Kinetic Energy question

[azle]

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[JimPic]

The lighter faster arrow will still have more energy down range.

Wrong...goes against the laws of physics

[Straight Shooter]

Well, here we go again. I agree a lighter arrow will lose energy faster BUT if its is starting out with more energy than a heavier arrow. Depending on how much, mind you. Then even though it still loses more energy it's still got more energy than the heavier arrow when it hits the target. Physics or not, I could care less about it. I have done this with the same setup, two different arrows weighing different, shot at the same speed all the way out to 40 yards through a chrono and the lighter arrow still had more energy than the heavier but the heavier had lost less.

Try it some time, physics don't play a whole into it, just accuracy when you are shooting through a chrono at 40 yards.:jaw:

Swampy, if you hit a pig with a sharp broadhead with a 60 pound draw bow, you definately kill it and should get a pass through. I'm sure the K.E. police will correct me on this.:nono:

[Tink]

You got more than enough KEwe have dozens of kids & little girls Texas killing boars with 30 & 35# bows Here is a hog I got recently when I was guiding some wounded solders on a boar bowhunt It Went about # 180 dressed out at 120# and produced 71 3 of fresh pork. I used a 50# PSE SSD and Axis 340 arrows with the New F 15 6 Blade 100 grain BH fixed BH The shot was a tad back and the hog only went 40 yards i shot it at 20 yards. I can post a pix of the hog maybe some expert here can produce a pix of the f 15 fixed 6 blade BH You are good to go TINK NATHAN

[m gardner]

KE is a good measure of how much work the arrow can do. Linear momentum will tell you how difficult it is to slow it down and stop it. A 50 pound bow with a 400 grain arrow will definitely get the job done. Sixty is even better. Have fun killing your pig!

Mark

[stcif]

I love these discussions. My physics education ended after high school, therefore I am no expert. I do understand the extreme basics though/

I believe the guy who understands this stuff the best is Dr. Ed Ashby. I suggest anyone intersted in penetration read his stuff.

What I have found is that most guys I know and shoot with are more concerned with speed, poundage and KE than anything else. Why is that? Well I believe it is that way because that is what the industry pushes to sell products.

I have been experimenting with different weight arrows for the past year or so. I am shooting a 500 grain arrow out of my 60 pound Diamond Liberty. The only downfall to heavier arrows in my opinion is they are not as flat shooting. More guess work on yardage and more pins. That cost me a deer last year as I was shooting 580 grain arrow. I'm still learning.

Light and fast is just not the way I am shooting anymore.

KE doesn't mean a heck of a lot when it comes to penetration. Kinetic pulse is a better measurement to go by. Kinetic pulse charts can be found in the book "Traditional Bowyer, More Unecessary Fun".

If KE and speed was extremely important regarding penetration, people shooting large game such as cape buffalo wouldn't be shooting 900 grain arrows at 85 pounds. Why not shoot a lighter arrow at blazing speeds at the buffalo? It wouldn't penetrate.

Thank you Dr. Ashby for answering a lot of questions. Your hard work is appreciated.

From what I have seen, light fast set ups work on deer most of the time because of good shot placement. How many times though does that arrow fail to penetrate? Dr. Ashby reminds us something to the effect of, our setups should be able to handle worst case scenarios.

I have also noticed my heavier arrows simple fly like darts. FOC is at 16%. When I go to a 250 broadhead/insert combo, it jumps to over 25%. It's been fun learning and experimenting.

Good luck on the boar hunt! One of my dream hunts.

[sskybnd]

whats enough kn to make a pass threw, going to a shoot sunday and i cant shoot over 285fps, my bow was shooting 297fps and my arrow only weighs 260grains and my bow was set at 68 lbs my kn was 50.92 kn now its at 46.90 and the bow set at 59lbs its a whole lot easier to draw back and hold for some time, just wondering if i could keep it at such for hunting also.

[stcif]

whats enough kn to make a pass threw, going to a shoot sunday and i cant shoot over 285fps, my bow was shooting 297fps and my arrow only weighs 260grains and my bow was set at 68 lbs my kn was 50.92 kn now its at 46.90 and the bow set at 59lbs its a whole lot easier to draw back and hold for some time, just wondering if i could keep it at such for hunting also.

I do not know what KE you need for a pass through. I do not think it makes sense to ask a question phrased like that. I have been told that a kinetic pulse of 500 is needed to break the shoulder bone of a deer. KP is different than KE. My KP charts start with a 350 grain arrow. A 350 grain arrow at 285 fps give a KP of 899.37. In order for my set up to generate a KP of about 900 I would have to shoot my 500 grain arrow 225 fps.

260 grain arrow is very light. I'd say worry less about the speed and shoot a heavier arrow.

The traditional shooters are using heavy arrows, some 600, 700, 800 grains at speeds well under 200 fps. Low KE, but the arrows zip right through the animals. Why?? Because kinetic pulse is more a function of momentum, which is affected more by arrow mass, than speed.

Edited March 20, 2010 by stcif

[sskybnd]

i like my arrows, there high country speed pro's and can be shot at 70 lbs, i had 4 pass threws with them this year but that was at 68lbs and 50 lbs of ke now the bow has less draw weight and less ke and was aking if 4 lbs of ke will make that much of a difference.

[Diamond Archer 01]

i like my arrows, there high country speed pro's and can be shot at 70 lbs, i had 4 pass threws with them this year but that was at 68lbs and 50 lbs of ke now the bow has less draw weight and less ke and was aking if 4 lbs of ke will make that much of a difference.

I don't know.

[Tink]

Not to the deer

Its far better to hit with 40# of KE than Miss with 90# of KE

TINK

[elkoholic]

A razor sharp broadhead placed precisely (in the right spot) will do the job if launched from any modern compound set at greater than 30 pounds. The whole kinetic energy versus momentum issue is quite interesting to discuss, but the end results on an actual hunt is all that matters. Personally, I like to think of it this way; Would you rather get hit by a baseball going 100+ mph or a bowling ball going 10+ mph? Most bow hunters would be better off shooting a heavier arrow at slower speeds but the speed demon in us all screams out for more velocity. Faster speeds do help in long range shooting and/or misjudgements in distance from intended target, but have inherent accuracy issues and increased bow vibration (newer bows are designed to eleviate that) as the bow itself has to absorb much of the energy that a heavier (slower) arrow would have absorbed.

[Tony]

Ken i killed my Boar in tenn with my bow set at 62 lbs. the arrows were around 375 gr at that time. you wont have any problems at all.

Tony