Beachcat Jib Design

Hi,
I want to make a new jib for my Maricat 4.3. I have all the necessary supplies and tools, but I need some advice on shape parameters. I intend to use Sailcut CAD to design the panel shapes, but am unsure of what values to use for draft depth and position, as well as twist.

Can anyone suggest some suitable parameters for a 14' beachcat?

Leon.

 

Welcome to the forum.

Designing a well suited sail for your needs, is much like designing a well suited wing for your airplane. If you don't have the understanding necessary to make the choices, then using a program like SailCut will just produce a pretty picture of proposed panels, that may or may not fit your needs. Simply put, a well setting sail requires a fair bit of experience and understanding and though you can learn this information, it might be best to just contact SailRite or a local sail maker and have one developed for you.

I know this isn't what you wanted to hear, but sail design and making is pretty specialized. Sailing making in particular is hard work, if you want a sail that sets well and more importantly wears well. It's a lot of hard hand work and everyone I've known, including myself, after having made a sail, quickly understand and accept that sail makers earn every penny they charge for one.

You might find you can work with a local sail maker, having them design up the panels and supply you with these dimensions, so you can cut and sew. Of course, sewing the panels together is just a small portion of the job.

 

I think you might want to consider the main also. My sister had a new jib made for her boat by a sail maker, it was a nice jib that set well, but over powered the main.

 

Thanks for the responses. This is purely a learning exercise for me. I understand that the best and cheapest way to obtain a well-made sail is to purchase one. I give full respect and credit to the professionals.

That said, I don't think that a simple jib for a 25 year old, occasionally used, non-racing beach cat is an overly ambitious project for a motivated amateur. I would even wager that with a bit of research and experimentation, I should be able to make a sail which performs and certainly looks better that the stretched, rust stained, tattered old thing I've been using for years.

Regarding the aircraft analogy, you are right. I keep in mind however, that successful albeit crude ultralights have been built by motivated amateurs. I've even seen one that used two beachcat masts and mainsails as the wings! A truly terrifying machine. That is the level of sophistication we are talking about for my boat.

I've ordered "The Sailmaker's Apprentice" by Marino. Can anyone suggest any other useful references?

Thanks,
Leon.

 

Not for nothing, unless you have a good grasp on the fundamentals, you'll just sew up a fair bit of costly material that will perform not much better then the bagged out jib you currently own.

Sailmaker's Apprentice will offer the details for assembly, but not panel shapes and layout. How much luff round, how high to make the clew, how much draft, where should the draft be located, etc., etc., etc. These are the things you'll need to learn.

 

I agree, those are the things I am trying to learn. Thanks for the pearls of wisdom.

 

You could just accept the "stock" jib SailCut offers, after you punch in the basic dimensions. Of course it may not be well suited to your boat, sailing style, average wind strengths, etc., but it'll probably set fairly well, in some conditions and on some points of sail. I haven't played with SailCut in decades, but you may have to buy the full blown version to get usable output. You may also want to get a few books on sail design. Those from Gutelle will be good.

 

Sail making isn't too hard. Give it a go. I've built multiple sets of working sails for my boats which perform quite well though I had access to a professional sail loft.
A generic jib design for a beach cat is probably the best place to start such an exercise because it is small, not for racing and can be recut several times if need be. It will be a good learning exercise.

 

Isn't the big difference in jibs for beach cats going to be the lack of forestay tension? I don't think I would want to use standard keel boat parameters.

 

Sure, forestay tension is an issue that the design will have to accomodate but most olde style beach cats get their tension through the main sheet and the Mari can do the same. It isn't the sort of issue that I think should dissuade someone interested in sailmaking. You could always go back and put more hollow in the luff curve if you found that sag was leaving you with and excessively full sail.

 

My copy of sailmakers apprentice covers all these topics and gives good starting points for designing a sail...

 

Sailcut allows you to enter a number for luff round that will compensate for jib sag.

The best book I have found for sail design is "SailingTheory and Practice" by Marchaj.

http://www.amazon.com/Sailing-Theory-Practice-C-Marchaj/dp/0396084281

It has has some hard to find information about twist camber and draft.

Software for analysis of sail aerodynamics of Sailcut designs can be found here:

http://www.xflr5.com/sail7/sail7.html