October 26, 2010

A noteworthy turning point

WHAT WOULD YOU SAY is the most unappreciated part of a sailboat, the one that’s invariably overlooked and neglected, but without which the boat simply cannot function? Yes, that’s right, it’s the rudder.

It’s out of sight (apart from the few stern-hung rudders still around) and it’s largely out of mind. It’s a truly modest and uncomplaining piece of equipment, one that doesn’t need to be fed constantly with expensive diesel fuel, one that never goes flat and needs charging, one that never has to be taken to the sewage pump-out every week, or varnished every six months.

It is a marvel of efficiency; and also a marvel of such simplicity that you have to wonder why it took so many hundreds of years to make an appearance on sea-going ships.

The ancient Phoenicians, the Romans, and even the Vikings, used steering boards — oars or paddles, usually hung from the right-hand quarter. (Hence the starboard -- steerboard -- side. The other side was the side that rested against the port, so the steerboard wouldn’t be damaged.)

It wasn’t until 1242 A.D. that pictorial evidence appeared of a centerline rudder on a ship in Europe. It was, if you’ll forgive me, a turning point in marine design. Apparently this new-fangled invention was received with such enthusiasm that it was quickly adopted by shipbuilders all over the world. Pintles and gudgeons suddenly became household words.

How does the rudder work? Well, in the crudest of terms, if you push it to one side, the water flowing past strikes that side with more force than it strikes the other, so the rudder tends to be pushed sideways, taking the stern with it.

I often marvel at the way a tiny rudder can turn a 250,000-ton oil tanker; although, lurking in the back of my mind somewhere is something vague I once read about the rudder only initiating the turn, and the ship’s hull itself acting to reinforce the turning moment, as might a wedge driven through the water.

While most rudders lurk quietly and invisibly beneath their mother ships, the importance of their roles has not been lost on naval architects, physicists, and engineers. The design and performance of rudders is the subject of countless scientific papers and even whole books. In this respect, if you should wish to develop your latent rudder fetish, get hold of a book called The Development of the Rudder, by Lawrence V. Mott. It’s a fascinating and lavishly illustrated volume of nautical archaeology that digs deep into the conception of the modern rudder, starting with its crude but rather interesting parents in various parts of the world.

Even if you don’t find yourself entirely enthralled by rudders, it will help while away large parts of the cold and soggy winter we’re expecting around here, thanks to La blasted Niña.

Red faces over snakes
THERE was some editorial embarrassment at the Walnut Street Gazeout (should be Gazette) this week. You’ll recall that an inmate was asking for help in finding a book called The Tactics of Small Boa Tracing.

Well, it turns out that either his handwriting was illegible, or his contact down the row doesn’t read too well. The book in question is actually The Tactics of Small Boat Racing, by Stuart H. Walker, MD. It’s still available, and any decent bookstore can order it for you.

Today’s Thought
The ancient sailor said this to Neptune in a great storm, “O God, thou shalt save me if thou please, if not, thou shalt lose me; yet will I keep my rudder true.”
— Montaigne, Essays

Boaters’ Rules of Thumb, #112
Rudder efficiency. The average sailboat rudder will stall and lose efficiency if it is put over more than 35 degrees from dead ahead. In fact, it will act as a good brake if you are approaching a dock too fast and you can put it over to 90 degrees, first one side and then the other.

“And you, madam, what’s your husband’s average income?”
“Oh, usually well after midnight.”

(Drop by Monday, Wednesday, Friday for a new Mainly about Boats column.)

1 comment:

Oded Kishony said...

My Paceship PY26 has a stern hung rudder which seems an ideal arrangement it's easy to access, effective,and can be removed for repairs without hauling out the boat.
Why are stern hung rudders losing popularity?