WB there is a guy on youtube, from Europe that uses parallel fibres from woven fibreglass cloth. He combs the transverse fibres out, then lays the long fibres in a bed of epoxy, backing and bellying the bow. Its very much like sinewing a bow's back, in that the glass will conform to the cambered back of a tree stave.
Not primitive but should increase the draw by at least 20lbs. You could try one course on the back and belly, see how much the bow gains and how it shoots. You could repeat the process again if you need more draw weight.
