arrow physics 2

[Dr. Ed Ashby]

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

[ChuckC]

Thanks Ed

ChuckC

[Jason R. Wesbrock]

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.

[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.

[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.      

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

[Rob DiStefano]

Originally 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?    

[Zradix]

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!!!

[Kenneth]

Originally 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.        

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

[Richie Nell]

As per Sir Jim,

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

[Don Stokes]

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

[George D. Stout]

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

[Jason R. Wesbrock]

Originally 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.

   

Originally 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.    

[trashwood]

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

[Dr. Ed Ashby]

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

[trashwood]

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

     

rusty

[Rob DiStefano]

Originally posted by Jason R. Wesbrock:
 

Originally 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.

   

Originally 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      

[Jason R. Wesbrock]

Originally 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:

[George D. Stout]

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^).

[Rob DiStefano]

Originally posted by Jason R. Wesbrock:
 

Originally 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?          

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?    

[Jason R. Wesbrock]

Originally posted by Rob DiStefano:
 

Originally posted by Jason R. Wesbrock:
 

Originally 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…

 

Originally 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.

 

Originally 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.