IOMICA Forum

I am considering trying to make my own sails and am wondering how best to go about it. After reading about making sails with blocks I am wondering what the best way of doing this is. My questions are:
Do I need to make a different block for each seam?
Does the lowest seam need any curve inserting or can the panels be joned flat bearing in mind that the outhaul inserts most of the curve?
How many panels should the sail have?

I’m asking these questions because I have been amazed by the performance of single panel sails, I believe in trying to keep things simple and I would rather not make three sail blocks.

Thanks in advance


Chris

spaldi01 wrote: Does the lowest seam need any curve inserting or can the panels be joned flat bearing in mind that the outhaul inserts most of the curve?

I think most sails have a little shape in the lowest seam also, but if you plan on not putting in any shape at this seam then you don't need a seam at all!

spaldi01 wrote: How many panels should the sail have?

the class rules limit the number of panels to four in mainsails and three in jibs.

Chris,

There has been a thread within the forum about sailmaking, please try to find it. I'm not sure anymore which dept/topic it is under in. That would at least give you some idea about this topic.

If you feel that a single or 2 panel sail will be enough for you then I think you should give it a try, building a single panel sail is way easier than 4 panels.

In my opinion however putting shape in the sails is one of the most critical performance item in any sailboat, if not the most important. Even if you have the best, smoothest and finest fins and hull surface or shape you stil won't sail optimally if your sails are not optimal.

To answer your question, in my opinion only, I think the most important area of the sail that should have "shape" is at the middle and top, because as you said the outhaul will control the shape of the lowest panel. However this being said. I think that if you are putting shape in the sails, it should be done that the whole sail should have shape to ensure proper "foil shape" or wing shape. If your middle and upper panels have shape and the lowest doesn't, then adjusting the outhaul will not make the right amount of effect compared to if the whole sail is shaped the same way.

Good luck with your sail building project.

Lastly, from what I understand you just need one mold/block if you area already sure of what shape you want to have. But if you want to experiment with several different drafts, etc. then you will need a mold for each variant. Oh I'm talking about mylar/drafting film sails in this email.

TTFN
Arvin

I have researched sail making further and looked at the previous thread. Unfortunately the urls no longer work. I have found Frank Bethwaite’s High Performance Sailing and Larry Robinsons excellent booklet very enlightening and it appears that the shape at the head of the sail and the distribution of that shape is very important (Just as Arvin suggests.)

Using Larrys method where circular blocks are used it is however necessary so make a block for each seam. So before I spend the next few months making sail blocks I was wondering if anybody out there would be prepared to share their experiences using Larry method (and even their sail block index numbers and seam positions with me.)

I would also be interested to know why some commercial IOM sails have three panel mains and some have four.

Thanks in advance

Chris

Hi Chris,

Maybe you've already read it, but I found the Sailmaking Notes on the Graham Bantock site very usefull in getting started making my own sails.
The notes are downloadable as PDF.
www.sailsetc.com

I've just finished my first set in mylar and it doesn't look that bad, but I'll wait with a judgement till after tomorrow's first testrun.

Regards, Jan.