Home › Forums › Bows and Equipment › A Case Study: How the 'stories and experiences' thread helps us understand arrow design.
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Here’s an example of how and why all the information we can assemble, regardless of the equipment used, helps expand our understanding of how arrow design affects arrow terminal performance; which is the entire purpose of this forum.
If you will check out the “CSI – Mozambique Penetration Test” on the Bowsite forum site (http://www.bowsite.com/bowsite/features/articles/equipment/penetration2/) there is some very useful information, and I highly commend Mr. Pat Lefemine for collecting and posting the data from his Cape buffalo kill shot and three test shots. I do wish the skin had not been removed from the buffalo before the test shots were taken, but as Mr. Lefemine correctly states in the associated discussion thread, the skin of the Cape buffalo (over the chest area) is not very thick, and its absence probably had little effect on the results. Having hunted and tested on both Cape and Asian buffalo, the structural differences between the Cape and Asian (as noted in the 2004 Study Updates) is what makes the Asian buffalo somewhat more difficult to penetrate than the Cape buffalo, with skin thickness over the chest area being one of the very notable differences.
Please check out the results of the Cape buffalo shots shown on Bowsite. The bow used is a 90# compound, the arrow is an 1100 grain double-shafted one, and the broadhead a double-beveled, 200 grain Muzzy single blade. The reported velocity is 200 fps. That translates to 97.7 ft.-lbs. of kinetic energy (KE) and 0.977 Slug-Feet/Second of momentum.
These results make an excellent comparison base against the best performing, penetration maximized arrow setup tested in the Study, to date. That would be the Internally Footed EFOC arrow, as detailed in 2007 Update, Part 3. The bow used was an 82# at 27” draw, straight-end longbow. Arrow weight is 790 grains, only 2/3 the mass of the compound’s arrow. Velocity was a modest 151 fps, 25 % slower than the compounds arrow. This gives 38.9 ft.-lbs. of KE, less than 40% of the KE carried by the compound’s 1100 grain arrow. It has a momentum of 0.523 Slug-Feet/Second, just over one-half that of the compound’s heavier arrow.
On a very large adult Asian buffalo (not skinned), on all back of the shoulder shots, from a test distance of 20 yards, these 790 grain, penetration-maximized arrows broke both the entrance and exit side ribs on each hit, with 100% of the shots (5 of 5) providing an exit wound through the 1” thick skin. Median tissue penetration (the length of the wound channel through the tissues, not counting off-side arrow protrusion) was 23.875 inches. On its one shoulder shot it broke ribs on both the entrance and exit sides, with the broadhead passing completely through the off side rib, but failed to exit the skin.
This same bow and penetration-maximized arrow setup also produced an exit wound on a hunted trophy class bull, sticking some 20” of shaft out the off-side. All of these shots exceed the penetration shown/described by any of the compound’s reported Cape buffalo shots. We can’t directly compare scapular hits, because of the shooting angle differences. The only scapula shots taken in the Study’s testing were taken at 45 degrees, quartering from the front. As noted in the Update, that shooting angle was used because this particular test sequence was primarily directed at the structural integrity aspect of the Internal Footing, not at penetrating the scapula. However, even from this extremely adverse shooting angle one-half (3 of 6) of those shots penetrated the scapula, with two stopping in the on-side rib and one penetrating the underlying rib, entering the lungs.
What accounts for the terminal performance difference, despite the compound’s huge advantage in arrow force? It’s all about getting the maximum amount of ‘useful work’ out of whatever force your arrow carries, and squandering as little as possible on ‘non-productive’ work. This is achieved by assembling the best possible combination of penetration-enhancing factors.
Assuming that arrow flight is equally well-tuned for the arrows used in both test sequences discussed here, but not having all the dimensions before me for Mr. Lefemine’s arrow setup I can’t compare some features, such as any possible ferrule-diameter/shaft-diameter ratio differences. However, some arrow features can be logically compared.
I don’t have the mechanical advantage (MA) for the broadhead used in the Mozambique testing, but the photos are available to examine. There’s little doubt the MA of the Muzzy 2 blade broadhead used is less than 1/2 that of the Modified Grizzly’s. There’s also a marked difference in the ferrule taper and fade-in between the Muzzy and that of the Grizzly, with a clear advantage in both ferrule MA and ‘smoothness’ going to the Grizzly. The FOC difference would be a big force-saving advantage for the Study’s penetration-enhanced arrow, both at impact and once the bone(s) was breached. The Modified Grizzly’s single-bevel bone-splitting advantage would also have conserved a substantial amount of the available arrow force in breaching the heavy bones.
Remember that each force-saving penetration factor is compounded by each of the other force saving factors; and the same is true for each force-squandering factor. The outcome arrow penetration is not a sum of the improvement yielded by each of the penetration enhancing factors, it is the product of them. Each factor’s influence on the arrow’s penetration, whether good or bad, must be multiplied by the influence of each of the other factors.
The larger the game you hunt, or the lighter the poundage of the bow you use, the more important it becomes to maximize your arrow’s potential. The outcomes from these comparable tests are a dramatic example of the potential gains that you can obtain in terminal arrow performance, merely by maximizing the penetration potential of your arrow. Within reason, it is rarely the bow used that determines the outcome. Once it is launched, it’s all about the arrow.
Ed
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Interesting, thanks for the info.
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Thanks, Doc. I’m new here and what a great find this forum is, especially when you personally contribute. The final paragraph of your post above, in particular, sums things up and speaks multitudes. I hope you’re recovering well. Snuffy
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Ed,
Having watched the videos you speak of on Bowsite, I’m confused as to what you mean by the differences in penetration. On all of the test shots on Pat’s buffalo, they got complete penetration, including through the shoulder blade. Could you please clarify the differences in penetration to which you are referring? Thanks.
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Unless I TOO missed, Ed’s message, I think Doc was showing the comparison of a much more powerful bow and heavier arrow with a double bevel to his testing with a longbow, lighter arrow and a single bevel.
Penetration was comparible yes, BUT…….
The longbow and lighter grain arrow “gives 38.9 ft.-lbs. of KE, less than 40% of the KE carried by the compound’s 1100 grain arrow. It has a momentum of 0.523 Slug-Feet/Second, just over one-half that of the compound’s heavier arrow.
By comparison. The “lesser” longbow and lighter arrow with a modified Grizzley gave comparible penetration when compared to a set up with approx double the energy computations.
Sorry for sticking my nose in, Doc. Just know I have more spare time than you do.
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Steve,
I noticed that as well, which was quite impressive. But specifically, I was referring to this quote:
“All of these shots exceed the penetration shown/described by any of the compound’s reported Cape buffalo shots.”
Ed noted that all of his test shots produced exit wounds. All of Pat’s shot resulted in exit wounds as well (including one shot through the shoulder blade). So I was curious as to what I missed with regard to “…exceed the penetration…”
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Steve, you’ve pretty well described it, but also worthy of note is that the penetration maximized arrow consistently achieved exit wounds through the 1″ thick skin of the Asian buffalo.
Looking through the approximately 700 Asian buffalo shots in the current testing serie’s database, one of the notable features is that very few of the arrow setups which manage to traverse the thorax retain (conserve) enough of their force to FULLY BREACH the off-side rib (the broadhead passing completely through the rib, not stopping in the rib); and how few of those that do manage to breach the off-side rib retain enough force to provide an exit wound through the tough, fiberous, thick skin of the Asian buffalo.
Years of repeated and systematic testing, at or very near the same force level, of identical arrows, save one altered arrow feature, has helped isolate the most significant arrow design features affecting arrow penetration. By combining as many on the known factors as I could into this particular arrow setup, a combination was finally arrived at where complete penetration, with an exit wound, was the norm – the most likely outcome on each shot – at the modest level of arrow force at which the testing was conducted.
The significant difference in penetration between the Study’s penetration-maximized arrow and the arrow used in Mr. Lefemine’s test is the amount of penetration achieved (the “work” done) relative to the force required to accomplish that work. That, in physics, is efficiency; doing more work with less applied effort. And this is the goal. As the game gets bigger, or the poundage of your bow gets less, arrow efficiency becomes increasingly more important. There’s no such thing as overkill in bowhunting. No one has ever lost an animal because their arrow penetrated too much.
Ed
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Dr. Ed Ashby wrote: The significant difference in penetration between the Study’s penetration-maximized arrow and the arrow used in Mr. Lefemine’s test is the amount of penetration achieved (the “work” done) relative to the force required to accomplish that work. That, in physics, is efficiency; doing more work with less applied effort.
EdEd,
I’m not trying to be disagreeable. I suppose being an analyst by profession, I like to pick things apart and look at them thoroughly.
I still don’t see any “significant difference in penetration” between the two setups. Complete penetration is complete penetration. I suppose if I had to point to an actual difference, it would be that Pat’s setup also achieved complete penetration after shooting through both the shoulder blade and a rib. I’ll readily admit I don’t know the intricate details of buffalo anatomy, but I have to believe that a cape buffalo’s shoulder blade is tougher to shoot through than a water buffalo’s hide.
I’m also not sure about the efficiency you mentioned. Using the same type of comparisons as above in this thread, I could easily make a case that my grandfather’s setup was more efficient than mine.
His recurve pulled 42# @ 26”. He shot swagged aluminum arrows with 3-blade 125-grain cut-on-impact heads. His arrows weighed about 460 grains and they flew around 160-170 fps. My 56# @ 32” recurve shoots 500-grain carbons tipped with 125-grain cut-on-impact 2-blade heads at 200 fps.
Since we both do (or used to, in his case) routinely shoot completely through whitetails, does that mean his setup was more efficient than mine (despite my heavier arrows, higher Ke and momentum, higher FOC, and 2-blade heads)? No. It means we both have/had enough to do the job.
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Well when you tote a 1100 grain arrow and 90# compound you are carrying a sledge hammer to do a job that the Doc showed can be accomplished with the framing hammer!
Dead is dead and 1100 grain arrows could stop a freight train. BUT the point is that a longbow which was lighter #/less efficient with optimized arrows achieved the same results. Not sure the longbow was more efficient or less efficient than the wheelie or not but it used every bit of what power it had efficiently. Pretty strong point/backing for the arrow studies.
Agree dead is dead, no one argueing that, but I know I am not shooting a 90 pound bow accurately/hence it is nice to know I could utilize the studies to achieve this same result. I know I am not going over 65/70 on my curve (prefer 55!) and be accurate.
Neat info to be had,
J
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J-dog wrote: Well when you tote a 1100 grain arrow and 90# compound you are carrying a sledge hammer to do a job that the Doc showed can be accomplished with the framing hammer!
Fair enough, so long as you don’t hit the shoulder blade. In that case, we know the sledge hammer will still work. But the framing hammer?
Dead is dead and 1100 grain arrows could stop a freight train. BUT the point is that a longbow which was lighter #/less efficient with optimized arrows achieved the same results.
That was my point as well: they both achieved the same results (barring impact with the shoulder blade), just like both my grandfather’s setup and mine achieved the same results. But that’s not exactly the same as saying his was more efficient. Until we get to the level where one or the other fails to achieve complete penetration, we haven’t tested their limits. So we don’t have enough data to draw that conclusion.
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Unless I’m reading this wrong, I think what the Doc is saying is that with the longbow test arrow setup, the broadhead completely exited the off side on all shots. With Pat’s compound, only one shot completely pushed the broadhead out the other side. If that’s the case, it would seem the lighter penetration maximized arrow made a difference.
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