ORIGINAL: D.Parsons
How do you figure Peak draw fource ratio?
How do you figure Bow efficiency in %?
How do you figure Virtual Mass (gr)?
KE = mv²/450240 Mass ( gr ), Velocity ( fps )
PE = Potential Energy ( Energy stored in your bow at full draw )
Bow efficiency = KE/PE
To find KE, shoot an arrow through a chronograph, weigh it, then plug the numbers into the formula.
To find PE, measure the area under the draw-force curve of your bow. To get the d-f curve, use a boat winch and crank your bow 1" at a time and record the poundage each inch until you get to the center of the valley ( full draw ). Remember the area under the curve is now in Inch/pounds. You will have to convert to Foot/pounds when you're done.
Ex. your bow has 80 ft/lbs of KE and 100 ft/lbs of PE, 80/100= 80% efficiency.
The other stuff ( Peak draw fource ratio and Virtual Mass ) I don't know. It's great stuff to mess around with in the winter.