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KE reamains constant?(roughly)

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KE reamains constant?(roughly)

Old 11-21-2002, 06:38 PM
  #1  
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Default KE reamains constant?(roughly)

So...If I have a bow with specs as such
60#
30" Draw
350 grain arrow
250 fps = 48.58 Ft/lbs

My K.E. will not change significantly unless I change...
A. Draw length
B. Draw weight
C. New Bow<img src=icon_smile_big.gif border=0 align=middle>

So when looking at specs I can get a pretty good idea what the KE will be from the IBO speed (- for string accesories)even if I shoot a heavier arrow? So the KE is a rough way to measure efficiency???

Yikes! I just wanted to shoot a deer and now I'm back to Schoolin'!lol



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Old 11-21-2002, 08:57 PM
  #2  
tm
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Default RE: KE reamains constant?(roughly)

True to a certain extent. For instance if you're in the mid weight for arrows going up in arrow weight will deliver a slight increase in kinetic energy, going down a slight decrease. This is assuming that you're shooting arrows with roughly the same spine.
The thing to watch is getting too light in arrow weight. I often put it this way &quot;would you rather get hit with a piece of foam rubber going 500 fps or a brick going 40 fps&quot;. Kinda extreme, but it does get the point across.

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Old 11-22-2002, 01:07 AM
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Default RE: KE reamains constant?(roughly)

would you rather get hit by a 2x4 going 5 fps, or a sliver going 500? (ask the tree after a tornado)
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Old 11-22-2002, 08:41 AM
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Default RE: KE reamains constant?(roughly)

KE doesn't seem to change significantly when changing arrow weight, on the same bow. As weight increases, speed decreases. Momentum determines penetration. Of course, KE is a factor here, also. But a heavier object resists opposing forces better than a lighter one, if speed is roughly the same. There comes a point where one overrides the other. At what speed and arrow weight this occurs can probably only be borne out by testing different setups. One interesting thing I came across when testing arrows was a lighter (not much, 15 gr), stiffer arrow worked better with my bow, regarding penetration. This was found shooting broadheads into a foam target. Both arrows were spined OK for my bow. Redline 410 at 29&quot; and PSE 300 at 29&quot;, both with 100 gr heads. The PSE is on the stiff side, by the chart, but shoots and penetrates much better.
Trushot, you definitely need a new bow.<img src=icon_smile_big.gif border=0 align=middle>

Phil.
&quot;Could you guys be quiet, my dad's trying to shoot.&quot;<img src=icon_smile_shock.gif border=0 align=middle>
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Old 11-22-2002, 12:19 PM
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Default RE: KE reamains constant?(roughly)

Thank YOU Phil!

Now could you PLEASE explain that to my lovely Wife??

Wife-&quot;Why on God's green earth do you need another bow?&quot;
Me-&quot; It's all about the KE HoneySugarPieChickadeeDreamboat&quot;
Wife&quot; No, it's about the AK&quot;
Me-&quot;AK???&quot;
Wife &quot; The [email protected]* Kicking you'll recieve if you buy another bow!&quot;<img src=icon_smile_evil.gif border=0 align=middle><img src=icon_smile_tongue.gif border=0 align=middle><img src=icon_smile_big.gif border=0 align=middle>

I've got some work to do before I get into that new VFT!LOL<img src=icon_smile_wink.gif border=0 align=middle>

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Old 11-22-2002, 12:55 PM
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Default RE: KE reamains constant?(roughly)

I disagree! Arrow weight has more effect on changing KE than speed does. I currently shoot a 350 grain arrow at 307fps giving me a KE of 73#. If I increase the arrow weight to 450 grains which will drop the speed to about 285fps, but the KE increase to 83#. Go to www.bowjackson and run some models on the KE computer it will confirm what I am saying.

Aim Hard!
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Old 11-22-2002, 05:01 PM
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Default RE: KE reamains constant?(roughly)

FlHunter,
I tested my bow through the Chrono with 350, 450, and 525 grain arrows and all the speeds decreased exponentialy so that my KE was within a pound (or so)on all tests. Is this just My bow?

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Old 11-22-2002, 08:07 PM
  #8  
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Default RE: KE reamains constant?(roughly)

FLHunter, I've run the #s on my bow. BowTech P38 dual cam at 60#.
300 gr at 318= 67#
350 gr at 295= 68#
375 gr at 286= 68# This is what I shoot day in and day out.
400 gr at 277= 68#
500 gr at 249= 69#
All close enough to call it constant, or consistent. Though as I stated earlier, I feel the 500 gr arrow would penetrate better, possibly. On deer sized game, any of these will blow through with no problem.
I just ran your #s on Jackson's site. Your increase in KE comes from less speed loss than expected, with 100 gr more arrow. 350 gr at 306= 71#. 450 gr at 271= 73#. If your bow chronos 285 with 450 gr, then that's much faster than Jackson's site calculates.

Trushot, maybe you could break it to her over a nice dinner at her favorite restuarant.<img src=icon_smile_wink.gif border=0 align=middle>

Phil.
&quot;Could you guys be quiet, my dad's trying to shoot.&quot;<img src=icon_smile_shock.gif border=0 align=middle><u></u><u></u><u></u><u></u>

Edited by - pdq 5oh on 11/22/2002 20:25:25
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Old 11-22-2002, 10:49 PM
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Default RE: KE reamains constant?(roughly)

LOL<img src=icon_smile_big.gif border=0 align=middle> Good one Phil! Have you checked out my website?? Been there!LOL. Thanks for all the info Guys!

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Old 11-23-2002, 03:44 AM
  #10  
 
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Default RE: KE reamains constant?(roughly)

A. Draw length.
- Longer draw length means your arrow will need to be fatter shaft which means it will be heavier which means... Well, I'm not sure what that means. Typically, a heavier arrow will not change KE by much but if this heavier arrow is shooting the same speed as the lighter arrow at lower poundage, then yes, increasing draw length will increase KE. Whether it is a significant difference, I don't know. And I could be wrong on all that.

B. Draw weight.
- Increasing your draw weight will shoot the same weight arrow faster giving it more power. And vice versa for lowering poundage. Draw weight will indeed &quot;significantly&quot; change KE. So b is the right answer.

C. New bow.
- If the new bow has a faster AMO or IBO speed then it will have an increased KE from the slower bow using the same poundage, arrow and arrow weight and draw length. Although the increase in KE will not likely be significant.





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