Plug Preparation With Pic Question

General Composites Discussions Composites Talk
#1

Hey guys,
While I wait for vacuum parts to come in, I figured I would make my next mold in the mean time.

I was wondering what would be the best way to prevent the paint/clear coat from coming off when I make the mold? 5 coats of mold release wax and 3 coats of pva? Last thing I want is for the paint to be ruined in case the mold goes wrong. I’m not sure what type of paint was used on it since it came with my bike.

Also, I’m bad with figuring out how much gelcoat I need to cover this part. Anyone can shoot a guesstimate? Most of the time, I barely have enough for my mold or I use too much.

Thanks all for the help

#2

The tactic that I used to prevent paint from coming off a plug is to spray on the PVA as per the instructions. I spray about 6-9 layers with 15 mins between coats. That way I have a pva layer that can be pulled off when I demold. It is a nice barrier that separates the paint from the gelcoat and resin.

It’s hard to tell an approximation of gelcoat needed without an idea of how large the part is. Put it next to something: a soda can, a ruler, etc.-- that way we have an idea how large the part is, and can give a better estimate.

#3

If you have good paint that’s shiny and smooth, then wax should prevent the paint from coming off. If the paint had a bad bonding surface, and wasn’t cured well, then it could come off. What is that piece? If it’s a car part, I wouldn’t worry about it so long as you wax it 5 coats or so.

#4

When in doubt about styrene resistant paints/clear, switch to epoxy. Pea and wax will not help at all.

#5

It’s actually a solo motorcycle cowl.

Ill get another pic with a soda can or something in the pic for better judgement.

#6

The safest bet is to use PVA. Wax could be fine but it could also fail with polyester or epoxy surface coats. The best thing to do is test the release with a scrap that is painted with your paint system. Then you can test your release system and your resin to make sure it’s all compatible. Some epoxies will chemically bond with the paint even if it’s waxed. Wax is unable to block chemical reactivity. Properly applied PVA blocks any chemical reactivity. Either way… TEST! TEST! TEST!

Calculating the amount of gel-coat is simple. Surface area x gel coat thickness + 15 percent. You can always mix up more gel-coat and apply it right away if you are running short.

#7

Thanks for the extra input. Sadly I don’t have an extra part. I’m not sure if the previous owner purchased it prepainted or had it painted,

As for the amount of gel coat, I’ve got about 16 oz left and was wondering if I needed to purchase more.

Here’s another pic if it helps…