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Leach roach & battens

Printed From: Sailrite Enterprises, Inc.
Category: Sailmaking
Forum Name: Sail Design
Forum Discription: Sail shape, two dimensional and three dimensional
URL: http://forum.sailrite.com/forum_posts.asp?TID=2449
Printed Date: 09 April 2020 at 1:45am


Topic: Leach roach & battens
Posted By: shipmate44
Subject: Leach roach & battens
Date Posted: 26 October 2012 at 3:37pm
Hi all from the UK.
Having read James Lowell Grants books on sail design , I have decided to have a go & make my own sails.
My boat is a 17ft  Daysailer with a steel swinging centre plate & Bemudan rigged.
Main sail dimensions are Luff 5.3 meters, Leach 5.7 meters & foot 2.3 meters.
This foot measuement would give me a batten length of 576 mm using Mr Grants formula of 12% of foot length + 300 mm.
My roach would therefor be between 190 mm to  288 mm.
However my origional sail ( which is over 35 years old ) has 762 mm battens which would give me a roach of between 251 mm & 381 mm.
The max roach on my old sail is approx 340 mm but it is so worn is difficult to make it set anywhere near well
I will probably be using 2.7 %  one tenth camber ratio unless advised diferently here
What  batten lenth would be most appropriate please as this also affects the leach roach sizing.
Many thanks



Replies:
Posted By: MattGrant
Date Posted: 26 October 2012 at 4:59pm
There is no right answer here. If you want a larger roach and there is no "class rule" restriction and there is no backstay in the way you can go large. You just don't want to go so large that the back edge becomes unsupported. But either of your examples are reasonable.
Best Regards, Matt Grant
Sailrite
 


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Best Regards,
Matt Grant
Sailrite


Posted By: shipmate44
Date Posted: 29 October 2012 at 5:18pm
Thanks Matt.
I'll probably go with something close to the origional sail.
I did forget to mention I was thinking of making it a loose footed sail rather than roped as it used to be , would this affect roach sizing ?


Posted By: MattGrant
Date Posted: 30 October 2012 at 8:03am
No, not of the leech edge.

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Best Regards,
Matt Grant
Sailrite



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