drhill wrote:The moment of inertia of those HSS sections will give you an idea of the relative strength and stiffness.
1x2x0.083 wall the moment of inertia is 0.2379 in^4
1x2x0.120 wall it is 0.3214 in^4
2x3x0.83 wall it is 1.021 in^4
So the 2x3 is more than 3 times the strength and stiffness of the 0.120 wall 1x2
It is your trailer for your use, but if you are going to the trouble of building, it costs little more to make it a couple feet longer. Even when I was tent camping I kept finding the list of gear growing all the time. So what you think might be big enough, may be too small after a few trips. Also - you might want to rent or borrow the smallest trailer you can find for an hour or two and find out how painful it can be to have to back up a short trailer. Longer is so much easier.
And just in case you wanted to know.
2x2x0.083 has a moment of inertia of 0.3905 in^4 and
2x2x0.120 wall it is 0.5337 in^4
So the 2x3x.083 would be lighter than 2x2x.120 wall but almost twice as strong in the vertical direction.
I was able to plug in some numbers (not that I understand what I'm looking at) and came up with 1.467 in^4 for .120 2X3 which is about 40% more strength than .083 2X4 at approximately 30% weight gain. Ideally I think .083 2X3 works best for my situation but because I am building it I want to err on the side of caution. I'll bite 40 lbs. on this build but if I do another in the future for off road the frame will be 2' longer and the tongue will sit beneath the cargo frame. The temptation to enlarge the frame is prevented by my desire to keep the towing weight of the trailer loaded at around 1000 lbs and which will limit me to about 550 lbs of cargo. I do have 14" just ahead of the cargo box and storage on the lid so i think i'm gonna have to learn to live with this and use the experience i gain for another project. As for backing up... that is going to be a lesson for me also... i drove a ton of farm equipment as a kid but that was then and this is now...