plug constuction

[bevan]

I have Desinged a 4.9m catamaran and I am starting to build the wooden prototype soon. When I've built the wooden prototype and sailed it for a number of hours,then I will have a good idea of the proformance. Then I need to build a plug to give to a fibreglass manufacture. I've heared that for the plug you can use form to go over the skeleton frame. what types of form can I use? Does anyone know of some websites on this issue. If I don't use form then I'll have to use 2mm plywood. I've been advised to the strip planking method. Can anyone explain fully on the strip planking method?

Thanks for all the help!

[gonzo]

The mold is made of fiberglass. Use a demolding agent over the hulls and laminate over them.

[Dutch Peter]

Originally Posted by bevan

I have Desinged a 4.9m catamaran and I am starting to build the wooden prototype soon. When I've built the wooden prototype and sailed it for a number of hours,then I will have a good idea of the proformance. Then I need to build a plug to give to a fibreglass manufacture. I've heared that for the plug you can use form to go over the skeleton frame. what types of form can I use? Does anyone know of some websites on this issue. If I don't use form then I'll have to use 2mm plywood. I've been advised to the strip planking method. Can anyone explain fully on the strip planking method?

Thanks for all the help!

On the foam type:
Quoting PAR:

"If it's a one off mold then you can use anything that will hold it's shape, support the weight of the laminate during cure, be reasonably inexpensive, reasonably easy to work into a fair surface and tolerate some heat during the cure."

Explaining strip planking:

strip planking is 'carvel planking' but with battens in stead of planks. The essential difference is the width/thickness ratio, which is lower for strip planking.

[Herman]

For strip planking and other useful stuff: Buy the "Gougeon Brothers on Boat construction" Book.

Why not using the prototype as a plug? Just fill up al the holes you drilled, and give it a new paintjob.

[newo eloc]

I to designed a catamaran hull and built it out of 9ml maranti ply with epoxy glass over
then I used that as a mold and popped off a single skin polyester grp hull and deck joined them ,then did the same again. Now I have three hulls and am not happy with any of them. in my opinion If you are designing your own hull's you wont be happy with it untill you have built about 10 so what I do now is I build a cheap plug out of concaved 4ml hardwood ($16.oo for 2.4 x 1.2 sheets here) strips 20ml wide over a 4ml ply structure .Then glass over ,if I want it as light as possible I prep plug with mold release agent and strip out ply from the inside when cured otherwise I leave ply in. You can make all the changes you want on the plug but once you build a mold thats basiclly it. I admit I know nothing and will be interested in another opinion

[newo eloc]

Your heavy wooden proto type will perform totally differantly from your lightweight f/glass model as did mine. I suggest you go straight to glass. but I know nothing

[yokebutt]

Don't overlook the possibilities of plaster and other cheap construction materials.

For a "sailing plug" we usually cover the "skeleton" with core-foam and laminate the inside skin once the mold is taken and the shell is off the plug.

Yoke.