asymmetric spinnakers

[Daz925]

I'm after a bit of help really. I need to make an asymmetric spinnaker for a model yacht, the problem is I've never been on a sailing yacht to see one in action. I'm more of a powerboat guy.

I have searched the net for spinnaker designs and found a few with a lot of different shaped panels. I don't see how if i cut each panel out and stitch it together by butting them up against one another i will get the desired shape.I am making it from 75 gsm ripstop nylon.

If anybody can point me in the right direction i would very much appreciate it.

I used an asymmetric spinnaker on my prototype of the Melges 24RC and on two 68" RC tri's. Sails by Morgan in Cocoa, Florida built my sails and would probably build yours.PM me and I'll send you Scott's e-mail. A word though: on a model an asymmetric spin is MUCH harder to make work than the symmetrical system I designed using twin pivoting spinnaker poles.
Below are sketches of both systems.

[Daz925]

The yacht isn't rc, its for a uni project, we just have to push it off, and its a race down the pond, kind of thing. We have also been given a budget of £40, so kind of have to do everything ourself. Thanks for your reply anyway.

[bistros]

Originally Posted by Daz925

The yacht isn't rc, its for a uni project, we just have to push it off, and its a race down the pond, kind of thing. We have also been given a budget of £40, so kind of have to do everything ourself. Thanks for your reply anyway.

Lots of good sailmakers in the UK - I'd call one, explain the project and ask for help. Bet they'd either supply scaled panel patterns or even do it for you for free. Certainly mention you'd like to have a sailmaker's marque prominently displayed! Obtaining sponsorship and free help is a lesson everybody needs to learn.

The asymmetrical spin will affect the helm balance (adding lee helm) of the boat quite a bit, so I'd take that into account in designing the CLR. If your model is light enough, and the wind adequate, it will also bring apparent wind into play, so the sheeting of the main and jib will need compensate.

Best of luck.

--
Bill

[Earl Boebert]

Material on free sailing model spinnakers:

http://www.usvmyg.org/sails/sail2.htm

My preference is for a "flattie" asymmetric whose shape equals the projected area of a fully sheeted out main when viewed from dead ahead. This tends to balance the thrust on either side of CL, sort of like the Ljungstrom rig. I've also used the "Jimmie Durante" spinnakers described on the web page to good effect.

Cheers,

Earl