For all you KE people out there...

[O.L. Adcock]

Oh you BB stackers!    Thanks for your service by the way. Only 20 years? I had to be quiter too thanks to slick Willie after 25!

Works like this: Stored energy = limb energy + string energy + arrow energy

That equation must remain ballanced cause you can neither create nor destroy energy. If I increase the mass of say the string, the numbers for the other two MUST go down, and they do. So no matter how heavy the arrow goes, the energy wasted by the limbs/string continue to go down. Now you can get the arrow so heavy we no longer have the ability to measure the tiny changes in arrow velocity, but that's way over 20gr/lb and over practical usage.

Those are not graphs based on theory, actual measurements by Norb Mullaney but it also matches the theory which is nice. Remember that in KE velocity is squared, it's also squared for the wasted energy in the string and limbs. The limbs only move about 1/5th as far as the arrow so they only have about 1/5th the velocity. If anyone  ever sees a situation where the KE does drop in the heavier arrows, that's a clue something else is wrong like nock fit or severe riser contact due to poor tuning. You red shirts, even drawing pictures don't help!    Good on you bud....O.L.

[O.L. Adcock]

To put arrow weight and velocity into further perspective, if our bows were 100% efficient and you went from a 250gr arrow to a 500, you'd lose 25% of your velocity. Go from 500 to 1000 and you lose another 25%. So going from a 250gr and increase your arrow weight 400%, you'd only lose 50% of your velocity. Because they aren't 100% they don't follow those numbers exactly but close. Keep in mind arrow velocity is like RPM to an engine, it depends on the load and doesn't cross directly to horsepower without knowing the load....O.L.

[Dr. Ed Ashby]

Or ... note that the increase in arrow FORCE (the momentum) has a near-linear relationship with the increase in arrow mass. It's more analogous to the 'break horsepower'; the force output 'where the rubber meets the road'.      

Ed
TGMM Family of the Bow

[Tilzbow]

My, my we've gone into a deep, scientific discussion that requires way more concentration than I can muster late on a Friday night after a week of the same at work. OL and Dr. Ed are on a roll and I've got to read this when I get up tomorrow morning and I'm fresh so I can comprehend what they're writing since it's very interesting!

[shakeyslim]

hmmmmmmmmmmmmmmmmm didn't this get discussed by a guy named newton? and if i'm not mistaken you can pretty well take his word as LAW on this point

[chrisg]

sure but was he an archer? This is why I loved science and then going out and finding that it actually does describe the world.
chrisg

[Ragnarok Forge]

I have to agree that Newton nailed it down firmly.  A body in motion tends to stay in motion.  A heavy bond in motion tends to stay in motion longer than a light body when they meet equal resistance, even if the light body is moving faster.  

I have to say DR Ashby and O.L. Adcock have this one pretty well figured out.

If you are planning to hunt buffalo, give up the whole fast arrow idea.  Get your arrow weight up above 650 grains.  Optimize all the other factors and crank your FOC above 20% and preferably closer to 30%.  This usually means keeping your shots at 30 yards and less due to arrow drop past 30 yards.    

Shoot a really high KE arrow out of a compound into a buffallo and you will often find your arrow broken and a pissed buffallo looking for the cause of his pain. Shoot a high momentum of impulse arrow into the same buffallo and your going to have meat on the ground.