# arrow energy



## berettaboys (Sep 21, 2007)

a buddy of mine has just got a new bow set up and the arrows are very short, i believe 25 inches. i have compared them to mine and a few of my friends arrows, and have been wondering how much energy they will loose when hitting a target. :?: 
although he is picking up greater speed and less drop with the arrows hes using, he is concerned that the new arrows might not penetrate like his older 29-31 inch aluminum arrows would on animals.
what are your guys's thoughts on this theory? it kind of makes sens, just like a 180gr. bullet will hit an animal with more energy then a 150 gr. bullet.
any help or thoughts on this matter would be greatly appreciated. 8)


----------



## HNT2LV (Sep 19, 2008)

My first thought is how did he go from 29-31 to 25 inch Arrows. Overdraw, but that seems like a huge overdraw 6".


----------



## berettaboys (Sep 21, 2007)

just the difference in bows from 20 years ago, also met with a different set up. he had a 27 1/2 in. draw with a 31 in arrow. now that they just set him up its even shorter now with the whiskerbisket rest and going to a trigger so his new arrows a 25 inch long.


----------



## MEEN (Jan 27, 2009)

It is going to depend on several things. Are his arrows still aluminum? Are they the same diameter?

Assuming his new arrows are aluminum, same diameter, and five inches shorter he lost 1.3 ft-lbs.

If they are carbon he lost a little more.


----------



## TEX-O-BOB (Sep 12, 2007)

> what are your guy's thoughts on this theory?


No theory here at all. It's a fact, a heavier arrow will always out penetrate a light one. Period.

I know all you speed freaks are crapin yer pants right now thinking your 300 grain arrow going 335 fps is going to out penetrate a 600 grain arrow going 190 fps. IT WONT! Because of a little physics factor called momentum. You see, Kinetic energy means nothing if you don't have the weight behind it to create momentum. Momentum, or "slugs" of energy is what carries the arrow THROUGH the target and out the other side. The kind of energy that can only be stored in something heavy. Kinetic energy on the other hand is a TRANSFER of energy from one thing (175grain boat tail going 2900 fps) to another (deer). That's how bullets kill things, with shock, a transfer of energy. The hemorrhaging you get from a bullet wound is just icing on the cake.

I'm going to prove my point next week when I kill an elk with a 40 pound self-bow and a 780 grain ash arrow. I'll post pics. 8)

Shoot a heavy arrow, get good penetration. Always.


----------



## Bowdacious (Sep 16, 2007)

TEX-O-BOB said:


> > what are your guy's thoughts on this theory?
> 
> 
> No theory here at all. It's a fact, a heavier arrow will always out penetrate a light one. Period.
> ...


Very good explination Tex. 
A lot of people are so obssesed with the SPEED when in actuality it isn't speed that kills, it is kinetic energy. Different bows will actually shoot the same arrow diferently and therefore the kinetic energy is also very different. Matthews Monster boasts that it is the fastest bow out there.....which is great but compare the kinetic energy and you will find that the Monster leaves a lot to be desired. IT IS ALL ABOUT KINETIC ENERGY AND SHOT PLACEMENT.


----------



## lehi (Sep 13, 2007)

Cool post Tex. Did you happen to get my last PM i sent ya?


----------



## swbuckmaster (Sep 14, 2007)

The monster has enough KE to push an arrow length wise through a deer. :shock: 

It has enough KE to use a larger broad head for those not so great shots.  

Any time you can take the same arrow weight and push it 50 fps faster you will get more KE. :mrgreen: 

It has enough Ke to make me wish I had some money to purchase one. -#&#*!- 

It will also do it quieter than my current bow! -)O(-


----------



## TEX-O-BOB (Sep 12, 2007)

Quiet? Compared to what? :lol:


----------



## TEX-O-BOB (Sep 12, 2007)

lehi said:


> Cool post Tex. Did you happen to get my last PM i sent ya?


Ya, I got it.


----------



## MEEN (Jan 27, 2009)

TEX-O-BOB said:


> No theory here at all. It's a fact, a heavier arrow will always out penetrate a light one. Period.


Sorry Tex but I gotta call you on it. A heavier arrow will not always out penetrate a light one. It depends on how much energy is imparted upon the target. i.e. a big fat arrow will create more friction (loss of energy) than a light skinny one resulting in LESS penetration.



> I know all you speed freaks are crapin yer pants right now thinking your 300 grain arrow going 335 fps is going to out penetrate a 600 grain arrow going 190 fps. IT WONT! Because of a little physics factor called momentum. You see, Kinetic energy means nothing if you don't have the weight behind it to create momentum. Momentum, or "slugs" of energy is what carries the arrow THROUGH the target and out the other side. The kind of energy that can only be stored in something heavy. Kinetic energy on the other hand is a TRANSFER of energy from one thing (175grain boat tail going 2900 fps) to another (deer). That's how bullets kill things, with shock, a transfer of energy. The hemorrhaging you get from a bullet wound is just icing on the cake.


Gotta call you on it again. Momentum is mass * velocity. SO in momentum mass has just as much as an effect as velocity. KE is .5*mass*velocity^2 The integral of momentum IS kinetic energy so it's kind of vague to analyze the comparison. I wont get into what implications that has but it's like comparing velocity and acceleration. They are dependant upon each other. So it's absolutely wrong to say that Momentum is better.

Basically I would look at what is important, and that is the amount of energy transferred from the arrow in flight to your target. Energy and Momentum are CONSERVED.

Now I think this is what you were trying to get at Tex. Just because something has a large amount of momentum doesn't mean your target will feel all or even 10% of that momentum (unless the arrow doesn't pass through). I could go into some long spill about arrows passing through or not and yadda yadda yadda. It's boring. A larger arrow is able to transfer more of its energy into its target (however this results in less penetration). A smaller arrow will need more ft-lbs of energy in order to transfer the same amount of energy as a large arrow.



> I'm going to prove my point next week when I kill an elk with a 40 pound self-bow and a 780 grain ash arrow. I'll post pics. 8)
> 
> Shoot a heavy arrow, get good penetration. Always.


Shoot a heavy arrow, (at the same velocity as a smaller arrow) and impart more momentum but get less penetration.


----------



## jahan (Sep 7, 2007)

MEEN said:


> TEX-O-BOB said:
> 
> 
> > No theory here at all. It's a fact, a heavier arrow will always out penetrate a light one. Period.
> ...


Shoot a heavy arrow, (at the same velocity as a smaller arrow) and impart more momentum but get less penetration.[/quote:3iknhviq]

You have to be a Mechanical Engineer, you made my head hurt I haven't used that crap since college, hahaha. Integrals, derivatives, partial differential equations. _/O -O,- :lol:


----------



## swbuckmaster (Sep 14, 2007)

TEX-O-BOB said:


> Quiet? Compared to what? :lol:


My LX 
I shot the monster with around a 700 grain arrow and it still pushed it around 250 fps. I didn't feel the shot and it was so quiet i didn't even hear it. It also pushed that arrow almost all the way through one of UAC target blocks :shock:


----------



## CP1 (Oct 1, 2007)

I am going to go out on a limb here and give the thought that KE & momentum have very little to do with kills in the archery world. If so then why is only 40 foot lb required? 
In my opinion it has a lot more to do with shot placement and the ability of your broad head to cut properly, then how fast you are shooting or the weight of your arrow. 

Tex kills with his stick under 20 yards all day long because he can make the shot, SWBUCK kills all day long at much further distances because he is a dang good shot with his given equipment. If your set up is tuned properly and you have practised your guts out- you will be a death machine regardless of your speed or arrow weight.


----------



## berettaboys (Sep 21, 2007)

thanks for all your guyses help on this. he is going to try different arrows. he is not happy with the penetration he is getting with his new short carbon arrows. 8)


----------



## TEX-O-BOB (Sep 12, 2007)

> Sorry Tex but I gotta call you on it. A heavier arrow will not always out penetrate a light one. It depends on how much energy is imparted upon the target. i.e. a big fat arrow will create more friction (loss of energy) than a light skinny one resulting in LESS penetration.


On a block target yes. But were not talking about killing foam animals were talking about the real ones. Once an arrow makes the initial wound the rest of it fallows trough with very little drag. Plus add the fact that blood is very slippery and you get even lees drag. The diameter of the arrow matters very little in regard to ANIMAL penetration once a wound channel has been created by a broadhead.



> Basically I would look at what is important, and that is the amount of energy transferred from the arrow in flight to your target. Energy and Momentum are CONSERVED.


And again I say the TRANSFER of energy is NOT how an arrow kills an animal. That is how BULLETS kill animals. The energy stored in the bullet is TRANSFERED to the deer causing shock and trauma. Arrows should essentially pass through the animal with as little energy loss or TRANSFER of energy as possible. The type of head you shoot, what the arrow runs into while making it's way through the animal, and the total weight of the arrow are the only factors that determine how far it will or will not penetrate. You can post up all the fancy pants math you want, It doesn't change a thing. Math is finite, killing critters has many variables and the bottom line is a heavy arrow will be more stable in flight, stabilize a broadhead better, deflect less off of obstructions, and kill with more efficiency than a light one. That's not math or science, that's common sense! Even a dummy like me can figure that out.



> Shoot a heavy arrow, (at the same velocity as a smaller arrow) and impart more momentum but get less penetration.


You're on dope. Well, may be not if the heavy arrow is 3 inches in diameter.


----------



## wyoming2utah (Sep 12, 2007)

A couple of essays that discuss this topic:
http://www.alaskabowhunting.com/PR/Unde ... ration.pdf

http://bowsite.com/bowsite/features/pra ... /index.cfm

http://tradgang.com/ashby/Momentum%20Ki ... ration.htm

What did I learn? That nobody agrees...


----------



## MEEN (Jan 27, 2009)

TEX-O-BOB said:


> On a block target yes. But were not talking about killing foam animals were talking about the real ones. Once an arrow makes the initial wound the rest of it fallows trough with very little drag. Plus add the fact that blood is very slippery and you get even lees drag. The diameter of the arrow matters very little in regard to ANIMAL penetration once a wound channel has been created by a broadhead.


Very true because the coefficient of friction becomes so small that the size of the arrow has little influence. Therefore we can agree that a large or small arrow will have nearly the same penetration. Let's just say it's close enough to kiss.



> And again I say the TRANSFER of energy is NOT how an arrow kills an animal. That is how BULLETS kill animals. The energy stored in the bullet is TRANSFERED to the deer causing shock and trauma. Arrows should essentially pass through the animal with as little energy loss or TRANSFER of energy as possible.


I completely agree. I was in a hurry this morning copied and pasted from a prior post that was dealing with bullets.



> The type of head you shoot, what the arrow runs into while making it's way through the animal, and the total weight of the arrow are the only factors that determine how far it will or will not penetrate. You can post up all the fancy pants math you want, It doesn't change a thing. Math is finite, killing critters has many variables and the bottom line is a heavy arrow will be more stable in flight, stabilize a broadhead better, deflect less off of obstructions, and kill with more efficiency than a light one. That's not math or science, that's common sense! Even a dummy like me can figure that out.


To quantify this it should be the head you shoot, what the arrow runs into, and the KE (not mass). I just showed that mass is just as important as velocity. A mass with no velocity is static therefore velocity has to have some significance for penetration.



> Shoot a heavy arrow, (at the same velocity as a smaller arrow) and impart more momentum but get less penetration.





> You're on dope. Well, may be not if the heavy arrow is 3 inches in diameter.


I meant KE instead of velocity. Your right a heavier arrow with the same velocity as a smaller arrow will have more KE thus resulting in better penetration. It should say shoot a heavy arrow, (at the same KE or momentum as a smaller arrow)

Tex generates his KE from mass and those of us with training wheels generate our KE with speed. The size of the arrow has little effect on penetration. Just shoot the deer in the vitals.


----------



## swbuckmaster (Sep 14, 2007)

the thing I have learned is when you are a short midget like myself and my 25" arrows will still go all the way through a deer and stick in the dirt at the distances I shoot. However my buddies arrow is longer weighs more and hits harder. He has more KE created out of his bow because he has a 3" longer draw.

But he cant sneak as good as a midget so it all evens out.  

midgets rule! *OOO*


----------



## jahan (Sep 7, 2007)

swbuckmaster said:


> the thing I have learned is when you are a short midget like myself and my 25" arrows will still go all the way through a deer and stick in the dirt at the distances I shoot. However my buddies arrow is longer weighs more and hits harder. He has more KE created out of his bow because he has a 3" longer draw.
> 
> But he cant sneak as good as a midget so it all evens out.
> 
> *midgets rule!* *OOO*


Midgets unite, F'n A dude. :mrgreen: :lol:


----------



## CP1 (Oct 1, 2007)

Does SWBUCKMASTER stand for Short- & Whooly- & master of killing bucks?


----------



## proutdoors (Sep 24, 2007)

CP1 said:


> Does SWBUCKMASTER stand for Short- & Whooly- & master of killing bucks?


 -_O-


----------



## MEEN (Jan 27, 2009)

wyoming2utah said:


> A couple of essays that discuss this topic:
> http://www.alaskabowhunting.com/PR/Unde ... ration.pdf
> 
> http://bowsite.com/bowsite/features/pra ... /index.cfm
> ...


Very interesting articles thatnks for posting them. The first one is crap. He contradicts himself. The second one is okay. The third one is the best although it is full of equations and it even put me to sleep. The author uses the justification that an arrow traveling faster generates more friction (not sure I agree 100%) but I can buy that. Force of friction = coefficient of friction X normal force. So I think what the author is saying is that an arrow traveling faster doesnt allow the wound channel to clear soon enough so more of a normal force is present. Seems possible.

The author is saying that for two arrows with the *same *momentum (Assuming Tex's big heavy tree branch and my light carbon arrow have the same momentum for example), Tex's tree limb will penetrate farther because my momentum was generated from speed at the cost of increased friction whereas Tex's momentum was generated from mass. I can buy that but I bet the difference is finite.


----------



## MEEN (Jan 27, 2009)

jahan said:


> You have to be a Mechanical Engineer, you made my head hurt I haven't used that crap since college, hahaha. Integrals, derivatives, partial differential equations. _/O -O,- :lol:


I still have night sweats thinking about PDE's. Those were the worst.


----------



## TEX-O-BOB (Sep 12, 2007)

> Tex generates his KE from mass and those of us with training wheels generate our KE with speed. The size of the arrow has little effect on penetration. Just shoot the deer in the vitals.


Say hallelujah!!! We finally agree on something! 

I knew you'd see it my way... :mrgreen:


----------



## bow_dude (Aug 20, 2009)

I typed this once and for some reason it didn't post, so I'll try it again.

Get your self an archery program such as T.A.P. where your can use different arrow configurations and see what the calculations are as you go from heavy to light arrows and see the arrow speed change and the K.E. values change. You will be shocked at what you find out. I did and the K.E. values hardly changed. I ran an arrow weighing 356 grains, 386 grains, and 420. I think I even ran a heavier arrow. Regardless, the program will calculate K.E. out to 200 yards, I ran it out to 70. All dropped off as the yardage increased, but the difference between the 356 grain arrow traveling at 331 fps and the 420 grain arrow traveling at 305 fps was about 5 less in K.E. value at 70 yards. Yes, the heavier arrow had more K.E. , but the difference was almost nothing (2 or 3). The lighter arrow dropped off faster, but when you hit 35 to 40 yards, all the figures stabilized and the drop off was about the same rate from light to heavy arrow for the remainder of the 70 yards. Quite a shock for sure. What was really interesting was feathers caused a real drop off almost immediatlely. The difference between vanes and feathers was surprising. We hear about how a heavy arrow out penetrates, but here is a program that takes the "wives tales" conjecture out of it and shows the calculations. What made the difference was not the arrow weight, but the bows efficiency. My Elite GT 500 is different than my Mathews LD. The GT 500 has an efficiency rating of 80 %. You can bet that a stick bow shooting a heavy arrow is no where near 80 %. All the arrows at 70 yards were above 60 lbs of K.E. (or what ever it is measured in) I was lookking for an arrow combination to use on my loper hunt. I ended up using the 386 weight arrow because I was shooting a 100 grain tip and so my foc was heavier which I figured would help me in the windy conditions you run into when in the desert. Speed and K.E. became a moot point when shooting past 40 yards. 

I ran into a weapons engineer at SL Archery several years ago. He designed weapons for the military. He was very enlighting on several subjects. He told me that years ago, bullet resistant vests were made from 21 layers of silk. The silk would stretch and catch the projectile not allowing it to break through the vest. So, they started using weapons that shot the projectile faster, not heavier. The projectile would "snap" through the silk. The speed increase didn't give the silk time to stretch. So, they had to start making the vests from kevilar. What was the point? That when the projectile increases in speed, the rules change. 

I have come to the conclusion that if I were shooting a stick bow, I would out of necessity need the heavy arrow in order to "push" through the target. But with todays, speed bows, the arrow speed "snaps" through the target rather than pushes, be it tissue or bone. Different things come into play when the speed increases What is that magic speed number? Don 't know, but as I play with the T.A.P. program and try different arrow combinatrions, a patter begins to imerge and hard figures begin to prevail instead of what "someone once stated" and "I heard" about heavy arrows out penetrating light fast arrows. Run the figures and see for your self. Old school thought is just that... old school.


----------



## tuffluckdriller (May 27, 2009)

I'm going to throw out one more angle on this...

What about the stiffness of the arrow? I theorize that if the arrow is stiffer, it will penetrate better, because it won't have any energy lost to flex. Whaddya think?


----------



## TEX-O-BOB (Sep 12, 2007)

Bow dude, 

You make some interesting and valid points about the whole speed thing but your comparison on arrow weight is hardly a comparison. Try comparing a 356 grain arrow to a 650 grain arrow. I think you'll see some major differences. Get a 650 grain arrow going 280 fps (which todays modern bows are plenty capable of doing) and you've got a freight train coming at you. One that will "snap" through just about anything. :wink: 

The bottom line is, get any mass going fast enough and penetration is a moot point. MY point simply says this. A heavier arrow will (and by heavier I mean 550 + grains) fly better, be more stable in flight, absorb more of the bows "efficient" energy, stabilize a broadhead better, be more resistant to wind drift, and penetrate deeper. To forgo all those PLUS factors and trade it all in for an arrow that "shoots flat" and gets there in a split second, is, in my "old school" mind, unwise. Better woodsmanship, and smarter shot placement at closer distances is what we all as archery hunters, compound or stick bow, should be shooting for. 

I'd much rather RELY on my instincts, than DEPEND on technology.


----------



## MEEN (Jan 27, 2009)

bow_dude said:


> Yes, the heavier arrow had more K.E. , but the difference was almost nothing (2 or 3).





MEEN said:


> Assuming his new arrows are aluminum, same diameter, and five inches shorter he lost 1.3 ft-lbs.


I used old school physics to calculate that in less than a minute. No need for a machine. P.S your machine was built completely from old school principles and science.



bow_dude said:


> Don't know, but as I play with the T.A.P. program and try different arrow combinatrions, a patter begins to imerge and hard figures begin to prevail instead of what "someone once stated" and "I heard" about heavy arrows out penetrating light fast arrows. Run the figures and see for your self. Old school thought is just that... old school.


I disagree on the old school thought issue but I don't have time to explain. Sometimes things built "better" aren't for the consumer it's to increase the profit margin. Once again, momentum = mass x velocity. As long as you get the same momentum from mass or speed the penetration is going to be nearly the same.



> So, they started using weapons that shot the projectile faster, not heavier. The projectile would "snap" through the silk. The speed increase didn't give the silk time to stretch. So, they had to start making the vests from kevilar. What was the point? That when the projectile increases in speed, the rules change


Your silk example is not very valid because the reason that the silk started failing was because the KE of bullets started increasing. They could have added more mass and the same thing would have happened.



tuffluckdriller said:


> I'm going to throw out one more angle on this...
> 
> What about the stiffness of the arrow? I theorize that if the arrow is stiffer, it will penetrate better, because it won't have any energy lost to flex. Whaddya think?


Yeah some energy will be lost as a result of flex and the frictional force is probably less in stiffer arrows, BUT it's going to be a very very small differents. Like a few mm's.

I don't remember who started this thread but different arrows aren't going to help your friends penetration by much. The biggest problem was his change in draw length.


----------



## swbuckmaster (Sep 14, 2007)

have you seen my head? it defiantly doesn't stand for whooly. Its almost as shiny as the brass plate in pro's head. *OOO* -BaHa!-



CP1 said:


> Does SWBUCKMASTER stand for Short- & Whooly- & master of killing bucks?


----------



## proutdoors (Sep 24, 2007)

The plate is made of solid aluminum.


----------



## swbuckmaster (Sep 14, 2007)

tuffluckdriller said:


> I'm going to throw out one more angle on this...
> 
> What about the stiffness of the arrow? I theorize that if the arrow is stiffer, it will penetrate better, because it won't have any energy lost to flex. Whaddya think?


ill agree. 
If it is stiffer it will penetrate better. :shock:
The more weight you pack the better it goes in. O-|-O 
Length doesn't matter if you have speed! *OOO*


----------



## CP1 (Oct 1, 2007)

SW,
Thats exactly what she said!!!!!!!!!!!!!!!


----------



## TEX-O-BOB (Sep 12, 2007)

-()/>- -()/>- -()/>-


----------



## stillhuntin (Feb 14, 2008)

tuffluckdriller said:


> I'm going to throw out one more angle on this...
> 
> What about the stiffness of the arrow? *I theorize that if the arrow is stiffer, it will penetrate better, because it won't have any energy lost to flex. Whaddya think?*


 :roll: 
Seems like un-necessary condemnation of us "old drillers"  
At least the draw length hasn't changed


----------

