Speed and KE

[txhunter83]

Using a calculator I found online, I came up with the following data.

What I am currently using:
Hoyt Vectrix
26" draw at 65#
Easton FMJ 400 10.2 GPI
255 FPS
55.62 ft lbs of KE

If I were to go down to the 500's(9.1 GPI), which I should probably be using...
265 FPS
53.69 KE

I just got a great deal on some Carbon Express Maxima 250's(7.3 GPI) arrows on Camofire. Plugging this into the equation yields...
280 FPS
54.18 KE

So I lose roughly 1.5 ft lbs of KE from what I am using currently, but gain 25 FPS on my speed. I think that's a good trade.

I have recently read that more weight automatically means more KE, but according to this calculator, it doesnt.

What do y'all think?

[JP Dorris]

If you keep the speed the same then more weight equal more KE.

Keep in mind that speed is squared in the equation so a drop/increase in speed affect the result more then changing the weight.

I went through the same dilema a few weeks ago and had roughly the same result with the resulting KE. Someone calculated that the increase in speed would only change my impact point by about one inch. In essence no change, so I bought the same weight arrows.

Also someone mentionned the noise that a lighter arrow may cause from the bow, my bow was shooting good with 8.4 gpi so again, why change.

[txhunter83]

If you keep the speed the same then more weight equal more KE.

Keep in mind that speed is squared in the equation so a drop/increase in speed affect the result more then changing the weight.

I went through the same dilema a few weeks ago and had roughly the same result with the resulting KE. Someone calculated that the increase in speed would only change my impact point by about one inch. In essence no change, so I bought the same weight arrows.

Also someone mentionned the noise that a lighter arrow may cause from the bow, my bow was shooting good with 8.4 gpi so again, why change.

Well, that's one thing I was worried about...noise.

[Javelin]

Forget KE and worry about inertia and momentum. Inertia is basically newtons first law and says that an object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an outside force (gravity, or in this case hitting a deer) Momentum is speed x mass and shows how much force must be overcome to slow down or speed up an object. Why is this important PENETRATION
an arrow does not penetrate because its momentum is overcome by an outside force, the deer, it doesnt have anything to do with the energy it has. Think about it, is it easier to stop a truck rolling at 3mph or a baseball at 99mph? Inertia comes into play because the moving arrow doesnt want to stop according to the law, but both gravity and then hitting the deer try to stop it so the more momentum it has the more it will penetrate before stopping

[txhunter83]

Forget KE and worry about inertia and momentum. Inertia is basically newtons first law and says that an object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an outside force (gravity, or in this case hitting a deer) Momentum is speed x mass and shows how much force must be overcome to slow down or speed up an object. Why is this important PENETRATION
an arrow does not penetrate because its momentum is overcome by an outside force, the deer, it doesnt have anything to do with the energy it has. Think about it, is it easier to stop a truck rolling at 3mph or a baseball at 99mph? Inertia comes into play because the moving arrow doesnt want to stop according to the law, but both gravity and then hitting the deer try to stop it so the more momentum it has the more it will penetrate before stopping

So you're saying stick with the heavy arrow?

[Joegeer]

I would like to know where this calculator is on the web so i can play!!

[Javelin]

So you're saying stick with the heavy arrow?

maybe not, I would weigh each arrow to get a total arrow wieght head, shaft insert, fletching ect and get the speed of each which you have. Then take and multiply the speed and total weight of each. Then I would pick the two with the largest number and see how each shoot. if you can shoot one pin out to say 30 yards with one of them and the other you need two pins to thirty, I would shoot the arrow that you can use one pin with as long as the number you get my multiplying mass x speed is not too much different

[tx07]

There is a formula you can use to play instead of a calculator.

But as far as speed over Ke, that's up to the user really.
Some like speed others like Ke.
I jus use the arrows I get a satified flyte out of and don't worry about the little things.

[DPerez905]

I am into speed and KE so that's why I went with the GT500. I shot a 465gr fmj at 337fps and got 117.29 ft/lbs KE. I shot a few hogs with it like that but I have switched to the heavier fmj's 250DG so now I have dropped it down in speed and KE but my bow is a lot quieter. Now I'm wingin a 600 gr arrow and that thing hits like a log. Imo a heavier arrow is better bc it quiet downs your bow and you hit a lil harder.

[Cotton]

All those arrows will blow through a deer but the lighter faster arrow will hit closer to its mark on a ducking deer. A bow is as quiet as you make them. 100 grains difference in arrow weight makes very little difference in the sound level unless your bow has other problems such as lose screws and such.

At bow range a deer will hear the bow no matter what and react, do you want to give them more time to react?

[tvc184]

All those arrows will blow through a deer but the lighter faster arrow will hit closer to its mark on a ducking deer. A bow is as quiet as you make them. 100 grains difference in arrow weight makes very little difference in the sound level unless your bow has other problems such as lose screws and such.

At bow range a deer will hear the bow no matter what and react, do you want to give them more time to react?

X2

If there was a problem with arrows not penetrating deer and making a clean kill then it is an issue. I don't see much of a problem with that using modern compounds and arrows.

[HogHunter34]

I am into speed and KE so that's why I went with the GT500. I shot a 465gr fmj at 337fps and got 117.29 ft/lbs KE. I shot a few hogs with it like that but I have switched to the heavier fmj's 250DG so now I have dropped it down in speed and KE but my bow is a lot quieter. Now I'm wingin a 600 gr arrow and that thing hits like a log. Imo a heavier arrow is better bc it quiet downs your bow and you hit a lil harder.

WOW...you must have some nitro booster arrows to hit 337 fps at an arrow weight of 465 grains. That's some serious KE! Might could shoot through a house

[TXPalerider]

.......
I just got a great deal on some Carbon Express Maxima 250's(7.3 GPI) arrows on Camofire. Plugging this into the equation yields...
280 FPS
54.18 KE

...........

I shoot Maxima 250s with my Black Ice (IBO almost the same) at 65# with 26.5" draw, but, I know I'm not getting near 280 fps from it. Are you accounting for the complete weight of the arrow? I'm just not quite sure you can get there.

Not trying to be difficult, just want you to have good info when making your decision.

Regardless, I think the Maxima is a fine choice. i love them.

[crittergitter]

I would like to know where this calculator is on the web so i can play!!

http://home.att.net/~sajackson/ke.html

[Bill]

Forget KE and worry about inertia and momentum.

Forget KE and worry about tuning the arrow/broadhead to shoot exactly where you want it to hit, and having a sharp broadhead. Arrows kill by exsanguination (blood loss) and not by destroying tissue and organs by the transfer of energy like a bullet. This has been debated ad-nauseam on multiple bowhunting web sites. A heavier arrow will be quieter, all things being equal. It may matter on large, dangerous game but for deer and pigs I don't believe so.