Hi,

I'm a teacher and work with teenagers and am considering building a kayak with one particular class group. I already have a mould from which one successful polyester/glass boat was pulled about two years ago. The mould is also polyester/glass with a polyester gelcoat. The mould needs some minor modifications to change aspects of the kayak design that have become apparent in the meantime. Basically, I'll need to cut six slots, remove some material and then re-glass up the mould to make it rigid again. The total area of the modifications will be 6 slots each about 1 inch by 3inches. I intend to make the new boat from resin infused epoxy with a mixture of reinforcements including carbon, diolen, glass and kevlar with soric as a core material.

I understand that a polyester mould is risky to be using with epoxy, so my first question is whether the epoxy compatible gelcoat will lessen the chances of the new component sticking to the old mould?

The second question is whether I should use other materials to modify the mould to prevent there being any fresh polyester in contact with the new component? (if so, which materials?)

Third question, what release agent should I use? (the mould has a good finish and was well prepared with release wax previously),

Thanks,

Donnacha.

What type of boat is this?  The reason I ask is that I have paddled slalom boats of carbon (600g) / PVC foam carbon kevlar 2x200g which have been very light and rigid but dont take a bash too well to squirts which have been 6x600g carbon (!!!)  these are freakin' rigid and take a good battering but quite heavy.  The intended use should dictate your laminate.

On the original question, I have taken epoxy moldings from polyester moulds without problem.  I find a cleaned mould with PVA release agent works well.  I spray the release agent and build up coats over a few hours to give quite a thick, strongly blue, layer.  If you spray on multiple days it doesn't work.  When you de-mold it pulls the release agent apart so its a one-shot release but it works OK.