I really think we would find that each cam design, bow weight, draw length combo has a particular weight arrow at which effeciency peaks or is at it's best, and could give us some skewed numbers we are not used to.

Usually more weight equals more KE, but those numbers with modern Bow design are slight. A sweet spot in arrow weight and Voila numbers we are not used to.

My thoughts are that even arrow material could play a part in energy absorbed from the Bow?? My 400 grain arrows are the new Aramid Kevlar shafts.

I doubt any contact is the issue on my setup with feathers and a Limb Driver.

340 grain arrow less KE

400 grain best KE

500 grain arrow slightly less KE

I sure would not give up the speed differencethere is between a 400 and a 500 grain arrow for even a slight gain in KE and I actually lost a tad

Numbers from My Guardian 60# 28" draw

326 grain arrow 280 fps 56.77# KE

500 grain arrow 232 fps 59.77# KE

Difference of 3# KE

Numbers from my General 60# 28" draw

326 grain arrow 278 fps 55.96# KE

500 grain arrow 228 fps 57.73# KE

Difference of only 1.77# KE

On the Guardian and General I never shot the 400 grain arrow. Maybe I should!!

Dan

I certainly didn't forget efficiency, in fact in my very first post I explained that the reason heavier arrows carry more ke than lighter arrows is precisely because bows shoot heavier arrows more efficiently than lighter ones. Here's the quote...

"Going to a heavier arrow ALWAYS results in an increase in both momentum and kinetic energy. The reason for this is that,upon release,stored potential energy in the limbs is transferred more efficiently to the kinetic energy of arrows of greater mass than of lower mass. That's just fundamental mechanics and the rule can't be violated."

Heavier arrows absorb more of the stored potential energy in the limbsand the ratio of energy absorbed/energy storedis the definition of efficiency. That is the rule that can't be violated. It's ALWAYS true. If test results indicate otherwise than something is amiss or something unaccounted for is going on. If the only change is to increase arrow mass then ke and momentum will ALWAYS increase.

Oh and by the way, it is impossible to increase the ke without increasing momentum and vice versa by only making one change e.g. arrow mass or bow weight or draw length etc.

For years many independent testing facilities have measured and publishedefficiency data on bows shooting an array of arrows from very light to very heavy.Data is available on litereally hundreds of bows from recurves to the most exotic of cam designs. You can go to the news stand any time and pick up a copy of Bowhunter magazine who publishes such data every month. In not one single case on literally thousands of measurements has efficiency been shown to fall back when arrow mass increased. In every every single case efficiency and ke increased as arrow mass increased. There is no sweet spot regarding arrow mass and ke. As you go lighter and lighter the bow shoots the arrow less and less efficiently wasting more and more energy in vibration and noise. This effect will continue to worsen as you go lighter and lighter all the way down to dry firing the bow.

Was there ever a test done with the kevlar arrows?

Again,I agree with you and have never seen this happen without a reason,it is usually in the tune.But,I have never tested kevlar arrows and if an arrow can absorb more energy,then it makes sense it will produce better ke.


(Oh and by the way, it is impossible to increase the ke without increasing momentum and vice versa by only making one change e.g. arrow mass or bow weight or draw length etc.) AGREED

I was referring to the momentum being higher with the lighter arrow.It wouldn't be.

But,if indeed the 400 gr arrow has a higher ke value than the 500 grain arrow,the momentum could still be higher with the 500 grain arrow than the 400 even if the ke was higher on the lighter arrow.Regardless of what caused the discrepancy.

I think that's right but I'll have to ponder it a bit...

DOn't know about the kevlar arrows.

I think Momentum is over rated. What are we actually trying to shoot through. Armour Plating? There are many things that play a bigger part in penetration than momentum.

That's another subject and I won't argue the point. You can argue until the End of time while I'll stillbe Blowing through everything I shoot. There are So MANY thing that determine penetration capabilities of a setup there is No way to discuss it on a forum with any good outcome.

My Airborne produces slightly more KE with a 400 grain arrow than it does a 500 grain arrow.
That's a fact!! Like, Believe it or not. Your thoughts or beliefs won't change a thing.

It's a known fact that some Cam/Bow designs seem toprefer or perform better with light or heavyarrow setups. I am not a Gung Ho light arrow guy nor am I a Gung Ho Heavy arrow guy. I have setups ranging in weight from 326 grains all the way to 500 grains.

They all have one thing in common. They work, and I'll guarantee you they'll all Blow through anything I hunt on North America, but when I find a setup that shoots as effeciently as my Aramids are shooting out of my 82 you can bet I'll stick with them

Dan

Dan,
I will agree with you to some extent, I think there's some value in momentum, but even though a 800gr arrow travelling at 168fps will carry moremomentum than my 440 @ 270'ish FPS, I'm still opting for the 440ish because I like a "little" speed along with my KE.A 440-470 gr arrow is about where my either of my 2 bows are going to be getting the maximum efficiency as far as KE goes.

I think we all chase speed a little, but the compromise between is probably what is in the overall realm best for our bows.

I'm not arguing there is not more momentum with a heavier arrow. I just said IMO it's over rated

Your shooting a 70# bow. Me a 60#er.

You say your best overall arrow weight seems to be 440-470 grains and mine is 400ish grains.

Sounds about right to me

Dan

If you calculate the numbers on the arrows that I posted you can see that my numbers agree with MeanV's findings. All three arrows were shot three times eachthrough the same chronograph, out of the same bow, at the same draw length, at the same draw weight.

For poops and giggles I just shot a 397 grain arrow too.

397 grain arrow... 315 fps ......... 87# KE
443 grain arrow...302 fps ......... 90# KE
502 grain arrow...283 fps ......... 89# KE
625 grain arrow... 256 fps ......... 91# KE

Aparantly the 82nd, and probably the 101st, are less efficient with certain weight arrows.

Very interesting. I only hope that 435 grains is close to that sweet spot.

Alright, this is going to be hard for me to explain because I do not have a lot experience in testing arrow masses and their efficiency, but I'll do my best. Is it possible that the marginal gain in KE peaks. Think about it. Look at the following HYPOTHETICAL data:

365 grain arrow — 1# KE — _ Marginal KE
370 grain arrow — 2# KE — 1 Marginal KE
375 grain arrow — 3# KE — 1 Marginal KE
380 grain arrow — 4# KE — 1 Marginal KE
385 grain arrow — 6# KE — 2 Marginal KE
390 grain arrow — 8# KE — 2 Marginal KE
395 grain arrow — 10# KE — 2 Marginal KE
400 grain arrow — 13# KE — 3 Marginal KE
405 grain arrow — 16# KE — 3 Marginal KE
410 grain arrow — 19# KE — 3 Marginal KE
415 grain arrow — 23# KE — 4 Marginal KE
420 grain arrow — 27# KE — 4 Marginal KE
425 grain arrow — 31# KE — 4 Marginal KE
430 grain arrow — 35# KE — 4 Marginal KE
435 grain arrow — 40# KE — 5 Marginal KE*
440 grain arrow — 44# KE — 4 Marginal KE
445 grain arrow — 48# KE — 4 Marginal KE
450 grain arrow — 52# KE — 4 Marginal KE

It's like combining economics and physics into one very complicated question.