Trad Gang

one arrow weighs 688grns and is traveling 135 ft/sec and has 27.85 ft-lbs of force at release . Another arrow weighs 547grains and is traveling 150 ft/sec and has 27.34 ft-lbs of force at release.
The arrows are identical in cross section. Which arrow will have more force when it hits a target 20yds away?   :banghead:

These are the actual measurements out of my bow. I just got a chrono yesterday and I'm trying to figure out which arrow to shoot. One arrow is 13.36 grns/lb the other is 10.62 grn/lb. I was really surprised my bow imparted basically the same amount of energy to both arrows.

The force, energy, momentum etc in your arrow is composed of mass times velocity. When you hit the target the velocity will bleed off. The mass will not. Invest the energy in mass. In other words shoot the heavy arrow. Dr Ashby reports are a long read but more than worth the time. Check 'em out.

JW

Too many real world factors to calculate and consider to render the exact correct answer from me. Need to know the actual velocity at impact. Jim

All things being equal, the heavier arrow will arrive with more whump at 20 yards.  The heavier arrows carries momentum farther and is probably more important than KE as far as hunting is concerned.  Hope this helps.
Jack

I don't know how to figure momentum exactly ,but I know that when you multiply the ft/sec X grns the lighter arrow has 82,050 units and the heavier arrow has 92,880 units. That's about 13% "units" more in the heavy arrow.

So from my other post it was decided the heavy arrow will lose speed slower than the light one. So the farther these two arrows travel the more power the heavy arrow will have when compared to the light arrow. Am I getting this right?

Zradix, if you shoot two arrows out of the same bow, the heavier will absorb the most energy.

engery = mass x velocity^2.  At the release from bow the heavier arrow has about 1.8% more energy.

I agree with Zradix.  The drag is proportional to the square of speed.  The lighter arrow would slow down in faster rate because of more drag from speed and less mass to counter the force.  I don't think the arrows will reach "terminal velocity" when reaching at 20 yards.  Just need to find a formula to simulate the flight.

The 688gr arrow will pinatrate more. The 547gr arrow will shoot flatter. How much penatration do you need? How flat do need the arrow to shoot?
Steve

The very bottom line is the heavier of the two is the BEST option for several reasons.
Based on quality research, there is no comparison in a 688 gr. arrow and a 547 gr. arrow when it comes to penetration and bone contact.

Zradix,  You really want to calculate "Hit Poundage" and forget the Kenetic stuff.  With your exact figures above the 688 gr. arrow hits with 41# of force and the 547 gr. arrow hits with 37#.  It's the old thing of would you want a 250# guy to run into you running 10 mph or a 100# guy.

The heavy arrow momentum is .412 and the light .364.

What would concern me is at 135 fps the heavy arrow will have a good deal more arc.

For close shots at 15 yds and under it won't matter and the heavy will pound em.  But at 25yds, you may be under the target.

Mike

no contest - heavy arras are yer best huntin' buddy.

the question might be a compromise for trajectory.  heavy arrows have more arc and that might shorten yer effective shooting distance.

10gpp is my minimum, and there is no maximum unless trajectory becomes an issue for consistent accuracy.

ymmv!

Penetration is most important. Momentum ( mass times speed) is a better indicator of penetration than than kinetic energy (mass times speed squared). A formula that squares the speed is biased toward speed but that doesn't translate into penetration. Bottom line, the heavier arrow will penetrate better. However your "light " arrow is still 10gr per lb. of bow weight which is plenty heavy for whitetails. Sorry to be so long winded.

Thanks for all the help guys. Yeah I have to admit I'm a little worried about overkill. Don't need to use an elephant gun on a mouse. I'm wondering if the 10gn/# will pass thru just like the 13 on whitetails.

It may not be that simple.   :)    Depending on your bow, the efficiency of the bow may change with the arrow weight, which puts another factor into the equation. Longbows tend to increase in efficiency with increasing arrow weight, but a recurve may not.

I'm shooting a 1957 or 58 Bear Kodiak recurve 60" 52lbs at 28" heavy arrow is ash, light arrow is cedar. I'm shooting a Abowyer brown bear broadhead (175grn+15grn lead)

I would think that a 10 gr setup should pass through rib cage hits on whitetails most of the time,if you are tuned for good arrow flight.Wind can change things just like an untuned arrow.

I'm not sure there is such a thing as overkill,though.It is part of the choice to be satisfied with the trajectory though.

I have been shooting 13 gr per pound arrows out of several bows and don't have to think about trajectory out to 20 yds.I would rarely shoot at game past that range but if I want to shoot farther,I verify with my tip.At 25 yds,4" under and 30 is point on.

I shoot all recurves and every one penetrates deeper with heavier arrows.They also shoot quieter.

Both your setups are good ones.You can't make a bad choice there.Just juggle a few elements to help you decide but forget the kinetic energy formula.

Dumptruck & Hugo both traveling at 40 MPH. Which is easier to stop? Why?

QuoteOriginally posted by Zradix:
Thanks for all the help guys. Yeah I have to admit I'm a little worried about overkill. Don't need to use an elephant gun on a mouse. I'm wondering if the 10gn/# will pass thru just like the 13 on whitetails.

i think you need to stop thinking about this, yer gonna hurt yerself with all these thoughts.

10ggp or 13gpp? - take yer pick, go out and make meat.

Just for the record, drag is proportional to the CUBE of the velocity, not the square of velocity.

And while we're at it, force = mass X acceleration--or deceleration.

Both arrows will lose the same amount of energy to drag--the heavier one will lose less velocity, but had less to begin with.

If both arrows arrive at the target with the same energy, the energy lost to the target will be equal.

How many of you pontificators actually studied physics?

That's my problem! How much energy will each arrow have at the target? this is fun!

The lighter arrow will have less momentum or force downrange than the heavier arrow. Period

Momentum is penetration. Another period.

I know the original question was that the arrows are going the same fps.  But that can only happen if they are shot off different bows or the same bow drawn to different lengths.  It gets a lot more complicated if you consider the given arrow weights with the appropriate different fps (shot from same bow).  

I shoot 3D with my father who uses a compound.  Light arrows and decent fps at aprox 280.  I shoot slower heavier arrows, but I NEVER get better penetration.  Doesn't matter if the target is at 10 or 50 yards, his penetrates better. I am not sure how to run the math but his fast and light beats my slow and heavy.

NO. The original question stated that the arrows had the same energy--they were going DIFFERENT speeds.

Sir Nell, What is your training in physics?

Here is my take on it. Both arrows you describe are more than adequate. You should shoot the arrow that shoots the straightest and the best way I know how to determine this is to bare shaft and then see what happens when you put on your choice of broadheads. If both arrows shoot equally straight my preference would be the heavier arrow or the one with the highest FOC. Higher FOC just make penetration less of a problem, even with lighter arrows.

Personally, I would select an arrow that flies the best, and groups the best all things being equal (which they are not). Because your arrow speed is 135 fps vs 150 fps, I agree with Mike and probably would go with the later. The majority say weight, but you need to be able to hit what your aiming at regardless of the distance. If 20 yds is your effective range, shoot them then decide.

You did not mention the bow weight, which is important in the discussion, particularly if your shooting a relatively light weight (40-45, 45-50 lbs) with that weight arrow. What arrow material, wood, alu, graphite. What is the FOC? If your shooting a relatively light bow with a heavy arrow, you might consider a lighter arrow with with a higher FOC. Again, reference was made to Dr. Ashby's report. He recommends an FOC as high as possible, 19-30%, and it is easy to confuse a heavy arrow with being the same, when it is not. You may find a lighter arrow with a high FOC that shoots outstanding and penetrates better with a two blade with a 3:1 ratio, eg. Grizzly.

Sir Jim,
Nothing special like yourself.  Just a biology and science major and common sense.  

Now let us all know of your credentials.

If penetration is the concern, the higher FOC with a broadhead with a ferrule the same diameter of the shaft, is better than a small ferrule on a large shaft. Small diameter shaft is going to have less friction than a large diameter shaft, all things being equal. (anyone interested in some 2315 Eastons?)

As for weight to bow draw weight, Fred Bear used a 610-625 gr. arrow with a 65 lb bow for years, which is 9-10 grains/draw wt., and he wasn't too concerned about knocking down.

I am considering going from POC to Ash to get better penetration with the lighter bow I'm shooting now. The example in this thread has the Ash about 26% heavier. I wonder if that is typical.

Hud, so I could maybe keep the POC shafts I have and just increase my FOC. Looks like I could do that keeping my same heads with the new tool at 3R you add a nail footing- anybody have experience with this one?
----------------------
The new internal point weight and footing jig allows you to easily add weight and strength to your wooden arrows and shafts. Simply use the supplied drill bit with your variable speed hand drill to create a precisely aligned internal cavity at the point end of the shaft. Insert a 1/8" rod or nail of your choosing, and then affix the point as normal. Available for 11/32" or 23/64" shaft sizes, 9/64" drill bit included. This jig is specifically designed to accomodate the slight diameter variations typical of wood shafting. However, for best results use the jig size that corresponds to your shafting size. Comes with instructions.
Easy to use
Instructions included
Great weight ot Increase FOC on wood arrows

If a plastic golf ball and a real golf ball were propelled into a glass widow, why would the plastic ball require much more speed than the real golf ball to break the widow?

A year of physics--some time after Newton put forth his formulas.

Common sense, and biological science didn't get anybody off the ground, though they tried.

If the energy of two dimensionally identical arrows is equal at impact, penetration will be equal. The aspects of momentum and inertia are just different representations of energy.

If the bow was held the same for each arrow then the heavier arrow would hit in the dirt in front of the target and ruin this discussion.
Since the bow would have to be tilted higher for the heavier arrow to hit the target then gravity would have more time to affect the heavier arrow as it arcs toward the target.  Since the angle of attack is greater for the heavier arrow it picks up more speed and so hits the target with more force.
I have no physics training but I know if you drop two objects from a skyscraper they hit at the same time.

"Common sense, and biological science didn't get anybody off the ground, though they tried."

Thanks for the confidence booster.  Don't tell my boss...O wait...I am the boss.

"If the energy of two dimensionally identical arrows is equal at impact, penetration will be equal. The aspects of momentum and inertia are just different representations of energy."

They may begin with the same energy but they are not gonna end the same.  That is exactly why the heavier arrow DOES penetrate better.  Downrange it simply is not too fond of stopping as quick as the lighter arrow.  

Is that not what you have found to be true?

QuoteOriginally posted by FlintRiverKen:
I am considering going from POC to Ash to get better penetration with the lighter bow I'm shooting now. The example in this thread has the Ash about 26% heavier. I wonder if that is typical.

Hud, so I could maybe keep the POC shafts I have and just increase my FOC. Looks like I could do that keeping my same heads with the new tool at 3R you add a nail footing- anybody have experience with this one?
----------------------
The new internal point weight and footing jig allows you to easily add weight and strength to your wooden arrows and shafts. Simply use the supplied drill bit with your variable speed hand drill to create a precisely aligned internal cavity at the point end of the shaft. Insert a 1/8" rod or nail of your choosing, and then affix the point as normal. Available for 11/32" or 23/64" shaft sizes, 9/64" drill bit included. This jig is specifically designed to accomodate the slight diameter variations typical of wood shafting. However, for best results use the jig size that corresponds to your shafting size. Comes with instructions.
Easy to use
Instructions included
Great weight ot Increase FOC on wood arrows

that's the braveheart archery footing weight jig - love it!  adds arrow gpp weight, foc forward balance and stiffens a wood shaft's critical area behind the point.

2 thumbs up for the braveheart foot weight jig!

  :thumbsup:    :thumbsup:

Only if the skyscraper is in a vacuum chamber. or are identical in drag

What an excellent topic, while I follow most of it,  I wish I had paid more attention in math and physics classes. I may well try the new footing weight jig mentioned above.


Mike

No Richie, as a matter of fact, if a lighter arrow has the same energy as a heavier arrow, that means the lighter arrow is going faster.

They would lose the same amount of energy in a substance of uniform consistency--and they would stop at the same point.

The difficulty in understanding this is that we never have a controlled situation and enough instances to see a clear picture of the results.

Most of the time, a bow will put more of its available energy into a heavier arrow--which will indeed penetrate farther than a similar, but lighter, arrow from the same bow, because the lighter arrow carries less energy away from the bow. The energy not put into a lighter arrow dissipates as hand shock, string stretch, vibration and so on.

Jim

Jim... What are the tubes in your profile?

Sir Jim,

If a plastic golf ball and a real golf ball were propelled into a glass widow, why would the plastic ball require much more speed than the real golf ball to break the widow?


The original question was..which one has more force (momentum) downrange?  

And you are saying they have the same?  Not possible

Another example is the Little League soft baseballs.  I new a 5-6 year old boy that was hit in the chest with a "soft" baseball and died.  It was soft but not light weight like a plastic whiffle ball.  The texture obviously has nothing to do with making the ball safe.  The weight behind the ball, the force that was exerted on impact even at slow speeds is the killer...unlike the light weight whiffle ball.  It would take an incredible increase in the speed of a whiffle ball to come anywhere close to serious danger.  

The force downrange (or across the diamond) is NOT the same for objects of different weights.

Richie, force=mass X acceleration.

A plastic golf ball has far less mass than a real golf ball. But if the plastic one is going at a speed that gives it the same kinetic energy at impact, it too will break the glass. (Don't try this in the living room.) lol

Yes, the original question was, "which will have the most force when it hits the target?"

Some above have noted that variable of 20 yards of air that must be penetrated before reaching the target.

The heavier arrow would lose less velocity, but at that range, any difference in force at the target would probably be within a margin of error that could be attributed to the uncertainties of measuring the force.

At longer distances, the ratio of the drag area to the mass, and the higher drag on the faster arrow would begin to be obvious.

It all ends up that there is a wide range of values that will do what is needed. Success in our hot pursuit of the ultimate combination would only increase the percentage of kills per shot by a tiny, probably unnoticeable, amount.

Zradix,

Those "tubes" are "Reparrows." They are hard wood footings that glue on the standard taper of a wood arrow to foot, extend or repair it.

Really cool!! Thanks

And now they are gone. Musta stept ona toe.

QuoteOriginally posted by Jim in Maine:
And now they are gone. Musta stept ona toe.

check yer email ....

Some food for thought. Would you want me to throw a ping pong ball at you, or would want a golf ball thrown at you. Which do you think would hurt more thrown at full speed.

physics is physics, and for any specific hunting stick bow i'll prefer as heavy an arrow as i can handle.  

and i'll make sure to push as much of that arrow weight as far forward as possible.

why?  don't need to be a physicist to read and understand the empirical data results found in dr. ashby's reports.  ain't hurting me to use those results to help my hunting.

This has been an interesting discussion.  It's been awhile since I had physics, but I'm trying to follow along here.  Jim, could you explain the difference between force and momentum. They both seem to be a factor of mass and velocity. Also, I think your comment regarding arrows shot from the same bow is most appropos - which is why I like a little heavier arrow in order to gain as much efficiency from any given bow as possible. Obviously someone else can come along and shoot a lighter arrow faster than my heavy arrow and have more energy at the target, but it will be from a different bow.

Sir Jim,
"But if the plastic one is going at a speed that gives it the same kinetic energy at impact, it too will break the glass."

Of course it would..but that is my point.  It will NOT be going at the speed necessary to have equal force at impact.  

It loses speed quicker downrange than the heavy golf ball thus NOT having equal force like you say it will.

"The difficulty in understanding this is that we never have a controlled situation and enough instances to see a clear picture of the results."

A clear picture of which has more force at impact is countless arrows penetrating better due to more force downrange at target impact.  That happens for a reason and that reason is more momentum downrange.

Rob,
Not surprisingly, you are exactly right.  It is not rocket physics.

this is all way over analyzed. just shoot arrows that fly good and with 10 gpp or more and you are good to kill. hunting dangerous or very large game is where a little more info may be necessary.

Overspined,
You are right, no doubt about it. But...it is fun to learn, tweek, read research, try to get it as good as you can sometimes.  It is just fun.

Like you said, at the same time we are having this overkill fun.  We all know that it doesn't take much momentum, force, weight, etc. to actually make a deer dead.

But did I mention overkill is alot of fun?

OK guys, I think maybe some didn't read all of my last comment on drag etc.

First, this entire thread began with the calculations showing that the heavy arrow and the lighter faster arrow had, for practical purposes, the same energy.

You are all correct that that will not be true at some distance from the launching point. The lighter arrow will lose speed faster.

You are also correct in that, if I may paraphrase, the heaviest arrow your bow can give an acceptable trajectory will give the best penetration.

But that is only because the heavier arrow will retain more energy during its flight.

That probably was the intent of the first question. I just jumped in--a little rough shod I guess--when certain laws of physics were being presented incorrectly.

I tend to like the equations and principals a little too much, perhaps.

Greg,

A force is usually defined simply as a push or a pull. In the English system (nearly out of fashion now) the unit of force, foot-pound, is the amount of energy required to move a weight of one pound one foot against the pull of the earth's gravity.

This is also called the amount of work required...

Momentum is the  property of a moving body that it has because of its mass and motion and that is equal to the product of the body's mass and velocity.

An example in my old physics book may be interesting here. It states:

A 4-ton truck traveling east at 10 mph has momentum equal to that of a 2-ton truck traveling east at 20 miles per hour.

So, I think we can see that  a 1,000 grain arrow flying at 100 fps has the same momentum as a 500 grain arrow flying at 200 fps.

Of course, our arrows are not nearly as different as those two and there is drag to contend with.

Anybody who hasn't quit reading?

"They would lose the same amount of energy in a substance of uniform consistency--and they would stop at the same point."

"But that is only because the heavier arrow will retain more energy during its flight."

Your two quotes above seem to be contradictory but the latter is correct.

That is precisely what I have said several times now.....  Which answers his original question of which has the most force at the target.

And I do like reading your information.

just to keep this thread in perspective ...

interesting stuff, no doubt - the physics behind arrow mass/speed/penetration is all well and good.

but to put all of that gobble-dee-gook to the task of trad bowhunting, none of it matters squat at sane hunting distances with a well flying arrow that sports a sharp cut-on-contact broadhead that's put to the SPOT.  

don't care a fig about fps, gpp, foc, lmnop, or etc.   :D

"You are all correct that that will not be true at some distance from the launching point. The lighter arrow will lose speed faster.

You are also correct in that, if I may paraphrase, the heaviest arrow your bow can give an acceptable trajectory will give the best penetration."

That's what I said. Boy, some of you seem to want to make it really hard to agree with you!

Richie,

You quoted me correctly:
"They would lose the same amount of energy in a substance of uniform consistency--and they would stop at the same point."

"But that is only because the heavier arrow will retain more energy during its flight."

But the two quoted passages are from entirely different contexts!!!

I shoot about 11 grains per pound of pull, if anybody cares. 8-)

A long time ago in a place far far away, I was employeed to do some testing with a chronograph at 60 yds.

Yes it was a mechanical bow and at the time I was a pro shooter.

But that being said we did a study for the game dept on retained energy.

We shot arrows from 6 gpp to 12 gpp from a bow through a chrono that was 60 yds down range.

Not an easy task.

Anyway to make it short.  The difference in KE on the light arrow and the heavy arrow from the chrono at 3 ft and the chrono at 60 yds was 3%.

The heavier arrow retained 3% more energy then the light arrow over the distance.  Both arrows were flying perfectly.

Mike

Thanks Mike, you made my day!

QuoteOriginally posted by wingnut:
A long time ago in a place far far away, I was employeed to do some testing with a chronograph at 60 yds.

Yes it was a mechanical bow and at the time I was a pro shooter.

But that being said we did a study for the game dept on retained energy.

We shot arrows from 6 gpp to 12 gpp from a bow through a chrono that was 60 yds down range.

Not an easy task.

Anyway to make it short.  The difference in KE on the light arrow and the heavy arrow from the chrono at 3 ft and the chrono at 60 yds was 3%.

The heavier arrow retained 3% more energy then the light arrow over the distance.  Both arrows were flying perfectly.

Mike

real interesting, mike!

by 'mechanical bow', did you mean hand-held?  release aid?  what was the holding weight and let-off (if any)?

what was the 6pp and 12gpp arrow mass weights?

any foc numbers?

was any data collected at 20yds?

just curious.

I apology if I quoted you out of context.  Gotta keep apples to apples here.

"I shoot about 11 grains per pound of pull, if anybody cares. 8-)"

I shoot around 12-14 (900-1050 grains).  I love the power but mainly for noise reduction.  
10-11 gr./lb would be plenty of arrow weight for my 71 lbs. but louder than I want.

I wonder how the increase in the KE would equate to an increase in Momentum?

That would be interesting to know because Dr Ashby's research show that KE is insignificant as it pertains to penetration.

wingnut... Sounds to me like...YES the heavy arrow in this setup will have more energy at the target.  YES the light arrow will have a flatter trajectory. The difference ,however may actually be very negligible when pertaining to the lethality on a whitetail. I would think that if you're gambling on a 3% chance to kill you're shooting entirely the wrong setup to begin with. It is surprising the trajectory difference in these two arrows when shot at 20yds. The faster arrow will get to the target a little more than .4 sec sooner. I say a little more because I don't know how to figure the extra distance the heavier arrow travels due to more arc. This extra distance would actually bring these two arrows even more similar to each other in energy at target. Mind boggle!!

Just for fun, here is a post that looks at the relationship between momentum and kinetic energy:

http://physics.ucsc.edu/~josh/6A/book/momentum/node3.html


The thing I hope can be gleaned from the above Web page is that kinetic energy and momentum are different ways of describing the same situation.

Wingnut, that would have been a fun study.  3% loss isn't much.  Since you measured KE, I started doing some reading because others have talked about momentum being a more important number to consider.

I just found an interesting example on KE vs momentum.  
Summed up: In this extreme example, a meatball is way more dangerous than a truck at the given variables even though momentum would show they are equal.

Truck's momentum = mv = (1000 kg)(1 m/s) = 1000 kg m/s
Truck's kinetic energy = 0.5 mv2 = (0.5)(1000 kg)(1 m/s)2 = 500 Joules

Meatball's momentum = mv = (1 kg)(1000 m/s) = 1000 kg m/s
Meatball's kinetic energy = 0.5 mv2 = (0.5)(1 kg)(1000 m/s)2 = 500 000 Joules

Here's the source for some more good explanation:
http://www.batesville.k12.in.us/Physics/PhyNet/Mechanics/Energy/KENOTMomentum.html

Below are quotes from Dr. Ashby based on field research.

"ALL MOMENTUM IS NOT THE SAME

Given two arrows, identical in shaft and broadhead materials and profile, and having EQUAL momentum, but possessing UNEQUAL mass, the arrow deriving the greater portion of its momentum from its mass will penetrate better.  The Laws of Physics requires this to be true, and ALL of my field test data validates this to be the case."

"Laws of Physics dictates that momentum, and not kinetic energy, is the correct unit of measure to quantify the linear (straight line) "potential disposable net force" that is available to an arrow.  Momentum determines THE AMOUNT OF FORCE which an arrow has available to it for penetration."

"Kinetic energy is NOT the correct unit of measure for calculating ANY of the forces relevant to penetration.  It is applicable for calculating neither the force of a moving object; the disposable net force at impact; the net force at exit; net force consumed during penetration; the applied impulse; nor the resistance impulse force affecting penetration."

"Laws of Physics dictates that momentum, and not kinetic energy, is the correct unit of measure to quantify the linear (straight line) "potential disposable net force" that is available to an arrow."

I don't think Isaac Newton knew about that one, he never mentioned it.

It is a shame Sir Isaac died not having a clue why all the deer he shot looked like a pin cushion instead of swiss cheese.

Below is from Dr. Ashby's research concerning KE and penetration.

"Using the TPI formula, a 60 pound longbow firing a 788 grain compressed cedar arrow, with a 190 grain Grizzly broadhead, at 148 fps has only 38.34 ft. lbs of K.E., .52 lb.-sec. of momentum, but has a TPI of 1.50.  That combination was used to repeatedly shoot through the scapula of a large zebra stallion and through the thorax to the off side, often breaking off-side ribs (never failing to penetrate the scapula and completely through the thorax).  This was compared to a compound firing a 555 grain aluminum shafted Black Diamond at 229+ fps.  This combination gives 65.21 ft. lbs. of K.E., a momentum of .57 lb.-sec., but a TPI of only 1.27.  That compound was, at best, able to penetrate only 5 to 8 inched beyond the scapula, and occasionally failed to penetrate the scapula at all on that same zebra carcass."

"The 60# longbow/788 grain arrow/Grizzly broadhead was also compared to a high energy compound firing a 450 grain carbon arrow tipped with a three blade head, with cut width of 1 1/8" and a cutting blade length of 2", at a velocity of 259+ fps.  This combination yields 76.56 ft. lbs. of K.E., .52 lb.-sec. of momentum, but a TPI of only 0.62.  It was unable to penetrate the zebra scapula."

"Penetration of this combination (compound, light weight carbon shaft and 3 blade head) on all the larger antelope species is marginal at best.  This bears out the reduced penetration capability of this set-up compared to the lower velocity longbow with its heavy arrow and single blade broadhead of high mechanical advantage.  This even though the momentum of both combinations is identical (.52 lb.-sec.), and the compound has 76% more kinetic energy (67.56 ft. lbs. vs 38.34 ft. lbs.)."

Man I love reading Dr. Ashby's results, thanks Richie Nell.  His reports go way beyond just mathmatical equations and provides a wealth of real testing and experience.  Thanks Dr. Ashby once again.

the doc has spent 25+ years compiling and learning from his exhaustive data collection.

i'll trust his real world bow hunting test results over that dead apple man any day.  

then again, maybe some of you are comparing apples to oranges ... ?  

all my personal testing shows that well flying, heavy, weight forward arrows penetrate 'stuff' better - maybe LOTS better - than lighter, faster, well flying low foc arras.  couple that with a truly sharp c-o-c broadhead and the hunting deed is well setup for killing as long as i do my part.

Well 135fps is getting on down to fish arrows speeds.It might penitrate best but it is below the threshold where I would hunt with so is too heavy for me.Sometimes there are more things to consider when picking arrow weights than what number crunching shows. Common sense needs to kick in sometimes.   ;)     :D

imho, there is no question that higher bow holding weights, and heavier arrows, are always an advantage IF the bowhunter can *effectively* handle the higher bow holding weight under hunting conditions.

imo, hunt with the highest bow holding weight you can *master* - add in a heavy arrow and the prescription for success has been writ, it just needs proper execution.

I love threads like this!

Sorry if it's already been mentioned and I missed it, but don't forget the bow noise aspect.  The heavier arrow will result in a quieter shot.

wow, still arguing this one heh ?

Why not throw in some more data.  Since deer are very prone to doing silly things,  like.. moving, and dead zebra are typically not quite as guilty of that crime, how much does a moving target change the formula (perfect arrow flight is no longer a perfect impact if the target is moving.. in fact with "bad arrow flight" there is a possibility, albeit slim, that the animals movement will correct for the bad arrow flight and allow for even more penetration)

And, as always... if a very light arrow  and a very heavy arrow both go thru the deer and into the ground beyond, which one is better ?
ChuckC

QuoteOriginally posted by ChuckC:
...
And, as always... if a very light arrow  and a very heavy arrow both go thru the deer and into the ground beyond, which one is better ?
ChuckC

however, if both arrows strike an inch or so off and hit bone or gristle mass rather than flesh mass, which arrow has the better chance to kill rather than wound?

Great information Rob and couldnt agree with you more.

Im new to trad archery and all this is some great information for a newbie.

QuoteAnd, as always... if a very light arrow and a very heavy arrow both go thru the deer and into the ground beyond, which one is better ?

The heavy arrow

Jeepers. How long is it until deer season opens again?

I'll take the heavy arrow with high FOC anyday over speed.  Even with my wheelie bow my buddies looked at me like I was crazy when I was getting my arrows built up.  They said "that's gonna be moving so slow it's gonna bounce off the target by the time it gets there."  Well when my arrow blew through the Block target at 40yds and they're lightweight arrows going 300+ fps only penetrated a few inches they were shocked.  Oh and my bow was whisper quiet compared to theirs.

I do no disagree with the premise that a heavier arrow will result in a quieter shooting situation. However, it has almost always been my experience that the fist and foremost factor in good shooting and quieter shooting is perfect tuning of the bow and arrow. Get the brace correct, the nocking point correct, the spine correct, correct and consistent form, a smooth crisp release and you will be surprised at how quiet and how little it may matter in terms of quiet shooting. Far too many bowhunters use the heavy arrow to quiet their bows rather than putting in the extra effort it would take to tune the set up in the first place. It is almost like having to put too much feather on a shaft to get it to shoot properly when the real problem is you need to find a better, more suitable shaft for you setup.

QuoteOriginally posted by Don Stokes:
Jeepers. How long is it until deer season opens again?

:bigsmyl:

QuoteOriginally posted by Bill Carlsen:
I do no disagree with the premise that a heavier arrow will result in a quieter shooting situation. However, it has almost always been my experience that the fist and foremost factor in good shooting and quieter shooting is perfect tuning of the bow and arrow. Get the brace correct, the nocking point correct, the spine correct, correct and consistent form, a smooth crisp release and you will be surprised at how quiet and how little it may matter in terms of quiet shooting. Far too many bowhunters use the heavy arrow to quiet their bows rather than putting in the extra effort it would take to tune the set up in the first place. It is almost like having to put too much feather on a shaft to get it to shoot properly when the real problem is you need to find a better, more suitable shaft for you setup.

Bill,  I agree that a properly tuned bow and arrow combo will be quieter than an untuned.  But if all things are equal and both the lighter and heavier arrow are tuned well then the heavier will absorb more of the bows energy and will in turn be quieter every time.

The difference between shooting a well tuned light arrow and a well tuned heavy arrow is the heavy arrow will kill anything the light arrow will but the light arrow will NOT kill everything the heavy arrow will.

And regardless of how quiet the light arrow bow shoots...the heavy arrow bow is quieter.

Rob...  I seriously don't know (which would likely penetrate that target).  That one wasn't researched...yet.   You can also look at it from another point of view that at our ranges, the faster  (lighter) arrow will get thee quicker and there will have been less movement incurred.

There are a ton of variables in these equations, many of them external to the shooting itself.  

What if a gust of breeze hits just prior to the arrow hitting,  should we have been shooting small feathers,  which are less affected but don't correct arrow flight as quickly,  or should we stick with 5.5" super fletch, which will allow you to shoot nearly any arrow and get past nearly any shooting flaw, but are very affected by breeze.  There goes arrow flight.

There are a dozen more factors to consider beyond that.
ChuckC

Here's one to chew over. It is POSSIBLE (and, actually easy) to have a heavier arrow that shoots as flat, or even flatter than a lighter weight arrow! And that is when both are fired with the same launching force.

I just returned from doing a presentation at the ATA show. I was really pleased with how well the presentation went over with everyone attending – and even many who didn't attend, but who heard about it from those who did attend. The trip was somewhat of an ordeal. On the way up I was only able to drive about 3 hours a day before becoming too exhausted to continue. By the time I headed back I was able to drive seven hours a day, so it looks like the after-effects of the radiation treatments are finally beginning to wear off a bit.

At any rate, I had a little demonstration in the presentation that I'd set up to show folks the effect on arrow flight that EFOC makes. It was a short, rubber tipped arrow with a movable rubber weight. By sliding the weight up or down on the shaft I could shoot the arrow at 6%, 11% and 24% FOC, without the mass of the arrow changing.

I pre-selected and marked the positions for the rubber weight for those specific amounts of FOC. Only a few compound shooters use over 6% FOC, and most use less than 6%. A typical traditional wood shaft with most commonly used broadheads show about 11% FOC. 24% FOC was with the weight as far forward on the shaft as I could slide it.

By using the same launching force and shooting angle on each shot I could demonstrate how much arrow energy is CONSERVED by using EFOC, and also demonstrate that front-weighted EFOC arrow DO NOT nose dive - indeed, they fly both flatter and farther than an arrow OF EQUAL MASS but with a lower amount of FOC. (Just as O.L. has repeatedly proven with his record-setting flight arrows.)

The small shaft was unfletched and, of course, the flight at 6% FOC was TERRIBLE, and it flew about half the length of the lecture hall. At 11% FOC it flew somewhat better, and traveled a bit over 60% of the length of the lecture hall. At 24% FOC the flight was great, and the small arrow HIT THE WALL at the far end of the lecture hall with a resounding thump! You could actually hear the collective gasp of the folks in the audience.

That simple demonstration became the talk of the entire convention - even among folks who hadn't attended, but who heard about it from those who had attended. During the balance of the day of the presentation and the next day I had a number of compound shooters tell me that they had changed to EFOC arrow and, to their amazement, had discovered that the EFOC arrows, though heavier than thier ususal, lower FOC arrows, were shooting flatter at long range. This they each had discovered because they were expecting to have to move thier sight pins DOWN (aim higher) with their new, heavier arrows, but ended up having to moving their sight pins UP (aim lower)!

Based on the information from several of the compound shooters who appeared to have done more extensive investigation of EFOC on their arrows it appears that the 'break even point' was around 150 to 175 grains of increase in total arrow mass. That is; when changing from a low FOC (which was usually around 5%-6%) to EFOC around 24%-25% they each had found that an increase in arrow weight for the EFOC setup of about 150-175 grains resulted in the SAME SIGHT SETTINGS (same point of impact) at 20, 30 and 40 yards as they had been getting with their 'customary arrows'.

This would make an interesting investigation with a shooting machine! After the ATA presentation, there is one thing I know for sure; we're beginning to make real inroads into the bowhunting public (FINALLY!.  :)   )
Ed

QuoteOriginally posted by Dr. Ed Ashby:
Here's one to chew over. It is POSSIBLE (and, actually easy) to have a heavier arrow that shoots as flat, or even flatter than a lighter weight arrow! And that is when both are fired with the same launching force.

I just returned from doing a presentation at the ATA show. I was really pleased with how well the presentation went over with everyone attending – and even many who didn't attend, but who heard about it from those who did attend. The trip was somewhat of an ordeal. On the way up I was only able to drive about 3 hours a day before becoming too exhausted to continue. By the time I headed back I was able to drive seven hours a day, so it looks like the after-effects of the radiation treatments are finally beginning to wear off a bit.

At any rate, I had a little demonstration in the presentation that I'd set up to show folks the effect on arrow flight that EFOC makes. It was a short, rubber tipped arrow with a movable rubber weight. By sliding the weight up or down on the shaft I could shoot the arrow at 6%, 11% and 24% FOC, without the mass of the arrow changing.

I pre-selected and marked the positions for the rubber weight for those specific amounts of FOC. Only a few compound shooters use over 6% FOC, and most use less than 6%. A typical traditional wood shaft with most commonly used broadheads show about 11% FOC. 24% FOC was with the weight as far forward on the shaft as I could slide it.

By using the same launching force and shooting angle on each shot I could demonstrate how much arrow energy is CONSERVED by using EFOC, and also demonstrate that front-weighted EFOC arrow DO NOT nose dive - indeed, they fly both flatter and farther than an arrow OF EQUAL MASS but with a lower amount of FOC. (Just as O.L. has repeatedly proven with his record-setting flight arrows.)

The small shaft was unfletched and, of course, the flight at 6% FOC was TERRIBLE, and it flew about half the length of the lecture hall. At 11% FOC it flew somewhat better, and traveled a bit over 60% of the length of the lecture hall. At 24% FOC the flight was great, and the small arrow HIT THE WALL at the far end of the lecture hall with a resounding thump! You could actually hear the collective gasp of the folks in the audience.

That simple demonstration became the talk of the entire convention - even among folks who hadn't attended, but who heard about it from those who had attended. During the balance of the day of the presentation and the next day I had a number of compound shooters tell me that they had changed to EFOC arrow and, to their amazement, had discovered that the EFOC arrows, though heavier than thier ususal, lower FOC arrows, were shooting flatter at long range. This they each had discovered because they were expecting to have to move thier sight pins DOWN (aim higher) with their new, heavier arrows, but ended up having to moving their sight pins UP (aim lower)!

Based on the information from several of the compound shooters who appeared to have done more extensive investigation of EFOC on their arrows it appears that the 'break even point' was around 150 to 175 grains of increase in total arrow mass. That is; when changing from a low FOC (which was usually around 5%-6%) to EFOC around 24%-25% they each had found that an increase in arrow weight for the EFOC setup of about 150-175 grains resulted in the SAME SIGHT SETTINGS (same point of impact) at 20, 30 and 40 yards as they had been getting with their 'customary arrows'.

This would make an interesting investigation with a shooting machine! After the ATA presentation, there is one thing I know for sure; we're beginning to make real inroads into the bowhunting public (FINALLY!.   :)    )
Ed

:thumbsup:  Finally is right Doc!  Great Job!!!   :clapper:    :clapper:    :clapper:    :clapper:

Dr. Ashby,
That is what I asked you about awhile back when I thought I may be hallucinating.  
That is definitely what I see in the flight of my 1000 grainers with 31% Ultra-EFOC.  They fly like a 750 grainer but quieter and with a bit more clout.

Thanks again for your work.

Richie,

It all just stands to reason. The outcome with this simple demonstration arrow setup logically implies that the energy previously wasted by an arrow with low FOC (and now being conserved by an arrow of higher FOC) can be usefully applied to propell a heavier, higher FOC arrow with a trojectory that is equally as flat as that of the lighter, lower FOC arrow.

Also, it must be remembered that the heavier arrow will retain its velocity better than a lighter arrow, continually gaining ground - velocity wise - against a lighter arrow as the range increases AND, the higher FOC arrow also stabalizes with less fletching, which translates to less drag during flight, which also aids velocity retentuion.

Life is good!   :coffee:    :goldtooth:

Any arrow with poor flight will not shoot as far as one with good flight. 6% arrows can fly extremely well. Changing nothing but the foc has to alter the dynamic spine therefore changing flight characteristics.

To give credit where credit is due, the FOC demonstration above is a simple example of the results of very extensive testing By C.N. Hickman done with a shooting machine and reported in Archery Review of February 1934.

Those who will not study history feel compelled to discover everything all over again...

If I am understanding this correctly, a well tuned 6% will not fly well AS FAR as a well tuned 26% arrow.  This is because of the location of the weight.  The weight is pulling and not pushing the arrow.

Not exact but maybe similiar;
A rear wheel drive vehicle inefficiently pushes the front of the vehicle around and eventually into a ditch on a muddy dirt road.  

The front wheel drive vehicle steers itself more efficiently and is going to stay in the road better than the rear wheel drive.

Jim,
You are amazing.

QuoteOriginally posted by SteveB:
6% arrows can fly extremely well.  

Absolutely. 3D shooters don't seem to have a problem hitting X rings at 50 and 60 yards with low FOC arrows. If someone feels that they need to go to extremes with respect to FOC for accuracy at bowhunting distances, I'd venture to say that their accuracy problem has nothing to do with the balance point of their arrows.   ;)

Sorry

Yes, 6% FOC arrows can fly extremely well ... IF they have sufficient drag from the fletching to overcome the inherant instability of a flying object having a FOC of only 6%. Therein lies the difference. There is a huge energy loss in compensating for the inate instability of a low FOC projectile in flight. It's the same for aircraft. Why do gliders have their wings (and the cockpit and pilot) positioned as far forward as possible? For greater flight stability and maximum use of any available propulsion. Why does the Raptor have a neutral FOC? Greater maneuverability, albet at instability in flight so great that a human cannot fly it without computer assist.

Ed

Changing the dynamic spine to cause erratic flight makes it less then an apples to apples comparison. By only using one arrow, 2 changes are being done - foc and dynamic spine. It would seem that to be relative, 2 arrows of the same wght and same dynamic spine, with the only the foc being different should be used.

QuoteOriginally posted by Zradix:
Thanks for all the help guys. Yeah I have to admit I'm a little worried about overkill. Don't need to use an elephant gun on a mouse. I'm wondering if the 10gn/# will pass thru just like the 13 on whitetails.

Without reading all the responses in this thread,9gpp out of my 50# bear grizzly will not only pass thru a whitetail,it will zip through.You should have no issues with either of those from your bow.

QuoteOriginally posted by Dr. Ed Ashby:
Yes, 6% FOC arrows can fly extremely well ... IF they have sufficient drag from the fletching to overcome the inherant instability of a flying object having a FOC of only 6%.

Just for the sake of discussion; the 3D shooters I was referring to (compounds, obviously) shoot vanes 2" or less in length -- not a lot of drag. Even FITA shooters who use the standard recommended 11-16 percent FOC use tiny vanes.  

If you don't mind, could you please explain how the tuning issues Steve describes did or did not come into play in your demonstration? It seems like the results were more about a tuned versus untuned bare shaft than they were about FOC alone.

Jason,

In the simple demonstration arrrow used the dynamic spine on ALL the shots would be grossly over-spined. The propulsion system was a short section of modest strength bunge cord, drawn less than 10 inches. The shaft was a 20" section of dowel rod. The mass weight of the sliding weight is small. None of the shots represented a 'tuned vs. untunes' setup. All were 'untuned'. It was a demonstration of the effect EFOC has on the flight characteristics of even a poorly tuned arrow setup.

I have, however, used matching arrows (same total mass and external profile, varying only in degree of FOC), equally well tuned, from the same bow and achieved the same results - the higher FOC shoots measurably (and significantly) flatter than the lower FOC arrow. To do so the higher FOC arrow has to be making better use of the force derived from the bow. This has been a 100% occurrance when testing with such matching setups.

Conversely, I have yet to see an equally well tuned lower FOC arrow that can totally recover from paradox as quickly (with the smaller fletching) as an arrow of higher FOC. That means that more of the arrow's force is being loss to arrow flex. These results are not based on conjecture, but on repeated actual testing, from several different types of bows.

With big traditional broadheads (like the 190 Grizzly), Wesley Mulkey is getting total stability and can consistently hit 1" dots at forty yards using a 2" A&A pattern 3-fletch on a 28% FOC arrow setup. At lower FOC he can't do that, even with considerabley more fletching and regardless of the tuning. That's from actual testing too. Why does it happen? Because of the inate stability of a higher FOC projectile in flight. (Wesley is a three time Georgia 3-D champion, and by far the most accurate shooter I personally know.)

Talking with the folks at Win Win, most all of the South Korean FITA shooters are using well upwards of 19% FOC ... and they're the ones 'taking the gold'.

Just as I told everyone at the seminar, there's no trick or no magic. When we're finished, feel free to come up and try it for yourself.

Hope that helps clarify,
Ed

Thanks Ed

ChuckC

Ed,

I appreciate your response. By your earlier post, I was under the misimpression that your demonstration involved an arrow being shot from a bow. With that being the case, before we conclude that...

"It is POSSIBLE (and, actually easy) to have a heavier arrow that shoots as flat, or even flatter than a lighter weight arrow! And that is when both are fired with the same launching force."

...would it be possible to conduct a controlled experiment that actually utilized the elements of that conclusion—"heavier arrow", "lighter weight arrow", "fired"? I would be very interested to see the results of such an experiment, as it would provide true apples to apples results.

Either way, thank you again.

An archer from the Ukraine, took the mens Gold in archery in the 2008 Olympic games.  I don't know what kind of FOC he was using.

now this discussion is getting real interesting.  way cool.

early this morning i pulled out four longbows ...

53# @ 29" moab aggressive r/d
55# @ 29" mohawk t/d mild r/d
45# @ 29" mohawk mild r/d
47# @ 29" sunbear mild r/d

and shot this one arrow out of each bow ...

29.5" ad trad (nock tapered carbon),  i had no other initial measured data on this arrow other than it felt point heavy and had substantial mass weight.  (arrow data collected after shooting and listed below).

from 8 to 21 yards this arrow flew like a dart.  i needed no fletching at all.  i felt confident launching this arrow from each bow and rarely missed hitting the 12" x 10" target.  the moab was the fastest bow, a real rocket launcher!  the 55# 'hawk t/d had much better stability and 'pointability' than the moab, but was slower.  the 45# mohawk felt the most stable of all the bows, and by far it had the best 'pointability'.  the 47# sunbear had great stability and pointability but was by far the slowest.

i noted the arrow data after shooting ...

* shaft + alum insert + 5/16" glued on nock = 356 grains
* 273 grain point (11/32" judo epoxied to a 125gr steel adapter)
* 666 grain total bare arrow weight
* 25.12% efoc
* gpp range is 12.11 to 14.80

i swapped out the heavy judo/adapter for a 127 grain screw-in judo point ...

* 481 grain total bare arrow weight
* 14.10% foc
* gpp range 8.75 to 10.69

as expected, arrow speed was dramatically increased with all 4 bows.  arrow flight was definitely not as clean as the heavier version.  i had to be very careful and methodical with my form and release or arrow flight would be close to horrible and thus the point of impact was not at all consistent.  i missed the target too often.  in this configuration, this arrow absolutely requires fletching!

my target was a doubled folded heavy rug supported on graphite tubes staked into the ground, so no penetration data (which would be harder still since testing was done with judo points), but the 666 grain arrow mad a noticeably harder smack into the rug, typically blasting through it with every hit - not so with the lighter arrow, which failed to hit the rug too many times.    :help:  

welp, my unscientific quickie testing sez to me i'll take that big ol' heavy arrow, with efoc, any day,    :cool:

QuoteOriginally posted by George D. Stout:
An archer from the Ukraine, took the mens Gold in archery in the 2008 Olympic games.  I don't know what kind of FOC he was using.

george, you back from vacation already?    :saywhat:

I never thought I'd glean this much information from posting my question. Thank you everyone...Course I'll be more than happy to listen to more!!!

QuoteOriginally posted by Rob DiStefano:
now this discussion is getting real interesting.  way cool.

early this morning i pulled out four longbows ...

53# @ 29" moab aggressive r/d
55# @ 29" mohawk t/d mild r/d
45# @ 29" mohawk mild r/d
47# @ 29" sunbear mild r/d

and shot this one arrow out of each bow ...

29.5" ad trad (nock tapered carbon),  i had no other initial measured data on this arrow other than it felt point heavy and had substantial mass weight.  (arrow data collected after shooting and listed below).

from 8 to 21 yards this arrow flew like a dart.  i needed no fletching at all.  i felt confident launching this arrow from each bow and rarely missed hitting the 12" x 10" target.  the moab was the fastest bow, a real rocket launcher!  the 55# 'hawk t/d had much better stability and 'pointability' than the moab, but was slower.  the 45# mohawk felt the most stable of all the bows, and by far it had the best 'pointability'.  the 47# sunbear had great stability and pointability but was by far the slowest.

i noted the arrow data after shooting ...

* shaft + alum insert + 5/16" glued on nock = 356 grains
* 273 grain point (11/32" judo epoxied to a 125gr steel adapter)
* 666 grain total bare arrow weight
* 25.12% efoc
* gpp range is 12.11 to 14.80

i swapped out the heavy judo/adapter for a 127 grain screw-in judo point ...

* 481 grain total bare arrow weight
* 14.10% foc
* gpp range 8.75 to 10.69

as expected, arrow speed was dramatically increased with all 4 bows.  arrow flight was definitely not as clean as the heavier version.  i had to be very careful and methodical with my form and release or arrow flight would be close to horrible and thus the point of impact was not at all consistent.  i missed the target too often.  in this configuration, this arrow absolutely requires fletching!

my target was a doubled folded heavy rug supported on graphite tubes staked into the ground, so no penetration data (which would be harder still since testing was done with judo points), but the 666 grain arrow mad a noticeably harder smack into the rug, typically blasting through it with every hit - not so with the lighter arrow, which failed to hit the rug too many times.     :help:    

welp, my unscientific quickie testing sez to me i'll take that big ol' heavy arrow, with efoc, any day,     :cool:  

Rob, I did pretty much the same thing with 2 of my bows today even though I'd already done it with trad and wheelie bows before, and I got the same results.  I also did as Doc explained with a very overspined and untuned shaft with 425gr. up front and watched it correct itself inflight as though it had fletching on it and still hit the target.  Yep, I know what'll be in my quiver  :D

As per Sir Jim,

"And now they are gone. Musta stept ona toe."

It seems the force of gravity has been defeated. Sir Isaac Newton would be amazed.

Someone has to make sure "all" of the information is correct 8^)))))))).

QuoteOriginally posted by Rob DiStefano:

arrow flight was definitely not as clean as the heavier version.  i had to be very careful and methodical with my form and release or arrow flight would be close to horrible and thus the point of impact was not at all consistent.  i missed the target too often.  in this configuration, this arrow absolutely requires fletching!

Of course your arrow flight was not as clean with the lighter arrow. You took a tuned arrow, reduced its point weight by 185 grains (thereby throwing it out of tune), and re-shot it out of the same bows. If I swapped my 125-grain heads for 310-grain ones my arrows would be touchy and fly like garbage too.

 

QuoteOriginally posted by Rob DiStefano:
welp, my unscientific quickie testing sez to me i'll take that big ol' heavy arrow, with efoc, any day,       :cool:    

Yeah, I'd take a tuned arrow instead of an untuned one too.     ;)

hmmm there are 11 dimensions in the new string theory (P theory).  thus gravity's force is diluted because it crosses all 11 dimension.  I must live in the wrong dimension.  

i don't have a bow that will shoot any 600 gr arrow as fast as it will shoot a 450gr.  I would bet the house that at 30yds the 450 gr is still faster. with fletch or without fletch. EFOC or not.

so i would guess we are not talking about speed here......

rusty

Don,

Nope, the law of gravity is being well enforced. As you'll remember from grade school science, the pull of gravity is a constant, not dependent on the weight (mass) of the object. The Gravitational Constant is 32.174 feet/second/second at sea level. A falling body drops at this rate, regardless of its mass.

(1) A higher mass arrow absorbs more of a bow's stored energy, and will carry higher kinetic energy than a lighter arrow from the same bow.

(2) If more of the arrow's energy is applied to the arrow's forward motion then the arrow will travel farther before it drops to the ground. A more efficient arrow design does exactly that; it conserves energy otherwise wasted on 'non-productive work", such as recovering from paradox and/or stabilizing arrow flight.

(3) A heavier arrow which derives greater energy from the bow and which also is of a design that makes more efficient use of whatever energy it derived from the bow can have an equal or shorter travel time across a given distance; ergo, gravity has an equal or lesser time to act upon the arrow and the drop at that distance will be equal or less.

As previously noted, several compound shooters who approached me at the ATA reported that they were getting equal or less drop at 20, 30 and 40 yards with a heavier arrow having EFOC than with a lighter arrow at low FOC (and in one case the shooter reported that he had tested to 60 yards, with the same results). The aggregate of reported results indicated that an EFOC arrow in the 24%-25% range shot to the same point of impact as a low FOC (in the 5% to 6% range) that was 150 to 175 grains lighter. This is congruous with the results I've had with equally tuned, equal mass/profile arrows; the equal mass, higher EFOC arrows shoot flatter (drop less) than the lower FOC arrows. This can only occur when the flight time is less. Since I was testing with equal mass arrows, equally well tuned, the bow derived force would be equal. For the flight time to be less the EFOC arrow has to be using its bow-derived arrow force more productively than the lower FOC arrow. This additional 'productive arrow force' can equally well be applied to pushing a somewhat heavier arrow fast enough to result in a 'total flight time' equal to that of the lighter arrow, resulting in equal arrow drop.

Now those compound shooters are generally working with more 'potential bow force' than most of us traditional shooters. That means a higher potential 'useful force' gain (from the same amount of increase in arrow efficiency), but the effect would be the same for a traditional bow, but to a somewhat lesser degree - dependant only on the amount of available force (at equal arrow efficiency).  

It's all about total flight time. Ask any competition 1000 yard rifleman which .30 caliber bullet shoots flatter (has less drop) at 1000 yards, the 200 grain Match King or the 180 grain Match King, when fired from any of the .300 Magnum cartridges commonly used in 1000 yard competition. It's the 200 grain bullet, even though it starts out well over 200 fps slower than the 180 grain version. Why? Because it makes more efficient use of the energy it carries. Indeed, beyond 600 yards it will be traveling faster than the 180 grain bullet. The net result is a shorter total travel time to reach the 1000 yard target, giving a sorter time for gravity to pull on the bullet, which results in a lesser amount of bullet drop. Bullets are a far more efficient aerodynamic design than an arrow, which also means that the potential for gains in efficiency are far greater for the arrow, percentage wise.

Hope this helps clear up the gravity question,
Ed

I do under stand long range rifle shooting.  I even understand 90 meter archery.  Not interest really in either on of those. the most important thing to me is the flatest trajectory I can get from 15 to 25 yds.  which arrow will give the flatest, least drop from 15 to 25 yrs and with that flatest trejectory give me the best
penetration

An example of my interest is a 13 to 25 pound feathered bird with a kill zone a little smaller than my 18 yd group shown,  what arrow can i shot thatwill give me a hit in the killzone as I move up five steps or back five steps.  tune very well and be very quite.  If i had my foundest wish the arrow afer beening shot would have about seven inches hangin out one side of him and another 7 inches out the other side. the close side right thru the wing knuckle destoring it then taking ahard angle down into the boiler room or a littel angle up and cut the sprind.

On top of that I want it to shoot out of a 46#@28" so that I am strong enough to hold the bow at half draw while the trukey decides to get lined up on my shot line and i don't have to start the draw from full draw.

not only do I think arrow speed is very important on turkey hunting, i have one turkey Tom pick the arrow up visually and duck the arrow. then duck and other arrow becuase the first arrow didn't even land close enough to make him worred.  the use of a string track line paying all the way out to him looks like the jet exhaust on the old Vet 104 Thundercheif fighter jet.  you knew it was coming from a way off.  kinda early warning.  

I know from postmortums that I have had many near misses,  the hit sstill resulted in a recovered turkey but is was close.

I use the same rig for pig hunting at night.  bow is 46# on my fingers and I using a 1916 28.5" and the 4 blade stingers.  I only get about 5 yd of tractory that will hold the wing knuckle with the 1916.  the shaft and 4 blade stinger will tear the knuckle to it in not flight worth.

Dryad 17" riser  with lognbow and recurve limbs.  62"  lighted sight for night time, single pin for turkey,  I do quiet often was a Bieter 1/2" frame without an inster.  top othe diamond to bottom of the diamond is over 12 yds,  works good

     (http://i706.photobucket.com/albums/ww66/rustycraine/oriongrp1a.jpg)

rusty

QuoteOriginally posted by Jason R. Wesbrock:
 

QuoteOriginally posted by Rob DiStefano:

arrow flight was definitely not as clean as the heavier version.  i had to be very careful and methodical with my form and release or arrow flight would be close to horrible and thus the point of impact was not at all consistent.  i missed the target too often.  in this configuration, this arrow absolutely requires fletching!

Of course your arrow flight was not as clean with the lighter arrow. You took a tuned arrow, reduced its point weight by 185 grains (thereby throwing it out of tune), and re-shot it out of the same bows. If I swapped my 125-grain heads for 310-grain ones my arrows would be touchy and fly like garbage too.

   

QuoteOriginally posted by Rob DiStefano:
welp, my unscientific quickie testing sez to me i'll take that big ol' heavy arrow, with efoc, any day,        :cool:      

Yeah, I'd take a tuned arrow instead of an untuned one too.      ;)  [/b]

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

never tuned any arrows to any bow - that was my point.  in fact, i never shoot ad trads these dayze, only beman ics 500's.  this was the first time i ever shot an ad trad outta those 4 bows.  i used that one arrow with different bows from 45 to 55 pounds holding weight and the arrow flew dead straight  on from each bow.  make of that what you will.  all that matters is my opinion of that little experiment,

now, i never mentioned trajectory!  hah!  there was a bunch with the light weight bows and 666 grain arrow at over 20 yards.  NOT at all for me!    :D    :saywhat:  

QuoteOriginally posted by Rob DiStefano:

never tuned any arrows to any bow - that was my point.

Your point was that you never checked how tuned or out of tuned those two configurations were, but yet you concluded that heavy, EFOC arrows fly better than normal arrows? I think what you actually demonstrated was that the static spine of those shafts requires 273 grains up front to fly correctly out of your bows.   :rolleyes:

8^).

Dr. Ashby posted: "Nope, the law of gravity is being well enforced. As you'll remember from grade school science, the pull of gravity is a constant, not dependent on the weight (mass) of the object. The Gravitational Constant is 32.174 feet/second/second at sea level. A falling body drops at this rate, regardless of its mass."

Grade school science also told us that was, "in a vacuum!"  

But nature abhors a vacuum!  8^).

QuoteOriginally posted by Jason R. Wesbrock:
 

QuoteOriginally posted by Rob DiStefano:

never tuned any arrows to any bow - that was my point.

Your point was that you never checked how tuned or out of tuned those two configurations were, but yet you concluded that heavy, EFOC arrows fly better than normal arrows? I think what you actually demonstrated was that the static spine of those shafts requires 273 grains up front to fly correctly out of your bows.    :rolleyes:  [/b]

i never said any of that, jason.  

i just think it's interesting that one arrow, configured a certain way, bareshafted well out of 4 different bows with 4 different holding weights.  that's all i said.

i'm not saying anything else ... good, bad or indifferent.  just stating what i found,  what you think is your bidness and that's just fine with me, too.

for the record, for you, george, jim, whomever ...

anything i say about heavy gpp or efoc or lmnop is not me espousing any arrow gospel.  just stuff i've found and stuff that's perhaps worthy of some consideration by everyone.  if you don't wanna consider such goings on, that's way cool.  

believe it or not, i'm old school when it comes to archery.  i know what works for me very well.  i have no idea what works for you, but i very much respect your way of shooting and of your tackle choices.  got that?     :saywhat:      

i know what kills game first and foremost, too - a well placed scary sharp broadhead that's delivered by a well flying arrow.  nothing at all to do with gpp, foc, efoc, etc.  

that's about it.  is that clear to you guys?    :campfire:

QuoteOriginally posted by Rob DiStefano:
 

QuoteOriginally posted by Jason R. Wesbrock:
 

QuoteOriginally posted by Rob DiStefano:

never tuned any arrows to any bow - that was my point.

Your point was that you never checked how tuned or out of tuned those two configurations were, but yet you concluded that heavy, EFOC arrows fly better than normal arrows? I think what you actually demonstrated was that the static spine of those shafts requires 273 grains up front to fly correctly out of your bows.     :rolleyes:   [/b]

i never said any of that, jason.  

[/b]

What you said was...

QuoteOriginally posted by Rob DiStefano:

welp, my unscientific quickie testing sez to me i'll take that big ol' heavy arrow, with efoc, any day,  

Now, if that isn't what you concluded by your test, then I'm truly at a loss because that's what you wrote. I don't honestly know how many ways that sentence can be interpreted.

QuoteOriginally posted by Rob DiStefano:
i have no idea what works for you, but i very much respect your way of shooting and of your tackle choices.

As I respect yours. Neither of us bought our first bows yesterday. I've been around long enough, shot enough different tackle different ways and killed enough piles of critters to know that there are a lot of different ways to get the job done, and there are very, very few universal rights or wrongs in this subject. So please don't misinterpret our discussion here as an "I'm right; you're wrong" exchange. It isn't, at least from my end.

jason,

all i stated was what i feel is gonna work best for me.  if you read something else in that, sorry.

enjoy whatever works best for you!    :wavey:

The good thing is the more a bowhunter knows about the maximum and minimums, the better a bowhunter can tune a bow and arrow to fit the situtation he hunts in.  

I don't want to go to an extreme either way.  the lightest arrow would give me the best hunting range trajectory (IMO) but might not be the best selection at the terminal end.  

it is fun taking all the information and testing it against what the bowhunter has (or thinks he has) figured out over the years.  I love to tinker with my toys  :) .  

good thread.  lots of good tinkering bits  :)

rusty

QuoteOriginally posted by George D. Stout:
...But nature abhors a vacuum!  8^).

If I may offer a more modern version:

"But Nature and Man abhor vacuum cleaners"

George,

A clarification. There is a difference between the force of pull exerted by the Gravitational Constant and the acceleration of a falling body that results from the pull of the gravitational constant.

The force of the Gc is a universal constant. The Gravitational Constant, denoted Gc, is an empirical physical constant involved in the calculation of the gravitational attraction between objects with mass. It appears in Newton's law of universal gravitation and in Einstein's theory of general relativity. It is also known as the universal gravitational constant. The rate of acceleration of a falling body resulting from the pull exerted by the Gc changes, depending on the medium the object is falling through. Ergo, as a 'body' is falling through air the resistance gradually increases, progressively reducing the rate of acceleration until "limiting velocity" is reached. In a true vacuum the rate of acceleration would not decrease. However the Gc would remain constant in each case.

The rate of acceleration resulting from the pull of the Gc at sea level is 32.174 feet per second/second ... until the limiting velocity is reached, where the force of resistance equals the Gc acting upon the body. To be absolutely precise, I should have said that the Gravitational Constant is 32.174 lbm-ft/lbf-sec2, which results in the acceleration rate of a falling body of 32.174 feet per second/second at sea level.

So, just for clarification:

"It is easy to verify that, when air resistence is negligable, all objects accelerate towards the earth at the same rate. The 'reason' is that the gravitational force on an object is proportional to its inertial mass. According to Newton's second law, in order to calculate the acceleration of an object caused by gravity, we must take the gravitational force on that object and divide by the inertial mass. Thus, the inertial mass of the object cancels out of the resulting expression for the acceleration. In fact the acceleration of any object at the Earth's surface is determined by the distance of the object form the center of the Earth, Newton's constant (Gc) and the mass of the Earth:

Acceleration = Gc multiplied the Mass of the Earth divided by the Radius of the earth squared

If you put the value of Newton's constant, the radius of the Earth ( 6 x 106 meters) and the mass of the Earth ( 6 x 1024kg) into the above expression you will get approximately 9.8m/s2, which is the rate at which all objects accelerate downwards at the surface of the Earth (at the level of the earth's surface).

Although the magnitude of the acceleration due to gravity, g, is the same everywhere on the Earth's surface, its direction changes depending on where you are. It is a vector that always points towards the center of the Earth, so, for example, it is in the opposite direction at the North Pole than at the South Pole. This effect is not very relevant to us because the Earth is so big. If we move from one end of the room to another, or even one end of the city to another, we are only moving across a very small fraction of the total circumference of the Earth, so the direction of the gravitational acceleration changes very little. Our notion of ``down'' only changes significantly when we travel very large distances. However, if you happen to be near a very massive, but small object, such as a black hole, the fact that gravitational acceleration changes direction depending on your location becomes very significant indeed: it gives rise to so-called tidal gravitational forces that can tear a spaceship apart in microseconds.

Note that the rate at which objects accelerates towards the Earth changes with distance. We don't notice this because we are already so far from the center of the Earth (6 thousand kilometers) that we would have to move vertically a large distance to cause a significant change: for example, to decrease the acceleration due to gravity by half down to 4.9 m/s2 we would have to go out into space about 1500 km above the Earth's surface."

Gc is a constant. The rate of acceleration resulting from the Gc changes with a number of factors. Nonetheless, the Gc always remains constant. Hope that clears everything up.

I was trying to keep the explination(s) as simple as I could - as some folks think I tend to make explinations too complex - but any time I'm less than absolutely precise there's always someone looking to point it out. That's good. Keeps us all on our toes!    :biglaugh:  

Ed

Dr. Ashby: "I was trying to keep the explination(s) as simple as I could - as some folks think I tend to make explinations too complex.."

Don't sell yourself short Doc, "most" folks think you tend to make explanations too complex."
 :knothead:    :thumbsup:

quote:

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Originally posted by George D. Stout:
...
What tends to tick us (me) off is the trend of "some" to think a study of this nature cancels and supercedes everything else we have learned over the decades.  ...   :saywhat:  

but nah, that's not you, george.  :D      :biglaugh: