May 1, 2011

Knowledge and its dangers

I WAS REMINDED recently of how much there is to learn about sailing, and how easy it is to make a fool of oneself. Perhaps, of all mankind’s sporting activities, this is one in which a little knowledge is the most dangerous.

This reminder came to me after I read a post on a sailboat bulletin board from one of those know-all blowhards who irritates beyond distraction.

He said:

“Cat boats develop more lift per square foot of sail area compared to sloops. This is because the (only) sail flies in clean air, as opposed to the downwind sail in a two sail rig flying in dirty air. There is a racing class (which name I can not recall) where (for all practical purposes) the ONLY thing controlled about the sail is TOTAL area. No sloop has been competitive in that class since 1964, only cat boats.”

This man has obviously never heard of the Square Meter classes that originated in Scandinavia and spread all over the world. There are about nine of these classes, also known as Skerry Cruisers, and the basic idea is that the sail area should be limited, but the design of the hull left free. And no designer, to the best of my knowledge, given the complete freedom of designing any boat hull or rig to be the fastest around a normal racing course, ever came up with a cat-boat.

The reason is very simple. A boat with a single mainsail cannot point as high as a boat with a sloop rig. As anyone who has read Arvel Gentry knows, the jib causes a “bend” in the wind ahead of the boat that allows a sloop to point higher than a cat-boat.

I once crewed on a 30-Square Meter in a Lipton Cup contest, and it was fascinating to see the ideas yacht designers came up with to create the fastest boat limited to 323 square feet of sail area, about 20 square feet less than a Catalina 27. All were long (up to 47 feet overall), skinny, and classically beautiful. All had long overhangs and all were sloop-rigged. None were cat-boats.

Today’s Thought
True knowledge is modest and wary; ’tis ignorance that is bold and presuming.
— Joseph Glanvil, Scepsis Scientifica.

Boaters’ Rules of Thumb, #193
The speed of non-planing hulls is governed principally by waterline length. The formula for determining maximum normal speed, in knots, is the square root of the waterline length in feet times 1.34. It is possible to exceed this speed slightly while surfing down the face of a wave, or by installing an overly powerful engine, but for all practical purposes this formula provides the average highest consistent speed for a hull that cannot plane. It is, in fact, the speed of the wave the hull has dug itself into.

“Hey, look at this, I found a green snake.”
“Oh don’t touch it, darling, they’re just as dangerous as ripe ones.”

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

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