Steering 3

Marathon, Florida
No LL

I bet you can't believe there is so much to just steering a boat. This is the final post on the subject. I promise. Once again, it is for my non-boating friends. (See previous posts, Steering 1, and Steering 2)

When you steer a wheeled vehicle you are used to repeatability. If you turn the steering wheel by, say, 90 degrees you expect the car to turn with a particular radius, day after day, time after time. Not so with a boat or an airplane. The only exception is when your car skids.

Planes are subject to forces from wind while boats are subjected to both wind and water current forces. They don't have wheels on the pavement to override those forces. Therefore, they don't necessarily move the way they're pointing, nor do they necessarily turn as much as you expected.

The rudders on boats and planes, plus elevators and ailerons on airplanes, are the only means of steering. The effectiveness of a rudder is proportional to the speed of the boat. Therefore, when moving slow, you must deflect the rudder more to get the same effect. There is also a minimum speed, called "steerage" or "steerage way" , below which the rudder is ineffective and you are out of control.

What should you do if the rudder is all the way to one side and you still aren't turning enough? Then you should use more power. (I'm talking about motoring, not sailing.) More power makes you move faster eventually. Also, more power moves more water past the rudder immediately. In most boats, the rudder is directly behind the rudder.

Tarwathie has a full keel and a skeg rudder. This design is optimized for blue water sailing, where the most important characteristic is that the boat moves ahead in a straight line. Full keel boats need much bigger turning radii than sail boats with fin keels and spade rudders. Look at the picture of Tarwathie below, and you'll also see that only a small fraction of the rudder surface is directly behind the propeller. Using more power to make Tarwathie turn faster is not very effective.



With practice I have learned to turn Tarwathie on a dime. The technique involves a lot of back and forth movements; like doing a K turn on your car. However, if there is a strong wind or a strong current, I can't do it. The boat would drift away while I was trying.

Sometimes full rudder and full power is still not enough to turn the boat (or the plane). In that case, your intent to turn that way will fail, you must come up with a plan B. This happens when trying to land a plane on a runway with a cross wind. When you run out of rudder, the landing must be aborted.

So what about the poor captain who needs to take his boat in to a slip at a marina. He may have to move down a narrow dead-end corridor with boats on all sides, then negotiate a 90 degree turn into the slip. Imagine trying to do this with strong winds or currents coming from the side or from behind you. There are only two solutions to this dilemma.

1. Abort: Give up the idea and go somewhere else until the weather changes.
   
   
2. The pucker method: Move in to the corridor with plenty of speed to make sure that your rudder will work well. You'll have to negotiate the final turn smartly, then apply full reverse power to stop. Meanwhile your crew will have to handle the lines and fenders to secure the boat as you bring it to a stop. There is no margin or error, or opportunities to retry with the pucker method. Do it right or crash into other boats, with embarrassing and financially ruinous consequences.
   
   It is no wonder at all that bringing a boat in to a slip is the most terrifying maneuver a captain is ever called on to do.
   
   Watching other skippers attempt the pucker maneuver is a primary source of entertainment in some marinas. It's great fun unless your boat is one of the endangered vessels if the skipper fails.
   

I read an article that said that European boaters are getting older and more feeble. American boaters are only slightly behind them. To preserve their market, boat manufacturers are forced to make the boats ever easier to maneuver and to sail. The latest sail boats have bow and stern thrusters, rotating propulsion pods, and joystick steering.

• A thruster is a second propeller mounted in the bow or the stern, which pushes water 90 degrees to the left or the right. Thrusters are aids to steering at low speed when the rudder won't work.
• Propulsion pods extend below the boat. The pod contains the main propeller connected to the engine. A rotatable pod is able to rotate 360 degrees and therefore push in any direction.
• The new joysticks move the boat forward-aft-port-starboard. Also, by twisting the handle they are able to make the boat turn (twist) in the same direction.

Of course, with a sufficiently strong wind, the maneuver will still fail; perhaps spectacularly.