Paint Surface CHecking

[CCBB]

Hi folks,

I thought if anyone in the world knows how to deal with checking in painted plywood you all wouldd with the history of ply boatbuilding and repairing.

This checking in fairly pervasive, increasingly so each season, in the garboard of my sailing dinghy. It is clearly linked to flexing of the surface mechanical and perhaps ply movement. (I first noticed the checking at the position of the garboard where I sit...flexing the surface outward apparently). It is paint over primer over plywood filled with epoxy fairing compound to fill the grain.

The paint is checking and revealing some primer and now wood.

My question is whether the best way is the obvious way: to sand it all down to wood, reseal, prime and paint those checked areas, then paint the whole boat with a coat or two of fresh paint to blend it all? Or are there some tricks?

Clint

[PAR]

Some species, such as Douglas fir and Meranti are well known for surface checking. Meranti can be stopped completely with a thin sheathing of cloth, set in epoxy. Douglas fir needs a thicker sheathing and there's no guarantee it will stop the checking.

If the surface just has a few coats of epoxy, then is painted, there isn't sufficient reinforcement in the epoxy to prevent the checks. Meranti very often will stop checking with just an epoxy coating, though usually you'll have to apply a thickened layer to hide the blemishes.

There are other species that do this as well, but since you're an American Clint, I figured the two common species here would be what you're attempting to cope with.

Without the cloth, you'll continuously chase down surface checks. There is one product that I know that will permit the surface checks, but still stay attached. This is truck bed liner. This stuff is a two or three part polyurethane that will absorb the movement under it and stay stuck. It will not hide the newly formed checks, but it will stretch to keep them covered. It goes on thick (at least 30 mils) so it's heavy, but it does work very well. Color choices and gloss retention are limited, but custom colors can be mixed by most manufactures. Some of the formulations can be over coated, others not so much. This fairly new breed of polyurethane is over taking the industrial coatings industry. It has a very long life span, which recoups it's high initial cost and it's durability is unmatched. It's just not very shiny.