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RE: What is the best way to get kinetic energy II

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RE: What is the best way to get kinetic energy II

Old 03-24-2005, 04:22 PM
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Default RE: What is the best way to get kinetic energy II

[link]http://www.bowhunters.org.au/bulletin.htm[/link]

Boy, this thread is getting just as good as the one with the same topic over on The Bowsite. Attached is a link to a web page that has Dr. Ashby's latest report on KE, Momentum, and Penetration. It's a good read for anyone who has been following this thread.

Athur P., judging from some of your previous posts, me thinks you have already read it.
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Old 03-24-2005, 04:42 PM
  #62  
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Default RE: What is the best way to get kinetic energy II

I think most of us agree here on the basics and are quibbling over "every wind of doctrine" , What I have taken from this thread is that high country's philosophy is all wrong , a super light arrow going fast is not necessarily better . Allot of people , must agree as I see they are offering a $500 discount for direct factory sales , guess that kind of slaps their dealers .
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Old 03-24-2005, 04:46 PM
  #63  
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Default RE: What is the best way to get kinetic energy II

Did you read on down on Tapley's site about what is needed to penetrate a solid? He used shields in his example, but says it's momenentum that is needed to penetrate a solid and that an arrow that is too light will bounce off.
That's exactly what I've been saying. It is momentum that determines whether or not a projectile penetrates or bounces off. If it does penetrate, however, it is KE that defines how far.

Earlier, I mentioned using a heavier arrow for extra momentum just in case of a bad shot and needing the arrow to penetrate bone. Same concept.
I agree with this statement. No argument there. Heavier is better for penetration. I've said that all along. Heavier results in more momentum and more KE. But also it is interesting to point out that faster is more accurate, not only because of flatter trajectory but because there is a shorter dwell time while the arrow is attached to the string during acceleration. Same concept of longer brace being more forgiving. But that for sure is another thread.

I think we agree alot more than we disagree.
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Old 03-24-2005, 04:47 PM
  #64  
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Default RE: What is the best way to get kinetic energy II

Actually, I've not read that paper before, Olink, but I did burn a bookmark on it. Thanks! I have read Ashby's arrow lethality study that he did in Africa several times. And I'm anxious to see the results of the new study he's conducting in Australia right now. I've got a lot more respect and trust for the results of a scientific study done in the field, on real animals, over a span of several years than I do for those goofy 'tests' a bunch of people have done with a block of foam in the backyard in an afternoon.

But also it is interesting to point out that faster is more accurate, not only because of flatter trajectory but because there is a shorter dwell time while the arrow is attached to the string during acceleration.
I could argue that point till the cows come home too. That has not been my experience with the progression of compounds over the past 25 years, at all. What I've seen is the shorter, reflexed riser bows with lower brace heights and higher letoffs are far more critical of minor form flaws and make you pay dearly where accuracy is concerned. Especially on a cold, damp, windy day when you're up in a treestand and have the adrenaline pumping. It's a little tougher to execute a shot with proper form in actual hunting conditions. Far different from standing flat footed on a shooting stake, where you've got the time to double check every minor aspect of your form before releasing.
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Old 03-24-2005, 05:16 PM
  #65  
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Default RE: What is the best way to get kinetic energy II

Okay, I guess we'll agree to disagree then. Still, the answer to the original question, "what is the best way to get kinetic energy" for a given bow at a given draw weight and given draw length is to shoot a heavier arrow.
We don't disagree at all regarding this. I've been saying heavier is more KE and more momentum all along.

What I've seen is the shorter, reflexed riser bows with lower brace heights and higher letoffs are far more critical of minor form flaws and make you pay dearly where accuracy is concerned.
We agree again. I said that a longer brace height is more forgiving. The reason it is more forgiving is because the power stroke is shorter and therefore dwel time is reduced. All other things being equal, faster means shorter dwell too therefore more forgiving.
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Old 03-24-2005, 05:17 PM
  #66  
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Default RE: What is the best way to get kinetic energy II

I would love to read the paper Olink posted but when I try to load it Adobe only loads the 1st page and then I get an error. Any suggestions?
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Old 03-24-2005, 05:23 PM
  #67  
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Default RE: What is the best way to get kinetic energy II

I think most of us agree here on the basics and are quibbling over "every wind of doctrine"
I think you are right ijimmy. Actually my very first post on this subject said as much in that I think the argument is silly. Of course then I charged right in to help to perpetuate it. And here I am still keeping it going. I think I should spell silly s y l v a n.
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Old 03-24-2005, 06:33 PM
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Default RE: What is the best way to get kinetic energy II

Sylvan - Instead of letting your brower opening the document, try saving it as a .pdf file on your PC and then open the file with Adobe.
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Old 03-25-2005, 03:49 AM
  #69  
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Default RE: What is the best way to get kinetic energy II

Sylvan - Instead of letting your brower opening the document, try saving it as a .pdf file on your PC and then open the file with Adobe.
Same thing, I guess I'll try downloading a newer version of Adobe.

You know I was thinking again how silly this argument is. If you think about it BOTH KE and momentum are just functions of arrow mass and velocity. They are both just numbers that you get by multiplying mass and velocity together but of course in a little different way so that you get a different result. However, increase mass and/or velocity and BOTH momentum and KE increase. Lower mass and/or velocity and BOTH momentum and KE decrease. But BOTH momentum and KE are again just numbers. You can't even measure either one them directly. There are only 2 real world things you have any influence on regarding momentum and KE and they are simply your arrow weight and how fast you propell it.

So to answer the original question, if you want more KE then throw your arrow faster or throw a heavier one or both. You'll have to decide for yourself what is best, but IMO put on a heavier arrow, that's the easiest.
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Old 03-26-2005, 03:42 AM
  #70  
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Default RE: What is the best way to get kinetic energy II

Arthur P,
I had asked you why you used pound seconds as opposed to slug ft/sec for momentum and I finally realized that it was a dumb question. If I'd thought about it a bit I would have known.

Following just the units through...
Momentum = mass x velocity = slugs x ft/sec
slugs = pounds/ft/sec/sec

so momentum = pounds/ft/sec/sec x ft/sec = pounds x sec or we say just pound seconds

so slug ft/sec is identical to pound seconds

KE is talked about in foot pounds for the same reason. Its just the result of following the units through to the simplest terms. I guess sometimes we get so used to saying something we forget why. I did anyway.
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