Kenetic Energy

[exocet200hunter]

I'm surprised this has not been brought up in topic yet, after looking at the newer models of Excals ( Matrix and Micros ) I see a lot of Rave about the micros but can't see that the KE of a 16inch quill to be hunt worthy past 30yards.
YES the micros are a sweet little compact xbow but with such a light weight and length bolt ( quill ) I cannot see a big impact on genetic energy past 30 yards compared to say a Matrix model ( longer bolt, and power stroke ).
I feel with such a short quill it will drop dramactically pass 30yards.
Any thoughts on this ?
- Matt

[paulaboutform]

I believe the thing to do would be to shoot an arrow that's heavy enough, and with enough FOC, to generate an appropriate amount of momentum. Kinetic energy is great for determining power but with arrows you're ultimately looking at the amount of momentum generated and the type of broadheads used to achieve effective penetration at varying ranges. I believe you can certainly shoot a 16" arrow beyond 30yards, it just depends on arrow recipe.

Paul

[nchunterkw]

I put a 15 1/2" 520gr arrow completely through a buffalo at 30yds with my Micro back in December. As Paul said, kinetic energy does not necessarily translate into good penetration. Google a guy named Ed Ashby and read his papers. He puts arrows through Asian buffalo out of light weight recurve bows.

[vixenmaster]

KE is about a moot pt usin archery tackle, Real world is weight n momentum wid a clean cuttin broadhead. I use 400gr on up arrows 16"to 20" out of my micro. I have not saw any power loss on killin deer, still gettin pass-through's

[wildcatter]

I had a 335 and from my experience with the 410 grain arrows I was usiong, I had more energy than any Compound verticle bow I ever owned, and all were 70# Hoyt's till the last which was 60# but none carried the KE the little sweet shoot'n Micro did.

Now if ya like them little tooth picks they rate their speed with, I would pick my shots a little different,,,,,, like has been said,,,,, weight and momentum!! KE and heavy arrows with sharp broadheads kill game,,,,, speed is nothing more than what some use to pound their chest and fantasize with,,,, speed don't kill,,, weight and momentum DOES,,,

[DuckHunt]

Because of a little test I ran a couple days ago, your theory caused me to run another quick test. I grabbed one of my 16" arrows and found one of my old 20" Firebolts. I put a 125gr field tip on the 20" arrow so they both end up weighing exactly the same weight. Both were fletched identically (2" blazers). Here is what I shot...

16" Black Eagle Zombie Slayer @ 380 grains, 100gr tip (19.23% FOC)
20" Excalibur Firebolt @ 380 grains, 125gr tip (15.40% FOC)

Both arrows left the bow at 320fps which makes sense since they are the same weight. To answer the question if arrow length impacts speed, no. There was no difference in speed when the arrows reached the target at 50 yards. At 50 yards both arrows clocked in at 294fps. The Block target is not a consistent medium, but both arrows appeared to have similar penetration witnessed by an additional 4" sticking out for the 20" arrow. I was using field points, so penetration could differ greatly with different fixed or mechanical broadheads.

On thing that really surprised me was that although they left the bow at the same speed and arrived at the 50 yard target at the same speed, they did not have the same trajectory. After shooting the pair numerous times, I came to realize that one arrow was consistently shooting about 3.5" flatter (higher, less arc) than the other. This busted a myth I've always had. If you are like me and assumed that the 20" arrow would have a flatter trajectory, then you too were wrong. When aiming at the same spot, the 16" arrow hit 3.5" higher than the 20" arrow of the same weight. This got me to wondering if the FOC of the arrows was causing this delta. In either case, I was surprised.

So your thought that the short quill will drop off beyond 30 yards is bunk. From what I can see, the 16" arrow actually has an advantage. As for momentum, that is entirely tied to the weight and speed of the arrow. Whether the arrow is 16" or 20" doesn't matter as much.

DuckHunt

[Normous]

Perhaps the 16" has less surface area leading to less friction compared to the 20".

[Doe Master]

I feel KE numbers are only valuable if you understand what the number really is .
It is a value that is given to an object in motion .
Where it is of value to us hunters . Is it gives us a value to how much energy is required to pierce the protective layer of our quarry . That is why broadhead manufacters sometimes give a required KE to effectively use their product . Some expandables require more because they use some of that energy to expand . Where as a cut on contact uses far less .

[DMc]

..... When aiming at the same spot, the 16" arrow hit 3.5" higher than the 20" arrow of the same weight. This got me to wondering if the FOC of the arrows was causing this delta. In either case, I was surprised....

Man, DuckHunt, you are doing some great testing! Keep up the good work and thanks for posting it.

[gerald strine]

Because of a little test I ran a couple days ago, your theory caused me to run another quick test. I grabbed one of my 16" arrows and found one of my old 20" Firebolts. I put a 125gr field tip on the 20" arrow so they both end up weighing exactly the same weight. Both were fletched identically (2" blazers). Here is what I shot...

16" Black Eagle Zombie Slayer @ 380 grains, 100gr tip (19.23% FOC)
20" Excalibur Firebolt @ 380 grains, 125gr tip (15.40% FOC)

Both arrows left the bow at 320fps which makes sense since they are the same weight. To answer the question if arrow length impacts speed, no. There was no difference in speed when the arrows reached the target at 50 yards. At 50 yards both arrows clocked in at 294fps. The Block target is not a consistent medium, but both arrows appeared to have similar penetration witnessed by an additional 4" sticking out for the 20" arrow. I was using field points, so penetration could differ greatly with different fixed or mechanical broadheads.

On thing that really surprised me was that although they left the bow at the same speed and arrived at the 50 yard target at the same speed, they did not have the same trajectory. After shooting the pair numerous times, I came to realize that one arrow was consistently shooting about 3.5" flatter (higher, less arc) than the other. This busted a myth I've always had. If you are like me and assumed that the 20" arrow would have a flatter trajectory, then you too were wrong. When aiming at the same spot, the 16" arrow hit 3.5" higher than the 20" arrow of the same weight. This got me to wondering if the FOC of the arrows was causing this delta. In either case, I was surprised.

So your thought that the short quill will drop off beyond 30 yards is bunk. From what I can see, the 16" arrow actually has an advantage. As for momentum, that is entirely tied to the weight and speed of the arrow. Whether the arrow is 16" or 20" doesn't matter as much.

DuckHunt

Hey Duck hunt
Do you have brass inserts in the Zombies I was trying to figure out how you got a higher F.O.C out of the shorter bolt with a lighter head .

[DuckHunt]

Do you have brass inserts in the Zombies I was trying to figure out how you got a higher F.O.C out of the shorter bolt with a lighter head .

Yes sir. The Firebolt has the stock aluminum insert and nock. For my Zombies I use an 80 grain brass insert and a lumenock.
DuckHunt

[wildcatter]

Good stuff DH I think FOC is a lot to do with trajectory, and with the heavier weight pulling the vanes at the end of the shaft I feel the that heavy front end has some momentum doing some things we cant see over that lighterfront end and loger shaft having the same drag of them vanes behind it,, having less momentum up fron pulling fer ya,,,,,,?????? just think'n out loud......

[vixenmaster]

Shorter arrows paradox is less than the longer arrows. They regain their trajecty arc faster

[nchunterkw]

The shorter arrow had more FOC than the longer, so it should have had more arc. It didn't

The longer arrow has more surface area and drag so it should have slowed more. It didn't

So to me that says FOC was not the cause and drag differences were negligible.

The only explanation is that the stiffer Zombie launched at a higher angle. I think the Firebolt (much much less stiff than a Zombie) will vary more coming off the rail due to it's flex and location of the spine with respect to the rail. Be interesting so see if the POI difference varies with which vane of the Firebolt is in the rail.

[carperdoug]

I find that the stiffer arrows will consistently hit higher. I have seen this occur with arrows weighing as much as 25 grains difference and various insert configurations. I have no explanation.

I shoot mostly 40 - 50 yards.

My Executioners, 18 or 20 inch, will have a lower poi than my zombies, 18 or 20 inches. All of these are fletched with 2" blazers. Jerry's Spynal Tapps, 18 or 20 inches, with SK300 vanes will also be higher than the BEs.

Just another puzzling fact of archery.