What did he measure to figure the arrow's KE, Sylvan? It's velocity or speed of forward motion. Rotational, vibrational, et al. types of motion were not measured and so are excluded by default. They do represent energy that was transferred from the bow to the arrow, but wind up being unavailable to assist with penetration. So, they're relatively unimportant anyway - unless trying to figure a bow/arrow's efficiency right down to the gnat's arse. Like you said, fine points.

No probem at all Art. I knew you'd be interested in it.

Do I dare mention here that Dr. Ashby provided it himself (which he did).[8D][8D][8D]

Exactly correct and had he said it the way you just did I wouldn't even had mentioned it but he did specificlly say there were included not excluded so I just pointed out the minor inconsistency.

BTW if you are interested in kinetic pulse here is a very good sight as well. Its about bulltets but the physics is interesting and somewhat analogous to arrows.

http://www.xmission.com/~fractil/math/kp.html

the site Bob gave is the same one you gave me a while ago and I couldn't open it. Still can't.

Burned a bookmark on that'n too. Thanks. Lots of good formulas. I'm not sure I don't like his kinetic pulse idea better than I like the power factor idea. Still, the problem with all this stuff is you must know your speed and arrow weight to figure them. Like I said, there are relatively few bowhunters who actually are that well informed about their equipment.

Here we are on page 11 and I don't think I ever commented on Coug's original post. Sorry, Coug. I agree with you, of course.

MNrut wrote: True. All things being equal more KE also means more momentum and therefore more penetration. The way to more KE/momentum for the same bow, assuming you don't want to pull more weight, is a heavier arrow. Agree?

No problem Arthur. I am just sitting back trying to take all this in when I come in to the forums. Lately I have not been able to read as much as I would like and have not read Ashby's studies or any of the links provided by various members. I will try to get to around to it.........uh, perhaps I am better off not doing so.[8D]

Personally, I hope I didn't give the impression I was totally discounting KE because I am not. Being inept at times conveying my thoughts, especially when I am in a hurry, I just wanted to say that the average bowhunter should not get so caught up or be so worried about his KE that he puts so much emphasis on it that he becomes mystified and confused. Personally, I have not been near a chrono for years(I probably should invest in one just for kicks), but I have a good idea what is fast enough for me and what gives me optimum penetration.

Arthur...you had me going for a few minutes after I read your post about some wanting minimum KE levels to be able to bowhunt. First off, I have never heard that mentioned before and think something of that nature would be impossible to enforce. Second......shooting 60-65 lbs. 2216s using fingers with mid-1980's compound bows probably does not show high KE, but I do know I got enough penetration to bust through bone and had several passthroughs on midwest deer leaving the arrow sticking in the ground.

Hmmmm, the topic of broadhead designs for penetration purposes would make for an excellent topic. I ain't starting it though!

Walks with a Gimp said it best........and unbelievable as it may seem, after shooting bows every year since 1977 I have only busted one limb........and that was a $30 garage sale recurve special!![8D]

Quoted from Dr. Ashby by others:
"As I point out in the article, not all momentum is equal! Momentum gained from increasing arrow mass [ie. heavier arrow] results in more penetration than momentum gained through increased arrow velocity [ie. speed]. The data here is clear cut [ie. more momentum with a heavier arrow]. The reason is because the increased tissue resistance encountered by the faster arrow (assuming both arrows have equal impact momentum) reduces the time over which the available momentum is disipated in the tissues: the lighter arrow will have a lower Impulse of Force - regardless of the distance of the shot."

The tricky part here is where he says "....(assuming both arrows have equal impact momentum)...." Because, in the first sentence he states "....not all momentum is equal!"

While this paragraph is just a slight indication of his complete work, it is a glimpse of reality as best it can be defined via forums. A breakdown of the paragraph results in some specifics to which Sylvan has agreed/argued from the beginning.

It's the indepth understanding of the parameters of testing that is not inclusive in forum interaction. The vector query is just one example of confusion.

I'm surprised and delighted that Sylvan carried this as far as he did; and, I thank him again for both the content and his perseverance.

BTW, KE usage as a measuring term became popular with the advent of mechanical broadhead usage. The industry needed to gauge usage due to problematic issues with misuse of the earlier mechanicals. The 'goat' was KE.

Len, you have to take the entire package when discussing his work, not just snippets. Did you read the part about faster arrows encountering increased resistance? Resistance is geometrically proportional to the arrow's speed. Meaning a lighter arrow that's travelling twice as fast as a heavy arrow will encounter resistance 4 times that of the slower, heavier arrow. If it could be shot 4 times faster it would encounter 16 times the resistance. That's why he says increasing momentum by increasing speed is not equivalent to increasing momentum with weight. The faster arrow will encounter more resistance. The slower arrow will encounter less resistance. (That's the fallacy in TFOX's thinking that driving an arrow faster will help it overcome friction. Quite the reverse is true.)

Even ballistics programs show the difference in the different rates of speed KE lost over distance while cutting through thin air to the target. Lower speed (w/heavier arrow) = lower resistance = higher percentage of retained energy = increased penetration potential. Higher speed (w/lighter arrow) = more resistance = lesser percentage of retained energy = less penetration potential. The smaller diameter and superior damping qualities of carbon help cancel out some of that increased resistance, perhaps, but still, it's the cutting edges on the broadhead blades that encounter the lion's share of the resistance. So, you'd have to shoot a smaller diameter head with fewer blades on fast arrows to significantly offset that increased resistance.

Again, with smaller, thin skinned animals like deer, it's not likely to be that big a deal. On larger, tougher game though, it would be more noticeable.

Arthur:

VERY insighful and quick. I've learned to expect that from you.

By my post "While this paragraph is just a slight indication of his complete work, it is a glimpse of reality as best it can be defined via forums.", I was trying to get across that "snippets" taken out of context can be manipulated in many ways. Even though, the basis of what WWAG posted is what I practice and what seems to have prevailed through these many pages.

No, I haven't read his works, nor do I have the time. In the scheme of things, I leave certain items to experts in their field and rely on them to give me pertinent data. I only question them when I need clarification or when something 'goes against the grain' of normality. Much like I rely on you for your expertise.

Ah, baloney! You're as full of it as I am. [8D]