KE vs Momentum
06-14-2004, 03:23 PM
#21
Nontypical Buck
Join Date: Feb 2003
Location:
Posts: 2,994
RE: KE vs Momentum
Check this thread on AT out.
Full frontal shot on African Big Game-
http://www.archerytalk.com/vb/showth...threadid=88679
Wow. Skin on a Giraffe is 1" LESS thick at the front than broadside. That's some seriously thick skin. I can only imagine what a cape buff or rhino have...
Full frontal shot on African Big Game-
http://www.archerytalk.com/vb/showth...threadid=88679
Wow. Skin on a Giraffe is 1" LESS thick at the front than broadside. That's some seriously thick skin. I can only imagine what a cape buff or rhino have...
06-14-2004, 05:27 PM
#22
Nontypical Buck
Thread Starter
Join Date: Feb 2003
Location: Arlington TX USA
Posts: 2,214
RE: KE vs Momentum
Thanks for the formula Arthur. I've been playing around on BowJackson's website and I am checking the momentium not only at the bow, but also at 20 & 30 yards. I am not as concerned with the values at ranges farther than that since I have a self imposed limit of 30 yards for a shot on a deer.
06-14-2004, 06:20 PM
#23
Join Date: Dec 2003
Posts: 127
RE: KE vs Momentum
BPS,
Your ultralight, super duper high speed theory is going to get you no where here.
I am going to side with Arthur. If you didn't get the pass thru's with the heavy set ups, at slower speed, than check your tune, broadhead, or form.
A compromise of KE, and momentum is the key.
Your ultralight, super duper high speed theory is going to get you no where here.
I am going to side with Arthur. If you didn't get the pass thru's with the heavy set ups, at slower speed, than check your tune, broadhead, or form.
A compromise of KE, and momentum is the key.
06-14-2004, 07:38 PM
#24
Nontypical Buck
Join Date: Feb 2003
Location: CT, USA
Posts: 3,058
RE: KE vs Momentum
I really don't want to get into this..but I can't keep my big trap shut..
But I will keep it short and sweet. 
(yeah..right!)
IMO, Momentum should be emphasized (and is KEY) in 2 set-ups
1) where energy (however you want define it) is low i.e. many traditional set-ups, low poundage, shorter draw lengths softer cams/wheels, etc. In those cases, I believe Momentum is much more critical. You want a pretty heavy shaft and fixed blades of some sort to maximize energy and penetration down-range.
2) BIG and/or "dangerous" Game. i.e. Moose, Buffs, the bigger African/Asian/Australian game species, etc. Where you need every bit of "leverage" you can get.
Though we hear tales of the lady pulling 36 pounds who has a 24" draw on an old round wheel bow who shot completey through a Moose with a a 2 inch cut 5 blade mech, I think in those cases, there was a lot of luck invoved and exceedingly good shot placement...neither of which we can always guarantee due to circumstances beyon our control. It's best to plan for the worst..not the best.
On most modern bows shooting fairly light to medium weight arrows at very good speeds, tipped with a stout broadhead of whatever make you prefer, KE is an acceptable benchmark, and momentum becomes less critical unless you are shooting very long bowhunting ranges (i.e. 40-60 yards) for something like Elk, Caribou, big Canadian whitetails, Big muleys, etc where that arrow is coming back into orbit and losing alot of energy.
On deer sized game I feel the point of whether KE or momentum is more important is a moot one. Except in scenario 1 above.
From my experience shaft diameter does provide an advantage in penetration (as well as windrift and less velocity decay) compared to the larger diameter alums with similar (or even lighter in the case of carbon) weights,energy, & broadhead design (many of the old PC style arrows were not exactly light in most cases by the time you glue adapters, older heavier vanes, and a 100-125 grain head on them). And I also agree with BPS regarding shaft flex. While I have no scientific proof, it is only reasonable to assume that carbon will act the same way on game it hits as it does in inanimate targets. Aluminum bends around like a noodle upon impact..while the softer nature of hide, flesh and ribs may not make for as much shaft oscillation as a foam target, It makes no logical sense that the phenomenon is completely suppressed/negated going from one target medium to the next.
Bow tune is another key factor as I'm sure we all know, and a whole 'nother can o' worms.
Regardless...I suspect this topic, like Singles Vs. Duals vs. Hybrids, Mechs vs. Chisel, vs. Cut to the tip, Open Camo vs. Blend camo. and other similar topics are really only topics of argument started years ago to get us from one season to the next on the message boards and are hardly relevant whatsoever!
But I will keep it short and sweet. (yeah..right!)IMO, Momentum should be emphasized (and is KEY) in 2 set-ups
1) where energy (however you want define it) is low i.e. many traditional set-ups, low poundage, shorter draw lengths softer cams/wheels, etc. In those cases, I believe Momentum is much more critical. You want a pretty heavy shaft and fixed blades of some sort to maximize energy and penetration down-range.
2) BIG and/or "dangerous" Game. i.e. Moose, Buffs, the bigger African/Asian/Australian game species, etc. Where you need every bit of "leverage" you can get.
Though we hear tales of the lady pulling 36 pounds who has a 24" draw on an old round wheel bow who shot completey through a Moose with a a 2 inch cut 5 blade mech, I think in those cases, there was a lot of luck invoved and exceedingly good shot placement...neither of which we can always guarantee due to circumstances beyon our control. It's best to plan for the worst..not the best.
On most modern bows shooting fairly light to medium weight arrows at very good speeds, tipped with a stout broadhead of whatever make you prefer, KE is an acceptable benchmark, and momentum becomes less critical unless you are shooting very long bowhunting ranges (i.e. 40-60 yards) for something like Elk, Caribou, big Canadian whitetails, Big muleys, etc where that arrow is coming back into orbit and losing alot of energy.
On deer sized game I feel the point of whether KE or momentum is more important is a moot one. Except in scenario 1 above.
From my experience shaft diameter does provide an advantage in penetration (as well as windrift and less velocity decay) compared to the larger diameter alums with similar (or even lighter in the case of carbon) weights,energy, & broadhead design (many of the old PC style arrows were not exactly light in most cases by the time you glue adapters, older heavier vanes, and a 100-125 grain head on them). And I also agree with BPS regarding shaft flex. While I have no scientific proof, it is only reasonable to assume that carbon will act the same way on game it hits as it does in inanimate targets. Aluminum bends around like a noodle upon impact..while the softer nature of hide, flesh and ribs may not make for as much shaft oscillation as a foam target, It makes no logical sense that the phenomenon is completely suppressed/negated going from one target medium to the next.
Bow tune is another key factor as I'm sure we all know, and a whole 'nother can o' worms.
Regardless...I suspect this topic, like Singles Vs. Duals vs. Hybrids, Mechs vs. Chisel, vs. Cut to the tip, Open Camo vs. Blend camo. and other similar topics are really only topics of argument started years ago to get us from one season to the next on the message boards and are hardly relevant whatsoever!
06-14-2004, 08:03 PM
#25
Nontypical Buck
Join Date: Feb 2003
Location: In Teh Garage (Rossville, GA USA)
Posts: 1,161
RE: KE vs Momentum
Your ultralight, super duper high speed theory is going to get you no where here.
I am going to side with Arthur. If you didn't get the pass thru's with the heavy set ups, at slower speed, than check your tune, broadhead, or form.
I am going to side with Arthur. If you didn't get the pass thru's with the heavy set ups, at slower speed, than check your tune, broadhead, or form.
I dont give a rat who you side with, It aint about sides
It is about you cannot put a mathematical equation on a stiff arrow.
Use what gives you the best results and I will do the same
06-15-2004, 06:29 AM
#26
Giant Nontypical
Join Date: Feb 2003
Posts: 9,175
RE: KE vs Momentum
Jeff, it is NOT reasonable to assume an arrow reacts the same way when it hits flesh as it does when it hits an inanimate object, like a target.... unless it hits solid bone, like the ball and socket in the shoulder, and immediately slams to a dead stop.
On a broadside hit where the arrow knicks a couple of ribs, it's not going to have much resistance. An arrow going a mere 200 fps when it hits a deer is going to whip through the deer in about .008 of a second, assuming a 20" wide ribcage. Doesn't give that arrow much time to flex, does it. By the time the arrow could react to the impact, it's already through the deer and gone.
Talk about small diameter and friction. What's the difference in friction between a carbon arrow with stiff plastic vanes and a 2419 wearing feathers? The carbon shaft is smaller and, naturally, has less friction, but those vanes! The 2419 has more surface area and more friction on the shaft, but those feathers slide right through. Prove it to yourself. Grab the shaft of a vane fletched arrow and pull the fletching through your closed fist. Then do the same with a feather fletched arrow.
I agree about momentum/KE being over-argued. Like I said, you don't have one without the other. Like YOU said, with a high performance bow you can stack up a pile of KE and do well. On the other hand, while you're stacking up that KE with speed, you're also stacking up the momentum. That's why a high KE arrow will penetrate. Not so much because of the energy but because it's also carrying a lot of momentum. Don't take my word for it. Do the math!
It's easier and quicker to pile on the momentum with arrow weight than it is to get it with speed, but you do get it with speed. Still, momentum is the key, as far as I'm concerned.
Where I get my dander up is when KE snobs start saying you must have X amount of KE in order to ethically hunt such and such animals. Not only are they operating with a false premise, their BS is dangerous to youth, women, disabled and traditional hunters, who cannot shoot high poundage bows or whose bows cannot churn out gobs of KE. Momentum is a much better indicator and is easily achievable for most people.
Lets assume for a moment that my suggested minimum of .33 pound seconds of momentum is a good figure. I don't know that it is, but lets assume... That is achieveable with a 500 gn arrow at 149 fps and 25 ft lbs KE. - ie. a 50 pound selfbow. Or a 400 gn arrow at 186 fps, 31 ft lbs - ie. a 12 year old with his youth compound. I don't like the idea of using less than a 400 gn arrow for hunting so I won't figure for a lighter arrow.
Those low KE setups will do the job BUT, you have to have make intelligent choices in arrow selection, broadhead selection and shot selection. You have to have the bow well tuned. You have to execute the shot properly and place the arrow accurately.
Of course, those same choice and performance issues are imperative no matter whether you're shooting a wimpy rig or a mongo rig. It's easy for the hunter to blame the arrow for his failure, even though it's hunter's fault because he chose the wrong arrow to begin with.
On a broadside hit where the arrow knicks a couple of ribs, it's not going to have much resistance. An arrow going a mere 200 fps when it hits a deer is going to whip through the deer in about .008 of a second, assuming a 20" wide ribcage. Doesn't give that arrow much time to flex, does it. By the time the arrow could react to the impact, it's already through the deer and gone.
Talk about small diameter and friction. What's the difference in friction between a carbon arrow with stiff plastic vanes and a 2419 wearing feathers? The carbon shaft is smaller and, naturally, has less friction, but those vanes! The 2419 has more surface area and more friction on the shaft, but those feathers slide right through. Prove it to yourself. Grab the shaft of a vane fletched arrow and pull the fletching through your closed fist. Then do the same with a feather fletched arrow.
I agree about momentum/KE being over-argued. Like I said, you don't have one without the other. Like YOU said, with a high performance bow you can stack up a pile of KE and do well. On the other hand, while you're stacking up that KE with speed, you're also stacking up the momentum. That's why a high KE arrow will penetrate. Not so much because of the energy but because it's also carrying a lot of momentum. Don't take my word for it. Do the math!
It's easier and quicker to pile on the momentum with arrow weight than it is to get it with speed, but you do get it with speed. Still, momentum is the key, as far as I'm concerned.
Where I get my dander up is when KE snobs start saying you must have X amount of KE in order to ethically hunt such and such animals. Not only are they operating with a false premise, their BS is dangerous to youth, women, disabled and traditional hunters, who cannot shoot high poundage bows or whose bows cannot churn out gobs of KE. Momentum is a much better indicator and is easily achievable for most people.
Lets assume for a moment that my suggested minimum of .33 pound seconds of momentum is a good figure. I don't know that it is, but lets assume... That is achieveable with a 500 gn arrow at 149 fps and 25 ft lbs KE. - ie. a 50 pound selfbow. Or a 400 gn arrow at 186 fps, 31 ft lbs - ie. a 12 year old with his youth compound. I don't like the idea of using less than a 400 gn arrow for hunting so I won't figure for a lighter arrow.
Those low KE setups will do the job BUT, you have to have make intelligent choices in arrow selection, broadhead selection and shot selection. You have to have the bow well tuned. You have to execute the shot properly and place the arrow accurately.
Of course, those same choice and performance issues are imperative no matter whether you're shooting a wimpy rig or a mongo rig. It's easy for the hunter to blame the arrow for his failure, even though it's hunter's fault because he chose the wrong arrow to begin with.
06-15-2004, 07:09 AM
#27
Nontypical Buck
Join Date: Feb 2003
Location: CT, USA
Posts: 3,058
RE: KE vs Momentum
ORIGINAL: Arthur P
Jeff, it is NOT reasonable to assume an arrow reacts the same way when it hits flesh as it does when it hits an inanimate object, like a target.... unless it hits solid bone, like the ball and socket in the shoulder, and immediately slams to a dead stop.
Jeff, it is NOT reasonable to assume an arrow reacts the same way when it hits flesh as it does when it hits an inanimate object, like a target.... unless it hits solid bone, like the ball and socket in the shoulder, and immediately slams to a dead stop.
On a broadside hit where the arrow knicks a couple of ribs, it's not going to have much resistance. An arrow going a mere 200 fps when it hits a deer is going to whip through the deer in about .008 of a second, assuming a 20" wide ribcage. Doesn't give that arrow much time to flex, does it. By the time the arrow could react to the impact, it's already through the deer and gone.
Talk about small diameter and friction. What's the difference in friction between a carbon arrow with stiff plastic vanes and a 2419 wearing feathers? The carbon shaft is smaller and, naturally, has less friction, but those vanes! The 2419 has more surface area and more friction on the shaft, but those feathers slide right through. Prove it to yourself. Grab the shaft of a vane fletched arrow and pull the fletching through your closed fist. Then do the same with a feather fletched arrow.
I agree about momentum/KE being over-argued. Like I said, you don't have one without the other. Like YOU said, with a high performance bow you can stack up a pile of KE and do well. On the other hand, while you're stacking up that KE with speed, you're also stacking up the momentum. That's why a high KE arrow will penetrate. Not so much because of the energy but because it's also carrying a lot of momentum. Don't take my word for it. Do the math!
It's easier and quicker to pile on the momentum with arrow weight than it is to get it with speed, but you do get it with speed. Still, momentum is the key, as far as I'm concerned.
Where I get my dander up is when KE snobs start saying you must have X amount of KE in order to ethically hunt such and such animals. Not only are they operating with a false premise, their BS is dangerous to youth, women, disabled and traditional hunters, who cannot shoot high poundage bows or whose bows cannot churn out gobs of KE. Momentum is a much better indicator and is easily achievable for most people.
. Agreed, as I laid out in "scenario 1" in my intitial post, momentum indeed should be the determining factor. However the opposite is true as well...when a certain threshold is reached KE is just as viable a means as momentum..the problem is defining where that threshold is. We can argue 'til we are blue in the face, but the game law makers have to make a distinction and go with what they feel is an adequate simple to use indicator. I agree though, it may very well be incorrect.
....BUT, you have to have make intelligent choices in arrow selection, broadhead selection and shot selection. You have to have the bow well tuned. You have to execute the shot properly and place the arrow accurately.
Of course, those same choice and performance issues are imperative no matter whether you're shooting a wimpy rig or a mongo rig. It's easy for the hunter to blame the arrow for his failure, even though it's hunter's fault because he chose the wrong arrow to begin with.
Make no mistake Arthur, I'm not arguing with you. I just that I feel this is one of those cases where the line is blurry, and there are no hard and fast rules for everyone.
I agree with you on many of your points re: momentum, but I believe the amount of importance of certain factors and under what circumstances is where we will need to just agree to diasgree.Always fun though.
Glad to see ya back and in the groove
06-15-2004, 08:03 AM
#29
Nontypical Buck
Join Date: Feb 2003
Location: In Teh Garage (Rossville, GA USA)
Posts: 1,161
RE: KE vs Momentum
it is NOT reasonable to assume an arrow reacts the same way when it hits flesh as it does when it hits an inanimate object, like a target.... unless it hits solid bone, like the ball and socket in the shoulder, and immediately slams to a dead stop.
then please explain why those fat flemsy eastons would not penetrate thru the animal not hitting any bone I might add
and the lighter stiffer completley pass thru busting rib bone entering and exiting.
Please do not try to explain that my bow was not properly tuned.
your philosipher is exactley right it is not brain surgery nor is it rocket science.....
even common sence will tell you uncooked spageti will penetrate a potato and a limp noodle will not
you can believe what you want to
but you can bring your self to my little Pro shop down here in tennessee and I will proove it to you by shooting the arrows thru any type of medium you want that lighter, faster stiffer arrows will out penetrate
fat, heavy weak slow every time at any distance!
06-15-2004, 09:46 AM
#30
Nontypical Buck
Join Date: Feb 2003
Location: Heaven IA USA
Posts: 2,597
RE: KE vs Momentum
For me at least I think it is healthy to discuss KE & Momentum but I wouldn't argue with anybody over it. At a certain level I believe you start splitting hairs. Both have merit and both are tied indelibly to each other.
Bigpapascout back in the mid 90's I was using a setup where I shot a 2514 arrow. Compared to what some of my buddies were using they looked like telephone poles.
At any rate, I went back in my journals and looked at the results; here is what it showed. Using a 2514 arrow there were 11 kills (these were midwest and northern whitetails). Of those eleven deer harvested eight were complete pass throughs. The three where no pass through was acheived hit bone. Two hit the off shoulder and one connected with the spine.
For the last five years I have used carbon arrows. While I do think they penetrate better they also have been stopped at times by an off shoulder or spine.
Bigpapascout back in the mid 90's I was using a setup where I shot a 2514 arrow. Compared to what some of my buddies were using they looked like telephone poles.
At any rate, I went back in my journals and looked at the results; here is what it showed. Using a 2514 arrow there were 11 kills (these were midwest and northern whitetails). Of those eleven deer harvested eight were complete pass throughs. The three where no pass through was acheived hit bone. Two hit the off shoulder and one connected with the spine.
For the last five years I have used carbon arrows. While I do think they penetrate better they also have been stopped at times by an off shoulder or spine.