K.E. VS Momentum

[BT]

smj said:

By gum, this thread is taking shape! If I get a little time over the holidays, I'll break out the physics book and add my 2 cents from the math side of it.

Looking forward to it

[michihunter]

skipmaster1 said:

The thing with the crossbow....... you will get slightly more KE from a heavier arrow at the same weight....
Can we turn the #'s down a crank. If not we will have to add some brass nocks to slow it down a bit more with the heavy arrow. we want the exact same KE for both tests so we are in fact testing apples to apples.

Although you may have a valid point, isn't the test being performed to decide what would penetrate more out of an individual setup? For example, would a 350 gr arrrow out of a 70# bow pentrate more than a 450 gr arrow out of the same setup? I think this is what the average archer would prefer to know.

[BT]

skipmaster1 said:

The thing with the crossbow....... you will get slightly more KE from a heavier arrow at the same weight....
Can we turn the #'s down a crank. If not we will have to add some brass nocks to slow it down a bit more with the heavy arrow. we want the exact same KE for both tests so we are in fact testing apples to apples.

NO

We don't want that skipmaster or the lighter shaft doesn't have a chance

Not to mention that real world application makes this scenario impossible to duplicate by the average bowhunter.

This is to say that you cannot increase weight and maintain speed within the same parameters using the same simulation devise.

If a person wanted a heavy shaft they would have to live with the fact that they are going to lose speed and vise/versa.

In order to know what is better in a hunting application we must do this test in a real world setting.

Hence keeping the bow the same and only changing the arrow weight.

[Greg Krause]

Michi- I guess you are right. I was just thinking we were gonna compare penetration vs arrow weight. otherwise it will be penetration vs arrow weight vs KE.
your way would be better for real life conditions though.

[Greg Krause]

Bt I was saying slow the hevier one down more, not the light shaft. because the heavy one will be higher ke, even thought it is slower. so the KE's would be the same, not the speeds.

I do agree we should just do real life scenarios though.

[rreda]

I am just getting caught up with this thread, since I posted the other day. I had no idea what my "treestand musing" was going to start. But I do think that it is worth the effort.

[Greg Krause]

This debate goes on and on, all over. every place bowhunters get togther. we have facts but no one can tell you for sure what they mean.
Fact- More KE is better for penetration. How much is really needed though, and for what?
Fact- It is easier to bump KE up, by going to a heavier arrow. again, how much is needed?
How much will you gain?Are the tradeoffs worth it or not?
Fact- Momentum plays a part in penetration. How much? More than ke?

Fact- a heavy arrow(to a point) will out penetrate a lighter arrow(shot from the same set-up)

It goes on and on. For thin skinned deer, I personally rest my bets on KE and flat shooting. My 370grain arrows are awesome. For bigger game I want a happy medium. Say 400-450grains for elk,moose, Grizzly and so on. A lighter arrow will do the job, but momentum will help on long shots at thick critters. On real big game, like Cape Buffs, I am only taking close shots, 25yds or so. I want the MOST KE and Momentum. Flat shooting holds little value to me here. 750+ grains with 85#'s or more KE. You wouldn't catch me there without a Draw weight of at LEAST 90#'s on an efficent bow.

Bottom line is, deer are thin, "easy" to penetrate animals. I will take a slight drop in KE and momentum for better shot placement at unknown ranges. most of us are overkill anyway. a 37# longbow will zip straight through a ribs only shot on a deer at 20yds or less. compounds are more efficient and we are shooting higher weights.

[BT]

skipmaster1 said:

AND HERE IS HOW THE THREADS GENERALLY GO

Fact- It is easier to bump KE up, by going to a heavier arrow.
[blue]Fact- It is easier to drop arrow weight and increase speed to achieve higher K.E.
Increasing arrow weight drops speed which reduces K.E.[/blue]

Fact- Momentum plays a part in penetration. How much? More than ke?
[blue]Fact-Momentum comes at a loss of K.E. due to weight[/blue]

Fact- a heavy arrow(to a point) will out penetrate a lighter arrow(shot from the same set-up)

[blue]Fact- True , but only if the K.E. remains the same to the lighter shaft.[/blue]

[yellow]SEE! [/yellow] ;D

[Greg Krause]

;D ;D ;D

See, it never ends.

Bt, with all bows I've had, I can get slightly more ke with a heavy arrow over a light one. the arrow just sucks up more energy. same draw weight same draw length

488 grain arrow at 258fps
370 grain arrow at 290fps
plug it in

[Greg Krause]

I just used Bowjackson
I came up with 72# KE for the 488grain
69#KE for the 370grain