I am researching building my own paneled sails using the Claudio tool. One thing has me stumped: How to build twist into a sail? I understand the process of using sail controls to induce twist and the reason for twist. However, there is often mention of actually building some twist into a sail when it is made, but I can't find any information as to how exactly that is done. Is it function of changing the max draft % at different seams as you move up the sail? Is it function of changing the max draft position at various seams.? A combination of of these two, or something else entirely?

I have studied some spreadsheets that sort of talk about twist, but am not sure what final parameters I should be trying to build-in to the sail. One article I read mentioned that as the sails twists out at the top, it looses lift and to counter act that some extra draft should be built in to the top section(s). On the other hand, I have been playing with the "Sailcut CAD" software. In their default sail plan they show shallower drafts at the foot and top moulds with a twist of 18 degrees. These two items seem contradictory. ?? Also, changing the twist in the "dimensions" section of the software definitely changes the twist in the "view" of the sail, but doesn't change the draft figures. So maybe twist is something that I cannot build in using a Claudio tool. Maybe it has to be calculated by the software and is reflected in the pattern printouts for each panel. I do not have the facility to printout full size patterns and trying to manually plot the points has resulted in poor results.

As a related question: I am building a main sail that is approximately 23" at the foot with a luff of about 59". the boat is similar in LOA and shape to an EC12.
I am not sure what max draft %'s I should use. I have decided to try a 5 panel sail (4 seams).

Any input. ideas and info on this issue would be greatly appreciated.

dcassel

I have always located draft at the same distance from the leading edge which gives more chamber at the head of a sail. Not really twist, but it does result in a more full sail at the top.

Twist is not built into a sail it comes from adjustments to the vang & sheet. Draft is built into the sail by means of luff curve & broard seams. Suggest you have a look at Ben Morris's website.
Andrew

Send a PM-Private Msg to RodCarr

Rod has A LOT OF SAIL MAKING EXPERIENCE that he might share in a PM vs forum post

CARR SAILS, 3011 - 177th Ave. NE, Redmond, WA 98052 (425) 881-2846
rodcarr @ carrsails.com

You will find this site has very good, well laid out with in-depth information, explanations & tools for making your own sails http://www.stirling.saradioyachting....sailmaking.htm

Thanks all. I'll follow up.
dcassel

Thinking out loud - if twist is not built into a sail, it is usually fairly easy to tune some in to suit conditions, but if it is built in, how easy is it to tune it out? If built in twist was a huge advantage, everybody would be doing it and the sailmaking instructions would have plenty to say on the subject. Just a passing thought.

Twist is the result of varying tensions along both the foot and the leech of a flying sail. While twist is not actually built into the broad seams, a basic understanding and quantification of the desired final flying shape of the sail must include consideration of twist. As a sail twists the resulting camber at any height aloft in the sail changes. Typically the head becomes flatter as the twist is increased in the sail.

RESET ONE hit the nail on the head in his earlier post in this thread.