Sails Design

[simonech]

Hello all,
I've just registered to this forum, I found it very interesting.

I'm a sailor and in my spare time I started reading things about sailing phisique...
I'm very interested in the "aereo part" of the problem: the sails.

My question is:
once I decide which shape to give to my sail (chord, camber and so on) how can I enforce this shape in my sail?
A flat sail can take the shape just over a certain amount of wind, but with lower wind, how can I do?

I've know about pannels sewed togheter, but I don't know how to convert a certain airfoil shape to geometry and combination of pannels...

Does anybody can give me some pointer (or explanations) about this topic?

Thank you
Simone

[gonzo]

Are you trying to go hi-tech or cutting "on the eye".

[simonech]

I intend to cut panels.. no hi-tech... just learning the basics of broadseam...
But how do I desing the panels?

Th

[gonzo]

To get the shape from flat panels, one edge is curved. That is, the camber in the sail will be determined by the curve cut into it. Think of the staves in a barrel. A sail is similar. The curve on the edge of the panel will follow the curve of the camber you want. Of course this is a bit simplistic, since the mast, boom and batten also affect the shape. It is a starting point. Some of the new sailcloths are very rigid. They are much more difficult to shape. I think it would be easier to work with a softer material. Also, if you want reefs in the sail, the very rigid sailcloths make it hard to work with.

[simonech]

Ok, but what I was looking for was:
I want the max camber at 40% of the chord... so I'll have to do a curved panel with the maximum width at 40% of the lenght, but is there any formula about the width difference form max to min panel width to have a prefixed camber?

Thx
Simo

[gonzo]

This is an aproximate formula that works pretty well. Calculate the camber in pecentages of the length of the panel. The curve of the edge on the panel will be proportional to the camber. For example, if at 40% the camber is a curve with a height 12% of the cord, at 40% the panel needs to be cut 12% of its width. Remember that sails twist, so the camber needs to decrease on the upper panels.

[simonech]

Ok. I'll give your formula a try.
Thank you very much

Simo

[gonzo]

I checked out your website. What's the video about? I couldn't access it.

[simonech]

eheh.... can u read italian?
u entered in my gf section (history of D).. she is a video artist, and the video is protected because it's under work

[Polarity]

go here: http://www.sailcut.com/ and check out Sail cut 4

Paul

[giramonti]

I suggest you read Tom Whidden's book, The Art and Science of Sails. It will give you a very good base in sail design. The book is a long read, and a lot of what is covered is not relevant to actual design, though there is some vital information inside. Topics covered are twist, camber, max draft, longitudinal camber distribution, and more that I can't remember. The book definitely covers design, but barely covers construction, which is what I think you're looking for. Another book is Brion Toss' "The Sailmakers Apprentice." I have to admit, I didn't really like the book because the techniques are old, or more positively, they are fundamental, and I'm more interested in modern sailmaking techniques. If I remember correctly, that book does cover building draft into a sail, sewing techniques: batten pockets, grommets, luff rope, etc.

Both books are expensive so you'll probably want to look before you buy to make sure they have the info you want.

[simonech]

Thank you very much... I'll look for the second book.

Anyway, your is a very nice company
thank you
Simone