Chapter - 11

Steering

Propeller Working Ahead (Right Hand Propeller)

The water which is drawn into the propeller from forward of it in a line parallel to the keel has no appreciable effect upon steering. However, water is thrown out from the after side of the propeller, more or less radially from the blades. This rotary current set up strikes against the rudder to a greater or less extent (depending upon the position of the rudder and amount of rudder given it) and tends to throw the stern sideways. The upper blades, which are moving from port to starboard, throw their water against the upper portion of the rudder, and the lower blades drive their current against the lower starboard side of the rudder. If the lower part of the rudder is greater in area (relative to the center of motion of the water thrown radially away from the after side of the propeller) the resultant effect will be to throw the stern to port. If the upper area is greater, then the stern will be thrown to starboard. Thus it will be seen that the position and size of the rudder relative to that of the propeller will have a certain influence upon steering.

Propeller Working Astern

Water is drawn in from astern and forced out forward. The water forced out is thrown against the boat's underbody—that from the upper blades against the starboard side, and that from the lower against the port side. As the upper blades are working more effectively in this case, it follows that in backing, a boat's stern will be thrown to port.

Sidewise Force Of Propellers

There is a certain sidewise force exerted by a propeller. The upper blades moving from port to starboard tend to force the stern to port, and the lower blades working from starboard to port have a tendency to throw the stern to starboard. As the lower blades are working deeper in the water, their action will have the greatest effect, with the result that the boat's stern will be thrown to starboard. In backing, the stern will be thrown to port.

This resultant action of the sidewise force of the propeller is quite pronounced in motor craft, especially when the upper blades are near the surface. Most motor boats have a tendency to work off their course to port for this reason. The effect is greatest when the boat is starting from rest, as then the tendency to "churn" the water is maximum when the boat's speed is minimum. For this reason it is essential and desirable to turn to port when starting up if it is desired to change the boat's course quickly. Many motor boats will not turn to starboard until they have considerable way on, while they will turn very readily to port.

Wake Current

The wake current, or that drawn along by the boat, is greatest at the stern of the boat at or near the surface of the water. It rapidly diminishes below the surface. The wake current is maximum at maximum speed of the boat, being zero when the boat is at rest. The influence of wake current, which has the greatest effect upon the upper blades, is to neutralize the greater sidewise effect of the lower blades when the boat speed is maximum.

Effect Of The Propeller Upon Steering

1. Boat And Propeller Going Ahead

Here the rudder is the controlling factor for reasons explained, although the average motor boat tends to turn better to port. If the rudder is put hard over when the boat is going full speed ahead, the first effect will be to throw the whole boat to the side opposite to which it is desired to go, the stern going off the most and not returning to the line of the original path of the boat until the bow has turned several points. The boat turns with increasing rapidity until she reaches a point from which she turns on a path which is practically a circle. As the boat swings around this circle, her bow is pointed inward, and her stern outward. The exact point on her keel which moves around on a true circle depends largely on the boat's speed—the faster the boat is, the nearer the bow will this point be.

The speed at which a boat is moving at the time her rudder is put over has little effect upon her turning space, although the time of turning will be less with the faster boats. If the helm is put over to clear a stationary object, the speed will not be a factor in determining whether the object will be cleared or hit. However, speed will be a factor in the force with which the object is hit.

Generally speaking, a boat may be turned through eight points with a fore and aft "advance" of four boat lengths.

See table which follows for:

2. Boat And Propeller Going Astern

3. Boat Going Ahead, Propeller Astern

4. Boat Going Astern, Propeller Ahead

Table Showing Action of Boat Under Various Conditions
(Right hand propeller, single screw)
                                    1.                     2.               3.                     4.
Direction of Motion
of Boat                         Ahead              Astern        Ahead              Astern
Propeller Going            Ahead              Astern        Astern              Ahead
Direction Bow or          Slightly             Stern          Bow                 Stern
Stern Will Swing           to Port              to Port        to Starboard     Probably
With Rudder                                                                                   to Port
Amidships
Direction Bow or          To Starboard    Stern          Uncertain (I)     Stern
                                                                                                      Strongly
Stern Will Swing                                   Slowly                                to Port
With Right Rudder                                to Port*
Direction Bow or          To Port            Stern          Bow                 Stern May
                                                                                                      Swing
Stern Will Swing                                   Strongly      to Starboard     Slightly to
With Left Rudder                                  to Port                                Starboard

Note: Boat's bow generally cannot be swung to port when backing.

*As stern speed increases, this may change to slight starboard. This is position to steer straightest course when backing.

(1) If the boat has begun to swing from a hard right rudder before the propeller is reversed, she will often continue to swing when the propeller is reversed. If propeller is reversed before putting rudder hard right, the results may be uncertain. To be sure of results, to throw the bow to

Port

1. Stop propeller
2. Port rudder
3. Reverse propeller
4. Starboard rudder

Starboard

1. Stop propeller
2. Right rudder
3. Reverse propeller
4. Left rudder

Recapitulation (Single Right Hand Propeller)

From the foregoing it will be seen that it is practically impossible to make a boat's bow swing to port when backing. Therefore, in maneuvering from a position at rest it is best to plan to turn to starboard as follows:

1. Right rudder.
2. Go ahead with propeller.
3. Go ahead as far as safe, swinging sharply to starboard, gaining as much headway as possible.
4. Reverse propeller full speed.
5. Immediately shift rudder hard to left.
6. Back as far as possible at speed.
7. Propeller full speed ahead.
8. Put rudder to right at once.

If it is necessary to turn to port, proceed as follows:

1. Left rudder. 
2. Go ahead full speed until boat gathers good speed.   
3. Stop propeller and let boat run.
4. Reverse propeller full speed.
5. Starboard rudder immediately.
6. Run astern as far as possible.
7. Go ahead full speed and—
8. Put rudder to left immediately.

On boats of light draft, the whole conditions described above may be reversed, especially when the propeller is poorly or incompletely submerged.

Leaving And Picking Up Moorings

Let us consider now a few of the practical problems you will encounter in handling your boat around moorings, docks and floats. Practically every situation is just as simple as it appears when you watch a good seaman handle it, but it can be made difficult and embarrassing if the few important factors are not taken into account. Suppose your boat is lying to a mooring and you are ready to get under way for a cruise. The engine has been warmed up to get the oil circulating and eliminate danger of stalling after the mooring has been cast off. The dinghy line has been shortened up to prevent its being drawn down under the stern and fouled in the propeller. If there is no wind or current, the boat will not pay off when the mooring line is let go. The buoy is likely to be close under the bow where you cannot see it from the wheel. If you go ahead there is a strong probability that the buoy will strike the hull, and the line will foul the propeller. Consequently it is better to back off until the buoy is in sight, then go ahead, watching carefully that the swing of the stern in turning doesn't bring it too close to the mooring. After you are clear of the anchorage and straightened away, the dinghy can be dropped astern so that it rides comfortably, head high, on the crest of the second stern wave.

If, in the situation above, there has been a current, the boat would drift naturally with it away from the mooring and reversing might not be necessary. If the wind is blowing, the bow may be tacking gently back and forth from side to side as the wind catches first one side and then the other. In such a case we can let the mooring line go as the bow reaches the limit of its tack in one direction, the bow will pay off and it will be easy to get under way without further maneuvering. Deep draft boats with not too much freeboard forward will not tack back and forth in this way at anchor or at the mooring as much as a light hull with high freeboard and no draft forward. Holding the mooring line off to one side of the bow will give the wind a chance to catch that side and help in paying the bow off in the direction you want to throw it.

When the cruise is over and we are ready to pick up the mooring, a man is stationed on the bow with a boat hook ready to catch the eye splice in the end of the mooring line. This end may be buoyed with a small can or wooden float. The helmsman's job is to bring the boat's bow up to this buoy and hold it with the engine if necessary until the man forward has had a chance to get the line and drop the eye splice over the mooring bitt. Overshooting the buoy, the line will be dragged back along the side of the hull. Falling short, it will be out of reach of the boat hook, and you can't expect the man with the hook to drag a heavy boat up to the mooring by main strength when a kick or two of the propeller would do it in more seamanlike fashion. So the engine must be used to hold the bow close to the buoy, though not chafing against it.

Landing At A Float

In coming up to a mooring, you usually have the advantage of being able to approach from the proper direction with respect to wind and current. With docks and floats, it is another story as their construction often makes it necessary to land on a certain side regardless of conditions. If there is no wind or current it is better, with a right-hand propeller, to approach a landing with port side to the dock. In this way when the engine is reversed, the propeller wash against the starboard side of the boat's bottom throws the stern against the dock, instead of away from it.

Whenever there is a choice, it is also better to land on the leeward side (protected from the wind) as in this position, the boat will be held clear and cannot chafe. It may be necessary to work smartly as the wind will blow the boat off. If two men are available, have one each at bow and stern to handle the lines. If you have one man, let him handle the bow line and after this is secure pass him the stern line which has been left coiled ready on the aft deck. With the bow fast, you will have a measure of control at least over the stern with the engine. If you must work alone you can run the bow line aft and the stern line forward along the deck, outside of all stanchions, to a convenient point in the cockpit and carry them both ashore at once.

Allow For Wind And Current

Where the wind or current acts in a direction parallel to the face of a dock it will be better to come up against it, on the same principle as outlined in connection with picking up a mooring. In this way the boat is under better control as the propeller can be turned over slowly to offset the effect of wind and current. With the propeller turning you are in a better position to place the boat where you want it, yet the boat's actual headway is kept down to a minimum.

Sometimes it will be necessary to make your landing downwind, as for example, when coming into a canal lock or a boat slip. Reduce your headway as much as possible and be ready to use your reverse in ample time. A powerful reverse may be necessary to check headway due to the drive of the wind. Be sure to keep the motor turning fast enough to eliminate any risk of stalling. Here the choice of the port side is important if you have two canal walls or dock sides to pick from. The reversing propeller then holds the stern up instead of throwing it away from the dock. You can then run out a stern line without difficulty. This will hold your boat in position until you can get the bow line out as well. If you make the mistake of carrying out the bow line first, the wind is likely to catch the stern and turn the boat around before you have a chance to make fast.

Another awkward situation presents itself when the wind is blowing strong at right angles to the face of the dock against which you intend to land. On the windward side, the wind will blow you against the dock and it is necessary to allow for this in approaching. If possible, keep the bow up slightly to the wind instead of running exactly parallel to the dock. Also try to place your boat so that you bring it up to the right spot while the boat is still several feet off the dock. You can hold this position with the engine while the wind blows you into your berth. In the meantime, have your crew ready with plenty of fenders to be placed at strategic points to
protect the hull. Avoid a berth of this kind if you can, as any sea kicked up by the wind will pound the boat against the dock and make things generally uncomfortable. Sometimes, conditions will justify dropping an anchor to windward, to hold the boat off.

Landing Through The Surf

Of all phases of seamanship, taking a small boat through the surf probably calls for the greatest skill. There are some types of small boats of such excellent design that they will live through fairly heavy seas, even when mismanaged to a certain extent—provided they are in deep water. But when the ground swell rolls in on a beach or bar, and the natural formation of waves is broken up, curling breakers are produced that carry power enough to capsize any but the expertly handled and well designed boat.

The difficulties lie in the steepness of the curling breaker's shoreward side and the speed at which it is driving on the beach. The boat with buoyancy enough to live in a surf is so light that it can be picked up by a breaker and carried like a surfboard at astonishing speed. If caught even slightly off the end-on heading that allows breakers to pass, she may broach to and capsize despite the best efforts of her crew. Or she may be carried end-on at increasing speed on the shoreward side of a roller, stern rising and bow lowering, until the bow is buried in a trough and the stern is thrown somersault fashion over the bow, pitchpoling.

When approaching a line of breakers along the beach from the seaward side it is hard to form an accurate idea of just how rough the surf is, the character of the seas that the boat will be running through, and just where the surf may be a little less heavy, or offer some kind of opening for the landing. From seaward the surf will always appear smoother than when viewed from the beach. Therefore a primary rule to be laid down is that extreme caution must be exercised before entering the surf.

It is generally possible, however, to wait just outside the breakers for a time, studying the succession of seas as they roll in. It will be noted that the outer line of breakers is ordinarily the heaviest so that a boat taken safely through them usually has a good chance of getting all the way to the beach—if handled properly. Somewhere along the beach, because of the configuration of outer bars, the trend of the shoreline, or rock formations, there may be one spot where the surf is a little easier to run.

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