Wall thickness

[sitnfat]

Working on plans to build a teardrop. Originally I had planned on 1 1/2 thick walls out of two pieces of 3/4 plywood. But after looking through this forum seems most folks don't do this. Any reason other than weight?

[MtnDon]

I'll counter that with... why would you use two solid layers of 3/4 plywood? IF you want a thick wall it would be better to frame a wall with "sticks" and infill the spaces with foam insulation, then skin over with thinner plywood. IMO.

[sitnfat]

I'm not the best wood worker in the world. Seems using two sheets would be simpler and faster.

[steve cowan]

2 sheets of 3/4" would be faster but why? It will only add weight that is not necessary.Some use 1 sheet of good quality 1/2" with good results.Remember you're
not building a tank.


This is built with 3/4".

[les45]

The side walls on my weekender are 3/4" plywood sanded and painted. Top and end walls are 1/4" plywood over 1X2 spars with foam insulation between spars.

[yrock87]

I'm not the best wood worker in the world. Seems using two sheets would be simpler and faster.

using one sheet would be even faster and cheaper (and lighter)

my build is 1/8ply, 1inch foam, 1/8 ply but if I were to build again and I was not concerned about insulation, I will be going high quality 1/2 inch ply. maaaaaybe 5/8s. the ply is MUCH stronger than you think once it is boxed.

[jonesnforcampin]

We planned our camper to be removable from the trailer & it hangs over the trailer 6" in front and 18" in back, so I wanted it extra rigid. We went with 3/4" & 1/2" glued and screwed together. If I had it to do over again I would probably do max of 1" total.

We also ran some of our wiring in between the two sheets. We routered out channels in the 1/2" to lay the wires prior to gluing and screwing.

I tend to over build though. Hoping it's not too heavy for the TV (not quite done yet).

If your camper is not removable and fully supported by the trailer I would go with a framed and insulated wall set up with thinner skins inside & out. Weight & cost are big factors I'm thinking of. Wonder what the insulation efficiency is comparing 1-1/2" thick plywood vs framed & insulated with 1/4" or 1/8" skins...?

Oh, and some others have posted about how strong the plywood actually is; to add to that, my Dad found me some 1/2 that we used for the roof and it looked like there was some plastic mesh in there too. Even after I broke a strip of cut off over my knee it still didn't go into to pieces. There was some fabric of some sort in there. Amazing stuff.

[yrock87]

according to google, plywood is R value of about 1.25 per inch, so a 1.5 inch ply wall would be about R 1.8. the XPS I used was an R of 5, plus 1/4 in of ply (1/8 on each side) gives us a nominal R 5.3.

my cabin will be temporarily permanently installed. it is more than strong enough to take on and off, in fact I just moved it across town on the trailer and then took it back off to finish work without the tires and tongue getting in the way. I don't plan on ever taking it off for any particular purpose, but I hate not having options, so it will be removable with a few bolts if needed. It really is amazing how strong these things are when you combine them together into a box frame. you take bend board and foam, and glue it together with some 1x1 framing (which also bends quite a bit) and you end up with a surprisingly stiff panel, then you box it together with 6 sides (and a curve or two) and you end up with an amazing stiff box. I guess that cardboard is the same principle. a little corrugated cardboard that is folded into a box and then taped is suddenly strong enough to stand on (on the corners if empty) or carry 50-80+ lbs.

[KCStudly]

The trick is to separate the outer fibers and support them rigidly with out adding weight. Whether you feel the need for the insulation value or not (noise suppression, heat/cool/moisture barrier) the extruded foam board is ideally suited for separating thin plywood since it provides a broad gluing surface and is very resistant to compression when loads are dispersed (...by the plywood).

...and it is wrong to think about whether the trailer can stiffen the cabin. The cabin is such a deeper section than the trailer frame that once the box is unitized (i.e. the bulkheads are in and the roof goes on) it will be the cabin stiffening the trailer, not the other way around.

TPCE is 5 mm inner skin laminated to 1-1/2 XPS with minimal 2x2 cedar frame work and two (2) plies of 6oz epoxy/FG cloth outer skin. It is as rigid as H-E-double hockey sticks! Unitize your construction and all of the smaller light weight pieces will add strength to the assembly, not weigh it down.

Before adding the outer skin, with the inner skin fully finished and with the door (no window or hardware) my 9ft 8in long x 49-1/2 in tall walls weight 45 lbs each; i could lift and move them myself quite easily, but the were already very stiff at that point. A 3/4 inch thk piece of 4x8 fir ply weighs 44 lbs and is really quite floppy by comparison.

Build airplanes not tanks. Build your trailer and your cabin light, that way there is less load for the structure to have to deal with.

If you want your walls to be thicker than 3/4 inch, I say go foamie! ... or at least do a traditional stick frame and foam wall with 5mm (3/16 inch) underlay ply skins.

[yrock87]

The trick is to separate the outer fibers and support them rigidly with out adding weight. Whether you feel the need for the insulation value or not (noise suppression, heat/cool/moisture barrier) the extruded foam board is ideally suited for separating thin plywood since it provides a broad gluing surface and is very resistant to compression when loads are dispersed (...by the plywood).

...and it is wrong to think about whether the trailer can stiffen the cabin. The cabin is such a deeper section than the trailer frame that once the box is unitized (i.e. the bulkheads are in and the roof goes on) it will be the cabin stiffening the trailer, not the other way around.

TPCE is 5 mm inner skin laminated to 1-1/2 XPS with minimal 2x2 cedar frame work and two (2) plies of 6oz epoxy/FG cloth outer skin. It is as rigid as H-E-double hockey sticks! Unitize your construction and all of the smaller light weight pieces will add strength to the assembly, not weigh it down.

Before adding the outer skin, with the inner skin fully finished and with the door (no window or hardware) my 9ft 8in long x 49-1/2 in tall walls weight 45 lbs each; i could lift and move them myself quite easily, but the were already very stiff at that point. A 3/4 inch thk piece of 4x8 fir ply weighs 44 lbs and is really quite floppy by comparison.

Build airplanes not tanks. Build your trailer and your cabin light, that way there is less load for the structure to have to deal with.

If you want your walls to be thicker than 3/4 inch, I say go foamie! ... or at least do a traditional stick frame and foam wall with 5mm (3/16 inch) underlay ply skins.

agree on the built panels being stiffer than ply. my 3mm(1/8 ply), 1in foam, 3mmply wall sections 4ft hight by 10ft long) were incredibly stiff as well, also less than 50 lbs and I could also easily move them by myself. They were so stiff that my passenger side wall (which I inadvertently cut the bottom not quite straight in a concave shape) actually pulled the 1 inch floor up to the wall when I screwed it together. now that the roof is no, pound the wall or roof with your fist and the whole trailer thuds like a tight drum, almost zero flex.


Not saying that you shouldn't build 1-1/2 inch ply walls if that is what you want, but don't do it for stiffness, especially if you are concerned about weight and your TV being able to pull it.

I like the airplane analogy. heck, even a boat is a good analogy. light equals fast. what we are not building are tractors...

[jonesnforcampin]

according to google, plywood is R value of about 1.25 per inch, so a 1.5 inch ply wall would be about R 1.8. the XPS I used was an R of 5, plus 1/4 in of ply (1/8 on each side) gives us a nominal R 5.3.

my cabin will be temporarily permanently installed. it is more than strong enough to take on and off, in fact I just moved it across town on the trailer and then took it back off to finish work without the tires and tongue getting in the way. I don't plan on ever taking it off for any particular purpose, but I hate not having options, so it will be removable with a few bolts if needed. It really is amazing how strong these things are when you combine them together into a box frame. you take bend board and foam, and glue it together with some 1x1 framing (which also bends quite a bit) and you end up with a surprisingly stiff panel, then you box it together with 6 sides (and a curve or two) and you end up with an amazing stiff box. I guess that cardboard is the same principle. a little corrugated cardboard that is folded into a box and then taped is suddenly strong enough to stand on (on the corners if empty) or carry 50-80+ lbs.

Yup, I have a problem of over building stuff.

One thing I do have to say in support of my over built camper and thick plywood walls is I won't have a problem attaching anything anywhere I want. I have seen other builds that look great and will work great, but every attachment point has to be planned for on the walls. With this being my first build and trying to plan for a growing family I have no idea what will and won't work and what I will need to change during the build and after. As a matter of fact the bunk for the kids has changed three times and we haven't even finished the camper. I don't have to worry about where I'm going to attach it to the walls though.

[dwgriff1]

Take a hollow core door. Put it between two sawhorses and you can sit on it without it breaking, and the whole thing is very light weight.

I made a whole pile of "hollow core doors" shaped as necessary and I textured and painted the panels on the inside before assembly (I am basically lazy). I framed the walls with 3/4 framing with foam in the core (which makes it stronger).

The one downside is that it is relatively easy to punch holes in that thin skin, particularly in the process of backing the trailer. That short wheelbase can be like pushing a cat by the tail.

dave

[yrock87]

Take a hollow core door. Put it between two sawhorses and you can sit on it without it breaking, and the whole thing is very light weight.

I made a whole pile of "hollow core doors" shaped as necessary and I textured and painted the panels on the inside before assembly (I am basically lazy). I framed the walls with 3/4 framing with foam in the core (which makes it stronger).

The one downside is that it is relatively easy to punch holes in that thin skin, particularly in the process of backing the trailer. That short wheelbase can be like pushing a cat by the tail.

dave

I don't push cats at all. especially by the tail... anybody ever read " Harris and Me"? a buddy growing up had a cat named Buddy the Buzzsaw. I never liked cats after that.

[Shadow Catcher]

You are building an airplane not a tank. Our walls are 1.5" but framing is 1.5 X 1" X 0.06 aluminum tubing 1/8' plywood covered with Filon and 1/16" typical RV wall board interior. It is strong enough for me to stand on.

[Tomterrific]

One of the strongest most indestructible off road vehicles is a motorcycle. The dirt bikes weigh less than half of a road bike and the road bike would fall apart the first time it went down. Weight does not mean strong! Design light. Tradition and simplicity says 1/2" walls. I went with 5mm and battens. I used 3/4" for the floor/base but 1/2" would have done as well.

T