Impressive. What type of setup do have slingin' those telephone poles out to 80?
KE, Momentum, Speed/FPS, Ethical Kill
- Thread starter Graindrain
- Start date
Impressive. What type of setup do have slingin' those telephone poles out to 80?
jmez
WKR
Carbon Element and ZT Carbon Spyder Turbo.
I shot out to 100 with a CBE slider now.
I shot out to 100 with a CBE slider now.
- Thread Starter
- #23
OP
Graindrain
Lil-Rokslider
Shooting out to that distance is not my concern though. Its what is the arrow packing at that point.
My slider will go to 102 before hitting the FOB or Fletching.
I thought about cutting a hole in ply wood to create a barrier and checking speed out at these distances but I don't know anyone that trusts me to borrow their chrono.
My slider will go to 102 before hitting the FOB or Fletching.
I thought about cutting a hole in ply wood to create a barrier and checking speed out at these distances but I don't know anyone that trusts me to borrow their chrono.
moxford
Lil-Rokslider
If you have the spare cash, got for the upgrade because it won't hurt.
But.
At 60 yards, the flight time difference is negligible.
At 60 yards, the KE is bleeding off really quickly and doesn't really matter.
At 60 yards you need a heavy arrow to, as larryschwartz says, KEEP your momentum.
Either bow will get a pass-through at 60 yards on a clean shot. What you're doing is hedging your bets on a non-clean shot. And if that's what you're doing, you need momentum. That means a heavy high-FOC bone-busting setup.
Remember, KE is "(0.5)*m*v^2".
Momentum is "mv".
As your arrow slows down (for any reason) your KE will bleed of EXPONENTIALLY compared to your momentum. The instant your arrow touches that animal your KE plummets. Momentum derives equal portions from mass (a constant) so even as v drops your momentum "push through" power stays higher. So focus on momentum and not KE or FPS.
If your rig won't shoot the required (heavier) arrow at that distance, well, then upgrade.
Yes, you will gain more arc.
Yes, you will gain more pin-spread.
Yes, it will take longer to impact.
Remember that trad-bow guys are often shooting under 200 fps but 600+ grain arrows for big game (1000+ gr for really big game). Your bow will shoot those heavier 500-600gr arrows but you'll have to run a stiffer spine, more weight up front and even if you end up around 220 FPS you'll have much more punch on a marginal shot.
And if you don't care about the marginal shot, your existing bow will punch through soft-tissue just fine.
I have no idea what I'm talking about and all numbers are completely made up.
-mox
But.
At 60 yards, the flight time difference is negligible.
At 60 yards, the KE is bleeding off really quickly and doesn't really matter.
At 60 yards you need a heavy arrow to, as larryschwartz says, KEEP your momentum.
Either bow will get a pass-through at 60 yards on a clean shot. What you're doing is hedging your bets on a non-clean shot. And if that's what you're doing, you need momentum. That means a heavy high-FOC bone-busting setup.
Remember, KE is "(0.5)*m*v^2".
Momentum is "mv".
As your arrow slows down (for any reason) your KE will bleed of EXPONENTIALLY compared to your momentum. The instant your arrow touches that animal your KE plummets. Momentum derives equal portions from mass (a constant) so even as v drops your momentum "push through" power stays higher. So focus on momentum and not KE or FPS.
If your rig won't shoot the required (heavier) arrow at that distance, well, then upgrade.
Yes, you will gain more arc.
Yes, you will gain more pin-spread.
Yes, it will take longer to impact.
Remember that trad-bow guys are often shooting under 200 fps but 600+ grain arrows for big game (1000+ gr for really big game). Your bow will shoot those heavier 500-600gr arrows but you'll have to run a stiffer spine, more weight up front and even if you end up around 220 FPS you'll have much more punch on a marginal shot.
And if you don't care about the marginal shot, your existing bow will punch through soft-tissue just fine.
I have no idea what I'm talking about and all numbers are completely made up.
-mox
- Thread Starter
- #26
OP
Graindrain
Lil-Rokslider
Mox, Thank you very much.
I have decided to upgrade the setup to the Xcentric 6. I can sell the Perfexion and buy the new bow with some extra cash laying around.
Given the extra speed the new bow will have and the Kinetic Kaos arrows I am shooting I can always add more weight and increase mass and the FOC with Gold Tips F.A.C.T. system.
The information that Mox provided proves the point to me.
The amount of speed lost with the heavier arrows makes the momentum less in the example of shooting the 500+ grain arrows.
I think it is interesting the different ideas presented by some wanting speed, some believing the key to the best set up is KE, and then the example Mox gives showing the key is Momentum.
Thanks for the help guys.
I have decided to upgrade the setup to the Xcentric 6. I can sell the Perfexion and buy the new bow with some extra cash laying around.
Given the extra speed the new bow will have and the Kinetic Kaos arrows I am shooting I can always add more weight and increase mass and the FOC with Gold Tips F.A.C.T. system.
The information that Mox provided proves the point to me.
The amount of speed lost with the heavier arrows makes the momentum less in the example of shooting the 500+ grain arrows.
I think it is interesting the different ideas presented by some wanting speed, some believing the key to the best set up is KE, and then the example Mox gives showing the key is Momentum.
Thanks for the help guys.
roadrunner
WKR
http://archeryreport.com/2010/09/arrow-foc-basics-calculate/
moxford - you are correct in all your statements (other than the last one about not knowing what your talking about!!). I also have something that shows the relationship of KE vs. Momentum (p) graphically, but can't get it to post because Excel is an invalid file and the pdf version is too large, but, KE does fall off at a faster rate than momentum because of the square of the velocity.
For anyone - All KE does is show what it takes to get the arrow moving at a specific velocity for a specific mass. Other than that, it is meaningless. Correct stiffness of the arrow and a higher FOC will make better for trajectory, penetration, and velocities.
This can always be a controversial debate for anyone, read the article, especially pay attention to paragraph 7. I use a light arrow but a high FOC and have better results than another guy I know that shoots a heavy arrow. My setup is 305 fps, 400 gr, and 16% FOC.
Jacob Chapman
WKR
KE means nothing unless the animal you shoot is the same distance away as the chrono you are shooting through. Momentum is king
5MilesBack
"DADDY"
You should have someone shoot your bow while you stand someplace down range right near the 60 or 70 yard target and watch and listen to the arrows as they zip by and hit the target. It's impressive. My buddy and I have done this out to 130 yards, and even at that distance it's impressive.
I laugh every time I hear someone say "At 100 yards your arrows are just going to bounce off the animal". I doubt I'd ever shoot that far at an animal, but if I did I'd have absolutely no doubt that my arrow is blowing right through an elk on a broadside shot. Yes, I have more KE and Momentum than most, but I don't think most people give their setup enough credit. My longest shot on an elk was 71 yards, quartering away, with my 60lb bow shooting a 445gr arrow at 272fps. That arrow penetrated from behind the ribs and stuck in the offside shoulder.
Last year with a 70lb bow and a 500gr arrow at 285fps with an expandable from 54 yards, the arrow blew through the bull quartering away and blew through the humerus on the offside, and still landed 20 yards behind the bull. Now I'm shooting a 532gr arrow at 286fps.
I laugh every time I hear someone say "At 100 yards your arrows are just going to bounce off the animal". I doubt I'd ever shoot that far at an animal, but if I did I'd have absolutely no doubt that my arrow is blowing right through an elk on a broadside shot. Yes, I have more KE and Momentum than most, but I don't think most people give their setup enough credit. My longest shot on an elk was 71 yards, quartering away, with my 60lb bow shooting a 445gr arrow at 272fps. That arrow penetrated from behind the ribs and stuck in the offside shoulder.
Last year with a 70lb bow and a 500gr arrow at 285fps with an expandable from 54 yards, the arrow blew through the bull quartering away and blew through the humerus on the offside, and still landed 20 yards behind the bull. Now I'm shooting a 532gr arrow at 286fps.
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moxford
Lil-Rokslider
I forgot to insert obligatory Dr. Ashby links. Here's a good archive of it: http://tuffhead.com/education/ashby.html
Read it. All of it. All the calcs and napkin math and theorycrafting pale in comparison to empirical testing and field data. It's all done with a trad-bow, so it'll scale up even better for compounds.
It's easy to go too far off the deep-end, though. Range estimation is more difficult with a slower bow, and the greater arc means more chance for branch-contact.
-mox
Read it. All of it. All the calcs and napkin math and theorycrafting pale in comparison to empirical testing and field data. It's all done with a trad-bow, so it'll scale up even better for compounds.
It's easy to go too far off the deep-end, though. Range estimation is more difficult with a slower bow, and the greater arc means more chance for branch-contact.
-mox
Violent Hippie
WKR
The data / charts I have read (including the links provided in this post) show 42-65 KE for elk sized game. In regards to the original post it appears you are good to go and there is no justification to buy a new bow. Sorry . Ha . Ha. I on the other hand have been using a setup shooting 45 KE and even after spending time shooting through the chrono with different weight arrows and working the numbers cant get over 46 KE which is on the lower end of the elk sized game chart. Based on this I feel justified to buy a new Elite this year.
moxford
Lil-Rokslider
Look at it this way:
momentum #1: 10kg * 10m/s
momentum #2: 1kg * 100m/s
Exactly the same momentum. MUCH higher KE on #2. But the instant your arrow contacts anything, including your target, that target is going to start slowing your arrow down very very quickly. The resistance provided by your target will bleed off your velocity proportional to the mass. So lighter weight items slow down quicker. Throw a baseball at me, 100MPH, and I can catch it. Roll a car at me at the slowest speed possible and there's probably no way I can stop it. Heavier arrows carry the "push' better through an animal on marginal shots. With soft-tissue shots it's just overkill.
Some like speed because it makes range-estimation errors less critical. There's less chance of a branch conflict. Less chance of a string-jump.
Some like KE because of the high numbers that go along with speed.
Momentum fans have figured out that you can get some really impressive KE numbers at the point of contact but that the arrows just don't punch through as well.
Find your own happy medium.
-mox
5MilesBack
"DADDY"
You must have meant "more critical", as range estimation is completely independent from the speed of your bow, or whether you even have a bow in your hands.
moxford
Lil-Rokslider
You must have meant "more critical", as range estimation is completely independent from the speed of your bow, or whether you even have a bow in your hands.
I'll go with "less forgiving."
Hopefully between the three variants everyone will understand. =P
tipsntails7
WKR
- Joined
- Jul 30, 2013
- Messages
- 3,428
An easy way to visualize it is kinetic energy is a non directional force. Unlike momentum.
Rifles kill with KE(most of the time) they are imparting "shock" on an animals system
Arrows kill with momentum, they cut through the animal and cause bleeding.
KE was adopted by the archery industry as a buzz word, it's a tangible number that sounds great and doesn't have a decimal point in it, unlike Momentum
If you shoot a "normal" weight arrow and have a good KE number your momentum will be just fine. They are not the same thing but are correlated, at least in this discussion.
Not to stir the pot here, but I do think the whole momentum vs KE is a debated topic even among well established archers and people with a professional understanding of physics. For the record, I side with momentum wholly.
However, I always see the example of the baseball vs ping pong ball being thrown at you, or something similar, which illustrates the concept well. But, I think there is a huge difference between the two, and the difference in a heavy arrow and light one could only be a hundred or so grains. So practically speaking, I wonder if that small difference on paper actually translates into something pragmatic? Does anyone have a link to some actual testing done with the light/heavy debate? Perhaps the small gain in momentum on paper doesn't really make a difference in real life practice, unless its a drastic change, i.e. 350 grain ibo arrow to a 700 grain telephone pole?
However, I always see the example of the baseball vs ping pong ball being thrown at you, or something similar, which illustrates the concept well. But, I think there is a huge difference between the two, and the difference in a heavy arrow and light one could only be a hundred or so grains. So practically speaking, I wonder if that small difference on paper actually translates into something pragmatic? Does anyone have a link to some actual testing done with the light/heavy debate? Perhaps the small gain in momentum on paper doesn't really make a difference in real life practice, unless its a drastic change, i.e. 350 grain ibo arrow to a 700 grain telephone pole?
moxford
Lil-Rokslider
Calculate the momentum values in slug-ft-per-second. That difference is your quantifiable value.
Let's say you get a 0.5 slug-ft/sec difference. Does that matter? Well, since 1 slug != 14.6kg (or 32.2 lbs) then you can start to see a difference because your arrow then has 7.3kg (16.1 lbs) of extra push. That's an extreme example, but you get the idea.
Incoming napkin-math...
http://archerycalculator.com/archery-kinetic-energy-and-momentum-calculator/
300 grains @ 300 fps = 0.3992 slug-ft/sec
700 grains @ 200 fps = 0.6211 slug-ft/sec (0.2219 slug-ft/sec difference, or about 7.14 lb-ft/sec extra push, over a 50% increase from the baseline.)
There a lots of other factors here, but this is one of those "argh argh argh more more more is better!" kind of things. To a point. 4000gr moving at 0.1 fps is pretty useless.
As for actual real life data and testing, read those Ashby links I posted, above. He does all of that, in depth, over many years in many situations with real world targets.
-mox
Let's say you get a 0.5 slug-ft/sec difference. Does that matter? Well, since 1 slug != 14.6kg (or 32.2 lbs) then you can start to see a difference because your arrow then has 7.3kg (16.1 lbs) of extra push. That's an extreme example, but you get the idea.
Incoming napkin-math...
http://archerycalculator.com/archery-kinetic-energy-and-momentum-calculator/
300 grains @ 300 fps = 0.3992 slug-ft/sec
700 grains @ 200 fps = 0.6211 slug-ft/sec (0.2219 slug-ft/sec difference, or about 7.14 lb-ft/sec extra push, over a 50% increase from the baseline.)
There a lots of other factors here, but this is one of those "argh argh argh more more more is better!" kind of things. To a point. 4000gr moving at 0.1 fps is pretty useless.
As for actual real life data and testing, read those Ashby links I posted, above. He does all of that, in depth, over many years in many situations with real world targets.
-mox
Last edited:
moxford
Lil-Rokslider
There is no "global" target.
On one end of the spectrum: with a perfect shot you need enough momentum to push through the soft-tissue a deer. That's not very much ... 45 lbs recurve with wooden arrows.
On the other end: a terrible shot where you need to blow through the ribs and shoulder of an African Cape Buffalo. 100lbs @ 20 yards with 1200gr.
The question is, what are you shooting? A moose-arrow is (probably) not the same arrow you're going to use on the open plains for antelope. Or pigs. Though it might be. No reason you couldn't shoot a 700 gr arrow at a speed-goat ... if you can get close enough.
On the open range, maybe speed matters. Maybe you don't want a 0.9 second flight time at 60 yards. (180ft / 200 fps) Maybe you're okay with it. Maybe you think "antelope are pretty small, with a lighter bone-structure ... I want to go to 300fps so the flight-time is only 0.6 seconds (180ft / 300 fps).
You hit the goat on a good shot with a lighter 300fps arrow it'll go down.
Marginal shot with a lighter arrow, less momentum, on a bone hit? *shrug* It depends.
You hit it with 1000 grains and you'll probably knock it straight off it's feet and obliterate whatever bone(s) you just hit.
For me, personally? Well, I just got a new rig and built some new arrows. Haven't even shot them yet. I used to have 414gr arrows out of an older mid-90s bow but never hunted.
I now have a Nitrium LD (32" draw) with 80lb limbs (turned down a touch, I cannot quite pull 80 yet ... =D) The arrows I built are 30" Kinetic Kaos .200 with 75gr HIT inserts. Total arrow weight, without head, is 458 grains. Since I have such a long draw and high poundage I have to run super-stiff arrows anyways, but that also gives me the flexibility to run widely varied tips. I can run 130gr for a finished weight of 588 grains. I also have some 2-blade 300gr heads (Tuffhead 225 + 75gr screwsert) to get up to 758.
I haven't shot them yet, and won't even get a chance to until mid-next week. It will be interesting to chrono them for real, but similar arrows (777 gr) out of other recent bows (shorter draw length, less weight) are still in the 220 fps on the chrono. I'm hoping to be in the 280 range with the lighter heads and 250s with the heavier ones, but my setup is a bit on the extreme end due to my size.
TL;DR: Don't worry about what anyone else is using. Figure out what your own goals are and play around with the online calculators.
Do you have a rangefinder? That makes a difference.
Do you hunt open country or dense woods with lots of branches? That makes a difference.
Are you hunting blacktail or pigs or elk or moose or cape buffalo .. or rabbit? That makes a difference.
This article is a couple of years old now:
"In most cases a well-placed arrow of any weight will get the job done, but when things go wrong and your arrow misses it’s mark by a few inches, that’s when arrow weight shows it’s true importance. So for this reason, I always shoot the heaviest arrow I can and still achieve a speed of 280 fps.
With my current bow and arrow set up, I am able to produce of speed of 286 FPS with an arrow weight of 488 grains. If you use the calculation for kinetic energy (Arrow weight x Velocity squared, divided by 450240), this combination gives me 89 foot-pounds of kinetic energy, a lethal combination for any North American animal." -Aron Snyder: http://www.rokslide.com/2012-01-09-05-12-00/archery/139-arrow-weight-setups
He's also stated "I like seeing an animal with a shock wave like it got hit with a 50 cal BMG." Though he usually runs a > 80 lb bow. So, more grains of salt on setups/rigs/target-numbers.
More recently he's been running 529gr arrows.
This is an excellent podcast series (highly recommended) and this episode is where they cover some gear and setups.
http://www.grittybowmen.com/gritty-podcasts-blog/2015/8/9/episode-23-do-you-even-shoot-bro
Find the FPS you're happiest with as a minimum. Then figure out how to build the heaviest, highest FOC arrow you can at that speed. You'll hit bow limits, your limits, physics limits, etc.
But in the end, a good shot is a good shot and the extra momentum is insurance or for much larger, tougher game. Or if you like to see things fall over like they were just hit by a .50 BMG.
-mox
On one end of the spectrum: with a perfect shot you need enough momentum to push through the soft-tissue a deer. That's not very much ... 45 lbs recurve with wooden arrows.
On the other end: a terrible shot where you need to blow through the ribs and shoulder of an African Cape Buffalo. 100lbs @ 20 yards with 1200gr.
The question is, what are you shooting? A moose-arrow is (probably) not the same arrow you're going to use on the open plains for antelope. Or pigs. Though it might be. No reason you couldn't shoot a 700 gr arrow at a speed-goat ... if you can get close enough.
On the open range, maybe speed matters. Maybe you don't want a 0.9 second flight time at 60 yards. (180ft / 200 fps) Maybe you're okay with it. Maybe you think "antelope are pretty small, with a lighter bone-structure ... I want to go to 300fps so the flight-time is only 0.6 seconds (180ft / 300 fps).
You hit the goat on a good shot with a lighter 300fps arrow it'll go down.
Marginal shot with a lighter arrow, less momentum, on a bone hit? *shrug* It depends.
You hit it with 1000 grains and you'll probably knock it straight off it's feet and obliterate whatever bone(s) you just hit.
For me, personally? Well, I just got a new rig and built some new arrows. Haven't even shot them yet. I used to have 414gr arrows out of an older mid-90s bow but never hunted.
I now have a Nitrium LD (32" draw) with 80lb limbs (turned down a touch, I cannot quite pull 80 yet ... =D) The arrows I built are 30" Kinetic Kaos .200 with 75gr HIT inserts. Total arrow weight, without head, is 458 grains. Since I have such a long draw and high poundage I have to run super-stiff arrows anyways, but that also gives me the flexibility to run widely varied tips. I can run 130gr for a finished weight of 588 grains. I also have some 2-blade 300gr heads (Tuffhead 225 + 75gr screwsert) to get up to 758.
I haven't shot them yet, and won't even get a chance to until mid-next week. It will be interesting to chrono them for real, but similar arrows (777 gr) out of other recent bows (shorter draw length, less weight) are still in the 220 fps on the chrono. I'm hoping to be in the 280 range with the lighter heads and 250s with the heavier ones, but my setup is a bit on the extreme end due to my size.
TL;DR: Don't worry about what anyone else is using. Figure out what your own goals are and play around with the online calculators.
Do you have a rangefinder? That makes a difference.
Do you hunt open country or dense woods with lots of branches? That makes a difference.
Are you hunting blacktail or pigs or elk or moose or cape buffalo .. or rabbit? That makes a difference.
This article is a couple of years old now:
"In most cases a well-placed arrow of any weight will get the job done, but when things go wrong and your arrow misses it’s mark by a few inches, that’s when arrow weight shows it’s true importance. So for this reason, I always shoot the heaviest arrow I can and still achieve a speed of 280 fps.
With my current bow and arrow set up, I am able to produce of speed of 286 FPS with an arrow weight of 488 grains. If you use the calculation for kinetic energy (Arrow weight x Velocity squared, divided by 450240), this combination gives me 89 foot-pounds of kinetic energy, a lethal combination for any North American animal." -Aron Snyder: http://www.rokslide.com/2012-01-09-05-12-00/archery/139-arrow-weight-setups
He's also stated "I like seeing an animal with a shock wave like it got hit with a 50 cal BMG." Though he usually runs a > 80 lb bow. So, more grains of salt on setups/rigs/target-numbers.
More recently he's been running 529gr arrows.
This is an excellent podcast series (highly recommended) and this episode is where they cover some gear and setups.
http://www.grittybowmen.com/gritty-podcasts-blog/2015/8/9/episode-23-do-you-even-shoot-bro
Find the FPS you're happiest with as a minimum. Then figure out how to build the heaviest, highest FOC arrow you can at that speed. You'll hit bow limits, your limits, physics limits, etc.
But in the end, a good shot is a good shot and the extra momentum is insurance or for much larger, tougher game. Or if you like to see things fall over like they were just hit by a .50 BMG.
-mox
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I was just curious what people thought a good momentum value is.
I have a workable setup right now, still some tuning I need to do. I haven't reached my balance of arrow weight and FPS
Specs:
Nitrium Turbo maxed out 67lbs (I need to get it tuned so I am at least pulling 70lbs I really want 73lbs)
Goldtip velocities 460gr 18% FOC
285 FPS- Chronographed
I have a workable setup right now, still some tuning I need to do. I haven't reached my balance of arrow weight and FPS
Specs:
Nitrium Turbo maxed out 67lbs (I need to get it tuned so I am at least pulling 70lbs I really want 73lbs)
Goldtip velocities 460gr 18% FOC
285 FPS- Chronographed
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