Fiberglass panels - any advice for prep & paint ?

[nomad]

Does anyone have any advice or links on how to prepare & paint old fiberglas?
I have a couple of large panels in unpainted original gelcoat that are unused/never fitted but have been in storage for many years.
There's no obvious damage, fitting isn't a problem for me but I'd be grateful for any advice on how to get a good key for the paint.
Getting paint to stick is the main aim, I can live with some ripples/marks as it's not going to be a permanent addition 
I've found 1 great post on here (thanks PhoenixCapri !) but I'll happily take any other links or tips


As thanks, I give you...

Vokaro priceofhistoys.com/2008/09/18/super-fun-vokaro/vokaro-kit-car-1/


Brubaker Box retrorides.proboards.com/thread/131416/cool?page=2&scrollTo=2034570


Bangert (& an interesting site ) blog.hemmings.com/index.php/tag/rick-dlouhy/

[Maxxxer]

When I did the work on my flip front I started with a drilled, cracked front piece which needed a fair bit of filling to get how I wanted it (see the build on www.mgexp.com/member/maxxxer#registry )

Keying the surface is reasonably easy - although has it's obviously softer than sanding metalwork so you do need to be careful not to sand too hard.
Crazing in the gel coat is a PITA, but if you take your time and sand over gradually with a low grit it shouldn't be too tough to sort.

The hardest part for me was the sanding of the new fibreglass sections I added to fill the various holes; I think I may have overdone it on the hardener as it was a sod to sand smooth.

I felt it was easier than working with metal to be honest, and if you do make a mess you can always fix it with more fibreglass..!

Paint wise I approached it the same as normal spraying (although to be fair my Midget doesn't have the best paint in the world so I wasn't too worried about the final finish; if it was curse word I could always re-spray).

One thing I do wish I has used is high build primer to resolve some of the visible issues where I had clearly filled the holes; there's still an obvious difference in the fibreglass.

The only other thing is - what are you painting? If its likely to move a lot (as my flip front does when opening and closing) you'll need something that can take the movement; my paint is starting to crack in some places. As such give the car a once over with a Plastidip type stuff as is likely to be more flexible (and also reasonably cheap compared to a full re-spray).

Oh, and I also really enjoyed getting stuck in - never done anything with fibreglass before, so it was something entirely new for me.

[docjohn]

I did the old and new bonnets by dry sanding with 400 grit, then put high build two pack primer on with a mini gloss roller, resanded and then just used cellulose as normal. The 2 pack primer stops the cellulose thinners from eating into the resin coat or any filler and sinking. You've got to dry sand as wet sanding lets water into the fibre-resin interfaces which seeps out over time to create blisters - sometimes its called osmosis.