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pupper
04-03-2007, 11:14 PM
Who has calculated their bow/arrow setup in ft. lbs of kinetic energy?

The formula is: (velocity x velocity) X arrow wieght in grains / 450,250= ft. lbs of kenitic energy

my rig is a bowtech tribute 70# w/ 27.5" draw and I shoot 5575 gt xt hunters.

with a 100 grain tip I am shooting 291 fps, my arrow wieght is 361 grains.

make sure you chrono your shooting as my bow says it shoots 338 fps but through the chronograph it shoots 291.

so the calculation looks like this:

(291 x 291) x 361 / 450,250= 67.895

so rounding up my bow/ arrow set up hits with 68 ft. lbs of kinetic energy.

what type of punch are you packing?

bochunk2000
04-04-2007, 01:44 AM
From what I gather I'm shooting about 270 fps.
We chrono'ed it 60# and got 245 and then dialed it up to 69 lbs.
27.5 in arrow with 125gr broad heads. I have a 28" draw length.
When I weighed the arrow a couple of days ago it weighed 429gr total. When I do the math that gives me about 69.5 lbs kinetic energy.

Could anyone please tell me what the minimum should be to hunt with. I'm pretty sure this is plenty I am just wondering the minimums. Thanks Steve.

J_T
04-04-2007, 08:16 AM
Thanks for the post and the formula Pupper. I went looking for it in my stuff and couldn't find it.

I shoot a 64# recurve, 200 fps and a 750 gr wood arrrow. Works out to 67 ft lbs of energy.

I just made up some carbon arrows, thinking lighter (flatter trajectory) and I was able to build an arrow weighing 630 gr. This new arrow now gives me 56 ft lbs of energy.

If you want more KE >> go heavy.

JT

Bow Walker
04-04-2007, 08:52 AM
Steve, there was an arrow site that I believe had the recommended KE for different game. Of course I can't find the site anymore. But from what I do recall, Elk was around 54 - 58 lbs per square foot. For Bear it was the same.

You don't have anything to be shy about or to worry about.

road warrior
04-04-2007, 09:02 AM
(315x315)x415/450250=91.45669.Hoyt Cybertec 80lb 31"draw 27"415grn arrow.

bochunk2000
04-04-2007, 09:14 AM
(315x315)x415/450250=91.45669.Hoyt Cybertec 80lb 31"draw 27"415grn arrow.

:-o Wow! That sounds like you could take down a mack truck with good penitration. LOL.
Steve.

Thanks Dann I will have a look for that site.

Bow Walker
04-04-2007, 09:24 AM
My main problem is that I haven't been able to chrono my new bow:mad: I don't know what the heck I'm getting from it.

I'm also in the process of building a couple dozen new arrows - starting with GT5575 camo shafts. I got the camo by mistake. I usually use the plain black shafts as they are a tad lighter overall.

I guess one side benefit from the slightly heavier camo shafts will be a bit more KE when I'm finished. We'll see when I'm done.

Maybe I'll make the long arduous trek over the 'Hat to see Sampson - he's got a chrono that I can most likely use if I get on my knees long enough:oops: :roll:

willyqbc
04-04-2007, 09:28 AM
heres an online calculator that will take the math out of this...just punch in your numbers!!

http://www.iowabowhunters.org/KineticEnergyCalc.asp

My set-up this year will either be a 460 grain arrow doing 270fps or a 485 grain arrow doing 264fps... both yeild around 75 ft/lbs.

Chris

Bow Walker
04-04-2007, 09:47 AM
Here's an interesting site. Ever wondered of fast you're really shooting that arrow??

http://www.calculateme.com/Speed/FeetperSecond/ToMilesperHour.htm

The Hermit
04-04-2007, 09:49 AM
Hey BowWalker! Franko has a chrono and we have been trying to tee up a time to get to the range with it. I need to sight in my new Weatherby, hopefully on Sat... maybe we can get Frank to come up and fling some arrows too! Hutch is also talking about the need to get out and fling a few too!

Bow Walker
04-04-2007, 10:24 AM
http://smileys.smileycentral.com/cat/16/16_12_168.gif (http://www.smileycentral.com/?partner=ZSzeb001_ZSYYYYYYJOCA) Sounds good.........let me know.http://smileys.smileycentral.com/cat/36/36_1_11.gif (http://www.smileycentral.com/?partner=ZSzeb001_ZSYYYYYYJOCA)

J_T
04-04-2007, 12:39 PM
Hey guys, isn't there some guidance provided somewhere or a rule of thumb or perhaps its a law somewhere that says an arrow must (I can't remember) either have a minimum weight, or must be 10 grains for each pound of bow pull.

IE I shoot a 64 pound bow therfore a well matched/efficient arrow for my bow is a 640 gr arrrow.

I might be way out in left field here. I haven't thought about this for some time.

JT

Tuffcity
04-04-2007, 01:04 PM
J T,

I think that the 10 gr/pound is more of a guide line for trad setups. IIRC it roughly averages out bow efficiency with an adequatly massed arrow to achieve decent speed, quietness and penetration potential.



Could anyone please tell me what the minimum should be to hunt with.


I think that minimum draw weight within an archers draw length is a better guideline for hunting. With minimum KE requirements you will exclude lower poundage stick bows that will cleanly kill game if decent weight arrows are used.

KE is a better indicator of bow efficiency than actual "killing" power. Calculate the force your arrow produces and see how it stacks up. Certainly not nearly the manly numbers that KE calculates out at but probably a better indicator of the potential to push an arrow through something.

RC

J_T
04-04-2007, 01:07 PM
Thanks RC.

pupper
04-04-2007, 05:55 PM
Thanks for the post and the formula Pupper. I went looking for it in my stuff and couldn't find it.

I shoot a 64# recurve, 200 fps and a 750 gr wood arrrow. Works out to 67 ft lbs of energy.

I just made up some carbon arrows, thinking lighter (flatter trajectory) and I was able to build an arrow weighing 630 gr. This new arrow now gives me 56 ft lbs of energy.

If you want more KE >> go heavy.

JT

I dont know if going heavy is the answer because velocity is squared in the calculation so every fps faster you actually gain twice as much in the calculation. plus going heavier takes away from shooting flatter.

Justin

pupper
04-04-2007, 06:00 PM
(315x315)x415/450250=91.45669.Hoyt Cybertec 80lb 31"draw 27"415grn arrow.

is that chrono speed or advertised speed?

with a drawlength at 31" i guess that number is very attainable!!!

Tinney
04-04-2007, 06:05 PM
KE is relative. Gah this is the same as energy from a rifle....he with the most has the biggest...err....ego

Shot placement will forever rule supreme.

pupper
04-04-2007, 06:14 PM
KE is relative. Gah this is the same as energy from a rifle....he with the most has the biggest...err....ego

Shot placement will forever rule supreme.

what if shoot a thick hided animal in the right spot but it cant penetrate?

then is shot placement still supreme?

Tinney
04-04-2007, 06:30 PM
What animal are you hunting in BC that has a thick enough hide that ANY modern bow cannot penetrate!?

J_T
04-04-2007, 06:39 PM
what if shoot a thick hided animal in the right spot but it cant penetrate?

then is shot placement still supreme? Nope, if you can't penetrate it's a question of the leading edge of your arrow. The broadhead.

pupper
04-04-2007, 06:45 PM
What animal are you hunting in BC that has a thick enough hide that ANY modern bow cannot penetrate!?

your right, pretty much any modern compound set at 50#+ shooting the right arrow and a razor sharp broadhead will get the job done. Then shot placement is definetely trump!

Tinney
04-04-2007, 07:00 PM
I mean if you're gonna hunt something enormous like a griz or a buffalo, step up to the plate and pull the extra poundage but mean common, for anything moose-sized and smaller......what are we really comparing here? ;)

pupper
04-04-2007, 09:29 PM
I mean if you're gonna hunt something enormous like a griz or a buffalo, step up to the plate and pull the extra poundage but mean common, for anything moose-sized and smaller......what are we really comparing here? ;)

what is the point of measuring anything or talking about anything?

interest sake? mans competetive nature? discussion?

come on tinney what is your point here? should we not even mention what poundage we shoot or fps? whats the point of that?

anyways lets get back on topic of kenitic energy!!!!!

Justin

Eagle1
04-05-2007, 08:22 PM
B.C. hunting regs say " minimum 40# at your draw lenght to hunt "
Tere is also a minimum bow weight and arrow weight to hunt with if your lucky enough to get a buffalo draw, can't remember, it's in the LEH paper.
I had a chance to shoot and chrono the new Alpine Silverado { IBO 325 fps }
I shot a 452 gr arrow at 68 lbs, 29 draw, 280 fps, that just over 129 KE boys.

Also the magic number is " 450,240" not 450.250.

Thing is shot placement and a sharp broadhead.They been doing bowhunting for hundreds of years with less efficeint bows than we have now a days, but a little KE never hurts if theres an oppps, s - - t happens, animals move, buck fever and so on.

bochunk2000
04-05-2007, 08:30 PM
I shot a 452 gr arrow at 68 lbs, 29 draw, 280 fps, that just over 129 KE boys


Not to argue Bill but when I do the math it comes out 78.7 KE. Am I doing it wrong? I went to that site posted earlier.

http://www.iowabowhunters.org/KineticEnergyCalc.asp

Let me know if that site is wrong so I can re-do my calculations.
Steve.

Eagle1
04-05-2007, 08:33 PM
B. C. hunting regs say " min 40# to hunt with "
There is a min bow weight and arrow weight if your lucky enough to draw a buffalo tag. Don't know right now what it is but its in the LEH paper.


I had a chance to shoot and chrono the new Alpine Silverado {Ibo 325 fps}
Shot a 452 gr arrow, 68 lbs, 29 draw, an impresive 129 + KE

Thing is shot placement and a sharp broadhead, for hundreds of years they've been bowhunting with less efficant bows than ours now a days and a lot less K E. a little K E goes a long ways for those ooppps shots, s - - t happens, animals move, buck fever.

Eagle1
04-05-2007, 08:45 PM
Not to argue Bill but when I do the math it comes out 78.7 KE. Am I doing it wrong? I went to that site posted earlier.

http://www.iowabowhunters.org/KineticEnergyCalc.asp

Let me know if that site is wrong so I can re-do my calculations.
Steve.

Well i don't know about that site calculation , but by the way I've been told for years now is :
arrow 452 x 452 xspeed 280 div by 450,240 = 127 + K E

jessbennett
04-05-2007, 08:46 PM
according to calculations, that would be just around 79 ft/lbs energy not 129.... am i wrong here??? could be. it has been known to happen from time to time..:lol:

bochunk2000
04-05-2007, 08:47 PM
Ok I was taught that its the weight x the speed x the speed
450240

I might be squaring the wrong one
Steve.

jessbennett
04-05-2007, 08:49 PM
what do ya know, my lighter faster arrow has more kinetic energy...........:confused: :)

Eagle1
04-05-2007, 09:05 PM
Weeeeeelllllllll, don't I have egg on my face, it's been awhile since I did the K E calculation, it is speed x speed x weight div by 450,240.

Speed does over take mass, phyisics,

Sorry guys.
oldtimers dicease

interceptor
04-06-2007, 03:15 AM
G' Day Lads,

I posted this earlier on a different thread, I think it adds to the KE debate aswell. You can shoot what you like as hard as you like,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

If the broad head ain't shaving and the arrow not flying true than you WILL lose out on penetration and thus not get the damage down range that you would have wanted. All I am saying is what ever you shoot, if you have over 40# draw wieght and your gear shoots a shaving sharp BH and the arrow has great flight (all this can be done before you even see an animal),,,,,,,,,,,,,,SOOOO the only thing you need to worry about when you see that big buck or whatever is,,,,,,,,,,,,,,,,,,,,,Shot placement.

Geez, glad I got that of my chest:lol: :lol:




G' Day Lads,

This my first post so be gentle with me :lol:

While I have never been to BC, I have hunted some fair bruisers over here in Australia and I have been in on a few hunts with other lads on Buffalo. These are one of (if not the) toughest critters around. Between me and a small group of mates we have tried arrows from 450 grains right up to over 800 grains, all out of current model top line compounds.

IMHO there are two things that make for good penetration.

1, The broad head has to be shaving sharp, not just sharp but SHAVING sharp. If the hairs on your forearm don't run away from blade then it ain't sharp.

2, Arrow flight, if your arrow flies like a dog and wags all the way to the vital zone you will lose heaps of penetration. When you let them go you should see nothing but the nock of your arrow disappearing into the kill zone.

http://img.photobucket.com/albums/v487/interceptor429/hunting%20pics/FirstBuffTrip005.jpg

At my first arrow he was quartering away hard and my arrow buried all the way, the broad head stopped on the far side shoulder. My finishing shot went in between the shoulder blades and the BH came out around 4 inches between the front legs (he was laying in the shade feeling the effects of my first arrow) he stood at the shot then dropped for the count after eye ballin me for a few seconds.

I shoot a Mathews Switchback, 73#, 29" draw and my arrows weigh around 470 grains.

Cheers Noel


Cheers Noel

pupper
01-31-2008, 11:42 AM
what do ya know, my lighter faster arrow has more kinetic energy...........:confused: :)

I was thinking about this topic over the last couple months and what I had on my heart was this:

we measure our arrow speed coming right out of the shoot, a lighter arrow will be faster at this point but what about at 40 yards? wont a heavier arrow have more momentum and penetrating power at these yardages? a light arrow can be stopped quicker than a heavy arrow right? so this calculation can be a little misleading when we measure the arrow coming right off the rest. So in essence I am wondering, what is the magic combiniation for speed and penetrating power?
for example this video:
http://www.youtube.com/watch?v=uaEWhGHfCJA&feature=related

shows a kid spearing a doe with complete pass through, this is an example of wieght and penetrating power with little speed.

willyqbc
01-31-2008, 03:00 PM
everything in archery is a trade-off...there is no free lunch

as pertains to this discussion lets look at a few of the variables

speed is definately an ally if it can be controlled (you can maintain accuracy), however if you go with a very light arrow to acheive a good chrony reading your downrange performace will definately suffer. conversely if you go with too heavy an arrow the range and tragectory will suffer, the trajectory will be a rainbow making yardage estimation absolutely critical, but the short range power and penetration will be better. As a good illustration think of a person throwing a ping pong ball, a baseball and a shot put. the ping pong ball will start out the fastest but will bleed energy VERY quickly and be of little use in a short range. The shot put will have a lot of hitting power but will have a very short range and will drop like a rock as it loses speed. The baseball is the obvious choice.

So for me i like a medium heavy arrow....380-400 grains. I will shoot this arrow as fast as I can while maintaining the accuracy of my groups. From experience, I know this set-up will deliver on any animal I choose to shoot.

Another critical component is being sure you have properly spined arrows....too stiff or too soft will cause a loss of efficiency which will obviously translate into a loss in downrange performance. Coupled with this and in conjunction with your arrow length and fletching choice, pay particular attention to your choice of broadhead weight. Too heavy or too light can also cause inefficient arrow flight and loss of downrange performance.

Just my opinion
Chris

pupper
01-31-2008, 10:28 PM
Yah chris, I agree totally with you. So for my settup I am shooting a 361 grain arrow (5575 prohunter) at 27.5" draw. I was thinking of increasing my spine stiffness or switching to FMJ eastons. but I think I am at the right combo right now.

Kirby
01-31-2008, 10:46 PM
I'm slinging them with about 73 pounds of kinetic energy.

Haven't had anything debate the power behind it.


An interesting point, couple of years ago I hit a mulie with 70 pounds behind the arrow and it failed to even penetrate to the lungs. Clipped the shoulder, turned and ran down under the hide, I blame the mechs, but it goes to show don't really matter how hard you hit it if your shot placement is off.

Kirby

Bow Walker
02-01-2008, 09:45 AM
I stopped using N.A.P. Spitfires for the same reason - not that I hit a deer that way, it's just that on angled shots or bone shots the chances of the mech not opening properly and doing it's job are much higher than with any other head.

I now use one piece broadheads since replaceable blade heads have fairly fragile blades. I like the toughness of the one piece heads.