ARROW SPEED

eric

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If I increase my arrow speed by increasing poundage AND reducing the arrow length is there any formula or rule of thumb that can be used so that the arrow spine remains the same. i.e. If bow poundage is up 2lb how much can I shorten the arrow. or if I shorten the arrow by 1 half inch how much must the poundage be increased to keep the same spine.
Arrows are ACE's 27 3/4" long 720s. Any ideas will much appreciated.
 

Timid Toad

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Your best bet is probably the Easton arrow selection chart. It's only a guide of course, but it would be a start. Then you'll need to play to regain tune.
 

Rik

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The Easton charts seem to suggest that 1 inch is approximately 5 pounds of weight. But it's very rough.
And of course, the spine of the shafts doesn't change when you shorten them... It's just that shorter arrows of the same spine match a different setup...
 

callummac

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I thought that the longer the arrow was the more time there is for the force acting on the arrow to accelerate it to a higher velocity.

Would that mean that even though you get more force acting on it from the higher poundage, by reducing the arrow length that force has less time to act on the arrow?

I realise regardless you would have a gain in force due to the higher poundage, but would it not be better to keep your arrow length the same and increase the poundage instead?
 
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Timid Toad

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But why would you shoot a longer arrow than you needed to? More weight will reduce speed leaving the bow. But more weight will carry greater momentum at the longer distances.
It is a trade off, but it depends on what the OP is trying to achieve.
 

blakey

Active member
If I increase my arrow speed by increasing poundage AND reducing the arrow length is there any formula or rule of thumb that can be used so that the arrow spine remains the same. i.e. If bow poundage is up 2lb how much can I shorten the arrow. or if I shorten the arrow by 1 half inch how much must the poundage be increased to keep the same spine.
Arrows are ACE's 27 3/4" long 720s. Any ideas will much appreciated.
If you want to increase arrow speed then the easiest way is to get lighter arrows. That way you don't have to mess with length or spine? I believe Carbon Ones are lighter than ACEs. Of course if you really want to accelerate McKinneys are the way to go. Cheers
 

callummac

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But why would you shoot a longer arrow than you needed to? More weight will reduce speed leaving the bow. But more weight will carry greater momentum at the longer distances.
It is a trade off, but it depends on what the OP is trying to achieve.
Apologies, I must have misunderstood what the OP was trying to achieve. I was of the understanding that he was already shooing a specific length of arrow and that he is planning to reduce that length and increase poundage to increase arrow velocity.

I didn't realise his current arrows were too long for him.

Apologies all.
 

Timid Toad

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I don't know whether the arrows are *too* long either! Just if you have room and stamina to wind up the bow and enough on the clicker plate to take some off the arrow length then why not? I spend a lot of time messing about with arrow lengths and point lengths to find the best combination for me, but I am looking for something very specific: tune and groups at 70m.

Apologies, I must have misunderstood what the OP was trying to achieve. I was of the understanding that he was already shooing a specific length of arrow and that he is planning to reduce that length and increase poundage to increase arrow velocity.

I didn't realise his current arrows were too long for him.

Apologies all.
 

Rik

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I thought that the longer the arrow was the more time there is for the force acting on the arrow to accelerate it to a higher velocity.

Would that mean that even though you get more force acting on it from the higher poundage, by reducing the arrow length that force has less time to act on the arrow?

I realise regardless you would have a gain in force due to the higher poundage, but would it not be better to keep your arrow length the same and increase the poundage instead?
What a weird idea... Assuming the same length of draw and arrow weight a longer arrow doesn't make any difference.
Given extra weight the shaft spends longer on the string and picks up a little more energy, but you'd get that from a heavier point or shaft, and it wouldn't translate to higher arrow speed, just better momentum...
If the longer arrow meant a longer draw, then that's different.
But on its own...?
 

callummac

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What a weird idea... Assuming the same length of draw and arrow weight a longer arrow doesn't make any difference.
Given extra weight the shaft spends longer on the string and picks up a little more energy, but you'd get that from a heavier point or shaft, and it wouldn't translate to higher arrow speed, just better momentum...
If the longer arrow meant a longer draw, then that's different.
But on its own...?
Longer arrow, longer draw is basically what I am getting at.
 

eric

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Many thanks for all the replies but I am still not clear if I can achieve what I am looking for. My original post was perhaps not detailed enough so I will try to explain in more detail. Again many thanks for your patience.
My current set up is Arrow length from nock throat to end of shaft 28 1/8" ( Sorry for earlier error) and they could be reduced by 5/8". My arrows are ACE,s 720s. My limbs are W&W Ex Power 30lb @ 28 ". My limb poundage is set at the middle position. I am shooting at a decent 1st class level and want to achieve Bowman but @ 90m/100yds I am at the extreme of my set up and my "groups" are very wide in the bottom half of the target and the green. OK I could aim above the gold but find this unsatisfactory. If the arrow is shortened by 5/8" this will stiffen the arrow and if the poundage is increased this will weaken the arrow The question is by how much to keep the same balance. Both actions should increase the arrow speed and move the groups higher and tighter. Is my reasoning OK or might X10s be the answer. Using higher poundage limbs is not an option.
 

backinblack

Active member
X10s is definitely not the answer - they weigh more than ACEs and will give worse sight marks than you already have. Knocking 5/8 inch off your arrows will not save an awful lot in weight at 6.4 grains per inch for a 720 ACE. In my experience 10 grains at 90m is about half a target difference in cast so you are still struggling I think.

You can always try winding up the limbs to the max and seeing what effect that has on sight marks before you trim your arrows. Alternatively, you can look elsewhere for an improvement in cast: make sure your nocking point isn't too high, shoot a platform tab, use a modern string material if you don't already (8125, Fastflight+), lighter point weight in arrows, spin wing vanes are lighter than normal fletches, dont shoot pin nocks. I'm sure others can add to this list.

Best,
Backinblack
 

Tuck

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Agree with Backinblack, using a shelf tab to increase the arrow to eye would probably be the most effect , also reducing point weight could be tried, if you are using higher point weights.



Eat, Drink, Shoot, Enjoy.
 

Ar-Pe-Lo

Member
Many thanks for all the replies but I am still not clear if I can achieve what I am looking for. My original post was perhaps not detailed enough so I will try to explain in more detail. Again many thanks for your patience.
My current set up is Arrow length from nock throat to end of shaft 28 1/8" ( Sorry for earlier error) and they could be reduced by 5/8". My arrows are ACE,s 720s. My limbs are W&W Ex Power 30lb @ 28 ". My limb poundage is set at the middle position. I am shooting at a decent 1st class level and want to achieve Bowman but @ 90m/100yds I am at the extreme of my set up and my "groups" are very wide in the bottom half of the target and the green. OK I could aim above the gold but find this unsatisfactory. If the arrow is shortened by 5/8" this will stiffen the arrow and if the poundage is increased this will weaken the arrow The question is by how much to keep the same balance. Both actions should increase the arrow speed and move the groups higher and tighter. Is my reasoning OK or might X10s be the answer. Using higher poundage limbs is not an option.
As a rough guess if you shorten arrows by 1/2 inch, you need to wound limbs in by 2#......given your arrows are curently tuning well....

Not sure if this will be enough.....at this poundage I would either look at lighter arrows (McKinneys) or faster limbs (Border Hex-6)....
 

Rik

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Depending on exactly what poundage you're shooting, you might be able to get a match with ACE 670s, which would drop your arrow weight (quirk of the way the ACE shaft sizes work).
Another option might be to drop your nocking point a mm or so. That can add significant height at long ranges. Just don't overdo it.

But with all these options it's difficult to be definitive without seeing the actual setup in action...
 

Whitehart

Well-known member
So many questions

66" or 68" bow?
Point weight in the ACE's?
Type of tab?
Type of string?
Weight on fingers at full draw?
Nocking point height?
Tiller?
 

jerryRTD

Well-known member
Many thanks for all the replies but I am still not clear if I can achieve what I am looking for. My original post was perhaps not detailed enough so I will try to explain in more detail. Again many thanks for your patience.
My current set up is Arrow length from nock throat to end of shaft 28 1/8" ( Sorry for earlier error) and they could be reduced by 5/8". My arrows are ACE,s 720s. My limbs are W&W Ex Power 30lb @ 28 ". My limb poundage is set at the middle position. I am shooting at a decent 1st class level and want to achieve Bowman but @ 90m/100yds I am at the extreme of my set up and my "groups" are very wide in the bottom half of the target and the green. OK I could aim above the gold but find this unsatisfactory. If the arrow is shortened by 5/8" this will stiffen the arrow and if the poundage is increased this will weaken the arrow The question is by how much to keep the same balance. Both actions should increase the arrow speed and move the groups higher and tighter. Is my reasoning OK or might X10s be the answer. Using higher poundage limbs is not an option.
If higher poundage limbs are not an option due to physical limitations then perhapps the time has come to go the dark side. A compound bow would give you all the power and arrow speed you need.
 
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gster123

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Does the spine not change according to the barrel shape on ACEs and X10 and the cut as the spine is an average for a set weight and length?
 
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