April 9, 2009

All about rudders

THE SUBJECT OF today’s lecture is rudders. Like teeth, rudders are very nice to have. Rudders allow you to steer the boat, something that is so highly desirable that it makes you wonder why Western “civilization” didn’t adopt them until the year 1200 or so. Before that, Western vessels were steered with paddles or oars, usually slung over the starboard (steer-board) quarter.

In passing it should be noted that the Chinese are known to have had proper rudders in about 200 BC – 1,400 years before the idea occurred to Europe’s brightest spark.

Of course, the subject of rudders is not very exciting for most people. Rudders are usually hidden underneath the boat somewhere, and only warrant scrutiny if the boat is hauled out for bottom painting or repairs. Even when you can see a rudder (or part of it) hanging off the stern of a boat, it doesn’t arouse much excitement or passion.

Neverthless, the subject of today’s lecture is rudders, so we shall press on.

Rudders are quite large in sailboats, compared with those of powerboats, for better control at slow speed. But even though they’re big, they won’t work if you turn them more than 35 degrees away from dead center. More than 35 degrees and the whole rudder blade will stall.

If you have a tiller, it’s easy enough to see when the rudder is being pushed over too far. On a boat with wheel steering, however, it’s a good idea to fit rudder stops to prevent the rudder from turning more than 35 degrees either way.

The rule when you’re using a sailboat’s auxiliary engine in reverse is to hang on tight to the tiller, because if you give it half a chance the rudder will slam over hard one way or the other. Even if the spinning propeller doesn’t chew a big hole in it, the tiller might thump you in the ribs.

It doesn’t need much brain power to figure it out, of course, but the farther aft a rudder is, the more leverage it has to turn the boat. That’s why a transom-hung rudder is more efficient than one whose stock comes up through the cockpit floor. I prefer rudders fixed to the transom, not only for their better turning power but also because if something goes wrong, they’re easier to fix, with their readily accessible pintles and gudgeons. I used to like to talk about pintles and gudgeons around the office water cooler when I was younger. It made me sound like I knew something and the girls would flutter their eyelashes at me.

Many racing sailboats have balanced rudders. They have a small portion of the rudder area in front of the rudder stock to make steering easier, say 15 to 17 percent in front, and the rest behind. I once had a Santana 22 that was like that, but she suffered from lee helm in light weather and the balanced rudder made her wander all over the place. It was very tiring for the helmsman.

Cruising boats don’t need balanced helms. They benefit more from a rudder hung from the end of a full keel, or from a skeg. Such a rudder offers less resistance when it’s turned, and allows for a less disturbed flow of water to the rudder blade.

I see some of you are nodding off already, so I’ll cut this short by saying that the whole subject of how a rudder steers a boat is quite fascinating. It involves a wedging action of the whole length of the hull once the rudder has initiated a turn, and the hydrodynamics are extremely interesting. Well, I, at least, think they are, but I can spot a lost cause as well as anybody. So I’ll just finish by urging you to think good thoughts of your rudder next time you’re sailing. You need your rudder more than it needs you.

Today’s Thought
He who will not be ruled by the rudder, must be ruled by the rock.
—Isaac D’Israeli, Curiosities of Literature

“Hey, Fred, that cow you sold me dropped dead last night.”
“Gee, that’s too bad. She never did that before.”

1 comment:

Jeff Young said...

Your post about rudders is quite timely for me. Last weekend I had the lower pintle fail and come right out of the gudgeon, transforming my transom hung rudder into something more like a raft floating aimlessly behind my 23' sailboat. I finally ending up on the rocks and it wasn't pretty. So, yeah, rudders can be VERY important. Great post!!