Painting the "back" of molded fiberglass parts

[Rachel]

I've got a semi-boat related question here:

I have a molded fiberglass part to paint. This isn't a boat though, but a molded part. I don't want to paint the gelcoat side, but the "back" side. It looks like it was made in cheapish production fashion, with some kind of matt/chopper-gun method, as the surface is a bit "strandy" and not all that smooth. Kind of like the back of a molded shower stall or what I imagine the back of a "liner boat" liner to look like. Definitely not the woven roving I'm used to on boats.

I'm wondering if I have any special preparation concerns (beyond cleaning). I'm planning to use bilgekote, because I think it'd be a difficult surface to sand well, and I know it likes to stick. Perhaps a rough-up with a 3M pad?

I'm reasoning that there is no mold-release wax to worry about because the smooth inside-of-the-mold gelcoat is on the other side. But what about any sort of wax used to inhibit air so polyester resin can cure? Or isn't that the way they did "factory" type molded fiberglass.

Thanks for any insights.

Rachel

[bcooke]

How is your bilge project coming?...

[Ceasar Choppy]

I'm wondering if I have any special preparation concerns (beyond cleaning). I'm planning to use bilgekote, because I think it'd be a difficult surface to sand well, and I know it likes to stick. Perhaps a rough-up with a 3M pad?

I'm reasoning that there is no mold-release wax to worry about because the smooth inside-of-the-mold gelcoat is on the other side. But what about any sort of wax used to inhibit air so polyester resin can cure? Or isn't that the way they did "factory" type molded fiberglass.

The reason you aren't seeing any hefty FG in your part is because it isn't a boat. Its a boat part. Yes, the mold release would be on the gelcoated side.

I would treat it like you would any other part of the interior of your boat: prep with a good scrub with a 3M pad and maybe a wipe down with acetone or denatured alcohol.

What "part" is it that you need to paint the underside??

[Rachel]

How is your bilge project coming?...

Hey, there's a designated thread for you to annoy me about that in!

Caesar, it's not on a boat. It's the inside of a "locker" in a small fiberglass camper. The camper is fiberglass on the outside, and also has a gelcoated fiberglass liner. Therefore the insides of the lockers are comprised of the "backs" of both of these pieces. They're a bit dark and strandy, so the owner would like to paint them, but not if it's a massive grinding/prepping exercise. Some 3M pad prep followed by an acetone wipe sounds a lot less messy and labor-intensive. I just wasn't sure how to treat glass constructed this way as compared to what I'm used to, and thought it was worth a check.

I wasn't as much surprised by the "non-boat" quality level as I was mentioning it just to give information. The construction would be laughable if judged by boat standards, but seems to have worked well for its intended purpose.

Thanks for the input (not you, Britton, but Caesar ;)

R.

[bcooke]

Hey, there's a designated thread for you to annoy me about that in!

I did. You didn't respond. So I found you here.

Thanks for the input (not you, Britton, but Caesar ;)

Ouch :-)

[Summersdawn]

I would bet that they used an air inhibitor wax during layup. I would solvent wipe accordingly. Even if they didn't who knows what has come into contact with the inside of the locker since it was built.