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[BlueWotsit]

Restoring an old GRP hull, it was suggested I use Brushing Primer as used in the Auto Trade - this appeared to do the trick fine and smoothed back nicely and filled minor gremlins

I then applied Halfords Acrylic car spray paint over the primer a couple of days later.

Left it to dry 24 hours and started light sanding it ready for the next coat, and it lifted / cracked apart very easily in places but not everywhere.

Was this a compatibility problem, first coat of paint on too thick or something else do you think ? - I was using 600 grade wet and dry to sand it

As a possible solution I was thinking about painting GRP resin over the hull and sanding smooth then start painting again - will acrylic go onto resin and should a primer (normal) be used.

thanks

[Shipmate60]

Did you rub all the old paint off, back to gell coat?
It is usually best to use all the paint/primer from one manufacturer which should ensure compatability, but still read the instructions as Halfords still sell celulose based primer and red lead.

Bob

[ukengineman]

Halfords do two primers in the Acrylic spray paint range. One is for plastic materials (which would be the appropriate one) and one for metals. I suggest you sand off the existing finish and start again using the Halfords acrylic primer.
Alan

[BlueWotsit]

It turns out the primer was cellulose based, so I guess this was the problem ? The instructions on the can were useless in Italian only !!!

Rather than take the primer coat back to base, Im going to get hopefully on this occasion some cellulose based paint and use that

Anything I should look out for ?

[Shipmate60]

Just try a small area and leave for a few days, try rubbing that down and see how it "sticks"
If not out with the wet and dry and take it all off, which is my preffered option.

Bob

[Stavros]

seriously m8 I would either go down the route of a complete sand down and start again which would give the best result in the long run,or get an isolating primer.I know this is available in the car trade but I do not know if it is available in aerosol form.If you go to any good car paint factors such as Brown brothers or Partco tehy will advise you.Don't bother asking in Halfords,as most of the idiots who work there don't know the difference between a ball joint sand a track rod end!!!!!

[BlueWotsit]

cheers Guys, watch this space as they say......

Dont start me on Halfords..... I went in to get a bit of car striping tape, which I like to use when masking delicate areas.......the guy looked at me as if I had just arrived from another planet, totally clueless and that was the easy question I asked him   

[BlueWotsit]

The plot thickens... literally

Talking to a fellow club member he said he uses the cellulose brushing primer all the time with Halfords acrylics and hasnt had the reaction mine had

Looked closer at the Halfords tin and it clearly states compatible with most paint mixtures including celluloses

Im wondering now if it could have been caused by some form of chemical reaction left as a result of the previous owner, religiously polishing the hull with that Space Age all singing and dancing UV protection polish that you buy for cars, its all I can think of

Meantime Im taking paintwork right back to bare hull

[Colin Bishop]

UV protection polish frequently contains silicone. If so then no paint will stick to it so that may well be the problem. I think it can be removed with acetone but you are probably wise taking it back to the bare hull.

[Stavros]

DO NOT DO NOT USE ACETONE TO GET RID OF ANY POLISH,it will attack any paint that is on the hull.The PROPER way to get rid of any silicone products on any surface prior to painting is too use a PANEL WIPE available from good paint motor factors,this is the only product that will successfully get rid of it,hte product can also be usedfor degreasing prior to painting,please listen to a PROFESSIONAL paint sprayer

[Colin Bishop]

Thanks for that Stavros. Do you know what the magic ingredient is in panel wipe? The reason I ask is that it is common practice to polish full size GRP boats with silicone based polishes to keep the hulls slick and discourage staining and marine growth. Eventually, due to oxidisation it becomes necessary to paint the hull which is then pretty much impregnated with silicone which is a **** to remove!

[Stavros]

Wish I new m8 as I could then bottle it up and drink it !!!!!!!

[BlueWotsit]

Am I right in thinking that this wipe, is like a paint to apply, followed by primer then the top coats ?

[Stavros]

No M8 all you do with this wonderfull product is as the old chappie siad in the Karate kid film wipe on wipe off thta is all you do.Clean cloth x2 one for applying the other for taking off simple as chips!!!

[BlueWotsit]

thanks for that