Re: Mast Vang

TillyLucy@aol.com
Sat, 31 Jul 1999 00:18:50 EDT


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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Geez you guys, I hate to rain on your parade but stop and think for a
minute.....

The sail is an airfoil and the lift generated is going to be perpendicular to
the foil. If you start lengthening the windward shroud, tilting the mast
towards the water, it's going to have the effect opposite of what you intend
- the lift vector is going to be pointing at the water, trying to pull the
boat over, kind of like an upside down airplane wing.

What you need to do in an "overpower" situation is to reduce the lift
generated by the sail:

Decrease the angle of attack. This is most easily accomplished on a P-15 by
letting out the mainsheet. On larger boats where it's necessary to cleat the
main, heading up accomplishes the same thing, though it takes you off your
chosen course.

Decrease the depth of the foil. By flattening the sail you will reduce the
amount of lift generated. Tighten the outhaul and the downhaul (See Judy for
tips on bending the mast to flatten the main)

Reduce sail area. Do the obvious thing, reef!! If you can't reef, lower one
of the sails.

Please don't take offense, but mankind has been perfecting the design of
boats for millenia - if there was a free lunch out there, I think it would
have been found by now.....

Best regards,

Dave Kautz
P-15 #1632 Tilly Lucy
Palo Alto, CA