Wall Construction

[travist]

Hi All,

So I've seen a gazillion wall construction threads, and tried to avoid writing my own, but I'm building a standy, that will probably sit on a 7'x14' frame with a galley kitchen/hatch in the back. It will probably stand 7.5' tall. Meant to sleep my family of 4, with a possible guest (ie a friend of my kids), and provide a seating area (that becomes a bed).

All that to say, I'm a classic over-builder, but one of the things I like about building a trailer is that I can build it as strong as I want, and I know from seeing around me that factory trailers these days always seem to be cutting corners.

Ok, so enough intro.

I've been thinking about doing the following. Skin (pmf or other, undecided), Solid plywood, hard foam, thin wood veneer. My plan was to attach all structural components to the solid ply, then block in the foam and skin after, or at least leave space for all the structural components (beds etc).

So for my questions. How thick plywood should I do? I was thinking 3/4", but wondering if I need that much strength, will 1/2" work just as well? I know often cabinets are built out of 1/2" and hold up a lot of weight.

Also, if you think this wall construction plan is crazy, let me know if you think that another alternative is much better. Not sure I want to do the skeleton thing, but I could maybe be convinced.

[Wolfgang92025]

Hi Travist,

Welcome to the fun.
Sounds like you are building a pretty good sized trailer.
I used 1/4" on the outside, wooden frame with 3/4" insulation (that"s all I could find in So Cal @ the time) and 1/8" skin on the inside.
My body is 12' long and 5' tall and is still holding strong after 8 years bouncing down all kinds of roads and trails.
If I was to build today, at most I would only use 1/8" on both sides. Use quality materials and glues with stainless hardware when you can.
Also, think aircraft, not a tank.

[Tomterrific]

I agree. The 3/4 inch ply will not be that strong of wall only heavy. It is the joint that gives the wall strength as the joint is the first failure.

Tt

[travist]

Can you clarify why you say it won't be that strong?

Also, what would you suggest for wall construction? 1/2" solid? or skeleton?

[noseoil]

A skeleton with skins is what you want. A stick-framed conventional house is built this way, so why not a trailer? The "studs" only serve to keep the skins apart & provide strength from the down-forces. How many houses do you see with solid wood walls?

[coyote]

My 4X8 tear is 1/2 ply. 4 yr's,@ 4000 miles each summer, no problems. My Scotty is 5 X 10, also 1/2 ply. That's factory from 1965. I took it completely down for rebuild 3 yrs. ago. At 50 years it was still working well, except for expected water damage. I rebuilt new walls out of new 1/2 inch. (Lumber yard ply. was MUCH better than big box store) 3000 miles this year, no prob. Coyote

[2bits]

If you are building a standy then basically you are building a vintage trailer like a '60s Shasta or a Scotty and I would suggest looking into those tried and true construction styles. For example cabinets are stick built with 1/8" yes 1/8" face frames and undersides, not 1/4" and certainly not 1/2" . You're not throwing a tow chain up there,just some plastic forks and tin cans in the pantry. Check out camper wall construction and it will blow your mind what had lasted 50 years. on stick built campers 1x2's were held together with staples and many times the wood wouldn't even touch. I personally use ripped 1x2s and pocket holes and a stick build frame. As Mr. Coyote mentioned, Scottys were built with solid 1/2" ply walls and have lasted the test of time. 2x4s and 3/4" plywood is best left for homes. If you miniaturize the scale of a house why would you not miniaturize the building materials as well. Kind of the same concept as a scale model plane. just because you build it smaller doesn't mean it is weaker. I hope that helps.

[travist]

Thanks for all your input everyone. I do like the unibody of the plywood cut out skeleton if I went that direction. Sounds like I can at least go down to 0.5" ply solid if I wanted to. Lots to think about. I'm still in the drawing stage, I'm using AutoDesk Inventor so I can get a full weight and center of gravity sense of the trailer, then play with things like skeletons or changing plywood things etc. This will all give me a direction to consider.

[Staryder61]

There really is no right or wrong answer...IMHO.. many different ways have worked for people, it comes down to a matter of preference in the end..
Some use solid plywood. Some use the stick building method, insulate and skin both sides,
I used the skeleton, insulated and skinning both sides. It cut down on the pieces I had to cut, the joints and pocket screws it entailed.. plus my work space was limited at the time..

[lacofdfireman]

Maybe I’m wrong but it seems like it would be so much more money to make a skeleton frame then sheet it both sides when you could just do a 1/2” wall and be done. Sure it’s lighter to make a skeleton frame but if your side profile is 4x8 you’d end up having to buy a sheet of 1/2” to make your skeleton frame then 2 more sheets to skin it where you could have just bought 1 sheet of 1/2” and been done?


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[Ottsville]

Maybe I’m wrong but it seems like it would be so much more money to make a skeleton frame then sheet it both sides when you could just do a 1/2” wall and be done. Sure it’s lighter to make a skeleton frame but if your side profile is 4x8 you’d end up having to buy a sheet of 1/2” to make your skeleton frame then 2 more sheets to skin it where you could have just bought 1 sheet of 1/2” and been done?

You don't have to use a sheet of plywood for the skeleton, you could use boards, or even cut your "boards" out of ply. Are you insulating this build? Will this build need to support a RTT like your first one?

[Staryder61]

The skeleton or stick build is used for the use of insulation, which helps with heating, cooling and to prevent condensation.. more so than just structural.. and in my case, it also gave me a place to help run some wiring out of sight..

[lacofdfireman]

Maybe I’m wrong but it seems like it would be so much more money to make a skeleton frame then sheet it both sides when you could just do a 1/2” wall and be done. Sure it’s lighter to make a skeleton frame but if your side profile is 4x8 you’d end up having to buy a sheet of 1/2” to make your skeleton frame then 2 more sheets to skin it where you could have just bought 1 sheet of 1/2” and been done?

You don't have to use a sheet of plywood for the skeleton, you could use boards, or even cut your "boards" out of ply. Are you insulating this build? Will this build need to support a RTT like your first one?

Yes my current build will be built to support a RTT on top. This is why I’m thinking 1/2-3/4” side walls?




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[lacofdfireman]

Also I figured if I used a solid sheet of 1/2-3/4” that would be plenty of insulation?


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[travist]

What's RTT?

I also wonder at the weight savings of skeleton and then having to add 1/8" skins on both sides.... that almost seems like zero weight savings.