buckskin,

If your theory of friction is true....then why do lighter arrows penetrate "air" worse then then heavy arrows. A light arrow will lose a greater % of its speed than a heavy arrow at equal distances.

If it cannot penetrate "Air" better, Why would it penetrate deer better??

Rack attack,

That is not always true as you can see if you look at my numbers with the lighter arrows.Usually a lighter arrow will be smaller in diameter and will actually hold more speed.This is not always true but is with the ACC verses the 2413.They lost the exact same speed at 50 yards.At 100 yards the ACC lost 1 fps more.


What you are reffering too is drag and air resistance and not friction.Friction is something actually rubbing against an object.

ok. Let me say, this idea of an energy balance and KE is not "my theory". I am not near that intelligent. I can only present the facts. Let me start with the momentum and KE confusion.

KE is again 1/2mv^2. Momentum is m*v. Now in Calculus Momentum is consider a derivative of KE. This means that Momentum is actually a representation of the change in KE. Let me explain. AS KE energy decreases over a distance, say from 20 to 40 yards, then momentum is a rate of change. So as the KE energy changes, the momentum is a reprentation of that change. To say that momentum does not affect penetration is not what I am trying to say. What I am saying is that we have no mathematical way to relate mometnum and penetration directly. KE is the only way to represent the relationship of velocity, arrow wieght and penetration. Just like velocity is related to acceleration......momentum is related to KE. Velocity affects each one but in a different proportion. It is just a matter of how they relate to penetration. And by the way...all this can be proved mathematically. But trust me is sucks!!!!!


Now on the momentum aspect. Yes momentum has everything to do with deflection on bone or hard tissue. Remember momentum is not momentum without direction. As an arrow glances off a bone or breaks the bone, it is transfering momentum to the bone in a particular direction. This is the law of "conservation". Momentum is conserved.....always.!!!!!!! So Yes an arrow carries a certain amount of momentum and that is it. Once that is used up...no more momentum transfer. Also remember that momentum and KE will equal zero at the same time. So they are related.

I don't mean to confuse the matter. It is just that momentum and KE are so closely related the two get confusing some times.

Our best tool for judging penetration is KE. Sorry guys.....scientific principles.....I don't make the rules....I just learned how they are applied.

IF anyone cares this is the energy balance
All these terms actually represent a change between two points.

(v^2)/2 + g(z) + w + F = 0

v=velocity
g=gravity
w=work
F=friction

Verbally this reads

change in Kinetic energy + change in potential energy + work + friction = zero.

<BLOCKQUOTE id=quote<font size=1 face='Verdana, Arial, Helvetica' id=quote>quote:<hr height=1 noshade id=quote>What you are reffering too is drag and air resistance and not friction.Friction is something actually rubbing against an object <hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face='Verdana, Arial, Helvetica' size=2 id=quote>

Isn't drag and air resistance due to the friction of the air. Air is not a vacume, it is a medium. I think those terms are one in the same. Air resistance is due to the friction of air molecules rubbing against the arrow.

I think 99% of the friction is directed onto the broad head and the shaft size, being led through a larger hole from the head plays a very small role in penetration.

I also feel the penetration diff. between heavy and light are so small that in the real world do not change the outcome.

I opt for speed, I can live with loosing a little KE for the flat trajectory.

Its just makes it that much easier for me to pull the arrow out of the dirt.<img src=icon_smile_big.gif border=0 align=middle>

My heavy arrows have never slowed down on a deer either and they've done fine for me for a long, long time.

I understand what you're saying, Buckskin, but you have to also remember that physicists have looked at all the numbers and swear that a bumblebee cannot possibly fly.

Thank God there weren't any physicists 30,000 years ago or our species would still be using sticks to dig up beetle grubs and roots for food instead of using them as projectiles to gather venison steaks. <img src=icon_smile_big.gif border=0 align=middle>

Edited by - Arthur P on 08/16/2002 17:27:22

BobCo-

Just type the address listed into a browser rather than clicking the link. I have built anti-frame grabbing into my webpage bacause some other websites were building it in to theirs! Cant' do that! without my persmission!

The address is www dot thearcheryprogram dot com

Happy Shooting!



>>>------Tony Virnoche------>>>
>>>---The Archery Program--->>>

After reading most of the replys to this subject (one of my favorites), we seem to be focusing on KE and/or momentum. While these are the easiest to use for judging penetraition (well...KE at least) one thing has gone without much mention. Velocity and the ability to cut (penetrate). Fluid dynamics has been mentioned, but there is more. GENERALLY, the faster something is moving, the easier it cuts. You can put a chunk of 100lb test fishing line on the end of a sledge hammer, and you'll have GOBBS of KE...but you won't cut grass untill you get it moving...FAST.
When talking penetration, and what affects it, velocity must be part of the equasion (and in KE it is......but there is more to it than just using KE) When you go from field point to broadheads, velocity plays a MUCH larger roll (field points MOST push matter aside, where blades cut without much movement).
I think it was outdoor life that did tests on like 19 broadheads on 3 different arrows...what everyone guess would happen didn't. The BEST penetration was with an expandable on the LIGHTEST arrow. And arrow diameter was not the differance. they used weighted and non wieghted carbon arrows....non wieghted did better than weighted (both did better MOST of the time than aluminum). And the expandables won out most likely due to the low friction of the blades (not very tall) compared to the HUGE surface area of most fixed blade heads.
I'm NOT saying we all need to buy a Bowtech Black Knight and shoot 80 Lbs w/ 300 gn arrows.....but speed alone DOES affect penetration (same KE but more speed, the faster/lighter arrow wins....with blades, it wins by a lot).

Edited by - Stealth_Force on 08/18/2002 00:33:06

Quite frankly, my opinion of this light arrow, high speed thing is that it was founded in the late 80's/early 90's by people doing their damnedest to justify being cheapskates and hunting with their 3D rigs instead of getting real hunting equipment. (Of course, they are also the ones that ruined 3D by bringing target bows into the game instead of competing with hunting bows, but that's another topic.) Just expressing my opinion based on personal observation. Flame on, if you must.

The thing that worries me about this speed/kinetic energy focus is that a lot of new people can look at the numbers you guys are posting, like 280 fps and 70 fpe, and think they can't hunt with their bows because they can't get anywhere near those numbers with their setups.

Does high speed and a heavy reliance on KE work? Of course it does. But it's only ONE way of skinning this cat. Just like shooting an 800 grain arrow at 150 fps out of a selfbow and relying heavily on momentum. It too is only one way. Both are getting into the realm of expert archers, and neither are even close to the best way for most people. High speed rigs are not the easiest things in the world to shoot accurately, no matter how easy they may seem to YOU. They put demands on shooting form and tuning skills that most people cannot meet. The selfbow makes high demands on the shooter's hunting skills, being able to get very close to the animal and being able to shoot without all the stuff everyone thinks is indespensible nowadays... like sights, release, rangefinder, blah, blah, blah.

In my not-so-humble opinion, everyone between the two extremes would all be better served by moderate performance bows designed with more of an emphasis on forgiveness instead speed, shooting around 7-8 grains per pound with fixed blade broadheads around 220-250 fps. That's all you really need. For traditonal gear, I don't like to see hunting arrows weigh less than 9 grains per pound (and I'm sure to catch heck from some of them, too).




Edited by - Arthur P on 08/18/2002 07:22:07

Stealth force.
I would like to know which month and year of outdoor life the &quot;penetration&quot; test was in. I am interested in doing some testing myself. This test sounds alot like what I am looking for.

I also think your idea of velocity affecting penetration is interesting. You have actually described the energy balance I mentioned in my earlier post. The KE in the energy balance is actually the KE per grain of arrow weight. In other words, the arrow weight doesn't matter, only Velocity^2 on a per mass basis. Now, all you heavy arrows addicts, don't throw your computer across the room. Your heavy arrow might have a per mass KE value close to the per mass value of a lighter arrow. This is why I am saying that KE is a great number that can be used to judge penetration.

Stealthforce


I did mention the speed(velocity) in one of my earlier post.

Speed fights friction much like pushing a steel block across a table,the faster you push the block the less friction and the easier it is to push.


I agree with your post to some degree but when you hit bone it would be nice to have some momentum built up for busting through it.

I agree with Arthur that a moderate weight arrow is best for most but my moderate and his moderate weight are different.


I like what the AMO has set up for minimums.IT IS NOT 6 GR PER POUND.It is different for everyone.I stay at the lower end for whitetail but would go up a little on larger game.There is a list of the AMO minimums at www.bowjackson.com



I actually never had a passthru on a deer untill I went to carbon and expandables.Since then, all have been passthru's.GO figure.