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#1 2005-05-28 09:19:35

Guest

Measuring for a head sail

I am thinking of buying a used 150-170 of the internet.  I measured my luff using a measuring tape attached to a halyard, sent it to the top, measured to the deck shackle. The measurement was 35'6". I belleve this is my maximum luff length. If I want to race with the sail and apply tension should I be looking at a 35 foot luff with 6 inches for stretch or a shorter luff.
I am also confused about LP and foot length. If I want a 155, should I be looking for sails with LP in the 15' 7" range or is it the foot I should be concerned with.
I've never bought a sail before so any help is appreciated.
Regards
Cameron
1987 C&C 27 MKV Sail#575

#2 2005-05-28 10:03:47

davidww1
Member

Re: Measuring for a head sail

If you are buying a dacron sail, you will want to make allowance for stretch, but laminated materials don't stretch very much (in the order of one or two per cent). Most of what you take in when you tension a halyard is the halyard itself (unless you are completely crackers and have sprung for high-modulus halyards and even then you will get some elongation from straightening of the fibres).

This site gives, on the Sea Change page, a Luff Perpendicular (LP) of 15'7" for a 155% genoa, so you've got that part right. Foot length isn't an issue for racing, but will give you a sense of the sail's shape. If you think about the geometry involved, a high-aspect-ratio sail will have a relatively short foot length, while a low-aspect-ratio sail will have a foot length more closely approaching the leach length.

All of which is to say that a sail with the right luff and the right LP measurements may not fit your boat. I would suggest that you try to get hold of a genuine Mk V 155% genoa, pick up the measurements from that (luff, foot, leach) and then try to ascertain what any variation in these measurements means to sheeting positions, etc.

Sails that are an almost-fit can sometimes be modified successfully, but there are limits to what can be done if you want to race and enjoy the process.

David Weatherston
Towser, Toronto
C&C 27 Mk IV

Last edited by (2005-05-28 23:28:31)


David Weatherston
Towser, Toronto
C&C 27 Mk IV

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