Figure 6-22. Then, by reversing with left rudder, pivot the boat around the pile and bring the bow into the wind or against the current or the wind, whichever predominates. You can then clear the pile by going ahead with power as the spring is cast off.
Figure 6-22 If pinned against a piling, use a forward spring line from a stern cleat (and apply a bit of reverse power) to swing the boat into the wind or current.
In getting clear from this point, you may need a little left rudder to keep the stern clear of the pile, but don’t use enough to throw the stern so far over that the starboard quarter is in danger of hitting an adjacent pile.
Plan Maneuvers in Advance
Obviously the number of possible situations—considering the differences in boats and the strength, direction, and effect of wind and current—is almost infinite. Usually, however, applying one of the principles above, modified as needed, will permit a seamanlike handling of the problem.
Even though you know the principles, however, it pays to think ahead about the steps you will take. With a clear plan of action, you can take each step slowly and easily and have time to keep the boat under perfect control. To avoid confusion, tell your crew the steps you plan to follow, the actions that each crewmember will have to take, and the orders you will give when these actions are required. Even on occasions that call for swift and decisive action, you’ll need calm, ordered judgment.
If your planned maneuver is not working, don’t hesitate to stop, reevaluate the situation, and develop a new plan. For example, if your plan for a clean approach to a pier or wharf has been upset by a freak current you couldn’t calculate or by a passing boat’s wake, back off and square away for another attempt. That in itself is good seamanship, regardless of how some may judge your apparent “miss” on the first try. Common sense, if you act with deliberation, will enable you to work out a solution for any combination of conditions.
When you are at the helm and you have people on deck handling lines, give orders to each so that all action is under your control, instead of having two or three acting independently at cross-purposes. This is especially imperative when your crew is not familiar with boats or with your method of boat handling.
DOCK LINES & THEIR USES
Dock lines (also called mooring lines) play an important part in the handling of vessels at a pier. Obviously, as boat size increases, more and heavier lines are needed. A small, light outboard craft requires fewer lines for secure docking than does a heavy 50-foot trawler. But all skippers should know and understand how lines are used so that they can decide which lines are appropriate in any circumstance.
In addition to securing a boat in its berth, the proper use of lines can aid maneuvering close to piers and wharves.
Figure 6-23 The various possible dock lines for a vessel include the eight shown here. A small-craft skipper will never need to use all of them at the same time. The stern line, 8 in the diagram, is best run to the offshore side of the boat to gain better control while holding the stern closer to the wharf or pier.
Dock-Line Terminology
Although most skippers speak quite loosely of bow and stern lines, it generally matters little as long as the line is made fast forward or aft.
However, there are several lines that can be secured to the bow or stern and, depending on their direction and use, these are given other names. (Note that “forward” and “after” relate to the direction in which a line runs from the vessel, not to where it is made fast on board.) Figure 6-23 illustrates eight possible lines; Figure 6-24 shows just those lines that might be used in a typical small-craft docking situation.
Figure 6-24 As shown in this typical small-craft docking, crossing spring lines provides greater length for each. This is particularly desirable where there is a significant tidal range.
Bow & Stern Lines
According to correct nautical terminology, there is only one BOW LINE. This is made fast to a forward cleat and run forward along the pier or wharf to prevent the boat from moving astern. The STERN LINE leads from an after cleat to a pile or cleat on the pier astern of the boat; this line checks the boat from going ahead. When securing a small craft, these lines can be sufficient to keep the boat next to the dock. If given the proper slack, they can allow for considerable rise and fall of the tide.
Breast Lines
BREAST LINES are lines secured to the bow and stern that lead athwartships nearly at right angles to the vessel and to the pier or wharf. They are used on larger vessels to keep the craft from moving away from the pier or to pull it in for boarding. Large craft may use bow or quarter breasts, depending on where they are secured. Breast lines are more important on large vessels than on small ones.
Additional Cleats
Smaller recreational boats frequently will have only one bitt or cleat forward and one or two aft, for securing dock lines. Additional cleats along the sides, properly through-bolted, give better flexibility in the use of dock lines.
Spring Lines
Although only two SPRING LINES are usually used, there may be as many as four: the forward bow spring, the after bow spring, the forward quarter spring, and the after quarter spring. Bow springs are made fast at the bow or to a forward side cleat; quarter springs run from the stern or an after side cleat. Forward springs lead forward from the vessel to the pier or wharf, and control movement sternward. After springs lead aft from the vessel, and check movement ahead.
Spring lines are used to prevent movement in a berth, ahead or astern. They work with the bow and stern lines to keep a boat in position when there is a significant rise and fall of tide. This is particularly desirable where boat movement forward and aft must be minimized so that fenders are kept in place against piles, or where the gap between adjacent vessels is small.
BOW THRUSTERS
Many medium-size and larger craft are now equipped with a BOW THRUSTER. This is a small propeller (or two of them) mounted in a tunnel that crosses from one side of the hull to the other just below the waterline and very near the bow. Bow thrusters on boats are smaller versions of devices found on most large ships. They are powered by either an electric or a hydraulic motor. Electrically powered thruster installations are simpler and less expensive, but cannot be operated continuously. Hydraulic thrusters may be self-contained or powered from a hydraulic power system installed for other machinery. Smaller units have a single propeller; larger units have two counter-rotating propellers or two propellers with opposite blade angles turning in the same direction; there does not seem to be any significant advantage or disadvantage in these variations in design. Thrusters are rated in motor horsepower or pounds of thrust developed.
Bow thrusters are reversible, sending a jet of water to either side. Controls usually consist of a small joystick at each helm position, together with an ON-OFF switch. Motors are operated in either direction at a fixed speed. To keep size and weight at a minimum, electrical motors are small and must be operated intermittently to prevent heat buildup and damage. On sophisticated installations, a thruster may be retractable rather than in a tunnel, being lowered for use and retracted within the hull when not needed.
Bow thrusters are of the greatest assistance to single-screw vessels, but are also quite useful on twin-screw craft. They are primarily used in docking and undocking, situations where they can be of significant help. They may also assist in making sharp turns in rivers and channels. The fact that they are used only infrequently does not detract from their overall value—when you need one, it’s good to have it!
Seldom seen, but quite practical, are STERN THRUSTERS. These have the motor and small propeller of a bow thruster, but not the tunnel. They are usually mounted beneath a swim platform on single-screw craft such as trawlers. The purpose is the same as for bow thrusters, assistance in docking or other close-quarters maneuvers.
Sizing the Line to the Boat
On most recreational boats, dock lines are made from nylon, either of twisted rope or braided core and cover. Nylon is the preferred material because it stretches, thereby absorbing shock loads; it is chafe-resistant for long life; and it is easy on the hands.
A line’s size varies with the boat. Typically, a 20-to 40-foot craft will use 1/2-inch-diameter nylon lines, with larger yachts using 5/8- or 3/4-inch lines. Smaller boats can use 3/8-inch nylon. Dock lines should be strong enough to hold the boat and have enough bulk to resist chafe, while not being so heavy as to lose their shock-absorbing characteristics. A light boat pulling against a 5/8-inch line will come up hard against the line because the weight of the boat is not enough to cause the line to begin to stretch. On the other hand, a light 3/8-inch line holding a heavy boat will be very springy and probably only strong enough for favorable conditions. Moreover, 3/8-inch lines provide no margin for wear and chafe when under heavy strain.
Making a Boat Fast to a Pier
Although many people will speak of “tying up” a boat in a slip or to a pier, this is not correct nautical terminology. A vessel of any size is “made fast” to the shore.
As described above (and illustrated in Figure 6-23) there are at least eight dock lines that might be used to secure a boat; they are not all used at the same time. Most average-sized boats can be made fast to a pier or wharf using four lines. The after bow spring is crossed with the forward quarter spring and secured to separate pier cleats or piles; refer to Figure 6-24. This arrangement provides longer springs, which can be drawn up rather snugly and still allow for a rise and fall of tide. If only one pile or cleat is available on shore, position your boat so that this point is opposite amidships; then run both springs to it. The lines will be shorter, but still effective.
The bow and stern lines should make roughly a 45° angle with the pier. The stern line can be secured to the near-shore quarter cleat, but will work better if run to the offshore quarter cleat. The longer line will allow the boat to rise and fall with the tide and better keep the boat in close to the pier.
If there is an offshore wind blowing, you may want to rig a slack breast line to the near-shore quarter cleat in order to pull the boat into the pier against the wind for easy boarding. However, you must always remember to loosen the line as the tide rises or falls, and to allow plenty of slack during the night or when the boat is untended.
Dock lines frequently have an eye splice in one end but not the other. You must decide whether to use the end with a loop on shore or on the boat. If you are going to be on board, it is better to retain the plain end on board. This means that you can make adjustments without getting off the boat. If there will be no one on the boat, use the end with the eye on board; the plain end ashore will allow adjustment without the necessity of boarding. Figure 6-25 illustrates the most secure method of making the eye end of a line fast to a cleat.
Figure 6-25 Most cleats on boats consist of a crossbar elevated from the deck by two legs (see Figure 1-28). The most secure method of attaching a line to such a cleat is by passing the eye through the gap between the legs and then back over each end of the crossbar.
Heaving Lines & Monkey’s Fists
A part of good seamanship is knowing when a certain procedure is applicable to the size of vessel that you are on, as when getting dock lines from your boat to the shore or another craft. The lines of a big ship are heavy hawsers, hard to handle and impossible to heave. The deck crew of such a vessel makes use of HEAVING LINES, light lines weighted at one end with a MONKEY’S FIST (an intricate woven knot enclosing a weight) for greater accuracy in heaving. This light line is attached to the hawser near the eye splice—but not in the loop where it might get jammed when a strain is placed on the hawser—and the line is heaved over from the ship to the pier or wharf as soon as possible as a MESSENGER. The heavier line, or hawser, is then pulled over and made fast.
Small-Craft Practices On recreational boats, heaving lines is more of a technique to be learned and then filed away for possible later emergency use. Normally, your crew can hand a line to someone ashore, or throw it a short distance.
To throw a line to someone on shore or another boat, coil the line in your left hand (if you are right-handed), making clockwise loops. Coil the line smoothly, avoiding figure-eights, then transfer about half the loops to your throwing (right) hand and hurl them with a strong swinging motion while letting the loops play out freely from your other hand. Hold tightly to the bitter end or, better yet, secure it to a cleat. Figure 6-26 shows a line being prepared by a right-handed person. If necessary, a weight can be added to carry a line farther, but this is seldom length. Otherwise, the short one carries the full load until it breaks, leaving the single longer line to then carry the same full load.
MAKING FAST
When mooring your boat, fasten the lines securely at both ends. Often you will loop the eye splice of the dock line around a pile. If your boat has much freeboard, or the tide is high, the mooring line will lead down sharply from deck to pier. To prevent it from being pulled up off the pile, loop the eye splice around the pile twice. If the eye in your mooring line is too small to go around the pile twice, or even fit over the pile once, pull the line through the spliced eye to make a new loop.
If yours is to be the second line on a pile or cleat, it is both prudent and courteous to dip your line through the first loop. The other skipper may not know the trick of getting his line clear without removing yours. To drop a line over a pile that already holds another boat’s line, run the eye of your line up through the first eye from below, then loop it over the pile; see the illustration at right. This will allow either line to be removed without disturbing the other.
If you find that another skipper has dropped the eye in his line over yours on a pile or cleat, simply reverse the process. Pull the other line to get a little slack, and then slip your eye up through its loop and over the top of the pile. Your line then can be dropped through the eye of the other and pulled clear.
When leaving a pier or maneuvering against spring or other dock lines, it is convenient to be able to release the line from the pile or cleat—from on board the boat—as soon as you get away from the pier. By looping a long line around the pile or cleat and having both ends on board, you can easily release it. Slip one end around the pile or cleat, then pull it back on board. Be sure to release the end of the line without the eye splice, so it will run freely around the pile or cleat without hanging up at the splice.
If the lead is high from the pier or wharf to the deck, take an extra turn around the pile with the eye splice to prevent the line from slipping up off the top of the pile.
If you need to place your line on a pile that already has one on it, pass the loop of your line up through the loop of the first line and then over the top on the pile.
If Lines Are Doubled
If two lines are used with the idea of getting double the strength of one, they must be of equal needed. If you need to pass over a heavy towline, however, break out your heaving line and use it to good advantage.
Figure 6-26 A properly coiled dock line can be thrown a significant distance if you start with half the coil in each hand.
Allowing for Tidal Range
Boaters on freshwater streams and lakes have no tides to worry about when they make fast to a pier. But in tidal waters, failure to consider the tides can part lines, and may even sink the boat.
Long spring lines provide the most effective method for leaving a boat free to rise and fall. They also keep the boat from going ahead or astern, moving off fenders, or twisting in such a way as to get caught on pier projections. The longer a spring, bow, or stern line can be, the greater the tidal range it can accommodate with a minimum of slack. Long lines also allow each line to be adjusted so they don’t all come taut or excessively slack simultaneously as the tide falls or rises; see Figure 6-27.
Figure 6-27 This illustration shows how long spring lines are used with considerable changes in tidal levels. If the water drops 11 feet from E to D, a 32-foot after bow spring line (A to F at high water, A to B at low water) would cause the boat to move astern only the distance from F to B, roughly 2 feet.
Adjust the dock lines to come up almost taut at either of the extreme tidal ranges; this adjustment may take some experimentation. Observe the boat at both high and low tide, and adjust the lines so they are snug, but not tight, at these stages.
If you keep your boat in a slip, it is important to check the lines at times of extreme high and low tides. Make sure the lines are not so slack that the boat can move against a pile or finger pier.
When berthing in a narrow slip with a large tidal range, it may be impossible to keep the boat from coming against a pile or pier. Careful placement of fenders, on the boat or secured to the pier or piling, may be the only way to protect your boat; be sure to use spring lines.
Maneuvering Against Dock Lines
Depending on current and wind, getting in and out of your slip or away from a pier can at times be challenging. Spring lines are the most useful dock lines, as they can be used to assist maneuvering.
Going Ahead on an After Bow Spring
If it is possible to secure an after spring close to the boat’s pivot point (about one-third the way aft from the bow) or amidships, the boat can then be worked into a pier by running ahead slowly with the rudder turned away from the pier; see Figure 6-28. Since the stern is free to swing as the discharge current acts on the rudder, the boat will move toward—and come in closer to—the pier. This technique is especially useful when maneuvering short-handed, bringing the boat against the pier by simply passing a single line ashore. It is also helpful when maneuvering a large boat against a stiff offshore wind, where hauling in on bow and stern lines would require great effort. This is typically more theoretical than practical on many small boats, which have only the bow and stern (or quarter) cleats for securing spring lines to, while the pivot point is well aft of the bow. If it is at all possible, install a cleat on each side of your boat slightly forward of amidships.
Figure 6-28 By going ahead on an after bow spring line, as shown at A, a boat’s bow is pulled into the pier, but the stern swings away from shore. If the rudder is turned away from the pier, as at B, the stern will swing in as power is applied. This maneuver works best if there is a cleat back from the bow, nearer the pivot point of the boat.
Reversing on a Spring or Bow Line
The stern is swung sharply toward the pier by the action of the forward quarter spring when reversing; see Figure 6-29.
Figure 6-29 When backing on a forward quarter spring, the stern swings in but the bow swings out away from the pier.
Since stern movement is restricted, there is much less control. The bow is free to swing away from the pier with the wind or current. If you back on a forward bow spring or on a bow line, the stern is not as restricted, and the line has less effect on turning the boat; see Figure 6-30. Unless there is a strong offshore wind or current, the boat will probably back parallel to the pier.
Figure 6-30 By reversing on a bow line, a boat can be sprung in nearly parallel to a pier or wharf face.
LANDING WITH CONTROL
Whenever you approach a pier or wharf, your close-quarters boat-handling skills will be tested. Although this maneuver is not difficult, a challenging situation can arise from a combination of wind, current, and adjacent congestion. Your knowledge of turning a boat in limited space will stand you in good stead when you tackle the problem of bringing your boat in neatly to a pier, wharf, or float.
As a matter of proper terminology, here is a reminder that you should not refer to a “dock” when you actually mean a “pier” or “wharf.” A pier projects out from the shoreline, usually but not always at a right angle. A wharf (sometimes called a quay, pronounced “key”) is a structure generally parallel to and not far from the shore. Technically, a dock is the adjacent water area that can be occupied by a vessel. In boating, however, the term is often used loosely to mean the structure itself. The space occupied by a vessel, or available for its use, is its berth.
The action of coming alongside the structure, whatever it is, is referred to as DOCKING (sometimes mooring, although it is less confusing if this term is limited to picking up the pennant of a floating mooring buoy). Departing is “undocking,” a term more often used with ships than boats.
This section covers the basic guidelines to consider when approaching a pier or docking a boat in the types of conditions you will likely encounter.
Approach with Caution
Since boats do not have brakes and must rely on reversing the propeller thrust to stop, it is prudent to maneuver at slow speeds in congested areas. Monitor your boat’s wake as you make your way to your berth; it can affect your boat as well as other craft nearby.
Don’t come in at high speed with a grand flourish. Depending on conditions, throttle down gradually to keep the boat under control. The goal is to proceed through the harbor or marina slowly, but with enough way on to maintain control. When you consider that you have enough way on to reach the dock, shift into neutral; use reverse power as and when necessary to check headway as you reach your desired location.
If your speed has been properly estimated, you will be several boat lengths from the pier when you shift into neutral. Approaching a pier too fast will require you to shift into neutral far from your berth. Even though the boat is moving through the water, the propeller is not turning and, consequently, there is no propeller discharge current acting on the rudder. Keep in mind that most boats have better slow-speed maneuverability if the propeller is turning: A slow approach allows you to keep the boat in forward until you are almost alongside the pier.
This is a good time to exercise judgment—keeping on the way needed for maneuverability, yet using no more speed than required. If you have been running at any speed, hold off briefly and let your own wake pass by your boat. Have the dock lines ready to use fore and aft. Also have fenders ready so that they can be put in place as soon as the boat is secured, keeping it from chafing against piles or pier edges. Lead all docking lines outboard of stanchions and shrouds, so that they will be clear when taken ashore.
The biggest mistake novice deckhands make is to secure a dock line before the boat has lost all headway. If you have a couple of hands on board, assign one to the bow and one to the stern, with instructions not to make fast until headway is checked. Use reverse to stop the boat, cautioning your crew that securing the bow or stern lines while the boat is still moving can cause the bow or stern to come crashing into the pier. An after bow spring line is the only dock line that should be used to stop the boat. If you are maneuvering into a tight berth or against strong current or wind, this line will likely be the first one secured.
MAKING USE OF FENDERS
Fenders (they are not to be called “bumpers”) are relatively soft objects of rubberlike plastic often filled with air under low pressure. They are used between boats and piles, pier sides, and seawalls to protect topsides from scarring and to cushion any shock of the boat striking the fixed object. Some fenders can be inflated to different pressures with a hand- or power-driven pump. Most fenders are circular or square in cross section and of varying length.
Most fenders have eyes molded in each end for attaching a short length of line that is used to suspend them along the side of a boat. Some models have a hole through their center through which a piece of line is run and knotted on each side of the fender.
Good-quality fenders are not inexpensive, but they are well worth the investment. Half a dozen substantial fenders are not too many for the average cruiser to carry.
Fenderboards
Vertically suspended fenders give protection against the face of a solid pier or wharf as the boat moves fore and aft. If the boat lies against vertical piles, however, vertical fenders will not stay in place during the boat’s forward and aftward movement.
The solution to protecting the hull in many situations is with fenderboards—short lengths (approximately 4 to 6 feet) of heavy boards (2 inches by 6 inches is common), sometimes faced on one side with metal rubstrips or rubber cushions. Holes are drilled, and lines attached, allowing the board to be hung horizontally, backed by two fenders hung vertically.
The horizontal fenderboard rests against the pile bridging the two fenders. The boat can then move back and forth the length of the fenderboard and still be protected from chafing against the pile.
Fenderboards also give excellent cushioning between two or more craft rafted together. One boat should put out the usual two fenders behind a fenderboard; the other puts over only its own two fenders. A second fenderboard should not be used, since one board could tangle with the other.
Calm Conditions
Without wind or current to complicate landing, a skipper operating a boat with a single right-hand propeller should make a port-side approach to the pier. Time your approach speed so you will be several boat lengths from the pier when you shift into neutral. Since a reversing right-hand propeller will move the stern to port, approach the pier at a 10- to 20-degree angle; see Figure 6-31. When alongside, shift into reverse to stop headway. Depending on your speed, a short burst of throttle may be necessary to stop the boat and to kick the stern to port, with the boat alongside and parallel to the pier.
Figure 6-31 With a right-hand propeller, approach a pier or wharf for a landing, as at 1, at an angle of 10° to 20°. Discharge current of the reversing propeller will set the stern to port, as at position 2, even though the rudder is centered.
Although a port-side approach is preferable, you can, with care, make a good landing with the pier on the starboard side (remember, we are on board a single-screw boat with a right-hand propeller). Approach the pier slowly at a much shallower angle, as nearly parallel as possible to the pier; see Figure 6-32. Just before you have to reverse to check headway, turn the rudder to full left, swinging the stern in toward the pier. If it does not respond, give the propeller a brief spurt of ahead engine power while the rudder is full left, in order to kick the stern to starboard. Then reverse to check your headway.
Figure 6-32 When it is necessary to make a landing starboard-side to the pier in a craft with a right-hand propeller, approach slowly, as at 1, as nearly parallel as possible to the pier or wharf face. The rudder is turned to full left at 2, and the stern is swung to starboard with a short burst of engine power. Check the forward motion at position 3.
You can also bring the boat in parallel to the pier with an after bow spring line. Secure this line to a pile or cleat ashore, then put the gear in forward with the rudder full left. The spring line prevents forward movement while the stern moves toward the pier.
Wind or Current Parallel to Berth
Because water is many times denser than air, in most cases current should be given primary consideration when planning an approach to a pier or wharf. If the wharf happens to be on the shore of a river or the bank of a tidal stream, the current will flow generally parallel to it. In this case, the direction of the current should determine how you approach. Heading into the current will enable you to keep the propeller turning over slowly and water moving past the rudder—right up to the moment of reaching the wharf—if the current is strong enough.
If you were to approach the pier from the opposite direction, moving with a half-knot current, you would not only have to stop the boat dead in water. You would also have to begin making half-knot sternway before your relative movement past the pier would stop.
The wind also must be reckoned with. Since propellers are not as efficient when reversing as when going forward, attempting to stop your boat in a strong following wind takes extra time. During this time, the rudder will be in the propeller’s suction current, so it will be of little use in steering the boat. Stopping a boat going upwind is much easier, and, if the wind is strong enough, the propeller can be kept turning ahead even as the boat comes dead in the water.
When approaching a pier with a current running or strong wind blowing parallel to it, stop your boat in the channel. Assess the directions and relative strengths of the wind and current (at times they may be opposing) before deciding on which approach is best:
• If the wind or current is at your back, then pass downwind or downstream of the pier, turn around and proceed toward the dock upstream. In starting a turn such as this, even at some distance from the berth, throttle down well before the wharf comes abeam. Otherwise your wake may carry along and have you wallowing in it just when you are coming alongside.
• In coming up against wind or current, you can use that force to check your headway, instead of reverse. In the case of a strong current, your boat should respond to the helm when its relative movement to the pier has stopped, because there will still be a flow of water past the boat and its rudder.
Landing Downwind or with Current
If you can, avoid any landing in which wind or current is setting you down toward your berth. Here, you are totally dependent on your reverse gear for stopping the boat. An error in judgment or an engine or gear failure would put you in an embarrassing, if not dangerous, situation.
Sometimes, however, space will not permit you to turn before docking. Suppose, for example, you are coming into a canal lock with a strong wind astern. Proceed in as slowly as possible while retaining control. With a single-screw, right-hand-propeller boat, if possible, choose the port side of the lock, so that your stern will swing in against the lock face when you reverse. Once the boat’s headway has been checked, get a line out from the stern or port quarter; the boat can lie temporarily on this line alone. If you get a bow line secured ashore first and miss making the stern line fast, you risk being turned end-for-end by the wind or current.
Handling the Lines
If you have a couple of hands aboard, assign one to the bow and one to the stern to handle lines, with instructions not to make fast until headway is checked. The seriousness of checking the boat’s way by means of a snubbed bow line instead of reversing the propeller is only too obvious. If single-handed, you will have to work smartly, with a stern line fast to the after cleat—coiled and ready to carry ashore—and a bow line run in advance along the deck back to the cockpit. All docking lines, of course, should be led outboard of stanchions and shrouds, to be clear when taken ashore.
The problem is similar if you are making your landing with a following current. In either case, be ready with reverse gear on the approach, using it as strongly as necessary to hold the boat against its momentum and the push of wind or current. The propeller ordinarily should be turning over slowly in reverse for the last boat length or two of headway, the throttle being opened gradually and as needed to kill all headway at the right instant.
Landing on the Leeward Side of a Pier
Since the wind can blow from any direction, it’s not uncommon to find yourself approaching a pier with the wind blowing at right angles to the pier. If you have a choice as to which side of the pier you land, choose the leeward side. If the wind is strong, the windward side can be uncomfortable and your boat may pound against the piles. The rougher it is, the more important it becomes to dock on the leeward side. The wind will then hold the boat clear of the pier instead of pushing the craft against it.
Unless there is current to consider, make the leeward approach so the port side will rest against the pier. Depending on wind strength, you may have to point the bow into the wind a bit more than usual to keep it from falling away during your approach. Your biggest problem will be getting the stern to come into the pier against the wind.
Since you are going upwind, you can approach the pier a bit faster then normal, and then reverse a bit harder, kicking the stern toward the dock. You may need to put the rudder hard right and go forward for a short burst to help get the stern in.
Have the crew take or pass the bow line—or after bow spring line—ashore first. Then secure the stern line. If the stern begins to drift away from the pier before you can secure the stern line, run ahead on the bow line slowly with the rudder hard right. It will act as an after spring to help bring the stern into the pier.
Be careful that neither the bow nor topside is damaged by the pier during this operation; have your fenders ready.
If you have a large, heavy boat, secure the after spring on a beam cleat first; then secure the stern line.
Close Quarters
Often you will find that the only empty berth in a crowded marina or yacht club lies between two docked boats. There may be little more than a boat length to squeeze into; see Figure 6-34. Here again, the spring line comes into play.
Figure 6-33 Close-quarters boat handling is one of the most important skills that a boater can acquire. The key to success is understanding the fundamentals, plus much practice—an opportunity that is ever-present (often with other skippers watching) in most marinas and yacht clubs.
A port-side approach is preferable. Since boats are on both sides of your desired berth, you will have to approach at a greater angle than if the pier were clear of other vessels. The objective is to place the bow of your craft as close to the pier as possible, without running up on the forward boat. Be sure you leave ample clearance on your port side so that, when you back down to check headway, the stern does not hit the bow of the boat astern of you.
Have your crew stand by, ready to go ashore with the after bow spring line or ready to throw the line ashore to someone on the pier who will make it fast. After the spring line is secured ashore, put the rudder over full right and go ahead slowly. While the propeller discharge current acting on the right rudder pushes the stern into the pier, make certain that the spring line is adjusted so that the boat cannot possibly move forward into the boat ahead. Then, as the boat swings in, the spring line may be slacked off a little bit. Quite often you may find that a fender or two might be necessary at the point of contact.
Figure 6-34 Landing between boats A and B, boat C approaches at a greater than normal angle. At position C2, a spring line is run aft from at or near the bow to the pier or wharf. Going ahead with engine power and right rudder, the boat swings into its berth at position C3.
A Mediterranean Moor
In some areas, especially along the Mediterranean coast in Europe, where docking space is very limited, boats of all types and sizes are docked with their sterns to the shore, without the use of piles and finger piers. An anchor is dropped off shore, and the vessel is slowly backed in, paying out the anchor rode, until it is close enough for persons to get on and off using a short gangplank from the transom to the quay or shore. Have fenders in place along both sides if there are adjacent craft.
Holding with One Spring Line
The use of a spring line works well for temporarily holding a boat on the lee side of a pier or wharf. Assume that you intend to run up along the leeward side of a pier and remain there for a short time while you pick up guests or perhaps put someone ashore. Instead of getting lines out to make fast fore and aft as you would for a longer stay, or expecting the crew to hold the boat against the wind’s pressure, try using just one line as an after bow spring. First come alongside; pass and make fast the line ashore. Then, continuing to use it, go ahead, rudder turned away from shore, with just enough power to hold the boat in against the pier. This is a maneuver that you can accomplish single-handedly without too much difficulty, by having your spring line fast to the forward cleat as you come in, with the end ready to pass ashore for someone on the pier to drop over a pile or cleat.
Doubling a Spring Line
Single-handed, you might prefer to use the spring doubled, with a bight of line around the pile or cleat on shore and both ends of the line made fast to your boat. Then, when you are ready to leave, you can slip the engine into neutral, cast off the one line, and haul the spring back aboard without leaving your boat. This would be helpful when the wind is of some force, the shoreside cleat well back from the pier’s edge, and there is no one on shore to assist. This way there would be no risk of the boat’s being blown off as you step ashore to cast off the line.
In any case, when the line has been cast off, the wind will cause the boat to drift clear of the dock, the bow ordinarily paying off faster than the stern. Whether you go ahead or reverse to get under way will depend on whether there are other structures and boats nearby, and whether your course is to be up- or downwind.
This same maneuver is appropriate if it is current rather than wind that is tending to move your boat away from the pier.
CLEARING A BERTH
Getting safely away from alongside a pier or wharf can be either simple and easy or complex and difficult, depending on wind direction and force, the set and strength of any current, and the proximity of other craft. Take advantage of any help you can get from the wind and current, and make good use of spring lines.
With Wind or Current Ahead
When your boat is facing the wind or current, leaving a berth is not difficult. The biggest problem skippers often create for themselves is to start forward without providing sufficient clearance between the pier and their boat. Remember that, for a boat to turn, the stern must be free to move. To pull away from a port-side pier, the stern must swing to port before the boat will begin to turn to starboard away from the pier. It is not uncommon to see a boat rub its stern against the whole length of a wharf as the skipper turns the wheel more and more to starboard in an effort to pull away; refer to Figure 6-15.
With smaller, lighter craft, all that may be needed to gain the necessary clearance from the pier is for someone ashore to push off the bow. Alternatively, backing on a forward quarter spring will allow the current to turn the bow away from the pier or wharf; use a fender to cushion the port quarter of the hull; see Figure 6-35. On the other hand, a larger boat will find it better to go ahead on an after bow spring, with the rudder turned in toward the pier. The natural action of the propeller plus rudder will swing the stern clear of the pier. You can then back down a short distance to clear the pier before going ahead; remember that as you turn to starboard your stern will swing to port, bringing it back toward the pier. With either procedure, don’t try to cut away too sharply; your stern could come back in enough that your port quarter would strike the pier.
Figure 6-35 One technique that can be used when the wind or current is ahead is to back on a forward quarter spring line with the rudder centered. This will turn the stern in and the bow out. You can then retrieve the spring line and power ahead to clear your berth. Use a fender as shown here.
From a Windward Berth
Clearing a berth where the wind or current is pushing the boat against the pier does not necessarily have to be difficult, except in extreme conditions when it may be impossible to get the boat off the pier without working with the after bow spring.
Since the wind or current is holding the boat against the pier, cast off all dock lines except the after bow spring line. If the boat has only bow and stern lines, cast off the stern line, then transfer the bow line to an amidships position on the pier to convert it into an after spring.
Go ahead easy on the spring with the rudder turned toward the wharf; see Figure 6-36. The bow of the boat will come into the pier, and the stern will move away from the pier. If it does not respond with the rudder hard over, open the throttle to provide the kick necessary to work the stern around.
Figure 6-36 An after bow spring line is often needed to depart from the windward side of a pier or wharf face. The boat goes ahead on the spring from 1 to 2, with the rudder turned toward the shore. Use of a fender may be needed as shown here. At 3, the line is cast off, and the boat backs into the wind or current.
Depending on the nature of the pier and the type of boat, you may need a fender or two at critical spots between pier and boat.
Continue until the boat has turned enough. The stern should be angled far enough from the pier so it will not be blown back against the pier when backing away. Get the spring line and fenders on board, and back the boat away with rudder centered. The stronger the wind or current, the more power is necessary to move the boat against it. If there are other boats moored to the pier near you, back away with considerable power to gain sternway and some steerage as soon as possible.
Continue backing away until well clear; a boat that is dead in the water will make much more leeway than one that is moving.
With Wind or Current Astern
Instead of merely casting off all lines and going ahead, get the maneuverable stern out away from the pier and go astern before going ahead on the course.
Run ahead on the after bow spring. This allows the stern to drift out into the current or be kicked out if necessary by power, going ahead with the rudder turned toward the wharf. If the current or wind is noticeable, often the stern swings out without aid of the engine. When the boat has swung out anywhere from 45 to 60 degrees, the spring is cast off. The boat should be backed off far enough to clear the structure before you go ahead with opposite rudder.
Backing Around
We have already discussed backing out of a slip. But at times it may be necessary to back out of the slip and make an immediate sharp turn to avoid other boats or an adjacent pier. In either case, the forward quarter spring line can be used in much the same way as described for using the after spring; see Figure 6-37.
For example, let’s say your boat is lying in its slip, starboard side to the land. The first step is to make the spring ready from a point near the corner of the slip to the after cleat—either amidships, if there is only one, or the cleat on the starboard quarter, if there are two.
Figure 6-37 A forward quarter spring line can be used to assist a boat in backing out and around the end of a pier. When the spring line becomes taut, the boat reverses with full right rudder. Use a fender as necessary to protect the hull.
With the spring ready—slack but tended—ease off on the bow line, tended by someone on shore. Back the boat slowly with full right rudder. When the boat is about halfway out of the slip, take a strain on the spring to prevent backing farther. This will cause the boat to pivot as the stern is pulled around to starboard by the spring line. Be sure to protect the boat from the pier with a fender.
As you continue to back, the spring will pull the boat up to the pier. At this point, you should slack the spring as the boat comes parallel to the pier so you can back farther. If you plan to secure the boat to the pier, you can use the spring as one of your dock lines, adding others as needed.
This method is especially useful when there is a breeze off the structure that would tend to blow the boat away if maneuvering without lines. No human power is required, and it can be accomplished in a leisurely and seamanlike manner. But, as in any case where the stern is made fast to the shore with the bow free, take special care to keep the boat under control.
If the boat is to get underway after being backed around, no bow line is needed. When the boat has pivoted far enough, with its starboard quarter near the corner of the pier, idle the engine while casting off the shoreward end of the spring and bringing it on board. To get underway from such a position, keep the rudder amidships until the stern of the boat is clear of the pier.
Turning in a Berth
At times you may find it easier to turn your boat around at the pier than to attempt to leave the berth with adverse current conditions—particularly if the area surrounding the pier is congested.
To turn a boat with the starboard side against a pier, current coming from astern, first let all lines go except the after bow spring. Often the effect of the current will then be sufficient to throw the bow in toward the pier and the stern out into the current; see Figure 6-38. If any factor, such as a beam wind, tends to keep the stern pinned against the pier, kick the stern out by going ahead easy with right rudder. Keep a fender handy as a protection for the starboard bow.
Figure 6-38 A boat can be turned end for end using just the current (or wind) and a spring line.
Take steps to prevent the bow from catching on the pier as it swings. A small boat will usually require a fender, but a large craft may have to reverse the engine just enough to keep the bow clear.
As it swings in with the current, the fender should be made ready near the port bow. Also transfer the after bow spring from the starboard side to the port side. If the boat does not come alongside readily, even when helped by going ahead a little on the spring line with right rudder, rig a forward quarter spring. Take a strain on the quarter spring and ease the bow spring. The current will push the boat back against this line and pull it parallel to the pier.
On a larger vessel, you will need to go ahead on the after bow spring rigged on the port side. Going ahead easily with right rudder on this spring alone, the boat stays under control and eases in nicely. In turning a boat this way, make the turn with the bow—not the stern—to to the pier.
Turning with Power
Consider a situation as described above with the starboard side against a pier, except there is neither wind nor current to assist in turning. Here the power of the engine can be used to swing the boat. Go ahead on an after bow spring with right rudder. This throws the stern out away from the pier; use a fender to protect the bow. Allow the bow to nose up against the pier, using another fender, if necessary, to cushion it.
As the boat swings toward a position at right angles to the pier, ease the spring. With the bow against the pier, the engine going ahead slowly, and the rudder amidships, hold the boat in this position. Meanwhile, cast off the bow spring from on shore; rerig it as an after bow spring on the port side (or use a second line for the port side). With right rudder again, the stern will swing all the way around; shift the fenders once more to protect the port bow.
In any maneuver involving the use of engine power against a spring, the strain on the line must be taken up slowly and easily. A surge of power puts a shock load on deck fittings that they were never designed to carry, and may even tear out the cleats. And with such a surge, if the fastenings hold, the line may part.
Once the strain has been taken up easily, proper deck fittings and good line of adequate size will stand the application of plenty of power. Always bear this principle in mind when you are preparing to tow or when you are passing a line to a stranded boat. Also remember that most docking lines are nylon, and can store considerable energy as they stretch. When the boat is put in neutral or the throttle is closed, the boat can be pulled back toward the pier. If a nylon line is stretched to the breaking point, it can snap back with dangerous or even lethal effects.
TRIM TABS
The performance of a boat with a planing or semi-planing hull is considerably affected by its trim. A high bow-up angle of pitch results in less efficient operation and greater wake. The proper use of TRIM TABS will bring the bow down for a better running angle. These are metal plates usually attached by a hinge to a portion of the lower edge of the transom; see Figure 6-39. They look much the same as the flaps seen on the trailing edge of the wings of an aircraft. In the retracted, or “up,” position they are in line with the bottom of the craft. Moved to a “down” angle of 10 to 20 degrees, they provide added lift at the stern with a lowering of the pitch angle as the bow comes down. A slight increase in drag occurs, but this is acceptable for the desirable effect of a better running angle. Trim tabs are normally used in pairs, and are raised or lowered manually or by one or more actuators for each tab. Actuators are either small hydraulic cylinders and pistons operated by their own hydraulic pump or screw rods turned by electric motors.
Trim tabs must be used intelligently. When a boat is at rest in its berth, the tabs should be in the fully up position—this provides the maximum protection for the “piston rods” from marine fouling. Starting from a standstill, operating in the displacement mode, the tabs will have no effect and should be left in the up position. As additional throttle is applied to get “on plane,” the tabs should be lowered—how much will have to be learned from experience with each individual boat. Properly used, the tabs will significantly help the boat to get on plane, and will reduce the engine power required to stay on plane. Speed for a given engine rpm should be increased by several knots, and fuel efficiency should increase slightly. Once on plane, the best adjustment of the tabs will have to be found experimentally. Trim tabs are not always used with their maximum down angle; it is possible in some cases to get the bow angle down too low, with the result that the boat could tend to yaw from side to side. Most installations will have some sort of indicator for the angle of the tabs; they may be labeled “Tab Down” or “Bow Down”—the effects are exactly the same. Make small adjustments up or down, and after each, wait a half-minute or so for the boat to settle into the new running angle.
Trim tabs should not be used in all conditions. They probably should not be used in a following sea, as it is then desirable for the craft to have a greater bow-up attitude for more positive steering control. In significant head seas, the bow should be up more than in calmer waters, and thus less tab action is called for. Tabs should always be in the up position when backing down—if the tabs are down there will be water pressure on their upper surfaces that may damage the actuator.
A pair of trim tabs is normally operated together, the same angle on each tab. Controls for each tab are separate, however, and they can be adjusted individually. They can be so used to correct for a lateral imbalance, such as a list to port or starboard—an increased angle of tab is used on the low side.
BOAT HANDLING WITH TWIN SCREWS
This chapter has thus far related almost exclusively to a single-screw inboard boat. Although this permits a better study of the basic factors of boat handling, attention must also be given to inboard engine twin-screw craft.
In twin-screw craft, there are twin rudders as well, one directly behind each propeller; see Figure 6-39. The propellers are counterrotating, which balances any steering pull, and will generally rotate “outward”—the right-hand rotation on the right side and the left-hand rotation on the left side. The effect of this is to provide maximum maneuverability.
Figure 6-39 Maximum maneuverability of twin-screw craft is gained by placing twin rudders behind the propellers, where the discharge current can act upon them most effectively. Note also the trim tabs (arrows) located at the lower edge of the transom.
Going ahead with the starboard engine for a turn to port, the offset of the propeller from the centerline adds greatly to its effect of throwing the stern to starboard. Similarly, offset of the port propeller helps the steering effect when the port engine is going ahead for a turn to starboard.
When reversing, the starboard propeller throws its discharge current against the starboard side of the hull to help a turn of the stern to port. Likewise, the port propeller reversing throws its stream against the port side of the hull to help a swing of the stern to starboard.
The important factors in turning and steering are thus combined by the outward-turning propellers. The steering effect is exerted in the same direction as the turning movement caused by the off-center location of the propellers.
Gathering Headway
Unlike a boat with a single propeller, if the transmission gears of a twin-screw boat are put in forward together, the boat will begin to make headway without any tendency to pull to starboard or to port.
Turning
Clearly, having two propellers gives you the means of shifting one propeller or the other ahead or astern, independent of rudder control. In fact, much of a twin-screw boat’s slow-speed maneuvering is done without touching the steering wheel; working the clutches and throttles is the key to controlling the boat’s movements.
One Propeller Going Ahead or Reversing
A boat’s stern may be put to one side or the other by going ahead or backing down one propeller, without turning the other. Some headway or sternway in these cases accompanies the turn.
Referring to Figure 6-40, powering ahead on the port engine (A) moves the stern to port and the bow to starboard; right rudder would assist this turn, but is not necessary. The opposite action, using power ahead on the starboard engine (B), has the opposite result, stern to starboard and bow to port.
Figure 6-40 These diagrams show the actions of a twin-screw craft when power is applied to only one propeller, with the rudder centered. (Arrows show discharge current). One propeller turning ahead turns the stern of the boat to its side. When one propeller is in reverse, the boat backs to the opposite side.
Reversing on one engine results in the same turning action as going ahead on the other. At (C), the port engine has been put in reverse, and at (D), the starboard engine has been reversed.
The maximum turning effect is, of course, obtained when one propeller is turning ahead and the other is in reverse—the two effects are additive; see Figure 6-41.
Maintaining Control while Backing
A twin-screw boat starting from a position dead in the water, with both engines at the same speed in reverse, has a great advantage over a single-screw craft, as it can be made to take any desired course by steering with the rudders. In such a boat, the counterrotation of the propellers means that the force that would throw a single-engine boat off-course is balanced out. Rudder action, however, will be less than when going ahead, as the propellers’ discharge currents are directed away from the rudders rather than onto them.
In addition to the ability to use the rudders, a twin-screw boat offers the possibility of using the throttles to speed up one engine or the other as an aid to steering while maintaining sternway. There is also the possibility of stopping one engine completely, or going ahead on it, for maximum control in backing up.
While a twin-screw craft backs as readily to starboard as to port, it is still subject to the effect of wind, waves, and current. The helmsman, however, has a greater ability to exercise control over these external forces.
STEP-BY-STEP DOCKING WITH A TWIN-SCREW BOAT
Most twin-screw boats are maneuvered in close quarters by using the direction of rotation of the propellers. Depending on wind or current conditions, stop the boat in front of the slip, or slightly to windward or upcurrent. (The rudder may be used if needed.)
The sequence below is intended as an example. Depending on the circumstances, this will sometimes be done in the opposite manner, swapping “starboard” for “port” and vice versa. In this example, both throttles are in idle as you back with starboard engine in reverse. As the boat gathers way, it will begin to back to port. By going forward with the port engine, the boat can be made to pivot and to align with the slip. When alignment is satisfactory, the port engine is also put in reverse to continue backing into the slip. Slight adjustment in direction can be made by putting either gear momentarily in neutral or forward. (On some craft, the placement and grouping of the shift lever and throttles will vary from that shown below.)
1 Stop headway with the starboard engine in reverse; the stern will begin to move to port. Then continue backing with the starboard and port engines at idle.
2 As sternway builds and you enter the slip, go ahead with the port engine to align the boat with the slip.
3 With the boat aligned with the slip, put both engines in reverse; continue backing into the slip. If either engine is put in forward, the stern will move in the same direction.
4 When fully in the slip, put both engines in forward momentarily to kill all sternway. Secure the boat.
Steering with the Throttles
In maintaining a straight course with a twin-screw boat, the speed of each engine can be adjusted so that the leeward engine compensates for the effect of leeway. This is done by running the leeward engine at a slightly faster speed to hold the bow up into the wind. The disadvantage of using this technique is that an undesirable “beat note” or throb sound may be heard when the speeds of the two engines are not the same—when the engines are not “in sync.”
Turning in a Boat’s Length
With practice, you can easily turn a twin-screw boat in a circle only a little larger than the boat’s length, as shown in Figure 6-41. For example, to turn to starboard, the rudders can be set amidships while the port engine goes ahead and the starboard engine reverses; on most boats, turning the rudder is not necessary, but will tighten the turn.
Figure 6-41 A twin-screw boat can be turned in its own length. With rudders centered, go ahead on one engine with the other in reverse (small arrows show screw discharge current). Changing engine speed on one propeller can give the craft headway or sternway if this is desired.
Start this type of turn with the engines at idle or turning slowly at the same speed. To turn to the right, put the port gear in forward and the starboard gear in reverse. As the boat begins to turn, it may start to make some headway. (This is not surprising, since a boat drives forward more easily than it goes astern, and the propeller develops more thrust at a given rpm while turning ahead than astern because the propeller blades are curved so as to produce lift on the forward side.) To compensate, you probably will have to open the starboard throttle slightly to increase the rpm of the reversing starboard propeller. For both engines, a rate of rpm can be found so that the balance will turn the boat in its own length.
When the port engine is speeded up a little, the circle is larger and the boat makes some headway. If the port engine is slowed down, the circle is also larger, but the boat makes some sternway as the reversing starboard propeller pulls it around, stern to port.
Handling a Partially Disabled Boat
If your boat happens to sustain damage to the steering gear, it can still make port by steering with the throttles (provided that the rudders are not jammed hard over to one side). One engine can be allowed to turn at a constant speed—the starboard one, for example. Then open the throttle of the port engine to speed up the port propeller and cause a turn to starboard. Closing the throttle of the port engine slows down the port propeller and allows the starboard propeller to push ahead, causing a turn to port—keep your speed moderate when doing this, as steering is not as positive as with rudders. Since most slow-speed maneuvering is done with the propellers, when you get back to port you will be able to maneuver into your berth.
Stopping
A twin-screw boat is stopped by reversing its propellers, but unlike a single-screw vessel, this will usually not throw the stern to one side.
Docking a Twin-Screw Boat
When docking, the experienced helmsman of a single-screw boat usually tries to make a port-side approach so that, when the vessel is stopped, the reversing propeller will swing the stern toward the pier (or wharf). The skipper of a twin-screw boat can use this technique on both port and starboard approaches. By reversing the offshore engine to check headway when coming up parallel to the pier, the stern will move in. On a port-side approach the reversing starboard right-hand propeller will move the stern to port. When approaching to put the craft’s starboard side to the pier, the reversing port propeller will conveniently move the stern to starboard.
Landing at a pier or wharf, a twin-screw boat should approach at an angle of 10° to 20°, as is the case with a single-screw craft. When it has just enough way to carry it in nicely, the rudders are turned to the side away from the pier to bring the stern in as it comes up parallel to the structure, and the engines are shifted into neutral. To check headway as it comes parallel to the structure, the offshore engine is briefly put into reverse.
Using Spring Lines with a Twin-Screw Boat
When a twin-screw boat is lying in a berth and a spring line is used to throw the bow or stern out as an aid to getting clear, one engine may be used. For example, with an after bow spring, going ahead on the outside engine only throws the stern out away from the pier; in addition, the inside engine could be put in reverse.
Sometimes a twin-screw vessel is gotten clear of a wharf by rigging a forward bow spring and reversing the propeller on the wharf side to throw the propeller discharge current on that side forward between the boat and structure as a “cushion.” Naturally this is most effective if the wharf under water is solidly bulkheaded rather than built on open piling. The discharge current from the inside wheel forces the boat away from the wharf, and the line is then cast off. Further reversing on the propeller nearest the wharf, while the other propeller turns ahead as necessary, shapes the boat up to get the stern clear. The rudders are left amidships until the boat is clear and ready to pull away.
Other Twin-Screw Maneuvers
If one propeller is stopped while the boat has headway, the bow necessarily turns in the direction of the propeller that is dead. Consequently, if one engine of a twin-screw power plant fails, and the boat must proceed on the other alone, a certain amount of rudder angle on the side of the operating engine is necessary to maintain a straight course.
When a twin-screw boat has headway and a quick turn to starboard is desired, the starboard engine can be reversed and right rudder applied. The fact that the craft has headway means that the right rudder adds to the steering effect to shorten the turn.
With sternway, both propellers reversing, if a quick turn of the stern to port is wanted, the port engine is shifted to ahead and left rudder is applied. Again, due to the craft’s sternway, the rudders’ effect is added to that of the propellers to cause a quick turn to port.
If a twin-screw boat has considerable headway and its engines are reversed with rudders hard over, the stern will normally swing away from the rudders (to port with right rudder, and vice versa) until the headway is overcome by the reversing engines. After it has gathered sternway, the stern tends to work toward the side on which the rudders are set.
Caution: When shifting from forward to reverse or vice versa, remember to reduce the rpm’s to a minimum in order to protect the gears in the transmission.
MANEUVERING WITH DIRECTED THRUST
Outboard, sterndrive, and pod-drive boats do not have rudders. The boat is steered by directing the propeller thrust—by turning the outboard motor, sterndrive, or pod unit on which the propeller is mounted. Maneuvering such a boat is usually easier than maneuvering a single-propeller inboard boat of the same type.
Directed propeller thrust makes slow-speed maneuvering easier and turns at normal speeds much sharper; see Figure 6-42. The propeller discharge current is turned from side to side to create turning forces, unlike a boat with a rudder, which must have water flowing by it to be effective. Outboard and sterndrive units have very little or no shaft angle, so the propeller does not produce as much unequal blade thrust as does the propeller on an inboard boat. Larger, more powerful outboard motors and high-power sterndrives do, however, produce considerable propeller torque—twin drives of either type normally have right-hand and left-hand propellers to balance out this undesirable effect.
Figure 6-42 The pivoting drive unit of a sterndrive boat (left) permits a tight turn, while an inboard craft, even a twin-screw boat (right), with its fixed propellers, responds only to the rudders. Jet-drive craft can likewise make very sharp turns at high speeds, even to the point of being dangerous.
How a particular outboard or sterndrive boat reacts to the helm is difficult to predict exactly, but some general principles apply in most situations. Some of these situations—basic maneuvers that any boater will likely have to complete during regular daily operation—are described next. This discussion assumes a typical boat with single outboard or sterndrive power. Boats with two outboards or sterndrives can usually be maneuvered as described above for twin-inboard vessels.
Gathering Headway
When an outboard or sterndrive boat is “dead in the water”—that is, not moving forward or sternward—and the propeller is not turning, the boat will not respond to the helm. Since the propeller is not turning, it is not creating any discharge current, so no turning forces are created. Even though the boat may be moving over the bottom with a current, no water is passing by the lower unit of the outboard or sterndrive; therefore, it cannot act as a rudder.
As soon as the outboard or sterndrive is shifted into forward gear, the propeller’s action creates a discharge current and generates thrust. If the outboard or sterndrive is centered, the discharge current is directed straight back, causing the boat to begin to move forward in a straight line.
If you open the throttle quickly on a boat with a single large outboard or sterndrive, as you would when pulling a water-skier, for instance, torque will pull the stern of the boat to one side, usually starboard, similar to a single-screw inboard. Large outboards and some sterndrives have small trim tabs located behind the propeller that help compensate for these forces, but a firm grip on the helm before the throttle is opened is also necessary.
As the boat gathers headway and the propeller begins to operate in the faster water flow for which it was designed, this imbalance usually lessens. If your boat wants to turn to port or starboard as soon as you let go of the helm at typical operating speeds, the steering trim tab needs adjustment.
Turning
After a boat has gathered headway, with the helm amidships and the lower unit tilted so that the boat is planing at a slight bow-up angle, the average boat tends to hold its course in a straight line fairly well. Once underway, the outboard or sterndrive boat is not affected to any significant degree by propwalk unless the lower unit is trimmed too far out or in.
If the helm is turned to starboard, the outboard motor or sterndrive is also turned in the same direction. The propeller’s discharge current is directed to starboard, forcing the stern to port. Water flowing past the hull hits the lower unit on its starboard side, creating additional turning forces. The stern begins to move to port, causing the bow to turn to starboard.
If the helm is turned to the left, the motor or sterndrive turns to port; the stern of the boat moves starboard as the bow begins to turn to port.
At low speeds, there can be a time lag between when the helm is put over and when the boat begins to turn. At high speeds, there is little lag in helm response. Small movements of the helm result in immediate action by the boat. The faster the boat moves through the water, the greater the forces generated by the water hitting the lower unit of the outboard or sterndrive, which provides a small amount of “rudder action.” Also, the discharge current increases in strength as the throttle is advanced and propeller rpm increases.
It is important to remember that the response of each boat depends on the maneuver and the speed at which it is undertaken. Actual experience at the helm at different speeds is the only way to become familiar with the handling characteristics of any boat.
In order for the boat to begin its turn, the stern must be free to move. For example, the force of a water-skier towline secured to the stern can make steering difficult, since it may prevent the stern from swinging to port. That is why competition ski boats secure the line to a towing post located well up into the boat, forward of the transom; refer to Figure 6-16.
Stopping
Unlike a car with brakes, your boat depends on reverse thrust in order to stop. Assume that the boat has headway, with the helm centered and the propeller turning in reverse. Now the propeller discharge current is directed forward, past the lower unit of the sterndrive or outboard.
Depending on the throttle setting, the screw current may not be strong enough to reverse the water flowing past the lower unit. As power is increased, the propeller discharge current becomes strong enough to stop the flow of water past the lower unit and, as the throttle is opened, more completely reverses its flow.
While water is flowing past the lower unit, there is some steering force generated, but when the discharge current stops that water flow, the boat will temporarily not respond to the helm. When the strong propeller discharge current starts to flow past the lower unit, steering is again restored. In addition to the force of the water hitting the lower unit, the propeller discharge current is directed by turning the outboard or sterndrive, adding to the steering forces.
The propwalk of the reversing propeller tends to throw the stern to port, but to a lesser extent than a comparable inboard engine craft.
STEP-BY-STEP DOCKING WITH A STERNDRIVE BOAT
Outboard- or inboard/outboard-powered boats are relatively easy to back up, but that may be scant comfort to the novice in a busy marina. The reversing propeller is turned in the direction you want to go by using the wheel or motor handle or tiller. On some light displacement boats with shallow draft, the bow tends to be influenced by the wind (coming from the left in the photos below).
When backing down in a crosswind, allow maneuvering room (to port in this example) and watch the bow carefully. If it begins to swing downwind, you may have to stop backing, leave the helm over to port (toward the wind) and go in forward to straighten the boat. A quick burst of power is all that is usually needed, but be careful that you don’t throw your crew or guests off balance with a sudden maneuver.
Set your speed to just enough to overcome the effect of a crosswind. If this doesn’t work, abort the maneuver early, reposition, and wait for a lull in the wind.
1 Bring the boat to a stop by shifting into reverse. Put the helm over to port and begin backing in. Slow your speed by momentarily shifting into neutral.
2 Continue backing with the helm over hard to port. Watch the bow, and begin to straighten the helm as the boat enters the slip.
3 Center the helm to align the boat parallel to the pier. If the stern is too far from the pier, shift to neutral, then put the helm over to port and go forward for a second or two.
4 When fully in the slip, stop sternway by shifting into forward. Put the helm to port to kick the stern over close to the pier if necessary. Shift into neutral and secure the boat.
Backing Down
If your boat is dead in the water with the outboard motor or sterndrive centered, and you put it into reverse gear, the stern will be pushed slightly to port by the reversing propeller. The tendency to back to port can easily be overcome by turning the engine or sterndrive slightly to starboard.
Since outboards and sterndrive boats have the advantage of directing the propeller discharge current, and need not rely on a rudder for steerage, you can also maneuver your boat by the judicious use of the throttle. The technique is to position the drive unit with the steering wheel while out of gear or at very low speed, then to give a short, sharp burst of throttle. The overall effect will be to push the stern in the desired direction while not adding an appreciable forward or sternward motion to the boat.
As the boat begins to gather sternway, the water passing by the lower unit will begin to contribute to the steering force. Unlike most single-screw inboard boats, outboard and sterndrive boats back predictably. If the helm is put over to starboard, the motor or sterndrive will turn to starboard and will direct the propeller discharge current to port, moving the stern to starboard.
However, wind and current will affect how a boat of this type backs. Outboard- and stern-drive-powered boats tend to be light-displacement, shallow-draft craft, and when backing down in a strong crosswind, the bow will tend to fall off downwind. This can cause steering difficulties.
Remember that, in addition to the force of the wind on the forward topsides, the hull’s pivot point has also moved aft, much closer to the drive unit. The steering forces are now acting on a much shorter lever as a result.
Usually, once sufficient sternway is gained, the force of the keel moving through the water is enough to keep the boat on track. Also remember that, when backing, the stern will lead as it moves to port or starboard, before the boat begins to turn.
Jet Drives
Jet-drive boats essentially have a propeller within the hull of the craft—in effect, this is a pump drawing in water from ahead and ejecting it out the stern. There is no rudder—steering is accomplished by pivoting the jet nozzle from side to side of the centerline. Reversing is done by lowering a deflection plate or reversing buckets into the discharged water so as to create rearward thrust.
The vast majority of jet drives will be found on personal watercraft (PWCs), but jet drives have been used on vessels of all sizes, including yachts of 100 feet (30.5 m) or more in length.
The use of jet drives on small, fast personal watercraft provides a high degree of maneuverability and fast acceleration. Steering response is immediate, and turns can be very sharp. Persons taking their first ride on a PWC should start out slowly and get the feel of the craft’s response to throttle and steering before operating at high speed and making sharp maneuvers.
Figure 6-43 The Volvo IPS drive differs from a conventional inboard-outboard drive unit—the propeller faces forward to pull, rather than push, the boat through the water. The entire unit can turn from side to side for steering, but the maximum angle of turn is limited for the sake of safety. The IPS drive is designed to break off cleanly if an obstruction is hit, thus lessening the likelihood of hull damage.
Pod Drives
A new form of directed-thrust propulsion, similar to the pods used on large ships, has become popular in recent years for recreational vessels and yachts. The first of these new pod drives was the Volvo Penta Inboard Performance System (IPS), followed by Cummins MerCruiser Diesel’s Zeus system. The main difference between them was that the twin counterrotating IPS propellers face forward to pull the boat through the water, while the Zeus System utilizes aft-facing propellers, also counterrotating, to push the boat.
Pod-drive engines are mounted far aft in the boat, freeing up interior space where a midships engine room would otherwise be, and they drive the pods, mounted under the boat, via a vertical shaft through the bottom of the hull. Cooling water intake and exhaust are both included in the pod, reducing the need for through-hull fittings in the boat. And the pods are designed to shear off cleanly in case of a catastrophic grounding, eliminating the possibility of a strut or rudder piercing the hull.
The advantages of pod drives are numerous. Since each pod turns independently from side to side, together they add up to tremendous maneuverability at low speeds for docking; at higher speeds, they give the boat a sharp turning ability. They also provide better fuel efficiency and less smoke and noise than do traditional inboard engines.
OTHER SEAMANSHIP TOPICS
Although boat handling is one of the major aspects of seamanship, there are many others.
These include Anchoring (Chapter 9), Special Techniques (Chapter 10), Safety & Emergencies (Chapters 11 and 12), River Seamanship (Chapter 22), and Marlinespike Seamanship (Chapter 23).
Seamanship for sailing craft is covered in Chapter 8.