I felt compelled to compose this missive this after receiving a weekly "tech tip" from an archery only web-site containing the prominent statement:
"Shooting a heavier arrow (shaft + tip) will not necessarily give you more penetration (kinetic energy) over a lighter arrow. Check it for yourself ... take your bow and shoot a heavy arrow and a light arrow through a chronograph, then calculate the kinetic energy. I bet the values aren't much different."
In deference to those espousing (and being led to believe) such an all encompassing statement related to a complex sub-set (archery) in the science of ballistics, I would submit that so much sales hype circulates in the archery market touting arrow speed and really very little discussion time is spent on what I have come to believe is the more critical topic of reliably, humanly dispatching game. After all, the vast majority of shekels spent in the archery industry today are dedicated to deer hunting. Shouldn't that really be the central issue and not just lauding the ability to launch arrows to 60 yards and beyond? Being able to hit a target at range accurately is important; however, if the pursuit revolves around the ethical killing of game, hitting accurately and killing reliably are not necessarily one and the same topic.
Please bear with me if you've heard all this before.
An arrow's penetration (or lack thereof) is based on a number of variables.
The current rage in archery advertisement centers on velocity. From a simple calculation using an arrow's weight and it's velocity at impact, a number, kinetic energy (k.e.) as commonly measured in foot pounds, can be obtained. Basing conclusions about an arrow's ability to penetrate solely upon velocity, k.e. or a combination of both can be misleading and even cruel. If one were to base their decision on using a particular arrow set up based solely upon k.e., he is missing large parts of the arrow penetration equation.
Killing with an arrow has little to do with actual energy transferred to the target (as is commonly found in the firearms industry). If one stops to think about it, were the arrow to actually drop all of its retained energy into the target at point of impact, the arrow would not penetrate at all (as in the case of a small game "blunt" type arrow). An arrow actually performs better when less of its retained energy is shed in the target and penetration is affected by the slicing action provided by a well designed broadhead that maintains its shape and sharpness while performing its duties of destroying the vital circulatory and/or respiratory systems.
Two of the most overlooked factors in arrow choice for maximizing penetration are inertia and friction imparted to the arrow combination as it passes through a given target.. Inertia is a body's propensity to maintain speed and direction based primarily upon its mass. Yes, it takes more energy to start a massive projectile moving but it also requires more effort to change its direction or to stop that travel. In other words: We absolutely want that broadhead to penetrate as far as possible into and beyond (if possible) the target. The arrow's "impact" has little or nothing to do with its intended purpose.
More massive projectiles may or may not strike with more kinetic energy but they tend to retain more of their initial velocity while in flight and during encounters with the target.
Friction related penetration is also affected by:
1. Diameter of the shaft (smaller shaft diameter equals less surface area drag and resistance while inside the target thus greater penetration)
2. Number and angle of cutting edges of broadhead (i.e. a more gradual angle to the cutting edge provides less resistance and better penetration, two cutting edges require less energy to penetrate than three edges, three edges require less than four edges)
3. Smooth transition from broadhead ferrule to arrow shaft promotes penetration (a larger ferrule with smaller O. D. shaft penetrates better than same sized shaft and ferrule while a larger shaft than ferrule penetrates more poorly than either of the above)
4. Stiffer shaft penetrates better than a more flexible shaft (less energy is consumed in shaft flexing and increased lateral friction after impact and more energy is retained for forward movement)
Of course, taking any one of the above factors outlined above to an extreme (i.e. very heavy shaft but too slow to even find the target) does our goal of successfully harvesting game no good.
My admonition to everyone is to be aware of the decisions you are making when choosing an arrow/bow combination. Be careful to filter the advertising propaganda possibly spread by the counter salesperson and television/magazine/catalog ads from the physics of what you actually need to do. There is no free lunch and the current focus on speed and kinetic energy as the end-all be-all to our archery problems is short sighted. While desirable for the 3-D course, that intense commercial focus on speed alone has actually produced a dramatically increased level of struck and wounded game escaping because of inadequate penetration. Merely being able to hit our target is insufficient if we can not reliably bring our intended quarry to ground in an ethical and humanely quick fashion.
Not to put too fine a point on it (all puns aside) but the broadhead needs to make it all the way through those vitals and hopefully out the other side producing a wound channel that allows maximum loss of vital fluids and/or gasses. On deer that can be reliably done at 200 feet per second at 20 yards with a sharp broadhead and a reasonably stiff, heavy arrow every time the mark is hit.
Hitting a foam target is not the same as hitting one of God's creatures.
I hope this gives some food for thought.
This was my test... I'm a believer in a heavy arrow :thumbsup:
http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=120616
Well said. Now would you say momentum and inertia are the same?
Are there not a multitude of such studies? Even Dr Asby's missives have info relating to this.
Konrad...I doff the camo cap to you for providing some solid rationale behind your concerns. I "get it" that cutting ability is really what we're after, rather than what the military calls "a kinetic event." Assuming a sharp broadhead and a good hit on unobstructed vitals, I believe that either a fast, light arrow or a slow, heavy arrow will kill efficiently.
What about when there is a need (albeit inadvertent) to punch through a shoulder blade or solid chunk of rib? How does the mass vs speed discussion factor in then?
Kingsnake
Go back to the first page and go down to Ashby Report. He helps makeyour point with broadhead tests. Good on you
Chris M,
I believe that for the purposes of this discussion the terms, while not precisely the same, are virtually interchangeable.
Wikipedia says: "In common usage the term "inertia" may refer to an object's "amount of resistance to change in velocity" (which is quantified by its mass), or sometimes to its momentum, depending on the context."
Kingsnake,
I would much prefer folks err on the side of a more massive projectile, particularly if they are using a compound bow with sights as their launch platform and may be tempted to push their "circle of death" much beyond 30 yards. Then, if they encounter the odd bone or less than perfect shot execution, there will be enough retained enrergy and velocity to completely penetrate the target. The lighter/faster crowd seems well able to ignore the fact that bad and/or unexpected things sometimes happen in the field (i.e. bone structures).
It has been well documented that the heavier shaft not only retains its velocity better than the light shaft at extended range but its mass (inertia/momentum) better allows for penetration of bone.
Dr. Ashby further expounds on the issue of bone penetration with tests proving the single bevel, two edge, tanto point broadhead has distinct advantages in this regard.
QuoteThe lighter/faster crowd seems well able to ignore the fact that bad and/or unexpected things sometimes happen in the field (i.e. bone structures).
Yes, bad things happen. But it's been my experience that the more accurately people shoot the less often those bad things happen. Get it sharp, get it flying straight, get it where it belongs. The rest is mostly fluff, and if a person actually believes a few extra grains of arrow weight or the number of bevels on their broadheads will turn a bad hit into a humane kill, well, for the animal's sake I hope they're right.
Penetration is largely influenced by shot placement. Of course, a heavier arrow with a sharp BH will do better than the opposite.
It may be implied that each arrow set up is tuned well - yet this is brought not often enough. Arrows which hit 'dead on' - not at an angle due to poor tuning, wind, etc - will possibly be the greatest factor influencing penetration.
my 2 cents
mg
Interesting thread. I'm looking for what arrow and arrow weight shoot best out of my particular bow. The better the arrow flight the better I shoot. I do appreciate what your saying. But since going traditional my "killing radius" is no where near 30 yards. I'm rarely shooting over 15. So far this year Ive killed 3 deer and 2 have been complete pass thrus and one penetrated up to the fletching on the the entrance side. My arrow is approx. 10 grn per pound. Im happy with my results and know my limitations. Great thread. Definate food for thought.
PENETRATION ENHANCING FACTORS IN ORDER OF IMPORTANCE
1.Structural Integrity ----- - from BH tip and edge strength to nock
---------------------------------- tiny tip bend results in an average penetration loss of 14%
2. Arrow Flight- the 'ENABLER' permits other factors to work at full efficiency
-- Poor arrow flight squanders arrow force
-- Even with every other factor in place, w/o good arrow flight you'll still have poor arrow performance
3. Extreme FOC ( >19%) - 1st notable gains are manifested at levels >19%
-- Normal FOC - < 12%
-- High FOC - >12 % to 19%
-- Extreme FOC- > 19% to <30%
--Ultra EFOC >30% - EFOC contributes to a 40% to a 60% increase in penetration having most of the enhancing features
-Ultra-EFOC is (Study defined) as being 30% and above. The reason being, it's really difficult to reach 30% and above FOC without making a concentrated effort to attain FOC.
4.Mechanical Advantage - BH MA ranks this high because it has a more pronounced influence on the outcome penetration of a perfectly flying and structurally sound arrow
5.Shaft Dia & ferrule Dia - 10% penetration gain when shaft dia is 5% smaller than the BH ferrule dia - Aver penetration decrease of 30% when shaft dia > BH ferrule dia
- 40% difference in tissue penetration when comparing a favorable ratio to one w/unfavorable ratio
6. Arrow Mass- Greater mass increases bow efficiency, absorbing more of the bow's energy when fired. That means more arrow force.
- Arrow's tissue penetration is directly proportional to its momentum
7. Edge Finish - A smooth, beard shaving sharp honed & stropped edge works best
- 26% advantage over smoothly filed sharp edge
- 60% advantage over serrated edges
8. Shaft Profile - Tapered shafts show 8% penetration advantage over parallel shafts and 15% over barrel-tapered shafts
- Parallel shafts show 7% advantage over barrel-tapered shafts
9. BH/Arrow Silhouette - Rough & irregular surfaces increase arrow drag in all tissues and is more pronounced during bone penetration
10.Type of Edge Bevel- Single bevel – No down-side to using single bevel BH on any type hit
11. Tip Design - Tips design greatest importance on shots impacting bone. Tonto Tip demonstrates 27.5% better over 2nd best performer(round).
12. Arrow mass(wt) above the heavy bone threshold - this factor jumps to very near the head of all factors, excepting only structural integrity & perhaps fight arrow quality
- Bone impacts of one type or another occur on most hits, and bad hits can occur at any time the threshold is at, or very near 650 grains
13. Arrow force derived from the bow -substantial gain in arrow force from your bow requires either obtaining a more efficient bow or increasing draw wt penetration gains obtainable by increasing draw wt pales in comparison to that achieved through better arrow design
ARROW LETHATLITY DEPENDS PRIMARILY ON PENETRATION
None of those 13 mean anything if you can't put it where it belongs. With very few exceptions, accuracy trumps everything on that list.
Thanks for posting Friend! Very interesting, what are the sources of this information?
Jason, I'm sure that Friend agrees that if you miss your target these 13 factors won't matter, I think he was just describing the factors that ENHANCE ARROW PENETRATION, such as the title of his post states. Whether you can hit the target or not is a different thread.
QuoteOriginally posted by Friend:
5.Shaft Dia & ferrule Dia - 10% penetration gain when shaft dia is 5% smaller than the BH ferrule dia - Aver penetration decrease of 30% when shaft dia > BH ferrule dia
- 40% difference in tissue penetration when comparing a favorable ratio to one w/unfavorable ratio
The one time this does not apply hardly at all is when using 3 blades. I have spoken to a few people about the VPA terminators when paired with an 11/32nd shaft. I have been told that because the 3 blade cuts a hole in whatever it hits (bone included) one can use shafting that is larger than the ferrule diameter as the 3 blades create a hole large enough to completely eliminate shaft drag.
FarmerMarley,
Is accuracy a different thread? Not when the factors being discussed here affect accuracy. How many "I missed another one" threads do we see on message boards every season? Too many.
Velocity being equal, the following factors will add the MOST:
-Perfect arrow flight. I hear Jason and others, but... An arrow that hits the mark but slamming in sideways might mean a single lung hit, or a glance off a rib, rather than a pass-thru).
-Mass
-Sharpness
Paul,
I agree with you 100% about arrow tuning -- get it flying straight. That's why I always cringe when I see people tell others to just screw a heavier head on their arrow to get more FOC. Bad advice to throw tuning out the window just to make your calculator spit out a number over 20%.
I'm gonna agree with Matt, Jason and Paul on this one. Arrow tuning/flight is CRITICAL to accuracy, especially with broadheads.
I'm not going to discount shot placement, but in Konrad's initial post, I think it can be assumed that the "hit" is the same. We get a bunch of posts about arrow penetration and rarely is arrow flight mentioned as one of the variables, but nothing will kill penetration quicker than a crooked flying arrow. No amount of weight and FOC will make up for a sideways arrow.
Quotenothing will kill penetration quicker than a crooked flying arrow. No amount of weight and FOC will make up for a sideways arrow.
That about sums it up right there, everything else is debateable, this is not!
Eric
Perhaps I was not clear enough in my first post (my wife accuses me of this quite frequently) but I was writing from a position of accepting that everything else (tuning, etc.) was correct in the comparisons.
Perhaps I take too much for granted but I was looking at things assuming an apples-to-apples comparison (everything else being equal/perfect).
I apologize if that was not originally made clear.
In addition I will also add that I disagree regarding the statement that "everything else is debatable".
The information contained in the original post was not hypothetical but empirical data.
Like someone once said, "It is what it is..."
FarmerMarley...
The substantiated information posted is a summary of Dr. Ashby's study's on Arrow lethality.
Dr. Ashby has his own forum w/i the Trag Gang Site.
QuoteOriginally posted by Konrad:
Perhaps I was not clear enough in my first post (my wife accuses me of this quite frequently) but I was writing from a position of accepting that everything else (tuning, etc.) was correct in the comparisons.
Perhaps I take too much for granted but I was looking at things assuming an apples-to-apples comparison (everything else being equal/perfect).
I apologize if that was not originally made clear.
In addition I will also add that I disagree regarding the statement that "everything else is debatable".
The information contained in the original post was not hypothetical but empirical data.
Like someone once said, "It is what it is..."
I always assume that most prefer an accurate arrow and realize the importance of a tuned one also.I think you explained yourself just fine.
QuoteOriginally posted by Friend:
FarmerMarley...
The substantiated information posted is a summary of Dr. Ashby's study's on Arrow lethality.
Dr. Ashby has his own forum w/i the Trag Gang Site.
Thanks Friend, I will have to check that out, sounds very interesting and useful.
FarmerMarley,also,if you go to Tuffhead's site,there are some audios of Doc Ashby speaking at Kzoo,explaining some of the points.
By subscribing to the Traditional Bowhunting Magazine's web-site (free & no spam) you can read all of Dr. Ashby's fine and detailed work. They also sponsor a forum dedicated to traditional bowhunting open for comments.
They also have a fine print magazine that you have probably seen on store shelves.