To heck with KE formulas and theories

[Cougar Mag]

This just isn't simple anymore and it gives me a headache. Back when bows were 50% to 60% letoff(a couple were 40%) and shooting fingers, at 65-67 lbs. I was shooting right around a 540 grain arrow.......2216's to be exact. I even dabbled a couple of seasons with 2219's at 70 lbs., till I figured out that 70 lbs. was just a tad too much for me when it got cold. When I started shooting a release. I still hunted with a heavy aluminum arrow. I blew through deer with no problem, but admittedly the arrow would not shoot as flat at longer distances.

KE was not even talked about then, at least not that I can remember. Certainly the correct arrow spine and weight most certainly was, along with FOC. I remember going to lighter arrows.....2213s for 3D shoots and eventually wound up using them for hunting. Next I used carbons, nearly the same weight but with a stiffer spine for hunting. And although I still killed my share of whitetail deer, I did notice a difference in penetration on not pinpoint hits and in fact even a passthrough on double lung hits were not quite as impressive.

I guess what I am getting at is this. Using the KE formulas, charts, etc. it doesn't work for me. I get better penetration, consistency and accuracy with heavier arrows shooting the same poundage, using the correct spine, and although the lighter arrows produce more fps( and in general according to the charts and KE formulas more KE..........well). It just doesn't work for me. For example I prefer an FOC of around 10%. Using a chart and more importantly to me is doing the balancing act at home on a level desk or table.......going heavier in broadhead weight along with the stiffer spine/heavier weight arrow does work for me. I am not talking about ultraheavy or over spined arrows. Simply using a heavier weight that is properly balanced within the accepted FOC range. Shooting lighter to get faster speeds and in effect to pump up the KE, well I just don't see it working.

What I am saying is, and remember this is my opinion....as unexpert as it is, I would not rely simply on formulas, graphs, and charts alone. I just think KE is way overblown and too many archers are basing their arrow choices on it. Thats my opinion and I am stickin to it.

[ELKINMTCWB]

I do not think checking KE is bad. I think People think 10 p of KE is very much.People say I am only shooting 15 p less KE that is not very much at all. But in reality 15 pounds is a lot. It is just eazy for people to just lose 10 or 15 pounds of KE and not feel bad about it.

But if they loose 10 FPS they have a COW.

Just how many FPS dose it take to make one KE pound?

[Sylvan]

Heavier arrows shot from the same bow will always produce more initial KE. The reaon is that KE = Stored Energy - Wasted Energy and heavier arrows waste less energy. The bow is always more efficient in transfering energy from the limbs to the arrow when the arrow is heavier.

[500 fps]

Generally that is true but there are some exceptions. I don't have the #'s on hand anymore, but some bows are so much more efficient with lighter arrows (near the 5 gr/lb range) that the speed increase they achieve generates more KE with the lighter arrows than heavier, when shot from the same bow. Norb Mullaney talked about this phenomena a while back in one of his articles in Bowhunting World, and I've seen the same thing in my own experience.

[gibblet]

momentum is the key, not how much energy something has stored, but how much energy its going to take to stop something. that's what is important, and i think that's what cougarmag is talking about.

[mainehunt]

Cougarmag,
Well said, and I hope you do stick with it!

Kev

[dsheally]

I hear what you are saying. For hunting I use aluminum 2314's weighing 485gr.
and use this for deer,bear and elk. Why do I use such a heavy arrow compaired the
lighter arrows? Because I had bad experiences with light carbon arrows while hunting
and lack of penetration with these. I went back to the old reliable aluminum arrows
that usually blow right through game. My thoughts are the heavier arrow and their
momentum down range are harder to stop thus increases penetration. I guess it
really makes no difference what the arrow is made of, the added weight of the
entire arrow is what is important to me.

[Arthur P]

Coug, the KE stuff started up when people began using ultra light arrows for 3D shooting, then decided to use those same arrows for hunting. Always before, archers used light arrows for target and heavy arrows for hunting. Easy, smart and simple. Not good enough for these 3D guys though! They figured that if they can shoot 3D deer at 50 yards with their little twig arrows, then they'd be able to shoot real deer at 50 yards in the woods too.

So, then they had to start doing all these mathemagical gymnastics and calculations, trying to figure out if they had enough power to actually kill an animal with their target arrows. Then they'd sit around at the end of the day, bragging about how much speed and KE they're getting. They still do, come to think of it.[8D]

[silentassassin]

The reaon is that KE = Stored Energy - Wasted Energy and heavier arrows waste less energy. The bow is always more efficient in transfering energy from the limbs to the arrow when the arrow is heavier.

Sylvan, isn't there a law of deminishing returns that comes into to play somewhere in there

Then they'd sit around at the end of the day, bragging about how much speed and KE they're getting.

Arthurp,

I must admit that I am somewhat guilty of that myself. I must also admit that I have killed an even dozen in the last two years with an EXCEPTIONAL shot to recovery ratios (flawed only by a miss that I still don't know went wrong on) and some mighty impressive passthroughs

[Sylvan]

Sylvan, isn't there a law of deminishing returns that comes into to play somewhere in there

As you go lighter and lighter the transfer of energy to the arrow becomes less and less efficient ultimately to the point where you are dry firing the bow. This of course is the most ineffiecient as all the energy is wasted. The rate of change in efficiency with arrow mass does change but the change in efficiency is always negative when lowering arrow mass and positive when increasing it.

momentum is the key, not how much energy something has stored, but how much energy its going to take to stop something. that's what is important, and i think that's what cougarmag is talking about.

Momentum and KE are both products of mass and velocity therefore both go up and and down together. Not in equal amounts of course but if KE goes up so does momentum and if KE goes down so does momentum. No exceptions. So as you go lighter with the arrow you lower momentum and of course the reverse.

Generally that is true but there are some exceptions. I don't have the #'s on hand anymore, but some bows are so much more efficient with lighter arrows (near the 5 gr/lb range) that the speed increase they achieve generates more KE with the lighter arrows than heavier, when shot from the same bow. Norb Mullaney talked about this phenomena a while back in one of his articles in Bowhunting World, and I've seen the same thing in my own experience.

I do not believe that Norb Mullaney ever said that efficiency goes up when you put on a lighter arrow. If he did he was incorrect. You could put on a lighter arrow and increase KE if you also made some other change to compenstate for the loss in efficiency. For example increase draw weight or lower brace height.