After reading most of the replys to this subject (one of my favorites), we seem to be focusing on KE and/or momentum. While these are the easiest to use for judging penetraition (well...KE at least) one thing has gone without much mention. Velocity and the ability to cut (penetrate). Fluid dynamics has been mentioned, but there is more. GENERALLY, the faster something is moving, the easier it cuts. You can put a chunk of 100lb test fishing line on the end of a sledge hammer, and you'll have GOBBS of KE...but you won't cut grass untill you get it moving...FAST.
When talking penetration, and what affects it, velocity must be part of the equasion (and in KE it is......but there is more to it than just using KE) When you go from field point to broadheads, velocity plays a MUCH larger roll (field points MOST push matter aside, where blades cut without much movement).
I think it was outdoor life that did tests on like 19 broadheads on 3 different arrows...what everyone guess would happen didn't. The BEST penetration was with an expandable on the LIGHTEST arrow. And arrow diameter was not the differance. they used weighted and non wieghted carbon arrows....non wieghted did better than weighted (both did better MOST of the time than aluminum). And the expandables won out most likely due to the low friction of the blades (not very tall) compared to the HUGE surface area of most fixed blade heads.
I'm NOT saying we all need to buy a Bowtech Black Knight and shoot 80 Lbs w/ 300 gn arrows.....but speed alone DOES affect penetration (same KE but more speed, the faster/lighter arrow wins....with blades, it wins by a lot).

Edited by - Stealth_Force on 08/18/2002 00:33:06