Re-painting the coach roof

[AleCiotti]

Hi guys, due to water infiltrating where the coach roof and the teak deck attach, I will have to open a big portion of the coach roof up and also of the teak deck to remove the rotten wood..

After that I will have to re-paint the surface, my boat coach roof coat is of
white polyurethane paint, I never applied it and I have no idea on how to proceed

should I sand all the old paint first? should I use a primer (I guess so)?
is there a specific way it should be applied?

Thanks in advance, I'll link some photos of the boat for reference.

 

[veshengro]

I'll leave the painting bit to the experts, but just say that all the wood under the old paint on cabin top and sides needs to be exposed and dried, thoroughly dried, before you put any primer or paint on it, otherwise you will be wasting your time.

My neighbour painted his ply foredeck last summer and round the fittings, cleats etc: where the damp was in the wood the paint has lifted already.

 

[AleCiotti]

I'll leave the painting bit to the experts, but just say that all the wood under the old paint on cabin top and sides needs to be exposed and dried, thoroughly dried, before you put any primer or paint on it, otherwise you will be wasting your time.

My neighbour painted his ply foredeck last summer and round the fittings, cleats etc: where the damp was in the wood the paint has lifted already.

agreed, i will be staying in a shipyard where there are workers whom I can ask for help, so I will probably leave the painting to them.

as for the wood I was thinking of removing the rotten one, putting a layer of thickened epoxy on the bottom and sides of the hole created, replace the rotten wood with mahogany marine plywood (the current one).

on top of that I don't really know if I have to put anything else or if we can go straight to priming and painting?

Thanks

 

[veshengro]

If your boat is in a yard and the wood can dry out in the sun or even under cover it will be a good start to repairs.
I've never done major work on a wooden boat, and looking on Google/You Tube isn't my style, so hopefully someone on the Forum with proper knowledge will be able to help. Good luck with the repair.

 

[rogerthebodger]

Once you have stripped all the rotted wood and paint and the wood is dry, I would start with epoxy penetrating primer with several coats until the epoxy stops soaking in,

Once dry sand to roughen the surface and replaced the wood paint with epoxy primer several coats, fill and sand smooth the topcoat with polyurethane topcoat

This is how I finished the replacement wheelhouse top of my previous boat

 

[AleCiotti]

I was thinking of doing basically that!

thanks for confirming, I'm looking to use West system's resin (105) + hardener (206) for the first coats after removing the rotted wood, so it can soak well, and after on top of that I'll put some filled epoxy (105 + 206 + 406) and on top of that the marine plywood coated freshly coated with epoxy, put some weight on top of it and let it dry, sand, and paint.

Am I missing something or should I be good with doing that?
Thanks

 

[Tranona]

Is this still for a temporary repair until you get it done properly? If so it is OTT to slather all that epoxy in it. You need to strip it back and find out exactly how it was constructed and replicate that if the repair is to be good and permanent. It is not clear how the cabin is constructed and how it is bonded to the deck, but I would guess that the actual cabin is moulded veneer or ply sheathed in epoxy glass cloth, filled and faired then painted with (probably) a 2 pot paint such as Awlgrip. The black sealant is to cover the junction between the teak and the coachroof and that has failed letting water in and spreading under the teak as well as into the coachroof.

You really are not going to know how best to repair it until you strip it back and found out exactly what is underneath the paint and the teak covering.

 

[William_H]

I have used polyurethane paint on my GRP cabin top with plus and minuses. I did not use a primer. No real problems there. I just brushed on the PU paint so finish is not beautiful. But a vast improvement on original that has been repaired and filled in many places. I touch up the PU paint easily every winter so can keep it tidy if not brilliant. You may need to add non skid grit to paint in places on cabin top as PU paint will fill in the molded in non skid.
However this is all for GRP boat. It is not clear to me if you have GRP or wooden boat. I suspect PU paint on wood would be a prolem with movement and perhaps wood deterioration as PU is very hard. Not flexible. But really no idea. ol'will