Hi Uncle Fester, I am currently building an "A" liner type of trailer and like you found there is very little info about home built ones.
My trailer is built from a box type trailer that I use to cart around my large model aircraft, which is 3.6m x 1.7m and 1.2m high I wanted something that I could camp in and still carry model planes and after building several models of the trailer in foam is was the "A" Liner type I chose.
The tricky bits of the design are.
1: How to lift the roof, I used 2 gas struts on each roof section
2: Hinging the side walls, these hinges have to be off set at the bottom to allow the roof sections to fold down completely., also because of the geometry of the triangle walls and the roof the bottom corners of the walls (the last 300mm) are hinged separately and are closed up when the walls are up (bit hard to explain!!).
3: Sealing the roof when set up, I decided to simply overhang the roof sections at the top by about 150mm (6 inches) to try and keep the rain out.
My trailer is not quiet finished, I have to make the door, add the foam insulation and fit lights etc.
The current weight is 560kg which will go up to about 700kg when finished.
Have attached some pics hope this helps.
Cheers, Kev.
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