: Any other fellow woodworkers had any futon building experiences to share?
Yes. Designed and built one for my then-girlfriend (now SWMBO) in college. She used it for a couple of years in college, it was our sofa for a while in an apartment, and now (with new mattress) it serves as a guest bed. Ten plus years and no problems yet.
Mine is not what I'd call fine furniture, but it was nicer than what the futon stores were pushing. Instead of legs & a frame, it uses three crosswise members about 10" tall, with lengthwise slats. The crosswise members are each in 2 pieces which overlap, pivoting around simple bolts. To hold the back upright, large diameter dowels are inserted into holes. On my then-college-student budget, this was built with (carefully chosen) 2x lumber - the cross members are 2x10's and the slats 2x3's, planed down a bit, and then sanded and rounded over. Considering that, it's held up well - no significant twist/warp/check problems and it still looks OK.
The good: - Rock solid & sturdy. - Was quick to build. - Folds up & down easily. - No special hardware.
The problems: - I got the back angle wrong - it's a little too upright to be really comfortable in 'sofa' mode. This would be easy to fix. - When in 'sofa' mode the futon mattress has a tendency to slide down & off. We used to work around this by running a long piece of nylon webbing around it to "tie" it to the frame, but that wasn't a great solution. I would imagine this to be a problem with other designs as well. - It's a bit low to the floor. Fine for sleeping, not great for sofa-ing.
As you can see, all the problems are with the sofa aspect. As a platform bed it works great.
If you're interested in more details send me email. I can take pics of the design, and I even still have the plans.
-Brett