Paul,
I want to replicate the plans of the Marauder as much as possible. I really like the low look of it, and I am looking for a high speed bike, which it should be. That is a very long bike, so the strength of the frame is important. I am sure a 2x4 would hold, but it is as heavy as a battleship, to use your words
My running plan for now is to have 2 sheets of high quality birch ply of 9 mm (3/8") thick, with a 4 cm (1,5") hardfoam core, finished with glasfiber and epoxy. I don't think I need a chassisbeam of 4" if I use the ply and hardfoam, but 1,5" as by the original plans is to narrow for sure. I am now thinking of 2,75" height, but I can not back it up with any calculations since I do not have that knowledge.
However, I am looking at a lot of different plans of wooden recumbents, aspecially for the fixings of the wheels, BB, steering etc. I have read some info about trail etc, but since I use the measurements of the Marauder, that should be ok. I will send you a PM for the plans.
Why wood? I like working with it. I like the sawdust. My hobby is making wooden toys. My workshop is filled with woodworking tools. I can not weld, although I am sure I can learn. And, I just want to try. Maybe I will fail, but I will learn from it.
Bob