To figure the cutting surface I take the cutting diameter and divide it by two, then multiply the number of blades by that figure. I then add in any cut on contact tips or blades that are not full size. The blade thickness issue generaly comes out in the testing. thicker blades tend to hold up better and not break in the plywood, tire and drum.
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ORIGINAL: 5 shot
Great stuff btw 5-shot!
The way I look at it, blade surface area and total cutting surface are different. What I was looking for was the size of the wound channel. While I agree that longer blades do have more "surface area" they don't always have more cutting ability or larger wound channels. I could include both, but I think that the actual penetration testing kind of "proves out" how the heads penetrate, so it works out in the end. Of course I know it's still not an exact science, but at least I think it makes for better more accurate comparisons between heads.
This is hardly a "cutting surfacee" figure you come up with at the end. It's simply a different way to give it some arbitrary figure. I guess it's OK if you do the all the same, but it's hardly CUTTING SURFACE. The major contributor to this total is number of blades. I guess it works, but I can see it giving false hope. For example, the old Rocky Mountain Razorbacs with the 5 blades. Through it all it's a ho hum broadhead.... but 5 blades really boost the number in a misleading way. In fact, it's really a crappy broadhead. Too small a cutting diameter that leaves terrible blood trails.
Well, I don't know how else to figure total cut, each blade has 1/2 the cutting diameter, so you have to divide the cutting diameter by 2 then multiply by the number of blades. I agree that some heads like the old NAP razorback, ( the rocky mtn razor was actually a pretty good head) can get a boost, but when the fragile head hit's a steel drum or plywood those blades breat off pretty quick. The razorbacks did fly well though.