KE has nothing to do with penetration... apparently

Discussion in 'Tech Talk' started by TKP030, Apr 7, 2016.

  1. TKP030

    TKP030 Weekend Warrior

    Joined:
    May 12, 2015
    Posts:
    575
    Likes Received:
    147
    Dislikes Received:
    1
    Location:
    North Dakota
    Very interesting read on Outdoor life i saw on facebook about KE. the first half of the article i was thinking this guy is crazy and then he explained him self and made a very interesting point

    here's the article

    Physics for Bowhunters: Why Kinetic Energy Doesn
     
  2. Sota

    Sota Legendary Woodsman

    Joined:
    Jun 28, 2014
    Posts:
    25,227
    Likes Received:
    14,852
    Dislikes Received:
    113
    Location:
    Minnesota
    I don't know about all the math but I do shoot a 475 grain arrow out of a bow turned up to 11.
     
  3. elkguide

    elkguide Grizzled Veteran

    Joined:
    Jan 9, 2012
    Posts:
    6,488
    Likes Received:
    7,459
    Dislikes Received:
    6
    Location:
    Vermont
    Makes some sense.
     
  4. foodplot19

    foodplot19 Grizzled Veteran

    Joined:
    Sep 28, 2014
    Posts:
    8,583
    Likes Received:
    9,455
    Dislikes Received:
    5
    Location:
    West Central Missouri
    Agreed.
    Makes sense.
     
  5. Bowsage

    Bowsage Weekend Warrior

    Joined:
    Feb 3, 2016
    Posts:
    294
    Likes Received:
    60
    Dislikes Received:
    3
    Location:
    Virginia
    KE became a sales hype for the compound bow, through my own experience I found a well placed arrow with a scary sharp broadhead is what kills a deer .Its never been a BH problem or draw weight problem when it comes to the kill, taking a low percentage shot does. It doesn't take a freight train to kill a deer.
     
  6. JLhunts

    JLhunts Weekend Warrior

    Joined:
    Sep 26, 2015
    Posts:
    173
    Likes Received:
    1
    Dislikes Received:
    0
    Very good article
     
  7. MGH_PA

    MGH_PA Moderator

    Joined:
    Sep 23, 2008
    Posts:
    10,480
    Likes Received:
    325
    Dislikes Received:
    0
    Location:
    Cogan Station, PA
    Yep, I remember Tfox being the one who opened my eyes to this a long time ago on here. He was often met with some criticism on the subject, but yes, momentum is key and your FOC is a bigger driver in that as well.
     
  8. Justin

    Justin Administrator

    Joined:
    Jul 24, 2008
    Posts:
    9,825
    Likes Received:
    4,904
    Dislikes Received:
    0
    Location:
    Algonquin, Illinois, United States
    While you can't argue with fact that momentum effects penetration more than kinetic energy, we all need to realize it takes more than penetration to kill an animal. The #1 key is accuracy. Regardless of KE, momentum, speed or any other factor you need to be accurate and hit your target in the right spot. A big factor in that is the speed of your arrow. A faster arrow will fly flatter and arrive at your target faster. This brings some inherent accuracy benefits in that yardage estimates don't need to be as accurate and, to some extent, a faster arrow will minimize the effects of deer "ducking the string". While it may only be an inch or less - there are times when that can be the difference between success and failure. You get faster arrows by doing two things - shooting lighter arrows or shooting more poundage.

    It seems like all things in life seem to gravitate to that "happy balance". Sure a 900 grain arrow will out penetrate a 300 grain arrow shot from the same bow, but it will also be significantly slower. It's also overkill for whitetail hunting. Most adult male bowhunters seem to be shooting arrows in the 380-450 grain range, which IMO, is perfectly fine for killing whitetails. Hundreds of thousands of deer are killed each year with these setups. As Bowsage to accurately put it - it doesn't take a freight train to kill a deer.
     
  9. Born2Hunt

    Born2Hunt Die Hard Bowhunter

    Joined:
    Apr 4, 2011
    Posts:
    2,208
    Likes Received:
    289
    Dislikes Received:
    0
    Location:
    Southern Wisconsin
    Justin how much do the arrows you shoot weigh out of curiosity?

    Sent from my SM-G935R4 using Tapatalk
     
  10. Jake/PA

    Jake/PA Grizzled Veteran

    Joined:
    Feb 28, 2010
    Posts:
    3,494
    Likes Received:
    60
    Dislikes Received:
    0
    Location:
    Pennsylvania
    Yeah, I thought the kinetic thing was shot down awhile back?

    I just try to have a healthy GPI and FOC while still shooting around 270fps. Seems to work.
     
  11. remmett70

    remmett70 Die Hard Bowhunter

    Joined:
    Jul 13, 2015
    Posts:
    2,421
    Likes Received:
    394
    Dislikes Received:
    6
    Location:
    Rothschild, WI
    I can throw an 8lb bowling ball 25mph and it pretty much bounces off the pins. 14lb at 12mph knocks them all down.


    That is when I hit where I am aiming.
     
  12. BB4tw

    BB4tw Die Hard Bowhunter

    Joined:
    Jul 12, 2014
    Posts:
    1,640
    Likes Received:
    275
    Dislikes Received:
    1
    Location:
    Nebraska
    Kenetic energy is extremely important to arrow penetration.

    Kenetic energy is the energy of motion, if your arrow isn't moving, it isn't going to penetrate anything at all.

    Once contact is made, how quickly the kenetic energy dissipates is what is of greatest concern. This is where the KE figure looses its importance to the shot story and momentum figures become more useful.

    Many authors, and to some extent, bow manufacturers want to say that the two figures are at odds with one another or one hold higher importance. Fact is that efficiency is what we are all looking for.

    Efficiency is found when KE, momentum, archer skill, and equipment choices/condition are all in balance.

    To simply talk about penetration and monentum while excluding all other factors in the shot sequence is useless.
     
    Last edited: Apr 8, 2016
  13. Justin

    Justin Administrator

    Joined:
    Jul 24, 2008
    Posts:
    9,825
    Likes Received:
    4,904
    Dislikes Received:
    0
    Location:
    Algonquin, Illinois, United States
    Last year I killed 4 deer with 500 grain arrows and 1 with a 380 grain arrow.
     
  14. pastorjim08

    pastorjim08 Legendary Woodsman

    Joined:
    May 1, 2009
    Posts:
    10,390
    Likes Received:
    7,375
    Dislikes Received:
    7
    Location:
    Indiana
    I didn't take the time to read the article but it seems to me that KE would still be an important part of the equation with big expandables and larger game.

    Blessings...........Pastorjim
     
  15. roadrunner

    roadrunner Weekend Warrior

    Joined:
    Aug 16, 2014
    Posts:
    427
    Likes Received:
    24
    Dislikes Received:
    0
    It's no surprise to see a little science applied to one of the most popular and controversial topics in the modern bowhunting world. To say that KE has little to do with penetration is exactly that. It has little to do with penetration. The KE of an arrow is simply a representation of the amount of work the bow did on the arrow of mass to get it to a certain velocity. That's all it means. The bow has to do more work on an arrow of heavier mass than it does on a lighter arrow to get it to move. The "leftover" result is the responding velocity the arrow will have.

    To get a good appreciation of the relationship of momentum and kinetic energy, one needs to look at single variable (freshman) calculus. KE is really momentum with respect to a change in velocity over time, or mv(dv/dt). This gives the well known equation of 1/2mv[SUP]2[/SUP].
     
  16. TKP030

    TKP030 Weekend Warrior

    Joined:
    May 12, 2015
    Posts:
    575
    Likes Received:
    147
    Dislikes Received:
    1
    Location:
    North Dakota
    View attachment 66910
    View attachment 66911

    In short what the article entailed is that a 22lr has way more KE than an arrow since KE has more of importance on velocity that momentum where and in momentum weight has more pull. Images above
     
  17. remmett70

    remmett70 Die Hard Bowhunter

    Joined:
    Jul 13, 2015
    Posts:
    2,421
    Likes Received:
    394
    Dislikes Received:
    6
    Location:
    Rothschild, WI
    Neither the 900 or 350 grain arrow are going to get squat for penetration with a blunt tip.

    In the end, it is all balance. Want the arrow to be as fast as possible while still getting punch throughs.
     
  18. TKP030

    TKP030 Weekend Warrior

    Joined:
    May 12, 2015
    Posts:
    575
    Likes Received:
    147
    Dislikes Received:
    1
    Location:
    North Dakota
    The article clearly states where a good broad head is also very important. Just showing that often KE can be misinterpreted.
     
  19. Tacksman

    Tacksman Newb

    Joined:
    Mar 11, 2014
    Posts:
    20
    Likes Received:
    0
    Dislikes Received:
    0
    Location:
    America
    Interesting read. Thanks for sharing.
     
  20. Bowsage

    Bowsage Weekend Warrior

    Joined:
    Feb 3, 2016
    Posts:
    294
    Likes Received:
    60
    Dislikes Received:
    3
    Location:
    Virginia
    KE is just a number. It has very little to do with movement ( penetration) of an object.
     

Share This Page