K.E.
 

So what is your guys opinon on energy to kill a Whitetail
(pass thru)?

RE: K.E.
 

Um I guess I would go with a pass thru because if you can get a pass thru then you KE is good enough.

RE: K.E.
 

Well I haven't ever seen a study on what it takes to pass thru and animal but most studies recommend adequate KE to "kill" certain animals and they would be a minimum of 45 ft lbs for deer sized animals and 55 ft lbs for elk sized animals. That is not to say that animals cannot be successfully taken with less however, shot placement is crucial......

RE: K.E.
 

I've seen those figures too, Rob, and have to say it's total BS. Ifit were true, then nobody shooting a recurve or longbow of less than 55 pounds would ever kill a deer because they don't get that much KE. Back in the 60's, the most common draw weight for deer hunting was 45 pounds. A great many elk have been taken with 50 pound recurves.

I don't know what those guys doing the studies have been smoking when doing their work, but they were definitely in Neverneverland when they came up with those numbers.

How much energy you need depends on a whole mess of different factors.

What weight are the arrows you're shooting? Lighter arrows have to have more KE to get the job done than heavier ones.

What kind of broadhead is on them? Mechanicals have to have more KE to do the job than replaceable blade fixed heads. Replaceable blade fixed heads have to have more KE than 3-blade cut on contact heads. 3-blade cut on contact heads have to have more KE than 2-blade cut on contact heads. In all cases, heads with a larger cutting diameter have to have more KE than heads with a smaller diameter. You could even get into the length to width ratio too!

Are you shooting from the ground or from a treestand? An angled shot needs more KE to penetrate to the vitals than a straight on shot.

Anybody that tells you that you need X amount of KE to kill animal Y, without giving specific information on all the above is blowing smoke.

RE: K.E.
 

Aurthur, I couldn't agree with you more but that's the only figures available "per study", and I'd bet more than not it's all about compounds. You and I both know that a recurve/longbow shooting a heavy wooden arrow of the past not only killed deer but probably every bit or more efficiently than todays technological advancements and light arrows....


Like you said, my earlier study was true, it'd be near impossible to pass thru and animal with less and we know that is not true but like I said, it's about shot placement....and then woodsmanship.

RE: K.E.
 

It would depend on your broadhead and distance. KE is calculated at peak speed. The further out the less there is. Cut to tip, Fixed or mechanical require different KE. Because of all the variables I'd give you an answer of "Depends". If I was going with a fixed I'd say give me 50 for a passthrough at out to 30. For a mechanical, give me 60. Then again, it all depends on broadhead diameter.

RE: K.E.
 

My arrows have 67lbs comming out of the bow at 263fps.
Then at 60 yrd have 54 ft lb. With 100 gr 3 blade muzzys.

RE: K.E.
 

I have 74 ft. pounds @299
At 60 yards i have 56 ft.pounds

something is a bit fishy here[&:]

RE: K.E.
 

A little simple math give you the answer to your fishiness, newman.

Doing some back-figuring, D.Parsons is using a 436 gn arrow. Yours are 372 gns. Lighter arrows lose speed and energy at a much faster rate as they go downrange. At 60 yards, your 299 fps has dropped to 260 fps. Loss of 39 fps and 18 ft lbs of energy.

If you were to shoot a 436 gn arrow, your initial speed would drop to @ 286 fpsbut you'd wind up with an arrow doing something like 253 fps and carrying 62 ft lbs at 60 yards. A loss of only 23 fps and 12 ft lbs of energy. You'd have a trajectory very similar to what you've got now. It'd probably open your pin settings very slightly.

RE: K.E.
 

O.k. but not quite what i was refferring to.On the ballistic table from bojackson it tells me that at 0 yards i am going 299 fps and at 20 yards i am going 285 fps and the arrow drops 8 INCHES!!.My fishiness is that i know this not to be correct.There is no way my arrow drops 8 inches from 0-20 yards.It seems that the program is not to accurate or i did not give it the correct info,but i am sure i did.;)

RE: K.E.
 

I think the arrow drop info on Jackson's is about the mostimpractical info on his site. Worse than impractical, actually, because so many people wind up confusing arrow drop with trajectory.

Arrow drop is not the same as trajectory. Arrow drop is based on launching the arrow dead level with the ground. The arrow is at it's highest point at the bow and begins dropping the instant it clears the rest. If you did shoot the arrow dead level with the ground at 20 yards, it would indeed drop 8" in the time it takes to get there. (Pull of gravity is 35 feet per second, per second)

When you launch the arrow at an upward angleyou've put it on a trajectory.It rises up against the force of gravity, reaches a high point, then gravity starts pulling it backdown.Even shooting at 20 yards, you're launching the arrow on an upward angle. You aim the arrow upward to counteract the effect of gravity, to make the arrow fly upward, arc over, and dropinto the spot.

RE: K.E.
 

good reply, arther p
i want to make something clear here. i was shooting a 408 gr. arrow in 2004. when done on this site in sept. 1 in 2005 opener i was shooting a 565 gr. arrow at alot slower speeds. and yes there is a noticable pin gap. but the most differance is in the hunt. you better have your range finder in your hand.
here is what happened for me, sneak in on a herd of elk. just a cow and calf in the feild, the rest in the trees and moving. so i sit by a bush and wait. sure enough the cow walks by me at 42 yards, yes, i ranged the "green patch" and the creek was at 37 yards. anyway, the cow turns right to me 6-8 steps, then i draw, no wait she looking.....6 steps...draw and o.k. calm down ....42 yards to the "green patch"....twang...oh no right over her back. she leaves and yes i forgot she took 14-18 steps or in elk steps yards that would put her at 24-28 yards away.
and you know if i had still been shooting 408 gr. arrow at 270 fps. and close pins i would have hit the elk, a little high but those elk steaks sure would be good right now![:@]
so it all comes down to how you hunt, if you sit in a stand and only have 25 yard shots , then just shoot what is needed. if you are going to "run and gun" and may not have time to range every shot. then i like the lighter faster arrows.just my .02

RE: K.E.
 

I don't have the tech numbers, but a 73 lb hoyt ultratec, spiral cam, 29" draw, perfectly tuned bow , ST Axis arrows, tuned broadheads with 100 gr. thunderhead has yet to fail me. All pass thrus. Good enough?

This year, three shots, three eight points, all pass thrus. Any questions?:D

RE: K.E.
 

It should be understood that it is FORCE that is required to push an arrow through a deer not energy or momentum. We measure force in POUNDS. Now of course you can't have force without energy but it is still force that is required for any movement. As an example, you have a lot of energy in your muscles but until you use that energy to apply a FORCE to the string of your bow you can not PULL the string back. Just like it takes a FORCE to pull your bow string back it is force that is required to push a broadhead tipped arrow through the deer. How much depends on a lot of things but probably the most important of them to keep in mind is sharpness. A sharp broadhead requires much less force to push through than a dull one. You know this intuitively. Now KE and momentum are values that tell us about how the force can be applied. KE tells us about HOW FAR (distance), momentum tells us for HOW LONG (time). For example 50 foot pounds of KE means that a FORCE of 50 pounds can be applied over a DISTANCE of 1 foot. Or if you'd rather 100 pounds over 1/2 foot. 50 pound seconds of momentum means that a FORCE of 50 pounds can be applied over a TIME of 1 second. Or again if you'd rather 100 pounds for 1/2 second.

So lets look at a real example of an arrow in flight. Let's take a 397.5 grain arrow moving at 238 ft/sec. KE calculates to be 50 ft/lbs and momentum is 0.42 pound seconds. Now lets say that arrow strikes an object that is absolutely uniform in its consitency and given the sharpness of the arrow and frictional resistence and all that complicated stuff it winds up requiring 50 POUNDS of force to push the arrow into the object. How far will it penetrate? The answer is 50 foot pounds divided by 50 pounds = 1 foot. How long will it take? Well if the arrow has 0.42 pound seconds of momentum it will take 0.42 pound seconds divided by 50 pounds = 0.0084 seconds. Notice the literal common denominator is pounds or force.

So KE told us that a 397.5 grain arrow traveling 238 ft/sec will come to a stop in an object that resists the arrows movement with 50 pounds of continuous force in a DISTANCE of 1 foot.
Momentum told us that a 397.5 grain arrow traveling 238 ft/sec will come to a stop in an object that resists the arrows movement with 50 pounds of continuous force in a TIME of 0.0084 seconds.

But keep in mind, FORCE is what is required to make something happen whether it is to draw your string back, launch an arrow or bring an arrow to a stop. NOTHING starts or stops without a FORCE being applied. You can think of KE and momentum as nothing more than measures of how far or for how long can you apply the force.

Now finally to the question. Answer .... It's a trick question! No really, there is no precise answer to this question. There are a whole lot of assumptions that have to be rolled up in any answer before you can even begin. So many, I don't think it even makes sense to start. But think about this. When you pull your string back think about the force and "feel" the force you are using as you draw it back and then think about applying that same force on an arrow "pushing" the arrow with a sharp broadhead on it into a deer. Now think about doubling that force. Minus some efficiency losses (say 20% or so) that will give you a very rough feel for the potential penetrating force you have to push the arrow through the deer.
Did I make any sense whatsoever?
P.S.
[If you're curious about why I said think about "doubling" the force... I used double because the distance through a deer (broadside) is roughly a little less than 1/2 the power stroke on a bow of a typical archer. Sorry but without writing a book on this and boring everyone further, I can't explain it any better. Hope I shed just a little light and mabe gave a little different way of thinking about this and didn't confuse everyone]

RE: K.E.
 

sad thing is iactully understood this...but basically every thing he just said idhave to agree with. Honestly i dont now why you would have to worry about it too much, cuase you dont have to have a pass though to kill a deer yeah im sure it help to find them but i have found both of mine and neither passed completely though, the BH did but not the entire arrow,,also one thing i found out is that with little poundage bow it is better to shot heavy arrows cuase they will penetrate deeper, just my .10

RE: K.E.
 

Right on the money PSEsilverhawk55, all things being equal, heavier arrows shot from the same bow will indeed penetrate deeper. The reason is that bows transfer energy from the limbs to heavier arrows more efficiently than they do to lighter arrows, therefore there is more KE/momentum in the arrow in flight and therefore carry a greater potential to apply the FORCE necessary to push the arrow into/through the deer. I also agree totally that unless you are shooting a bow with "little poundage" it just isn't anything to worry about. Just keep your bow tuned, shoot a sharp broadhead and most important PRACTICE! I think captain backstrap summed it up pretty well!