topcoat for bright epoxy finish?

[Chuckles]

I am at a loss and need some advise.

Many of you may have read about the problems I had with Varthane spar urethane over RAKA epoxy on my hatch (see post on "varnish epoxy compatibility problem")... It did not cure properly and had to be scrubbed and sanded off. What a Mess!! Well I have two new coats of epoxy on the hatch and by weeks end the entire camper should receive the last epoxy cote. This time I am in no hurry to get the topcoat on. In fact I might wait until next summer unless I can score time in a heated shop this winter.

After my experience with the Spar Urethane I did some more research and I really don't know where to go from here. Despite using UV stable epoxy I want to topcoat it with another clear finish for increased UV protection. Here are the options as I see it:


Spar Urethane (oil or water based) --- These are relatively inexpensive ($30 - $50 per gallon). As I understand it these are basically a UV stable polyurethane and don't share much in common with the traditional spar varnish. The problem with poly is that it is not very repairable. Also, my first experience with the stuff was less than satisfactory Others seem to have had better luck with them though.


Hardware store spar varnish --- relatively inexpensive at $40 or $50 per gallon. From what I have read on the wooden boat sites they are absolute garbage or only slightly less durable than the stuff that costs twice as much. As I looked into it many brands are dropping like flies. Sherwin Williams-gone, Benjamin Moore-gone. Every time I read about one that performed well I find it's no longer in production. Apparently they are being dropped in favor of the aforementioned Spar Urethanes.


Specialty Marine Spar Varnish --- Again going to the wooden boat sites these are either the best thing since sliced bread or a complete waste of money. And at $120 to $150 per gallon you gotta think twice! Now I assume they are the best you can get but I'm not building a salt-water sailing rig that has to withstand the Caribbean sun 365 days a year... we are talking a camper that will be out two or three weeks a year and garaged in the interim. The benefit of real spar varnish (cheap or expensive) seems to be that it is forgiving and repairable.


Automotive clear coat --- This was suggested by one of the paint store franchises that no longer makes a spar varnish. I know nothing of automotive finishes and have no way of applying them.


My camper has about 610 square feet of surface to cover. Most of the brushable finishes say they will cover approximately 400 square feet per gallon. That's 4.5 gallons for three cotes. I don't know if my budget can handle the high end marine varnish, Is there a good inexpensive varnish out there? If appropriate, what would an automotive finish cost?

Your experiences and advise would be greatly appreciated

[grantstew8]

My plan is to use a few layers of epoxy resin with a few areas with glass and then sand it through the fine grit ranges and then use a polishing paste to get a shine.

I'm watching the replies to your post with interest. I'm about 2 months building away from this important decision.

Thanks for asking.

[Juneaudave]

I can give you some insights based on my experience....others experience may differ ...

My cedar strip trailer has seen 5 seasons now in a pretty challenging rainforest environment. The top and hatch are glassed, the sides are epoxy only (no glass), and the whole thing is sprayed with autoclear.

The top and hatch, with autoclear over glass, still looks very good. No failures at all. I think the glass provides a solid base for the autoclear. A good wash and wax would make it look like new.


The sides that have autoclear over epoxy, but no glass, have not faired as well. I think the slight expanison/contraction movement of the individual strips has created micro-cracks in the the autoclear and epoxy...just enough so to let just a tiny amount of moisture between strips. No serious failure, but I can tell, and it really needs a complete sanding and refinishing on the sides to restore the smoothness.


On the tongue box (autoclear over glass), I have had spot failures where water got into the end grain and the glass pulled away from ash trim....Interesting enough, the glass did not pull away from the cedar strips in general. I think the cedar just sucks the epoxy up better than the ash. Anyway, I've already cut out the bad spots and made epoxy repairs.


So I have a two stage varnish plan. Under stage one, I will completely sand the sides to bare wood to restore the smoothness where there isn't glass, and rough up the roof and hatch where the autoclear/fiberglass is performing well. I am then planning on using McCloskey Man O' War ( a relatively inexpensive marine spar varnish appr. $60-$70/gallon) for the initial coats over the box and sides to build a base...but will leave the roughed up roof and hatch till stage two.

For stage two, I am thinking that I will be spraying a couple coats of Schooner gold ($45/qt) for the final finish over the entire trailer. I've found Schooner to be extremely durable and it retains it good looks much longer than cheaper spars... the Schooner's is trickier to use as it does require mixing with either a brushing thinner or a spraying thinner, but I don't have any doubts that the the Schooner's will stick just fine on both the Man O War and the roughed up autoclear. I think the key is to make sure the Mon O War is completely cured... and if I go with spar sides, I will need to put spar over the autoclear just to make it look correct. The problem is that the autoclear is clear and the varnish is amber.

The other option would be to glass the sides and spray with autoclear again, but I am hoping the softer varnish will help with the differential movement and I can maintain it in smaller chunks. We will see.

[Chuckles]

My plan is to use a few layers of epoxy resin with a few areas with glass and then sand it through the fine grit ranges and then use a polishing paste to get a shine.

I'm watching the replies to your post with interest. I'm about 2 months building away from this important decision.

Thanks for asking.

Before you go with only epoxy for a topcoat you should check with the epoxy manufacturer. To my understanding most epoxy needs a topcoat for UV protection. I used RAKA epoxy with UV inhibitors and they still recommend a topcoat for UV protection.

I have glass and epoxy on everything but the flat plywood roof. I'm actually now thinking of going with a white or silver enamel on the flat part of the roof for less heat gain and, of course, the solid color paints offer complete UV protection! The top of the camper is about 6'8" from the ground so I can't see it anyways.

I don't have any new pics but here is my trailer on its maiden voyage.

After I finish the epoxy I'm going to start on the cabinets. It also needs fenders and a new door.

[Chuckles]

So I have a two stage varnish plan. Under stage one, I will completely sand the sides to bare wood to restore the smoothness where there isn't glass, and rough up the roof and hatch where the autoclear/fiberglass is performing well. I am then planning on using McCloskey Man O' War ( a relatively inexpensive marine spar varnish appr. $60-$70/gallon) for the initial coats over the box and sides to build a base...but will leave the roughed up roof and hatch till stage two.

For stage two, I am thinking that I will be spraying a couple coats of Schooner gold ($45/qt) for the final finish over the entire trailer. I've found Schooner to be extremely durable and it retains it good looks much longer than cheaper spars... the Schooner's is trickier to use as it does require mixing with either a brushing thinner or a spraying thinner, but I don't have any doubts that the the Schooner's will stick just fine on both the Man O War and the roughed up autoclear. I think the key is to make sure the Mon O War is completely cured... and if I go with spar sides, I will need to put spar over the autoclear just to make it look correct. The problem is that the autoclear is clear and the varnish is amber.

The other option would be to glass the sides and spray with autoclear again, but I am hoping the softer varnish will help with the differential movement and I can maintain it in smaller chunks. We will see.

Thanks Dave. I have glass on everything but the flat part of the roof where it's just epoxy over plywood so I might check out the cost of having it sprayed with auto clear.

I do remember reading on one of the boat building sites that some use the man-o-war varnish to build depth then use a few coats of the expensive stuff as a top coat. These folks are using 8 to 12 coats of varnish then sanding and putting another two coats on every year or two as needed!

[Juneaudave]

I sure can't complaint about auto clear over glass, but it is expensive to gear up to shoot if you don't have a compressor and spray guns. As far as varnish goes, I have been using McCloskey Man o War lately, but another inexpensive marine spar I like is the Dalys Seafin Superspar. I used that on my canoe a couple years back for the first time and thought it had really good ease of application and durability. I think it is pretty common. It might be useful to check the web and see what people are saying about it.