ORIGINAL: quiksilver
So, I guess when you consider that, if you're shooting two otherwise identical arrows (same head, same speed, same weight, same friction coefficient on the shaft, same fletchings) - and arrow A is a lincoln log (diameter .5"), while Arrow B is pencil thin (diameter .3") - you're probably going to get better penetration with Arrow B, simply b/c the force is transferred over a smaller surface area.
Same goes with broadheads. If you have two identical arrows (same speed, same weight, same fletchings, same diameter, same friction coefficient on the shaft) - and you put a 125 grain muzzy on shaft A,while on shaft B, you put a 125 grain mechanical head with a cutting diameter of 2.75" - you're bound to get much better penetration from arrow A (provided that the blades are the same thickness/sharpness).
So, while a KE calculation is nice and handy, there are hiddenpenetration killers lurking (fat shafts, shafts that "drag" more than others once moving through the target, broadhead selection, etc..) Unfortunately, these are things that can't be easily quantified by a quick KE or Momentum calculation. Instead, we resort to field testing.
Good post and good discussionthough.
Another very intelligent way of putting it.
Muzzy and other boradhead manufacturers realized that you have to have some sort of chisel tip to break through bone. But at the same time did not want a solid heavy broadhead design. So, they created the Muzzy with the chisel tip and replaceable blades. For years people have been proving that a broadhead like this will do the job.
Combine that with a smaller diameter arrow and maybe up the FOC and you have a dangerous combination.
In other's eyes all that matters is Ashby's test. However, all of Ashby's tests are done with everything being equal but weight. Yes, he switches broadhead design.And yes, he talks about FOC. However, he never compares arrows with thinner shafts to thicker ones. He states that a high FOC on a carbon arrow will dramatically improve penetration yet doesn't compare that to a heavy arrow with standard FOC.
He prefers extremely heavy arrows with heavy solid chisel broadheads and that is evident with the way he tests.