incressing draw weight

[raymond]

hello  board  i am building  a all bamboo deflex reflex  bow i am at tillering  stage and all is well but my draw weight is quite a bit less than i want bow length is 6 ft
how many pounds can i gain by shortening  the bow any one have ideas on this  bow string  i plant  to use is adjustable  so am flexible i need to add at lest 20lb to the draw weight,  this design is based on the yumi 

[Pat B]

Raymond, a Yumi bow has a horizontal multi-lam core of wood similar to maple. The strength is in the design and materials used. Using only bamboo it might be difficult to reach the weight you desire. This is just a guess though.
  On a wood bow I think you can increase the weight by 2# to 3# per inch you pike off the length. I don't know if an all boo Yumi would be the same.