Momentum V.S. Kinetic Energy

[easternhunter]

I sent this link to Stilllearnin' for information....not trying to convert him or anyone else here. (but Momentum ROCKS! )JUST KIDDING!
Anyways...in our discussion which get pretty deep on this subject alot of questions pop up. I think it's worth the read. Again just for reference information only so we can understand a bit better the issues at hand. www.booneman.com/_terminalarrow.php

One of my biggest questions is about the downrange effectiveness of these separate setups. Which setup will lose the ability to penetrate sooner? The light weight arrow or the heavier rig. Am I correct in suggesting that Momentum and K.E. need to be calculated at the downrange impact site since this is where the tires actually meet the road.? Do SL and Doegirl need to shoot exactly the same broadhead? I think so to keep an even playing field also. Since I'm currently shooting 600gr. arrows/broadhead combos, I'm very curious about this. Should be alot of fun to help SL. with this.

[BT]

Jan 15, 2009 10:17:30 GMT -5 easternhunter said:

One of my biggest questions is about the downrange effectiveness of these separate setups. Which setup will lose the ability to penetrate sooner? The light weight arrow or the heavier rig. Am I correct in suggesting that Momentum and K.E. need to be calculated at the downrange impact site since this is where the tires actually meet the road.?

There is no doubt that the heavier arrow will indeed have the greater potential at long ranges.
But....eastern zone whitetail hunting rarely ever involves ranges of that distance.
That said...whitetails exists nearly everywhere.

Do SL and Doegirl need to shoot exactly the same broadhead? I think so to keep an even playing field also.

No
This is a K.E. V.S. MO. test and Ashbys theory and BT's theory do not mesh at all, other than to be compared to a loose weave in relation to the broadhead design, excluding weight.

While penetration is a consideration for any rig, total performance is a very real consideration that needs to be taken into account.
This is why I said that the thread being compiled over the course of one year will reveal many things on both sides of the discussion.
For instance....
3-D which replicates field range errors.....how much with each bow effect the outcome?.
Will the K.E. bow be harder to handle and effect score or will the momentum bow effect score with it's wider arc?.

Penetration at varying distances....
Will there be a larger percentage gain overall with the momentum or just on one side of the coin?.
Will the K.E. bow outperform/match at close ranges?

The BT theory holds that a total K.E. system allows for a near zero penetration loss within the flat flight of the arrow and diminishing returns as the arrow leaves that area.
It also allows for lower percentage errors (drop) within the flat flight area and beyond.
The total system effects a 37 - 40 yard flat flight trajectory (3" window) with 70# K.E..
Of course this is only possible with bows that are 60#@28" (minimum) and have a true IBO ability for 350+
The BT theory also olds that the broadhead and arrow flight is crucial and are the only things that are required to be considered beyond FPS.
The Theory lists head diameter minimums based on design of that head and also on the K.E. total of the bow.

The system that Stilllearning will receive will maximize penetration with a minimum diameter and double ratio broadhead.
The recommended head thread (listed within this site) recommends that a head such as the 85gr. Stinger be used.
This head does weight 10gr. more than I would like but it also has a perfect profile.
(I will begin looking for a perfect head later in the year.)

Anyway.... ;D

[BT]

The internet is spazing today...it's a huge pain to post!.
But...I did read what was written on that site and I will go back and address some of the points....with that said....Ashby and BT are only off 50gr. in their theoretical set ups at 357f.p.s.

[BT]

To gain an understanding of this body of work, one must understand some of the principles of physics behind the study. Dr. Ashby does a good job explaining these principles in the following excerpts from his 1996 research paper entitled “Broadhead Performance”:

I remember this bit...my wife left the house!....I was freaking out! ;D

In the terms of physics, all broadheads are classes as a "simple machine". As such, all broadheads are no more than a series of inclined planes. The mechanical advantage (M.A.) of a "simple machine" is the ratio of the resistance to the effort.

What Ashby failed to consider was that although on the face this statement was factual (duh..) Ashby viewed a broadhead based on the mathematical outcome and as being two dimensional
Ashby recently realized his mistake in doing so...ala the bacon skinner blade
But it is so much more than that and although (perhaps) he may now be looking closer at the broadheads effect on penetration, he has not written in an educated manor on this subject

The mechanical advantage of an inclined plane is equal to the length of the plane divided by the height of the plane. A single blade broadhead, with a straight taper, 1" wide by 3" long can be viewed as 2 inclined planes, each of which has a mechanical advantage of 6.0 (3" divided by 1/2"). The mechanical advantage of the two planes combined would be 3.0 because the height would be doubled while the length remains the same. What this means is that with an exerted force (effort) of 1 pound, a weight of 3 pounds can be lifted from the tip of the broadhead to the back edge of the broadhead. The higher the M.A. the more work a broadhead can do with the force available.

As I just finished pointing out....Ashby is not a mathematical expert by any stretch
Ashby fails to consider the resistance or drag effected by the run of the blade.
As I have pointed out before, the ratio (at some point) becomes a detriment to penetration.
This doesn't take whole lot of thought
To make a point by extreme example, take a 1/1 ratio and a 1/100 ratio.
What will go through a given medium with the least resistance?.
Is this example insane?...no....it is extreme but is a factual example of drag being a greater inhibitor to penetration/force than ratio.
Now with that said, there is a ratio extreme to the lesser and the greater and it has been my finding that although the 2.5 is near perfect, the 2.25 may well be the finest of all.
(Note that the majority of superior expandables carry this ratio as well as the finest broadheads such as the Nightmare)
But there is even more that Ashby has over looked.
Ratio as it applies to protection of the edge.
He addresses it (since the inclusion of his liking to the bacon skinner) but he doesn't address anything beyond that or before that

To determine the mechanical advantage of any broadhead with a straight taper to the cutting edge, divide the length of the one cutting blade by 1/2 the width of the broadhead (or, more precisely, the distance from the central axis of the arrow to the highest point on the plane) multiplied by the number of blades. In an equation this would be expressed as:

M.A. = Length of cutting edge / (1/2 width of head) X (number of blades)

Example #1

As stated above, a single blade broadhead 3" long by 1" wide has a mechanical advantage of 3.0. If that same head has three blades, the M.A. would be 2.0, ie: (3" length/.5" lift distance X 3 blades). If it had four blades, the M.A. would be 1.5, or one half that of the single blade.

Ashby and I are together on this....hy wouldn't we be?....pretty simple mathematical calculation here
But...
Ashby stops here....becasue he doesn't know (well...he does since I wrote a piece based on the scimitar head) enough to go on speaking to the ratio of design

I find Ashby to be dry and boring reading....not a whole lot of discoveries being made since Africa

____________

The above was stated on that site and Ashby has since realized that he was incorrect....As I had said then and have been saying since.
Ashby has a much better handle on the broadhead today but still has not completely realized the total effect as of this date
To point to his latest revision would be to point to his findings that a single bevel head is superior to a double bevel as it relates to strength.
Strength saves the edge....which as you all know....I have said forever is of the utmost importance.
Anyway....
Ashby never took into account the front to back guage differential, leading edge taper and much much more
As I said...Ashby wings it most of the time and publishes what can be sold based on mathematical formula.
Ashby was contracted based on his internal medical expertise and not his knowledge of mathematics or their practical application in relation to archery
Many of his past and present statements shine a spot light on this fact.
If I backed up into my theory as much as this guy, nobody would take me seriously ......ever

I'm not saying he doesn't know what he is talking about...not at all
What I am saying is that Ashby is generally ahead of some and behind others....like the rest of us.
The only difference is that his fan base is much larger ;D

I have written a truck load on the subject myself and probably will write it all over again in this thread but right now......I gotta go take my meds ;D

[easternhunter]

Did I strike a nerve BT???
You bring up some interesting points. I think the final outcome may be inconclusive since there are just too many variables involved to reach a definitive answer on all this. How do you compare the performance of one setup against the other without maintaining some sort of control base? and how do you keep that control base constant?

I agree it seems that most or all of his findings are based on his trips to Africa. But at least he tried to incorporate various game species to cover the variations of size, hide thickness and toughness.

I must admit that alot of this is too deep for me too.

[BT]

Jan 15, 2009 13:50:47 GMT -5 easternhunter said:

Did I strike a nerve BT???

LOL!~Yeah....I have been defending my strong and unwavering position for 20 years while Ashby has been edging his way over to me ....all the while saying that I am wrong....until he says that I am right.
(Of course ....it isn't that I will be right....Ashby will be right. )

You bring up some interesting points. I think the final outcome may be inconclusive since there are just too many variables involved to reach a definitive answer on all this....
How do you compare the performance of one setup against the other without maintaining some sort of control base? and how do you keep that control base constant?

I don't agree in as much as there are two very distinct sides to this coin.
Doegirl and Stilllearning are both following the recommendations set forth by each party, so the end results are going to represent each school of thought.
I do believe that both rigs will do the job and that both will have very real Pro's as well as Con's.

This thread (hopefully) will be viewed as an entire table, filled to the edges and to the ceiling with food for thought.

I definitely will defend my contentions as will Ashby...because we both find that our theory's work.
That said....do they work for everyone?

[easternhunter]

Not trying to raise yer hackles BT..LOL In the end it's comes down to individual preference anyhow. That's where Bruce and I leave it anyways, cuz if we don't one of us would take a hurtin' real bad!
Where's Greg stand on all this???
Look forward to all this anyways! MAybe we'll all learn somethin'.

[BT]

I am going to stop right here with my pissin and moanin because this is not what I want this thread to turn into.
What I want to see is two people experiencing something that they have never experienced before and then telling us ll what they perceive the Pro's and Con's to be.

I got my hackles all brushed back down now Eastern ..... Dont you be mussin 'em up again!
;D

[easternhunter]

Jan 15, 2009 18:55:16 GMT -5 BT said:

I am going to stop right here with my pissin and moanin because this is not what I want this thread to turn into.
What I want to see is two people experiencing something that they have never experienced before and then telling us ll what they perceive the Pro's and Con's to be.

I got my hackles all brushed back down now Eastern ..... Dont you be mussin 'em up again!
;D

:PLOL

[royden]

why stop??? it was getting interesting ...