I didn't use an epoxy paint, but an epoxy adhesive. For most of these kind of jobs, I use West System Epoxy, which is popular epoxy adhesive from the boating world.
http://www.westsystem.com/ss/
However, it takes almost 12~24 hours to completely cure, which makes it stronger as it penetrates the wood more. Epoxy is almost always used in boats for this kind of repair. It's just what I am comfortable with using.
Epoxy is used not only as a glue, but also used with fiberglass or carbon fiber mat to make high-strength/light weight fiberglass. Cheaper boats (and RV's) as well as most "fiberglass" products use a Polyester resin to infuse the fiberglass, while high end boats (such as Hinckley) and other high-value components use epoxy resin. Circuit boards for example is fiberglass mat bonded by epoxy.
For sure, I could have used polyester resin, but epoxy is a higher performance resin and the cost differential is nil for small quantity. Now, if I were fiberglass laminating a 30ft boat, it would take 55 gallon drums of epoxy, at a huge expense.
Unfortunately, West System epoxy does not work very well on vertical surfaces, as the cure time is too long and it tends to run down the side.
So for this job, I used Locktite Heavy Duty epoxy in the 8oz size, which is a general purpose 5 minute epoxy I picked up at my local Menards (regional hardware store like Lowes and Home Depot).
I did not need the penetrating adhesive properties of the West System stuff as this is not a structural repair, but I needed the quick dry stuff to keep it running down the vertical surfaces.
Yes, epoxy comes in two parts; a resin and a hardener. Most epoxy formulations - such as the Locktite stuff I used are mixed equally, but West epoxy for instance is mixed about 3:1 resin to hardener.
No need to thin the epoxy. Thinning it makes it more prone to running on vertical surfaces. It is kind of like painting molasses though. The short 5 minute tack time means it will more or less stay put on a vertical surface.
I use epoxy for all of these kind of things; it is a lot more useful than just a glue. Epoxy is essentially a plastic.
For this application, it is better than spar varnish due to it's adhesive properties which will re-laminate the damaged areas. Also, all you need to apply is one coat. As it chemically cures you can button up the project a lot faster as well. It will still out-gas for awhile though.
The only downside of epoxy is it is not UV tolerant, so if the epoxy will be exposed, it needs to be painted, varnished, or you need to use a UV inhibitor additive. Not an issue here though as it will not be exposed to the sun.
I do also have some CPES, which is a penetrating epoxy that I have left over - again, from boating. I never needed to use it, so it is still new. This epoxy is very thin, and takes about 3 days to dry, so it flows a significant distance through the wood before curing.
http://www.rotdoctor.com/
It's main purpose is to repair delaminated transoms that have been water damaged. You basically pour it into the top of the delaminated area, and hopefully it will flow down into the wood and fill the delaminated areas, rotted areas, and so on.
It is an effective (sometimes) solution when the value of the boat is not sufficient for a traditional repair.
I should use that stuff for protecting the holes that were drilled into the back side for the mounting of the bezel. However, I am going to try to infuse some silicone grease in the holes, and hopefully that will be enough.
This project got me to thinking though. All of the exposed screws on the RV, whether they were used for fastening the ladder, any of the compartment hatches; basically everything that is attached, were simply drilled into the sides without any underlying protection.
Again in a boat, you would typically "bed" these screws by using a sealant, which will prevent water damage under the screw heads. And I am talking about the upper surfaces, such as bow rails, cleats, etc.
When the fastener is under compression like that, water will wick into it and can damage any underlying lamination. I really don't see a big difference between a RV and boat in this regard.
However, I thought with Thor, they used aluminum tubing for the construction, so why I found plywood in this area is a mystery to me. I think though, that it might just be localized to the tail light area, perhaps to beef up the area for the tail lights.
I know they do that for areas such as the dining table; where it fastens to the wall - there is a piece of plywood backing in the wall.
At any rate, I am going to take a closer look at the other fasteners on the RV.
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