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Old 04-27-2018, 11:56 AM   #1
canny
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Default Interesting Observation

I want to start by saying this just an observation and by far from any form of sophisticated scientific test. In my other thread I was discussing building a heavy high FOC arrow for my Sept elk hunt. So I ended up building a 26.5" CE Maxima 350 with 100g insert and 100g tip giving me a total weight of around 490g (don't remember exact) and around 16% FOC. I started shooting these arrows in the back yard and noticed something interesting. The sights on my bow were previously set up for my 28" standard Axis arrows. I think these arrows weighed in around 390g. No doubt my initial velocity was slower with the 500g arrows than the 390g, but what was eye opening was how much I had to change my pins.

20 yard pin = no change

30 yard pin = no change

40 yard pin = moved it up

50 yard pin = moved it up

60 yard pin = moved it up

This meant that despite the lower FPS at the bow the heavier arrow demonstrated a slightly better trajectory than the lighter 390g arrow at a higher velocity. I am guessing this is do to the weight factor resisting gravity allowing for slightly less drop.

Maybe something to ponder on....
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Old 04-27-2018, 12:05 PM   #2
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maybe it's a retained velocity thing.
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Old 04-27-2018, 01:22 PM   #3
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That’s interesting!
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Old 04-29-2018, 09:20 AM   #4
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Good observation. I believe some of the trad guys have noticed this too and kind of like a spring board effect...?

Thanks for sharing.
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Old 04-29-2018, 12:32 PM   #5
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This is one that if the light arrow people would test would realize they don’t loose when increasing mass. Or when increasing a lot it’s not much lost.

Friend was playing around the other day with his 550 and a 800 gr arrow. He only lost 10 yards. Meaning he was using his 50 yard pin for 40 yard shot with the 800 gr arrow.

Nice job
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Old 04-29-2018, 01:05 PM   #6
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I would like to see the math on how a heavier objects resists a constant force like gravity. Seems impossible.

Don't ge me wrong, because im not saying it didn't happen, but mathematically it shouldn't.
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Old 04-29-2018, 01:36 PM   #7
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Three seasons ago I jumped up to a 560ish grain arrow. This was more than a 120 grain increase. I did not see a change in my point of impact till outside of 40 yards. I passed tjis observation around at the time and several others chimed in that they had similar experiences. It makes since to me that your bow is performing more efficiently pushing a heavier projectile. This is also why your shots are noticeably quieter (at least mine are).
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Old 04-29-2018, 02:02 PM   #8
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Originally Posted by bowhuntntxn View Post
I would like to see the math on how a heavier objects resists a constant force like gravity. Seems impossible.

Don't ge me wrong, because im not saying it didn't happen, but mathematically it shouldn't.
I'd say momentum and wind resistance. When you double your arrow weight, you're not halving the speed (at most, you're quartering it), so your momentum increases while wind resistance stays the same. Additionally, if longer arrows are being used to achieve that weight, that should reduce your drag coefficient.

I would be interested in seeing a velocity x mass curve for a bow. I'd wager it doesn't follow a standard KE curve because the limbs are pre-loaded, and it'd be cool to find out at what weight arrow a bow is most efficient.
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Old 04-30-2018, 12:22 PM   #9
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Originally Posted by sir shovelhands View Post
I'd say momentum and wind resistance. When you double your arrow weight, you're not halving the speed (at most, you're quartering it), so your momentum increases while wind resistance stays the same. Additionally, if longer arrows are being used to achieve that weight, that should reduce your drag coefficient.

I would be interested in seeing a velocity x mass curve for a bow. I'd wager it doesn't follow a standard KE curve because the limbs are pre-loaded, and it'd be cool to find out at what weight arrow a bow is most efficient.
My apa was still climbing at 1100 gr
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Old 04-30-2018, 02:01 PM   #10
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My apa was still climbing at 1100 gr
Maaaan that's some weight; are you slaying dragons with that ballista?
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Old 04-30-2018, 02:18 PM   #11
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Why would you use a heavier arrow to go elk hunting?

Usually Kinetic energy is lost with an heavier arrow?

Look at it this way: would it be easier to stop a finishing nail at 400 fps or a railroad spike at 300 fps?

Just a thought...
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Old 04-30-2018, 03:02 PM   #12
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Originally Posted by TENRMORE View Post
Why would you use a heavier arrow to go elk hunting?

Usually Kinetic energy is lost with an heavier arrow?

Look at it this way: would it be easier to stop a finishing nail at 400 fps or a railroad spike at 300 fps?

Just a thought...
Backwards you think......
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Old 04-30-2018, 06:45 PM   #13
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If you didn't re-tune for it, the maxima is a larger diameter than the axis effectively raising the centerline of the arrow making it leave the bow "higher" than the Axis.
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Old 04-30-2018, 06:49 PM   #14
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Quote:
Originally Posted by TENRMORE View Post
Why would you use a heavier arrow to go elk hunting?

Usually Kinetic energy is lost with an heavier arrow?

Look at it this way: would it be easier to stop a finishing nail at 400 fps or a railroad spike at 300 fps?

Just a thought...
I don't want to stop either one, but there's a reason people don't go after cape buffalo with a 22-250.
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Old 05-01-2018, 03:13 AM   #15
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Quote:
Originally Posted by TENRMORE View Post
Why would you use a heavier arrow to go elk hunting?

Usually Kinetic energy is lost with an heavier arrow?

Look at it this way: would it be easier to stop a finishing nail at 400 fps or a railroad spike at 300 fps?

Just a thought...
Momentum, not kinetic energy, is what's important when punching through an animal. Same reason people use heavy, slower bullets on dangerous game.
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Old 05-01-2018, 07:13 AM   #16
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Originally Posted by sir shovelhands View Post
Maaaan that's some weight; are you slaying dragons with that ballista?
Haha no dragons.

I was testing efficiency of the bow
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Old 05-01-2018, 12:31 PM   #17
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Quote:
Originally Posted by TENRMORE View Post
Why would you use a heavier arrow to go elk hunting?

Usually Kinetic energy is lost with an heavier arrow?

Look at it this way: would it be easier to stop a finishing nail at 400 fps or a railroad spike at 300 fps?

Just a thought...
Yeah as mentioned you might need to rethink this. Trad guys have it figured out and have been for years. Heavy arrows with high FOC generate more momentum and therefore perform very well at low velocities. I came around to the idea that velocity is not something I'm even remotely concerned about. There are no true benefits, IMO to slinging a light arrow at game. Is it faster...yes, is it faster than the speed of sound...no. Therefore, the game can still hear the shot and possibly duck the string. Heavy arrows absorb more of the bows energy therefore the shot is quieter, high FOC arrows typically tune better with fixed blades, and then there is the momentum factor that allows the arrows weight to aid in the penetration.
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Old 05-01-2018, 01:17 PM   #18
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Quote:
Originally Posted by TENRMORE View Post
Why would you use a heavier arrow to go elk hunting?

Usually Kinetic energy is lost with an heavier arrow?

Look at it this way: would it be easier to stop a finishing nail at 400 fps or a railroad spike at 300 fps?

Just a thought...
I can tell you this, I would much rather get hit with a 400 fps finishing nail then a 300 fps railroad spike. That finishing nail might stop if it hits a major bone but that railroad spike is going to shatter it and keep going.
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Old 05-01-2018, 02:12 PM   #19
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I'm by no means an archery expert, but weight has nothing to do with gravity. Two objects of different weights will drop at the same rate (not factoring in wind). The only way for a heavier/slower arrow to hit higher than a lighter/faster arrow is because the heavier arrow retained speed better.

Think of it like this, you drop both arrows and they hit the ground at the same time. Lets say it takes 1 second. Even when the arrows are shot (assuming they are shot level) they will still both hit the ground in 1 second (unless there is some form of lift from the vanes, which I doubt there is). So the arrow that travels farther in that 1 second will have a shallower trajectory. If the heavier arrow retains speed better than the lighter arrow, it very well could have a flatter trajectory.

This is thinking of it in terms of bullet ballistics, but it should be a close approximation.
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Old 05-01-2018, 03:38 PM   #20
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Originally Posted by bowhuntntxn View Post
I would like to see the math on how a heavier objects resists a constant force like gravity. Seems impossible.

Don't ge me wrong, because im not saying it didn't happen, but mathematically it shouldn't.
I think it's called "momentum".
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Old 05-03-2018, 09:51 AM   #21
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Quote:
Originally Posted by TENRMORE View Post
Why would you use a heavier arrow to go elk hunting?

Usually Kinetic energy is lost with an heavier arrow?

Look at it this way: would it be easier to stop a finishing nail at 400 fps or a railroad spike at 300 fps?

Just a thought...
Finishing nail:
50 grains @ 400 FPS = 0.0887 slugs (momentum) & 17.75 Ke

Railroad spike:
7000 grains @ 300 FPS = 9.317 slugs (momentum) & 1397.52 Ke

Definitely easier to stop a finishing nail at these numbers (momentum).
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Old 05-03-2018, 10:05 AM   #22
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Originally Posted by JustinJ View Post
I'm by no means an archery expert, but weight has nothing to do with gravity. Two objects of different weights will drop at the same rate (not factoring in wind). The only way for a heavier/slower arrow to hit higher than a lighter/faster arrow is because the heavier arrow retained speed better.

Think of it like this, you drop both arrows and they hit the ground at the same time. Lets say it takes 1 second. Even when the arrows are shot (assuming they are shot level) they will still both hit the ground in 1 second (unless there is some form of lift from the vanes, which I doubt there is). So the arrow that travels farther in that 1 second will have a shallower trajectory. If the heavier arrow retains speed better than the lighter arrow, it very well could have a flatter trajectory.

This is thinking of it in terms of bullet ballistics, but it should be a close approximation.
A very good approximation.

Back when I was debating the use of vanes over feathers the consensus was that feathers were faster out of the hole than vanes, but that vanes caught up in speed at about 30 yards.

Even though we are talking about weight vs. drag (in my experiment) the results would be the same, but opposite, as Canny. IOW, the close range pins would move up and the long range pins would stay the same if we started with vanes for sighting in (which I did).

What I found was pretty close to what everyone believed, and well within the margin of error for different bows. IIRC the difference in the two up close was a mere 12(ish) FPS and the vanes caught up in about 35 yards.

The vanes, even though they were heavier, retained their speed better (due to less drag) than the feathers resulting in a flatter trajectory. Not by much, but it was there; mathematically anyway.

So, in my experiment the heavier arrow (by about 15 gr) actually hit the same spot and the lighter arrow hit low at distance beyond 40 yards or so.

It's not just about the weight. The arrow is a dynamic system in and of itself; everything must be considered and gravity isn't the only force acting on an arrow in flight.
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Old 05-03-2018, 10:11 PM   #23
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llll
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Old 05-03-2018, 10:12 PM   #24
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Originally Posted by Rat View Post
A very good approximation.

Back when I was debating the use of vanes over feathers the consensus was that feathers were faster out of the hole than vanes, but that vanes caught up in speed at about 30 yards.

Even though we are talking about weight vs. drag (in my experiment) the results would be the same, but opposite, as Canny. IOW, the close range pins would move up and the long range pins would stay the same if we started with vanes for sighting in (which I did).

What I found was pretty close to what everyone believed, and well within the margin of error for different bows. IIRC the difference in the two up close was a mere 12(ish) FPS and the vanes caught up in about 35 yards.

The vanes, even though they were heavier, retained their speed better (due to less drag) than the feathers resulting in a flatter trajectory. Not by much, but it was there; mathematically anyway.

So, in my experiment the heavier arrow (by about 15 gr) actually hit the same spot and the lighter arrow hit low at distance beyond 40 yards or so.

It's not just about the weight. The arrow is a dynamic system in and of itself; everything must be considered and gravity isn't the only force acting on an arrow in flight.

i like that
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Old 05-03-2018, 10:43 PM   #25
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Quote:
Originally Posted by Rat View Post
Finishing nail:
50 grains @ 400 FPS = 0.0887 slugs (momentum) & 17.75 Ke

Railroad spike:
7000 grains @ 300 FPS = 9.317 slugs (momentum) & 1397.52 Ke

Definitely easier to stop a finishing nail at these numbers (momentum).
FYI, slugs are not a unit of momentum, they're a unit of mass. Momentum units are slug*ft/s or kg*m/s.
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Old 05-03-2018, 10:45 PM   #26
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if you put your bow in a hooter shooter and aim it at the same spot the heavier arrow will shoot lower every time at every range. there is really no valid argument assuming fundamental equivalence of the arrows other than weight.

heavier arrows will retain a % of initial speed downrange better than a lighter arrow but they start slower so still will drop more by comparison with a lighter arrow at any range.

Last edited by Tom; 05-03-2018 at 10:59 PM.
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Old 05-03-2018, 10:50 PM   #27
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FYI, slugs are not a unit of momentum, they're a unit of mass. Momentum units are slug*ft/s or kg*m/s.
yes I'm sure rat knows its slug-ft/s
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Old 05-03-2018, 11:33 PM   #28
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yes I'm sure rat knows its slug-ft/s
Slugs, lbm, and lbf is a great example of why imperial units are terrible.
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Old 05-04-2018, 02:05 PM   #29
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Originally Posted by Tom View Post
if you put your bow in a hooter shooter and aim it at the same spot the heavier arrow will shoot lower every time at every range. there is really no valid argument assuming fundamental equivalence of the arrows other than weight.

heavier arrows will retain a % of initial speed downrange better than a lighter arrow but they start slower so still will drop more by comparison with a lighter arrow at any range.
That's funny cause this past weekend I was shooting with my step-dad. His bow is tuned to his light 380g Gold Tip arrow (very similar OD as my CE Maxima Reds) and when I let him shoot my heavy 495g arrows they were all in the same group. No statistical difference in elevation at 20 yards.

How does that fit into your statement about heavier arrows shooting lower every time at EVERY range?
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Old 05-04-2018, 02:09 PM   #30
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Quote:
Originally Posted by Tom View Post
if you put your bow in a hooter shooter and aim it at the same spot the heavier arrow will shoot lower every time at every range. there is really no valid argument assuming fundamental equivalence of the arrows other than weight.

heavier arrows will retain a % of initial speed downrange better than a lighter arrow but they start slower so still will drop more by comparison with a lighter arrow at any range.
Not so.

If I build two identical arrows in weight, but one has flu-flu vanes, the flu-flu arrow will not hit the same spot.

The increased drag from the flu-flu vanes will cause the arrow to slow down much faster.

Weight isn't everything...
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Old 05-04-2018, 05:28 PM   #31
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Not so.

If I build two identical arrows in weight, but one has flu-flu vanes, the flu-flu arrow will not hit the same spot.

The increased drag from the flu-flu vanes will cause the arrow to slow down much faster.

Weight isn't everything...
I agree 100% with you but those arrows do not have a "fundamental equivalence" and you are factoring drag into the equation.
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Old 05-04-2018, 05:29 PM   #32
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That's funny cause this past weekend I was shooting with my step-dad. His bow is tuned to his light 380g Gold Tip arrow (very similar OD as my CE Maxima Reds) and when I let him shoot my heavy 495g arrows they were all in the same group. No statistical difference in elevation at 20 yards.

How does that fit into your statement about heavier arrows shooting lower every time at EVERY range?
yes every range will be lower and at 20 yards the difference will be small. It is math. Gravity is constant. A heavier arrow is slower so will drop more at every range.
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Old 05-04-2018, 09:03 PM   #33
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Quote:
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yes every range will be lower and at 20 yards the difference will be small. It is math. Gravity is constant. A heavier arrow is slower so will drop more at every range.


Since you brought up math Iíll throw out statistics. Statistically there is no significant different in the drop of both arrows at 20 yards. To simplify if something drops 2Ē at a certain distance and another drops 2.1Ē then mathematically you could say that the latter drops more, but statistically the drop is insignificant so therefore they are the same.


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Old 05-04-2018, 09:12 PM   #34
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no...it is measureable which is why I mentioned using a shooting device like a hooter shooter so that the aiming point is consistent. Human error is variable when measuring anything...I am not trying to start an argument. You mentioned that perhaps the heavy arrow resisted gravity which is why your point is valid. You could be correct but it is not what I believe to be true. either way...if you are hitting your target you are ready for hunting season!

Last edited by Tom; 05-04-2018 at 09:32 PM.
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Old 05-04-2018, 10:13 PM   #35
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no...it is measureable which is why I mentioned using a shooting device like a hooter shooter so that the aiming point is consistent. Human error is variable when measuring anything...I am not trying to start an argument. You mentioned that perhaps the heavy arrow resisted gravity which is why your point is valid. You could be correct but it is not what I believe to be true. either way...if you are hitting your target you are ready for hunting season!
Two arrows with the same dimensions, fired from the same angle and from the same height will hit the ground at the same time, regardless of differences in weight, since you don't build up enough vertical velocity to make drag a big factor.

However, in the horizontal direction, you have great enough velocity to factor in drag. And there's two strikes against light arrows: the first being that you start out with a lower momentum than a heavier arrow, the second is that drag is proportional to the square of velocity, meaning the drag force is much higher on something going fast.

So in the short time of arrow flight that you have, it's mathematically possible that the lighter arrow will at some point be travelling at the same velocity as the heavier arrow (assuming they both don't hit the ground first). And it will continue to lose speed more quickly than the heavy arrow because of the difference in momentum. Now if the heavy arrows has adequate flight time, it can make up the distance between the two as the velocity gap between them widens.

I'd do the math to show an example, but the impulse due to drag is a PITA to calculate since it's a function of velocity, and velocity is a function of drag.

Though a simple example would be playing golf with a ping pong ball vs a golf ball. Both have nearly identical radii, and while the ping pong ball's initial velocity will be much higher when you hit it, it won't go nearly as far as the golf ball.
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Old 05-04-2018, 10:46 PM   #36
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Two arrows with the same dimensions, fired from the same angle and from the same height will hit the ground at the same time, regardless of differences in weight, since you don't build up enough vertical velocity to make drag a big factor.

However, in the horizontal direction, you have great enough velocity to factor in drag. And there's two strikes against light arrows: the first being that you start out with a lower momentum than a heavier arrow, the second is that drag is proportional to the square of velocity, meaning the drag force is much higher on something going fast.

So in the short time of arrow flight that you have, it's mathematically possible that the lighter arrow will at some point be travelling at the same velocity as the heavier arrow (assuming they both don't hit the ground first). And it will continue to lose speed more quickly than the heavy arrow because of the difference in momentum. Now if the heavy arrows has adequate flight time, it can make up the distance between the two as the velocity gap between them widens.

I'd do the math to show an example, but the impulse due to drag is a PITA to calculate since it's a function of velocity, and velocity is a function of drag.

Though a simple example would be playing golf with a ping pong ball vs a golf ball. Both have nearly identical radii, and while the ping pong ball's initial velocity will be much higher when you hit it, it won't go nearly as far as the golf ball.
I agree with everything you say as it is simple physics....all but the comparison of a ping pong ball and a golf ball with respect to archery. This does not equate in this situation.
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Old 05-04-2018, 11:29 PM   #37
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I agree with everything you say as it is simple physics....all but the comparison of a ping pong ball and a golf ball with respect to archery. This does not equate in this situation.
I could have used an example of any two objects of similar size, different weights, and different speeds as an example, because the equations for motion are the same regardless. It's just easier for people to grasp that even though a ping pong ball will move with a faster initial velocity, and be the same size as a golf ball, it won't go as far because of its lower momentum.
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Old 05-07-2018, 05:23 PM   #38
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Lots of info here. Thank y’all
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Old 05-07-2018, 09:31 PM   #39
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Heavy arrows with high FOC generate more momentum.........


Just keep in mind that the FOC has no bearing on momentum. The momentum is a function the relationship between mass and velocity, is static and cares not for FOC percentages. There are plenty of guys getting high momentum numbers simply off shaft weight, take the FMJ for and example. It can quickly run mass weight up in a hurry; however is not conducive to building above average FOC in most situations.


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Old 05-17-2018, 01:18 PM   #40
equyst
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Join Date: Apr 2018
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Thatís interesting!thanks for sharing
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