Teardrop Roof

[jdfdave]

I posted this In the Newbie section, but no replies, so I moved my question over here.

I am to the stage in my build where I need a make a decision about the roof. I skinned the exterior of the roof with 1/4 b/c exterior grade plywood. The entire outside has been waterproofed with CPES.
Now my decision: Can I just paint the roof with a good exterior paint? Should I use something like FRP from Lowes or Home Depot? If I use those how do I attach them to the roof? Contact Cement? Let them float and just attach at the ends and sides?
All Answers are appreciated. I have a lot to learn and am enjoying the process.

[Esteban]

Have you considered fiberglass? Some plywoods can crack, or check, over time. Fir plywood is known to do so. Fiberglass cloth and epoxy would help prevent that. You could paint the fiberglass. Interlux Brightside is a well regarded one part boat paint used for wood and for fiberglass. Rustoleum makes a less expensive boat /marine paint. Rustoleum Marine Topside Paint at Amazon.com Raka.com raka.com is a lower priced supplier of epoxy and fiberglass cloth many people here have used. They have good instructions on their website.

There many good YouTubes about fiberglassing. Many of the best are by canoe and kayak builders. Fiberglassing a Strip Built Kayak and Layout and Smoothing of Glass Cloth and The Basics of Fiberglass Fabric will get you started.

Because you have already sealed the plywood with CPES you may not need very much epoxy. As a rule of thumb you use 1 (liquid) ounce of epoxy for every ounce (weight) per square yard of fiberglass cloth. If you use 4 oz. cloth you need a little over 4 ounces of epoxy per square yard. Or 6 oz. cloth needs a little over 6 ounces of epoxy per yard. If you only need to do the roof you probably don't need all that much epoxy. Once you're done it's seamless and waterproof.

Lance and Becky's build journal is a good one to learn about fiberglassing. Lance and Becky's Sagwagon. Joanne's Desert Dawg Desert Dawg is another good one. Both fiberglassed and painted their teardrops.

Took a quick look at your blog. The seam in your roof and the side edges could be waterproofed well with epoxy and fiberglass cloth. You can then skip installing trim on the edges. If you round (over) sharp corners fiberglass cloth will drape over them better. The roof seam may need several coats of epoxy to soak into the end grain and completely fill up the joint.

[les45]

My outer skin is 1/4" plywood treated with CPES. I glassed my corners with 4" tape and simply painted everything with Rustoleum enamel over two coats of Zinsser oil based primer. It is a year old now and has held up well. You can check my journal for details of my prep work.

[jdfdave]

Thanks for the replies and ideas. The teardrop forum folks are so friendly and have great ideas. I hadn't thought of using fiberglass. I will look into that.

[michaelrsydney]

If you round (over) sharp corners fiberglass cloth will drape over them better. The roof seam may need several coats of epoxy to soak into the end grain and completely fill up the joint.

More to the point if you do not round all the corners the glass cloth will NOT drape and the job will be ruined. Put as big a radius as is practical and you will make the job much easier. Obviously finer cloth will drape more easily than a heavier one. The temperature and humidity have a big effect on the results so choose a warm dry day and don't be tempted to over catalyse the resin. But don't be too worried, it really is very easy to work with and a great solution for weatherproofing timber. It is widely used for the decks of timber boats. Good luck!

[KCStudly]

Also know that people have had problems when using just epoxy and not glass, especially when the ply has been formed over a curve. The stress in the wood fibers can still pop up as cracks and delamination later.

Les49's fine example and good results using just epoxy on the flat panels may not be as successful for you if you have a curved roof.

[doug hodder]

It's kind of a mixed bag of results using CPES. There are a number of builders that have used CPES and exterior paint and have had failures with it, some not. It's the end grain that typically starts to go...some have had larger checks in the ply surface.

Personally, I don't think only 1 coat of CPES is going to do it for you in the long run, and CPES doesn't build like an epoxy will. I build with epoxy, no cloth and have had great results on my builds over some fairly tight curves 18"R, down to 1.5" R on some wood strips that I bent on the tongue box on 1 of them. 6yrs and 5 yrs on the 2 trailers, with no problems. Thing is...you really need to take your time and put on many coats of material to really seal and smooth it out. If you are in a big hurry, I'd go with a layer of cloth on it and a couple of coats of epoxy over that prior to painting. Like mentioned...don't try to lay cloth over a hard 90...it has to be eased and if the tape is cut on the bias, it goes on a lot easier.

The whole CPES vs Epoxy debate has gone on for a long time....Once CPES has been put on...that's it, there is no more penetration that will happen with subsequent coats...it doesn't build up any thickness like an epoxy will for a smooth finish, It also is nastier to work with. Others opinions will certainly vary, to each their own.

Your other options...aluminum, FRP or any skin can be "floated" and captured with the appropriate aluminum cap. Doug

[Esteban]

West Systems Use Guide for Finish Coatings

The function of a finish coating like paint or varnish over an epoxy barrier coat, is to decorate the surface and protect the epoxy from sunlight. In doing so, the finish coating extends the life of the epoxy moisture barrier, which, in turn provides a stable base that extends the life of the finish coating. Together the two form a protective system far more durable than either coating by itself.
Protection from sunlight is a primary consideration in the selection of a finish coating. Long term UV (ultraviolet) protection of the barrier coat depends on how well the finish coating itself resists UV and keeps its pigments, or its shield of UV filters on the surface of the epoxy barrier coat. A high gloss finish reflects a higher proportion of the light hitting the surface than a dull surface. All other thing being equal, a white (especially a glossy white) coating will last the longest.

Most types of coatings are compatible with epoxy. Thoroughly cured epoxy is an almost completely inert hard plastic. This means most paint solvents will not soften, swell or react with it. However, it is still a good idea to build a test panel to assure coating compatibility.

It goes on to discuss qualities of different types of paint.

[jdfdave]

I am glad someone mentioned the FRP I asked about. What is the best method to attach it? Glue entire surface? Attach only at sides or ends to allow it to float?

[jstrubberg]

Just my opinion, but if I did either FRP or aluminum over wood, I would let it float. There is no way that the wood and the outer layer are going to expand and contract at the same rate. If you attach the two, sooner or later either the glue or the wood fibers are going to give as the two move around at different rates.

[jdfdave]

So just attach it at the edges with some sort of trim. Will it buckle going down the road at 60 mph? Just asking, I want to do it the right way.
Thanks

[Steve 70]

I used a vinyl to cover my roof. I have attached the link to the site. Extremely heavy duty. I skinned the roof with 1/4 inch plywood that was sealed with spar urethane. I let the vinyl float and only attached around the edges and around the roof vent. A couple of advantages that sold me was price, width of material,(61 inches, my camper is 5feet wide), and the ease of replacing if it were to be damaged or I would need to repair or replace the 1/4 inch plywood. Also several colors.

http://www.rochfordsupply.com/shop/Text ... _and_Tarps)/index.html

It is in the category of "general laminates 13 Oz"

[nhstt]

My outer skin is 1/4" plywood treated with CPES. I glassed my corners with 4" tape and simply painted everything with Rustoleum enamel over two coats of Zinsser oil based primer. It is a year old now and has held up well. You can check my journal for details of my prep work.

Les,
What brand of CPES did you use and what did you use as a filler
Advice please

Karen at the Ladybug-out build journal viewtopic.php?f=50&t=55602

[rowerwet]

http://m.instructables.com/id/Poor-Mans ... -weatherp/ what I used on my tear.