Straightness issues with single ply walls?

[les45]

Still in the planning stages, I am looking at using uninsulated single ply 4X10X3/4" plywood walls on a 5X8 trailer in my Weekender design. My walls will be screwed to 2X4 cleats running the full length of the 8' floor deck and my top will be 5' long 1X2 spars mounted vertically with 1/4" ply roof and 1/8" luan headliner sandwiching 1.5" of foam board insulation.I am seeing some subtle references to straightness issues in some posts, but can't seem to find a post with a lot of info on this subject. Anyone out there have any suggestions, thoughts, issues concerning straightness problems with this type of construction. The galley walls will keep that end fairly straight, but how about the long gap along the bed area? Will I need some sort of vertical reinforcement near the doors?
Thanks,
Larry S.

[absolutsnwbrdr]

I used 3/4" plywood for walls on both of my builds and I haven't had any problems with the walls warping. Depending on where you get your 3/4" ply, it may have some minimal warp/flex over the entire length of the panel, but it will straighten out once you get it on the trailer and get everything screwed/glued together. I used 3/4" 4x10 sheets of MDO plywood on my new build, and they were as flat/straight as could be. For what I paid, I would have been furious if they weren't.

Now regarding the doors: I used the factory-style doors on both my builds so I have zero experience building my own. However, the doors take up such a minimal area in relationship to the entire side wall that any warp that may be around the door opening should be negligible.

[campmaster-k]

My tear is only an 8 footer but I have no warping. Doors are fine.

[jonw]

I used 5/8in marine ply for my walls and have had no problems. Probably 1/2in marine ply would have been fine.

[les45]

I used 3/4" plywood for walls on both of my builds and I haven't had any problems with the walls warping. Depending on where you get your 3/4" ply, it may have some minimal warp/flex over the entire length of the panel, but it will straighten out once you get it on the trailer and get everything screwed/glued together. I used 3/4" 4x10 sheets of MDO plywood on my new build, and they were as flat/straight as could be. For what I paid, I would have been furious if they weren't.

Now regarding the doors: I used the factory-style doors on both my builds so I have zero experience building my own. However, the doors take up such a minimal area in relationship to the entire side wall that any warp that may be around the door opening should be negligible.

I plan to use the manufactured doors also. I'm looking at the 36" tall ones from Vintek. Looks to me like the metal framework of the doors would help stiffen the plywood walls vertically in that area.

[campmaster-k]

I love those doors. My next build will have those cool doors!

[angib]

My walls will be screwed to 2X4 cleats running the full length of the 8' floor deck

Everything else sounds fine - but 2x4 cleats is waay too much, when 1x2 will do fine. You don't need the strength of 3/4 plywood, just its resistance to bending, so you don't need cleats that belong on a house.

[DMcCam]

Hi Larry,
We used 3/4" Crezone plywood for my outer walls. It's a type of sign board used for exterior applications that's hard as nails and absolutely flat. The CNC router used up a 1/2" bit cutting them but that stuff is beautiful. I'm making a sandwich wall with an outer and inner layer of Baltic Birch plywood. We cut a 1/4" mortise in the bottom edge of the 3/4" as a support lip for mounting it to the deck then added the 1/8" birch for a total of 3/8" edge. As we were gluing and screwing the walls to the deck they were so strong they flattened a 1/4" dip in the 1 1/8" deck.
I agree that 2" x 4" cleats are way too much. Here's a link for you to check out ways to attach your walls to the deck: http://www.tnttt.com/viewtopic.php?f=21&t=19442

Have Fun,

Dave