If you coat it, it would loose it's shine anyways. I had always had problems when using any 1k stuff, even when I used a 2k paint on top. Pva ruins your shiny surface, if you don't spray it very carefully. You could remove the acrylic with acetone and then coat the plug with whatever you want. That's just as much work as to coat the plug without removing the paint.

Notice in the same post when I said “poly and epoxy are compatible” I also said ONLY use epoxy for bonding.

In terms of having a plug made epoxy or poly, theyll play nice with each other when laying up a mould or pulling parts from it.

Jason

Would it be possible to use a barrier over the acrylic painted pattern such as ‘pva mould release’ or ‘advanced board and mould sealer’ do you think? Can I paint pattern coat primer over it or a 2k paint? Help I am desperate if I have to strip the lovely shiny paint from the pattern!

Should’ve asked before I know!

It was certainly the other way around. You can paint polyester with acrylic paint, but you can't paint acrylic paint with polyester. Because the styrene will attack anything that is not 2k.
Everything without a second hardener component will cause problems during the mould making no matter if you use polyester or epoxy. Usually the plug won't release properly from the mould. In adition polyester attacks the paint, so that you will get defects all over the mould.

Thanks for all the useful advice!

I have a problem now because the buck is now painted with acrylic-nitro - I had read that Polyester on acrylic was ok but not the other way around. Can I use an epoxy on the acrylic paint? Hopefully I don’t need to strip all the paint off - that would be a job...

I will cover the steel with a pure epoxy coat before bonding it into the piece in a second epoxy carbon fibre hand lay operation.

Then I will join the front and back with epoxy adhesive.

Then I will make some holes and inject some 4 pound resin.

Thanks

Sorry to interrupt, but acrylic paint isn't a good option to finish the plug. Even with epoxy there are problems, but the styrene in the polyester will attack the paint heavily, and your mould will be wasted.
If you haven't got the equipment to spay a 2k primer, you could use a polyester brush/roll primer, like the one from ec.
"Polyester and epoxy are compatible" is a dangerous sentence. Epoxy bonds to polyester quite well, but polyester doesn't bond to epoxy.
If you want the steel for extra weight, a few layers of thick glass cloth could be an easier and saver option. If you want to use the steel for fixing, it will obviously be exposed. You should always protect steel from the carbon. Never laminate c.f. directly on steel. Either use a thin glass cloth as first layer, or use special ep or urethane primer first.

if there is an epoxy surface coat you have nothing to worry about. If it’s epoxy and carbon without a finish then it will corrode over time.

I’d use two part expanding foam with a 4 pound density. I’d avoid the stuff in a spray can.

Jason

I’m not sure what youre using the steel for. Is it to add rigidity to a mould or a finished part?

If for a mould, youll need to insulate the steel with E glass to protect it from the Carbon, OR, completely seal the steel off from any oxygen exposure to prevent galvanic corrosion.

Also, sand the steel with 40 or 50 grit paper thoroughly. Clean it in uni directional wipes with acetone multiple times. Using a swirling motion just spreads residual dirt and grease around the metal. Add the metal to the layup shortly after the acetone evaporates.

The foam idea sounds good. Is it needed though? Also are you using it to add structure or floatation? Use 2 pound foam for floatation, and 4 pound or higher if youre looking to add some rigidity.

Jason

+x

 

JasonFL - 4/13/2019 2:43:49 PM

Polyester and Epoxy are compatible. Polyester and Urethanes are for a very short time period. If the poly is under the urethane it will off gas and eventually create bubbles in the urethane and ruin your plug. I ruined many, many plugs this way before some one mentioned the compatibility issues.When building plugs Polyester primer is all you need. It can be polished to a mirror. Really is no reason to use anything else.For bonding always use epoxy and under 100 grit sand paper for prep. You’re relying on a mechanical bond if youre bonding post cure. Bigger scratches for the epoxy to bite into, the better.

So I'm not using Urethanes but Acrylic - didn't manage to find any polyester primer in time - but acrylic paint seems to be compatible when over-slapped with gel coat/ polyester resin/glass fibre?

The mould will therefore be polyester and I will fill it with Epoxy Carbon Fibre - all as per the bonnet EasyComposite tutorial... which is extremely clear!
I think I will bond the steel in with the lay-up of the carbon fibre so there is a chemical bond over and around the steel for maximum rigidity - good idea or not?
Final piece of the puzzle - when I connect the top and bottom parts I will have a hollow piece which I want to fill with some kind of expanding foam - anybody done this?

Thanks for all your help so far - great forum!