Moulding for perimeter of large teardrop

[KCStudly]

I think the point being missed is that wood doesn't have a lot of tensile strength parallel to the grain. If the wood is stressed parallel to the grain (i.e. bent), or if there are joints (such as splices and corners) then the internal strain, jostling going down the road, or even just expansion/contraction from temperature can cause the wood fibers to move enough to break the barrier of the coating (cracks) which results in water intrusion, which is the beginning of the end.

By adding a fibrous material that has strands running in various directions across the grain and across joints, then these stresses between the wood fibers and relative motion at joints are bridged and supported by the tensile strength of the fibers.

If you want to avoid checking in your wood and breaks in your protective finish, some sort of fibrous (or stretchy) membrane is desired. The stretchy ones tend to break down from weather and UV over time, and are more susceptible to impact/puncture damage, so the fibrous versions rein supreme, at least in my eye.

Using fiberglass reinforced epoxy, FRP/Filon, canvas and binder, even paper/poster board and glue before paint are all viable options that in my mind are better than just primer and paint over standard plywood. (Line forms to the rear to debate this.)

Using WBP (water and boil proof) marine grade plywood is also a good start.

[Fyddler]

I assume CPES first would still be important?

[KCStudly]

CPES - I don't see how it can hurt (except in the wallet), but there are lots here who feel that it is unnecessary and prefer to just us regular epoxy; the argument being that if you are using epoxy it is best to use glass weave, too, so anything before that is a waste. Still others have had good results with less expensive options under paint, like thinned wood glue, straight wood glue or "The Mix" (50/50 polyurethane and thinner).

I am building with WBP marine ply and foam, and am still undecided on the final covering. If I stick to the original plan and do canvas I will wash the underside and edges of my floor with thinned TB2 before a light sanding and coating with either tar or canvas and paint. The rest will be canvas and paint... unless I change my mind and go with glass weave and epoxy all over. Most of my surfaces to be covered are foam, so it is a different situation than what you are facing.

[Fyddler]

Thanks for all the great info!

[Irving]

That is great info. Thank you. Are you suggesting that if I decide to go with tightbond 2, canvas, primer and paint - I should still use CPES underneath of it all?

[KCStudly]

Are you suggesting that if I decide to go with tightbond 2, canvas, primer and paint - I should still use CPES underneath of it all?

No, I am not suggesting that. I haven't used it. I don't think that it is a bad product, and plenty of people have used it and feel that it is a great.

I guess I am just adding to the confusion. I have read the forums extensively and I am trying to share what I have gleaned from experienced builders that appear to have first hand experience, and lots of it.

For example, Doug Hodder (who is obviously a master craftsman and has built several truly masterful campers) has stated many times that he feels that CPES is a waste of money IF you plan to use glass and epoxy over it. He prefers straight
epoxy because he always has it on hand because he uses it as glue, filler, and sealer coating, and it cost about half what CPES cost with better coverage.

GPW, on the foamie forum has lots of experience with "experimental" techniques and materials used throughout the RC airplane hobby (light weight and strong are key concepts here) and, combined with his RV and trailer experience, his artist/painter background gives him a unique insight into coatings and canvas. He is a champion of "thrifty" alternatives and many people have had success using "The Mix" as an inexpensive alternative penetrating sealer. Just be careful to test and make sure that your thinner ratio doesn't dissolve the glue in your ply (some claim that the cheap sheet goods at box stores have different glues these days and they don't like solvents). Some people use a similar blend but cut the spirit ratio down to 40 or even 30/ct.

Mostly I'm looking at my own build method (hybrid foamie) and materials (foam, cedar and marine ply) and I do not plan to use CPES. I'm well invested into my project, and if money were no object I would probably use CPES, too, but I feel that the investment that I have made in the base materials and the use of one of these other proven methods will provide very good long lasting results.

Your mileage may vary.

[doug hodder]

That is great info. Thank you. Are you suggesting that if I decide to go with tightbond 2, canvas, primer and paint - I should still use CPES underneath of it all?

Thanks for the kind words KC...but I just get lucky. Danny is the master craftsman!

Irving...don't use CPES or an epoxy under a canvas and titebond 2 canvas skin. I don't believe that the titebond will want to bond to the CPES like it should. Doug

[Irving]

That is great info. Thank you. Are you suggesting that if I decide to go with tightbond 2, canvas, primer and paint - I should still use CPES underneath of it all?

Thanks for the kind words KC...but I just get lucky. Danny is the master craftsman!

Irving...don't use CPES or an epoxy under a canvas and titebond 2 canvas skin. I don't believe that the titebond will want to bond to the CPES like it should. Doug

Good to hear. Thanks.