laminating fiberglass to plastic

[river runner]

This isn't really a boat design question, but I'm having trouble posting on the building section.
I need to patch a boat bottom that is almuinum with a plastic layer over that. Epoxy doesn't stick to plastic very well. After roughing up the plastic, I'm thinking that putting down some sort of adhesive or coating, before the laminating resin and glass, might work. But what would be the best thing to coat the plastic?

[CDK]

Sika primer 206 adheres well to most plastics and also to glass.
There may be a similar product from 3M but I have no data.

[BPGougeon]

What kind of plastic is it? West System GFlex will stick to most plastics with proper surface preperation. Check it out. http://209.20.76.247/ss/g-flex-epoxy/

[PAR]

Bingo, prep is the name of the game here and typically carbonizing (oxidizing some as well) the surface molecules on the plastic is all that's needed, of course after good prep (cleaning, toothing, etc.)

As the next generation of West boys has mentioned, it's helpful to know which plastic you're dealing with, as some need a different approach.

[tunnels]

Originally Posted by river runner

This isn't really a boat design question, but I'm having trouble posting on the building section.
I need to patch a boat bottom that is almuinum with a plastic layer over that. Epoxy doesn't stick to plastic very well. After roughing up the plastic, I'm thinking that putting down some sort of adhesive or coating, before the laminating resin and glass, might work. But what would be the best thing to coat the plastic?

west system make a special epoxy fot that purpose !!chack it out onthere site !!!

[PAR]

There's nothing special about the epoxy you need, any of the major formulations will work with the proper prep. This said, some plastics can or need an epoxy with less elongation properties, which is why I asked which "plastic" you're trying to glue some to.

[river runner]

I have no idea what plast it is. It is for a Hyde drift boat and they have not been helpfull at all. I checked out G-flx at the west system site and this does sound promising. For some reason I'm having trouble with this site and didn't get some of the messages till I'd already ordered some System Three products, which I'm more familiar with. Maybe I can use them on the inside of the hull, which also needs work.

[PAR]

Follow the instructions on the West System site for bonding to plastics, but using your System Three goo. Cut the mixed epoxy with isopropyl alcohol 5% to 7% by volume (yea, I know, I can hear you yelling already). Then oxidize the plastic and apply immediately, while it's warm. Trust me on this one, I don't want to go into the physical properties changes this slight solvent dilution preforms, but it'll make a more resilient bond on the plastic I'm pretty sure you have.