Trad Gang

Topic Archives => Classics => Topic started by: Terry Green on March 29, 2003, 05:21:00 PM

Title: Physics Wizzard's...Riddle me this?
Post by: Terry Green on March 29, 2003, 05:21:00 PM
Been wondering about this for quite some time.

OK, I'll try my best to make it clear as possible.

2 arrows identical, same everything....EXCEPT the weight displacement.

One 600 grain arrow total weight including the 125 grain broadhead.

One 600 grain arrow total weight including the 225 grain broadhead.

Both arrows weigh the same 600 grains, and have the same broadhead measurements, but the weight displacement is different.

Which arrow will penetrate best?  Or, will they penetrate the same?

Will the arrow with more mass in the head penetrate less than the arrow with more mass BEHIND the head pushing as it meets resistance?

Kick it around.  I know its really not THAT important, but I would like to hear what you guys think.  And, its one question I haven't really seen a definite answer on.  Been meaning to do a test, but never really got around to it.
Title: Re: Physics Wizzard's...Riddle me this?
Post by: **DONOTDELETE** on March 29, 2003, 05:30:00 PM
Terry,
I just got my brother registered here on his pc and was showing him around.  I've tried the scenarios you presented out to 25 yards and found the arrow with the heavier up-front weight outpenetrated the arrows that weighed the same but had the 125 grain head.  My tests were only used on carbons and still haven't tested these past 25 yards so more tests will be needed.  Not sure why this happens??

Joe Subler on brother's pc
Title: Re: Physics Wizzard's...Riddle me this?
Post by: runswithskunks on March 29, 2003, 06:11:00 PM
I'm no physics wizard.    :smileystooges:

However, it is my observation that higher FOCs seem to have better flight -- they are just disadvantaged by higher tragectory flights.   So that might be one for you.

I don't see how the static distribution of the weight would substantially affect penetration -- 600 grains is 600 grains, and the whole setup is rigid.  If there were some significant flex involved, I think it would come into play a little.

rws
Title: Re: Physics Wizzard's...Riddle me this?
Post by: Dr. Ed Ashby on March 29, 2003, 06:13:00 PM
Oh, you just love to do this Terry, don't you!   :confused:    :confused:  

As the impact momentum would be identical, and the laws of conservation of energy must be applied, IF there is a difference in penetration, it could only result from a vairable in the resistance factors affecting each arrow's passage.  That would result in a longer moment of momentum for one of the arrows, allowing it to act for a longer period of time in the resistance medium, and thus travel a greater distance.

For the time being, I won't get excited about anything that turns up in artificial media test.  So far, I've found "artificial information" on terminal ballistics of little use in "real world" applications (arrows or bullets).

Hope to look at this one ... in a few years.  :readit:  

Ed
Title: Re: Physics Wizzard's...Riddle me this?
Post by: George Tsoukalas on March 29, 2003, 06:35:00 PM
What the Doc said but the problem is 100 gr difference on the head would require the arrow tipped with a heavier bh to have a bit greater spine.
Jawge
Title: Re: Physics Wizzard's...Riddle me this?
Post by: Meathook on March 29, 2003, 07:04:00 PM
I did a non-scientific study    :smileystooges:  


Seriously, My guess is that the difference in penetration is negligable assuming arrow flight is reasonably similar and tajectory equal.  But I  guess thats what the doc said.
Title: Re: Physics Wizzard's...Riddle me this?
Post by: JC on March 29, 2003, 07:13:00 PM
Thinking back to my old college days, I would have to say Jawge hit it closest. If the shaft does not flex, it transfers or "pushes" it's energy in a straighter line. This, if I remember correctly, is the better part of the "pillar effect." The energy is "focused" directly perpindicular to the cross section of the shaft making it more efficient in "pushing" the head through.  I would also think the decreased flex would cause less drag, therefore less heat, therefore less energy lost. Guess I did remember something from GA Tech....

Joe
Title: Re: Physics Wizzard's...Riddle me this?
Post by: runswithskunks on March 29, 2003, 10:14:00 PM
All this talk about flex....what kind of girlie- spined arrows are y'all shootin'?!

  :p  

rws
Title: Re: Physics Wizzard's...Riddle me this?
Post by: Charlie Lamb on March 30, 2003, 12:21:00 AM
This is one of those things that I kinda think I might know or might not know, but it probably doesn't matter anyway!  :D  

I'd have to say that the arrow with the heavy weight forward would have the greatest potential for deepest penetration.
Starting with a stable attitude on impact with target, to a lessoning of "noodling" of the shaft on impact.
Title: Re: Physics Wizzard's...Riddle me this?
Post by: John Nail on March 30, 2003, 07:50:00 PM
cornbread are square, divided by the length of the hippo-noose, times the root-mean-square of the earth's rotation over the moon's reflection=the one with the narrowest, sharpest, head will penetrate farther. However this doesn't mean it will kill quickest.....
Title: Re: Physics Wizzard's...Riddle me this?
Post by: Terry Green on March 30, 2003, 08:04:00 PM
Good answer Mr. Nail   :D
Title: Re: Physics Wizzard's...Riddle me this?
Post by: Ron LaClair on March 31, 2003, 07:53:00 AM
Now I'm totally confused  :confused:  It doesn't matter if I add weight to the front or the rear, I can still push my truck farther than I can pull it.  :knothead:    :D    ;)
Title: Re: Physics Wizzard's...Riddle me this?
Post by: Lee @ Keep It Simple on March 31, 2003, 12:34:00 PM
in rws scenerio...the fletching at both ends probably played into it a significant degree.

The stiffness at impact would be a factor as has been proven in videos that promote the carbon arrows.

I myself put more emphasis on arrow flight.  Quality flight not only improves penetration, but puts that penetration where it is supposed to be...the kill zone.

Great debate has taken place on the balance of arrow flight.  Here is MY opinion...which very well may not be correct, but it is my opinion non-the-less and anyone is free to disagree.

When studying archery I have come to the conclusion and common belief that the arrow is the most important piece of equipment as did many legendary archers.  Howard Hill for example expressed this belief as did I believe Bob Swinhart (spelling?).  Howard studied arrows extensively including arrow flight characteristics, balance, and many other aspects that we often think about such as spine, weight, straightness...etc.  One of the things he expressed concerning balance was a statement that a broadhead should be no more than 145 grains and lighter may even be preferred, but because he used a much heavier head when killing the elephant with that ~2000 grain elephant arrow that was made special for that purpose it is obvious that he made exceptions based on the purpose the arrow was to serve.

There are two factors that go into my mind when I think about broadhead weight.  At impact and during flight I think a heavy head would be good.  The idea of the point dropping surprises me because if the point is heavy, then the nock is light and if the nock is light isn't it going to follow the point?  Surely it would...so there would be an arrow/tradjectory drop, not point drop...but that is perhaps somantics.  Anyway, the other aspect is upon the release of the string...the string pushes the nock.  If the point is heavy, we all know spine needs to go up.  Ask youself why.  It is because the arrow wants to bend as the string pushes the nock.  This push has two effects in my opinion.  One is a commonly known flex of the shaft in which the center flexes in a manner known as paradox.  The other is perhaps less considered but equaly important and that is an attempt for the tip to move out of line of this paradox/thrust in which the nock would then be pushed in a manner not to "pass" the point, but in a slight effect gain on the point in RELATION to the target by going with the path of thrust from the bowstring while the tip would be more likely to go offcourse as the tip becomes heavier.  Therefore, ARROW STABILITY in my opinion has actually 3 different types of stability...1. take off from thrust in which a light point would be best (the faster the bow the more unstable a heavy point would become in take off), 2. flight in which moderate point weight with moderate fletching would be best, and 3. impact in which heavy point would be best...

so you go back te the famous statement..."Robbing Peter to pay Paul."

If you go to an extreme in either light or heavy, it is my belief that you will loose arrow stability at some point in flight.  Therefore moderate weight seems to be the best.  What is moderate now since "light, moderate, and heavy" are all relative terms.  My guess is Howard and other archers already figured this out to be somewhere in the 125-150 grain range depending on how heavy your arrows are to begin with.  At compound speeds this may be too heavy for stability at takeoff/bowstring thrust and you might expect to have to drop to 100 grains of tip weight to be able to travel stable and true at 300 fps.

In closing, let me say I am not getting stabilty at take off/bowstring thrust mixed with spine.  I am talking about stability.  Even a bow that is bareshaft tuned has a degree of sensitivity for this bareshaft to fly true.  I think the best penetration will come from the truest flying arrow that hits the mark.
Title: Re: Physics Wizzard's...Riddle me this?
Post by: Lee @ Keep It Simple on March 31, 2003, 12:40:00 PM
BTW, the reason I say the nock is light in a heavy arrow is because most people that use a VERY heavy point are those that need the weight because of carbon arrows.  For those of you that shoot spear weight (hehehe) arrows made of hardwoods may the feathers don't totally follow the point...like a spear.
Title: Re: Physics Wizzard's...Riddle me this?
Post by: BLACK WOLF on April 01, 2003, 12:28:00 AM
I love these kind of questions Terry!

Here are my 2 cents after thinking about it ;^)

Everything being equal...I would put my money on the heavier head.

What I've noticed is that there are at least 4 major factors for arrow penetration.

1. weight
2. speed
3. arrow diameter
4. arrow recovery (archer's paradox)

You've brought up another idea I haven't considered until now....F.O.C.

Let's exagerate the test by thinking about if the majority of the weight for the other arrow was in the back of the arrow instead of the front. As the arrow penetrates and reaches some resistance, a side to side effect on the arrow could be caused by the arrow hitting a rib. If you hold a stick with a weight at the end of it, it bends side to side more dramatically if you shake it than if you grabbed it by the end with the weight in your hand and shook it, which lends me to believe the arrow with the weight up front will have a better chance of penetrating further when heavy resistance is met.

Does that make any sense to anyone or did I have a brain fart? ;^) Sometimes, I'm not very good at expressing my thoughts into words ;^)

Ray
Title: Re: Physics Wizzard's...Riddle me this?
Post by: Terry Green on August 26, 2008, 02:05:00 PM
Note the date on this one started....

March 9th 2003!!!

A precursor of the FOC studies!!!

Thought it was interesting that it was posted on the 14th day of Trad Gang's birth, and a LOT has been said about it here since.