Archery Mechanics

[michihunter]

There has been a discussion going on in the review of Hoosieroutdoorsmans new Storm bow that I feel is worthy of it's own topic. The basic question lies in whether or not a bow that is shooting slower speeds, with less KE and momentum can penetrate harder and farther with the same arrow as another bow. Is it possible with the mechanics of the bow itself? I truly am unsure but feel that logically speaking, the bow is not the reason for the discrepancy. I think that once an arrow is released, the initial chrono of that arrow is the peak speed, KE, and such and that the only way there could be a difference in impact is due to an energy loss somewhere in the arrow itself./ Here's a link to some interesting articles on the topic. Pay particular attention to the topic entitled Draw Force Curve homepage.ntlworld.com/joetapley/ And here's a link to some very controversial articles written by renowned archer/hunter Dr. Ashby www.tradgang.com/ashby/

[hoosieroutdoorsman]

This is a good post Michi,,one I am sure we will both wear our fingers out on,,lol. Ok now with everything Michi has said and the articles he has posted which are great articles I might add. To truly ( IMHO ) break down the power of the bow you would have to forget the IBO,KE, Arrow weight. You would have to break the bow itself down into groups and run each part through a test or tests. Take the limbs,,say bow A has a really stiff set of limbs and bow B has a softer more limber set of limbs. Which one irregardless of speed KE arrow weight etc. would actually put the most energy into the string to fire off the arrow? Oh so we can rule out eccentrics and their let off and curve radius lets say these bows both have round wheels at top and bottom.

[michihunter]

The quicker moving limb will generate more energy therefore resulting in more energy transfer. Think of it as a spring. The tighter the spring the quicker it will retract. But I think you may be actually asking efficiency which could certainly be different. A slower moving spring through time and less force will transfer more of it's overall energy due to less energy loss through heat, friction, and such.

So the answer is both!! The tighter limb transfers more energy yet the slower more limber limb will transfer it more efficiently.

[hoosieroutdoorsman]

A tighter limb won`t always be quicker,,it depends on just how STIFF that limb is,,the same as the limber limb,,if too limber it will be a dud,, but with the right spine a limber limb can produce more energy than a stiff limb. Kind of like a bungy cord compared to cottom cord. The stiffer limb if pulled downward more than the even the properly spined limber limb would in fact beat it by over 30%,,,finding the right amount of movement in conjunction with the spine of the limb is the key,,the same with a bow string,,the string has to be elastic but not too elastic. That has always been the biggest brain pain for me is how the guys building these bows can get everything down to the micro in tolerance to achieve the performance they do. And you will find some that prefer a stiff limb and some prefer a limber limb,,yet both can achieve nearly the same results?? I guess that is what an education will actually do for you,,lol.

[hoosieroutdoorsman]

Hey Michi,,have you done any searching on Carbon Composite Bow limbs? I know High Country uses them but haven`t been able to find anything on the actual design and building of them. I know you do a ton of research on the web maybe you had found something?

[michihunter]

Actually I think you may be referring to HCA's composite RISERS.

[hoosieroutdoorsman]

Nope,,HCA also has Carbon Limbs,,they call them Vibra-Flex Armour. I had talked with a HCA rep and he said it was military grade carbon,,totally independant of affects of extreme heat,extreme cold, etc. He said that that is why they developed the Carbon Revolution Speed Max Pro arrows, they avg 5.5-6.5 GPI. He said while the majority of bow manufacturers will warranty arrows no lighter 5 grains per pound of draw HCA with the carbon construction will warranty down to 3 grains per pound of draw. Now here is something I think YOU will appreciate,, I did some numbers with their 5.5 GPI and figured in a speed of 320 fps,, and the KE was low. They may have developed a bow and a arrow that will flat smoke when used together but the kinetic energy is too low. I could take a 240 fps bow with a 5.5 grains per pound of draw arrow weight and smoke their high speed set up on KE. They brag on the carbon revolution arrow chart that they get better penetration? I would have to see that to believe it. A 29 inch CR arrow with 100 grain tip with a 320 speed will produce 67 Ft.Lb of KE
A 400 grain arrow same length and tip weight will produce the same KE at 275 fps. To me I can`t see the extra money is gaining anything? The carbon may be good for shooting lower GPP but is it really gaining anything positive?

[michihunter]

As you already know, I couldn't agree more!! ;D ;D