Now the Kinetic II got me to thinking about what they would do downrange so I punched them in and this is what I come up with.


To have the right foc and spine the Kinetic 400 would weigh in at 460 grains.



speed distance ke
238 fps 0 yards 57.9
220 fps 50 yards 49.5


The ke at 50 yards with the kinetic II is 2.2 ft/lb more ke than the 2214 at 450 grains.If I make the weight equal the difference become 1.7 ft/lb ke at 50 yards.


That gives the the kinetic a definate advantage over the aluminum.

Oh yea,it is also 3 fps faster at 50 yards than the aluminum.Doesn't really matter but just thought I would add it.


This is not my actuall hunting set up.My draw weight will be increased for hunting.

Edited by - tfox on 08/15/2002 19:49:53

I have been involved in many of these discussions. I will say this. There are many misconceptions about penetration and what causes it. I don't want to make this harder than it has to be.

Kinetic energy: 1/2*m*v^2. This as a term used to quantify the energy carried by a mass in motion.

Momentum: m*v this is a vector quantity. In other words a number is not momentum unless it has a direction. Momentum and energy are two different things.

Let's consider a hypothetical situation. Let's first make some simple assumptions. We have a number of arrows that weigh differently. Some are light and some are heavy. Now we use any broadhead but we use the same broadhead on all arrows. Now remember we have different arrows of different weight and diameter. We shoot each of these arrows out of different bows but have them set up to generate the same kinetic energy. If this is the case, the smaller arrows will pentrate deeper. Now I know everyone is pulling their hair out and cursing at there computer and saying I am a complete idiot and have no concept of physics. Let me explain before you argue that the "world is not round".

This is a case of simple fluid dynamics. We can consider a particle moving through a fluid the same as an arrow (particle) moving through tissue (fluid). With this in mind, the only mathematical tool we have in relating velocity ( ultimately Kinetic energy) and penetration would be an energy balance. Without spending the money and time ( chemical engineering degreee ) this energy balance concept is foreign. Just trust me when I say that only 4 things can affect the particles (arrow) penetration. These are Kineetic energy, potential energy, work, and friction. Now we know that the arrow is not doing any work (no pumps, turbines, motors, etc.). Potential energy can also be neglected (potential energy would be energy stored up by a change in height). So that only leaves friction and KE. Now if the Kinetic energy values are all the same, the arrow with the least amount of friction against the tissue will penetrate further. Assuming that the smaller diameter arrow has the least friction with the tissue due to reduced surface area then viola....the smaller arrow will penetrate further.

To explain why momentum and KE are not both related to penetration would take up a small book. They are related much like velocity and accelartion. Both are affected by velocity but do affect physical actions the same.

So, Kinetic energy is the only valid choice to quantify penetration. No it is not the only factor. Arrow placement, broadhead design, KE, all play a role.

I hopes this helps.

Bucskin, if momentum is not related to penetration, then why does an arrow continue in a certain direction when it contacts an animal? Why doesn't it take a random zigzaging course through the animal? Why does the arrow penetrate at all? SOMETHING allows the arrow to penetrate in a fairly straight line through the animal instead of the arrow simply expending all it's energy on the animal's hide and falling to the ground. The only something I know of that would do that is momentum.

Momentum is a form of inertia that allows an object, for our purposes an arrow, to resist changing it's current direction and speed.

Buckskin

I tend to agree to a point with equal ke arrows that the one with the least amount of friction will do best.But you seem to forget that an arrow is a long object that needs to be stabilized and if the foc is too low then when it hits an object the arrow will just flip forward.If a small arrow had an foc at 5 % it isn't going anywhere.



Another problem with equall ke is it isn't possible for most to achieve this with their bow.


I am still going to stick with the notion that momentum is what bust through the bone instead of bouncing around like a ping pong ball.

We can all agree that a light arrow is easier too move off course than a heavy one.


This may be of some help to penetrate through a deer when you bounce around a bone instead of thru it but on a large animal when you have to get thru a bone,I would still like to have some momentum.

It is all necessary but the amounts of what is in question.



Look here Arthur,we actually agree on something.<img src=icon_smile_wink.gif border=0 align=middle>

Yep, TFOX. It's about time. <img src=icon_smile_wink.gif border=0 align=middle>

I also agree that how much momentum you need depends on whether you hit bone or slide through flesh. I prefer to bust thru bone if I mess up instead of hoping the arrow slides around it, so that's why I like my logs for hunting. 99% of the time, I don't hit heavy bone. But there's still that 1% chance lurking around out there that I know would sneak up and bite me in the arse if I used something lighter.

I could use a 400 grain arrow and still get the same amount of momentum as I get with my 2315's @ 220 fps but I'd have to jack that 400 grainer up to around 340 fps for some 103 ft lbs of energy to do it. I don't think I could get quite that much out of my round wheeled 60 pound bow. Not even at my gorilla draw length. <img src=icon_smile_big.gif border=0 align=middle>

Arthur


I really don't think you should worry about anything with that much draw length.


The stored energy in your bow should just about take care of anything you should happen to shoot.Light or heavy arrow.Light to you is 400 gr and that is on the heavy side for me.<img src=icon_smile_shock.gif border=0 align=middle>

Heavy!?! LOL!

Even setting the prongs of my rest just behind the riser so I can cut my arrows to 31 1/2&quot; long, using 4&quot; feathers and 100 gn tips (so I can get a decent FOC) my GoldTips still weighed in at 420 grains. PSE Dominators were about the same. Beman ICSH's were even heavier. I can't get any lighter without going to a full blown overdraw!

See? Even when I try going light, I'm still accused of shooting a heavy arrow. So... If my arrows are going to be heavy anyway, might as well be REALLY heavy.

Did I ever tell you about the time I went from 2216's to 2213's on an overdraw bow and wound up with a lot more arrow drop with the lighter 2213's? The gap between my 20 and 30 pins tightened up but the gaps between 30-40, 40-50 and 50-60 opened up. Measuring from my 20 pin to my 60 pin, it was just under an inch with 2216's and just over 1 1/4&quot; with 2213's. Strangely enough, I got flatter long range trajectory with the heavier arrows.

Arthur,
Want a heavy arrow? Why not buy a fiberglass bowfishing arrow and use that. Should get somewhere around 1500 grains raw shaft <img src=icon_smile_big.gif border=0 align=middle>

Good discussion gents.
Can't wait to see Buckskins view on momentium

Greg

&quot;Getting close to the game is the joy of Bowhunting for me, the harvest is a bonus.&quot;

Live 15 ft Python after eating a small Antelope!

Arthur 31.5 inch arrows? Try my 33&quot; arrows. I believe that we both have the same draw length of 33&quot;. But, I like my arrows to go beyond my knuckes.

TFox, I would agree that for you it may be hard to get an extra 300 grain and the correct spined arrow if you, especially if you didn't move to an aluminum. It would also have to do with the lentgh of your arrow. An extra 300 grain for me was easy since I went from a 3d select carbon (32.5&quot with a 75 grain point to a 33&quot; aluminum 2613 XX78 with a 187 grain point (with adapter). The FOC on my carbon was a bit light, but the 75 grain Muzzy was the only head that I could get to fly right,the Aluminum FOC is just right around 12%. For me, I really enjoy shooting the heavier arrow.

TheArcheryProgram, thanks for all you expert help. BTW I tried to get to your website through your profile and it didn't work for some reason.

Edited by - BobCo19-65 on 08/16/2002 08:25:41

It would seem to me, that regardless of the KE or the momentum, a very important aspect would be an arrow that is flying a straight as possible. Any fish tailing or wobble would result in energy being wasted because of drastically increased friction. Therefore, if someone wants to really maximize their penetration potential, they should tune their bow, so it shoots the arrow as straight as possible.

It occurs to me, that any changes made to FOC, draw weight, arrow weight, etc. would be detrimental unless it results in a more perfect arrow flight. If a person is &quot;shooting darts&quot; with their current set-up, I'd hesistate recommending any change, just to increase KE, momentum or any other physical parameter. If they do decide to increase or decrease arrow weight, or draw weight, then they should be prepared to work at getting that perfect flight again, and it's not always that easy to do.