Painting a GRP cruiser
Q I am in the process of sanding down a 48-yearold Elysian centre cockpit cruiser ready for painting. She has had many coats of paint applied by previous owners, some I fear not applied well.
So my question is, even though I am sanding hard I do not feel I will get all the other paint off. Is there any form of primer that would sort of fill in small cracks, or should I just give it a couple of coats of primer and see how it looks before the final coats? Is there a good primer? A
TONY REPLIES: If the existing coats of paint stay firmly adhering during the sanding I am sure they will cause no problems when over-painted. If the cracks are in the paint films it may be better to use a paint stripper that is compatible with GRP and take the whole lot off but you can get what are known as high build primers that may fill the cracks, especially if you apply a couple of coats locally to the cracks and then sand most of it off again. However you will need to discuss this with whoever supplies the paint to ensure compatibility. I would suggest that you discuss this with International Paints (Akzo Nobel) and Hempel, both suppliers of marine coatings.
If the cracks are in the gel coat then you need to be aware that they would allow water ingress into the layup and may cause delamination and resin breakdown (osmosis). In that case I would rake them out and fill with an epoxy marine filler and then sand back. Be aware that normal car type polyester body filler tends to be porous although it should be fine under coats of paint and it is what we used on the GRP cruisers in the hire fleet.
Elysians have an exceptionally thick layup so will accept far more osmosis etc. than most modern cruisers.