I have made a couple deer rawhide strings. Used a round piece I believe was about the size of a dinner plate. Cut a 1/4 inch or slightly wider from outside edge to center. The rawhide is dried, stretched and stiff to begin with. Dry to cut the circle from an area that has about the same thickness throughout the circle. Once cut place it in water and let it soak long enough to become pliable again, then stretch and work it back to a softness. I tie one end to something high (garage door track) and place the other end into a variable speed drill, so you can go slow. Pull hide out taunt then begin twisting the rawhide until an even twist is showing the entire length. I then tie a small stick the the loose end and place the stick through a weight lifting weight (weight bar hole in center) and let the weight hold tension on the string as it dries. Fashion the weight so it cannot spin and unwind the twisted rawhide. Once dried take some sandpaper and rub the length to smooth out any bumps. I then take some lard or bears oil and apply to the string. It will still be stiff when dry. You can work the ends some so it can be tied to the bow. I have not yet had one break, but probably lucky so far. I have used on 50-55 lb. bows with good results. The string will be sorta elastic and slow, but it is primitive....Good luck
L.A. Clark