Preparing GRP for painting
 

My Marlin bootlid, which is currently just gelcoat has an area with a few hair line cracks. Suggestions please on the best way to treat it before painting.:help:

If the cracks are just in the gelcoat I beleive it is normal to grind back and fill (or apply more gel coat) before painting. If you don't do this the cracks will probably come back through your nice paint job.

I'm no expert though - just what I rememeber from various articles I have read.

Robin

Thanks
Chris

GRP canopies are made of glass reinforced polyester and are used because of their durability, low cost of maintenance and variety of looks. Some canopies are made to look like other, more expensive materials, such as timber-frames or tiles. Repair kits are available to replace worn screws, wall plugs and washers. Tears in GRP canopies are mended using basic fiberglass repair techniques of Custom Web Applications

Re: Cracks in gel coat , grind out the crack and either fill with gell coat or filler , if your going to paint the panel, use a barrier primer first some paints can react to GRP and you will need to flat it back and re fill any low spots it will look far better in the end if you take care with the flatting and filling if spraying its best to remove the panel if you can that way you dont have to deal with overspray

You can grind, sand, then fill or gel,
thats about it!

the best cure ive found for this is a 50/50 mix of filler and fibreglass resin,grind the cracks right back no matter how deep you have to go,then mix your filler and resin together until they have a consistancy like honey,add your hardener and mix in,then,if your panel is level,just pour it into the pit youve created in the panel until its levelish with the surface,then leave to harden,when its gone off youll be left with a very strong repair that will not shrink(as filler alone may),it will not crack like filler may on a surface that flexes,but,you can flat it with 180 with ease

sorry to bear this news .but the only way to repair this properly is to grind out the cracks back to the mat and then re-glass the area. then you can either re-gel or fill to bring back to surface level
you can then prep the whole panel for paint using a course grit ie 120 and prime with 2k hi build primer. anything less than this and i will almost guarantee the cracks reappearing or shrink back. (30 years grp experience)