KTM_Guy wrote:Plywood doesn't expand and contract like solid wood or metal. It can swell if not sealed well.
* As
KTM Guy stated, plywood that has been sealed (
sealed well) doesn't absorb or lose moisture content, thus doesn't warp or swell.
* I used 3/4" plywood (with phenolic resin-bonded plies) all around, and for the galley shelf, and also used 1/2" and 3/4" oak dimensional lumber pieces inside the cabin for shelving, door, A/C, and window framing. I used up to 6 coats of polyurethane "mix" (with several extra applications to the edges, to be sure of saturation), then pure poly, and finally, acrylic enamel to seal the wood outside, and one coat of acrylic inside. All seams were joined and protected by using PL Premium adhesive, as well as all drilled holes thru the skin sealed with PL, also.
* But, 3/4" plywood can add up to become rather heavy. My "little" 4x8 squareback TTT weighs in at around 2100 lbs travel-ready (weight fluctuates from trp-to-trip, as changes are made everytime). I'm sure that it is extremely overweight due to overkill in the items carried on-board (generator, A/C, redundant supplies, etc.), extra bracing of all structural members, as well as extra steel reinforcement of the basic frame (rolling weight was 400 lbs, before adding framerail braces, much beefier suspension components, and larger/heavier tires). That's just the way I roll...make everything stronger (and heavier, alas) than necessary, but inline with my belief that more is better ?!?
* I'm also sure that prudent use of the heavier 3/4" plywood will strengthen your build, but keep a running weight log, lest your trailer might grow much heavier than initially intended, as mine did. I had planned to use my '09 Chevy HHR Panel to tow it (tow weight max = 1000 lbs), but when my weight log showed it to be heavier than that, with all "needed" items installed, I decided to add more, and tow with my '04 Chevy 2500HD pickup (w/beefed-up suspension & transmission, capable of towing 12k lbs). Initial weighing at the local scale showed it to be 1280 lbs, empty. With travelling gear added, 1438 lbs on my first camp-out! Many alterations in the 6 years since then, have made it grow to 2100 lbs today. Beware!