Bob,
Interesting question this, and something I have thought about re arrows penetrating armour.
I would expect that pushing a drill bit against wood would be very much the same as an arrow going through flesh in an animal, or at least I can't see why it could be any different. Why do you feel they are diofferent?
Maybe I can explain how I am thinking?
You are standing right up next to the deer with a short arrow fitted with a broadhead in your hand. The arrow is fitted into your cordless drill.
You push against the deer with the arrow head with the drill turned off and see how is penetrates.
You then turn the drill on so it is going at 2500rpm and again push against the deer with the arrow head and the same force.
Wouldn't the effect be somewhat more dramatic with the arrow spinning?
You could the same by punching the arrow at the deer without it spinning, and with it spinning at 2500rpm.
You could so the same test by punching the arrow forwards at about 200fps.
Imagine two arrows that are identical, but one flies straight forward without spinning at all, the other spins.
The arrows hit with a certain amount of speed which will differ, with a differing amount of rotational energy but the same mass. If shot from the same bow there is the same amount of total energy in the arrow swhen it hits. In a spinning arrow some of that force or energy will be rotational which means that as it weighs the same as the other it will be going slightly slower. The rotational energy has been robbed from the forward speed
The question is this.
Which penetrates better and does more effective work?
An arrow that passes it's way through a deer slightly faster in a straight stab like a sitilletto?
An arrow that effectively drills it's way through a deer slightly slower?
An arrow can be made that comes straight back at you! If the weight is slightly rear of centre, if there are very small fletchings at the nock end and also small fletchings at the front and if the wind is coming from the correct dorection an arrow can turn so much it comes back! Must have been quite exciting for the guy (and his friends if he had any) who found this out, perhaps only for a short time though!
If you take a bare shaft without a point (so the weight isn't forward) out into an open space with the wind blowing from the side you will almost always see it turn quite dramatically so that it is flying side on to the the original direction. Often the arrow will end up going between 45 to 90 degrees to where you wanted it to go. This is failry dangerous! Put some drag on the back of the arrow and the straight shot will be improved. Put a point on the make the arrow CoG move forward and the arrow will fly better still. Make the drag element such that the arrow rotates and it will be even more stable.
I do agree that there is a lot of marketing hype used to sell archery products. Recently I saw an arrow marketed as having the latest high tech weight forward technology! Like people haven't been doing that for thousands of years!