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ouch, my brain hurts

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Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Initially Posted - 03/25/2007 : 19:15:13

http://www.arvelgentry.com/techs/A%20Review%20of%20Modern%20Sail%20Theory.pdf

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britinusa
Web Editor

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USA
5404 Posts

Response Posted - 03/25/2007 : 20:06:03

Anyone have a translation - sail trim for dummies using that info?

Paul

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Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 03/25/2007 : 21:18:24

Old news - but dumbed down enough that I got to about page 6 before I was saying I think I'm lost. The old presentations had me confused roughly near the section that said "written by:"

I still couldn't present it to the crew with any semblance of looking like a know what I'm talking about but this was definitely clearer than anything I've seen before.

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Brooke Willson
Admiral

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USA
983 Posts

Response Posted - 03/26/2007 : 05:07:22

If I read the article correctly, one of the most important points made is a complete debunking of the "slot effect" explanation for the interaction between jib and main. Sailors usually believe that the the role of the jib is to increase the speed of the flow over the lee side of the main, therefore decreasing pressure and increasing lift (per Bernoulli). The article says that the real function of the jib is -- essentially -- to make the flow smoother (decrease separation), and thereby increase lift. It looks to me as though he says that mainsail trim has more affect on the jib than vice versa. Fascinating.

I'd love to see an extension of this argument as it applies to overlapping and non-overlapping jibs. Garry Hoyt, among others, asserts that non-overlapping jibs are more efficient (which helps him sell jib booms). Chuck Paine at Morris Yachts has embraced this faith in designing arguably the most gorgeous boats being built these days. If you look at a lot of the new racing designs, they have huge mainsails and high aspect, non-overlapping jibs.

Another interesting point of the article is that our jib telltales should be mounted right at the luff, rather than farther back.

I think I'll send this to my father-in-law, who worked for NASA Langley for many years.

Brooke

Edited by - Brooke Willson on 03/26/2007 09:45:01

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