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Looking for a bit of advice from others who may have had similar experience or might know what’s going on.

Was using a 8125g string bought from reputable US string maker and had my ACE 670 tuned nicely with great arrow flight out to 70m, both bare and fletched. I use large groove nocks and fit was quite tight and arrow needed a bit of a yank to detach from string.

I just put a new string on made from Mercury (26 or 28 strands made locally by archery shop) and it was made to fit large groove nock and the nock fit has an audible click and doesn’t fall off the string when hanging freely but its no where near the tightness of the previous 8125g string. It would be considered loose when compared to the 8125.

8125 string setting was arrow point very close to centre shot and plunger around 7.0 medium beiter spring for straight arrow flight shooting 37.5lb @ 28.5”. Bow is aligned.

The problem I have with new string is that my arrows are flying horribly. At 11 metres, the bare shaft is at 45 degree angle into the target butt nock left but still within a couple of inches of fletched which are hitting close enough to the X (40cm face)and slo mo shows the arrows crooked flight all the way to target. Fletched are also slanted in target but not as extreme as bare shaft.

There is no arrow contact with rest or plunger at all. In order to get the bare and fletched to fly relatively straight out of bow, I have had to take 2.5 turns off limb bolts which is approx 3lb and also had to move centre shot 1 full arrow shaft width left of string but feels like it needs to go even further left which doesn’t seem correct as most using barrelled say close to dead centre is the go.

With the need to reduce draw weight and push center shot 1 full arrow width left of string and a stiffer plunger now improving but still not perfect bare or fletched flight, is this a case that my arrows were always weak but it was masked by tight nock fit or is there something else at play?

I want to get back to 37+ lb and have maybe 1/2” or arrow i can cut but dont know if thats going to be enough or the answer.

I’m guessing that the nock fit for the 8125 was not supposed to be so tight now that that the I have tried the nock fit of the Mercury sting as arrow clicks and doesn’t fall off on so not sure where to from here

Appreciate any feedback

Thanks
 

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In my experience it’s string weight changing the tune not nock tightness.
The equivalent of 2 strands of string weight will change your tune enough to notice.



options;

new string. 2 more strands.
or

Reserve with serving applied less tight and nock fit should improve.
Then add about an inch more of serving material to increase mass weight of string.

weigh the old and new string to compare.
 

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Discussion Starter #3
In my experience it’s string weight changing the tune not nock tightness.
The equivalent of 2 strands of string weight will change your tune enough to notice.



options;

new string. 2 more strands.
or

Reserve with serving applied less tight and nock fit should improve.
Then add about an inch more of serving material to increase mass weight of string.

weigh the old and new string to compare.
Thanks for the response
Just weighed both. 8125g 7.1 grams Mercury 7.0 grams so negligible weight difference.
I didnt mention in first post but speed test had Mercury string 3fps quicker than the 8125 so I put that down to looser nock fit.
 

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My DL is 28.75" and with 36# OTF, .610 ACE with 100gr points tune nicely. Your faster string shows the .670 weak is my best guess. FWIW, I test nock fit not by releasing the arrow by tapping the string as potentially too inconsistent for my clumsy hands. Rather, with the string at brace height, I like an arrow pulled slowly by hand deflecting the string no more than 1.0 cm. That seems to be a more precise way of measuring nock fit.
 

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What was your brace height with the old string, and what is it now? Changing the brace height by an inch gives me about 3fps change with a similar setup to yours. That also has a noticeable effect on the tune.

Mercury and 8125g are different materials as the first one is just dyneema (SK99) and the latter has some some gore fibers and the older SK75 dyneema. If the two had the same weight and nock fit, I'd expect the mercury string to be noticeably faster as SK99 is about 30% stiffer than SS75. I've gotten a 3fps difference by changing string type between dyneema-based strings while keeping the fit and mass pretty much constant. At your draw weight, going down 3lbs should mean about 7fps difference but there's a fair bit of leeway as you're basing it on the turns and not a measured value.

The way to check whether it's tight nock fit preventing the arrow from flying weak, or if the arrow was well tuned with the old string and is just weak with the new one would be to remove the center serving on the old string and serve it with something a bit thinner and see if that makes the arrows fly terribly. Or take a bit of masking tape or something else temporary and wrap it around the nocking point area on the new string and see if that improves the flight.

Going from a fairly loose fit where a flick to the string drops the arrow, to a "so tight it barely clicks" fit on my string by wrapping tape around the nocking point only makes a difference of 1fps for me so I'd very surprised if was causing the speed difference. I could see it having a surprisingly large effect on the tune though if the serving was so tight that it couldn't rotate in the nock.

Cutting a half inch should allow you to bring your draw weight back up by half a spine or only about 2lbs according to the Easton chart. Going from 120gr break-off points to 100gr break-off points (buying the different external length points, not just removing sections) should get you another couple pounds. Going back to the old string which gave excellent arrow flight is an easier option unless you're chasing the extra speed.
 

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Discussion Starter #7
What was your brace height with the old string, and what is it now? Changing the brace height by an inch gives me about 3fps change with a similar setup to yours. That also has a noticeable effect on the tune.

Mercury and 8125g are different materials as the first one is just dyneema (SK99) and the latter has some some gore fibers and the older SK75 dyneema. If the two had the same weight and nock fit, I'd expect the mercury string to be noticeably faster as SK99 is about 30% stiffer than SS75. I've gotten a 3fps difference by changing string type between dyneema-based strings while keeping the fit and mass pretty much constant. At your draw weight, going down 3lbs should mean about 7fps difference but there's a fair bit of leeway as you're basing it on the turns and not a measured value.

The way to check whether it's tight nock fit preventing the arrow from flying weak, or if the arrow was well tuned with the old string and is just weak with the new one would be to remove the center serving on the old string and serve it with something a bit thinner and see if that makes the arrows fly terribly. Or take a bit of masking tape or something else temporary and wrap it around the nocking point area on the new string and see if that improves the flight.

Going from a fairly loose fit where a flick to the string drops the arrow, to a "so tight it barely clicks" fit on my string by wrapping tape around the nocking point only makes a difference of 1fps for me so I'd very surprised if was causing the speed difference. I could see it having a surprisingly large effect on the tune though if the serving was so tight that it couldn't rotate in the nock.

Cutting a half inch should allow you to bring your draw weight back up by half a spine or only about 2lbs according to the Easton chart. Going from 120gr break-off points to 100gr break-off points (buying the different external length points, not just removing sections) should get you another couple pounds. Going back to the old string which gave excellent arrow flight is an easier option unless you're chasing the extra speed.

Thanks for detailed reply.
The 8125 was 202fps with brace at 21.8cm @ 37.5lb. Put new Mercury string on and got brace identical and it was 205fps. Having wound down the limbs to get somewhat straighter arrow flight with new string and its now 196fps so I have lost 9fps with 2.5 turns and left brace at 22cm as I sounded fine there didnt want to take too many twists out due to new limb angle of less poundage increasing brace quite a bit

I’m currently using 100-90-80gn break offs at 100gn so could go to 90 or 80 but am concerned it will impact overall arrow balance and flight if I break off. Reason for replacing old string was a lot of fuzzing so throught I would try local maker and tried Mercury due to also 100% dyneema like 8125 ano it was quick vs ordering from US.

i might try thickening up the center serving And trying again
 

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Discussion Starter #8 (Edited)
My DL is 28.75" and with 36# OTF, .610 ACE with 100gr points tune nicely. Your faster string shows the .670 weak is my best guess. FWIW, I test nock fit not by releasing the arrow by tapping the string as potentially too inconsistent for my clumsy hands. Rather, with the string at brace height, I like an arrow pulled slowly by hand deflecting the string no more than 1.0 cm. That seems to be a more precise way of measuring nock fit.
Ok so using the pull test, arrow detached from 8125 at approx 9mm whilst the Mercury detached at approx 3mm. I have tested with small groove nocks and they definitely do not fit the Mercury string as they are way too tight so I am of the opinion that the serving is correct thickness on Mercury string.

Lets say that I decide to stick with new string with current center serving thickness and go with new arrows, Is one spine stiffer likely to correct this issue or 2 spines. Existing arrows are 670 cut 28.20" nock groove to end of shaft.

I should add that this is all with UUkha SX100 limbs which are a 100% carbon limb so maybe that and the less tight nock fit/extra speed from string have combined to push the arrows way weak?
 

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IF you can cut the shaft around 1/2", I suspect that will put your arrows close. As alluded to by others, it sounds like weak arrows, masked by overly tight nock fit. I would actually measure the base of the point, and then the point end of the shaft where you intend to cut to, in order to ensure that the carbon is not wider than the point base.
 

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Thanks for detailed reply.
The 8125 was 202fps with brace at 21.8cm @ 37.5lb. Put new Mercury string on and got brace identical and it was 205fps. Having wound down the limbs to get somewhat straighter arrow flight with new string and its now 196fps so I have lost 9fps with 2.5 turns and left brace at 22cm as I sounded fine there didnt want to take too many twists out due to new limb angle of less poundage increasing brace quite a bit

I’m currently using 100-90-80gn break offs at 100gn so could go to 90 or 80 but am concerned it will impact overall arrow balance and flight if I break off. Reason for replacing old string was a lot of fuzzing so throught I would try local maker and tried Mercury due to also 100% dyneema like 8125 ano it was quick vs ordering from US.

i might try thickening up the center serving And trying again
8125 is 100% dyneema but 8125g is 8% gore. And before that in some years 8125 alternated between 100% dyneema and a blend but the name didn't change, it's a bit of a minefield.

I definitely wouldn't remove anything from those points - with my 620 ACEs in that poundage range breaking off sections inside stiffens the arrow (due to lower point weight) by about the same amount that it weakens it (due to shorter shank length) so doesn't accomplish anything but reduces FOC. The next lower weight of point is 80 grains full length and that's still in Easton's recommended range if fiddling with the string isn't enough to get the arrows flying well again.

Though you said
didnt want to take too many twists out due to new limb angle of less poundage increasing brace quite a bit
How much is quite a bit? 7 turns gets me 5mm in brace height with 38lb limbs. It varies with riser geometry but if it's much more than that then perhaps there's something else going on.

If you're planning on increasing poundage beyond 37lbs later and if the 45° bareshaft still happens when you change the center serving thickness on both strings, then 2 spines stiffer is likely a safer bet than 1. It varies a bit been people but I've been on 620s (120gr point from 34-38lbs and 100gr from 38-42) with a draw length 1/2" shorter than yours.
 

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Discussion Starter #11
8125 is 100% dyneema but 8125g is 8% gore. And before that in some years 8125 alternated between 100% dyneema and a blend but the name didn't change, it's a bit of a minefield.

I definitely wouldn't remove anything from those points - with my 620 ACEs in that poundage range breaking off sections inside stiffens the arrow (due to lower point weight) by about the same amount that it weakens it (due to shorter shank length) so doesn't accomplish anything but reduces FOC. The next lower weight of point is 80 grains full length and that's still in Easton's recommended range if fiddling with the string isn't enough to get the arrows flying well again.

Though you said

How much is quite a bit? 7 turns gets me 5mm in brace height with 38lb limbs. It varies with riser geometry but if it's much more than that then perhaps there's something else going on.

If you're planning on increasing poundage beyond 37lbs later and if the 45° bareshaft still happens when you change the center serving thickness on both strings, then 2 spines stiffer is likely a safer bet than 1. It varies a bit been people but I've been on 620s (120gr point from 34-38lbs and 100gr from 38-42) with a draw length 1/2" shorter than yours.
I have uukha SX100 so they are already more curved than conventional limbs so I got a 64.5“ string made as Uukha recommends that as a 65” string means that theres not many twists from completely straight to get to recommended brace of 21.8cm which also happens to be quietest for me. The 8125 was also 64.5”. At a guess I would say theres somewhere around 15 twists on the Mercury string for a brace of 22cm after winding down to current 35.8lb.

Before ending up at the above poundage change I tried a little tape on the nock serving and the bare and fletched did straighten up but was still very obvious crooked flight but it got better for each full turn I took off the limbs for total of -4 turns which was 34.6lb. I even went up to 39lb to be sure there was no false results and ended up taking 1.1cm off a bare and a fletched arrow and played with DW and 35.8lb and 22cm brace (199fps) gave straight flight and impact in the target for both arrows with just under 1 full shaft width left of string so I cant think of anything other than the combo of 100% carbon limbs which are relatively fast and the new faster Mercury string with looser center serving exposed a weak spine.

I will test at longer distances when I can and if flight remains good with current settings, I will cut all the arrows down and play with them at the lower DW until I get the itch to empty my pockets on an stiffer arrow so I can go back up to high 30’s.

Thanks to those that replied and offered some suggestions
 

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Discussion Starter #12
IF you can cut the shaft around 1/2", I suspect that will put your arrows close. As alluded to by others, it sounds like weak arrows, masked by overly tight nock fit. I would actually measure the base of the point, and then the point end of the shaft where you intend to cut to, in order to ensure that the carbon is not wider than the point base.
Point fit perfectly into shaft after taking 1.1cm off the 2 test shafts and got me to within 1.7lb of preferred DW but i will need to go with either 620’s or maybe 570’s as I could comfortably go up to 39lb without technique suffering.
 

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for a quick easy reversable test to see if it's a string weight issue, try adding a couple of brass nock locators or add some wraps of tape to the back end of your arrows. If it fixes the tune issue it will give you some clues as to what's causing the difference in spine symptom
 

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for a quick easy reversable test to see if it's a string weight issue, try adding a couple of brass nock locators or add some wraps of tape to the back end of your arrows. If it fixes the tune issue it will give you some clues as to what's causing the difference in spine symptom

Oh yeah, a less stretchy string (if the mercury is really that much stronger in the tensile area) will also contribute to a "weaker" dynamic spine. I don't know if that much but stranger things have been noted..
 

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Discussion Starter #15 (Edited)
for a quick easy reversable test to see if it's a string weight issue, try adding a couple of brass nock locators or add some wraps of tape to the back end of your arrows. If it fixes the tune issue it will give you some clues as to what's causing the difference in spine symptom
I am using beiter outernocks with a small arrow wrap and Eli vanes so rear is definately light. The bare shafts have tape at fletching area to get same weight as fletched but my confusion is that these arrows flew very nicely with 8125 string so could a new dyneema string make such significant tuning changes

I will put some tape on the rear as you suggest to see if stiffening the rear straightens the flight with the new string. I think that my C1 pins might fit the ACE so may try a pin nock combo as well.

Arrows are 280gn and I'm getting 200fps at 35.8lb which I would assume would be decent speed for the lb so perhaps the Uukha limbs are also contributing to this scenario in conjunction with a less stretchy string.

Thanks
 

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Looking for a bit of advice from others who may have had similar experience or might know what’s going on.

Was using a 8125g string bought from reputable US string maker and had my ACE 670 tuned nicely with great arrow flight out to 70m, both bare and fletched. I use large groove nocks and fit was quite tight and arrow needed a bit of a yank to detach from string.

I just put a new string on made from Mercury (26 or 28 strands made locally by archery shop) and it was made to fit large groove nock and the nock fit has an audible click and doesn’t fall off the string when hanging freely but its no where near the tightness of the previous 8125g string. It would be considered loose when compared to the 8125.

8125 string setting was arrow point very close to centre shot and plunger around 7.0 medium beiter spring for straight arrow flight shooting 37.5lb @ 28.5”. Bow is aligned.

The problem I have with new string is that my arrows are flying horribly. At 11 metres, the bare shaft is at 45 degree angle into the target butt nock left but still within a couple of inches of fletched which are hitting close enough to the X (40cm face)and slo mo shows the arrows crooked flight all the way to target. Fletched are also slanted in target but not as extreme as bare shaft.

There is no arrow contact with rest or plunger at all. In order to get the bare and fletched to fly relatively straight out of bow, I have had to take 2.5 turns off limb bolts which is approx 3lb and also had to move centre shot 1 full arrow shaft width left of string but feels like it needs to go even further left which doesn’t seem correct as most using barrelled say close to dead centre is the go.

With the need to reduce draw weight and push center shot 1 full arrow width left of string and a stiffer plunger now improving but still not perfect bare or fletched flight, is this a case that my arrows were always weak but it was masked by tight nock fit or is there something else at play?

I want to get back to 37+ lb and have maybe 1/2” or arrow i can cut but dont know if thats going to be enough or the answer.

I’m guessing that the nock fit for the 8125 was not supposed to be so tight now that that the I have tried the nock fit of the Mercury sting as arrow clicks and doesn’t fall off on so not sure where to from here

Appreciate any feedback

Thanks
If I'm reading this correctly you are shooting a recurve bow at 37.5#. If you have 26 to 28 strands that is NOT recommended. I make my own strings with BCY 8125, shoot 37# to 39# and use 18 strands. I shoot with a number of recurve archers. One of my friends is ranked 3rd on the U.S. para-Olympic team and we use anywhere from between 18 to 20 strands at the most. Nock size depends on center serving diameter. Some center serving is as large as 0.026 Brownell or I am currently using Majesty 0.022 diameter. Incidentally you can go online to find recommend number of strands depending on material. 26 to 28 strands is too much....in my opinion. Moving the center shot that far out does NOT make sense! Personally it sounds like you need to have someone who is familiar with bow set-up and tuning to look at your bow! If you can't do that go to Jake Kaminski's YOUTUBE videos on tuning a recurve bow.

Looking for a bit of advice from others who may have had similar experience or might know what’s going on.

Was using a 8125g string bought from reputable US string maker and had my ACE 670 tuned nicely with great arrow flight out to 70m, both bare and fletched. I use large groove nocks and fit was quite tight and arrow needed a bit of a yank to detach from string.

I just put a new string on made from Mercury (26 or 28 strands made locally by archery shop) and it was made to fit large groove nock and the nock fit has an audible click and doesn’t fall off the string when hanging freely but its no where near the tightness of the previous 8125g string. It would be considered loose when compared to the 8125.

8125 string setting was arrow point very close to centre shot and plunger around 7.0 medium beiter spring for straight arrow flight shooting 37.5lb @ 28.5”. Bow is aligned.

The problem I have with new string is that my arrows are flying horribly. At 11 metres, the bare shaft is at 45 degree angle into the target butt nock left but still within a couple of inches of fletched which are hitting close enough to the X (40cm face)and slo mo shows the arrows crooked flight all the way to target. Fletched are also slanted in target but not as extreme as bare shaft.

There is no arrow contact with rest or plunger at all. In order to get the bare and fletched to fly relatively straight out of bow, I have had to take 2.5 turns off limb bolts which is approx 3lb and also had to move centre shot 1 full arrow shaft width left of string but feels like it needs to go even further left which doesn’t seem correct as most using barrelled say close to dead centre is the go.

With the need to reduce draw weight and push center shot 1 full arrow width left of string and a stiffer plunger now improving but still not perfect bare or fletched flight, is this a case that my arrows were always weak but it was masked by tight nock fit or is there something else at play?

I want to get back to 37+ lb and have maybe 1/2” or arrow i can cut but dont know if thats going to be enough or the answer.

I’m guessing that the nock fit for the 8125 was not supposed to be so tight now that that the I have tried the nock fit of the Mercury sting as arrow clicks and doesn’t fall off on so not sure where to from here

Appreciate any feedback

Thanks
If I'm reading this correctly you are shooting a recurve bow at 37
 

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strands. I shoot with a number of recurve archers. One of my friends is ranked 3rd on the U.S. para-Olympic team and we use anywhere from between 18 to 20 strands at the most. Nock size depends on center serving diameter. Some center serving is as large a
If I'm reading this correctly you are shooting a recurve bow at 37.5#. If you have 26 to 28 strands that is NOT recommended. I make my own strings with BCY 8125, shoot 37# to 39# and use 18 strands. I shoot with a number of recurve archers. One of my friends is ranked 3rd on the U.S. para-Olympic team and we use anywhere from between 18 to 20 strands at the most. Nock size depends on center serving diameter. Some center serving is as large as 0.026 Brownell or I am currently using Majesty 0.022 diameter. Incidentally you can go online to find recommend number of strands depending on material. 26 to 28 strands is too much....in my opinion. Moving the center shot that far out does NOT make sense! Personally it sounds like you need to have someone who is familiar with bow set-up and tuning to look at your bow! If you can't do that go to Jake Kaminski's YOUTUBE videos on tuning a recurve bow.


If I'm reading this correctly you are shooting a recurve bow at 37
Lindy its Mercury strings. Mercury string material have very thin strands. Thats why you need to have twice the strandcount compared to other SK99 material.

"Recommended strands: 32-34 for compounds, 2 or 4 less for recurves "
 

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Discussion Starter #18 (Edited)
If I'm reading this correctly you are shooting a recurve bow at 37.5#. If you have 26 to 28 strands that is NOT recommended. I make my own strings with BCY 8125, shoot 37# to 39# and use 18 strands. I shoot with a number of recurve archers. One of my friends is ranked 3rd on the U.S. para-Olympic team and we use anywhere from between 18 to 20 strands at the most. Nock size depends on center serving diameter. Some center serving is as large as 0.026 Brownell or I am currently using Majesty 0.022 diameter. Incidentally you can go online to find recommend number of strands depending on material. 26 to 28 strands is too much....in my opinion. Moving the center shot that far out does NOT make sense! Personally it sounds like you need to have someone who is familiar with bow set-up and tuning to look at your bow! If you can't do that go to Jake Kaminski's YOUTUBE videos on tuning a recurve bow.


If I'm reading this correctly you are shooting a recurve bow at 37
Hi Lindy,
My original 8125 was 18 strands but the new string that I bought is made from BCY Mercury and is much thinner and needs 26-28 strands for same string diameter as 8125. I trust that the archery shop did the right thing as BCY themselves state approx 28 strands for Recurve strings. Buying locally meant that I could choose either Mercury (100% dyneema) or X-99 which I choose not to as X-99 is dyneema/vectran blend that apparently is not suited to recurves.

I know its a bit of a long read but my first post explains that tune was great with 8125 out to 70m and poundge, center shot and plunger tension were all within standard parameters based on arrow length and Eastern guide so im comfortable that i know how to tune properly.

As soon as I put the Mercury string on and got brace same as previous string and changed absolutely nothing else, my arrows acted very weak which is why I had to cut 11mm off a test arrow (that gets front of point in line with end of shelf), reduce poundage by approx 1.8lb and move center shot out full arrow width to get the arrows to fly straighter. I'm far from an archery expert but assume that if i was to wind the limbs down even further than I already did that center shot would then start to push back inwards towards riser but didn't want to take any more turns out of the limb bolts.

All initial tests with Mercury were at 11 metres and then last night I tested at 18 metres indoors and all the changes I made were validated as bare shaft was still 2-3 inches weak. I shot at least 8 ends of 1 bare and 3 fletched and results were consistently bare in the red with fletched in gold on a 40cm face and slo mo showed nice straight flight from bow to target with fletched but a little tail left kick with the bare approx 7 metres from target.

Once I can shoot at 30m next week I will assume that bare will move further even right of fletched which means that Mercury string and its characteristics have made my 670 ACES significantly weaker.
 

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Any slightest change in nock fit affects arrow speed. I use a bow scale to accurately compare the nock fit on my strings. The technique I use is to tie a string between the scale hook and front end of the arrow. Gently pull the nocked arrow from the bow string with the bow scale until the bowstring lets it off. Do this for both the old and the new bowstring. I bet the new string would register a lighter pull weight.
 
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