aggie79 wrote:Take a look at this design for a semi-standy trailer with a 10' body length, 6'-6" body width, 6' body height built on a near stock 4' x 8' HF trailer:
http://tnttt.com/Design_Library/The%20Wanderer%208%20and%2010.htm. It uses the stock HF axle and tires. The floor is 1/2" plywood. The only floor framing is a 1x6 at the front and rear of the floor.
The trailer was designed by Andrew Gibbons. Andrew has designed a plethora of boats, teardrop trailers, tiny travel trailers, motorcycles, etc. Many of his designs have been constructed by TNTTT members. He put together the Excel spreadsheet for axle placement and tongue loading and design.
Now, this is a good conversation we got going here! Thanks to Aggie79, Camp4Life and KCStudly for their thoughtful replies. Wonderful to hear from your expertise.
The issue of load transfer has already been explained by KCStudly and Camp4Life. However, I think it's worth pointing out that although a moment diagram could predict whether or not the teardrop would tip at a certain angular acceleration, it doesn't consider tire wear. Trailer owners, let's face it, habitually run their trailers with underinflated tires, which over-flexes the sidewall leading to heat generation and premature failure. So if you've built a 1,400-lb trailer on a 1,700-lb capacity Harbor Freight trailer, where each tire is rated for about 1,000 pounds, a combination of load transfer and underinflation could easily overwhelm the tire. Is this a catastrophic failure? Eh, maybe not. But maybe not negligible either.
I did check out The Wanderer. Clever design. And I think there's a lot to take away from it, such as the 1x6 floor framing. I did go through the Excel chart, too. Now, I haven't built one, so I can't speak to actual numbers ... but those weight estimates struck me as pretty darn lenient
for general builders. For one thing, the "fit out" estimate of 300 pounds suffices for a barebones model, but one with windows, 12/120-volt electrical system (a battery alone is 50 pounds!), cabinetry hardware, trim, seals, bedding, kitchenware, any plumbing, etc.? That's pushing it, even for a basic model. The chart also assumes a Spartan woody build. As soon as you add aluminum siding, roofing and trim, you're at the chassis weight limit. And some people would feel that his design choices - 1/4-inch sidewall sheathing, 1/2-inch flooring, 1x2 roof spars - were unacceptable structural compromises.
Now, I'm not knocking this guy's one design! He explains very clearly that if you change anything, you better make sure you know what you're doing! So If he built a 6x10 on a 4x8 trailer for 1,400 pounds, then I applaud him and his work. But I don't think it's fair to use his example as cart blanche for everyone else. There's no room for error. You can't build a 6x10 on a 4x8 kit trailer unless you're willing to mimic his design or build another barebones model. The gentleman who began this thread did not seem to have a no-frills build in mind. And I think the Wanderer 10 more-or-less proves that trying to build a 10'-long model is not something to be taken lightly, nor will it work for everybody.
And that's the end of my sermon
Thank you all so much for your contribution! Learned a lot