Trad Gang

Topic Archives => Classics => Topic started by: Dr. Ed Ashby on March 27, 2003, 07:48:00 PM

Title: "The Study" - need YOUR ideas NOW!
Post by: Dr. Ed Ashby on March 27, 2003, 07:48:00 PM
Hello all,

Please put on your collective thinking caps.  Most of the study data base work and protocols are done.  I'm developing an "idea and questions" list now.  This is a sort-of 'wish list' of things we would like to know about hunting arrow performance on real animals.

So far, I have about a page and a half of typed questions I want to look for the answers to, but I wish to "pick the collective brains" of the dedicated hunters of the Trad Gang.

I don't want to list all I have - 'cause it would just confuse the issue - too much to think about.  I'll just give a couple of examples from the list, and then I'd like for ya'll to just think about things YOU would like to have answers to - besides the performance levels of the different broadheads being tested.  So ... here are a few examples of some I already have on the list.

(1)  A look at the relationship of IMPACT kinetic energy and momentum as predictors of penetration, with arrows of equal 'broadhead design and structural integrity'.

(2)  The effect of the 'Moment of Force' on penetration.  A comparison of 'similar' arrows with EQUAL IMPACT FORCE, but with one having greater mass at lower velocity, and the other having lower mass at a greater velocity.  How important is the 'rate of disipation of force' as a factor in penetration?

(3)  Is there any quantifiable difference in the degree of blood trails that can be related to type of broadhead/cut width/number of blades/sharpening angle/broadhead cut blade profile(s)/type of edge sharpening method used.

(4)  What effect, if any, does the percentage of weight FOC have on penetration when all else is equal.

Ok, now, ya'll give me ALL you can think of!  :readit:

Lets try to keep this post 'at the top of the list' until I've milked everyone of EVERY IDEA ya'll can come up with.  If I need to add any 'data collection' items, I need them NOW ... BEFORE the study formally commences.

Ed
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: paradocs on March 27, 2003, 08:27:00 PM
Ferrule diameter vs shaft diameter, as it relates to penetration?
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Douglas DuRant on March 27, 2003, 08:31:00 PM
The effect of the “speed of impact”, if any, on the penetration achieved by a broadhead. Ron Le Clair showed a picture of a shoulder blade penetrated by a light carbon arrow in a thread a while back. If I understand him, he thinks you don't need high weight with fast light carbons to get good penetration. Stiffness, frequencies of modulation (is that real), small diameter are all things I have heard stated as reasons carbon arrows seem to penetrate well.

Consideration of the arrow concerning penetration seems as important as the broadhead, which rides the shaft. Factors such as arrow diameter, speed, weight, material, foc, are all potentially important to penetration.

The arrows path through the animal, with bones on impact, and exit, full stomachs ect being considered.

Repeatable bow energy, arrow speed, and draw length data. Accurate arrow spine, length and weights measurements are also important.

Distance, angle, elevation, and alertness of the animal at the shot are also relivent factors to consider.

From what I have seen you seem to have considered all these things already. I think some more on it, and if I come up with something I'll add it later. Good Idea asking, you never know what someone will think of.
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Ray Lyon on March 27, 2003, 08:35:00 PM
How does shaft material affect penetration, if at all, with other factors being equal.

Is there a corelation between number of blades on a broadhead and the length of blood trail do to the "shock" to the animals system of more blades.(Initial thoughts would be more blades, shorter trail because of quicker blood loss, but my memory seems to say otherwise with my personal experiences).
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Van/TX on March 27, 2003, 08:58:00 PM
Dr. Ed, I remember reading your study in the late 1980's.  You are so far ahead of most folks I'll just take at face value what ever you come up with.  You're a good'un.  Thanks!  :cool:
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Dr. Ed Ashby on March 27, 2003, 09:05:00 PM
Paradocs ... Douglas ... got 'ya covered on those.  Keep them heads working!  I'm sort of isolated here, and really need a 'sounding board'.

Ray ...  Have shaft materials in there.  Also degree of blood trails as related to type of hit, presence/absence of exit wounds and their location(s), type(s) of broadhead, number of blades, blade profiles (several parameters), total cut area of the broadhead (an am considering adding 'cut volumn' - any thoughts here?), edge sharpening angle, edge sharpening technique, and 'alert level' of the animal to the shot.  Any more?

Ed
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: herb haines on March 27, 2003, 09:33:00 PM
Dr. Ed ,
this might not even have any bearing on any thing but what about angle of hit and distance traveled .
    what i am wondering is from what i have read that a shot from a tree stand with exit low down on body would bleed out better than a a shot from the ground with a through and through shot .don't know how clear i am on this ,hate treestands ,hunt from the ground wondering which is better .----- herb  :confused:
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Dr. Ed Ashby on March 27, 2003, 09:41:00 PM
Herb,

It's in there!  Keep up the thoughs though.  I REALLY do appreciate everyone taking time to think about these things.  I hope to have a data base that I can keep going even after 'phase one' of the study is completed, hoping that factors which are 'indeterminate' can be cleared up as the data continues to accumulate.  I want the information collected to be as 'complete' as I can get it.  This 'input' of other bowhunters really helps me out!

Ed
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: paradocs on March 27, 2003, 09:44:00 PM
Hmmm, how 'bout moving vs stationary target, mud-encrusted hide vs "clean" hide, male vs female within the same species, wet vs dry fletching(assuming feathers from a well-tuned setup), all in relation to penetration?  I'm sure I'll come up with some more; just give me a few more beers.  ;)
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Kevin Lawler on March 27, 2003, 09:48:00 PM
I think you got yourself 2 studies there. I for one would like to see an independent study on the camparison of penetration of different shaft materials and a thesis on why one out pentrates the other.
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Buckeye on March 27, 2003, 09:50:00 PM
I would like to see the shaft material test go even a bit further in specifics. In other words same broadhead (weight, design) on equal weight arrows of carbon alum. and wood. Seems there has been more than a bit of speculation the last few years as to whether carbons in fact out penetrate other arrows. I remember your original study did speak to diameter of shaft as it related to the ferule/broadhead ferule diameter. At least it figured into the TPI. I would be interested in that test result. Thanks

B
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Buckeye on March 27, 2003, 09:53:00 PM
Sorry bout the cross post Kevin!
B
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Dr. Ed Ashby on March 27, 2003, 10:00:00 PM
Paradocs ... are there any breweries near where you aree?  If so, most have 'hospitality rooms'.  Great place for 'thunk'n'.   :scared:    :scared:    Thinking of naming it MOABS (Mother Of All Broadhead Studies - any name suggestions for the study out there?) Have had to divide the data bases up into three 9so far) and cross-link 'um, 'cause it got too big to work with!

As for shaft materials, I hope to be able to answer the 'what' part, but the 'why' will just be my speculation of why I THINK the results show what they do!

Ed
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Dr. Ed Ashby on March 27, 2003, 10:02:00 PM
Buckeye ... that is exactly what I intend to do, but it will only come after what broadhead to use is determined.

Ed
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: JRW on March 27, 2003, 10:42:00 PM
Please also break down some of the data by brand/model of broadhead. Not all 2, 3, or 4 blades are created equal.

Thanks, in advance.

JRW
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Russ on March 27, 2003, 10:52:00 PM
Dr. Ashby, Thank you for the opportunity to provide input. As already mentioned, carbon arrow penetration as related to total arrow weight and compared to other shaft materials. Carbon arrow penetration as related to added nock weight. Lots of nock weight or weight tubes may, theoretically, take away the alledged carbon benefit of lack of noodling on impact. I assume the critters down under are smaller than Africa's and I'd like to see data on penetration with lighter bows. I hunt, in my old age, with 55-65# bows. What arrow combinations work well in this weight range on deer, caribou, moose and such? How does one compensate for these relatively light bow weights and what is it's importance on thin-skinned North American big game? Lastly, I'm fascinated by your previous findings that penetration is more important than shot placement and would like to see it addressed again in this new study. Thansk again and I look forward to the new study!
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Russ on March 27, 2003, 11:59:00 PM
Forgot to mention front loaded carbons. It seems to be all the craze right now. Does it work?
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Dr. Ed Ashby on March 28, 2003, 12:09:00 AM
JRW ... consider it done!

Russ ... All the data this time will be related to the force at impact (I'll revisit the Kinetic Energy vs Momentum argument first, to see which I use, but the existing data I have is pretty overwhelming that there is NO consistant correlation between Kinetic Energy and penetration, so it will most likely be momentum.)  This 'impact force' format will allow for one to use their own set-up, a chronograph and one of the 'on line' down range ballistics calculators to get an idea of how their equipment should perform relative to the study's results.  There will be a fair amount of testing done with lighter bows too.  That should help.

The idea that so many hold that only 'big' animals were used in the Natal Study is wrong.  Most of the testing was done on warthogs, impala, bushbucks and nyala - animals VERY consistant in size and structure with the hogs and deer of North America.  It was only as we began to 'push' the broadheads that we couldn't fully evaluate the performance level of on the smaller animals that we moved up to larger animals, those of wildebeeste, kudu and zebra size.

There's plenty of 'big stuff' down under too - feral horses, bantang, scrub bulls, Asian buffalo and camels - so we will, no doubt, end up with some 'push' stuff here too, as the field begins to narrow.

Initial testing will begin with feral goats, pigs and deer.  Only the things that pass the testing at this level unscathed will 'move up' to the next level of testing.  There will be an attempt to segregate or 'rate' the broadheads for the level they perform to.  (Although I never adhered to that theory.  If it's adequate for the largest, then it darned sure is adequate for a smaller critter.  Ain't no such thing as 'over kill' with an arrow.)

There will also be some data collection on North American game, but season and bag limits severely restrict the amount of data that can be collected there.  Aussie has no season or bag limits on the feral animals!  Now that offers the potential for reasonable data collection, but it still pails in comparison to the shooting opportunities of Africa.

Broadhead selection has to be 'weeded out' before I can start to definitively look in the data base for other factors, or do any studies focused on a specific factor, such as the effects on penetration of shaft size relative to shaft diameter.

Hope the information that eventually comes from this study will be of some help to you Russ.

Ed
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Dr. Ed Ashby on March 28, 2003, 12:11:00 AM
Thanks again Russ.  The front-loaded carbon is one I'm anxious to look at too!

Ed
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Russ on March 28, 2003, 04:13:00 AM
Dr. Ashby, I'm sure you are aware of this but thought I'd mention it anyway. There is a theory that carbon arrows do not "noodle" or oscillate wildly upon impact like wood and aluminum arrows. Therefore, carbons are thought to penetrate better than other types of arrows, even though they may be much lighter, because they better maintain their sectional density. It is further theorized that this lack of noodling transcends momentum theories. Weighting the carbon shaft with excessive nock weight, with or without point weight, or weight tubes is thought to interfere with this inherent property and decrease penetration, despite increased arrow weight. I'd love to know if experimentation proves this out. It would change the arrows I hunt with.

Lastly, the momentum versus kinetic energy arguments have always seemed a bit hollow to me. Both equations use mass and velocity and differ only in their mathematical relationships. As I remember from undergraduate school, a thousand years ago, Newton's original solids equation for momentum was changed later by an engineer, for his particular experiments, and remained so. In your Tissue Penetration Index, mass and velocity figures were held subject to arrow shaft diameter relative to broadhead diameter and the mechanical advantage of the broadhead. This relationship seemed to de-emphasize mass and velocity to a large extent, yet you seem intent on studying it further. What is your perspective of all this?
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: AZStickman on March 28, 2003, 11:54:00 AM
I think you have it covered but broadhead length to width ratios as it relates to penetration and blood trails.... and broadhead materials of construction......which will affect proper sharpening and durability......also wouldn't fletching combinations possibly factor in..... 4 fletch v.s 3 fletch and differing fletch lengths..... Terry
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: bob@helleknife.com on March 28, 2003, 02:43:00 PM
Dr. Ashby,

Your study seems so over whelming to me.  So much data, so many variables...with tools designed over 10,000 years ago.  Interesting paradox!

Digressing a tad.  The holy grail of current archery thought is two holes are better than one.  Seems I have read that some early American archery pioneers felt that it was best if the arrow stayed in the animal and allowed to "work" as the critter fled.  Wonder how they came to that conclusion?  Perhaps they talked to some native Americans and that information was conveyed to them?

I wonder if there is any correlation between recovery or ease of recovery of animals on pass through shots vs. arrows that stayed in the animal.

Warmest regards.

bob@helleknife.com
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Dr. Ed Ashby on March 28, 2003, 05:39:00 PM
Russ ... somewhere, further along in the study, I hope to do a lot of "look'n" at arrow shafts as a factor, not only by type of material, but by FOC and by profile (straight, tapered, double tapered).

These 'individual factor' studies will have to be very 'focused', where all remains constant except for the varable being looked at, and a lot of shots have to be taken with each 'parameter' to get a valid result.  That means they are well down the road in the study, so don't be looking for that answer to drop out too soon - but I hope to get there, Lord willing, and the creek don't rise.  I too, hope to find the 'shaft answers', and, if I do, it could well change the arrow I hunt with too!

By the very definition, momentum is the correct formula for penetration.  It is the straight line force vector of a body in motion which must be met by an equal amount of resistance before a body in motion comes to rest.  Kinetic Energy is the entirity of energy of a body in motion and, for an arrow in flight, would include such things as the flexional energy, the sound energy, the rotational energy, and the heat energy, as well as the directional force vectors.

The reason for the "re-visit" is that so many still subscribe to, and rely upon, kinetic energy readings as an indicator of the arrow's 'potential'.  In some locations it is even used as the legal 'benchmark' for hunting set-ups to be legal for certain classes of game.

This dispute needs to be settled.  All the data I have so far indicates that Kinetic Energy should not be used as an indicator for penetration.  In all the studies I've done so far, it has no "significant' correlation at all.  The hope is that the case can be made so overwhelming that absolutely no question can remain, and we can all move on to the more important issue, coming up with something that really is valid.

Now, as momentum is the correct formula for straight line energy vs resistance, and assuming it does prove to have a sufficient level of correlation to penetration in this study, it will be used as the 'starting point', the 'impact force' (and 'impact force' is only A PART of what is needed for a final 'model').

The next phase will be to analize the resistance factors.  This is where the 'noodling' factor will enter, as will shaft drag, shaft size vs ferrule diameter, mechanical advantage of the broadheads, cut resistance, etcetera.  The 'changed momentum formula' you refer to is not really a 'change',it is a modeling - looking at the 'moment of momentum', the vairable force applied over the time period of action of a body in motion before it comes to rest.

The moment of momentum is one factor I hope to look at - the effect of like arrows of equal mumentum, but where one has higher mass and lower velocity and the other lower mass at higher velocity.  As the mass remains a constant throughout the penetration, the heavier arrow will have a longer 'moment' of force - therefore it will act 'longer' but, as it is moving slower, just how far will it be able to travel in that 'extra time of action"?  Which will go farther before expending all the energy and coming to rest against tissues of "X" amount of intrensic resistance?  Conventional wisdom says the heavier one will, but is that correct?  Could this be a factor in the reported 'carbon arrow penetration paradox'?  I have no idea yet!

Using the basic definition of momentum from physics, it is clear that all the factors influencing the resistance being met have to be delineated in order to come up with a predictable penetration factor.

If it can be varified that momentum is the correct 'starting point', and the other factors can then be 'quantified' somehow, it should be possible to develope an 'arrow profile formula' that should give a very close correlation to actual measured penetration under field condition.  This was what the TPI was about, and it appeared to have a very close correlation in it's one and only test so far done.  That test, however, was way to limited to be certain that it was correct.  Much, much, more needs to be done towards development of a relaible model.

Bob ... One of the many things being looked at this time will be the types of correlations between shot locations, penetration, exits and non-exits and the degree of lethality (recovery rates, distance traveled before collapse, degrees of blood trails, and a host of other factors).  The question you raise of an arrow remaining in and continuing to cut is one that has lingered long, and it must be look at critically.

After hanging around a lot of hunt camps for lots of years, one of the things I'm absolutely certain of is that a 'body hit' animal that runs off with the arrow still in it is much more likely to be the 'lost animal' than one that has a 'body hit' pass-through shot.  The question remains, "Why"?  Was it broadhead failure?  Inadequate penetration?  (These two often go 'ahnd in hand'.)  This continuing occurrance of a higher frequency of 'lost with the arrow in it' makes me wonder how valid the 'continues to do damage' theory is.

Yet another factor that enters into this 'remaining in' issue is that the Indians used stone points, which often shatter inside the animal, making multiple secondary missiles.  What is their effect?  From all the bullet wound dissections I've done over the years (which VASTLY outnumber all the arrow shots I ever even seen, or even heard about, might less dissected), I think it is more likely that it is these secondary missiles that do the damage, rather than a factor of the arrow remaining in and continuing to cut.

We WILL be doing some testing with stone points during this study.  The individual tasked with this portion of the study is an experienced hunter with stone points, and he has already brough up the subject of the damage done as the point shatters.  That shattering is the 'norm' not the exception, and would creat numerous secondary wound channels, and a 'cone of destruction' similar to an expanding rifle bullet.  He is also an experienced rifle hunter, and describes some stone point shot animals dropping "as though hit by a bullet".  Interesting stuff, huh?

AZStickman ... got 'ya covered on ALL those!

Thanks Russ, Bob, Stick ... your doing a great job.  I need these 'brain rattlers' just to keep me aware of where we are and where we're trying to get to with the studies.

Ed
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Kevin Bahr on March 28, 2003, 09:16:00 PM
Well, Dr. Ashby, since hairs are being split, how about broadhead blade to nock alignment, any angle better than others as far as penetration goes?  And one big one that always seems to get stuck in my craw, how about some professional arguments on why one should not use mechanical broadheads.  THanks in advance.  Kevin Bahr
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Kevin Bahr on March 28, 2003, 09:19:00 PM
Just kidding on my first question Doctor.  But serious on the second.  I have had bad experiences with open on impact heads shot by others and I need some professional, scientific study-backed reasons to quote when speaking about them to others.  Thanks again.  K. Bahr
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Dr. Ed Ashby on March 28, 2003, 10:06:00 PM
Hi Kevin,

Best never to take anything for granted!

I HAVE looked at broadhead to nock alignment pretty extensively, and the answer is ... it makes no differance at all.  Now, I didn't look at it out of curosity, I did it so that there WOULD BE hard data to verify what was obvious from the outset.

The arrow rotates in flight, so we really have no choice in the orientation of broadhead impact angle.  Also, the torque is too low for the arrow to continue rotation once tissue is entered.  The wound channel will show no change in orientation of the head's impact position from entrance to exit UNLESS it is deviated by impact with a heavy tissue, such as bone  (This, by the way, is another 'plus' for the single blade broadheads.  When they hit rib(s) they frequently glance off and turn to pass between the rids, thus conserving their energy for deeper penetration into the underlying soft tissues.)

Mechanicals WILL be in the testing - several different ones will be extensively tested.

Thanks - it's not always bad to 'split hairs'.  Often it's the fastest way to get answers ... by getting to the 'roots' of problems ... just to prove it really was only a good 'color job' all along!

Ed
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: bayoulongbowman on March 30, 2003, 06:42:00 PM
Dr. Ed , How about the sharpness of the broadhead isnt that one of most important and cutting on impact..maybe parallel to taper shat could develope more Kenitic Energy if its matched with the LBs . of the bow correctly...TY mark
Title: Re: "The Study" - need YOUR ideas NOW!
Post by: Dr. Ed Ashby on March 30, 2003, 09:01:00 PM
bayoulongbowman - Thanks for the post.  'Edge' is one of the factors that I'll be tracking, both the angle it is sharpened at and the type of edge sharpening finish technique used.  I hope to try cross-correlation to a number of factors (if there proves to be ANY correlation), penetration, edge durability, percentage of exits, degree of blood trail, etcetera.

Some initial 'overall durability' testing will be done, using the manufacturer's edge angle.  This is to forestall any criticism that the head(s) might have performed better if used 'as intended' by the manufacturer.

Will also be tracking type of shaft, by both material (includung, for woods, the specific wood type) and by shaft profile (parallel, tapered, double tapered).

Thanks, and KEEP THINKING!

Ed