Kinetic energy

Discussion in 'Bowhunting forum' started by scottg, Sep 30, 2007.

  1. scottg

    scottg Huntin Junkie

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    For the math guys. What is considered the minimum energy needed for deer hunting?

    Also what formula do you use to figure your energy?

    I am thinking of dropping my draw length a little to be a little more comfortable, but I don't want to start loosing too much speed and energy.


    Thanks
    Scott
     
  2. Ke

    to find kenitic energy you take arrow speed times arrow speed times arrow weight and divide by 450240. Example 245 x 245 = 60025 x 360 = 21609000 divided by 450240 = 47.994402KE
     

  3. Ke

    To get a rough idea of arrow speed if you know your KE take the Ke x 450240 and divide by arrow weight then take the square root of the answer and that will give you a rough idea of your new speed. It will be a little slower if you lower the arrow weight and a little higher if you increase the arrow weight. we are only talking about a couple of feet either way.
     
  4. brokenarrow

    brokenarrow Evil Genius

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  5. brokenarrow

    brokenarrow Evil Genius

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    As for the min KE...I remember the # being around 35 for medium game(whitetail...etc.)might have been alittle lower too...:noidea:
     
  6. Werd

    Werd Senior Member

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    is 55.53 good.??kuz thats what im at. my dads at 67.01
     
  7. BowhuntnHoosier

    BowhuntnHoosier Bisquit.......

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    Good answer.:peace:
     
  8. Dredly

    Dredly Site Guru

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    55 should be enough to pass through at least 1 shoulder (not saying you should shoot the shoulders but...

    I'm about 63 - 65 I think.
     
  9. IChim2

    IChim2 IChim2 and he's a shooter

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    I'm getting 78lbs KE...waaay more than needed for where/what i hunt.If possible i'd give you some.:laugh:
     
  10. scottg

    scottg Huntin Junkie

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    Thanks. That was what I was looking for.

    I am shooting a Tribute with 328 IBO. I know that I will not see that. I guess that another question is how much difference will a 1" shorter DL make on speed? I'm at 29" now, but with the loop and release, I'm having to stretch some. My arrows are Carbon Express radial x-weav - 300 series and I think they are 8.2 or 8.4 grn/in. Total arrow weight is around 389, the last one that I weighed. On the other hand, I need to have them re-cut because they are about 1 1/2" too long now. If I drop down to a 28" DL, then I can have them cut back some more. That would take about 20 grn off of my arrow weight.

    P.S. the reason that my arrows are too long is that one of my sons had an arrow OOPPSSS and our Catahoula chewed his to bits. I was getting ready to go to work for a month, so I gave him my arrows (we shoot the same ) and he would go and get some new ones for him. Well he kept mine and gave me the new ones, that happen to a little to long.
     
  11. IChim2

    IChim2 IChim2 and he's a shooter

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    This is only my thought.If you drop the dl 1" and you shortened your arrow lenth you will probably still be about the same KE as you were..But also from what your saying about your present dl being a tad long you will probably shoot better by shorting it.You will loose a tad of speed with the dl change but you will pick up a tad shorting your arrows..All and all there probably won't be enough to notice any difference.
     
  12. scottg

    scottg Huntin Junkie

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    Thanks for the help. I am getting ready to order a chrono to check speed. I already have the digital scale for getting arrow weight. The bow is pretty quick right now. I am able to shoot 1 pin out to 30 yds. At 40 yds I only get about 2" - 3" drop. Very flat shooting. I am also at only 65 lbs. I still have a few to go as I get my arms and shoulders back into shooting.
     
  13. BowhuntnHoosier

    BowhuntnHoosier Bisquit.......

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    WOW thats some serious KE.
     
  14. IChim2

    IChim2 IChim2 and he's a shooter

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    I know....way more than i'll ever need.I guess that one of the advantages of having a 30" dl.I guess thats why i'm not into the speed thing like others cause getting max speed wouldn't be a problem for me....That's from shooting a 503 gr xx78 2512 pape's mossy oak ultra/lite 29.75" with a 100gr bh out of a FB Truth set @ 71lb's.I'd hate to get hit with it.:biggrin1:
     
  15. kbohunt

    kbohunt are u a fat boy?

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    Ha,Ichim

    You might want to re-check your arrow weight.
    Easton charts say a XX78 2512 shaft only weigh's 299gr at 30inchs and with a 100gr head and inserts and vanes you should only weigh around 430 or so.:noidea:
    I shot a friends truth and calculated the KE with Beman-400,blazer vanes 30in draw and 67lbs.100gr muzzys, total arrow weight with broadhead 349gr-293fps KE-66.55 :biggrin1:
     
    Last edited: Sep 30, 2007
  16. IChim2

    IChim2 IChim2 and he's a shooter

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    You need to add for uni-bushing + glue for the vanes/nocks/incerts.....I've wght these several time's on 2 different scales and both come out +/- 1gr.Some times you have to take those charts with a grain of salt...
     
  17. Werd

    Werd Senior Member

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    you should open a business.....for K/E. 2.00$$ for 5 KE.. LOL
     
  18. kbohunt

    kbohunt are u a fat boy?

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    Ok!

    I have 2512's in my shop that weigh + or - a grain.
    Ive been building arrows for 25 years,and setting up bows.
    A 30 inch 2512 fletched with unibushings and nocks weighs 349gr.
    Add what ever head you want.
    I have seen probable a dozen Bear truth and code bows and as of yet have found one that can produce a KE of 70 or more,unless your shooting over 70lbs.:noidea:
     
  19. Holy Smokes

    Holy Smokes Senior Member

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    Never minded them K figures
    just set up a good bow and a good head and poked quite a few with very few problems that weren't me related.
     
  20. IChim2

    IChim2 IChim2 and he's a shooter

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    Ok..I've wght'ed these several times and always come up right at 503gr's.I have my Truth set at 73lb's (forgot that i max out the limbs)...30" dl and have crono'ed it on 2 different shoot through systems and come out at 262/264 fps.Rather the scales or crono is right i don't know but 2 different one's i doubt it.But i'm only going with what the scales/crono is telling me.One of the scale's/crono is at the shopp that everyone uses and haven't heard any problems and it reads the same as my friends.Like i said,i'm only going with what the machines are telling me.Don't want to get into a wissing contest....but if for some reason the total wght is less...i'll take that too.
     
    Last edited: Sep 30, 2007