Title: 2 arrows of different mass but the same KE = same penetration????
Post by: ozy clint on March 08, 2010, 10:21:00 PM
Post by: ozy clint on March 08, 2010, 10:21:00 PM
is it possible to have 2 identical arrows, differing only in mass, that have the same KE, yet they penetrate exactly the same amount.
apparently some guy has the backing of NASA on this. ?????
any rocket scientist out ther who can share their view?
i don't completely understand so what's going on here?
apparently some guy has the backing of NASA on this. ?????
any rocket scientist out ther who can share their view?
i don't completely understand so what's going on here?
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: lpcjon2 on March 08, 2010, 10:26:00 PM
Post by: lpcjon2 on March 08, 2010, 10:26:00 PM
George,George,George we need you...LOL IMO It would have to be done in an extremely controlled environment,And the target would have to be identical,the draw,ect. in every way I doubt that it could be done.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Longbow338 on March 08, 2010, 10:30:00 PM
Post by: Longbow338 on March 08, 2010, 10:30:00 PM
Hard to argue with physics.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: vermonster13 on March 08, 2010, 10:31:00 PM
Post by: vermonster13 on March 08, 2010, 10:31:00 PM
Backing by NASA? Were they shooting in space? :p
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Orion on March 08, 2010, 10:41:00 PM
Post by: Orion on March 08, 2010, 10:41:00 PM
From what I understand about all the stuff that's been bandied about re kinetic energy and momentum on this siute, it would be possible to get the same KE out of two arrows of different mass by varying the speed. However, the different mass of the arrows would yield different momentum results (and momentum, being the better predictor of penetration in critters, according to Dr. Ed's research), the heavier mass arrow would penetrate more than the other.
I'm certainly not a rocket scientist, but that's my story and I'm sticking to it. What does NASA know about arrows anyway. Arrows aren't rocket science. :bigsmyl:
I'm certainly not a rocket scientist, but that's my story and I'm sticking to it. What does NASA know about arrows anyway. Arrows aren't rocket science. :bigsmyl:
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Tater on March 08, 2010, 10:48:00 PM
Post by: Tater on March 08, 2010, 10:48:00 PM
Foghorn Leghorn
Quote " It's mathmatechics son, you can't argue with mathmatechics!"
Quote " It's mathmatechics son, you can't argue with mathmatechics!"
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: ozy clint on March 09, 2010, 02:57:00 AM
Post by: ozy clint on March 09, 2010, 02:57:00 AM
that's what i figured orion.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: lpcjon2 on March 09, 2010, 09:58:00 AM
Post by: lpcjon2 on March 09, 2010, 09:58:00 AM
If NASA has the money and time to do that, what the heck is next!Testing the G Force and resistance and KE that a sperm encounters when leaving the ----- well you know what I mean.Federal dollars at work.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Buckeye Trad Hunter on March 09, 2010, 10:21:00 AM
Post by: Buckeye Trad Hunter on March 09, 2010, 10:21:00 AM
QuoteOriginally posted by Orion:Couldn't be said better. Force equals mass times velocity, therefore a heavier arrow at the same speed cannot have the same penetration. If this guy has NASA backing him we need to end our space programs.
From what I understand about all the stuff that's been bandied about re kinetic energy and momentum on this siute, it would be possible to get the same KE out of two arrows of different mass by varying the speed. However, the different mass of the arrows would yield different momentum results (and momentum, being the better predictor of penetration in critters, according to Dr. Ed's research), the heavier mass arrow would penetrate more than the other.
I'm certainly not a rocket scientist, but that's my story and I'm sticking to it. What does NASA know about arrows anyway. Arrows aren't rocket science. :bigsmyl:
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Ragnarok Forge on March 09, 2010, 11:55:00 AM
Post by: Ragnarok Forge on March 09, 2010, 11:55:00 AM
The testing could be done and it actually would not be that hard to set up and run the testing. There are so many factors in penetration and the two different arrows that I can say the odds of both penetrating the same are about as likely as me convincing my wife I need another boat to add to my boat collection.
Is it possible, you bet, it is likely, not at all. KE is not a measure of penetration, never has been, never will be. KE is the measure of energy stored in the arrow during flight. Impulse determines penetration. KE is just numbers used by the industry to sell fast bows.
It sounds to me like another industry wonk who worked a test or worked the date to find some numbers to prove a point they wanted proved. I wouldn't believe anything they are saying until I saw a report with testing data and the signature of someone you can identify as a rocket scientist. That way I could look over the report and determine if their assumptions, math, and testing all support their thesis and conclusions.
Pretty much I am call bunk on this one without some proof. Possible yes, probably no.
George, where are ya man? I think you and I singing the same tune for once.
Is it possible, you bet, it is likely, not at all. KE is not a measure of penetration, never has been, never will be. KE is the measure of energy stored in the arrow during flight. Impulse determines penetration. KE is just numbers used by the industry to sell fast bows.
It sounds to me like another industry wonk who worked a test or worked the date to find some numbers to prove a point they wanted proved. I wouldn't believe anything they are saying until I saw a report with testing data and the signature of someone you can identify as a rocket scientist. That way I could look over the report and determine if their assumptions, math, and testing all support their thesis and conclusions.
Pretty much I am call bunk on this one without some proof. Possible yes, probably no.
George, where are ya man? I think you and I singing the same tune for once.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: ChuckC on March 09, 2010, 12:55:00 PM
Post by: ChuckC on March 09, 2010, 12:55:00 PM
Ozy I am gonna guess that you will never encounter that in the real world. If they are truley identical in all things except mass they are not gonna pass thru the shoulder blade of a wildebeast at the same exact level.
ChuckC :knothead:
ChuckC :knothead:
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: ChuckC on March 09, 2010, 12:56:00 PM
Post by: ChuckC on March 09, 2010, 12:56:00 PM
actually, your statement is a bit vague. HOW MUCH difference are we speaking of ?
ChuckC
ChuckC
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Longbow338 on March 09, 2010, 03:12:00 PM
Post by: Longbow338 on March 09, 2010, 03:12:00 PM
Has anybody seen video in sponsor classifieds where the 150 gr head blew through two bull scapulas while the heavier heads penetrated one and stuck in the other. Still not an identical shot because certain parts of the bone are thicker than others but will make you think.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Jeff Strubberg on March 09, 2010, 03:33:00 PM
Post by: Jeff Strubberg on March 09, 2010, 03:33:00 PM
It's more likely that two arrows of different mass and the same KE would show differnet levels of penetration.
KE is a pretty good measure of how well you can get a projectile going, but for my money momentum is a much better predictor of how they will stop.
KE is a pretty good measure of how well you can get a projectile going, but for my money momentum is a much better predictor of how they will stop.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: McDave on March 09, 2010, 04:59:00 PM
Post by: McDave on March 09, 2010, 04:59:00 PM
Obviously, the real world adds a lot of variables that are difficult to account for, so probably a simple formula such as MV, or MV(squared) is not going to give you the correct answer. But I'm sure that if you had an old water buffalo carcass and shot a 600 grain arrow into it at 180 fps, you would be able to find arrow speeds at which a 500 grain arrow would penetrate less than, equal to, or more than the 600 grain arrow.
You up for that, Clint?
You up for that, Clint?
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Buckeye Trad Hunter on March 09, 2010, 07:27:00 PM
Post by: Buckeye Trad Hunter on March 09, 2010, 07:27:00 PM
I miss read. I mistook the KE for speed. As stated before the KE has no bearing on penetration. However a formula such as f=mv will 100% give you the correct answer. A 600gr. arrow @ 180 fps will penetrate better than a 500gr. arrow @ 180 fps. We're not talking about what if I hit a shoulder on a cape buffalo. If that happens you're gonna get poor penetration no matter what.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Brook Trout on March 09, 2010, 08:22:00 PM
Post by: Brook Trout on March 09, 2010, 08:22:00 PM
Yes, Force equals mass x velocity, but that is not the only factor in penetration. Other factors such as broadhead sharpness and arrow material determine resistance after impact. So yeah a heavy arrow with say a dull broadhead may penetrate the same as a light arrow with a sharp broadhead. Thats why its important to have your heads sharp.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: ArkyBob on March 09, 2010, 08:31:00 PM
Post by: ArkyBob on March 09, 2010, 08:31:00 PM
Man when I read these kind of threads, my head starts hurting. I think I'll go drink a glass of muscadine wine!!!!!
BOB
BOB
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Richie Nell on March 09, 2010, 08:44:00 PM
Post by: Richie Nell on March 09, 2010, 08:44:00 PM
"Man when I read these kind of threads, my head starts hurting. I think I'll go drink a glass of muscadine wine!!!!!"
DITTO
...and I think I will dull my broadheads and shoot an UNtuned arrow. Nothing is a given anymore.
DITTO
...and I think I will dull my broadheads and shoot an UNtuned arrow. Nothing is a given anymore.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Don Stokes on March 09, 2010, 08:57:00 PM
Post by: Don Stokes on March 09, 2010, 08:57:00 PM
A swallow cannot carry a coconut. However, TWO swallows...
The single most important factor in penetration is a tuned bow and arrow, regardless of mass, KE, momentum, single or double bevel, angle of fletching, or anything else we can dream up. A perfectly flying arrow will penetrate well. An imperfectly flying arrow will not. Everything else is window dressing.
Please pass the wine.
The single most important factor in penetration is a tuned bow and arrow, regardless of mass, KE, momentum, single or double bevel, angle of fletching, or anything else we can dream up. A perfectly flying arrow will penetrate well. An imperfectly flying arrow will not. Everything else is window dressing.
Please pass the wine.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: raideranch on March 09, 2010, 09:02:00 PM
Post by: raideranch on March 09, 2010, 09:02:00 PM
The two variables that effect KE are mass and velocity. The heavier arrow will have more mass but less velocity. The lighter arrow will have less mass but more velocity. If you plotted the KE for both these arrows at different ranges somewhere on the graph the lines would cross. At that point (which will relate to a certain range) the KE would be the same for both arrows. If both the arrows are arriving at that range with the same amount of energy (KE) with everything else being equal (broadhead, arrow diameter, etc...) they will penetrate the same.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Brook Trout on March 09, 2010, 09:35:00 PM
Post by: Brook Trout on March 09, 2010, 09:35:00 PM
well put raideranch
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Jock Whisky on March 09, 2010, 10:29:00 PM
Post by: Jock Whisky on March 09, 2010, 10:29:00 PM
As the speed of a projectile increases, the resistance the target imparts to the projectile increases exponentially. For example if the speed of your projectile doubled (x2) the resistance of the target would increase by 4 times. It is not a straight line relationship. That is why your gas mileage goes for a crap as your vehicle speed increases.
So the faster your arrow goes, the more the target resistance increases.
The slower heavier arrow penetrates farther than the fast light arrow assuming they have the same KE, momentum, force whatever.
JW
So the faster your arrow goes, the more the target resistance increases.
The slower heavier arrow penetrates farther than the fast light arrow assuming they have the same KE, momentum, force whatever.
JW
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Richie Nell on March 09, 2010, 10:43:00 PM
Post by: Richie Nell on March 09, 2010, 10:43:00 PM
Jock,
"For example if the speed of your projectile doubled (x2) the resistance of the target would increase by 4 times"
If I have an 800 grain arrow going 150 fps and double that speed to 300 fps, are you saying that the penetration would not be as good because the faster arrow's resistance increased by 4 times?
"For example if the speed of your projectile doubled (x2) the resistance of the target would increase by 4 times"
If I have an 800 grain arrow going 150 fps and double that speed to 300 fps, are you saying that the penetration would not be as good because the faster arrow's resistance increased by 4 times?
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: jrchambers on March 09, 2010, 10:48:00 PM
Post by: jrchambers on March 09, 2010, 10:48:00 PM
now these tests could not be done with a crono right infront of the shooter as a heavyer object slowes slower than a lighter one. so if the ke is the same a foot from the bow at ten yards the heavyer one will have more ke. and i bet the tests were in some very consistant tofu like blob. no bone or hair hide tendons cartlidge.....
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: bowslinger on March 10, 2010, 01:07:00 AM
Post by: bowslinger on March 10, 2010, 01:07:00 AM
I am sorry Don, but swallows are non migratory.
Raiderranch, is it more likley that there may be a point where their momentums are equal, versus where their kinetic energy is equal?
I would assume if the arrows are the same except for mass, if there is a point where their momentums are equal, they will have very similar, if not the same penetration.
Raiderranch, is it more likley that there may be a point where their momentums are equal, versus where their kinetic energy is equal?
I would assume if the arrows are the same except for mass, if there is a point where their momentums are equal, they will have very similar, if not the same penetration.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: raideranch on March 10, 2010, 02:19:00 AM
Post by: raideranch on March 10, 2010, 02:19:00 AM
Bowslinger
Yes the two variables of momentum are mass and velocity which are the same two for KE. Two arrows of different mass and velocity could have very similar momentum through flight at all distances. The heavy arrow slows down faster but maintains its momentum through its mass while the lighter arrow maintains its momentum because it does not slow down as fast. The KE for these two arrows will not be paired as well as momentum over a range of distances because velocity has a greater effect on KE than mass does where they have equal effects on momentum. You can see from the equations that velocity is squared for KE which means it has more effect on KE than does mass. For momentum they have equal effects.
KE (kinetic energy) = .5 x mass x velocity²
P (momentum) = mass x velocity
Yes the two variables of momentum are mass and velocity which are the same two for KE. Two arrows of different mass and velocity could have very similar momentum through flight at all distances. The heavy arrow slows down faster but maintains its momentum through its mass while the lighter arrow maintains its momentum because it does not slow down as fast. The KE for these two arrows will not be paired as well as momentum over a range of distances because velocity has a greater effect on KE than mass does where they have equal effects on momentum. You can see from the equations that velocity is squared for KE which means it has more effect on KE than does mass. For momentum they have equal effects.
KE (kinetic energy) = .5 x mass x velocity²
P (momentum) = mass x velocity
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: ozy clint on March 10, 2010, 02:42:00 AM
Post by: ozy clint on March 10, 2010, 02:42:00 AM
raider- i can't see how two arrows of unequal mass but of equal KE can penetrate the same. the lighter, hence faster arrow encounters more resistance. even if their momentum was the same. isn't that right?
or am i confused?
or am i confused?
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: raideranch on March 10, 2010, 03:34:00 AM
Post by: raideranch on March 10, 2010, 03:34:00 AM
Ozy
I'm no physicist I just took Physics I and II as an undergrad a couple years ago and understand some of the basic principles. I assumed they would penetrate the same because regardless of speed if they arrive at the target with the same KE both arrows will be transferring the same amount of energy to the target (so the tissue is absorbing the same amount of energy) unless the arrows pass through in which the rest of the energy is going to be transferred to whatever the arrows hit next. In this range of velocity the difference in resistance likely insignificant. Brook Trout is an Engineer he probably has a better answer.
I'm no physicist I just took Physics I and II as an undergrad a couple years ago and understand some of the basic principles. I assumed they would penetrate the same because regardless of speed if they arrive at the target with the same KE both arrows will be transferring the same amount of energy to the target (so the tissue is absorbing the same amount of energy) unless the arrows pass through in which the rest of the energy is going to be transferred to whatever the arrows hit next. In this range of velocity the difference in resistance likely insignificant. Brook Trout is an Engineer he probably has a better answer.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: James Wrenn on March 10, 2010, 07:11:00 AM
Post by: James Wrenn on March 10, 2010, 07:11:00 AM
Yeah Richie the fast arrows will bounce off stuff.I am sure you have read that around here before. !["[dntthnk]"]("graemlins/dntthnk.gif" "\"\"")
;)
;)
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: TheFatboy on March 10, 2010, 08:08:00 AM
Post by: TheFatboy on March 10, 2010, 08:08:00 AM
Not sure if I'm just stating the obvious here, but if you have not read Dr. Ashby's study on this, here it is:
http://tradgang.com/ashby/Momentum%20Kinetic%20Energy%20and%20Arrow%20Penetration.htm
I've gotten a lot smarter just by reading this!
http://tradgang.com/ashby/Momentum%20Kinetic%20Energy%20and%20Arrow%20Penetration.htm
I've gotten a lot smarter just by reading this!
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Don Stokes on March 10, 2010, 08:30:00 AM
Post by: Don Stokes on March 10, 2010, 08:30:00 AM
Bowslinger, I was referring to African swallows, of course.
A basic flaw in the whole premise- Arrows that are not the same mass are not identical. They may be the same diameter, the same length, the same color, but performance during flight will not be the same by any measurement you choose to use. Heavier arrows leave the bow more slowly than lighter arrows, but at some point the faster arrows will slow to the same speed as the heavier arrows due to air resistance, and beyond that point the heavier arrow will be faster until the target is reached.
The answer to the question is predicated on the variables, and there are too many variables for a realistic evaluation.
A basic flaw in the whole premise- Arrows that are not the same mass are not identical. They may be the same diameter, the same length, the same color, but performance during flight will not be the same by any measurement you choose to use. Heavier arrows leave the bow more slowly than lighter arrows, but at some point the faster arrows will slow to the same speed as the heavier arrows due to air resistance, and beyond that point the heavier arrow will be faster until the target is reached.
The answer to the question is predicated on the variables, and there are too many variables for a realistic evaluation.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Jeremy on March 10, 2010, 08:51:00 AM
Post by: Jeremy on March 10, 2010, 08:51:00 AM
I'll play :)
Looking at just one moment, presumably just before impact and assuming that KE1=KE2
If a 500gr arrow is traveling 180fps, a 600gr arrow will need to be traveling at 165fps to have the same KE.
That same 600gr arrow will have 10% more momentum at that point than the lighter, faster arrow.
Going up to a 700gr arrow, it will need to be traveling at 152fps, giving it 18% more momentum than the light arrow.
Read through the Ashby link above, it does a good job of explaining why momentum and not KE is the better penetration indicator.
Looking at just one moment, presumably just before impact and assuming that KE1=KE2
If a 500gr arrow is traveling 180fps, a 600gr arrow will need to be traveling at 165fps to have the same KE.
That same 600gr arrow will have 10% more momentum at that point than the lighter, faster arrow.
Going up to a 700gr arrow, it will need to be traveling at 152fps, giving it 18% more momentum than the light arrow.
Read through the Ashby link above, it does a good job of explaining why momentum and not KE is the better penetration indicator.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Richie Nell on March 10, 2010, 09:16:00 AM
Post by: Richie Nell on March 10, 2010, 09:16:00 AM
QuoteYeah Richie the fast arrows will bounce off stuff.I am sure you have read that around here before.Not if it is also heavy. But what do I know I haven't shot enough light or heavy arrows to make a post.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: James Wrenn on March 10, 2010, 09:44:00 AM
Post by: James Wrenn on March 10, 2010, 09:44:00 AM
Just kidding of course Richie. :) I don't but the 4 times resistance for twice the speed thing myself.The bottom line none of this stuff matters much at all.Everything we shoot if it is legal and tuned well will put an arrow out the other side of the critters we hunt if we shoot them in there sides instead of there butts. :readit:
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Richie Nell on March 10, 2010, 10:16:00 AM
Post by: Richie Nell on March 10, 2010, 10:16:00 AM
I absolutely agree.
I have always really known that really heavy bows/arrows are not necessary for whitetail. But due to hunters like yourself, I have become more and more a believer in the ability of the lighter weight weapons with the proper educated hunter behind it.
but in the mean time..
Hello...my name is Richie ...(hi richie)..
I just have this perfectionist sydrome problem
that creates an uncontrollable urge to use a heavy bow, arrow and fist.
WOW...I feel so much better. It's a new day.
I have always really known that really heavy bows/arrows are not necessary for whitetail. But due to hunters like yourself, I have become more and more a believer in the ability of the lighter weight weapons with the proper educated hunter behind it.
but in the mean time..
Hello...my name is Richie ...(hi richie)..
I just have this perfectionist sydrome problem
that creates an uncontrollable urge to use a heavy bow, arrow and fist.
WOW...I feel so much better. It's a new day.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Jeff Strubberg on March 10, 2010, 01:25:00 PM
Post by: Jeff Strubberg on March 10, 2010, 01:25:00 PM
QuoteOriginally posted by Richie Nell:Nope. If you increse that speed and lower the weight to the point that KE was equal, then the lighter arrow would not penetrate as well.
Jock,
"For example if the speed of your projectile doubled (x2) the resistance of the target would increase by 4 times"
If I have an 800 grain arrow going 150 fps and double that speed to 300 fps, are you saying that the penetration would not be as good because the faster arrow's resistance increased by 4 times?
Of course if you apply more energy to accelerate the same weight projectile to a higher speed, it's going to penetrate better.
Heavier arrows equal more momentum. Assuming a constant amount of energy at launch (i.e. the same bow and draw), more projectile weight is the best way to increase both momentum and penetration. The longer we can carry a high amount of energy without increasign drag, the more penetration we will get.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Jock Whisky on March 10, 2010, 11:01:00 PM
Post by: Jock Whisky on March 10, 2010, 11:01:00 PM
Richie
I'll try to explain a little clearer.
You have two arrows absolutely identical except in weight.
Both arrows are shot so they develop the identical KE, momentum, force, whatever. This means the light one would be moving faster and the heavy one would be moving slower.
The heavy one would penetrate farther, all things other than weight and speed being equal. This is because the target resistance increased as the lighter one went faster.
Does this mean you have to shoot 700 grain arrows to kill an animal??? Absolutely not. However I use heavy arrows for all my hunting because I want the best chance for maximum penetration. That's the choice I made FOR ME after studying Ashby's work. Someone earlier said something about "fast arrows in the hands of an educated archer". Nothing wrong with that. Use the info in Ashby's report to make a decision that works for you.
JW
JW
I'll try to explain a little clearer.
You have two arrows absolutely identical except in weight.
Both arrows are shot so they develop the identical KE, momentum, force, whatever. This means the light one would be moving faster and the heavy one would be moving slower.
The heavy one would penetrate farther, all things other than weight and speed being equal. This is because the target resistance increased as the lighter one went faster.
Does this mean you have to shoot 700 grain arrows to kill an animal??? Absolutely not. However I use heavy arrows for all my hunting because I want the best chance for maximum penetration. That's the choice I made FOR ME after studying Ashby's work. Someone earlier said something about "fast arrows in the hands of an educated archer". Nothing wrong with that. Use the info in Ashby's report to make a decision that works for you.
JW
JW
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: jrchambers on March 10, 2010, 11:12:00 PM
Post by: jrchambers on March 10, 2010, 11:12:00 PM
quote from page 2 "The heavy arrow slows down faster but maintains its momentum through its mass while the lighter arrow maintains its momentum because it does not slow down as fast. "
corect me if im wrong but this is wrong, two arows different weight, same ke right off the bow, the heavyer one has more momentum, does momentum not equal speed retentoin?
ive done quite a bit of reloading ammo and two slugs with the exact same balistic coeficient, basicly arowdinamics, but different weights fired at the same speed are not equal in trajectory. the heavyer one slowes slower.
so these two arows asuming same diamiter and length will have the same ke only for a given distance, im not saying the heavyer one would ever catch up but if the shot could continue for a imposible lenght before gravity took over completly the heavy one might catch and pass the lighter faster arow.
corect me if im wrong but this is wrong, two arows different weight, same ke right off the bow, the heavyer one has more momentum, does momentum not equal speed retentoin?
ive done quite a bit of reloading ammo and two slugs with the exact same balistic coeficient, basicly arowdinamics, but different weights fired at the same speed are not equal in trajectory. the heavyer one slowes slower.
so these two arows asuming same diamiter and length will have the same ke only for a given distance, im not saying the heavyer one would ever catch up but if the shot could continue for a imposible lenght before gravity took over completly the heavy one might catch and pass the lighter faster arow.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: raideranch on March 11, 2010, 12:04:00 AM
Post by: raideranch on March 11, 2010, 12:04:00 AM
jrchambers
No, regardless of KE or momentum, fired at the same angle the faster arrows will have the flatter trajectory and will travel further. Both arrows are falling at the same speed but the faster one will cover more ground before it hits. Theoretically, if you shoot a bullet horizontal to the ground and at that exact moment drop a bullet at the same height of the barrel they will both hit the ground at the same time. They are falling at the same speed (9.8 m/s²) but the bullet shot from the gun is moving in both the horizontal and vertical directions as it is falling.
No, regardless of KE or momentum, fired at the same angle the faster arrows will have the flatter trajectory and will travel further. Both arrows are falling at the same speed but the faster one will cover more ground before it hits. Theoretically, if you shoot a bullet horizontal to the ground and at that exact moment drop a bullet at the same height of the barrel they will both hit the ground at the same time. They are falling at the same speed (9.8 m/s²) but the bullet shot from the gun is moving in both the horizontal and vertical directions as it is falling.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: jrchambers on March 11, 2010, 12:20:00 AM
Post by: jrchambers on March 11, 2010, 12:20:00 AM
raideranch i agree with that completly, i was saying in a fantisy world where gravity doesnt play just friction from the air that the heavy one would decelerate slower and in theory catch up. this could never really happen,
look at it this way two arrows different weight, same speed and angle, they both will hit the ground at the same exact time but the heavy one will travel further due to the greater retained momentum, penetration is limited by friction as is trajectory, more mass = more momentum wich friction effects slower.
I hope you understand my ramble
hey ani gravity arows would be nice though
look at it this way two arrows different weight, same speed and angle, they both will hit the ground at the same exact time but the heavy one will travel further due to the greater retained momentum, penetration is limited by friction as is trajectory, more mass = more momentum wich friction effects slower.
I hope you understand my ramble
hey ani gravity arows would be nice though
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: raideranch on March 11, 2010, 12:26:00 AM
Post by: raideranch on March 11, 2010, 12:26:00 AM
Yea I understand what you're saying and that's why I like heavier arrows. Heavy arrows are more stable because it takes more force to move them off path.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Richie Nell on March 11, 2010, 12:30:00 AM
Post by: Richie Nell on March 11, 2010, 12:30:00 AM
The lighter, faster arrow may travel a longer distance in a given time but upon resistence (including air, target, deer) it will slow quicker than the heavier arrow resulting in less penetration. Even though the heavy arrow starts slower, its mass allows it to keep moving upon resistence resulting in better penetration.
That is why Mass is King...not speed.
If you are in a traffic accident...do you want to be in a Prius or a Landcruiser?
That is why Mass is King...not speed.
If you are in a traffic accident...do you want to be in a Prius or a Landcruiser?
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Ragnarok Forge on March 11, 2010, 12:37:00 AM
Post by: Ragnarok Forge on March 11, 2010, 12:37:00 AM
A law of physics states that a body in motion tends to stay in motion. The same law / principle applies to the fact that a heavier body will stay in motion longer than a lighter body when they meet equal resistance. Pretty simple answer to the question. Physicists already solved it for us.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: raideranch on March 11, 2010, 12:45:00 AM
Post by: raideranch on March 11, 2010, 12:45:00 AM
"when they meet equal resistance"
True, but if the lighter arrow arrives at the target faster there is less time for the "resistance" (gravity, wind, etc...) to act on it so do they have equal resistances?
True, but if the lighter arrow arrives at the target faster there is less time for the "resistance" (gravity, wind, etc...) to act on it so do they have equal resistances?
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Richie Nell on March 11, 2010, 01:02:00 AM
Post by: Richie Nell on March 11, 2010, 01:02:00 AM
Probably wrong here but excluding the target at the end of flight, I would think the lighter arrow would have less actual resistence flying (time wise) but affected more as in slowing faster. The heavy arrow would have more resistence (time wise) but affected less because of its mass.
Oh boy. I'm clueless.
Oh boy. I'm clueless.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: jrchambers on March 11, 2010, 03:40:00 AM
Post by: jrchambers on March 11, 2010, 03:40:00 AM
as far as wind goes the faster would have less resistance. and the longer the arow is in flight the more gravity affects, but i dont know if gravity is resistance,
now as far as O2 friction i would tend to think that regardles of speed the same amount of friction would aply to each arow over a equal distance travled. regardles of how fast or slow a arow travles through the air it still has to travel through the same amount, excluding wind.
just a thought what if speed did create more friction, like a piece of sandpaper drug across a board fast then slow with the same pressure, the faster it is moved the more heat is created wich is a indicator of friction.
now as far as O2 friction i would tend to think that regardles of speed the same amount of friction would aply to each arow over a equal distance travled. regardles of how fast or slow a arow travles through the air it still has to travel through the same amount, excluding wind.
just a thought what if speed did create more friction, like a piece of sandpaper drug across a board fast then slow with the same pressure, the faster it is moved the more heat is created wich is a indicator of friction.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: ozy clint on March 11, 2010, 04:09:00 AM
Post by: ozy clint on March 11, 2010, 04:09:00 AM
jrchambers- you just contradicted yourself.
sure the two arrows pass through the same amount of air but the faster one encounters more air resistance. that's why the fast sand paper creates more heat even with the same pressure as the slow sand paper.
sure the two arrows pass through the same amount of air but the faster one encounters more air resistance. that's why the fast sand paper creates more heat even with the same pressure as the slow sand paper.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Jeff Strubberg on March 11, 2010, 09:58:00 AM
Post by: Jeff Strubberg on March 11, 2010, 09:58:00 AM
It's a law of physics that doubling speed produces four times the resistance. That applies equally to arrows or airplanes.
Also, that law applies regardless of whether you are travelling through air or a game animal.
Also, that law applies regardless of whether you are travelling through air or a game animal.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: jrchambers on March 11, 2010, 02:10:00 PM
Post by: jrchambers on March 11, 2010, 02:10:00 PM
oh so i did, well done quite a bit of thinking about the origonal question, i belive the answer would be no they could not penetrate equal. If the lighter arow was 550 going 190 right off the bow and the other was 650 going 180, thats a diference of 10fps right off of the bow, and say just for giggles there KE is the same, I know its not in that scenario but when they hit a target at 20 yards the difference in speed is not going to be 10fps it would be less I dont know how much but the KE of the heavy one would be greater. to have the same KE at the point of impact would reqire a bit more from the lighter arow at the bow and then once more resistance hits the two arows the lighter one would loose speed, KE, and momentum even faster then when in flight,
just the way i see it
just the way i see it
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Don Stokes on March 12, 2010, 12:37:00 PM
Post by: Don Stokes on March 12, 2010, 12:37:00 PM
Unless it was a very small coconut, I think it would probably take at least FOUR African swallows...
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: ChuckC on March 12, 2010, 12:43:00 PM
Post by: ChuckC on March 12, 2010, 12:43:00 PM
Jr I am guessing that the faster arrow likely has the higher KE, since the speed factor is squared.
All this and what did we decide ? Will either arrow fill a deer ?
ChuckC
All this and what did we decide ? Will either arrow fill a deer ?
ChuckC
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: ChuckC on March 12, 2010, 12:44:00 PM
Post by: ChuckC on March 12, 2010, 12:44:00 PM
Jr I am guessing that the faster arrow likely has the higher KE, since the speed factor is squared.
All this and what did we decide ? Will either arrow kill a deer ?
ChuckC
All this and what did we decide ? Will either arrow kill a deer ?
ChuckC
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Jason R. Wesbrock on March 12, 2010, 01:12:00 PM
Post by: Jason R. Wesbrock on March 12, 2010, 01:12:00 PM
QuoteOriginally posted by Don Stokes:It could grip it by the husk. :D
Unless it was a very small coconut, I think it would probably take at least FOUR African swallows...
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: raideranch on March 12, 2010, 02:08:00 PM
Post by: raideranch on March 12, 2010, 02:08:00 PM
"It's a law of physics that doubling speed produces four times the resistance"
This has been posted like 10 time but we aren't talking about doubling the speed. We're on only talking about increasing it 10-15 fps at the most in a hunting arrow. This "law of physics" doesn't apply at all velocities.
This has been posted like 10 time but we aren't talking about doubling the speed. We're on only talking about increasing it 10-15 fps at the most in a hunting arrow. This "law of physics" doesn't apply at all velocities.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Guru on March 12, 2010, 02:45:00 PM
Post by: Guru on March 12, 2010, 02:45:00 PM
After 4 pages, all this is proving...what? :biglaugh:
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: lpcjon2 on March 12, 2010, 03:09:00 PM
Post by: lpcjon2 on March 12, 2010, 03:09:00 PM
That we like to type about things that we will never be able to prove or find any facts to prove anything.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Jason R. Wesbrock on March 12, 2010, 03:18:00 PM
Post by: Jason R. Wesbrock on March 12, 2010, 03:18:00 PM
QuoteOriginally posted by Guru:That a few of us apparently watched too many Monty Python movies. :)
After 4 pages, all this is proving...what? :biglaugh:
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Mooseandbuck44 on March 12, 2010, 03:24:00 PM
Post by: Mooseandbuck44 on March 12, 2010, 03:24:00 PM
Here is a link where you can plug in arrow speed, weight, and other characteristics and it will generate arrow drop, speed, KE, and momentum at different distances:
http://home.att.net/~sajackson/ballistics.html
http://home.att.net/~sajackson/ballistics.html
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Jeff Strubberg on March 12, 2010, 04:54:00 PM
Post by: Jeff Strubberg on March 12, 2010, 04:54:00 PM
QuoteOriginally posted by raideranch:Uh, it applies at every velocity. It applies to arrows, apples and airplanes.
"It's a law of physics that doubling speed produces four times the resistance"
This has been posted like 10 time but we aren't talking about doubling the speed. We're on only talking about increasing it 10-15 fps at the most in a hunting arrow. This "law of physics" doesn't apply at all velocities.
As far as proving anything, nah. Just shooting the breeze...
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Guru on March 12, 2010, 04:58:00 PM
Post by: Guru on March 12, 2010, 04:58:00 PM
quote:
Originally posted by Jason R. Wesbrock:
quote:
Originally posted by Guru:
After 4 pages, all this is proving...what? :clapper:
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: ThePushArchery on March 12, 2010, 06:01:00 PM
Post by: ThePushArchery on March 12, 2010, 06:01:00 PM
I have been following this thread, and I am really enjoying the theories and thoughts, they are definitely making me think!
But what I have noticed is that there is a trend in everyone's thinking that Momentum is the better penetrating factor in comparing it to KE. (MxV vs. (½)MV2) I definitely agree with this theory, as I use momentum as my deciding factor in arrow design.
There is only one scenario being played out in everyone's thought process and which is setting KE equal between two non-equally weighted arrows AT THE TARGET.
But there is another scenario as well, setting momentum equal AT THE TARGET between two non-equally weighted arrows.
I do not have the answer, and this is the reason, b/c this conundrum is an inverse resulting problem. Bear with me here.
SETTING KE EQUAL AT THE TARGET:
- 500 gr arrow @ 146 ft/s
- KE = 533 x 10 to the 4th
- Mom = 73,000
Vs.
- 600 gr arrow @ 133.33 ft/s
- KE = 533 x 10 to the 4th
- Mom = 80,000
SETTING MOMENTUM EQUAL AT THE TARGET:
- 500 gr arrow @ 160 ft/s
- Mom = 80,000
- KE = 640 x 10 to the 4th
Vs.
- 600 gr arrow @ 133.33 ft/s
- Mom = 80,000
- KE = 533 x 10 to the 4th
So ignoring the units of measure, b/c that becomes a cumbersome task to do the unit conversions into standard KE and Momentum units the recap is as follows:
SETTING KE EQUAL AT THE TARGET:
- The heavier arrow has more momentum at the target than the lighter arrow. I would conclude that the heavier arrow would penetrate better.
SETTING MOMENTUM EQUAL AT THE TARGET:
- The lighter arrow has more kinetic energy than the heavier arrow. I would conclude that since momentum is the same, then the lighter arrow has the better ability to penetrate.
So the conclusion or the secondary question one must ask himself, and I do not have the answer to this question, would be as follows:
Shooting THE SAME BOW, and adjusting your arrow weight, which of the two variables (momentum or KE) would be the same or closer to each other than the other variable. Is it more realistic that momentum will have closer values AT THE TARGET, or will KE have closer values AT THE TARGET when comparing two non-equally weighted arrows. Whichever the two scenarios proves out with your bow and your arrow weights in comparison, would be the one to go with.
But to the original question, I do not believe that two arrows of the same KE but different weights will penetrate the same... No way.
Your thoughts?
But what I have noticed is that there is a trend in everyone's thinking that Momentum is the better penetrating factor in comparing it to KE. (MxV vs. (½)MV2) I definitely agree with this theory, as I use momentum as my deciding factor in arrow design.
There is only one scenario being played out in everyone's thought process and which is setting KE equal between two non-equally weighted arrows AT THE TARGET.
But there is another scenario as well, setting momentum equal AT THE TARGET between two non-equally weighted arrows.
I do not have the answer, and this is the reason, b/c this conundrum is an inverse resulting problem. Bear with me here.
SETTING KE EQUAL AT THE TARGET:
- 500 gr arrow @ 146 ft/s
- KE = 533 x 10 to the 4th
- Mom = 73,000
Vs.
- 600 gr arrow @ 133.33 ft/s
- KE = 533 x 10 to the 4th
- Mom = 80,000
SETTING MOMENTUM EQUAL AT THE TARGET:
- 500 gr arrow @ 160 ft/s
- Mom = 80,000
- KE = 640 x 10 to the 4th
Vs.
- 600 gr arrow @ 133.33 ft/s
- Mom = 80,000
- KE = 533 x 10 to the 4th
So ignoring the units of measure, b/c that becomes a cumbersome task to do the unit conversions into standard KE and Momentum units the recap is as follows:
SETTING KE EQUAL AT THE TARGET:
- The heavier arrow has more momentum at the target than the lighter arrow. I would conclude that the heavier arrow would penetrate better.
SETTING MOMENTUM EQUAL AT THE TARGET:
- The lighter arrow has more kinetic energy than the heavier arrow. I would conclude that since momentum is the same, then the lighter arrow has the better ability to penetrate.
So the conclusion or the secondary question one must ask himself, and I do not have the answer to this question, would be as follows:
Shooting THE SAME BOW, and adjusting your arrow weight, which of the two variables (momentum or KE) would be the same or closer to each other than the other variable. Is it more realistic that momentum will have closer values AT THE TARGET, or will KE have closer values AT THE TARGET when comparing two non-equally weighted arrows. Whichever the two scenarios proves out with your bow and your arrow weights in comparison, would be the one to go with.
But to the original question, I do not believe that two arrows of the same KE but different weights will penetrate the same... No way.
Your thoughts?
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: ScouterMike on March 12, 2010, 11:10:00 PM
Post by: ScouterMike on March 12, 2010, 11:10:00 PM
Good answer cpnhgnlngct to a simple physics question. Since a bow will give about the same KE to different weight arrows (actually a slight bit more as arrow weight increases) The answer to your secondary question is that the heavier arrow will always have greater momentum than a lighter arrow with the same KE and all else being equal will have greater penetration. Simple numbers.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: hybridbow hunter on March 13, 2010, 07:56:00 AM
Post by: hybridbow hunter on March 13, 2010, 07:56:00 AM
cpnhgnlngct,
This is a good question, but from the same bow you will never get , in the 8 to at least 20 gpp range, the same KE neither momentum, because any time you add weight to your arrow, you will increase both KE and momentum when you measure it in front of the bow.
Then,from the same bow, a heavier arrow (identically built than a lighter), will always out penetrate the lighter one because both KE and momentum are higher.
AT THE TARGET this heavier arrow will out penetrate even more than really close:
At 25 yds, air drag on the light arrow (if same length, fletch, and diameter...) will be higher than on the heavier arrow. So drop both in KE and in momentum AT THE TARGET from the same bow will be bigger with the lighter arrow, increasing the difference you had already in front of the bow and lead the heavier to out penetrate more.
In fact, the only advantage of a fast arrow, is that it will hit the target a little sooner than the heavier at hunting range.
This is a good question, but from the same bow you will never get , in the 8 to at least 20 gpp range, the same KE neither momentum, because any time you add weight to your arrow, you will increase both KE and momentum when you measure it in front of the bow.
Then,from the same bow, a heavier arrow (identically built than a lighter), will always out penetrate the lighter one because both KE and momentum are higher.
AT THE TARGET this heavier arrow will out penetrate even more than really close:
At 25 yds, air drag on the light arrow (if same length, fletch, and diameter...) will be higher than on the heavier arrow. So drop both in KE and in momentum AT THE TARGET from the same bow will be bigger with the lighter arrow, increasing the difference you had already in front of the bow and lead the heavier to out penetrate more.
In fact, the only advantage of a fast arrow, is that it will hit the target a little sooner than the heavier at hunting range.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: hybridbow hunter on March 13, 2010, 08:22:00 AM
Post by: hybridbow hunter on March 13, 2010, 08:22:00 AM
oops: on the lastsentence you should read
" In fact, the only advantage of a light arrow, is that it will hit the target a little sooner than the heavier at hunting range with quite flatter trajectory"
" In fact, the only advantage of a light arrow, is that it will hit the target a little sooner than the heavier at hunting range with quite flatter trajectory"
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Terry Green on March 13, 2010, 11:48:00 PM
Post by: Terry Green on March 13, 2010, 11:48:00 PM
The one most tuned to the bow....
And shot by the most accurate shooter with the smoothest release.
After all the discussion, THAT is your answer. :readit:
And shot by the most accurate shooter with the smoothest release.
After all the discussion, THAT is your answer. :readit:
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: ozy clint on March 14, 2010, 05:42:00 AM
Post by: ozy clint on March 14, 2010, 05:42:00 AM
i was just wondering if someone could prove this persons claim. seems no one can.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: hybridbow hunter on March 15, 2010, 07:33:00 AM
Post by: hybridbow hunter on March 15, 2010, 07:33:00 AM
It is difficult to "calculate" it but easy to offer an easy experience to the hunters we all are supposed to be.
Let's build exactly the same looking arrow, one 850 gr and 2nd 465gr.
If we shoot the first one from a 70+# top of the line recurve @ 28" we could get around 165 fps what is really close to the set up you used succesfully for your water buff hunts....
KE with that set up (165 fps- 850 gr arrow) is very close to 51.4 ft.lbs.
To get similar KE=51.4 with an arrow weighting 465 gr, we need something like 223 fps. With a trad bow it will be difficult unless you don't mind about life expectancy of the bow BUT with a Wheely bow rated 315-320 fps IBO, that is something you would get for...55 LBS @28".
Who will be brave enough to give a try for buff hunt with that 55 lbs wheely and 465 gr arrow??
:biglaugh:
Let's build exactly the same looking arrow, one 850 gr and 2nd 465gr.
If we shoot the first one from a 70+# top of the line recurve @ 28" we could get around 165 fps what is really close to the set up you used succesfully for your water buff hunts....
KE with that set up (165 fps- 850 gr arrow) is very close to 51.4 ft.lbs.
To get similar KE=51.4 with an arrow weighting 465 gr, we need something like 223 fps. With a trad bow it will be difficult unless you don't mind about life expectancy of the bow BUT with a Wheely bow rated 315-320 fps IBO, that is something you would get for...55 LBS @28".
Who will be brave enough to give a try for buff hunt with that 55 lbs wheely and 465 gr arrow??
:biglaugh:
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Jeff Strubberg on March 15, 2010, 09:17:00 AM
Post by: Jeff Strubberg on March 15, 2010, 09:17:00 AM
QuoteOriginally posted by Terry Green:In any reasonable weight range with any reasonable weight bow, this is your answer, folks.
The one most tuned to the bow....
And shot by the most accurate shooter with the smoothest release.
After all the discussion, THAT is your answer. :readit:
It's easy to get so wrapped up in which is "better" that we forget to ask which is enough.
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Don Stokes on March 15, 2010, 10:50:00 AM
Post by: Don Stokes on March 15, 2010, 10:50:00 AM
Maybe turkey season will offer some distraction from the winter doldrums...
Title: Re: 2 arrows of different mass but the same KE = same penetration????
Post by: Guru on March 15, 2010, 12:30:00 PM
Post by: Guru on March 15, 2010, 12:30:00 PM
QuoteOriginally posted by Don Stokes:I couldn't agree more :pray:
Maybe turkey season will offer some distraction from the winter doldrums...