Ever shotblasted fibreglass?

[Pete.]

I'm thinking of using some kind of grit to strip old paint off of a fibreglass bodyshell. Been getting mixed opinions about it, some say it'll be fine with low pressure and fine grit, others saying it will ruin the gel coat.

Has anyone here got any actual experience of stripping paint off fibreglass without stripping the gelcoat?

 

[rtbcomp]

I've certainly shifted filler using grit, so I would avoid it on something you want to keep.

 

[malcolm]

There's not a lot of difference between gel coat and paint in terms of ease of removal. Both are fairly soft and not very resistant to grit. If it's thick paint might be good for getting the worst off without exposing the gel coat to give a more friendly means a chance.

My friend with the glassfibre car used acetone to remove his paint. Worked in a similar way to paint stripper, but didn't damage the gel coat. He was worried that paint stripper would get in to the gel coat and cause trouble with repainting.

 

[Pete.]

Yeah you don't want to put nitromors onto fibreglass. I never thought of acetone but this paint has been on there a looooong time - the newest stuff was applied 20 yrs ago. My idea was really to strip-off the old paint and also provide a key for new stuff. I have visions of problems from years of ingrained dirt on the thing. This is what it looks like right now:

 

[109party]

ive used nitromores on glassfibre n gelcoat frequently u just gotta be quick have everything u need there so put it on, leave for litterlly a few secs,, till it bubbles then scrape,, then immediatly pressurewash, do it on a piece of scrap first so u get a idea of how long 2 leave it 4

 

[tux]

I have no actual experience of this, but TBH any kind of blasting on GRP sounds iffy to me. I can't see how you could avoid at least some damage.

If it were me, I'd break out the DA. Not a pleasant task, but it is tried, tested and time honoured.

 

[pedrobedro]

I'd just primer that and see what happens then barrier coat if anything comes up.

 

[danelectro]

DONT GO THERE!!!

Honestly, if you do it even with low pressure you'll end up with a pile of dust, and a lot of glass fibres!!!

Where I used to work we had a commercial sandblasting bay, some prune tried to blast the paint of of a motorcycle fairing.......needless to say he didn't have one afterwards!!

I think I would spend the time with a DA sander and some 80 grit to get the worst off, then obviously finer as you go. It takes time, but you'll get the right results.

 

[Shox Dr]

Would Bicarbonate of Soda work on something like this. Or the Foam Balls

 

[Coo]

I think I'd get a decent barrier coat to seal that up, then paint over...

 

[Pete.]

I think I'll scrap that idea. Too much potential for going very badly wrong

 

[gaz_moose]

i used to do smaller stuff in the blast cabinet it had quite a fine grit in it tho.you had to move pretty quick as to not leave craters.

 

[Debs.]

My experience is with composite aircraft structures, but I surely wouldn`t blast or chemical strip the car body.
My choice would be: (by hand) wash/degrease with scotchbrite pads, smooth/flat the gel coat with wet`n dry, prime, scratch-fill, smooth/flat (again), re-prime, scratch-fill and smooth/flat (once again) then base-coat/s and top-coat/s......the finish would be well-worth all the effort.

 

[hotrodder]

Walnut shells? Aparently won't damage the gel coat. The marine industry might throw up some other suitable blasting media too

 

[Shox Dr]

Would Bicarbonate of Soda work on something like this. Or the Foam Balls

Walnut shells? Aparently won't damage the gel coat. The marine industry might throw up some other suitable blasting media too

As I pointed out earlier there are plenty of different media these days the two I mentioned are used in the removal/restoration of Paint from Plaster moldings and wood woodwork in Listed Buildings

 

[MrFluffy]

Im in the flat it over rough and barcoat it camp...
Barcoat is truly horrible to look at (its some sort of gone off yellow diseased looking gloop) but Ive never had a reaction to subsequent coats and Ive painted over previously waxed finishes with a just a key in sanding...

This is the stuff :-
http://www.trevordunn.co.uk/shop/index.php?act=viewProd&productId=58

On a similar note, my old grp car was suffering starcrazing, and the best solution the painters could come up with was to heavily vee the worst cracks and stopper them, then coat it with a thick primer coat before isolating it.