Setup A 400 grain arrow 151 fps
Setup B 300 grain arrow 185 fps
Speed verified with chronometer. Setup A has 33% more arrow weight and ~10% more momentum. Setup B has ~15% more KE. Which do you think will provide more penetration into hard medium like bone? Will be testing them on 3/4" plywood.
OK, I'll guess, ummm A the heavy slow arrow. And that's just cuz I like heavy slow arrows. I like momentum over speed
Gotta see this.
I'm no Sir Issac Newton, but my gut reaction is to say that "B" wins at close range (under 20 yds) and "A" wins at the longer distances.
I cheated. Gold tip Kinetic energy calculator gives the nod to B. But I think Lon has a good point. Looking forward to your test results. Scott
I'll guess that inside 15-18 yards B, outside 15-18 yards A?
Oops, didn't see Blackhawk's post. X2 on Blackhawk's prediction
Depends on the yardage and foc
Neither. Both setups are generating little kinetic energy and momentum. I would not want to use either setup for big game animals.
Native, hurry up and shoot something so i know if I won .
PS, i agree with John v , not a whole lot going on with those arrows but since you're hunting plywood who cares
The heavier arrow has about 9% more momentum so theoretically it should penetrate better,if the heads are identical and shafts the same diameter.
Having said that,those are very light setups and I believe neither will penetrate much in 3/4" plywood.I believe any difference,if it can be measured,would be a fraction of an inch.
In this case,I would try a different medium for testing.I prefer minicell foam but insulating foam board should also work.
Why not 1" ( 3/4") boards, maybe 1 x 6" which might more closely simulate a bone by cracking open.
Frankly, arrows have been tested in plywood, paper, heck, probably stacked pizzas. The only place it really matters is in chest cavity.
Almost any reasonable arrow flying straight when the hit takes place, and leading with a sharp broadhead suitable for the arrow, will penetrate a deer's chest enough to kill it.
Even a 300 grain arrow, which is about half of what I use for deer. Use what you want. Its been done before.
Once again, it appears that we are looking for the least amount of everything needed, instead of the most.
ChuckC
It's going to be the heavy arrow at all distances. Very close shots could be a toss up depending on the quality of the arrow flight.
I think FOC could be a factor, but neither arrow is heavy enough to be a major factor.
Top arrow 300 grains bottom arrow 400 grains.
(https://farm1.staticflickr.com/565/20508599462_39f1bfc0c5_b.jpg)
(https://farm1.staticflickr.com/567/20329403798_ccbe93fd22_b.jpg)
Tested 3 sets. Results are quite consistent everytime. The 300 grains arrow always penetrate about 1/4" more. There are 2 layers of plywood. 1/2" in front and slightly thinner one behind. The lighter arrow will always just punch through the second layer. (Point just visible from the back.) While the heavier one makes a small dimple on the second layer. The picture above shows the penetration on the first 1/2" layer. (Second layer removed)
Tests done at 10 yards. By now I think some of you would have guessed the arrows are shot out of 2 different bows. (It's physically impossible to shoot a lighter arrow with higher KE out of the same bow) I repeated the test by shooting the 2 arrows from the same bow and both arrows penetrate exactly the same every time.
QuoteOriginally posted by JohnV:
Neither. Both setups are generating little kinetic energy and momentum. I would not want to use either setup for big game animals.
This...
Even though the arrows are the same diameter, with a 100 grain difference, one is flying better out of your bow than the other. I'd guess the 300 grain arrow is. Of course, the same weight head gives the lighter arrow more FOC, which also works to increase penetration.
In short, difficult to know what factor(s) account for the greater penetration, but weight is only one of them. :readit: :goldtooth:
The 400 grain arrow has perfect flight. 300 grain arrow is weak as it showed nock left when sticking in the board. I will continue to test with a broadhead if I can get my hands on some better medium. Maybe some thick ribcage from the market. But for now it seems KE is needed for penetration at short hunting distances.
I will predict that you will see more penetration from the heavier arrow when you switch to broadheads, but will be interested in seeing what you come up with.
Check on the dangerous game forum, and/or with people and PH's who hunt and guide for animals like Asiatic water buffalo, Cape buffalo, etc.
Nothing like experience shooting the real deal.
Good testing! Those are pretty low energy setups though
QuoteOriginally posted by Nativestranger:
Tests done at 10 yards. By now I think some of you would have guessed the arrows are shot out of 2 different bows. (It's physically impossible to shoot a lighter arrow with higher KE out of the same bow) I repeated the test by shooting the 2 arrows from the same bow and both arrows penetrate exactly the same every time.
Are you positive? The formula for KE squares the velocity measurement so a lighter arrow (faster arrow) should increase the product vs what a heavier arrow would do (only increasing mass which is not squared)
Your statement makes sense if you replace KE with momentum.
All bows are more efficient with heavier arrows. Kinetic energy usually increase with arrow weight. This can be negligible with highly efficient recurves or hybrid bows but significant with less efficient longbows or selfbows. The bow in setup B tested with a 360 grain arrow at 173 fps. So that's about 2.7% increase in KE over the 300 grain arrow. Btw you are partly right, momentum always go up more rapidly with increase arrow weight.
What was the hypothesis you were trying to prove?
There are to many variables for me to make any conclusions from this test. Different bows, highly variable penetration medium, friction on the arrow, potentially different tune, etc. For example, a slight dulling (or blunting) of one of the tips would make a big difference on a medium like ply wood.
Good job. but this has been done before. Similar results. If I ever draw a tag to hunt plywood, I will most certainly use a lighter arrow.
Actually, try it using a blunt. If your bow generates enough force, the blunt will punch a hole in the plywood, not forcing a point through but blowing a full sized hole in it, which of course provides for less friction on the rest of the arrow, which will blow on thru.
Thank you for your test.
ChuckC
I have posted this before, but i think you'll find it very interesting.. IF you take the time to watch it.
Part 1
https://www.youtube.com/watch?v=t4RGcyZ_gJY
part 2
https://www.youtube.com/watch?v=VAfK0sBsZBw
This test is trying to determine if Momentum or Kinetic energy will better determine penetration potential in an arrow. Yes it isn't done with real flesh. Never claimed that this will represent an exact hunting scenario. I used what's on hand (which happen to be pretty uniform throughout) rather than sit around argue about theories without doing anything to prove them. Well lubricated soft tissue isn't going to be the issue for most arrows with a sharp broadhead anyway. Its the hard stuff like bone that grips the arrow shaft tight that's gonna limit penetration in most cases. Take this test as what it is until I can get better test materials.
Dr. Ashby already determined that momentum is the better predictor, using real animals no less. His research is on this site.
Not just Dr. Ashby, but lots of Professional Hunters/Guides, along with the hunters themselves.
Depending on the animals, there can be more to consider than flesh and bone; i.e. feral pigs. The big males have a "shield" of gristle that isn't like bone, or foam, or plywood, etc. It's like...gristle.
Water buffalo (haven't hunted them, but almost went and studied it long and hard for over a year before an injury cancelled my trip for me). You may have to penetrate a thick layer of mud/dirt, hair, and over an inch of hide just to get to the flesh and bone. That's going to be a really tough test medium to replicate...but even if you did, we already know what the guides have found works best.
Nativestranger ...
I think I understand what you're trying to do.
TxAg has a VERY good point.
As you said yourself...bows are more efficient with heavier arrows..ie KE changes with different arrow weights.
KE measures the energy required to put something in motion....in a 100% efficient machine/environment you'd really have good #'s to work with...bows aren't 100% efficient in propelling an arrow.
So you end up with this "fuzzy" number that doesn't really mean much in the world of hunting.
also...aaaa heck...just read what others have tested..it's all been done and figured out and will be a lot easier on ya bud.
No reason for me to regurgitate it.
If ya really want to know which arrow has more penetrating power (giving they're all tuned the same etc, etc,etc) and want to do it yourself .. just multiply the weight by the speed. The set up with the highest # wins. Much easier...lol
Test those setups/arrows at different yardages and you'll really learn something.
Good luck to ya. :thumbsup:
Speed x weight= Momentum. Speed x speed x weight = Kinetic energy. Right now the setup with more momentum, less KE doesn't seem to penetrate any better even though I initially thought it would.
I have read Ashby tests. But they are inconclusive as to whether KE or Momentum is more important. Shooting the same bow with different arrows will always produce both higher KE and higher momentum on the heavier arrows. And his heavy arrows also has significantly higher FOC skewing results.
Here's something to think about. If tests were done comparing between a 50# bow and a 30# bow and the 50# bow out penetrate the 30# bow on plywood, then I am pretty sure nobody would question the validity of the test. If the 50# bow out penetrate the 30# bow again on ballistic gel, phone book, target foam. Is it reasonable to assume that it will be expected to perform better on live game? If given 2 unknown bows and one always stick an arrow deeper than the other on plywood. Most logical person will again choose the one that does better. So isn't it funny that all of a sudden this test medium is now invalid when testing arrows of different properties?
Now if anyone can suggest a better test medium then by all means I will try my best to repeat the test with it.
I can't help but look at every one of these penetration tests. I never see any relevant data.
All the tests are done into some medium that uses friction on the arrow to determine penetration. A light arrow usually wins. Most of the time the data fails to disclose arrow shaft diameter which is the determining factor.
Plywood is a useless medium for any real world scenario unless you just want to play around with shooting holes in it.
Have fun bud.
:thumbsup:
Looks like Blackhawk and Scott are correct in their prediction. Now to see if I can get insulation foam suggested by JimB.
I believe this simple test has no value, there are just too many variables. I can make a 600 grain arrow from a 50 pound bow skip off a plastic bottle cap just by varying the angle of impact (it only takes being 10 to 15 degrees off perpendicular if the cap isn't anchored). I don't think that proves the combination is not good for hunting. As the speed of the arrows is different in your test, the angle of impact is different due to different trajectories. The difference in observed penetration is to small to ignore these variables. That's one example. As I said, too many variables.
I don't think comparing fresh bone to plywood provides much value either. Its been my experience that fresh bone in up to elk size animals cut/split (ribs anyway) rather than shatter like ply wood. I believe some one did a post here years ago comparing penetration in fresh deer scapula to dried ones and found that the fresh/split cut also rather than shatter. Maybe someone remembers that and can provide verification.
If I sound overly cynical, my job requires me to evaluate vendor data to determine whether to include their products in our designs (or whether more testing needs to be done). In my 30 years of doing this, I have found that most vendors design tests that show their product is better than their competitors rather than to provide usable, more applicable, data. I can't help but pick "test" data apart. Unfortunately there is no ASTM method to measure arrow penetration in animals to end these debates (then we would be debating the test method).
"I have read Ashby tests. But they are inconclusive as to whether KE or Momentum is more important. "
Read them again.The tests were very conclusive and he goes to great length to show that momentum is far more relative to penetration than KE.
Here is another article that examines this:
http://www.tuffhead.com/education/formulas_momentum.html
another:
http://www.africanarcher.com/momentumKENETICS.html
another:
https://www.qdma.com/articles/momentum-beats-speed-for-lethal-arrow-hits
another:
http://www.tuffhead.com/ashby_pdfs/ashby%20ours/PDF%20Momentum,%20Kinetic%20Energy%20and%20Arrow%20Penetration.pdf
Some other stuff to consider when shooting in to man made mediums:
diameter is a big deal.Shaft makers talk about a shaft being 5/16" in diameter but actual specs may shoe they are from .287 to over .300.I have shafts in this range and they may be called 5/16" diameter but they are all different and minor fractions of difference in diameter will change the equation in man made materials.
To compare two different arrow setups,they have to be EXACTLY the same diameter.They also have to be the same FOC unless they are 18% or less.
Shaft finish also effects penetration so both arrows need to have the same shaft finish.Dipped shafts (wood grain,camo etc)are a drier texture and don't penetrate as well as plain carbon.
Your heavier shaft shows a carbon collar,which stops against the wood.Maybe the black shaft has one as well,it doesn't show,but if it doesn't,that will drastically skew results.
"And his heavy arrows also has significantly higher FOC skewing results. "
This also is untrue.Many of the tests used standard FOC arrows and when he was testing momentum VS KE,this was accounted for.
Ashby has tested all this stuff to death for over 28 years and $300,000 dollars spent.I've been delving in to this stuff nyself for about 8 years and don't have the time,money or patience that Doc Ashby does but I do run some occasional tests and all of those have correlated well with Ashby's findings.
I can tell you this,following what I have learned from the Ashby reports,using a combination of increased arrow weight,high FOC etc,I have more than doubled penetration from where I started.I'm relegated these days to bows in the low 50# range and these are penetrating way better than my former setups which were 60-66# bows and 9-10 GPP arrows with normal FOC.
Honestly I think your arrow shafts are too different to get reliable results from.If I were testing,I would want both shafts to be black,identical diameters,measured with electronic calipers and any footings or collars to be identical.Again,Ashby has already done this to death.I enjoy testing too but mine will never be as exhaustive as his.
So far,just following his results,my setups have increased in efficiency way beyond what I ever thought possible.
Anyway,good luck with your testing.Some day when I get enough time,a chronograph and a shooting machine,I plan to do some of my own.I spent over 2 years trying to come up with 2 arrows of exactly the same diameter but hugely different FOC numbers plus same diameter arrows with similar FOC but one light and one very heavy.That's not as easy as it sounds but I finally cracked the code.
Besides testing them for penetration,if possible,I'd like to flight shoot them from a machine.We'll see.
Just to clarify some stuff. That's the insert behind the point not a carbon collar. The lighter shaft has it too. Both shaft are the same 5/16 diameter. Within 3% Foc difference. Points are unsharpened. Shaft finishing doesn't matter as the heavier shaft didn't penetrate past the insert. No angle difference between them as they are shot from the same position to within 2 inches on the plywood. I admit some part of this test isn't perfect. Shooting at a non homogeneous medium like a live animal will give inconsistent results as well depending on where you hit. If the the theory that momentum and weight significantly outweigh KE, it should still show here without the need to formulate excuses. I often hear claims that light arrows gives me only 2" of penetration on animal or bounces off deer while heavy arrows pass all the way through. That's of course quite serious claims made in totally non controlled test environments. If that's true then it should show up in my test without the need to split hairs like small angle differences, shaft diameter... so on. Are any tests done other than Ashby that supports the momentum theory? The only 3 other test I can find are from Ken B, Ike and Ripfletching and all those concludes weight doesn't matter much in penetration.
QuoteOriginally posted by Nativestranger:
Setup A 400 grain arrow 151 fps
Setup B 300 grain arrow 185 fps
Speed verified with chronometer. Setup A has 33% more arrow weight and ~10% more momentum. Setup B has ~15% more KE. Which do you think will provide more penetration into hard medium like bone? Will be testing them on 3/4" plywood.
In my response to the original question I gave the edge to the heavy arrow. That said, and at the risk of seeming a sore loser, I'll throw in my thoughts on your results.
The flaw, IMO, is the unrealistic velocity spread. While tuning considerations may not have allowed shooting from the same bow, they both should have been chronographed from the same bow and then those velocities matched when shot from a bow to which they were matched.
I have extensive chronographed data from eight bows with draw weights ranging from 38# to 46# with each bow shot with two arrows. One is 525 grains and the other 675. The velocity spreads between the two are mostly in the single digits.
A real world comparison would have had your 400 grain arrow running at around 173 to 177 fps.
The 2 arrows are shot from 2 bows. 400 grain from a 37# bow. 300 grain from a 40# bow. I draw them to my draw length of just under 26.5". chrono tested them and set it up this way so the 400g arrow has more momentum/ weight and the 300g more kinetic energy. Yes you right that the velocity spread is quite big. But that's how you get the KE up for the lighter arrow. There's no other way to it. Then again if Momentum and weight (as what was previously thought) is the deciding factor then the velocity difference should not matter.
I might add that I also tested both arrows from both bows.
*The 40# bow tested 164 fps with the heavy arrow
*The 37# bow tested 173 fps with the light arrow
*The same bow penetrated the same with both arrows.
*The heavier bow always penetrate deeper than the lighter bow regardless of arrow weight.
I believe I see what you are getting at NS but to me it appears you are supplying a situation that is contrived and not based on fair comparison at all.
Just because one is heavier does not mean you can just toss it against the wall and expect it to knock it down. There comes a point in the experiment where the difference in speed is so great that there is no competition, and what then does that really show ?
Your testing was appreciated. Thank you. Points were made and I was drawn to think about the actions and results.
I will, however, still be using 580 grain arrows for elk season this year and wishing they were just a wee bit heavier.
CHuckC
Thanks.I understand what you are saying but again-5/16" is an industry term that spans a variety of outside diameters.Usually,these shafts have an inside diameter of .245-.246" but the out side diameters vary widely.Caliper measurements!
Personally,when I test penetration,I want a medium that the arrows will go deeply into-like 2/3 of the shaft length.This way,differences are more obvious.I've only been testing this stuff for 8 years but my findings are different than what you have come up with from shooting 2 sets of arrows from 2 different bows,into a hard medium.
"Are any tests done other than Ashby that supports the momentum theory"
Honestly,I get this all the time.I assume you did not read any of the articles that I gave links to.It's funny how a few minutes of video on Youtube,trumps 28 years of testing with all details of the tested arrows shown.He doesn't say a 300 gr arrow vs a 400 gr arrow when it was actually something else and if the arrow diameters were slightly different,that was noted.
My tests show that increasing arrow weight by say 10%,increases penetration 20%.If you bother to read,you might understand why this occurs.
What is seldom discussed about the Ashby reports is that during those 28 plus years,he logged data on 627 plus big game animal harvests of his own plus some from other hunters and cross referenced that data with the penetration tests.If ever saw the data sheets and criteria for this,it is thorough,way more detail than I'd have patience to provide.But yeah,a couple unknown guys shooting a handful of arrows with sketchy specs,om Youtube,for sure,has more relevance.This too,has been done to death.
"I have read Ashby tests. But they are inconclusive as to whether KE or Momentum is more important. "
"And his heavy arrows also has significantly higher FOC skewing results."
These statements are incorrect and you seem to have sloughed over them.
Good luck with your "testing"
Like I said I did test the 2 arrows from the same bow. Please understand I am not doing this to prove a point or trying to promote light arrows over heavy arrows or the other way round. I personally always shoot over 11.7 gpp - 10.3 gpp arrow weight from my bows. They shoot sweeter that way. I am simply curious to the science of momentum vs energy and decided to do some personal testing and share with you the results. Take the test as what it is. Another set of data. Thank you for suggestions and pointing out the limitations. I will also look over your links and Ashby test reports in more detail.
I did read up those links. They get their info from Ashby. I would like see independent and real world tests.
"My tests show that increasing arrow weight by say 10%,increases penetration 20%.If you bother to read,you might understand why this occurs"
That's quite substantial. If true then it should be easy to prove. It didn't show up in my tests when shooting the 33% heavier arrow from the same bow. But I will get another softer test medium to try.
Would you rather get hit with a 30" wooden dowel or a 30" piece of rebar?
If I can keep arrow speed reasonable, I'll take the heavy arrow every time. I've seen the results of using both (especially in my wheel bow days). It's worked for me this far.
Others may have had different experience.
QuoteThe 2 arrows are shot from 2 bows. 400 grain from a 37# bow. 300 grain from a 40# bow. I draw them to my draw length of just under 26.5". chrono tested them and set it up this way so the 400g arrow has more momentum/ weight and the 300g more kinetic energy. Yes you right that the velocity spread is quite big. But that's how you get the KE up for the lighter arrow. There's no other way to it. Then again if Momentum and weight (as what was previously thought) is the deciding factor then the velocity difference should not matter.
Of course it matters! :eek:
Measure momentum or measure kinetic energy. Velocity matters!
I dug through some stats of a test I did about this time last year. I chronoed eight bows with two arrows. One is a 520 grain the other a 650 grain. Both cedar, both full length/same length, both fletched the same. Out of eight bows here is the velocity differential that I got from these two arrows. The average of four shots for each arrow. The bows were all weighed on my scale and the scale checked for accuracy with a 45# weight. the first velocity is for the 520 and the second for the 650.
bow one 28# 153-146 = 7
bow two 30# 139-131 = 5
bow three 34# 149-144 = 5
bow four 46# 164-156 = 8
bow five 44# 170-163 = 7
bow six 40# 163-154 = 9
bow seven 37# 153-146 = 7
bow eight 35# 165-157 = 8
I doubt if many bows will produce significantly different results, yet your test velocities were spread far beyond what is typical.
So, I then went to the range alongside my house with bow number six. Selected because it is what I will shoot this year for hunting season and also because the two arrows tested below fly equally well from this bow. Once again, these are POC shafts full/equal length, near identical fletch, identical poly finish on the shaft, both 11/32", one with a 190 grain head and the other with a 145 grain head. Obviously, FOC will not be the same. The shaft weights were 575 grain and 525 grain. Fifty grains difference and with a rather low percentile difference since they are both fairly heavy arrows compared to the 300 an 400 you shot.
I shot seven shots with each into a new foam target that had had only five shots into it prior to this test. None of the test shots came even close to any pre existing hole.
So, I measured and averaged the seven shots with each arrow. They were shot alternately so that there was not a shooter fatigue problem or a creeping variation in shooting form.
Came up with this:
575 grain arrow average penetration 10.27"
525 grain arrow average penetration 9.71"
I suggest that you find a bow that will shoot both arrows equally well and do another penetration test. I think your results will be different. Or, you can send the arrows to me and I will sort through my cache of bows for one that shoots them equally well and do this same test.
So, season opens in less than two weeks and I just wasted a shooting session on this! :scared: Gotta get back down to business. :)
My velocity spread is typical for bows with decent efficiency. Again the numbers for the 40# bow: (36# @ my draw)
300g 185 fps 8.3 gpp 23.9 ft.lbs KE
400g 164 fps 11.1 gpp 22.8 ft.lbs KE
As you can see the 2 arrows are almost 3 gpp difference in my case and it gained about 21 fps going to the lighter arrow. It also lost about 5% KE and dynamic efficiency. Velocity gain about 7.5 fps per gpp. Very typical value for short bows with highly reflexed limbs. I have seen some bows gain 9 fps going from 9gpp to 8gpp. Of course with some bows the velocity gain with lighter arrows will be less. That doesn't mean it can shoot both arrows equally well. Rather it means the bow is inefficient with light arrows and energy drops quickly with arrow weight. Example straight limb longbows over 66". Hand shocky with light arrow and always chrono about the same with different arrows. With different bow designs, penetration behavior may be entirely different from mine which I forgot to mention. By all means shoot what works best.
Your 2 arrows are 50 grain difference and almost all that is the point weight. Vastly different FOC and dynamic spine may have cause the penetration difference. I used both heavier point and heavier shaft on the heavier arrow.
I gotta unfollow this one..
Have fun gents.
I think it can be said that any arrow of reasonable weight, with a sharp, cut on contact broadhead, flying straight ( well tuned to your outfit) has plenty of "force" available to kill a whitetail or mule deer, the target of opportunity for most of us.
For smaller game, obviously the same holds true. For very much larger game, well, questions remain and that is something you should consider for yourself when preparing for such a hunt.
ChuckC
Geez, I'm with Zradix on this one!
Your numbers just don't relate to your keystrokes.
QuoteOriginally posted by monterey:
QuoteOf course it matters! :eek:
Measure momentum or measure kinetic energy. Velocity matters!
I dug through some stats of a test I did about this time last year. I chronoed eight bows with two arrows. One is a 520 grain the other a 650 grain. Both cedar, both full length/same length, both fletched the same. Out of eight bows here is the velocity differential that I got from these two arrows. The average of four shots for each arrow. The bows were all weighed on my scale and the scale checked for accuracy with a 45# weight. the first velocity is for the 520 and the second for the 650.
bow one 28# 153-146 = 7
bow two 30# 139-131 = 5
bow three 34# 149-144 = 5
bow four 46# 164-156 = 8
bow five 44# 170-163 = 7
bow six 40# 163-154 = 9
bow seven 37# 153-146 = 7
bow eight 35# 165-157 = 8
I doubt if many bows will produce significantly different results, yet your test velocities were spread far beyond what is typical.
So, I then went to the range alongside my house with bow number six. Selected because it is what I will shoot this year for hunting season and also because the two arrows tested below fly equally well from this bow. Once again, these are POC shafts full/equal length, near identical fletch, identical poly finish on the shaft, both 11/32", one with a 190 grain head and the other with a 145 grain head. Obviously, FOC will not be the same. The shaft weights were 575 grain and 525 grain. Fifty grains difference and with a rather low percentile difference since they are both fairly heavy arrows compared to the 300 an 400 you shot.
I shot seven shots with each into a new foam target that had had only five shots into it prior to this test. None of the test shots came even close to any pre existing hole.
So, I measured and averaged the seven shots with each arrow. They were shot alternately so that there was not a shooter fatigue problem or a creeping variation in shooting form.
Came up with this:
575 grain arrow average penetration 10.27"
525 grain arrow average penetration 9.71"
I suggest that you find a bow that will shoot both arrows equally well and do another penetration test. I think your results will be different. Or, you can send the arrows to me and I will sort through my cache of bows for one that shoots them equally well and do this same test.
So, season opens in less than two weeks and I just wasted a shooting session on this! :scared: Gotta get back down to business. :) [/b]
May I know what bows are bow #1 and #8? What is your drawlength? Those are very impressive figures.
Your data for bow #1:
28# 650 grain 146 fps
(146 x 146 x 650) / 450240
Kinetic energy = 30.77 ft.lbs
Blacky Schwarz's controlled test data for 45# Bear super kodiak recurve:
44.5# 399 grain 186 fps KE= 30.28 ft.lbs
Good Lord your 28# bow shot with fingers produces more arrow energy than a 45# recurve bow shot with a shooting machine!
Even given a very optimistic efficiency figure of 80%, the bow's stored energy works out to be at least 38.46 ft.lbs. So it has over 1.37 Stored energy/ draw force value. That figure beats many compound bows drawn to 30"! Or maybe you have a 38" draw. Which is why I am curious how did you arrive at those figures. What was the bow used?
How is this related to Traditional Bowhunting? Can someone explain to me what has happened to this site?
I can see where it relates to trad. hunting. It tells me that you don't have to shoot high poundage bows with very heavy arrows to get good penetration on certain animals.
First off, Let me clarify an error on my part. This goes way back to when I originally tested these bows and the draw weights were summarised inch by inch for the sake of later creating FD curves. In a hurry while typing the above post, I snatched the draw weight of Bow #1 from the wrong position. The correct draw weight at 28" is 34#.
All the draw weights listed are based on AMO standard of 26 1/4" measured at the deepest belly side of the grip. My draw is pretty much 28". However, my draw length, and anybodies for that matter, will vary depending on the design of the handle and grip. For example, an ASL bow with a flat grip area is shot with the base of the thumb pressed into the handle. This will usually cause a small loss of draw length compared to the pressure point being in the web of the thumb and the index finger.
Irregardless, due to the depth or front to back thickness of the handles on the ASL type bows tested it is pretty much a wash since they tend to be deeper from the low point of the grip to the back of the bow. IOW, depths in the range of 1.75" to 2" and in one case a bit more.
One of the bows, bow #2, is an osage self bow with only 1.25" depth in the grip.
With the exception of #2, all are wood/glass lam bows.
But, all in all, if one uses the common method of measuring the length of arrow actually drawn to the back of the bow, the draw lengths for all of these bows when drawn by me are right in the 28" range.
A somewhat lengthy explanation, but possibley pleasing to one of your profession. :)
Bow #1 is a 1970 vintage Shakespeare Super Necedah 54" recurve.
Bow #2 is an osage self bow.
Bow #3 Is my own build, a 68" ASL with about 1/4" of string follow.
Bow #4 Is my own build, a 68" ASL with flat limbs and a 2" deep handle.
Bow #5 is a pre 70's vintage Howatt Cavalier 62" static recurve.
Bow #6 is my own build, a 66" ASL with flat limbs.
Bow #7 is a very odd little bow that you need to see and shoot to really appreciate. It is a 1954 vintage bow with no name applied to it. It has an aluminum handle, is ambidextrous, has limbs that are made of solid fiberglass, very narrow and conforms very much to an ELB in that it narrows from front to back and side to side with fairly narrow tips. When you look at this bow the first thing that crosses your mind is "kid bow", but it is not! This bow has taken big game.
Bow #8 is my own build, a 68" ASL with approximately 7/8" of reflex that is built in a continuous arc of a circle in the last 24" of the limb.
Bow #8 is impressive. Funny thing is, when this bow was finished I did not like it at all. Did not like anything about it! It is however a very good performer. Even at that, it does not fit my style very well and I cannot shoot it as accurately as most of the others. The other great performer is the Howatt static recurve. It too is a poor fit to my hand and form and not as accurate for me.
Just about the most pleasant to shoot of all eight is the osage self bow. A good fit to my hand, smooth drawing and stack free out to 29". I would hunt with it but it does not meet the minimum draw weight requirements for big game in Colorado.
Thank you for the clarification. I did enjoy reading up on your bows used for the tests.
One thing to consider is this: your data do seem peculiar to me in that the velocity gain is very little when dropping arrow weight. Put it in another way the energy lost going to the lighter arrow seems quite a lot. Example bow #6 (which you tested for penetration) lost almost 12% kinetic energy going from 650g to 520g. Anyway your tests may simply conclude the same thing as mine. Less KE = less penetration. On my 40# bow going from 400g to 300g the KE lost is only 4.5% and there's no noticeable difference in penetration.
This test data of a 60" recurve is taken from Arctradionly. Very precise tests done with shooting machine. Notice going from 12 gpp to 9 gpp the speed increase is 25 fps. Notice that KE and efficiency stays more or less constant above 10 gpp. But drops marginally going to 7 gpp. This shows that my data are nothing out of the ordinary.
(https://farm1.staticflickr.com/679/20393089638_7580b7a9bc_b.jpg)
KE is a good indicator of energy at impact but not so much after impact.
KE v.s. momentum is a lot like HP v.s. torque.
Those snappy little motors that they somehow get 300+ Hp from have very little torque and are useless for towing and are constantly downshifting when going up hills.
Compared to a small diesel with perhaps less Hp but twice the torque might not be quite as quick but haul the load almost effortlessly .
KE/HP means you got a quick arrow but momentum/torque is what gets you out the other side.
Bow #8 (35#) shoots 520 gr arrow at 165 fps for 28" DL and 650 gr at 157 fps?
This means 165 fps for 14.86 gpp and 153 fps for 18.53 gpp at 28" DL out of a 68" American semi longbow design :scared: :scared: . Was it in bow used in " the Avengers" movie?
That's maybe the fastest trad bow on earth or maybe inaccurate #
Bow #8 Stored energy/ peak draw weight works out to be min of 1.27 (assuming a very optimistic 80% max efficiency) a value not only beating Border's super recurve limbs but also many compound bows. Quite remarkable for any longbow.
QuoteOriginally posted by hybridbow hunter:
Bow #8 (35#) shoots 520 gr arrow at 165 fps for 28" DL and 650 gr at 157 fps?
This means 165 fps for 14.86 gpp and 153 fps for 18.53 gpp at 28" DL out of a 68" American semi longbow design :scared: :scared: . Was it in bow used in " the Avengers" movie?
That's maybe the fastest trad bow on earth or maybe inaccurate #
Yeah thats what i was thinking too. if you gave that bow 1/2 a fps for each grain of arrow weight it would be shooting a 10 GPP arrow 242 fps...
It was over a year ago that I did those numbers. Last thing I want is to mislead anybody and would never intentionally present erroneous data.
I will pull bow 8 on the scale later today and will also double check the scale accuracy. If my scale numbers are correct, I will reshoot the bow over the Chrony.
OK, put #8 on the scale again and drew it four times. It averaged 36.5#. Next, I checked the scale with a 22# weight (a sender international metric 10 KG 22# weight plate). It scaled at 21#. That puts the scale at 1/2% error which would correct the draw weight to 38.3#.
So, using that draw weight and shooting over the Chrony again will produce a different profile. I will do that today, but first I have to paint the trim around the front door.
My ballistic gel is ready. Hope to do some testing with broadhead soon. This is costing me money and time but I am willing to do it for the sake of Scientific research.
Does not look good for getting any arrows across the Chrony today. Some bad weather slowed the paint work.
You should send those two arrows to me to try.
Those are just regular GT carbon shafts. Velocity 600 28.8" 100g point and traditional hunter 1535 30.5" 125g point
For the life of me, I can't figure out why anybody would test penetration on anything other than a dead cow. :D
Because dead cows are harder to kill? Wait you can't kill a cow that's already dead. :laughing:
Ok first round of test done. I used 20% density ballistic gel. Feels firmer than human flesh. Friction on the shaft is high compare to real living tissue with blood. Since I only have 1 type of broadhead in weight of 100g, I only tested with one bow shooting both arrows. The the lighter arrow 300g. Heavier arrow 375g. Result: The lighter arrow penetrated about 1/2" more than the heavier one. Not a whole lot there. It could be the margin of error in draw and release.
(https://farm6.staticflickr.com/5714/20485599069_e1fd71b9bb.jpg)
(https://farm6.staticflickr.com/5617/20663171632_1a4eb324fa.jpg)
(https://farm1.staticflickr.com/781/20646145446_636dbf3a25.jpg)
Broadhead used: Cabelas copperhead with 3 replaceable lutz blades
(https://farm1.staticflickr.com/586/20663191362_e191f81b16.jpg)
Bow used: Grozer biocomposite Scythian bow 37# @28" (https://farm1.staticflickr.com/752/20672504575_22324b4cdb_b.jpg)
Repeated the tests 2 times. Moving the back stop further away. The heavier arrow out penetrate the lighter one by 1/3" on the last attempt. Given over 17" penetration, there's overall almost no difference in the ability of both arrows to penetrate the test medium.
(https://farm1.staticflickr.com/758/20053116663_0b0552d0ab.jpg)
(https://farm1.staticflickr.com/633/20647796466_738d7be72c.jpg)
To continue with the testing I will thicken the ballistic gel by another 10% to make real tough and shoot a mix of broadhead and field point.
I'd suggest stacking 2-3 gel blocks in a row and shooting them.
..so the arrow never penetrates out the other side.
...or make the gel in something longer..like a cooler or something.
I personally think the density you have is good.It allows the arrow to penetrate deeply without the fletching contacting the medium.
If I were going to go through that much trouble though,as I said before,I would want the shaft finish and diameters to be exactly the same.Just the shaft finish alone can show that much difference in penetration.You would also be surprised how much effect a few thousandths of an inch diameter will make in penetration in mediums where the arrow is stopped by friction on the shaft.Again,because a maker calls a shaft 5/16" doesn't mean it is exactly that.They vary a lot and either calipers or more specific specs should be used to make sure they are exactly the same if you want a true comparison.
Years ago,Fred Bear did some ingenious testing to determine what effect arrow weight had on impact.A weighted pendulum was used to test impact.He tested 6 different arrow weights out of eight different bows,shot from a machine.The beauty of this type of test is that it eliminates any question about test medium and penetration and also eliminates issues like shaft diameters,finish etc which plague penetration tests.His testing isolated impact and the effect that arrow weight had on it.
In all cases,the heavier arrow impacted more-with every bow.He even goes so far as to note that in one instance,a 45# bow with a 17.7 GPP arrow came within 1% of the measured impact of a 60# bow and 10 GPP arrow.
He settled on a preference for 9-10 GPP as a balance of trajectory and impact force.
Good suggestions. Will try make anotger block of gel. As you can see from photo. Both shaft are flush with the standard gt insert. Small difference in shaft diameter should not matter for soft elastic medium like ballistic gel. It still grips the shaft. Ok shaft finishing do matter. But I don't think there's much difference in friction here. Both finish are smooth but not shiny type.
The diameter does matter.It's about friction.The way to rule it out,is to use two shafts identical in diameter.As have others,I've tested both aspects.it makes a difference.
Tested with 30% ballistic gel. I was able to move the back stop way back. So both arrows penetrate deeper and not stopped by the back stop. This time the lighter arrow penetrated about 4.5" deeper and almost to the feathers. Though I am not fully convinced. I have to re melted and test again with 2 blocks.
(https://farm1.staticflickr.com/630/20505042799_7eefe225a9.jpg)
Latest test results in. Used a 30% density gel block and a 20% block lined up together. The 30% block really grips the shaft hard so I am not able to pass through both gel blocks. The bow used is 40# @28 drawn to 26.5". This time the 375 grain shaft penetrated about 1/4" more than the 300 grain. Given about 11" total penetration that's about 2.5% difference. Easily explained by the drop in KE on the lighter arrow.
(https://farm6.staticflickr.com/5645/20710503965_16925f813f.jpg)
(https://farm1.staticflickr.com/627/20089568523_299ceb4730.jpg)
Final test results in. Used the lighter 37# bow with single block of 30% ballistic gel this time. Both arrows penetrated about 10.5". The lighter arrow about 1/8" more.
(https://farm6.staticflickr.com/5801/20111025633_de05bf754a.jpg)
(https://farm1.staticflickr.com/738/20722809442_af4fae7a3c.jpg)
(https://farm1.staticflickr.com/600/20545395959_07dc91b784.jpg)
Conclusion: There seems little to no correlation between arrow weight/ momentum and the ability to penetrate ballistic gel with a broadhead. Kinetic energy seemed to determine penetration.
This is my interpretation and opinion of the results:
Penetration as tested depends on the total energy in the moving arrow. Which makes sense since to cut a wound channel, work has to be done and the amount of work done depends on the total energy available. The amount of arrow energy is determined by the stored energy of the bow multiplied by the efficiency factor. And that's why in my case the heavier bow always penetrated better than the lighter bow regardless arrow weight. Now that's not to say for your setup you won't get better results with a heavier arrow. But if you did, that is probably a function of the bow being more efficient and therefore having slightly higher kinetic energy with the heavier arrow. Thank you for looking and have a nice day.
Jimmy, I would not take the comments you are getting as negative criticism. Just good points to add to the thinking on this issue. I very much appreciate all your effort. Experiments of all kinds and all topics tend to draw healthy scrutiny. Well done.
Thank you Scott. I never took the comments negatively. Not at all. I welcome construction criticism and healthy scrutiny. Without the same mindset I would have just accepted commonly held beliefs and not be bothered to do any actual testing of my own.
Ok, finally got an opportunity to reshoot the bow #8.
I used three arrows this time. One 450 grain, one 525 grain and one 560 grain.
Remember that I retested the actual bow weight and came to 38.3# at 28". I also checked my actual draw length with that bow and determined it to be an actual 28" draw.
I replaced the battery in the chronograph just for good measure. I also used a better quality scale to weigh the arrows.
Each arrow was chronoed six times for the averages.
Here are the results;
68" slightly reflexed long bow 38.3# @28"
450 grain arrow
161.9
162.5
159.4
162.7
164.0
163.5
----------
162.33
525 grain arrow
155.9
155.2
155.9
155.4
154.1
156.3
---------
155.47
560 grain arrow
15.08
15.06
150.0
148.5
150.3
150.6
--------
150.13
I'm still pretty well convinced that you are arriving at erroneous conclusions regarding differences between KE and momentum as applied to penetration.
You large difference in velocity between the two arrows is problematic. Notice that with the lightest and heaviest arrow above the difference of 110 grains results in a difference of only 12.2 fps.
Granted, the percentile difference in weights is not exactly the same, but the difference betwen percentage difference between arrow weights and differences in velocities shows a very large differential. There, I believe lay the source of your conclusion that KE outweighs (pun intended) momentum in penetration.
If you are shooting the asiatic style bow in the previous picture, I think it may explain the large velocity differential. That type of bow is known for preferring a lighter arrow and was in fact designed by our rather brilliant (if not engineering educated) predecessors to do just that.
OTOH, the bow I am shooting is known for it's ability and effectiveness in hurling heavier arrows.
So, IMO, one problem in your test results is that your arrows are flying at a way disproportionate velocity. So disproportionate that the penetration results are nearly an even draw.
I'm pretty sure that the effects of variables in the surface of your two arrows along with other differences cited above are not enough to produce the near even up penetration results you are getting.
If you have another bow available that would produce velocity differences of 5 to 10 fps with those same two arrows I think you will find the 400 grain arrow out penetrating the 300.
Thank you for taking the time to test your bow. I think your results are typical for longbows. And my results are typical for shorter recurve bows. The big difference in speed in first test is due to the heavier bow shooting the lighter arrow vs the lighter bow shooting the heavier arrow. When the same bow shot the 2 different arrows speeds are closer. The 40# bow (drawn 36# @ 26") shooting the light arrow (300 gr 8.3 gpp) was averaging 185 fps 22.8 ft.lbs. Shooting the heavier arrow (400g 11.1 gpp) was 164 fps avg 23.9 ft.lbs. So that's 19 fps difference between 11.1 and 8.3 gpp. But that's 33% difference in arrow weight. Please note that as gpp goes down the speed goes up more rapidly, at higher gpp speed difference is less. Your arrows are ranging from 11.7 gpp to 14.6 gpp. 12 fps difference. 7% difference in KE with 24% difference in arrow weight. Longbows with long working limbs tend to be more efficient with heavier arrows. While recurve bows with short working limbs tend to shoot both more or less as efficiently. Horsebow or not the difference just in style of grip. I have a Pinnacle recurve with black max medium limbs and the performance is similar. But I don't shoot that anymore since I switched to right hand. Please do take a look at the test data I posted of this 60" one piece recurve tested by Arctradonly. This particular bow gained 25 fps going from 11 gpp to 8 gpp. And there's nothing special about that bow. Just a regular 1 piece hunting bow with typical recurve profile limbs. Also noticed the energy and efficiency curve is quite flat from heavy arrows to light arrows indicating the bow is as efficient shooting a wide range of arrow weights.
(https://farm1.staticflickr.com/679/20393089638_7580b7a9bc_b.jpg)
For my case, if i have the 300gr arrow and 400 gr arrow being only 10 fps apart like you said. Let's say 164 and 174 fps. The resulting difference in energy is nearly 20% less for the light arrow. That's unlikely for well designed modern bows. Maybe we can see that behavior with very slow and over built D shaped longbows. But these are my results with my bows. May or may not be applicable to you. The point of this test was originally to test if Momentum or KE is the determining factor in penetration NOT whether a light or heavy arrow is better. For me both arrows penetrate about the same for each bow. The arrow with higher KE always out penetrate the one with higher Momentum. In your case you have better penetration with heavy arrows. Your results doesn't contradict my results at all because your heavy arrows also have 7% more KE than your light arrows. It just means your particular bow is better at imparting it's energy into the heavier arrows. As you can see this test data for Great Plains 68" longbow is quite similar to the results you are getting. About 13 fps difference between 11 gpp to 14 gpp. Efficiency difference between light and heavy also about 8%. Compare this to the data for the recurve above. Much less fps difference between arrow weights when compared to the recurve. Efficiency dropping much faster with lighter arrows. All these are just the difference in arrow weight vs efficiency between the styles of bows. Doesn't mean one must be right while the other is wrong.
(https://farm6.staticflickr.com/5821/20755201000_3db0c15f61_b.jpg)
My conclusion is Kinetic energy is important in penetration while momentum is irrelevant. Its easy for you or anyone with a chronometer to prove me wrong. All you need is shoot a lighter arrow with high KE, low momentum from one bow and a much heavier arrow with higher momentum lower KE from another bow 5# weaker draw weight. Both arrows same foc same diameter. See which one is better in ballistic gelatin or plywood or whatever medium that's uniform. If you can prove that a higher momentum arrow can consistently penetrate better than a higher KE arrow then I may have to revise my testing procedures see what went wrong.