Really, sorry for the confusion. The only reason that I have posted multiple times was to clarify. I agree 100% that my original statements should have only been posted once. But they seemed to get disorted for some reason. The reason that I made the original post was in support to the origianl post to the topic. However, the quote that I used was said to be mine at one point, that it was taken from a paper at another and that I am defending it it in another, along with having some false accuation made against me. For some reason my point needed to clarified.

Let me explain, I claim to be no expert. However, Dr. Ashby's studies and opinions are valid to me and I do believe that a lot of work, actual testing, expertise, and education goes into a lot of his findings. Someone has proclaimed that his statements (or some) are exagerated and idiotic. Since Dr. Ashby frequently visits another forum, I am just inviting this person to have a conversation with Dr. Ashby to explain why they feel his findings (or some of) are idiotic and exagerated.

I'm really not uderstand the difficulty in understanding this. I really don't have a lot of interest in defending Dr. Ashby's points especially when he can do so for himself. However, I do have interest in defending what I posted especially when it gets distorted.

Well, I tried to be as clear as I could, so this will be it for me.

Good Hunting to everyone!

Exactly. Sylvan. Gains in KE with arrow weight are minimal but gains in momentum are directly proportional to the arrow's weight. Increase the arrow weight by 30%, you've increased KE maybe only 2-3 ft lbs, but have added 30% to your momentum factor. At the same time, effect on trajectory is practically nil, at typical hunting distances. Doesn't make much sense to me to be pushing the edge on arrow weight in the interest of flat trajectory, when a modest increase in weight is so beneficial - especially on downrange performance - and has such a minor effect on trajectory.

I still live by the old archery addage, "For hunting arrows, use the heaviest arrow that will still give you acceptable trajectory." It works for all bows at all performance levels and with all legal draw weights. Go by the adage and you'll get a good hunting arrow. Seems like many guys are trying to make up a new one: "For flattest trajectory, use the lightest arrows you can, then pencil whip the KE to make it look like it's an acceptable hunting arrow." It'll work for high performance bows but you start sliding down the scale on performance and they start sucking wind pretty quick. Then choosing a proper broadhead design gets critical at lower power levels, so I always recommend a sharp, cut on impact 2-blade head. Again, it works on all arrows regardless of the bow's performance level as long as it's legal draw weight and properly tuned.

I've tried the light arrow stuff and found out it was more work than I ever wanted to put into it. I found I was spending more time fiddling with the bow than shooting it. I found out my shoulders didn't like the draw cycles they're building into cams these days. But back to arrow weight...

Follow me on this'n. Say you shoot a light arrow vs a heavier one. Say your lighter arrow is carrying only 2 ft lbs less energy than the heavier one. Okay, since physics tells us that energy cannot be destroyed, those other 2 ft lbs have to be somewhere. Since the arrow doesn't have 'em, then obviously they're still in the bow. Right? Say you shoot 100 arrows that day. You've subjected your bow to 200 ft lbs of extra energy which becomes noise, heat and vibration. Say you shoot a hundred arrows a week, year round. At the end of the year, your bow will have absorbed more than five tons of excess energy. Five extra tons of noise, heat and vibration. Of course, noise disperses part of that energy into the atmosphere and part is transmitted through the bow into your hand, wrist, arm and shoulder but, hopefully, you see the point I'm trying to make. To get an idea of how much excess energy you've got impacting the bow with on every shot, take a 2-pound lead weight, raise it exactly 1 foot over your big toe and drop it. (Pause for folks to conduct said experiment.) Did it feel good? Wouldn't you rather have that much more power in your arrows rather than dropping on your toe?[8D]

Any questions why your sights and rest move and have to be reset over the course of the year? Any questions why so many guys buy a new bow every year? Any questions why I won't buy a used compound?

True fact of the matter is that, in the general population, not 1 guy in a hundred - maybe even one in a thousand - truly knows his arrow speed or weight. Even fewer have actually checked their FOC, or even knows what the devil it is. Lots of those fellas that say they're shooting 300 fps are visibly upset when they actually do shoot through a chrony and find out their 300 fps (because that's the IBO speed for their bow) is really only 260 fps. Do they really need to be pushing the raw edge of arrow weight when they're hunting? I think not. So, I refuse to recommend they do anything other than what I do. I know my way would work for everyone. I know that light arrows have their limitations.

500 fps wrote: Very small! 0.08 ft/lbs.

If you have a very good chronograph that is capable of discretely detecting a 0.1 ft/sec change in speed then for your experiment the smallest amount of energy change you can detect is therefore only 0.05 ft/lbs. The difference in your measuremts is only 0.08. The question is whether or not your accuracy can justify your conclusion.

If, for example, you want to conclude a measurement result of 10 inches is really shorter than a measurement result of 11 inches how precise must you be with the measurement. Clearly it must be less than +/- 1/2". If your chronograph has discrete increments of 0.1 ft/sec then under the best of circumstances you can not determine if one energy measurement is greater than the other unless the differece is greater than 0.05 x 2 or 0.1 ft/lbs. Again that would be under the best of circumstances. Normally, meaurements are not considered acceptable unless the discrete limit is at least 1 order of magnitude smaller than the minimum amount needed to draw the conclusion. In other words in the 10" smaller or larger than the 11" measurement you would need discrete measurement increments of +/- 1/2" = 1/10 = 0.1" In terms of your experiment then you would need increments of +/- 0.04" = 0.08/10 = 0.008 ft/lbs. In order to get discrete energy measurements of 0.008 ft/lbs you need discrete velocity measurements of 0.016 ft/sec.

I should add that errors in the measurement of arrow mass will compound the problem.

BobCo19-65 wrote: I'm really beginning to question your comprehension skills. The statement that I said was idiotic was that "kinetic energy has absolutely nothing to do with penetration". According to his published work HE DOES NOT BELIEVE THAT IS TRUE. I don't know where you got the quote and I don't care it has nothing to do with it. YOU posted it and YOU still seem to think that it was correct. ASHBY DOESN'T. Read his paper! So how would you like me to begin the conversation. Here goes...

Hello Dr. Ashby, from your work I see that you and I pretty much agree regarding the issue of KE, momentum and broadhead design on penetration of game animals. But there is this fellow on another forum who is obsessed with the idea that I think your views are idiotic. Do you have any suggestions as to how I might approach him without without resorting to calling him names and ridiculing his thought process as he has mine?

I agree. Now we are at the point where some are actually trying to argue that a lighter arrow can give you more KE/momentum! I'm not against more speed at all, but like you said once you have acceptable trajectory the gains you get by improving the trajetory just a little more are in my opinion not worth the losses in energy/momentum wear on the bow etc...

I recognize that this difference is small, so small in fact given the measurement errors you mentioned, probably not in the realm of statistical significance. But.....those are the only reasonably accurate #'s I had access to. I wasn't going to cook the books to make a point. The #'s are in fact significant (statistcally speaking) in some single cam designs. Enough so that it can't be discounted as measurement errors.

I wasn't using this as a means of justifying hunting with lighter arrows, or to take sides on the KE vs M debate. I merely threw it in as an interesting anomaly that is present in some bow designs. Just a curious blip that occurs that was peripherally related to the topic at hand.

You are kidding right.......I could have sworn that I mentioned that a bunch of times. Comprehension problems????? On my part?????


Here is another interesting quote from Dr. Ashby. I'll try to make this as clear as posible, I got it from Tradgang.com posted March 24, 2005 by Dr. Ashby.

Pretty interesting. Increased tissue resistance encountered by the faster arrow.

BobCo19-65 wrote: [/quote] and again the complete quote should have been Ethics problems?

Now you're making another quote with out an original thought of your own. More of the same technical discussion method of ridicule and quote an expert. Well, I'm not taking the bait this time. You can play your games with somebody else. You know I completely disagree with silentassasin but I respect that he is willing to put his own thoughts out there and defend them.

I have no idea at all what you are talking about.


I did not direct Dr. Ashby's quote at anyone, so I don't know why you seem to be offended. I posted it in general because it is pertanent. Correct, it is not my work, I found it from doing a little research and digging. Just wanted to pass the info along. It seems pretty interesting.

That's right you don't! LOL, just thought I'd use one of your discussion methods.

Actually I'm not surprised you don't know what I'm talking about you haven't all along! Your type is not all that uncommon. You use the words of a "guru" to get your idea out there and then if somebody challeges it you don't defend the idea you just insult the challeger by saying who are you to challenge the guru. Religious fanatics use the same technique. When you challenge the idea they present they argue that you shouldn't be challenging God. Pretty spineless if you ask me. I have no respect for it and I have no time for it so thanks anyway but find another chump!