the momentum theory
Moderator: Moderators
the momentum theory
i have always had an intresest in the effective penetration discussions that go on forever and honestly believe the only real way to clearly display the facts is to place a compound shooter with the most commonly used hunting setup, say 500 gr arrows, alongside a trad shooter with 750 gr arrows, both shooting into foam to test penetration . most understand KE and can see the superior figures from the compound, but throw in the momentum issue that the heavy arrow fans speak of and it gets complicated, therefore requiring the previously mentioned foam test to display the real answers...perhaps i have too much time on my hands but today i thought of an example of how effective momentum is in achieving penetration.... if anyone has ever tried to drive a concrete nail into a slab with a standard claw hammer they will know that you can flog away wild and fast but it takes alot of effort and eventually gets there....a lump hammer or sledgehammer however gets it done with ease and in less time and effort. " a prime example of how the slower, heavier item is a better option"....i personally dont get into debate over these things cause i couldnt give a damn, if your out there hunting pigs and having a great time thats really all that matters. but i posted this should anyone ever have trouble explaining the momentum theory........ps...i shoot most boars in north qld with fat heavy hand planed woods shot from a hard cammed compound,penetration is well under control......russ
-
Dennis La Varenne
- Posts: 1776
- Joined: Sun Sep 07, 2003 10:56 pm
- Location: Tocumwal, NSW. Australia
Dear Russ,
It has been a very long time since the science of physics has defined momentum to have a specific meaning, ie that a body in motion (which is any kind of projectile) has a measurable amount of energy in the direction of travel.
Kinetic energy on the other hand is the measurable amount of energy in a body having any kind of motion in any direction.
Most people do not understand either definition. They are only more familiar with Kinetic energy and are impressed with the large numbers which accompany it without realising their significance.
The relevance of the two different definitions of projectile energy as they apply to archery in particular has been dealt with very well in the series of article written by Dr Ed Ashby (the Old Derelict) who writes in Archery Action.
Fundamentally, momentum is the more applicable for predicting how well an arrow will penetrate any kind of medium because it is the amount of energy at the pointy end of the arrow rather than the amount of energy which the whole arrow possesses anywhere along its length. That is the difference in simple terms.
The debate about the relative merit of either definition tends to degenerate into a compound vs tradbow argument. Compounders seem to believe that compounds shoot arrows which produce kinetic energy and tradbow shooters often believe they shoot bows which produce momentum. It is a profoundly silly argument and completely wrong on both counts.
It doesn't matter a whit what kind of bow you shoot, both categories shoot arrows which have measurable amounts of BOTH categories of energy. The point is - which is the more useful in predicting whether an arrow will give reliably lethal penetration on animals or how far it will penetrate into any given target material.
Remember, momentum is the amount of energy at the point of the arrow and not the amount of energy contained in the whole arrow which is kinetic energy. In other words,momentum is the amount of force behind the arrow which is directed at pushing it along a defined pathway.
Kinetic energy is what is seen when an arrow stops and vibrates, or heard when it hums or makes a slapping noise at the time of impact. The more the vibration or noise, the more kinetic energy. BUT, the further it sticks into the target, tree, animal, the more momentum it has.
So, it doesn't matter a fig what kind of bow you shoot, so long as you generate sufficient momentum in your arrows to obtain lethal penetration in the animals you hunt in a reliable fashion.
The nonsense given out by a lot of compounders who are mightily impressed by the enormous kinetic energy figures which they can calculate from the speed of their arrows is just that - nonsense and proves nothing except how much their arrows will wobble on impact.
As Ed Ashby shows in his articles, momentum is improved by increasing mass where both energy types are defined as Mass x Velocity (with a few qualifying factors thrown in). Kinetic energy is improved by increasing velocity.
However, at the other end of the trajectory of an arrow where the arrow is required to penetrate an object, it becomes more important to use an arrow which will produce a high level of momentum because as velocity increases, the toughness (resistance to penetration) of the object being struck increases with velocity in the proportion of the square of the velocity.
This principle is seen in every day life when some fool dives off a tall bridge into a river and hits the water like a brick and kills himself. Why? Because he accelerates at the rate of 10 metres per second squared and as he does so, at the instant he hits the water, its properties of resistance to impact by the water increase dramatically - hence the loud whack which is dispersing kinetic energy being given off by the fool's body at collision.
If he wanted to avoid injury, he should have dived from a lower postion.
It is the same with arrows. Shoot them faster and it gets harder to get them to penetrate unless you increase their mass.
If the arrows are lighter, they also lose velocity much more quickly as distances increase and arrive at the target with far lower levels of both kinds of energy than if the arrow is heavier.
When we tradbow shooters use very heavy arrows at moderate speed, you will calculate that these arrows often have quite high momentum figures, often matching or even exceeding the compounders using light arrows at high velocity. What they should be doing, and what you are correctly doing is making best use of the much higher energy storage ability inherent in compounds to launch heavy arrows to get both higher speed and momentum, especially downrange.
Heavy arrows at a given velocity slow down much more slowly than light arrows and hence retain a far higher amount of energy at the pointy end than lighter arrows at similar or often greater speed.
Two arrows of very different weights travelling at the same speed will cover the same distance in much the same time and have the same trajectory (Newton's laws on gravity). The lighter arrow will arrive at the target with very much less energy at the point of the arrow compared to the heavy arrow (mass x velocity). To have the same energy level at the arrow point (momentum) on impact, it will have to be launched at significantly higher velocity than the heavy arrow.
Kinetic energy is not useful in measuring the effectiveness of arrows because it is the amount of energy given off at impact in all directions. Kinetic energy is useful for bullets for this reason. We bowhunters need to shoot arrows with high momentum from whatever kind of bow we use because we need to have a reliable measure of pushing force (if I may refer to momentum that way) behind our arrows if we want them to penetrate the target animal reliably.
Momentum is the only reliable measure we have to predict how well an arrow will do this. Kinetic energy can only do this very indirectly because of the other factors affecting it.
Why the high velocity brigade seem to do as well as they do with their relatively light arrows is only because they are able to launch them at such high velocity that they are able to generate an adequate level of Momentum anyway. It has little to do with Kinetic energy. But, if they used the same arrows in a lighter bow producing lower velocities, their penetrating ability would fall off dramatically.
So the principle is that if you must shoot a bow of lighter draw weight for hunting make sure you increase your arrow weight, not decrease it for the sake of trajectory.
Dennis La Varenne
It has been a very long time since the science of physics has defined momentum to have a specific meaning, ie that a body in motion (which is any kind of projectile) has a measurable amount of energy in the direction of travel.
Kinetic energy on the other hand is the measurable amount of energy in a body having any kind of motion in any direction.
Most people do not understand either definition. They are only more familiar with Kinetic energy and are impressed with the large numbers which accompany it without realising their significance.
The relevance of the two different definitions of projectile energy as they apply to archery in particular has been dealt with very well in the series of article written by Dr Ed Ashby (the Old Derelict) who writes in Archery Action.
Fundamentally, momentum is the more applicable for predicting how well an arrow will penetrate any kind of medium because it is the amount of energy at the pointy end of the arrow rather than the amount of energy which the whole arrow possesses anywhere along its length. That is the difference in simple terms.
The debate about the relative merit of either definition tends to degenerate into a compound vs tradbow argument. Compounders seem to believe that compounds shoot arrows which produce kinetic energy and tradbow shooters often believe they shoot bows which produce momentum. It is a profoundly silly argument and completely wrong on both counts.
It doesn't matter a whit what kind of bow you shoot, both categories shoot arrows which have measurable amounts of BOTH categories of energy. The point is - which is the more useful in predicting whether an arrow will give reliably lethal penetration on animals or how far it will penetrate into any given target material.
Remember, momentum is the amount of energy at the point of the arrow and not the amount of energy contained in the whole arrow which is kinetic energy. In other words,momentum is the amount of force behind the arrow which is directed at pushing it along a defined pathway.
Kinetic energy is what is seen when an arrow stops and vibrates, or heard when it hums or makes a slapping noise at the time of impact. The more the vibration or noise, the more kinetic energy. BUT, the further it sticks into the target, tree, animal, the more momentum it has.
So, it doesn't matter a fig what kind of bow you shoot, so long as you generate sufficient momentum in your arrows to obtain lethal penetration in the animals you hunt in a reliable fashion.
The nonsense given out by a lot of compounders who are mightily impressed by the enormous kinetic energy figures which they can calculate from the speed of their arrows is just that - nonsense and proves nothing except how much their arrows will wobble on impact.
As Ed Ashby shows in his articles, momentum is improved by increasing mass where both energy types are defined as Mass x Velocity (with a few qualifying factors thrown in). Kinetic energy is improved by increasing velocity.
However, at the other end of the trajectory of an arrow where the arrow is required to penetrate an object, it becomes more important to use an arrow which will produce a high level of momentum because as velocity increases, the toughness (resistance to penetration) of the object being struck increases with velocity in the proportion of the square of the velocity.
This principle is seen in every day life when some fool dives off a tall bridge into a river and hits the water like a brick and kills himself. Why? Because he accelerates at the rate of 10 metres per second squared and as he does so, at the instant he hits the water, its properties of resistance to impact by the water increase dramatically - hence the loud whack which is dispersing kinetic energy being given off by the fool's body at collision.
If he wanted to avoid injury, he should have dived from a lower postion.
It is the same with arrows. Shoot them faster and it gets harder to get them to penetrate unless you increase their mass.
If the arrows are lighter, they also lose velocity much more quickly as distances increase and arrive at the target with far lower levels of both kinds of energy than if the arrow is heavier.
When we tradbow shooters use very heavy arrows at moderate speed, you will calculate that these arrows often have quite high momentum figures, often matching or even exceeding the compounders using light arrows at high velocity. What they should be doing, and what you are correctly doing is making best use of the much higher energy storage ability inherent in compounds to launch heavy arrows to get both higher speed and momentum, especially downrange.
Heavy arrows at a given velocity slow down much more slowly than light arrows and hence retain a far higher amount of energy at the pointy end than lighter arrows at similar or often greater speed.
Two arrows of very different weights travelling at the same speed will cover the same distance in much the same time and have the same trajectory (Newton's laws on gravity). The lighter arrow will arrive at the target with very much less energy at the point of the arrow compared to the heavy arrow (mass x velocity). To have the same energy level at the arrow point (momentum) on impact, it will have to be launched at significantly higher velocity than the heavy arrow.
Kinetic energy is not useful in measuring the effectiveness of arrows because it is the amount of energy given off at impact in all directions. Kinetic energy is useful for bullets for this reason. We bowhunters need to shoot arrows with high momentum from whatever kind of bow we use because we need to have a reliable measure of pushing force (if I may refer to momentum that way) behind our arrows if we want them to penetrate the target animal reliably.
Momentum is the only reliable measure we have to predict how well an arrow will do this. Kinetic energy can only do this very indirectly because of the other factors affecting it.
Why the high velocity brigade seem to do as well as they do with their relatively light arrows is only because they are able to launch them at such high velocity that they are able to generate an adequate level of Momentum anyway. It has little to do with Kinetic energy. But, if they used the same arrows in a lighter bow producing lower velocities, their penetrating ability would fall off dramatically.
So the principle is that if you must shoot a bow of lighter draw weight for hunting make sure you increase your arrow weight, not decrease it for the sake of trajectory.
Dennis La Varenne
Dennis La Varénne
Have the courage to argue your beliefs with conviction, but the humility to accept that you may be wrong.
QVIS CVSTODIET IPSOS CVSTODES (Who polices the police?) - DECIMVS IVNIVS IVVENALIS (Juvenal) - Satire VI, lines 347–8
What is the difference between free enterprise capitalism and organised crime?
HOMO LVPVS HOMINIS - Man is his own predator.
Have the courage to argue your beliefs with conviction, but the humility to accept that you may be wrong.
QVIS CVSTODIET IPSOS CVSTODES (Who polices the police?) - DECIMVS IVNIVS IVVENALIS (Juvenal) - Satire VI, lines 347–8
What is the difference between free enterprise capitalism and organised crime?
HOMO LVPVS HOMINIS - Man is his own predator.
Dennis,
Another brilliant reply and explanation of the principles of archery. It was one of the better explanations I have seen for KE versus momentum. I am glad we have someone of Dennis's knowledge on this forum. To explain complex principles in lay mans terms is a real art.
Russ, although I have not done the maths and worked out if it is physically correct, some one once gave this explanation between light and fast projectiles and slower but much heavier ones.
What would you rather be hit by a ping pong ball doing 120 km/h or a golf ball doing 60 km/h ?
Daryl
Another brilliant reply and explanation of the principles of archery. It was one of the better explanations I have seen for KE versus momentum. I am glad we have someone of Dennis's knowledge on this forum. To explain complex principles in lay mans terms is a real art.
Russ, although I have not done the maths and worked out if it is physically correct, some one once gave this explanation between light and fast projectiles and slower but much heavier ones.
What would you rather be hit by a ping pong ball doing 120 km/h or a golf ball doing 60 km/h ?
Daryl
- darn right!I am glad we have someone of Dennis's knowledge on this forum
And Dennis isn't the only one who really makes my day by writing a post like this. I want to thank all of you who take the time to clue us lesser mortals 
in on things. Fair Dinkum, it makes all the work of running a site like this worthwhile when I see this kind of post. Not that I don't get a kick out of all input - joking or whatever - but you (I hope) know what I mean 
vegie, the ping pong analogy is excellent! In the same way that, as Russ points out, the bridge jump is excellent. A picture worth a thousand words stuff.
Dennis, the thing I kept thinking about while reading your post was how critically important it is for a hunter to get an arrow to fly straight - at least when it arrives at target
thanks,
Erron
I agree with Erron about the straight arrows when they reach the target. I paper tune my hunting arrows, broadhead and all. People laugh and think this is just a bit obsessive but I think it makes a big difference when they hit. I was told recently that a well tuned arrow will penetrate as well as one with poor flight from a bow that is 10 -15 pounds heavier.
Apart from the increase in accuracy I get I never have had troubles with penetration. A mate who does the same thing shot through a scrub bull hitting a rib going in , the arrow passed through and stuck in a tree root so hard we could not get it out. bow was a 66 pound hoyt superslam. 2219 shaft and a javelin, not an overly high poundage set up in my opinion.
Many people practice with arrows and when they ding them or bend them they become hunting arrows. I go the other way, my bent shafts become my target arrows. If your arrows are not perfect and fly perfectly then you have just lost a great deal of energy and efficency, that could have been fixed with a few minutes work. Some people spend a fortune on their gear and hunting then cut corners on critical aspects like dead straight arrows and getting perfect arrow flight.
Arguements about KE or momentum are pretty trivial if when your arrow arrives energy is lost because the arrow is hitting sideways and not directing all its energy straight down the shaft. Sideways friction will in my opinion robs energy from a shaft quicker than anything.
Daryl
Apart from the increase in accuracy I get I never have had troubles with penetration. A mate who does the same thing shot through a scrub bull hitting a rib going in , the arrow passed through and stuck in a tree root so hard we could not get it out. bow was a 66 pound hoyt superslam. 2219 shaft and a javelin, not an overly high poundage set up in my opinion.
Many people practice with arrows and when they ding them or bend them they become hunting arrows. I go the other way, my bent shafts become my target arrows. If your arrows are not perfect and fly perfectly then you have just lost a great deal of energy and efficency, that could have been fixed with a few minutes work. Some people spend a fortune on their gear and hunting then cut corners on critical aspects like dead straight arrows and getting perfect arrow flight.
Arguements about KE or momentum are pretty trivial if when your arrow arrives energy is lost because the arrow is hitting sideways and not directing all its energy straight down the shaft. Sideways friction will in my opinion robs energy from a shaft quicker than anything.
Daryl
vegie, i too am obsessive about regular broadhead practice, so much so that i dont even own any arrows with target points on them. they are fine for testing form and target practice but the only way to be 100 % certain that your hunting arrows are flying straight, arriving at the target straight, grouping well and grouping where you want them to, is to shoot them, exactly as they will be shot from the bow in a hunting situation...when polystyrene foam is such a perfect, cheap, readily available broadhead target, theres no excuse for going afield wondering if our equip is going to be ok. the game deserves better. we must KNOW what that arrow is going to do as it leaves our bow.....like taking shots at game at unrealistic ranges, it ***** me that so many people dont take the time to be at one with their gear. its something that should be hammered into beginner bowhunters right from the start....russ
-
Stickbow Hunter
- Supporter
- Posts: 11637
- Joined: Sat Jul 26, 2003 8:33 pm
- Location: Maryborough Queensland
Russ wrote
The reason I say this is that the foam will grip - because of a huge amount of friction - onto the arrow shafts and stop them. Foam, as a medium, is completely different to an animal which is mainly soft tissue.
The foam for example might stop a wood shaft shot from a trad bow far quicker than it might stop a carbon or alloy arrow shot from a compound yet in soft tissue (game) the heavy wood arrow may out penetrate the light arrow by a considerable margin. Something to think about.
I also agree with Dennis's comments above.
Jeff
Not having a go at you Russ just wanting to point something out. IMO the sort of test above is a total waste of time for the purposes of comparing penetration. About the only thing it might prove is that the foam can stop an arrow.i have always had an intresest in the effective penetration discussions that go on forever and honestly believe the only real way to clearly display the facts is to place a compound shooter with the most commonly used hunting setup, say 500 gr arrows, alongside a trad shooter with 750 gr arrows, both shooting into foam to test penetration .
The reason I say this is that the foam will grip - because of a huge amount of friction - onto the arrow shafts and stop them. Foam, as a medium, is completely different to an animal which is mainly soft tissue.
The foam for example might stop a wood shaft shot from a trad bow far quicker than it might stop a carbon or alloy arrow shot from a compound yet in soft tissue (game) the heavy wood arrow may out penetrate the light arrow by a considerable margin. Something to think about.
I also agree with Dennis's comments above.
Jeff
-
Dennis La Varenne
- Posts: 1776
- Joined: Sun Sep 07, 2003 10:56 pm
- Location: Tocumwal, NSW. Australia
Dear all,
Thank you for the compliments. I try to explain things as simply as possible because it is obvious that a lot of what should be basic knowledge is often obscured by jargon. Careful use of analogies helps.
Both momentum and kinetic energy are alternative methods of measuring the same thing for different purposes.
If you strike a gong or bell, the ensuing vibration is kinetic energy given off as sound which our ears detect. Characteristically of kinetic energy, it is given off in all directions and if you applied a measuring device to the bell, you could take the measurement anywhere on its surface or near it.
But if you pushed the bell and it bumped against an object, you could only measure its momentum at the points where contact occurred.
ALL movement in flight apart from forward movement is a form of KE loss. As it loses KE, it loses velocity (mass remains constant unless bits of arrow are falling off) and therefore so is momentum or hitting energy if I can call it that.
KE is not really hitting energy in the same way that momentum is because it disperses in all directions in the form of sound, heat, vibrating movement etc. as the arrow (projectile) loses velocity or stops. It is also lost as heat with friction against the air.
We can regard momentum as hitting energy because it is the energy or force which arrives at the target (or animal) at the point of the broadhead.
This is where most people confuse the two. They think KE is the amount of force which hits at the point of the arrow. Clearly, it is not. Momentum is.
Stickbow's reference to the matter of using polystyrene is correct, but it has a use in comparing like with like, ie, two arrows of same material from a bow where only one variable is changed at at time so that the relative penetration between the two can be measured.
It will not correlate directly with impact on animal tissue which is mostly a bag of water (about 70%).
If you shoot at polystyrene, you can compare penetration of arrows thus -
1. heavy and light arrows where everything else is the same, including velocity;
2. higher and lower velocities where the arrow has the one mass;
3. arrows of the same mass and material shot at the same velocity, but with different broadheads;
and so forth in a systematic manner, tabulate the results and draw graphs from the data.
The amount of testing can go on forever if you are that keen, but all it will ever tell you is how well or not any combination of equipment will penetrate into a poly block.
However, if one combination penetrates further than the others, it is safe to assume that it will also penetrate better into animal tissue, but that is the limit of what you can deduce from this kind of testing.
BUT, and it is a very big BUT - none of the above is predictive of how well it will penetrate animal tissue to a humanely lethal degree. It can only predict which combination has higher momentum (where friction is already allowed for), and thus a greater chance of lethal penetration.
As Stickbowhunter pointed out, it is not a fair comparison to shoot a carbon or alloy arrow into a poly block and compare it with a wood having a varnish coating. Friction on the surface of the wood is very high. In fact, if you withdraw the wood arrow immediately after, you can sometimes feel heat on the part of the arrow which has penetrated the poly block (which is another way in which KE is dispersed) which often slightly melts the varnish so that poly sticks to it.
However, if you shoot any kind of arrow into a highly fluid medium such as animal tissue which has very high lubricating properties, you get a completely different result. The comparisons become more reasonable because one of the limiting factors (friction) has been reduced to be a fairly insignificant factor.
As I said earlier, we Tradbowmen are not against compound bows as such and never have been. We have always been against their misuse where their obvious and undoubted mechanical advantage in being able to propel very heavy arrows with enormous momentum is deliberately given up for flat trajectory and speed using light arrows of low mass and momentum.
Many of the compounders use sights anyway. This negates the problems of high arc trajectories once the pins have been set up. Whatever the distance, you only have to put the pin on the spot and trajectory is automatically taken care of, so there really is no excuse for this usual kind of bow misuse in hunting.
If you are shooting barebow you should be getting well within your point-blank range and then halving it at least if you have any hunting skill.
As I have said elsewhere - hunting is not target practice on live animals.
We are there to humanely kill them, not to see if our equipment is working as well as we would like it to. You do that elsewhere and if you cannot, you use equipment and techniques which have been proven down the ages to work, which you should be doing anyway.
As Russ expressed it in perhaps the most succinct way I have read for quite a while -
"theres no excuse for going afield wondering if our equip is going to be ok. the game deserves better. we must KNOW what that arrow is going to do as it leaves our bow.....like taking shots at game at unrealistic ranges".
Russ' use of the word 'KNOW' is instructive.
The issue of straight arrow flight is a proper topic of concern as most of you have pointed out, but my post was a discussion of momentum vs kinetic energy and how it applies to arrow efficiency.
For the purposes of the discussion, perfect arrow flight was taken as a given. But, as some of you have correctly pointed out, the benefit of high momentum is severely reduced if the arrow is ocillating in flight (another way in which KE lost), fishtailing or porpoising, or performing other aerial acrobatics.
I hope I have not further confused anyone.
Dennis La Varenne
Thank you for the compliments. I try to explain things as simply as possible because it is obvious that a lot of what should be basic knowledge is often obscured by jargon. Careful use of analogies helps.
Both momentum and kinetic energy are alternative methods of measuring the same thing for different purposes.
If you strike a gong or bell, the ensuing vibration is kinetic energy given off as sound which our ears detect. Characteristically of kinetic energy, it is given off in all directions and if you applied a measuring device to the bell, you could take the measurement anywhere on its surface or near it.
But if you pushed the bell and it bumped against an object, you could only measure its momentum at the points where contact occurred.
ALL movement in flight apart from forward movement is a form of KE loss. As it loses KE, it loses velocity (mass remains constant unless bits of arrow are falling off) and therefore so is momentum or hitting energy if I can call it that.
KE is not really hitting energy in the same way that momentum is because it disperses in all directions in the form of sound, heat, vibrating movement etc. as the arrow (projectile) loses velocity or stops. It is also lost as heat with friction against the air.
We can regard momentum as hitting energy because it is the energy or force which arrives at the target (or animal) at the point of the broadhead.
This is where most people confuse the two. They think KE is the amount of force which hits at the point of the arrow. Clearly, it is not. Momentum is.
Stickbow's reference to the matter of using polystyrene is correct, but it has a use in comparing like with like, ie, two arrows of same material from a bow where only one variable is changed at at time so that the relative penetration between the two can be measured.
It will not correlate directly with impact on animal tissue which is mostly a bag of water (about 70%).
If you shoot at polystyrene, you can compare penetration of arrows thus -
1. heavy and light arrows where everything else is the same, including velocity;
2. higher and lower velocities where the arrow has the one mass;
3. arrows of the same mass and material shot at the same velocity, but with different broadheads;
and so forth in a systematic manner, tabulate the results and draw graphs from the data.
The amount of testing can go on forever if you are that keen, but all it will ever tell you is how well or not any combination of equipment will penetrate into a poly block.
However, if one combination penetrates further than the others, it is safe to assume that it will also penetrate better into animal tissue, but that is the limit of what you can deduce from this kind of testing.
BUT, and it is a very big BUT - none of the above is predictive of how well it will penetrate animal tissue to a humanely lethal degree. It can only predict which combination has higher momentum (where friction is already allowed for), and thus a greater chance of lethal penetration.
As Stickbowhunter pointed out, it is not a fair comparison to shoot a carbon or alloy arrow into a poly block and compare it with a wood having a varnish coating. Friction on the surface of the wood is very high. In fact, if you withdraw the wood arrow immediately after, you can sometimes feel heat on the part of the arrow which has penetrated the poly block (which is another way in which KE is dispersed) which often slightly melts the varnish so that poly sticks to it.
However, if you shoot any kind of arrow into a highly fluid medium such as animal tissue which has very high lubricating properties, you get a completely different result. The comparisons become more reasonable because one of the limiting factors (friction) has been reduced to be a fairly insignificant factor.
As I said earlier, we Tradbowmen are not against compound bows as such and never have been. We have always been against their misuse where their obvious and undoubted mechanical advantage in being able to propel very heavy arrows with enormous momentum is deliberately given up for flat trajectory and speed using light arrows of low mass and momentum.
Many of the compounders use sights anyway. This negates the problems of high arc trajectories once the pins have been set up. Whatever the distance, you only have to put the pin on the spot and trajectory is automatically taken care of, so there really is no excuse for this usual kind of bow misuse in hunting.
If you are shooting barebow you should be getting well within your point-blank range and then halving it at least if you have any hunting skill.
As I have said elsewhere - hunting is not target practice on live animals.
We are there to humanely kill them, not to see if our equipment is working as well as we would like it to. You do that elsewhere and if you cannot, you use equipment and techniques which have been proven down the ages to work, which you should be doing anyway.
As Russ expressed it in perhaps the most succinct way I have read for quite a while -
"theres no excuse for going afield wondering if our equip is going to be ok. the game deserves better. we must KNOW what that arrow is going to do as it leaves our bow.....like taking shots at game at unrealistic ranges".
Russ' use of the word 'KNOW' is instructive.
The issue of straight arrow flight is a proper topic of concern as most of you have pointed out, but my post was a discussion of momentum vs kinetic energy and how it applies to arrow efficiency.
For the purposes of the discussion, perfect arrow flight was taken as a given. But, as some of you have correctly pointed out, the benefit of high momentum is severely reduced if the arrow is ocillating in flight (another way in which KE lost), fishtailing or porpoising, or performing other aerial acrobatics.
I hope I have not further confused anyone.
Dennis La Varenne
Dennis La Varénne
Have the courage to argue your beliefs with conviction, but the humility to accept that you may be wrong.
QVIS CVSTODIET IPSOS CVSTODES (Who polices the police?) - DECIMVS IVNIVS IVVENALIS (Juvenal) - Satire VI, lines 347–8
What is the difference between free enterprise capitalism and organised crime?
HOMO LVPVS HOMINIS - Man is his own predator.
Have the courage to argue your beliefs with conviction, but the humility to accept that you may be wrong.
QVIS CVSTODIET IPSOS CVSTODES (Who polices the police?) - DECIMVS IVNIVS IVVENALIS (Juvenal) - Satire VI, lines 347–8
What is the difference between free enterprise capitalism and organised crime?
HOMO LVPVS HOMINIS - Man is his own predator.
Post subject/ penetration
Dennis,
I cant see what someone jumping off a bridge has got to do with arrow penetration. In your example, a large fast moving body hits the water over a big area, WHACK, no surprises there. He floats down river. What if he was a champion olympic high diver, and cut the water like a knife, with scarcely a splash. I bet hed go deeper into the water if he jumped higher than lower. These sort of examples can get pretty silly.
What is required for good arrow perfomance on game is a well tuned bow, cut on contact razor sharp broadheads,heavy arrows (travelling fast, THE FASTER THE BETTER, ie, a bow as heavy as you can handle accurately. ) and accurate delivery to the right spot. It's really not that complicated, people.
I get annoyed with people saying a heavy slow arrow is better than a light fast arrow. Whats wrong with a heavy fast arrow?
I cant see what someone jumping off a bridge has got to do with arrow penetration. In your example, a large fast moving body hits the water over a big area, WHACK, no surprises there. He floats down river. What if he was a champion olympic high diver, and cut the water like a knife, with scarcely a splash. I bet hed go deeper into the water if he jumped higher than lower. These sort of examples can get pretty silly.
What is required for good arrow perfomance on game is a well tuned bow, cut on contact razor sharp broadheads,heavy arrows (travelling fast, THE FASTER THE BETTER, ie, a bow as heavy as you can handle accurately. ) and accurate delivery to the right spot. It's really not that complicated, people.
I get annoyed with people saying a heavy slow arrow is better than a light fast arrow. Whats wrong with a heavy fast arrow?
-
Dennis La Varenne
- Posts: 1776
- Joined: Sun Sep 07, 2003 10:56 pm
- Location: Tocumwal, NSW. Australia
Woody,
You are only partially correct. The analogy of the diver is still correct. The greatest limitation to penetration is impact velocity where all else is equal.
You are comparing two unlike objects, one with a broad frontal area and the other with a smaller frontal area.
If you increase the velocity of either, the depth of penetration in each case when compared to itself at increasing velocity at impact with the water, will decrease as impact velocity increases.
As your Olympic diver dives from greater heights and velocity at impact increases, penetration into the water will decrease. The same will happen with the belly flopper, but to a somewhat greater degree because of the broader frontal area, not because the principle is incorrect.
If you increase the mass of either and maintain velocity, penetration will improve a bit.
The only time this analogy ceases to apply is when gravitational terminal velocity is reached. Thereafter, no free-falling object can increase velocity.
Next, I did not say or infer that a heavy slow arrow is better. I did say that a slow heavy arrow can have the same momentum as a fast light arrow, and will maintain its level of momentum further downrange better than a fast light arrow.
You are correct, however. A fast heavy arrow is better than a slow heavy arrow where all else is equal.
By contrast, in firearms ballistics, where velocities are prodigious compared to arrows, it is now understood that with any given normal bullet type, penetration can be considerably improved by reducing velocity, NOT increasing it. This is counter intuitive but true.
It is specifically because of the principle of the V squared relationship between a moving projectile and the increasing resistance to penetration of the struck object as projecticle velocity increases. As velocity increases, the stuck object becomes increasingly tougher so that bullets begin to destruct ever increasingly. I am talking about animals here, not brick walls.
Arrows travel at far too slow a velocity to perhaps ever reach the stage where that kind of resistance becomes a serious problem. But it is there just the same, and it begins to show more readily when the arrow mass is lighter and impact velocities are higher.
Where you say -
"What is required for good arrow perfomance on game is a well tuned bow, cut on contact razor sharp broadheads,heavy arrows (travelling fast, THE FASTER THE BETTER, ie, a bow as heavy as you can handle accurately. ) and accurate delivery to the right spot. It's really not that complicated, people."
- is also correct, but in no way contradicts what I have written about the difference between the behaviours of kinetic energy and momentum and why one is a better predictor of the terminal ballistics of an arrow where all of those basic qualifications which you have referred to have been met.
It is also why I wrote that if it becomes necessary to reduce your bow weight a little, you should not reduce your arrow weight significantly if at all. The loss of velocity will only be fairly small and the momentum of the arrow will not reduce very much at all and be a more reliable performer than a significantly lighter arrow.'
For example Stickbowhunter and I have reduced our bow-weights from about the mid-60s to the mid-high 50s over recent years and have increased our arrow weights from the mid 500s to the mid-high 700s with as good or better penetration than ever and more pass throughs.
I was not making a recommendation about what is the best kind bowhunting equipment. I was talking about why any kind of equipment which produces a higher level of momentum is a better predictor of a desired outcome, and why momentum rather than kinetic energy is a better means of measuring that predictability.
The higher the momentum imparted to an arrow by any means, the greater the level of confidence we may have that it will do its job where all else is equal.
For you to then go on to say -
"I get annoyed with people saying a heavy slow arrow is better than a light fast arrow. Whats wrong with a heavy fast arrow?"
- is again comparing unlike equipment and is meaningless.
I did not say or imply that there was anything wrong with a fast heavy arrow at any stage. I did think that the discussion would have led anyone to the logical conclusion that such was the case. Hence my specific reference to the mechanical superiority of compounds which is not being used properly.
A fast heavy arrow is better than a slow heavy arrow and BOTH are better than a fast light arrow where it is desireable that humane lethal penetration of an animal is the intention, precisely because both earlier examples will almost certainly produce higher momentum than the latter.
Dennis La Varenne
You are only partially correct. The analogy of the diver is still correct. The greatest limitation to penetration is impact velocity where all else is equal.
You are comparing two unlike objects, one with a broad frontal area and the other with a smaller frontal area.
If you increase the velocity of either, the depth of penetration in each case when compared to itself at increasing velocity at impact with the water, will decrease as impact velocity increases.
As your Olympic diver dives from greater heights and velocity at impact increases, penetration into the water will decrease. The same will happen with the belly flopper, but to a somewhat greater degree because of the broader frontal area, not because the principle is incorrect.
If you increase the mass of either and maintain velocity, penetration will improve a bit.
The only time this analogy ceases to apply is when gravitational terminal velocity is reached. Thereafter, no free-falling object can increase velocity.
Next, I did not say or infer that a heavy slow arrow is better. I did say that a slow heavy arrow can have the same momentum as a fast light arrow, and will maintain its level of momentum further downrange better than a fast light arrow.
You are correct, however. A fast heavy arrow is better than a slow heavy arrow where all else is equal.
By contrast, in firearms ballistics, where velocities are prodigious compared to arrows, it is now understood that with any given normal bullet type, penetration can be considerably improved by reducing velocity, NOT increasing it. This is counter intuitive but true.
It is specifically because of the principle of the V squared relationship between a moving projectile and the increasing resistance to penetration of the struck object as projecticle velocity increases. As velocity increases, the stuck object becomes increasingly tougher so that bullets begin to destruct ever increasingly. I am talking about animals here, not brick walls.
Arrows travel at far too slow a velocity to perhaps ever reach the stage where that kind of resistance becomes a serious problem. But it is there just the same, and it begins to show more readily when the arrow mass is lighter and impact velocities are higher.
Where you say -
"What is required for good arrow perfomance on game is a well tuned bow, cut on contact razor sharp broadheads,heavy arrows (travelling fast, THE FASTER THE BETTER, ie, a bow as heavy as you can handle accurately. ) and accurate delivery to the right spot. It's really not that complicated, people."
- is also correct, but in no way contradicts what I have written about the difference between the behaviours of kinetic energy and momentum and why one is a better predictor of the terminal ballistics of an arrow where all of those basic qualifications which you have referred to have been met.
It is also why I wrote that if it becomes necessary to reduce your bow weight a little, you should not reduce your arrow weight significantly if at all. The loss of velocity will only be fairly small and the momentum of the arrow will not reduce very much at all and be a more reliable performer than a significantly lighter arrow.'
For example Stickbowhunter and I have reduced our bow-weights from about the mid-60s to the mid-high 50s over recent years and have increased our arrow weights from the mid 500s to the mid-high 700s with as good or better penetration than ever and more pass throughs.
I was not making a recommendation about what is the best kind bowhunting equipment. I was talking about why any kind of equipment which produces a higher level of momentum is a better predictor of a desired outcome, and why momentum rather than kinetic energy is a better means of measuring that predictability.
The higher the momentum imparted to an arrow by any means, the greater the level of confidence we may have that it will do its job where all else is equal.
For you to then go on to say -
"I get annoyed with people saying a heavy slow arrow is better than a light fast arrow. Whats wrong with a heavy fast arrow?"
- is again comparing unlike equipment and is meaningless.
I did not say or imply that there was anything wrong with a fast heavy arrow at any stage. I did think that the discussion would have led anyone to the logical conclusion that such was the case. Hence my specific reference to the mechanical superiority of compounds which is not being used properly.
A fast heavy arrow is better than a slow heavy arrow and BOTH are better than a fast light arrow where it is desireable that humane lethal penetration of an animal is the intention, precisely because both earlier examples will almost certainly produce higher momentum than the latter.
Dennis La Varenne
Dennis La Varénne
Have the courage to argue your beliefs with conviction, but the humility to accept that you may be wrong.
QVIS CVSTODIET IPSOS CVSTODES (Who polices the police?) - DECIMVS IVNIVS IVVENALIS (Juvenal) - Satire VI, lines 347–8
What is the difference between free enterprise capitalism and organised crime?
HOMO LVPVS HOMINIS - Man is his own predator.
Have the courage to argue your beliefs with conviction, but the humility to accept that you may be wrong.
QVIS CVSTODIET IPSOS CVSTODES (Who polices the police?) - DECIMVS IVNIVS IVVENALIS (Juvenal) - Satire VI, lines 347–8
What is the difference between free enterprise capitalism and organised crime?
HOMO LVPVS HOMINIS - Man is his own predator.
-
Stickbow Hunter
- Supporter
- Posts: 11637
- Joined: Sat Jul 26, 2003 8:33 pm
- Location: Maryborough Queensland
Woody said
A big percentage of bowhunters in the past and I believe at present, still place flat trajectory (arrow speed) as the number one priority. They can't stand the thought of shooting a heavier arrow that will be travelling a few feet per second slower and therefore won't have as flat a trajectory even though it will penetrate better. I believe this train of thought is a direct result of shooting long distances on the filed course where their aim is to have as flat a trajectory as possible.
On the field course they don't have to worry about how well their arrows penetrate foam targets but when hunting live animals they do - or at least they SHOULD!
This is why the saying "a heavy slow arrow is better than a light fast arrow" came about. It's a proven fact that from any given bow a heavy slow arrow will out penetrate a light fast one.
You also asked - Whats wrong with a heavy fast arrow? Abosolutely nothing! This is where the compound shooter has the advantage over the trad shooter in that his bow will always have higher stored energy and therefore will shoot any weight arrow faster than the trad bow would the same arrow (bow weights being equal of course). Sadly this extra energy is often wasted because the bowhunter is more interested in arrow speed rather than arrow penetration.
Here is an example of this using figures from the testing done for an article I wrote some years ago:
A 66lb longbow shooting 750 grain arrows had 44.14 ft/lbs of kinetic energy and .545 lbs/sec of momentum.
A 60 - 70lb modern compound shooting 500 grain arrows had 69.4 ft/lbs of kinetic energy and .550 lbs/sec of momentum.
As you can see the compound had over double the kinetic energy of the longbow yet they had approx the same amount of momentum (penetrating ability).
Now take the modern compound and shoot a heavy arrow of close to 700 grains and the kinetic energy was approx 88.4 ft/lbs and momentum was .745 lbs/sec. Very impressive!
If only we could get this message across to bowhunters both trad and modern. Why? Because penetration is very important to the bowhunter. More penetrating ability means there is more likelyhood of an exit wound which means a better blood trail and faster recovery. Also if for some reason a less than perfect hit happens extra penetration can mean the difference between recovering an animal or not.
Jeff
I also believe that you are right in saying this. However, where it becomes complicated is getting that message to bowhunters.What is required for good arrow perfomance on game is a well tuned bow, cut on contact razor sharp broadheads,heavy arrows (travelling fast, THE FASTER THE BETTER, ie, a bow as heavy as you can handle accurately. ) and accurate delivery to the right spot. It's really not that complicated, people.
A big percentage of bowhunters in the past and I believe at present, still place flat trajectory (arrow speed) as the number one priority. They can't stand the thought of shooting a heavier arrow that will be travelling a few feet per second slower and therefore won't have as flat a trajectory even though it will penetrate better. I believe this train of thought is a direct result of shooting long distances on the filed course where their aim is to have as flat a trajectory as possible.
On the field course they don't have to worry about how well their arrows penetrate foam targets but when hunting live animals they do - or at least they SHOULD!
This is why the saying "a heavy slow arrow is better than a light fast arrow" came about. It's a proven fact that from any given bow a heavy slow arrow will out penetrate a light fast one.
You also asked - Whats wrong with a heavy fast arrow? Abosolutely nothing! This is where the compound shooter has the advantage over the trad shooter in that his bow will always have higher stored energy and therefore will shoot any weight arrow faster than the trad bow would the same arrow (bow weights being equal of course). Sadly this extra energy is often wasted because the bowhunter is more interested in arrow speed rather than arrow penetration.
Here is an example of this using figures from the testing done for an article I wrote some years ago:
A 66lb longbow shooting 750 grain arrows had 44.14 ft/lbs of kinetic energy and .545 lbs/sec of momentum.
A 60 - 70lb modern compound shooting 500 grain arrows had 69.4 ft/lbs of kinetic energy and .550 lbs/sec of momentum.
As you can see the compound had over double the kinetic energy of the longbow yet they had approx the same amount of momentum (penetrating ability).
Now take the modern compound and shoot a heavy arrow of close to 700 grains and the kinetic energy was approx 88.4 ft/lbs and momentum was .745 lbs/sec. Very impressive!
If only we could get this message across to bowhunters both trad and modern. Why? Because penetration is very important to the bowhunter. More penetrating ability means there is more likelyhood of an exit wound which means a better blood trail and faster recovery. Also if for some reason a less than perfect hit happens extra penetration can mean the difference between recovering an animal or not.
Jeff
Arrow penetration
Denis,
You missed my main point entirely, but summed it up very concisely in your second paragraph in your reply to me.
I stand by my observation that these sorts of comparisons can get pretty silly. Chalk and cheese, there is no point in comparisons like this. A man jumping off a bridge, or an olympic high diver or a high velocity bullet are not hunting arrows. I'm quite sure that your science is spot on, that is not my contention.
How fast would a well tuned, cut on contact, razor sharp broadhead arrow have to be travelling, before they start bouncing off pigs and goats. Your logic may be perfect, but it is not relevant. Thats my main point.
My second point about fast heavy arrows is staight out of Hunting the Hard Way. Howard was no fool, the big draw weights he used was for flattening his trajectories and giving his arrows more grunt when they got there.I also quoted Howard when I said ( as heavy a bow as you can shoot accurately. ) I guess my second point is dont rely on just one aspect of efficiency but do everything you can to improve "grunt" at the business end of bowhunting. What annoys me when traditional hunters say slow and heavy is better, and high tech hunters say fast and light is better, they are both only half right. Fast and heavy is best.
Unless I have missunderstood, the gist of what you are saying is ( all scientiffic explanations aside ) is that if your arrows arent that fast it doesn't matter so much as long as their heavy enough for good momentum, which stikes me as being a bit one eyed. As you can see I have my own opinions and I think we'll have to agree to disagree on this subject.
You missed my main point entirely, but summed it up very concisely in your second paragraph in your reply to me.
I stand by my observation that these sorts of comparisons can get pretty silly. Chalk and cheese, there is no point in comparisons like this. A man jumping off a bridge, or an olympic high diver or a high velocity bullet are not hunting arrows. I'm quite sure that your science is spot on, that is not my contention.
How fast would a well tuned, cut on contact, razor sharp broadhead arrow have to be travelling, before they start bouncing off pigs and goats. Your logic may be perfect, but it is not relevant. Thats my main point.
My second point about fast heavy arrows is staight out of Hunting the Hard Way. Howard was no fool, the big draw weights he used was for flattening his trajectories and giving his arrows more grunt when they got there.I also quoted Howard when I said ( as heavy a bow as you can shoot accurately. ) I guess my second point is dont rely on just one aspect of efficiency but do everything you can to improve "grunt" at the business end of bowhunting. What annoys me when traditional hunters say slow and heavy is better, and high tech hunters say fast and light is better, they are both only half right. Fast and heavy is best.
Unless I have missunderstood, the gist of what you are saying is ( all scientiffic explanations aside ) is that if your arrows arent that fast it doesn't matter so much as long as their heavy enough for good momentum, which stikes me as being a bit one eyed. As you can see I have my own opinions and I think we'll have to agree to disagree on this subject.
-
Glenn Newell
Woody, I was at the World Masters Archery competition in 1994 and we were shooting a York round at stramit targets around 50mm to 75mm thick and in the centre there was a double layer of stramit. The thickness of the stramit is not important because the point is that there were all sorts of archery equipment being shot from light target bows and target arrows and heavy hunting longbows and recurves and heavy weight hunting arrows. We shot at distances from 20 to 60 metres and what stuck in my mind the most that at all of the distances when we retreived our arrows was that the heavy weight arrows would only penetrate the stramit the depth of the field point or a bit more where as the light weight target arrows and thin diameter arrows would be sticking out of the back of the target and at the longer distances the light target arrows were pentetrating the two thicknesses of stramit in the centre with ease where as the heavy hunting arrow setups and out of bows almost twice the poundage of the target bows couldn't even come close to that amount of penetration.
So you see Woody while the maths of energy and momentum are relevant it is not the whole story only part thereof, other factors such as arrow diameter and the balance point of the arrow will make a big differance to penetration on game. If you have a broadhead that has a diameter that is narrower than the shaft diameter you will loose penetration there as well.
A well tuned arrow matched perfectly to the bow and a sharp broadhead out of a light bow will out penetrate a much heavier weight bow and arrow combination not correctly setup anyday.
It's one of the great myths of bowhunting, shoot a heavy bow and heavy arrows to get good results on game and we wonder why so many longbow and recurve hunters have gone over to compounds, we only got what we deserved.
So you see Woody while the maths of energy and momentum are relevant it is not the whole story only part thereof, other factors such as arrow diameter and the balance point of the arrow will make a big differance to penetration on game. If you have a broadhead that has a diameter that is narrower than the shaft diameter you will loose penetration there as well.
A well tuned arrow matched perfectly to the bow and a sharp broadhead out of a light bow will out penetrate a much heavier weight bow and arrow combination not correctly setup anyday.
It's one of the great myths of bowhunting, shoot a heavy bow and heavy arrows to get good results on game and we wonder why so many longbow and recurve hunters have gone over to compounds, we only got what we deserved.
Arrow penetration
Glen,
Thank you for your post on this subject. If I've understood correctly the gist of what your saying is that factors such as shaft diameters and point designs, arrow velocitys and well tuned equipment are all factors in arrow penetration . This is true, and should be a consideration. As you know I have definite ideas on broadhead design.
One thing I will say, is that stramit is not feral pig and target points are not broadheads. When I hunt cardboard, if the arrow doesnt fall out I'm happy , however I understand what your saying. Remember I did say that shoot as heavy a bow as you can handle accurately, so I am not advocating people over bow them selves. I am presently hunting with a compound because I'm too busy these days to find the time to do the push up regime I was doing to keep strong enough to shoot my hunting recurve accurately. I am still using a heavy bow accurately. I still believe that with hunting bows, grunt is good.
Thank you for your post on this subject. If I've understood correctly the gist of what your saying is that factors such as shaft diameters and point designs, arrow velocitys and well tuned equipment are all factors in arrow penetration . This is true, and should be a consideration. As you know I have definite ideas on broadhead design.
One thing I will say, is that stramit is not feral pig and target points are not broadheads. When I hunt cardboard, if the arrow doesnt fall out I'm happy
, however I understand what your saying. Remember I did say that shoot as heavy a bow as you can handle accurately, so I am not advocating people over bow them selves. I am presently hunting with a compound because I'm too busy these days to find the time to do the push up regime I was doing to keep strong enough to shoot my hunting recurve accurately. I am still using a heavy bow accurately. I still believe that with hunting bows, grunt is good.-
Glenn Newell
Woddy I wasn't implying that you were, I shoot under 50# for my hunting bows but I do use heavy arrows but I have also built myself a bow that has the correct limb design to cast very heavy arrows for that bow, about 670 grains. I also barrel taper my shafts and they straighten up out of the bow quicker than a parallel shaft. The barrel taper also helps in penetration especially when you hit bone. In the States back in the late thirties or early fourties when archery seasons were first introduced accurate records were kept about the deer killed and the intresting point that came out of the whole study was that cleaner kills on deer were accomplished by the lighter weight bows.
I have been bowhunting since the early 70's and like a lot of people of that time I was brainwashed into thinking that I was under bowed for pigs because I was shooting a 55# bow, so I bought a 72# bow and shot 3/8 shafts and honestly my kills were no cleaner and the penetration was not any better, and infact I would say that I had more pass throughs with the lighter bow.
Heavy bows are fine but as said by Russ in the origional post you should only shoot as heavy a bow as you can comfortably handle. I have seen women shooting bows as light as 35# taking boars, you just have to hit them right.
All of those mathamitacial equations are fine in a perfect world. If you are shooting at game with a strong cross wind the effect of the wind on a large diameter shaft with high cut feathers will be greater than on a narrow diameter shaft with lower profile feathers, that will upset the equation considerably.
After shooting over 500 pigs with a bow over the years I do know the differance between stramit and a feral pig but I felt that that was a good example of of how the maths become less relevant in the real world when you take all factors into consideration...Glenn...
I have been bowhunting since the early 70's and like a lot of people of that time I was brainwashed into thinking that I was under bowed for pigs because I was shooting a 55# bow, so I bought a 72# bow and shot 3/8 shafts and honestly my kills were no cleaner and the penetration was not any better, and infact I would say that I had more pass throughs with the lighter bow.
Heavy bows are fine but as said by Russ in the origional post you should only shoot as heavy a bow as you can comfortably handle. I have seen women shooting bows as light as 35# taking boars, you just have to hit them right.
All of those mathamitacial equations are fine in a perfect world. If you are shooting at game with a strong cross wind the effect of the wind on a large diameter shaft with high cut feathers will be greater than on a narrow diameter shaft with lower profile feathers, that will upset the equation considerably.
After shooting over 500 pigs with a bow over the years I do know the differance between stramit and a feral pig but I felt that that was a good example of of how the maths become less relevant in the real world when you take all factors into consideration...Glenn...
-
Glenn Newell
I was lucky Russ, I saw the best of what bowhunting had to offer back in the early seventies, I lived and worked in the Queensland chanel country when pigs were in plauge proportions. A grazier once took me down to the lambing paddock to help him poision some sheep and in the morning there were around three hundred dead pigs in the paddock, I hunted a couple of kilometers away on the same property a few days later and the pigs were so thick it seemed as though the big kill in the other paddock didn't even make a dent in their numbers.
I also lived for several years in the central highlands west of Mackay and Rocky before a lot of that country was cleared and there were a lot of pigs there also. I doubt if I will ever live to see game in those numbers in those areas again...Glenn...
I also lived for several years in the central highlands west of Mackay and Rocky before a lot of that country was cleared and there were a lot of pigs there also. I doubt if I will ever live to see game in those numbers in those areas again...Glenn...
-
Stickbow Hunter
- Supporter
- Posts: 11637
- Joined: Sat Jul 26, 2003 8:33 pm
- Location: Maryborough Queensland
Glenn & Woody,
What you have said about proper arrow flight is very important and this was stated early on in the thread by Dennis:
I also think it is important for bowhunters to know the answer to this because as bowhunters we have an ethical obligation to to kill our game in a quick humane manner. For the bowhunter this means having his/her arrows penetrating the intended game the very best they can.
I firmly believe that momentum more acurately describes what happens when arrows strike living flesh than does kenetic energy.
The physics definition of momentum is the correct formula to measure the directional impulse of a body in motion. It is the force exerted over a period of time in one specific direction. Using an arrow as an example, it is the measure of the forward force exerted by the arrow over the time it is penetrating the target.
Penetration is best determined by understanding the relationship between momentum (inertia) and resistance (friction). The reason a heavier arrow will always penetrate a game animal better than a light arrow (shot from the same bow and tuned correctly) is that the heavy arrow's forward momentum is better able to overcome the friction caused by the animals body tissue.
Glenn you said:
I say this because I believe that we, as bowhunters, should all strive to shoot the bow of our choice with an arrow combination that will give us good momentum which assists with good arrow penetration on game. Of course the penetrating ability of an arrow does involve other factors, including some of the things you have mentioned, but these in no way lessen the relevance of momentum when discussing arrow penetration.
Jeff
What you have said about proper arrow flight is very important and this was stated early on in the thread by Dennis:
I thought the topic was about kinetic energy and momentum and which was the best indicator of an arrows ability to penetrate game and replied accordingly.The issue of straight arrow flight is a proper topic of concern as most of you have pointed out, but my post was a discussion of momentum vs kinetic energy and how it applies to arrow efficiency.
For the purposes of the discussion, perfect arrow flight was taken as a given.
I also think it is important for bowhunters to know the answer to this because as bowhunters we have an ethical obligation to to kill our game in a quick humane manner. For the bowhunter this means having his/her arrows penetrating the intended game the very best they can.
I firmly believe that momentum more acurately describes what happens when arrows strike living flesh than does kenetic energy.
The physics definition of momentum is the correct formula to measure the directional impulse of a body in motion. It is the force exerted over a period of time in one specific direction. Using an arrow as an example, it is the measure of the forward force exerted by the arrow over the time it is penetrating the target.
Penetration is best determined by understanding the relationship between momentum (inertia) and resistance (friction). The reason a heavier arrow will always penetrate a game animal better than a light arrow (shot from the same bow and tuned correctly) is that the heavy arrow's forward momentum is better able to overcome the friction caused by the animals body tissue.
Glenn you said:
I disagree with you as the maths is always relevant, especially in the real world!but I felt that that was a good example of of how the maths become less relevant in the real world when you take all factors into consideration...
I say this because I believe that we, as bowhunters, should all strive to shoot the bow of our choice with an arrow combination that will give us good momentum which assists with good arrow penetration on game. Of course the penetrating ability of an arrow does involve other factors, including some of the things you have mentioned, but these in no way lessen the relevance of momentum when discussing arrow penetration.
Jeff
-
Dennis La Varenne
- Posts: 1776
- Joined: Sun Sep 07, 2003 10:56 pm
- Location: Tocumwal, NSW. Australia
To all,
I offer the following responses to the comments made by both Woody and Glenn Newell.
Woody’s words - “I stand by my observation that these sorts of comparisons can get pretty silly. Chalk and cheese, there is no point in comparisons like this. A man jumping off a bridge, or an olympic high diver or a high velocity bullet are not hunting arrows.â€Â
My response: My use of the example of the high diver was to illustrate as simply as possible the principle of the V-squared relationship of velocity to the resistance to impact of the body being struck. It still is and was then relevant to that explanation. Any moving body which strikes another must overcome a certain level of resistance either to penetrate it or to move it as the result of that motion. That principle is very relevant to the issue of the efficiency of arrows.
The principle explains that as the velocity of an object of given mass increases, the resistance offered by a stationary body to the moving object increases in proportion to the square of the velocity of the moving object.
The analogy of the diver (belly flopper or Olympic diver) is appropriate in that it explains why the moving object suffers an increasing degree of damage as velocity increases. The better ballistic profile of the Olympic diver offers protection against that damage only for a very moderate increase in velocity. This occurs despite the density of water remaining constant. It doesn’t get harder if you feel it. It only gets harder the faster you hit it.
Push the flat of your hand into a bath and then slap it as hard as you can. This simple test can assist in demonstrating this principle. Next, lob a heavy object in to a pool and watch how it sinks. Next, hurl the object at full force into the pool and watch it slow down before it resumes sinking. It can be observed to slow down much more suddenly when thrown fast than if it is thrown into the water gently.
The further analogy using firearms bullets also explains that principle appropriately because it explains something that firearms people have known for years that if you continually drive a projectile faster and faster, the resistance offered by the object being struck becomes so high that the bullet fails and breaks up with ever decreasing penetration.
That principle still applies to arrows, albeit to a lesser degree because the velocity is lower on average, but it still affects arrow performance by the proportion of the increase in velocity.
Why I maintain that there a correlation between bullets, arrows and divers is precisely because all of them have the common property of being objects in motion which collide with a stationary object. They therefore behave according to the same well-established laws of physics that Isaac Newton worked out in the 1600s.
Woody’s words – “Your logic may be perfect, but it is not relevant.â€Â
My response: To entertain that there is no relevance is begging the question of your having recently discovered some vital principles of physics not know to science.
Woody’s words – “My second point about fast heavy arrows is staight out of Hunting the Hard Way. Howard was no fool, the big draw weights he used was for flattening his trajectories and giving his arrows more grunt when they got there.I also quoted Howard when I said ( as heavy a bow as you can shoot accurately. ) I guess my second point is dont rely on just one aspect of efficiency but do everything you can to improve "grunt" at the business end of bowhunting.â€Â
My response: Quoting Howard Hill does not establish any kind of fundamental principle regarding the properties of an arrow in flight. Just because you and I agree with his basic advice on choice of bowhunting equipment does nothing to explain why it works, and when it does not, why not.
Simply stating that such and such arrow achieves a recommended outcome does not prove the point because it offers no standard by which the predicted outcome can be tested by someone else such as the Government officials with whom I have had to deal and who are quite willing to take our bowhunting away unless we can prove that it is a humane method of hunting without their having to shoot animals which they will never do.
If we are called to account for our activity, we may be given 30 minutes or even an hour if we are lucky, and our proof will have to come from our mouths and what we can write.
The wise words of Howard Hill mean nothing to these people and represent no kind of justification on our behalf.
In our own defence, it is crucial that we need to be able to establish a means of being able to objectively verify our claims. That requirement should be one of our most important priorities.
I have been convinced over the years that the momentum theory of predicting arrow performance is the most single useful comprehensive explanatory tool we have. No-one has yet come up with one which better explains the terminal ballistics of arrow performance over a range of velocities than momentum.
Dr Ed Ashby, to whom I have earlier referred, has contributed the best explanation we have so far and to which I subscribe. He has also added an important explanation of why certain designs of arrow and broadhead influence terminal performance and which has not been refuted by any of the range of explanations I have investigated so far.
I agree with Glenn Newell’s proposition about the superior ballistic performance of barrelled arrows only were all of the other of Dr Ashby’s other conditions of arrow design have also been met. I am yet to be convinced that barrelling of itself promotes superior terminal performance through animal tissue. The principle of barrelling is well established in exterior ballistics theory. It is used all the time where long-range firearms shooting is concerned (especially where terminal velocity is reached before the bullet comes to rest) where so-called boat-tailed bullets are the choice.
Woody’s words: – “What annoys me when traditional hunters say slow and heavy is better, and high tech hunters say fast and light is better, they are both only half right. Fast and heavy is best.â€Â
My response: I wish I could find an instance where I or anyone else for that matter has either said that or even inferred that proposition.
No-one I have ever read or heard comment on the issue has said anything other than that velocity is not as important as mass when predicting the terminal performance of an arrow. No-one has ever said that it is unimportant or that slow and heavy was better.
I and others have always maintained that excellent terminal arrow performance can be achieved by increasing arrow mass even if it sacrifices some velocity.
We have always maintained that slow and heavy do not necessarily give anything away to high velocity and light mass. The momentum theory explains why some astonishing penetration can be had using trad equipment which depends more on arrow mass simply because it often cannot achieve the velocity obtainable by many compounds.
Woody’s words: – “Unless I have missunderstood, the gist of what you are saying is ( all scientiffic explanations aside ) is that if your arrows arent that fast it doesn't matter so much as long as their heavy enough for good momentum,â€Â
My response: You have certainly misunderstood the gist of what I have been trying to explain, and the scientific explanations are an integral part of it. High momentum is dependent upon velocity but not nearly as much as is Kinetic Energy.
As Stickbowhunter pointed out in his post (as has Ed Ashby in his articles) that a very fast lightweight arrow can achieve a very high KE figure compared with a tradbow. However a tradbow can achieve a comparable Momentum figure as the HV lightweight arrow with far lower velocity by simply using a higher mass arrow.
That helps explain why a slower tradbow can achieve as good a result on similar game animals at lower velocity by using heavy arrows as can a compound usually casting lighter arrows. We have not said or implied that fast is bad. We have always said that slower is not necessarily bad as some compounders try to have us believe.
Glenn’s words: - We shot at distances from 20 to 60 metres and what stuck in my mind the most that at all of the distances when we retreived our arrows was that the heavy weight arrows would only penetrate the stramit the depth of the field point or a bit more where as the light weight target arrows and thin diameter arrows would be sticking out of the back of the target and at the longer distances the light target arrows were pentetrating the two thicknesses of stramit in the centre with ease where as the heavy hunting arrow setups and out of bows almost twice the poundage of the target bows couldn't even come close to that amount of penetration.
So you see Woody while the maths of energy and momentum are relevant it is not the whole story only part thereof, other factors such as arrow diameter and the balance point of the arrow will make a big differance to penetration on game. If you have a broadhead that has a diameter that is narrower than the shaft diameter you will loose penetration there as well.
A well tuned arrow matched perfectly to the bow and a sharp broadhead out of a light bow will out penetrate a much heavier weight bow and arrow combination not correctly setup anyday.
My response: To a point I agree with most of what Glenn is saying with the following exception. I would be very hesitant to say categorically that light bows will out-penetrate heavier bows on the basis of an observation at the event mentioned.
The last paragraph is true enough so long as the words ‘correctly set-up’ are always a part of the equation. Awful arrow performance results from light draw weight bows which are not set up properly also and they have the added disadvantage of having less in reserve than the heavier bow.
However, if all else is equal including equipment set-up, then other factors than draw weight must be coming into consideration to explain the observed phenomena and which need investigation. However, I would not like to extrapolate arrow performance on stramit targets using target piles to predict arrow performance on animals using broadheads.
A very good explanation of why can be found in Dr Ashby’s discussion on the mechanics of broadhead design and the friction co-efficient of the arrow related to its diameter. From Glenn’s simple observation at this tournament that with increasing distance the thinner arrows out-penetrated the thicker arrows tends to bear out Dr Ashby’s thesis relating to arrow diameter and friction in terminal performance.
What would have assisted even more with an explanation of these phenomena observed by Glenn would have been a precise knowledge of the starting and terminal velocities of each of the bow types, relative to their draw weights.
The relative lack of penetration of the heavy large diameter arrows into the stramit butts could possibly have been the result of higher terminal velocity (the V-squared relationship) due to its higher draw weight coupled with the higher frictional co-efficient of the larger diameter arrow.
The narrower arrows from lighter bows could easily have been travelling a little slower, but their much lower frictional co-efficient was enough to allow the observed penetration (the v-squared principle and the frictional co-efficient principle working together).
That combination may also explain why lightweight gear with small diameter arrows can often equal the performance of heavier equipment on some animals.
But, as animals get larger and their bodies somewhat denser through heavier musculature and bone mass, I would be very guarded against recommending it as a general use tool except to very experienced bowhunters possessed of good marksmanship and hunting skills, purely on the basis of there being little or no reserve if all does not go well.
To paraphrase Dr Ashby, lightweight gear may not have enough reserve punch (momentum) to turn a hit into a kill on a larger animal.
Glenn’s words: - It's one of the great myths of bowhunting, shoot a heavy bow and heavy arrows to get good results on game and we wonder why so many longbow and recurve hunters have gone over to compounds, we only got what we deserved.
My response: I agree with this statement with the reservation that if one cannot control the bow, no amount of draw weight or arrow weight is worth a cracker. I understand that control of the bow is a given in this discussion.
With that proviso however, I must disagree with Glenn that heavier is worse. If you can control it, heavier is better because it has a better reserve of punch for the worst cases when things can go wrong and that extra punch can turn an otherwise poor hit into a humane kill.
Summation: The main point I am trying to convey is that we do not have any kind of consistent ballistics theory which explains cogently to those who will need to know in the future how and WHY our equipment works and to what degree can it be RELIED upon to kill animals humanely.
It seems to me from much of the forgoing argument against my posts that there has been a lot of in-house equipment self indulgence. If I have not been able to explain my position as well as I would have liked, no one else has been able to offer a better alternative that I can see.
I am more interested in helping to establish verifiable criteria by which we will be able to demonstrate quite decisively to Government officials that we can be relied upon to kill hunted animals humanely using equipment in the hands of an averagely skilled bowhunter under the worst-case scenario.
If it proves that lightweight gear shooting high velocity arrow can be relied upon to achieve the forgoing criteria, I am quite happy to go along with it. However, I am convinced that the equipment preference outlined by Woody is the superior but not for his reasons and the reasons are going to be the decider in any political debate on the matter.
When I and two other Australian Bowhunters’ Association delegates attended a meeting with the Pest Animal sub-committee of the Animal Welfare Advisory Committee of the Victorian Bureau of Animal Welfare, the main part of the discussion on why bowhunting should remain legal centred on the WHY and not the what of equipment, both in relation to the humanity of our pursuit and the efficacy of our equipment.
They did not really care what we used – only that we could demonstrate that it killed humanely.
Embarrassingly, because we could not advance a cogent theory of why our equipment worked, we were left with the pathetic response that we only believed that it was adequate and it was obvious that the two hunters in the room had completely divergent views on what was effective and humane.
How could we expect those people who have it within their powers to make an adverse recommendation to the Minister responsible for hunting in this State, to take us seriously? Some of them were either animal rights activists or RSPCA members or officers.
Dennis La Varenne
I offer the following responses to the comments made by both Woody and Glenn Newell.
Woody’s words - “I stand by my observation that these sorts of comparisons can get pretty silly. Chalk and cheese, there is no point in comparisons like this. A man jumping off a bridge, or an olympic high diver or a high velocity bullet are not hunting arrows.â€Â
My response: My use of the example of the high diver was to illustrate as simply as possible the principle of the V-squared relationship of velocity to the resistance to impact of the body being struck. It still is and was then relevant to that explanation. Any moving body which strikes another must overcome a certain level of resistance either to penetrate it or to move it as the result of that motion. That principle is very relevant to the issue of the efficiency of arrows.
The principle explains that as the velocity of an object of given mass increases, the resistance offered by a stationary body to the moving object increases in proportion to the square of the velocity of the moving object.
The analogy of the diver (belly flopper or Olympic diver) is appropriate in that it explains why the moving object suffers an increasing degree of damage as velocity increases. The better ballistic profile of the Olympic diver offers protection against that damage only for a very moderate increase in velocity. This occurs despite the density of water remaining constant. It doesn’t get harder if you feel it. It only gets harder the faster you hit it.
Push the flat of your hand into a bath and then slap it as hard as you can. This simple test can assist in demonstrating this principle. Next, lob a heavy object in to a pool and watch how it sinks. Next, hurl the object at full force into the pool and watch it slow down before it resumes sinking. It can be observed to slow down much more suddenly when thrown fast than if it is thrown into the water gently.
The further analogy using firearms bullets also explains that principle appropriately because it explains something that firearms people have known for years that if you continually drive a projectile faster and faster, the resistance offered by the object being struck becomes so high that the bullet fails and breaks up with ever decreasing penetration.
That principle still applies to arrows, albeit to a lesser degree because the velocity is lower on average, but it still affects arrow performance by the proportion of the increase in velocity.
Why I maintain that there a correlation between bullets, arrows and divers is precisely because all of them have the common property of being objects in motion which collide with a stationary object. They therefore behave according to the same well-established laws of physics that Isaac Newton worked out in the 1600s.
Woody’s words – “Your logic may be perfect, but it is not relevant.â€Â
My response: To entertain that there is no relevance is begging the question of your having recently discovered some vital principles of physics not know to science.
Woody’s words – “My second point about fast heavy arrows is staight out of Hunting the Hard Way. Howard was no fool, the big draw weights he used was for flattening his trajectories and giving his arrows more grunt when they got there.I also quoted Howard when I said ( as heavy a bow as you can shoot accurately. ) I guess my second point is dont rely on just one aspect of efficiency but do everything you can to improve "grunt" at the business end of bowhunting.â€Â
My response: Quoting Howard Hill does not establish any kind of fundamental principle regarding the properties of an arrow in flight. Just because you and I agree with his basic advice on choice of bowhunting equipment does nothing to explain why it works, and when it does not, why not.
Simply stating that such and such arrow achieves a recommended outcome does not prove the point because it offers no standard by which the predicted outcome can be tested by someone else such as the Government officials with whom I have had to deal and who are quite willing to take our bowhunting away unless we can prove that it is a humane method of hunting without their having to shoot animals which they will never do.
If we are called to account for our activity, we may be given 30 minutes or even an hour if we are lucky, and our proof will have to come from our mouths and what we can write.
The wise words of Howard Hill mean nothing to these people and represent no kind of justification on our behalf.
In our own defence, it is crucial that we need to be able to establish a means of being able to objectively verify our claims. That requirement should be one of our most important priorities.
I have been convinced over the years that the momentum theory of predicting arrow performance is the most single useful comprehensive explanatory tool we have. No-one has yet come up with one which better explains the terminal ballistics of arrow performance over a range of velocities than momentum.
Dr Ed Ashby, to whom I have earlier referred, has contributed the best explanation we have so far and to which I subscribe. He has also added an important explanation of why certain designs of arrow and broadhead influence terminal performance and which has not been refuted by any of the range of explanations I have investigated so far.
I agree with Glenn Newell’s proposition about the superior ballistic performance of barrelled arrows only were all of the other of Dr Ashby’s other conditions of arrow design have also been met. I am yet to be convinced that barrelling of itself promotes superior terminal performance through animal tissue. The principle of barrelling is well established in exterior ballistics theory. It is used all the time where long-range firearms shooting is concerned (especially where terminal velocity is reached before the bullet comes to rest) where so-called boat-tailed bullets are the choice.
Woody’s words: – “What annoys me when traditional hunters say slow and heavy is better, and high tech hunters say fast and light is better, they are both only half right. Fast and heavy is best.â€Â
My response: I wish I could find an instance where I or anyone else for that matter has either said that or even inferred that proposition.
No-one I have ever read or heard comment on the issue has said anything other than that velocity is not as important as mass when predicting the terminal performance of an arrow. No-one has ever said that it is unimportant or that slow and heavy was better.
I and others have always maintained that excellent terminal arrow performance can be achieved by increasing arrow mass even if it sacrifices some velocity.
We have always maintained that slow and heavy do not necessarily give anything away to high velocity and light mass. The momentum theory explains why some astonishing penetration can be had using trad equipment which depends more on arrow mass simply because it often cannot achieve the velocity obtainable by many compounds.
Woody’s words: – “Unless I have missunderstood, the gist of what you are saying is ( all scientiffic explanations aside ) is that if your arrows arent that fast it doesn't matter so much as long as their heavy enough for good momentum,â€Â
My response: You have certainly misunderstood the gist of what I have been trying to explain, and the scientific explanations are an integral part of it. High momentum is dependent upon velocity but not nearly as much as is Kinetic Energy.
As Stickbowhunter pointed out in his post (as has Ed Ashby in his articles) that a very fast lightweight arrow can achieve a very high KE figure compared with a tradbow. However a tradbow can achieve a comparable Momentum figure as the HV lightweight arrow with far lower velocity by simply using a higher mass arrow.
That helps explain why a slower tradbow can achieve as good a result on similar game animals at lower velocity by using heavy arrows as can a compound usually casting lighter arrows. We have not said or implied that fast is bad. We have always said that slower is not necessarily bad as some compounders try to have us believe.
Glenn’s words: - We shot at distances from 20 to 60 metres and what stuck in my mind the most that at all of the distances when we retreived our arrows was that the heavy weight arrows would only penetrate the stramit the depth of the field point or a bit more where as the light weight target arrows and thin diameter arrows would be sticking out of the back of the target and at the longer distances the light target arrows were pentetrating the two thicknesses of stramit in the centre with ease where as the heavy hunting arrow setups and out of bows almost twice the poundage of the target bows couldn't even come close to that amount of penetration.
So you see Woody while the maths of energy and momentum are relevant it is not the whole story only part thereof, other factors such as arrow diameter and the balance point of the arrow will make a big differance to penetration on game. If you have a broadhead that has a diameter that is narrower than the shaft diameter you will loose penetration there as well.
A well tuned arrow matched perfectly to the bow and a sharp broadhead out of a light bow will out penetrate a much heavier weight bow and arrow combination not correctly setup anyday.
My response: To a point I agree with most of what Glenn is saying with the following exception. I would be very hesitant to say categorically that light bows will out-penetrate heavier bows on the basis of an observation at the event mentioned.
The last paragraph is true enough so long as the words ‘correctly set-up’ are always a part of the equation. Awful arrow performance results from light draw weight bows which are not set up properly also and they have the added disadvantage of having less in reserve than the heavier bow.
However, if all else is equal including equipment set-up, then other factors than draw weight must be coming into consideration to explain the observed phenomena and which need investigation. However, I would not like to extrapolate arrow performance on stramit targets using target piles to predict arrow performance on animals using broadheads.
A very good explanation of why can be found in Dr Ashby’s discussion on the mechanics of broadhead design and the friction co-efficient of the arrow related to its diameter. From Glenn’s simple observation at this tournament that with increasing distance the thinner arrows out-penetrated the thicker arrows tends to bear out Dr Ashby’s thesis relating to arrow diameter and friction in terminal performance.
What would have assisted even more with an explanation of these phenomena observed by Glenn would have been a precise knowledge of the starting and terminal velocities of each of the bow types, relative to their draw weights.
The relative lack of penetration of the heavy large diameter arrows into the stramit butts could possibly have been the result of higher terminal velocity (the V-squared relationship) due to its higher draw weight coupled with the higher frictional co-efficient of the larger diameter arrow.
The narrower arrows from lighter bows could easily have been travelling a little slower, but their much lower frictional co-efficient was enough to allow the observed penetration (the v-squared principle and the frictional co-efficient principle working together).
That combination may also explain why lightweight gear with small diameter arrows can often equal the performance of heavier equipment on some animals.
But, as animals get larger and their bodies somewhat denser through heavier musculature and bone mass, I would be very guarded against recommending it as a general use tool except to very experienced bowhunters possessed of good marksmanship and hunting skills, purely on the basis of there being little or no reserve if all does not go well.
To paraphrase Dr Ashby, lightweight gear may not have enough reserve punch (momentum) to turn a hit into a kill on a larger animal.
Glenn’s words: - It's one of the great myths of bowhunting, shoot a heavy bow and heavy arrows to get good results on game and we wonder why so many longbow and recurve hunters have gone over to compounds, we only got what we deserved.
My response: I agree with this statement with the reservation that if one cannot control the bow, no amount of draw weight or arrow weight is worth a cracker. I understand that control of the bow is a given in this discussion.
With that proviso however, I must disagree with Glenn that heavier is worse. If you can control it, heavier is better because it has a better reserve of punch for the worst cases when things can go wrong and that extra punch can turn an otherwise poor hit into a humane kill.
Summation: The main point I am trying to convey is that we do not have any kind of consistent ballistics theory which explains cogently to those who will need to know in the future how and WHY our equipment works and to what degree can it be RELIED upon to kill animals humanely.
It seems to me from much of the forgoing argument against my posts that there has been a lot of in-house equipment self indulgence. If I have not been able to explain my position as well as I would have liked, no one else has been able to offer a better alternative that I can see.
I am more interested in helping to establish verifiable criteria by which we will be able to demonstrate quite decisively to Government officials that we can be relied upon to kill hunted animals humanely using equipment in the hands of an averagely skilled bowhunter under the worst-case scenario.
If it proves that lightweight gear shooting high velocity arrow can be relied upon to achieve the forgoing criteria, I am quite happy to go along with it. However, I am convinced that the equipment preference outlined by Woody is the superior but not for his reasons and the reasons are going to be the decider in any political debate on the matter.
When I and two other Australian Bowhunters’ Association delegates attended a meeting with the Pest Animal sub-committee of the Animal Welfare Advisory Committee of the Victorian Bureau of Animal Welfare, the main part of the discussion on why bowhunting should remain legal centred on the WHY and not the what of equipment, both in relation to the humanity of our pursuit and the efficacy of our equipment.
They did not really care what we used – only that we could demonstrate that it killed humanely.
Embarrassingly, because we could not advance a cogent theory of why our equipment worked, we were left with the pathetic response that we only believed that it was adequate and it was obvious that the two hunters in the room had completely divergent views on what was effective and humane.
How could we expect those people who have it within their powers to make an adverse recommendation to the Minister responsible for hunting in this State, to take us seriously? Some of them were either animal rights activists or RSPCA members or officers.
Dennis La Varenne
Dennis La Varénne
Have the courage to argue your beliefs with conviction, but the humility to accept that you may be wrong.
QVIS CVSTODIET IPSOS CVSTODES (Who polices the police?) - DECIMVS IVNIVS IVVENALIS (Juvenal) - Satire VI, lines 347–8
What is the difference between free enterprise capitalism and organised crime?
HOMO LVPVS HOMINIS - Man is his own predator.
Have the courage to argue your beliefs with conviction, but the humility to accept that you may be wrong.
QVIS CVSTODIET IPSOS CVSTODES (Who polices the police?) - DECIMVS IVNIVS IVVENALIS (Juvenal) - Satire VI, lines 347–8
What is the difference between free enterprise capitalism and organised crime?
HOMO LVPVS HOMINIS - Man is his own predator.
Arrow momentum
Denis,
You are still not understanding what I'm trying to say about drawing comparisons. I'm not arguing your ballistic physics, and to explain why I think comparisons of this type are silly I will give you one.
If you shoot a bullet from a rifle into a sand bag it will pull up quickly, for the very reasons your saying about high velocity impacts increasing penetration resistance. you are right.
Now shoot a broadhead arrow into it. It will go straight through. My point is that even though the physics principles are exactly the same, in this case the arrow achieves a far better performance. I'm far more interested in why the arrow works than why the bullet doesn't. I think you are looking at the question from the wrong perspective. I'm sure you know all this, I just think your focus is in the wrong place. Anyway, I think I've bent your ear enough on this subject and I'm probably getting tiresome. These discussions go much better with a campfire and a bottle of good port anyway.Best regards, Woody.
You are still not understanding what I'm trying to say about drawing comparisons. I'm not arguing your ballistic physics, and to explain why I think comparisons of this type are silly I will give you one.
If you shoot a bullet from a rifle into a sand bag it will pull up quickly, for the very reasons your saying about high velocity impacts increasing penetration resistance. you are right.
Now shoot a broadhead arrow into it. It will go straight through. My point is that even though the physics principles are exactly the same, in this case the arrow achieves a far better performance. I'm far more interested in why the arrow works than why the bullet doesn't. I think you are looking at the question from the wrong perspective. I'm sure you know all this, I just think your focus is in the wrong place. Anyway, I think I've bent your ear enough on this subject and I'm probably getting tiresome. These discussions go much better with a campfire and a bottle of good port anyway.Best regards, Woody.
Woody, with respect mate, I think it may be you missing the point. Your cited example of the sand bag, if I'm not mistaken? actually proves Dennis's theory of high velocity not necessarily resulting in better penetration.
Dennis's posts take me forever to read and digest, but I think this was the gist of his quote on the diver into water thingy.
Erron
Dennis's posts take me forever to read and digest, but I think this was the gist of his quote on the diver into water thingy.
Erron
arrow momentum
Erron,
If you read my last post, I say that Denis is
right . What he is saying is correct. My contention is that if comparisons are made they should of apples to apples and not apples to oranges. Damm, you've made me give another comparison.
The only truly interesting article I've read on comparisons is Ed Ashby's natal study where Broadhead arrow is compared to Broadhead arrow, what works and what doesn't. Best regards,
Woody.
If you read my last post, I say that Denis is
right . What he is saying is correct. My contention is that if comparisons are made they should of apples to apples and not apples to oranges. Damm, you've made me give another comparison.
The only truly interesting article I've read on comparisons is Ed Ashby's natal study where Broadhead arrow is compared to Broadhead arrow, what works and what doesn't. Best regards,
Woody.
A very interesting thread and certainly thought provoking. I never really understood physics or ever will so formulas mean little to me. If you really know your maths you can prove or disprove just about anything.
The discussion reminded me of an article I read several years ago I found it last night. Pat Lefemine ( of the bowsite) was hunting Moose in Alaska using a 68 pound long bow and 26 inch raminwood shaft which weighed 800 grains when madeup. This arrow had a measured speed of 115 feet per second, but it passed clean through a big moose of around the 60 inch catagory.
While people might find excuses why the set up should not have worked, I think it shows the momentum contained in the shaft was sufficient to do the job.
Fast/slow, light/heavy as long as the arrow has sufficient energy to do its job efficiently does it really matter? Getting the arrow to the target spot on is the responsiblity of the shooter. If they can not accurately shoot the arrow then they should not be out in the field. This applys to slower gear as well as the bullet bows.
The discussion reminded me of an article I read several years ago I found it last night. Pat Lefemine ( of the bowsite) was hunting Moose in Alaska using a 68 pound long bow and 26 inch raminwood shaft which weighed 800 grains when madeup. This arrow had a measured speed of 115 feet per second, but it passed clean through a big moose of around the 60 inch catagory.
While people might find excuses why the set up should not have worked, I think it shows the momentum contained in the shaft was sufficient to do the job.
Fast/slow, light/heavy as long as the arrow has sufficient energy to do its job efficiently does it really matter? Getting the arrow to the target spot on is the responsiblity of the shooter. If they can not accurately shoot the arrow then they should not be out in the field. This applys to slower gear as well as the bullet bows.
-
doninkaliphornistan
- Posts: 46
- Joined: Wed Jan 07, 2004 12:47 pm
- Location: high in the desert of southern kaliphornistan
momentum vs KE ?
i'll go along with what vegie said, but i'd have to say: "which has more at the SAME speed? say 180fps (a reasonable trad bow "speed"), a ping pong ball or a golf ball? (or more appropiately, light aero or heavy aero?)
there are many that do not accept, perhaps they don't understand, that notion.
just for grins , a friend and i once dropped a ping pong ball and a golf ball from a measured heigth onto a pane of glass. guess which broke the pane?
i'm amazed at how many do not understand the weight issue in discussing speed vs penetration vs weight vs sharpness of broadhead vs arrow placement so it goes ...
...
pure and simple, with all factors being equal EXCEPT WEIGHT, for what ever the reasons dictated by laws of physics, the heavier of 2 projectiles traveling at the same speed will "penetrate" deeper/most ...
one of those "laws" that many archers ignore, or are not aware of, in their ongoing quest for more "speed" is: ""to DOUBLE the speed, is to QUADRUPLE the energy."
i doubt many of us can double the speed of ANY bow we have.
it is indeed, an ongoing "discussion" that i believe has no end ...
as for me, i will continue to shoot the heaviest shaft i can.
there are many that do not accept, perhaps they don't understand, that notion.
just for grins
, a friend and i once dropped a ping pong ball and a golf ball from a measured heigth onto a pane of glass. guess which broke the pane?i'm amazed at how many do not understand the weight issue in discussing speed vs penetration vs weight vs sharpness of broadhead vs arrow placement so it goes ...
... pure and simple, with all factors being equal EXCEPT WEIGHT, for what ever the reasons dictated by laws of physics, the heavier of 2 projectiles traveling at the same speed will "penetrate" deeper/most ...
one of those "laws" that many archers ignore, or are not aware of, in their ongoing quest for more "speed" is: ""to DOUBLE the speed, is to QUADRUPLE the energy."
i doubt many of us can double the speed of ANY bow we have.
it is indeed, an ongoing "discussion" that i believe has no end ...
as for me, i will continue to shoot the heaviest shaft i can.
when in doubt, run in circles and scream and shout ...
-
Glenn Newell
I understand the momentum theory no worries, thats why I shoot 675 grain arrows out of my 47# hunting bow to get maxium penetration as have I said in a previous post. But to tell somebody that weight plus speed to get maxium penetration with your bowhunting setup is a myth because arrows flex all the way to the target reguardless of what you have been told they do not fly straight especially at hunting ranges. When you have things like archers paradox working against you especially at close range no amount of extra poundage or arrow weight is going to help you with penetration. Your arrow setup must be perfectly matched to your bow so it will recover out of your bow as quickly as possible, if the arrow has still not recovered by the time it hits your target it will lose a lot of penetration. Even a very heavy arrow that has not recovered properly properly will not penetrate as far as a lighter arrow that has.
You see it all of the time, some poor bugger has bought a hunting bow and I am talking about recurves and longbows which he can't draw properly because he is over bowed or he has bought arrows that are over spined to buggery and wonders why he has got such poor penetration in the field on game even though he learnt to shoot his well enough to pass some silly bowhunter proficency course. The knowledge of tuning your arrow to your bow is one of the most misunderstood principles with traditionalist whereas with the hightec gear you can tune the bow to your arrows.
You don't need a heavy bow to shoot game, even the largest deer in Australia can be killed with a 40# bow as long as the correct arrow setup is being shot. Howard Hill once wrote that the largest bull moose can be killed with a 40# bow and a heavy arrow, but Howard understood arrow deflection better than anybody.
I feel sorry of a bowhunter when I hear them say that they can't shoot a heavy enough bow to shoot game like pigs, because some wanker has told them they need to shoot 60# for pigs, people who say things like this just don't know what they are talking about, ignorance and misunderstanding has been working against the traditional side of bowhunting for many years...Glenn...
You see it all of the time, some poor bugger has bought a hunting bow and I am talking about recurves and longbows which he can't draw properly because he is over bowed or he has bought arrows that are over spined to buggery and wonders why he has got such poor penetration in the field on game even though he learnt to shoot his well enough to pass some silly bowhunter proficency course. The knowledge of tuning your arrow to your bow is one of the most misunderstood principles with traditionalist whereas with the hightec gear you can tune the bow to your arrows.
You don't need a heavy bow to shoot game, even the largest deer in Australia can be killed with a 40# bow as long as the correct arrow setup is being shot. Howard Hill once wrote that the largest bull moose can be killed with a 40# bow and a heavy arrow, but Howard understood arrow deflection better than anybody.
I feel sorry of a bowhunter when I hear them say that they can't shoot a heavy enough bow to shoot game like pigs, because some wanker has told them they need to shoot 60# for pigs, people who say things like this just don't know what they are talking about, ignorance and misunderstanding has been working against the traditional side of bowhunting for many years...Glenn...
Last edited by Glenn Newell on Sat Jan 24, 2004 3:49 pm, edited 1 time in total.