Thanks for the replies they made me want to look more into it.

the question is theoretical. just imagine tillering a 12' 2x4 with hand tools

I really had to get an answer so i did an experiment.

I used a metal ruler instead of boards

below are the pictures of the set up and the data(if you can understand anything)

The results: doubling length will make the spring 8-9 times weaker, of course there are errors in the experiment but it seems that it follows a cube pattern like thickness does (but weakening instead of strengthening).

so 2x width 2x thickness 2x length =2x8x1/8=2x strong.

but we also have 2x draw length so it goes 2x draw weight (from hooke's law) but this is a big assumption to make.

i guess the resulting F-D curve would be more aggressive 200# @ 56" (100# @ 28") rather than 100# @ 56"

it would store 8x the energy of the normal bow (about time to double the arrow

)

I thought that someone would have made a miniature bow and scale it up to man sized, the same principles would apply here.