These always seem to become volatile topics, and I've gotten a little tired of seeing them devolve into arguments, but what the heck...

I can't say that I have ever heard a scientifically solid explanation of how 'kinetic energy' translates into a useful measure of real-world arrow performance and/or penetration.

SCALARS are quantities that are fully described by a magnitude (or numerical value) alone, in other words, a one-dimensional quality. KE is a scalar. In other words, an arrow has the same KE even if it is sitting motionless on your dining room table doing nothing. I don't know about you, but I hardly find that a useful measurement of the penetration potential o my arrow.

VECTORS are quantities that are fully described by both a magnitude AND a direction - in other words, multi-dimensional qualities. Momentum (P) is a vector. Vectors are the appropriate measurements of objects in motion, not scalars.

So why has KE become such a popular measurement? A man more cynical than I might guess one of two things:

1) The term was initially used in regards to arrows by someone who didn't understand physics very well, and it was then repeated by people who don't understand physics very well, until it became a commonly-accepted but innacurate factoid.

or

2) KE was grasped at by the marketing machine because speed is sexy, and sexy sells.

But like I said, I'm nowhere near that cynical... ;-)

These articles are worth reading on the subject: http://tuffhead.com/education/formulas_momentum.html

Everything that has momentum has kinetic energy, and vice versa. And you can see that in the figures you posted. Both increase with an increase in mass, so they can't really be separated. It's physics. So what are you trying to convey as they apply to practical application? Our sport has plenty of empirical evidence of the effectiveness of bows and arrows of all levels of KE, and MO. Unless, of course, you are trying to tell us our history is a sham.

Momentum can be defined as "mass in motion." All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion. The amount of momentum that an object has is dependent upon two variables: how much stuff is moving and how fast the stuff is moving. Momentum depends upon the variables mass and velocity. In terms of an equation, the momentum of an object is equal to the mass of the object times the velocity of the object.

Momentum = mass • velocity In physics, the symbol for the quantity momentum is the lower case p. Thus, the above equation can be rewritten as

p = m • v where m is the mass and v is the velocity. The equation illustrates that momentum is directly proportional to an object's mass and directly proportional to the object's velocity.

Kinetic energy is the energy of motion. An object that has motion - whether it is vertical or horizontal motion - has kinetic energy. There are many forms of kinetic energy - vibrational (the energy due to vibrational motion), rotational (the energy due to rotational motion), and translational (the energy due to motion from one location to another). To keep matters simple, we will focus upon translational kinetic energy. The amount of translational kinetic energy (from here on, the phrase kinetic energy will refer to translational kinetic energy) that an object has depends upon two variables: the mass (m) of the object and the speed (v) of the object. The following equation is used to represent the kinetic energy (KE) of an object.

KE = 0.5 • m • v2

where m = mass of object

v = speed of object

This equation reveals that the kinetic energy of an object is directly proportional to the square of its speed. That means that for a twofold increase in speed, the kinetic energy will increase by a factor of four. For a threefold increase in speed, the kinetic energy will increase by a factor of nine. And for a fourfold increase in speed, the kinetic energy will increase by a factor of sixteen. The kinetic energy is dependent upon the square of the speed. As it is often said, an equation is not merely a recipe for algebraic problem solving, but also a guide to thinking about the relationship between quantities.

Kinetic energy is a scalar quantity; it does not have a direction. Unlike velocity, acceleration, force, and momentum, the kinetic energy of an object is completely described by magnitude alone. Like work and potential energy, the standard metric unit of measurement for kinetic energy is the Joule. As might be implied by the above equation, 1 Joule is equivalent to 1 kg*(m/s)^2.

George has it.....What very little KE any arrow has is likely lost to tissue displacement on initial contact and should have very little to nothing to do with arrow penetration. KE is an important term in the ammunition industry because high powered rifle bullets with 2000-3000ft/lbs of KE cause hydrostatic shock, which shuts down internal organs. This obviously can't happen with arrows........Momentum is ultimately superior in attempting to predicate potential penetration, being a vector it actually posses a direction, not so with KE.

Sorry to be pedantic but isn't Kinetic energy measured in Joules (J) whereas Ft/lbs a measurement of a torque moment and to calculate a force, don't you need the accelleration of the mass not the speed of the mass which a chronograph gives you.?

My eyes are bleeding. Math is evil.

The thing I find interesting about this particular topic is the impact of variables. Put a punch cut head on arrow 4 and have it fishtailing to the target and whatever advantage it may have had is wasted.

If all the variables other than weigh and speed are the same for me it comes down to two things - what game am I hunting and what trajectory do I want. If I'm hunting antelope I'm going for the arrow that's around 9-10gpp. If I'm hunting something with big, heavy bones I'm going for arrow 3.

What I see from the data you posted is that even though each arrow is approximately 100 grains heavier than the previous one, there is a significant jump from the KE in arrow 2 to 3. More than between any other two arrows. Could be diminishing returns as the weight goes up.

If you are evaluating a bows efficiency kinetic energy is proably more useful. Momentum has more to do with what happens once the arrow hits its mark. A faster bow shooting the same arrow as a slower bow will always have more momentum, any bow will always have more momentum and less speed if you increase the arrow weight.

A good example 250 grain arrow 240 fps+ 32ft#KE 60,000 momentum 1000 grain arrow 120 fps+ 32fy#ke 120,000 momentum

250 might be good for target but not much good at killing.

I see the trend noted, toehead. I guess I'm confused about what you're asking with "KE or Momentum ???"

What I see with arrow 3 is a tick up in the linear progression of KE and Momentum. KE is a measure of work applied to move a particular mass to a particular velocity. Momentum is a measure of work available due to the velocity of a mass.

KE is a measure. Momentum is a measure. Both are results, not a cause, so would we be better served to ask what it is about the bow and arrow 3 combination that created the uptick than question which measure? Maybe limb design/construction, limb material or arrow spine/flex frequency.

It would be interesting to see test results of a couple more bows to see if they correlate similarly.

An arrow like arrow number 3 flies perfectly (albeit slower) out of my 51# bow. I have killed an elk and a pile of hogs with that set up.

Phil, all bows become more efficient as arrow weights go up. For practical purposes there really is no point where this stops happening.The only thing that stays fairly consistent is the virtual mass of the bow.

Isn't "towhead" the correct spelling? Just busting your balls, but I've been wondering.

http://www.merriam-webster.com/dictionary/towhead

Tow means 'flax or hemp fiber', and so tow headed is literally 'flaxen haired'. This meaning of tow comes from Middle Low German touw (which means 'flax, hemp fiber. A towhead is one with fair hair, typically white-blond. Blondness in youngsters is rampant while scarce in adults, as hair tends to darken with age. Know that this term is not restricted to a child.

I agree. What I was referring the point where the gains start increasing at a slower pace.

Toehead, considering yoru 63# bow... quick math says that arrow #3 is where you broke the magic 10gpp threashold. Coincidence?

KE is a measurement of energy in a system (e.g. potential energy vs. kinetic energy, both add up to 100% of the available energy in the system).

Momentum is a measure of a moving body's tendency to remain in motion if acted upon by an outside force. The higher the momentum, greater amount of WORK is required to bring the object to a stop (WORK being equal to FORCE times DISTANCE). If you want to know how much WORK is needed to stop a given object, you must first calculate the momentum.

All else being equal, Momentum should be a better predictor of penetration than kinetic energy, as there is a 1:1 correlation with the amount of WORK required to bring the arrow to a stop.

All I know is when my arrow hits something it dies... How much penetration are you guys looking for? 90% of the time. My arrow is stuck in the ground dripping with blood. So let's put the calculators away and shoot our bows so we can try to avoid those pesky shoulder blades shoot straight my friends.

Increase your momentum where it needs to be and you want have a "pesky" shoulder blade.

I used to do a lot of custom gunsmithing in the past and I ran into the same kind of questions from gun guys. Id have to say that 75% of these guys wanted more gun than they would need. One guy complained that what I got him into caused far too much tissue damage. I asked him how far away he was from the deer with his 7mm Mag. 20yds he says. The gun was built for 200 plus yds where he hunted them in Wyoming. My guess is that we need only enough energy to pass thru the vitals on a broadside shot on any particular animal. Thats very different on hogs and really big boned prey due to the difference in the arrows resistance to penetrating the vitals. I told my customers to first choose the bullet they wanted to use before anything else. Id have to say its very close to the same advice with arrows and broadheads. Tune to the game you will hunt.

Dustin...are you referring to the fact that the heavier arrow although traveling slower has more momentum as well as producing more kinetic energy that the lighter arrow traveling faster?

Thanks Toehead, for some fact amid all the conjecture. I recall Dr. Ed Ashby concluding from his 30 year broadhead penetration studies and larger game, than 600 grains might be an important threshold from moderately heavy hunting bows. Your results seem compatible with that. - lbg

Kinetic energy is useful in determining how efficient your bow is. By measuring the kinetic energy,KE, and dividing it by the potential energy, PE, you will get a number that represents its efficiency. In other words how much available energy that you have stored up in the bow when you draw it back is actually delivered to the arrow when you release it. Determining those two energies involves weighing the arrow, and measuring the arrow speed for KE, and determining the PE by creating a force-draw curve on a graph and measuring the area under the curve (not easy, but doable). 80% is in the ball park, plus or minus.

All I know is my carbons out penetrate my old woodies.

All I know is my carbons out penetrate my old woodies.

Toehead: I haven't read all the posts, so this might have been mentioned.

The one factor you failed to address in your original post is all of your figures are based on velocities at the bow. An arrow looses velocity extremely fast, in particular light arrows more than a heavier arrow. Which is the main reason that momentum is more important than K.E.

I did some velocity experiments several years ago, using the same bow 57# and a 400gr arrow and a 500gr arrow. using a shooting machine and shooting through two chronographs at the same time, the second one set at 16 yards from the bow, the first at the bow. I shot 10 shots with each arrow switching chronographs after 5 shot to account for variances in machines. The light arrow lost 14% of its velocity at 16 yards while the heavier arrow only lost 7%. I intended to try some heavier arrows but never got around to doing that. Bob

Yep, drag due to all forces more quickly deccelerates the lighter arrow. The more it slows, the less momentum it carries... the less momentum, the greater the effects of drag... continually until stopped. It happens in air and in flesh.

Glad to see you doin your own homework Toe.. Good stuff.. Have you been paying attention to actual penetration differences in the target as well?.. I like the discussions.. I would personally add in my own preferences when final decision of hunting arrow was being made as well.. That being flat as trajectory as possible.. Reason being, I use one set of arrows for everything..Hunting- target- 3d... I see trouble if you target with one set and switch for hunting.. But that is just me and my demands....

Makes me mad I can't remember what I used too, I knew the stuff arrowmkr added but forgot it. I think what he added lends credence to smaller diameter arrows penetrating better assuming they are of sufficient weight etc.. Less drag less slowing down yadda yadda yadda

toehead: I think a lot of your questions can be answered by studying the laws of Physics. Archery is all about physics and physics controls every aspect of it. One of the very first laws you learn is "An object at rest tends to stay at rest, and an object in motion tends to stay in motion" The heavier that object is the more that law applies.

Look at a simple ballistics chart. pick any cartridge. look at the lightest and the heaviest bullet for that cartridge, check the velocity at the muzzle then at 100, 200, 300, & 400 yards. The first thing you will notice, the light bullet at the muzzle will be a lot faster than the heavy one, but at 400 yards the heavy one will be catching up with the light one and will have much less drop in trajectory, because it is retaining its velocity longer than the light bullet. Physics, Physics, Physics!!! Bob

Arrowmaker, whay would the bullet with more momentum have a flatter trajectory? It will be accelerating toward earth at about 32 fps. Whichever takes less time to reach the target will have the flatter trajectory.

toehead: I think a lot of your questions can be answered by studying the laws of Physics. Archery is all about physics and physics controls every aspect of it. One of the very first laws you learn is "An object at rest tends to stay at rest, and an object in motion tends to stay in motion" The heavier that object is the more that law applies. Isn't that a cialis commercial?

I'm still a little confused as to how Knetic Energy can be measured in foot/pounds (ft/lb) What does the feet part represent and what does the pound part represent. Could someone explain it to me please .. thanks.

Phil, if you take a measure of your draw weight every inch and then ad them up you will get a measure expressed in inch pounds, divide that by 12 and you will get foot pounds. If you are measuring the kinetic energy you can express it any number of ways. When you shoot an arrow the weight of the arrow combined with how fast is traveling tells you how many foot pound of energy went into the arrow. If you lift a dead weight that weighs 50# 1 foot off the ground you have 50 foot pounds of potential energy. If you lift it 10 feet off the ground you have 500 ft pounds. It is just a measure of work.

toehead..."Remember, the equation for KE relies heavily on speed which is a factor that is constantly decreasing."

your right, and that is why i could never understand extreme arrow weight without an increase in draw weight to keep the speed up.

My philosophy has alway's been. If i want to shoot heavy arrows, i use a heavy bow. If you want to see something, Go back to your calculator, up the bow poundage so you can drive the heavy arrow as fast as the lighter bow, arrow combo...

i'm not promoting heavy poundage bows, unless you can handle them. but the numbers won't lie. keep your speed up and a heavy arrow gets pretty awesome in the way of penetration.

i simply won't argue about that...it's common logic, that don't require a physics degree to understand.

badger: I would suggest to you also, to look at a ballistics chart. its there in black/white. Its shows bullet drop in inches at the various distances. Bob

Arrow, I am sure it would and they would have to base that on how fast the arrow was traveling and how long it would have been in the air at whatever point they are making the calculation. I just said the bullet in the air the shortest amount of time will have less drop. Unless the bullet has lift built into its design it starts falling the instant it leaves the barrel.

Thanks badger .. that makes things much clearer ... appreciated

i can't really argue with that logic toehead.

i usually start getting confused the minute KE = 0.5 • m • v2

where m = mass of object

v = speed of object

shows up on here....

I'll let you guy's that know about this scientific stuff do the calculating.....

Bottom line is this....the heavier arrow is going to penetrate the most. It is not used the most simply due to less than desired speed ans trajectory.

And that, for deer sized game, we only need to penetrate about a foot to get through the chest.

That is true. Then the preferences continue... by either desiring to just be content with the minimum that is "needed" or continue in a mode of improvement that will also be needed.

Preferences rule regardless of what it best.

Sapcut, true except that I'm not sure that folks are willing to settle for the minimum. I just don't know what the minimum is. It's for sure that many get passthroughs with light bows. But some don't get passthroughs with 54#. There are so many variables that it is impossible to draw a line. I'm confident with my setup but that doesn't mean it couldn't be better.

Badger: I just checked the Hornady ballistic chart for the 30-06 a 125gr sst with a muzzle velocity of 2700fps drops 61.9" at 500yds, that cartridge loaded with a 165gr interbond with a muzzle velocity of 2710fps drops 49.3" at 500 yards. So please don't tell me its not possible. Its no different with an arrow, as I said before its governed by the laws of physics. Bob

Phil, Perhaps the "minimum" or what is "needed" is sometimes more influenced by what we just like, what we're comfortable with or even because it's all we've got because my cousin won it in high school by selling the most magazines...kind of thing. Or at least that was my deal in 1983.

"There are so many variables that it is impossible to draw a line. I'm confident with my setup but that doesn't mean it couldn't be better."

Now that is a stinkin true statement that applies to me as well.

I agree with what we like or influences of others. Peer pressure and hero worship play a huge role. Although Fred Bear liked 9 gpp. I would expect that to be the "norm" rather than 10.

aromakr, In your example you have the 125gr bullet traveling about 500fps below its maximum velocity and the 165gr bullet within 100fps of its maximum velocity.If loaded to equal pressures the 125gr bullet would drop about 15" less than the 165gr bullet at 500yards and the 165gr would have about 300 ft/lbs more energy than the 125gr.

To develop a draw-force curve, you'll need to determine the draw weight (force) at each inch. Then plot it out on graph paper: X axis = draw length and Y = draw force. You will need to measure the area under that curve to determine the PE. You can start out by using inches on the X axis, but will eventually need to convert to Feet. When you measure the area under the curve the units should come out in Foot Pounds. What I do is to carefully cut along the curve line, and then along X and Y margins. Then I weigh it and also weigh a square inch of graph paper. To add weight, you can glue the cut outs to heavy cardboard. and weigh them. The weight comparison is a measure of the square inches under the curve, which you can convert to Foot Pounds. YAY!! you got the PE.I'm sure there is a computer program that will do the same thing, but I don't know of it. I'm not sure if they are around but there's an instrument called a polar planimeter which is used to measure areas under curves.Very handy and you don't need a scale.

Ol Archer, you can also just add up the totals for draw weight at each 1" of draw and then divide it by 12.

Try shooting a 4,000 grain arrow through a chrono, figuring out how much ke in the arrow and then call it 95% of draw force, you will probably get closest.

The momentum equation is the one I think describes what arrows do the best because in that equation mass and velocity are directly proportional. As velocity or mass increase so does penetration. Jawge

KE sounds fine, but remember that since it is a square function of velocity, you lose it at a square of velocity loss. In other words, a ten percent loss of velocity costs you 19% of KE.

This is why the KE devotees shoot tiny fletches ;-)

The KR of a .17 Remington is 1243 ft. lbs.

Is anybody going to take one of those elk hunting?

TBB

bullets and arrows cannot be used in comparison when talking trajectory, KE , or momentum. possibly on paper they can, but that is about it.

bullets spin at a high rate of speed in order to be stable, BC or ballistic coefficient and sectional density, plays a huge part in long range trajectory...in otherwards a bullet with a high BC of the same weight, driven at the same speed, will alway's have better trajectory, more KE at longer ranges.

worthless info for us trad bow shooters. try stabilizing a 400 gr of arrow at 2000fps, regardless of FOC.

now i'm no physics major, but common sense tells me your going to have problems.

bullets also kill by hydrostatic shock,and hemorrhage. arrows kill by hemorrhage alone.

arrows travel at such a slow rate of speed compared to a bullet.

A 500 gr bullet out of a 458 win mag traveling at around 2100fps will have approx 4900 lbs of energy.

a 516gr 2018 aluminum arrow in comparison traveling at 180 fps out of a 55# bow, will have a 10.1 gpp around a 12% FOC but only around 37 ft lbs of energy.

Whats this all tell a camo ball cap wearing country boy from PA. ??

It tells me i can kill anything in north america with either, but arrows aren't bullets.

And all the scientific humbo is best left to pale skinned scientist, in horn rimmed glasses.

Oldarcher said " To develop a draw-force curve, you'll need to determine the draw weight (force) at each inch. Then plot it out on graph paper: X axis = draw length and Y = draw force. You will need to measure the area under that curve to determine the PE."

This is the exact protocol we use in our biomechanics lab to quantify the values of a force acting on a body to generate the "force/ time integral

If anyone would like to post the draw weight values of their bow at different draw lengths, we can compare the two methods of calculating the potentiel energy containe within the bow.

see told you i should leave the calculations to the scientist...the gpp of a 516 gr arrow from a 55# bow is around 9.4 not 10.1

I'd say most of us are way over our head discussing this stuff.

I was building forms on a bridge once, an engineer was watching over me, pumping me full of all sorts of load, span, this and that, re-bar info, and everything else under the sun. It was near 100 degrees sweat ran off the brim of my hardhat like water. I was feeling kind of miserable, so I finally looked at him pulled my claw hammer out of the hoop in my nail bag offered it to him and said.

"if you know so stinking much then you build it" He looked at me a good long while then answered. "that's not my job"...

I replied your dog-gone right it's not, nor could you build it.

I'll make you a deal, i got 30 yrs building experience from houses to 12 story buildings to bridges...You go back to the office and do the figuring,and let me do the building, because this hammer here is what it all boils down to.

i look at this topic about the same...you can calculate all you want, but the proof, the real world results, and the actual results are found in the field.

Ya can't escape it. Physics apply to that hammer too, bud :^)

"And all the scientific humbo is best left to pale skinned scientist, in horn rimmed glasses....."

shade', with all due respect, I very much disagree. "Science" and "fact" are synonymous and ultimately useful to everyone. And while I'm certain that at least most everyone reading this doesn't posses a doctorates in physics, some of us are able to extrapolate those facts that science provides and apply them to "the real world". That we are laymen doesn't mean we should be ignorant or unable to comprehend. What I don't understand is where I start asking questions directed at those who have the answers.......It would be my assumption that's how we all should learn.

I have yet to see anyone who is all bothered by this stuff, actually make up a bunch of arrows and watch hands on at different yardages,the actual performance of penetration, arc etc.. Bunch of lazy ass scientists...... Said with love ofcourse..

not denying science, or even denying it's benefit...

if you keep in mind that it is normally calculated in a controlled environment, and really only serves as a place to start, to get maximum efficiency and gain a reasonable understanding of the how and why of how things work.

But when we go into the field which is in no way a controlled environment.

Hunting is not a controlled environment, physics tell us scientifically what "should" happen out there but we all know it does not alway's work that way.

Another example would be air and water and temperature content in concrete.

Science tells us what amount "should" be optimal and break at the highest PSI.

Experience in the field tells me that it doesn't often work that way. I've had inspectors fail concrete due to to high air, slump ect...but my gut tells me it will be fine, we'll chance it and see how it breaks in 7 and 28 day's..and it breaks above the listed requirement.

Jeff while physics might apply to a hammer. All the physics knowledge in the world won't make a carpenter.

nor will knowing how to calculate KE or momentum make a bowhunter.

experience makes carpenters and bowhunters, not book knowledge.

That was my point.

Stan ... some of us "lazy ass scientists" are also life long archers ....Said with love of course :)

"I have yet to see anyone who is all bothered by this stuff, actually make up a bunch of arrows and watch hands on at different yardages,the actual performance of penetration, arc etc.."

Well, you're welcome to come over to my backyard any time, Stan, cuz that's what's happening just about every day!

;-)

The area under the curve gives potential energy. Some of which (not all, depending on efficiency of the bow and arrow combination) is converted to kinetic energy and imparted to the arrow. Now, the arrow has the kinetic energy from the bow but the arrow possess momentum, as well, which directly proportional to mass and velocity.

The question is... does penetration increase as a square of the velocity?

Some think yes. To them, velocity is very important. Increase velocity get a bonus on penetration.

...or is penetration directly proportional to mass and velocity? In other words an increase in either affects penetration equally.

Experimentally, should be pretty easy to determine this. But like why bother? Is it easier to drive an 16 d spike with a 16 oz hammer or a 12 oz?

It is momentum for me.

The principle of moderation...

Well, those who have gone before us seemed to understand that 8-11 gpp is really ideal. That is what I believe.

For a mind game, trying to shoot rebar out of a 50# bow. Try shooting a long straw.

Either situation would be dismal.

470 grain arrows out of my 47# hickory self bow fly pretty nicely.

Jawge

In relation to my last post...i pay attention to science and the how and why...but i also realize that things like physics, or any science for that matter is often not an end in itself, or an absolute in all circumstances.

and that every time you enter another variable in an equation it has the potential to alter the outcome.

"What I don't understand is where I start asking questions directed at those who have the answers.......It would be my assumption that's how we all should learn."

Hence the reason roger has his main man Dr. Ashby on speed dial...:)

"I have yet to see anyone who is all bothered by this stuff, actually make up a bunch of arrows and watch hands on at different yardages,the actual performance of penetration, arc etc.. Bunch of lazy ass scientists...... Said with love of course.."

Said because you're one of them.

"Well, those who have gone before us seemed to understand that 8-11 gpp is really ideal.

I think that has to do with how "those" like to see their arrow fly not because they penetrate better than other arrows. How many people have chosen to not use a 12-14 gpp arrow simply because it would not go in a animal deep enough. I think all of our arrows are far from that end of the spectrum. Point being, the main reason some say "10 gpp" has to do more with the desired flight of the arrow than anything else.

hence...."470 grain arrows out of my 47# hickory self bow fly pretty nicely."

"Hunting is not a controlled environment, physics tell us scientifically what "should" happen out there but we all know it does not alway's work that way."

Agree. It's all about increasing our chances of consistent success.

George...I have found that balance in all things is often best.

To much HP in vehicles..they sure go, but they also sure tear up transmissions, rear ends, u-joints and cut back on engine life.

strong drink?....why comment on the effects of to much?

food?....same thing, moderation and balance is best for most.

financial spending? ha..look no further than our Gov't for that answer.

Many things are all around best when balance is practiced. I reckon arrows are no different.

actually with my draw length of 27" and 54# bow i'd have to choose out of the ordinary extra long arrows, heavier than normal point weight ect...to get over 600 gr

I'm staining some douglas fir right now and i'm figuring the total with 160 gr points is only going to be around 548 which is plenty heavy for me.

You guy's that are shooting over 600 must be shooting heavier poundage bows, stiffer heavier spined arrows, and really heavy points above normal?

[[[ From: Stan Date: 19-Jul-14 - "I have yet to see anyone who is all bothered by this stuff, actually make up a bunch of arrows and watch hands on at different yardages,the actual performance of penetration, arc etc.. Bunch of lazy ass scientists...... Said with love of course." ]]]

Heh Heh, you obviously don't know me. 8^)

I have, and that's why I shoot the arrow setups that I do.

Rick

"You guy's that are shooting over 600 must be shooting heavier poundage bows, stiffer heavier spined arrows, and really heavy points above normal?"

I'm currently shooting a #55 @ 28" bow (my draw length is 28").

My arrows are GT 5575 cut to 28.5" with a total arrow weight of 655 gr. Point weight is 365gr.

That is what I'll be hunting with this year.

I'm currently shooting 67# @ my 29.5" draw.

7595 GT Trads cut 30.25" to BOP. I have 1" 2216 footings on both the point & nock ends. I am using the standard GT inserts with 50gr add in weights on them, and T-4 Turbonocks with 3X4" fletching.

Total arrow weight - 625gr with 18% FOC.

Rick

"What I don't understand is where I start asking questions directed at those who have the answers.......It would be my assumption that's how we all should learn." "Hence the reason roger has his main man Dr. Ashby on speed dial...:"

......or the reason I wouldn't bother asking him anything at all with regards to science, as he clearly states his work is not scientific. A matter for perspective, I suppose.

shade', then according to your logic we must discount everything scientific, as it's concluded in a controlled environment, and the 'real world' has obvious variables. Sorry, but it's within that variation that the actual facts obviate the truth.......They have to as they aren't mutually exclusive. Your actually missing the entire point of science.

Now I know why islept through physics.,this makes my head hurt

That was my next statement...it would all circle back to what has been said already decades ago, by folks who had hands on experience... Sap.....this bothers me not, Other than, well you know already..

i'd say bottom line is? best to use what you have the most confidence in.

Dustin, I'm not doing this for an 83rd time. I've given you Ashby's direct quotes regarding all of this and still you deny it......Your the only one, btw.

If Ashby's research is not "Scientific" by however one defines that....Does that make the Ashby research information worse, null and void, inadequate, etc. than any other research collected? Or does it continue to be the best information any of us have seen?

"I'd say bottom line is? best to use what you have the most confidence in."

Couldn't agree more, shade.

Sapcut, It isn't null and void at all. To me, it goes right along with the other information out there. Ashby has killed and tested on a large number of animals but volume alone doesn't make it the best information we have seen.

If I were a novice and wanted to find information on what to use for elk, I'd consider Ashby's work but I'd consider at least as much, if not more, the work of folks that have killed a lot of elk. Same for deer, same for pheasants. If I wanted to find information on what works on big-boned, large animals or large hogs with heavy shields, Ashby's work would be an excellent source but not the only source.

Fortunately, I don't have to worry about killing a buffalo or old boar hog.

To his credit, I know for a fact that Dr. Ed would never consider that his information should be anyone's only source, either. I think that sometimes the singularity of his study gets blown out of proportion, and what tends to get forgotten along with that is the evidence of numerous cultures all over the world, and at various times throughout history, that have used high-FOC arrows as well. None of this is particularly new or revolutionary, and he'd be the first to admit it.

i'd say that's pretty accurate smithhammer, i alway's felt he was simply stressing what others already said, and used in field experience to further enforce his point.

My take and opinion mirrors Phils post...i respect his work, and i really don't doubt it, however i also respect the experience of others that have been very successful with lighter arrows broadheads ect...for instance i would assume Ashby would frown upon replacement blade heads, yet i personally have shot through the shoulder blades of two deer, with a 125gr muzzy. And i could have used the one over again, the other had a bent blade, but the main head was fine.

You see i'll use replacement blade heads on occasion, are they as reliable as a two blade zwickey, grizzly, magnus or ace? i'd have to say over all probably not, but i doubt the average guy would have trouble with either.

i do have one old magnus two blade that has seen the inside of a deer's chest cavity numerous times..it's getting to be somewhat of a lucky charm maybe? It don't weigh 125gr anymore from being sharpened so often over the years but it's good for another. This year maybe huh?

lot's of us out there come fall, with slightly different gear. point is keep an open mind, use good equip, shoot straight. and don't over cook your venison.

"Jeff while physics might apply to a hammer. All the physics knowledge in the world won't make a carpenter."

No, but some IS necessary... a considerable amount actually. The best carpenters, and those I would prefer to work with and hire to work on my house, will have a good working understanding of it. Much of it may come from experience, mentors, word of mouth, etc... but it's in the books too :^). Those who built the garage here at the house I just bought DIDN'T... and now I have a lot of work to do to repair the damage that insued and keep it from happening again.

"Experience makes carpenters and bowhunters, not book knowledge. That was my point."

Well, one look at my garage should reveal that carpenters aren't automatically blessed with physics knowledge when they assume the title of 'carpenter' either.

IN that experience, in both carpentry and bowhunting, and well, most everything, IS physics. And that is MY point :^)

Fighting physics won't get you far. Neither will sloppy science and rookie reasoning. What's an expert? Well, X is the unknown quantity and a spurt is a drip under pressure. Doing something the same way 1000 times is just one experience, repeated.

Many opinions may have limited value. A fool can have only foolish thoughts. Stupid is as stupid does. We learn from considering many sources and applying trying to apply sound judgment. - lbg

i think your misunderstanding what i typed jeff. i'm not opposed to science or physics...My thought was in fact. Real life is not alway's in a controlled setting. Variables can change outcome, being able to modify or change for optimal result is alway's the goal.

As far as your garage, sorry to hear that, sadly it happens. Yes knowledge of load,span, bearing surface, ect is needed as well as being able to properly read blueprints ect..and then actually build it and have it come out plumb, level and structurally sound. And finished in a timely manner.

But with all due respect. Jeff you could study those things for 6 years in books, and without actual on the job experience, you could never even come close to a competent experienced carpenter.

And to put it in simpler terms.

You could have a masters degree in physics, you could be a noble science winner.

But if i handed you a brick trowel, and said build me a foundation. or a hammer and said build me a house.

Or a set of blueprints and say ok bud build me this six span bridge.

i doubt the foundation or the house would be plumb level or structurally sound. And i doubt you'd ever get the bridge built, i doubt you'd ever get the steel racks tied without having a twisted up stinking mess.Let alone build the abutment forms, and get it poured without it blowing out. Or get the concrete deck poured to the right percentage slope, and have the proper camber, Where in a book would you ever learn how to run a Bid well? (if you even know what that is?) doubt the parapet walls would be straight, could you even build a transition form out of plywood for the end? doubtful.

But with 30+ years of experience and a high school education, i can and have, and am still doing all the above.

So while you guy's are all discussing your formula's and fretting over KE and momentum, and trivial differences of a couple pounds of KE.....some of just go hunting. and harvest deer like they have for decade's.

Hope that didn't sound to harsh, wasn't intended to be. , i think i'm done with this one, i'd rather take a hike on the mt.

take care.

Roger, please, even if it will be the 83rd time, post the information. I have not seen that as of yet. Also, I am curious as to what your science background is to suppport your claims. Clearly, the Ashby studies are not perfect. There are a multitude of confounding variables, but clearly scientific research principles have been used.

Well to discuss this facet of archery one needs some knowledge of physics and he or she has to be an archer. IMHO.

At one time, one of my science colleagues was a pHD in physics. I asked him, for some reason, how much force was at each end of the nock of a 50# (self) longbow.

He said 25# on each end as did another colleague.

We know that can't be correct considering how narrow some self nocks are. 25# of force would break them easily. Besides nocks only move up and down a few inches over the course of the draw.

Gotta have both.

Jawge

Remember the v is squared in KE. Let's calculate KE for a v of 2.

Mass is constant.

0.5 (2) squared=2

Now for 3.

0.5 (3) squared= 4.5

So anecdotally, have you witnessed such a great increase in penetration with a small change in velocity?

I have not.

Jawge

Shade Mt, I think you're on the wrong forum. This isn't about building bridges.

lets not forget that the arrow is spinning in flight to some degree, so you have to recognize the equations that explain how the rotation effects k.e and momentum. or, like shade mt. suggests, it may be more worthwhile actually killing some animals instead of committing hours and hours to theory. theory is helpful in some respects, but, is it more telling than hands on experience? that may be the better thing to debate. no? then consider this-- If you put a lot of work into rotating an object, the object starts spinning. And when an object is spinning, all its pieces are moving, which tells a physicist that it has kinetic energy. For spinning objects, you have to convert from the linear concept of kinetic energy to the rotational concept of kinetic energy. i haven't seen anyone post the proper formulae for this reallity? why, when we have offset fletch and spin nocks and all arrows rotate to some degree. and remember that some arrows are barrelled in profile, some are tapered and any variation of mass requires a different formula to be inserted to calculate that portion of the arrow to make a meaningful conclusion. personally, i would rather just go shoot stuff.

For me, it's how much momentum do I need to get consistent passthroughs on deer I'm hunting. Any more than that is wasting speed which transfers to less than a flatter flight trajectory.

Badger, You're right if the curve is pretty much a straight line. I think long bows come close. And you're right with the really heavy arrows, or should I say "telephone poles". The chrono would probably get tired of waiting for the second blip. Good stuff though.

i doubt anybody here is denying the laws of physics are they? But i think what many are simply stating myself included, is Each one of us uses what we prefer. And for me i choose an arrow that gives sufficient penetration without sacrificing trajectory to much.

Why is KE and momentum considered and trajectory is not? If we really want to get scientific,(frankly i don't) shouldn't we be considering trajectory as well for optimal performance.?

And while i have no doubts that Dr Ashby has much experience, How on earth are we going to explain all the thousands upon thousands upon thousands of deer, Elk, Bear, moose that have been shot with what Dr Ashby claims as insufficient? good grief were they all Flukes!! Come on now we are not that naive are we?

"How on earth are we going to explain all the thousands upon thousands upon thousands of deer, Elk, Bear, moose that have been shot with what Dr Ashby claims as insufficient?"

Now that is a good question because Ashby did specify many many times throughout the years and years of research that there is no way possible to kill an animal without sticking to the equipment requirements he detailed in his work....you know like so many of you guys have so arrogantly twisted.

"How on earth are we going to explain all the thousands upon thousands upon thousands of deer, Elk, Bear, moose that have been shot with what Dr Ashby claims as insufficient?"

With all due respect Shade Mt,Dr Ed Ashby never said that.He has just studied penetration to find what could detract from or add to it and supplied that information to anyone that wanted to use it.Now,some on internet threads may have gone that far but I haven't read or heard Ed Ashby make those kinds of statements.

Jim B, they know that, we know that, all God's children know that... but making those types of statements, as Shade Mt did is what they do to Defend ( not that they need to but they do) the equipment they prefer to shoot.

That is what is most entertaining about Ashby information threads....seeing the new ways and statements the opponents feel they need to use to defend their choices. Instead of just saying...."I like to shoot what I shoot because I simply like to shoot it and I don't care who shoots what or who researched what or whether it is the best for penetration big bone or not."

I don't intend to twist Ashby's work at all. There are some of his proponents that do tend to bring his work in as "requirements" for bowhunting. The real problem I see in this argument are the two extremes. I believe the majority of us appreciate the work Ashby did but consider it only one piece of the available information.

Sapcut...I never once put Ashby's work or study's down, not once have i ever Bad mouthed or doubted him. What i was saying before you twisted it around my friend, is that Ashby made some valid study's but i hold his ideals no higher than the "thousands upon Thousands" of successful hunters that differ a bit in their equip from what Ashby prefers.

It is guy's like you that Quote Ashby this Ashby that..NOT ME! I can't remember ever Quoting him?

I respect the man, but lots of guys have shot game animals and didn't experience the failures often spoke of. That is what i meant when i said how do you explain that.?

Iv'e read a little of his writings, it's interesting yes. I could be wrong but wasn't most of his study's done on African game? i kinda recall him writing about shooting through Zebra scalpula's /

And i gotta say here ...I'm not putting the man down ok, understood?

just curious if he ever did any study's on game we often commonly hunt here, whitetail, black bear ect..

Understood. And I'm not saying or implying anyone SHOULD follow anything anyone says.

I believe some of his work did include smaller deer size African game.

And yes I agree it is very interesting information that we all can do what we wish with it.

Actually shade, that seems to be a common misconception that coninues to get perpetuated by his detractors as a supposed reason why the study doesn't apply to your average hunter in N. America. It's simply not true.

Direct quote from Dr. Ashby in the video link below (at 2:32): "...it's a misconception most people have that the study only deals with huge animals. the study started with SMALL animnals. In the original Natal study, over 90% of the animals were impala, nyala and warthogs, which are about the size of whitetail, small mule deer and feral pigs...."

If this subject interests you as much as it appears to, I would recommend watching all the videos in the series. Here is the link to the first one:

https://www.youtube.com/watch?v=VAeuVFSHA1E

' thanks, and yes i wouldn't mind watching those. take care

If I remember right,a lot of fairly popular broadheads failed in the Natal testing on whitetail sized animals.I believe that peaked his interest,to do further testing.Later,after things went "south" over there,I believe Doc Ashby moved to Australia.The test media then became water buffalo.Just going on memory here guys so take it with a grain of salt.

Jim B, If not mistaken, the study began due to the wounded unrecovered animal rate continued to be unacceptable and then wanted to know what could be done to decrease that with archery equipment. So they dove in the work to determine what would be the best arrow/broadhead/etc. combinations to increase lethality.

Perhaps he thought if they could find out the best equipment to penetrate the largest animals available then anyone who was interested could work backwards applying it to anything they hunted. I think its reasonable to conclude that the results on a water buffalo would be even better results for anything smaller. ??

I don't think Ashby was looking to label some equipment 'insufficient', rather, he was trying to find out what was 'optimum' for penetration. He hit upon a certain combination of arrow characteristics as giving the most reliable penetration under less-than-ideal circumstances, like if/when your shot hits hard bone instead of soft tissue.

Given a perfect shot, most anything will kill. It's the less-than-perfect shot that sorts out the good from the best.

I'd say anytime a guy strives to decrease the percentage of wounded game he has his mindset heading in the right direction.

What's this, no pictures?

.458 win is great for cape buffalo. Therefore a good whitetail round to help insure recovery?

"458 win is great for cape buffalo. Therefore a good whitetail round to help insure recovery?"

If you so choose. Your recovery rate would not decrease would it?

Actually it may. But that's because of how bullets work versus arrows and is a topic for a different forum.

It sure would be more painful to shoot and not worth it.

:)

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