Teardrops n Tiny Travel Trailers

Not sure if this is the right place for this question, but this is where I was when I thought of it. I am just going to leave my td with the wood on the outside. I've gotten some good ideas from this thread about how to waterproof and finish. My question is this, do I need to skin it with another piece of wood, like an 1/8th inch luan. Or can I just put my waterproofing and finish on my 3/4 or 1/2 inch plywood that I use for my side walls?

Hartse25 wrote:... do I need to skin it with another piece of wood, like an 1/8th inch luan. Or can I just put my waterproofing and finish on my 3/4 or 1/2 inch plywood that I use for my side walls?

If I understand the question correctly, you are building a traditional wooden TD with plywood side walls. You do not plan to use aluminum outer skin and will more than likely paint your wood (as apposed to a clear coat woody).

You don't mention if you plan to have a stick frame on the inside, or insulation, but you should plan on having some sort of additional reinforcing around the door opening and door skin (even 3/4 ply can warp in time and could effect the door seal)... unless you are using pre-made doors.

From the many traditional build threads that I have studied I don't think there is any need to add an outer skin. (My preference would be to stick build and use thinner inner and outer plywood skins, but that is based on my climate and planned camping locations/seasons.)

Most of the time the thin outer skin is only done if the thicker plywood core has been "skeletonized" to receive foam insulation, or when stick building to reduce weight. I suppose somebody might do it to be able to use a thinner piece of a finer grade wood and reduce the cost of building a woody by using a lower grade of plywood for the core, but I'm not sure the logic of that holds much weight in a cost vs. quality analysis.

With plywood construction the most important thing is to be sure to seal the edges very well. Fill any voids and soak them until there are no more pores or crevices.

Thanks. I do plan on having insulation and a stick frame between 2 layers of plywood. I am planning on using it mostly in the Midwest in the summer. Is 1/2 think enough or do I need to use 3/4?

If it were me, I would use 1x2 sticks (either on edge with 1-1/2 thick insulation... (some people feel this is excessive)... or "in the flat" with 3/4 inch insulation... (more common)... and only 1/4 inch or 5 mm (3/16 inch) ply inner and outer skins, fully glued.

Pay attention to your door and window thickness requirements and how you plan to trim these out. It's okay to just build up a spacer ring around these openings, rather than feel the need to make the whole wall thicker if you don't want to.

Unless you plan on dragging it through really rough conditions with lots of potential for damage from rocks and branches, even 1/2 inch ply is overkill/extra weight, IMO.

Maybe 1/2 inch for the floor if you don't plan on putting insulation or a bottom skin on underneath. My floor is 5 mm top and bottom on 1-1/2 inch foam with 1x2 and 2x2 cedar frame... I have been walking and kneeling on it since the front wall went up and I had to remove the waster piece of ply I had used for temporary protection. It's doing fine. Remember, once the mattress goes down all loads will be distributed.

Hope it's ok if I post this here...

I understand the mix and will be using it liberally when I start building. My question is when I put plywood down on the trailer for the floor of my foamie, I would coat the underside of the plywood with black goo roofing stuff? And this special mix everywhere else? Or do builders now put the mix everywhere and forgo the black goo?

Techniques/products seem to change so quick that it's hard to keep up!

I have been underwhelmed by the need to use undercoat unless you drive in rain & snow all the time.

When I purchased my used trailer, it had been in light use for 4 years but parked outdoors for the entire period. The top layer of untreated plywood has checking but the underside is close to new in appearance. You can see the trailer angle iron positions in the pic below.



My guess is that most folks could just use the mix on both sides as directed and call it good.

I'm not going to use the black stuff. I sealed the underside of my floor with a thinned coat of TB2 followed by a full strength coat (or maybe two?). After the canvas is wrapped under the edges I will paint the same as the top coat.

I'm not crazy about putting coat after coat of the mix ad nauseam. I'll do a couple of 50/50 coats, then, if I have some left I'll thicken it to 25/75. Once it's gone, if I feel I need more protection I'll either do full strength or rough it up a little for whatever product comes next; sometimes adhesive, sometimes paint. My preferred method is to glue first then seal because you get stronger bond to raw wood.

I have a couple questions regarding this "mix". If I use this on the edges of my plywood should I also use a CPES type product or is the mix enough?
And second, if I use this mix on wood before skinning is there been any issue with adhesives like PL premium or even TB finding traction on the sealed surfaces?
Thanks

I have a couple questions regarding this "mix". If I use this on the edges of my plywood should I also use a CPES type product or is the mix enough?
And second, if I use this mix on wood before skinning is there been any issue with adhesives like PL premium or even TB finding traction on the sealed surfaces?
Thanks

We actually like applying "the mix" to wood in several coats, only because we’ve been doing this for decades and it WORKS !!! The PROPERLY Thinned mix , 75% Mineral Spirits , and 25% Polyurethane varnish .. is just the right consistency to really sink in DEEP into the wood ... Other thicker preparations only linger near the surface and ultimately do Not completely protect the wood over time ...
CPES might work , ( Big Mike will tell you ) but is an Expensive alternative ... and some have suffered CPES failures despite their optimistic claims ... We however have never had a piece of wood treated with the Mix to fail ... (rot) .

Note: I did NOT invent the Mix , It was developed by Chuck Felton ( the aircraft guy) to waterproof common cardboard for plane construction ... I have merely used this to waterproof everything wooden that will be used outdoors , and since the early 80’s, all without failure.


Those who use the Mix differently than advised may not have the same successful results !!!

GPW wrote:We actually like applying "the mix" to wood in several coats, only because we’ve been doing this for decades and it WORKS !!! The PROPERLY Thinned mix , 75% Mineral Spirits , and 25% Polyurethane varnish .. is just the right consistency to really sink in DEEP into the wood ... Other thicker preparations only linger near the surface and ultimately do Not completely protect the wood over time ...

So I guess your saying as long as I use a thinned mix the surface will be able to accept an adhesive for skinning walls?

And second, if I use this mix on wood before skinning is there been any issue with adhesives like PL premium or even TB finding traction on the sealed surfaces?

TBII glue, applied to bare wood and clamped, is stronger than the wood. The wood will fail before the glue line fails. (Of course this doesn't apply to butt joined pieces).

I don't believe you'll get anything that approaches that with wood that has been sealed with the mix and then sanded to give it tooth. I think it's similar with PL Premium (and I use a lot of it but have not tested it on poly'd wood). You just can't beat the fact that adhesives are taken into bare wood with capillary action and clamp pressure.

Join your wood. (Fit, glue, and clamp –or screw) Then apply the mix. It'll soak into any voids in your joint and aid in the adhesion. Polyurethane finish is a fairly decent glue.

Tony

p.s. PL Premium uses moisture in the wood to cure.

Well now , there’s a big difference between water proofing the wood and skinning the wood ... Apples and oranges... Tony’s right eh !!! "You just can't beat the fact that adhesives are taken into bare wood with capillary action and clamp pressure. “ ...
It is possible to glue plywood to foam with T2 and then do the other side in the mix .... Once the T2 is dry/cured , the mix won’t affect it . Much like we’d do with chipboard ...

tony.latham wrote:

And second, if I use this mix on wood before skinning is there been any issue with adhesives like PL premium or even TB finding traction on the sealed surfaces?

TBII glue, applied to bare wood and clamped, is stronger than the wood. The wood will fail before the glue line fails. (Of course this doesn't apply to butt joined pieces).

I don't believe you'll get anything that approaches that with wood that has been sealed with the mix and then sanded to give it tooth. I think it's similar with PL Premium (and I use a lot of it but have not tested it on poly'd wood). You just can't beat the fact that adhesives are taken into bare wood with capillary action and clamp pressure.

Join your wood. (Fit, glue, and clamp –or screw) Then apply the mix. It'll soak into any voids in your joint and aid in the adhesion. Polyurethane finish is a fairly decent glue.

Tony

p.s. PL Premium uses moisture in the wood to cure.

Perfect. That's what I needed to know. Thanks all.

I think I got the 'mix' down, and using multiple coats and even extra on the ends. Using oil based poly instead of water based. My question: with multiple coats, does one allow the coats to dry in between coats? I wouldn't imagine having to sand in between coats either. Oh, btw, you'll see more of my questions as we go. Another newbie here and I"ve decided to do the foamie route with my first teardrop build. I'll introduce myself later in the appropriate folder. Hi from Virginia and Semper Fi folks!