Etch primer on epoxy?

[Brands01]

Is it possible to use an etch primer over epoxy to avoid sanding off the gloss prior to painting? This is in an area of the boat where the finish is not important.

[MikeJohns]

You generally use a chemical agent for this . For example Devoe generally recommend washing the existing epoxy with Devprep 88 prior to re-coating. Then you simply apply an epoxy.
If you have a gloss surface it is most likely some other top coat since epoxies always chalk slightly when used as a top coat.

[Landlubber]

Yes Mike is right, Devprep for instance takes off the waxy chemical residue. It would be pointless trying to make paint stick onto the shiny surface. Epoxy resin is generally not UV inhibited and as such the surface starts to deteriorate rapidly if not protected (as Mike says Chalky). I would still suggest that after using Devprep that you lightly abrade the surface anyhow. Is there a particular reason for not doing so or are you being lazy. If being lazy is the reason, forget it, boatbuilding laziness will come back and bite you again and again. Do it once and do it right!

[Jimbo1490]

Sanding the gloss off ofa large surface can seem a daunting task.

To greatly increase your efficiency when sanding a large surface like the side of a boat hull, it is helpful to use a 'guidecoat' This is a thin coat of a quick drying paint of a contrasting color. Flat black lacquer from spray cans is typically used for this purpose.

What you want to do is just 'overspary' the surface with a dusty, 'barely there' coat of paint applied over the whole surface. Applied this way, just couple of cans of lacquer will cover even a pretty large surface, 10 or 20 times as large as the typical can coverage.

Later when you sand, everywhere you actually touch with sandpaper will change color rather dramatically, clearly showing where you have sanded and where you have not. This will assure every spot gets sanded, but equally importantly, that you don't waste time sanding some areas over and over.

Without a guidecoat, you are left to figure out where you have not yet sanded by looking for glossy areas; a difficult task once everything is covered with sanding dust.

It really does help speed the job up!

Jimbo

[Landlubber]

Yeah Jimbo, that is true, and also Brands 01, there is no such thing as "This is in an area of the boat where the finish is not important.:, I hope you just mean the presentation of the finish, every thing you do MUST be done correctly, there are no short cuts. The "dustcoat" as we call it in Australia, saves a lot more time than it takes, and of course when doing finishes that presentation really is important, it is the only way I know of to really get the surface "flat", as every little dimple shows up because it is covered in black.
I build boats currently in China, we use cheap printers ink on a rag to do the same job, it is "waterproof" so it does not wash off when wet sanding.

Thanks Jimbo for bringing this up, every boatbuilder should use the technique. I also use it for brightwork believe it or not, you can still see the dark sections and the end varnish job is supurb. Id all the brightwork in full gloss, doing satin over this finish if required, that way the satin is very even and flat.

[Brands01]

Thanks for the responses everyone, I'll certainly take those tips on board when the time comes to fair the outside of the boat. I'll elaborate a little bit more, because my original question refers to the inside of my boat.

My boat is timber (so I'm probably posting in the wrong section!), and I've sheathed the outside of the hull and painted the inside with epoxy to stabalise the timber - which seems to have worked very well.

So I'm refering to the inside of the hull when I talk about the area where the finish is unimportant. I want to paint it to keep it looking neat and tidy, but the epoxy is all glossy. The reason I want to avoid sanding is now fairly obvious - all those ribs and stringers and nooks and crannys - much easier to spray something like an etch primer.

Any comments?

[Oyster]

The way I read it you are glassing a planked hull with some age? If so and the boat has some age on it, you maybe asking for some serious trouble down the way. If nothing else, I would leave the epoxy unpainted if you must epoxy coat the planking. This would at least give you some idea if dampness enters the seams and wood down the road. Normally if glass is applied on wooden planked hulls, its done in the initial build because the planks are more stable without the seasonal changess that takes place over time. I strongly reccomend that anyone thats in simular situation reconsider this method of glass or even epoxy on the interior. I would use a good enamel primer at the most, or red lead if you can buy any of that down there now. What thickness is your planking?

I posted comments for others even though I see you have coated the inside with epoxy.