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Interesting...

Nutterbuster said:
Can you clarify something for a dumb redneck? I'm reading your post as saying that your pin gap tightened as you went further out. Is that right?
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That’s correct...my pin gaps from 50-70 were closer together than they were from 20-40...weird, I know
 
Same principle as high ballistic coefficient bullets such as the 6.5 creedmoor? Simply retains its starting speed longer
 
rhagenw said:
Same principle as high ballistic coefficient bullets such as the 6.5 creedmoor? Simply retains its starting speed longer
Click to expand...
I believe you are correct. That’s what I’ve pieced together thus far.
 
With my lighter arrows I got the weird spacing closer up. 10-20 is virtually no difference so I use the same pin. 20-30 was a sizable gap. The space between 30-40 and 40-50 were almost the same. Then my 50 and 60 pins were almost stacked. My heavier arrows straightened out gap the changes by basically moving the 30, 40, and 50 pins up so I can still shoot out to 60 with a fixed 5 pin.
 
Your 20-30 gap represents a 20" drop - If you settle your 20 yard pin on the bullseye at 30 yards, you'd hit 17" low.

Your 40-50 gap represents a 30" drop - If you settle your 40 yard pin on the bullseye at 50 yards, you'd hit 25" low.

Your 50-60 gap represents a 30" drop - If you settle your 60 yard pin on the bullseye at 70 yards, you'd hit 26" low.

Updated from 60/70 pin gap to 50-60 - i misread your notes. And to account for 36" eye to pin measurement.

This is all according to basic geometry, and assuming your pins are set very, very precisely, at the measurements you gave me.

I ran your stats in archerycalculator.com and come up with 255fps for arrow speed at bow. I built a bow with similar IBO in TAP and only get 245 at your specs. Update - i calculated at 70, your draw is 65. It's something more like 235 on speed.

Here's what I found on trajectory:

If you aim with 20 yard pin at 30, you'd see a 8" low hit.

If you aim with 40 yard pin at 50, you'd see a 17" low hit.

If you aim with 50 yard pin at 60, you'd see a 21" low hit.

Updated from 60/70 to 50/60 and 36" and new speed.

Your pin gaps seemed very big based on an initial guess, but I also haven't had a multi pin sight in a while. So I ran the geometry in reverse with the findings from TAP. This is based on the distance between your eye and the pin to be 30"(28" draw + pin 2" in front of riser).

Here's what I found: Updated to be 36" to account for your sight being so far in front of riser.

Your gap from 20-30 should be .234"

Your gap from 40-50 should be .280"

Your gap from 50-60 should be .332"

Updated from 60/70 to 50/60 and 36"


Anyone can do the basic geometry with a right triangle calculator. You just need the distance from eye to pin(side 1, divide your pin gap by 2(side 2). plug these in, with a right angle between them. You'll get an angle from eye to half of pin gap. Take that angle, replace distance from eye to pin with eye to target. Take the resulting side 2 measurement that comes out, multiply by 2, and this gives you the spread between your pins if you were to aim with each at the distance you chose.


I say all this to say something is quite off. Your pin gaps could theoretically get smaller as you progress in distance. But it would take a strange situation that i can't come up with one based in reality.


This is all a real headscratcher. The size of the pin gaps is strange too, they seem big.


Edit - I went in and changed 30 to 36 for distance to pin once you informed me that your sight was out 6" from riser, and the correct bow poundage.



Essentially, something seems way, way off, that your pin gaps are over 1/2" for any reason. Your bow is either shooting 180fps, or your measurements were wrong.
 
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kyler1945 said:
Your 20-30 gap represents a 20" drop - If you settle your 20 yard pin on the bullseye at 30 yards, you'd hit 20" low.

Your 40-50 gap represents a 30" drop - If you settle your 40 yard pin on the bullseye at 50 yards, you'd hit 30" low.

Your 60-70 gap represents a 37" drop - If you settle your 60 yard pin on the bullseye at 70 yards, you'd hit 36" low.

This is all according to basic geometry, and assuming your pins are set very, very precisely, at the measurements you gave me.

I ran your stats in archerycalculator.com and come up with 255fps for arrow speed at bow. I built a bow with similar IBO in TAP and only get 245 at your specs.

Here's what I found on trajectory:

If you aim with 20 yard pin at 30, you'd see a 7" low hit.

If you aim with 40 yard pin at 50, you'd see a 14" low hit.

If you aim with 60 yard pin at 70, you'd see a 21" low hit.



Your pin gaps seemed very big based on an initial guess, but I also haven't had a multi pin sight in a while. So I ran the geometry in reverse with the findings from TAP. This is based on the distance between your eye and the pin to be 30"(28" draw + pin 2" in front of riser).

Here's what I found:

Your gap from 20-30 should be .194"

Your gap from 40-50 should be .232"

Your gap from 60-70 should be .25"




Anyone can do the basic geometry with a right triangle calculator. You just need the distance from eye to pin(side 1, divide your pin gap by 2(side 2). plug these in, with a right angle between them. You'll get an angle from eye to half of pin gap. Take that angle, replace distance from eye to pin with eye to target. Take the resulting side 2 measurement that comes out, multiply by 2, and this gives you the spread between your pins if you were to aim with each at the distance you chose.


I say all this to say something is quite off. Your pin gaps could theoretically get smaller as you progress in distance. But it would take a strange situation that i can't come up with one based in reality.


This is all a real headscratcher. The size of the pin gaps is strange too, they seem big.


Edit - I went in and changed 30 to 34 for distance to pin, just to see how it would affect pin gap. This would be really long for your draw.

This is what I come up with:

20-30 .22"
40-50 .264"
60-70 .284"

Essentially, something seems way, way off, that your pin gaps are over 1/2" for any reason. Your bow is either shooting 180fps, or your measurements were wrong.
Click to expand...
So I read through this twice...wasn’t sure what to think, so I went out to cut some wood...thought some more...came in and read it again...still not sure what the takeaway is...I fully understand your process, but I believe there are a few things awry here

for starters, as far as the geometry goes, I torque tuned my bow and my POI was least affected with torque with my pins being 6” from the front of my riser...this is significantly further away from the riser than the 2” you used to calculate the numbers...im sure this explains the gapping issue that doesn’t make sense to you.

still unsure how to processthe fact that the pin gapping decreases “significantly” the further I move out.
 
MathewsMan7 said:
So I read through this twice...wasn’t sure what to think, so I went out to cut some wood...thought some more...came in and read it again...still not sure what the takeaway is...I fully understand your process, but I believe there are a few things awry here

for starters, as far as the geometry goes, I torque tuned my bow and my POI was least affected with torque with my pins being 6” from the front of my riser...this is significantly further away from the riser than the 2” you used to calculate the numbers...im sure this explains the gapping issue that doesn’t make sense to you.

still unsure how to processthe fact that the pin gapping decreases “significantly” the further I move out.
Click to expand...
your pin gap is smaller because the arrow looses less speed at slower speeds. Think of the arrow loosing 10% of speed every .1 second the arrow travels. Of course it looses most in the beginning,say go from 270 to 230. These numbers are just examples and this process is not linear but i cant do the math for a curve. so the next loss is 35 fps to 195. The next loss is 29. So the loss of speed,or drop is less further out. Makes sense to me.
 
Bowmanmike said:
your pin gap is smaller because the arrow looses less speed at slower speeds. Think of the arrow loosing 10% of speed every .1 second the arrow travels. Of course it looses most in the beginning,say go from 270 to 230. These numbers are just examples and this process is not linear but i cant do the math for a curve. so the next loss is 35 fps to 195. The next loss is 29. So the loss of speed,or drop is less further out. Makes sense to me.
Click to expand...
Ahhh...I get it...putting it that way makes more sense to me
 
MathewsMan7 said:
So I read through this twice...wasn’t sure what to think, so I went out to cut some wood...thought some more...came in and read it again...still not sure what the takeaway is...I fully understand your process, but I believe there are a few things awry here

for starters, as far as the geometry goes, I torque tuned my bow and my POI was least affected with torque with my pins being 6” from the front of my riser...this is significantly further away from the riser than the 2” you used to calculate the numbers...im sure this explains the gapping issue that doesn’t make sense to you.

still unsure how to processthe fact that the pin gapping decreases “significantly” the further I move out.
Click to expand...

6 for sight bar, 28 for draw, 2 for riser thickness, minus 2 inches for your anchor being behind your eye = 34”. Still shouldn’t be over 1/2” pin gaps - even if I’m 2-3” off in this measurement(we’re not). That’s why I ran It twice to show how small the differnce

can you take a picture of the measuring tape against your pin gaps?

Something’s off. We’ll get to the bottom of it haha!


Bowmanmike said:
your pin gap is smaller because the arrow looses less speed at slower speeds. Think of the arrow loosing 10% of speed every .1 second the arrow travels. Of course it looses most in the beginning,say go from 270 to 230. These numbers are just examples and this process is not linear but i cant do the math for a curve. so the next loss is 35 fps to 195. The next loss is 29. So the loss of speed,or drop is less further out. Makes sense to me.
Click to expand...

you’re not taking into consideration that the slower the arrow is traveling forward, the less resistance the arrow encounters as it accelerates downward due to gravity.

loss of speed is not the actual drop. Drop is drop. The rate of drop is constant, less losses due to resistance. Faster your arrow travels, the slower the rate of drop. Slower your arrow travels, faster the rate of drop.
 
updated the math a bit in my original post. Not much change though.

Do you have a big enough target to aim with your 20 yard pin on bullseye, at 30 yards, and record how low below the bullseye you hit?
 
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kyler1945 said:
loss of speed is not the actual drop. Drop is drop. The rate of drop is constant, less losses due to resistance. Faster your arrow travels, the slower the rate of drop. Slower your arrow travels, faster the rate of drop.
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Just wanted to simplify this a bit. The force downward from gravity is over time and not distance. Due to air resistance, it takes longer to cover each consecutive 10 yard increment meaning more drop per increment. But, the slower the arrow goes the less force there is from wind resistance, slowing the rate of decrease. This means theoretically the rate of drop for the arrow would become nearly constant as the amount of air resistance approaches zero; although, that would also mean the velocity of the arrow is approaching zero as well.

However, that does not completely explain the issue.

One thing we may have overlooked, what size pins do you have? With the the reference size of the target and a larger pin size it may be negotiable at that distance. Could be completely wrong, but just wanted to rule out all the options.
 
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