Dumb GRP Question

[Stemar]

I'm thinking about a fairly small GRP project, basically, a hard sprayhood for Jazzcat. First thoughts were to use Divinycell or similar as the core, but I have some 6mm double wall polycarbonate lurking in a corner of the shed. Would epoxy stick to it to make a rigid shape, or would I be better off using it as an easy release mould?

 

[Boathook]

I would make it out of ply and cover with epoxy, etc.

 

[Keith 66]

Epoxy made stick to Polycarb twin wall but its hard to work the stuff, As for plywood most today is such poor quality its a waste of epoxy using it. Why not use PET foam core? Its much cheaper than divinylcell & similar pvc cores. It can also be had in a recycled version. We used some a few years ago in a project & it works well with both polyester, vinylester & epoxy. East coast fibreglass is my go to supplier.

 

[Trident]

There are specialist epoxy types that will stick to polycarbonate but its probably not worth the hassle and cost - foam core is easy to work (cut with a stanley knife, shape with a router or just a file and sand paper) and remarkably cheap compared to the cost of the other materials. You can of course then choose to use polyester resin rather than epoxy which is much much cheaper and plenty strong enough for what you are making and nice and quick to cure . Drill small holes through the foam to allow penetration. You can always do the tabbing to the superstructure of the boat with epoxy at the end if you're concerned about the strength of join