I'm going to build a 5x10 flat bed utility trailer for general hauling, but am planning on leaving the top with the ability to put a 5x10 teardrop in place later on.
Total loaded weight will be at about a 2,000# load limit, with the axle & springs I have. Wondering about 1 1/2" X 3" X 1/8" wall tubing, or 1 1/2" X 4" X 1/8" wall (both would be rectangular sections) for the main frame runs. Planning on 3/16" X 2" angle for the internal cross members. The same end pieces as the main frame for the front & back will be used with mitered corners to seal up the frame.
I know the trailer with a teardrop box bolted in place on the frame is way overkill either way, but I'll be using it to haul stuff in the mean time with just a flat deck & no support for the frame, as a utility trailer once it's finished at first. Axle will be a 60/40 setback so there will be 4' behind & 6' in front with 25" springs splitting the difference on mounts.
Is the 1 1/2" X 3" X 1/8" tube strong enough, or should I go with 1 1/2" X 4" X 1/8" for a 10' long flat deck utility trailer? It will have a standard 50 degree hitch coupler for a 2" ball, with the 2 members running under the front corners & back to the frame sides.
Edit, 4" it is!