Fibrglassing question

[alyne]

Hi

I have a plastic rotomoulded kayak (Scupper Pro). I want to take a fibreglass mould of part of the boat in order to make a mast step.

My question is, what do I need to do before laying up so I can release the mould from the plastic surface, leaving no damage to the boat? The surface of the plastic is quite course, so I can't just use a release agent. Also as this is a small one off project I am hoping there is a low cost solution?

Thanks in advance
Andy

[marshmat]

Are you taking the mould from the outside or inside of the hull?
I know it sounds crude, but might I suggest plain old paraffin wax? Melt it, spread it on, smooth it with a plastic spreader before it cures. If it's lumpy you can point a hair dryer at it and it gets soft and workable again. $4.99 a kilogram at any grocery store, and it does the job....

[alyne]

Hi Matt

I'm taking the mould from outside the hull so its easily accessible.

Thanks for the suggestion. I knew there had to be a simple solution but couldn't think what to use!

All the best
Andy

[fiberglass jack]

got to love that cheap floor wax works great, the only thing i would be worried about is if the resin will eat the plastic , as u are going to pull a mould from the outside i would cover the hull with wax paper cut several pieces and tape them down with scotch tape, after u gelcoat skin the part with a single layer of glass and let dry, what u will want to be carefull is exotherm heat if u lay up the mould in one shot the heat may distort the plastic , so do it is a few shots

[Frosty]

Will fibreglass stick to Acrylic? Can epoxy be used as an acrylic glue.

[marshmat]

There ain't much epoxy won't stick to, lol!
I've glued acrylic with epoxy in the physics lab, it worked fine so long as the surface was roughened up a bit. It's not as good as an actual 2-part acrylic adhesive but those are really pricey and finicky. I have no idea how the epoxy-acrylic performs in the field as I've only ever done this to build relatively low-stress lab equipment.

[yokebutt]

Andy, most rotomolded products are polyethylene, (often referred to by ungainly acronyms like HDPE and UHMWPE) wich is a great non-stick surface for most resins and glues.