Are faster bows wounding more deer?

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hunter_mike
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Re: Are faster bows wounding more deer?

Unread postby hunter_mike » Tue Jul 02, 2013 7:23 am

hunter_mike wrote:
Bowhunting Brian wrote:
hunter_mike wrote:
Dhurtubise wrote:
On the other hand a faster bow will obviously produce grater momentum in the same arrow, but how much. When you read the literature on a bow, they use the KE value to quantify their bows. It makes sense because this value should be relatively consistent regardless of your choice of arrow weight. However I think that overall this value is misunderstood, and at least a little misleading for your average hunter.

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This is exactly the concept that really clicked for me and made me realize that momentum is the quantity you want to optimize in your hunting bow rig.

I remember that: Potential Energy = Kinetic Energy - Waste energy from friction & inefficiency

-Potential energy is the energy you induce when you draw your bow back. When you are at full draw you have induced the maximum potential energy your bow can capacitate. This amount of energy is always the same for your particular bow no matter what type of arrow or setup you are using. The only way to increase your potential energy is to increase your draw weight. Potential energy is simply a force time a distance. (60lb draw weight*29 inch draw length) (I realize its more complicated than that because of the draw cycle and let-off)

- The waste energy and friction is basically an amount of energy that is a function dependent on the efficiency of your bow, friction between your arrow rest and arrow and any other energy that is converted into hand shock energy you can feel and sound energy you can hear.

- Kinetic energy is basically whatever energy is leftover after you deduct the wast energy. According to the equation above in blue, this kinetic energy amount will be pretty much the same no matter what type of arrow or projectile you are launching. Obviously in reality it does vary a bit. (you can feel the difference in hand shock when you shoot a big heavy arrow vs. when you dry fire your bow.)

So if kinetic energy is pretty much always constant what do you have control over? MOMENTUM

Momentum = mass*velocity

An arrow with more momentum will have more penetrating power because it will want to keep moving more than an object with less momentum. Therefore it is more resistant to slowing down from air resistance and tissue and bone

Anyone care to take it from here?


I agree. KE is a marketing tool. KE looks better because it is not a decimal number like momentum is. any of todays bows can get the job done. people think the need a high KE or try to change their set-up so they can raise their KE, when in reality, if they want to increase their chance of a pass through, all they have to do it raise the number of grains on their arrow.


Ok. I agree with that except when you increase the mass of your arrow, you are decreasing your velocity too. Therefore ther has to be a certain optimum point where your arrow will be so heavy that it starts to actually decrease your momentum and hurt you. Thats not my opinion, its math and physics. I would like to find that point.


Ok Brian I apologize, I was actually wrong about that. Heres the mathematical relationship of momentum and mass. The big assumption is that your Kinetic energy is constant throughout this curve with is a decent assumption as others have observed.

Image

The curve shows that momentum always increases when mass (of your arrow) increases. However the rate of momentum increase starts to slow way down after a while. You can theoretically get as much momentum as you want, it just depends on how much velocity you want to give up


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Re: Are faster bows wounding more deer?

Unread postby DEERSLAYER » Tue Jul 02, 2013 8:17 am

Uncle Lou wrote:...Now I got to look into that decibel claim on the Strother, that is such a low value it is hard to believe. I suspect a typo or the sound meter is farther away than the standard for that measurement. If it is true, that is an unbelievable breakthrough. Most quiet bows are 80+/- dB. It is also a logarithmic scale which makes it a couple orders of magnitude quieter

Lou,
I would look up the contact info for the author of that report (Rick Combs) and not only ask about the dB's but also let him know why it caught your eye...... because of the business your in. You never know, it may lead to some more exposure for you.
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Re: Are faster bows wounding more deer?

Unread postby hunter_mike » Tue Jul 02, 2013 9:42 am

Image

Another mathematical relationship if you assume KE is constant, which was determined to be a reasonable assumption. As the mass of your arrow approaches zero, your velocity approaches infinity. As your arrow mass approaches infinity, your velocity approaches zero.

The earlier relationship between mass and momentum still holds true.
Image

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Re: Are faster bows wounding more deer?

Unread postby Dhurtubise » Tue Jul 02, 2013 12:36 pm

Great work mike!

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Re: Are faster bows wounding more deer?

Unread postby JoeRE » Wed Jul 03, 2013 4:00 pm

Haha, there is a reason I tried to provide a simple qualitative explanation of KE and momentum a couple pages back. You guys pull that math out and every non-engineer's eyes glaze over! j/k :lol:

Good discussion guys!
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Re: Are faster bows wounding more deer?

Unread postby hunter_mike » Wed Jul 03, 2013 4:06 pm

JoeRE wrote:Haha, there is a reason I tried to provide a simple qualitative explanation of KE and momentum a couple pages back. You guys pull that math out and every non-engineer's eyes glaze over! j/k :lol:

Good discussion though guys!


Haha yeah i didn't mean to kill the post, I was basically thinking out loud. BUT, i do think that the graph's that I drew, representing the math are easy enough for anyone to understand. If they don't look at all the math crap that doesn't make sense and just look at the shape of the curve it explains things that are more difficult to explain with words.
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Re: Are faster bows wounding more deer?

Unread postby Darin » Wed Jul 03, 2013 6:03 pm

Glad to see you guys going to town on this topic! Some of the math looks like Hebrew to me :lol: but as I follow I am picking up on it. Thanks for the input so far
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Re: Are faster bows wounding more deer?

Unread postby ShaftSlinger6 » Mon Sep 30, 2013 3:29 pm

Im fairly new to bow hunting and still trying to 'fine tune' things... Is there such thing as too much arrow weight? I shoot 63lbs at 28' draw. Any thoughts on using a 10.6 gpi arrow? This would put speed around 275 fps as opposed to say an 8.2 gpi arrow at 299 fps. Is it beneficial to go to the 10.6 gpi?
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Re: Are faster bows wounding more deer?

Unread postby DEERSLAYER » Mon Sep 30, 2013 3:43 pm

ShaftSlinger6 wrote:Is there such thing as too much arrow weight? I shoot 63lbs at 28' draw. Any thoughts on using a 10.6 gpi arrow?

I think that would be a good weight. It's only to much if it drops like a lead balloon causing your accuracy to plummet with it.
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Re: Are faster bows wounding more deer?

Unread postby ShaftSlinger6 » Mon Sep 30, 2013 4:03 pm

Makes sense. Just wasnt sure if there was a point to where the trade off wasnt worth it other than decreased accuracy.
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Re: Are faster bows wounding more deer?

Unread postby Stanley » Mon Sep 30, 2013 4:04 pm

ShaftSlinger6 wrote:Im fairly new to bow hunting and still trying to 'fine tune' things... Is there such thing as too much arrow weight? I shoot 63lbs at 28' draw. Any thoughts on using a 10.6 gpi arrow? This would put speed around 275 fps as opposed to say an 8.2 gpi arrow at 299 fps. Is it beneficial to go to the 10.6 gpi?


No, your 20 yard pin will hit at 20 yards with a bow set up to shoot light arrows or a bow that is set up to shoot heavy arrows.
You can fool some of the bucks, all of the time, and fool all of the bucks, some of the time, however you certainly can't fool all of the bucks, all of the time.
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Re: Are faster bows wounding more deer?

Unread postby BassBoysLLP » Tue Oct 01, 2013 1:09 am

ShaftSlinger6 wrote:Im fairly new to bow hunting and still trying to 'fine tune' things... [glow=red]Is there such thing as too much arrow weight?[/glow]I shoot 63lbs at 28' draw. Any thoughts on using a 10.6 gpi arrow? This would put speed around 275 fps as opposed to say an 8.2 gpi arrow at 299 fps. Is it beneficial to go to the 10.6 gpi?


No. As long as you are good judge of range, you will be fine. With today's bows, you won't see much of a difference in trajectory under 30 yards (typical shot on a whitetail) when comparing a light and heavy arrow. In the end, its all about personal preference unless you want to shoot a large expandable broadhead.
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Re: Are faster bows wounding more deer?

Unread postby woody283 » Fri Oct 04, 2013 4:00 pm

I might be a little late for the ballgame, but i am a momentum shooter. Also only shoot trad gear. If i keep my shots under 25 yds, i have no problem putting a group of ceders into a group of much lighter carbons, and you can see the effect of momentum. with my hunting arrows coming in just shy of 700gr, and my 3d carbons at just about 500, I'm getting at least 3/4 inch more penetration with the cedar. And thats not considering the shaft diameter. But i do taper my cedars to about 10% foc. from 5/16 to 11/32 at the head.
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Re: Are faster bows wounding more deer?

Unread postby Chasman » Fri Oct 04, 2013 11:37 pm

Wow pretty heavy stuff. Good stuff though. My take on the issue of wounding deer is that bowhunting is one of the few hunting sports that is gaining new hunters. The combination of inexperience, bogus advertising of too many products, and yes Glamour Hunting shows instills the instant success of bowhunting. And because they spent 3 grand on this stuff they have to kill something, or at least try, so fling away. I had a huge learning curve. Did not shoot a deer for my first 3 years. Shot at one and missed by a mile. Small buck. Can still remember to this day I did not prepare myself for the actually shooting of the deer before that. Super nervous, no confidence in my shooting. Changed that from that day forth.


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