MickinOz wrote:...I made damned sure very bit of timber I put in was screwed, glued, nailed, and/or stapled into contributing to the structure.
Some even suggested I was perhaps over doing it a teensy bit.
She's a battleship.
BUT, I do not like the flex in my chassis.
I've done a bit of research, and I am of the opinion that the drawbar is just that little bit too long, I swear I can see some harmonics developing...
The other thing I did wrong: I painted with oil based enamel paint. The forum, and other places, is awash with suggestions that these don't flex enough for protecting live wood.
But Hey, I know better!
....
* I also made sure that mine was structurally solid, using steel hardware and bolts to secure all panels, with a double-dose of PL adhesive between all interfaces, then as seam-sealer on the inside & outside of every joint (no structural panel was screwed together). All panels were 3/4" plywood (with additional 1/2" x 3" oak boards as inner bracing around doors, windows, & the A/C in the rear wall. More PL adhesive, plus some Spax screws held them in place. My cabin is so solid, that it's probably the heaviest 4x8 around.
* The frame I started with was smaller and lighter than even a Harbor Freight trailer, but it was elongated and firmed-up with 1.5" x 2.5" rectangular tubing, and the original tongue was replaced with a 6' long, .188" thick piece of 3" square tube, connected to three crossmembers, and with a sistered spine running full length...no flex afterwards. Only 42" of the tongue projects forward from the front wall, and I wish it had been about 18" longer, after the fact. In addition, when upgrading the axle later, to a 3500 lb unit, I used 30 inches of 1/4" thick 2" angle, and 3/16" thick plate to box in the original frame, for the new suspension. Solid like a rock.
* I find nothing wrong with oil-based enamel paint; that's what my trailer is primarily covered with, Tractor Supply Co. (Valspar) Tractor and Implement Enamel (in Massey-Ferguson Grey). It also contains urethane and alkyd. resins, with added to its' long-lasting durability (10 years, so far, since painting). The roof, front slope, and hatch exterior (and the interior) were coated with nearly as durable TSC (Valspar) Heavy-Duty Aluminum paint, also an oil-based enamel? with alkyd. resins, but without the urethane. It reflects heat well, but needed retouching a few years back.
* The reason they've lasted so well without cracking or peeling is the fact that they adhered perfectly to the plywood, which was fully-coated with several layers of the famous polyurethane/paint thinner "mix". I used pre-sanded ACX plywood, and didn't sand between any coats of poly or paint. The poly coats were left to dry for a week before the paint went on, and all coats were done in very hot weather, in direct sun (so they shouldn't have been so good, as the conditions were completely wrong for application). I store my trailer in a garage, so that has helped the durability, but I never expected the paint to last so long (back-up plan to overcoat it with Monstaliner or Durabak wasn't needed).
* I fully expected to move on from this trailer, and build a second one, but didn't need to, nor want to, and just modified it to suit my needs as I went... cheaper, too.