Originally posted by katman:
Looking at the pics of Rob's bow almost looks like a recurve strung at that brace. Lower brace less preload.
So tradeoff is a little less performance for more smoothness and a shorter overall length? Is that made up in the increase in draw length?
How does short riser/longlimbs effect shootability?
Thanks for being patient with me Kirk.
No problem Gery, You've got the right idea about a longer working limb having a bit slower arrow speed at shorter draw lengths due to more limb moving forward, which is more mass weight.
This is definitely mitigated by a longer draw length, and longer power stroke. This is why your average production line bow that safely draws to 32" performs pretty decent at 30", and average at 28", but dies on the vine at 26"-27". I build most my my bows "Draw length specific." to optimize performance at a specific draw lengths.
Now the part about a lower brace height having less preload isn't really much of a factor in aggressive r/d designs. Typically the amount of preload is built into the limb design in the form of reflex, and fade angle, and it isn't as critical on higher poundage bows as it is on bows 45#'s and under. a lower poundage bow will typically brace a bit higher to gain a bit tighter string though, and it helps quiet it down.
a really good example where brace height does effect preload is building a D shape long bow that draws 50 pounds at 32". This requires long sweeping reflex with longer limbs from 66-68" in total length. It would be advantageous to brace this bow at about 8" drawing 32". bracing it lower will not stop the limbs efficiently and produce hand shock. Now if you built the same bow at 50 @ 28" you could lower the brace to 6" and still have the same preload.
i hope that helps... Kirk