# Formula for twist rate and string length



## Cdpkook132

Is there some kind of formula for how much longer you need to set the jig over your finished string length to account for the twists? Is there an optimal twist rate for string and cables? 


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## retribution

Roughly 1/4 inch for every 50" of string length..thats what i go for 452x and trophy..twist ratio i just divide total length of string by 1.5 and thats how many twists..
If you contact deezlin on here and purchase his dvd it will walk you through the whole process from start to finish of building a good quality string..dvd is fairly cheap,less than $40 i belive and will solve you alot of headaches.


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## cuttingedge

This is what "I" do. I'm sure you will get many opinions, and many will work.

For strings in the 60ish length I allow about 1/8" extra length on the layout. Once the end serving is done, I put in 35-40 twists in and stretch the string. After it sits under tension for a few minutes I measure it and add or remove twist to get to the proper length. Serve under tension. After serving is completed, I usually relax the string and re-stretch it. 

For cables in the 30-35ish length I allow maybe 3/32" overage. After serving the end loops I add about 25-30 twists, stretch it, measure it and add or remove twist to get the proper length. Serve under tension.


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## edthearcher

do a search there are many great formula here


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## Brown Hornet

This is the formula I have been using....

Length X .75 X .012

So if your building say a 53" string.... 53 X .75 X .012 = .477 add that to your string length and you get 53.477...set your post there and build. Twist to length, stretch and serve.


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## Cdpkook132

Brown Hornet said:


> This is the formula I have been using....
> 
> Length X .75 X .012
> 
> So if your building say a 53" string.... 53 X .75 X .012 = .477 add that to your string length and you get 53.477...set your post there and build. Twist to length, stretch and serve.


Thanks I will keep this one in mind.

I also found this 



Hoytalpha35 said:


> My formulas are desired length x 1.007 = jig length. For twists I multiply length x 0.66. Hopefully that gives you a start. You'll probably need to do tester string and make some minor adjustments do to variances in how you lay-up and stretch.





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## flag

im constantly tweaking my formula but if you will take your string length and muliply it by 1.01 that will give you your jig setting and then multiply your string length by 0.75 and that will give you the number of twist. that will get you close but it comes down to how much tension you stretch at and how long you will have to find what works for you and when you find it just try to be consistant with your process and you will get good results


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## Cdpkook132

flag said:


> im constantly tweaking my formula but if you will take your string length and muliply it by 1.01 that will give you your jig setting and then multiply your string length by 0.75 and that will give you the number of twist. that will get you close but it comes down to how much tension you stretch at and how long you will have to find what works for you and when you find it just try to be consistant with your process and you will get good results


Thanks for the advice


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## Hoosier bowman

This is good stuff... I have taken the advice here and averaged it:

~Brown Hornet said:
Desired Length X .75 X .012 = amount to add that to your string length
This is the same as multiplying the desired length by 1.009 to get length you need to start building at.

~Hoytalpha35 said:
desired length x 1.007 = jig length


1.007 + 1.009 = 2.016 / 2 = 1.008


So, I multiply the desired final length by 1.008 and get the length I need to set my jig for. For # of twists I just divide length by 1.5 so I have 1 twist for every 1.5" of string length. 

This is what I have been using and it works great.


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## drewbie8

Brown Hornet said:


> This is the formula I have been using....
> 
> Length X .75 X .012
> 
> So if your building say a 53" string.... 53 X .75 X .012 = .477 add that to your string length and you get 53.477...set your post there and build. Twist to length, stretch and serve.


this is the same one i use and it works well for me


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## macnimation

I am interested in the string building now and this thread is excellent.
I have one question though.

When you calculate the correct length of the jig and build the string, then you calculate the correct number of twists, when you twist the string, will it bring it to the correct length required or will it be shorter than the correct length required?

Because if the twists bring the string to the correct length, then surely stretching the string will make it longer that it should be?

I have watched many videos of string making and they all seem to measure the jig the correct length of the string required and then build.
They then add the required twists, which will shorten the string, and then put it back on the jig, then then implies that the string is stretched to the correct length.

Is that correct?


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## K.G.K.

Lay your string out, serve your ends, twist to length (close) and stretch to at least 300# for an hour or more. Relax the string and then measure the string while under 100# tension. Add or remove twists to achieve desired length at 100# tension. Stretch to at least 300 lbs tension and serve. Relax and install. You could re measure at 100# tension to make any slight adjustment. Install and shoot

If you send me your email I can send you an excell program string jig calculator where you put in the desired string length and it will tell you the jig post setting and number of twist needed.


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## george2524

Would this formula apply to cable lengths also?


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## RatherBArchery

I use the formula that Hormet uses, worked well on the 4 strings I have built.


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## macnimation

Excellent information. Thanks for the advise.
Are there any jigs that provide the string stretching and also have a weight scale so that you know when you have both 100 and 300 lb applied?


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## RatherBArchery

Just noticed my post above, SORRY HORNET  Not sure where the Hormet came from???


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## bluerocker

Ok I have a dumb qusetion for you guys, the formulas are all about the same. But if I'm building a 54" string and use the formula I get .477 ok what is that on a tape measure? How do you convert it to something on a tape measure? I uselly set my jig 5/16 longer for a 54" string, and put 1 twist for every 1 3/4"


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## gofor

1/2" is .500. 31/64" is .484. 15/32" is .467. 7/16" is .434. My guess is that if you are doing well with 5/16ths, then 7/16ths wouuld be a good place to start. However, I am not a string maker.

To get the decimal equivalent of a fraction, divide the top number by the bottom number using a calculator. For example: 31/64 = 31` divided by 64, which gives you 0.484375, which rounds up to .484, a little more than the .477 you came up with. I seriously doubt anyone will notice 100th (.010)especially when it can be adjusted with a partial twist.

Just as a reference, when measuring with a ruler, the eyeball margin of error is about + or - .007, or a total of about .014". If you take two different brand tape measures and lay them side by side, you could easily see more than a 32nd inch (.031") difference at the 54" mark. I have seen some disagree by over 1/16th, so best to use the same measuring stick all the time to get consistency.

JMTCW

Go


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## JF from VA

Here is a quick chart for decimal to fraction conversion if you don't want to calculate them:

http://www.hamuniverse.com/antfrac.html


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## BowBaker1640

I multiplied my end length x 1.007 to get my post setting and ended up with my buss cable 3/16" long


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## Rantz

BowBaker1640 said:


> I multiplied my end length x 1.007 to get my post setting and ended up with my buss cable 3/16" long


This could have been caused by a different length yoke leg. Or do you mean that even when measuring it linearly with the yoke legs on the same post, you're too long?


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## Unk Bond

Hello All
Archers always seem to follow the trend of others. Why not something different in lenth . Say a inch longer than finish lenth. And twist the bow string to lenth. And then keep cables normal. [ Later


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## Hoytalpha35

BowBaker1640 said:


> I multiplied my end length x 1.007 to get my post setting and ended up with my buss cable 3/16" long


Did you let it relax overnight before checking the length? With the pre-stretch it takes a little time to recover. If you get this consistently then it is just a matter of adjusting the formula for how you build.


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## BowBaker1640

Rantz said:


> This could have been caused by a different length yoke leg. Or do you mean that even when measuring it linearly with the yoke legs on the same post, you're too long?


measuring with both yokes on the same post


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## Rantz

Unk Bond said:


> Hello All
> Archers always seem to follow the trend of others. Why not something different in lenth . Say a inch longer than finish lenth. And twist the bow string to lenth. And then keep cables normal. [ Later


I'm assuming it has to do with staying within a desired twist ratio from string to string regardless of length. It would affect the ratio differently on long single cam strings than it would on two cam or hybrid string lengths.


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## BowBaker1640

Hoytalpha35 said:


> Did you let it relax overnight before checking the length? With the pre-stretch it takes a little time to recover. If you get this consistently then it is just a matter of adjusting the formula for how you build.


yes I did so i'm going use l x.75x.012= post setting. that will give me a starting point for the jig that should work.


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## Unk Bond

Rantz said:


> I'm assuming it has to do with staying within a desired twist ratio from string to string regardless of length. It would affect the ratio differently on long single cam strings than it would on two cam or hybrid string lengths.


============

Hello All
Quiet agree.
My bad, I was thinking of my 2 two cam bows . With this type of string length. Haven't shot my old single cam bow for several years.Have no idea how extending length might work out. But thanks for pointing it out. Might try one.
Might add here both strings being black. Even though I prefer 2 color bow string and one being orange. The trade off to solid black was worth it. [ Later


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## BowBaker1640

BowBaker1640 said:


> yes I did so i'm going use l x.75x.012= post setting. that will give me a starting point for the jig that should work.


this formula I posted here before won't work either because it comes up with a starting length even longer than there other formula


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## Ray knight

I made a nice excel calculator for jig setup and twist rate. If anyone needs it, shoot me an email and i will send it to you.


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## 48archer

Here is a formula i have read about in a post that i would like to here anyones comments about, the builder claims that for example if he is building a 100in finished length string he sets the set up length at 99 7/8. What ever the finish length is he goes an 1/8in under. Now this is with 452x material, has anyone ever tried that or is it even possible to build that way?


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## Ray knight

48archer said:


> Here is a formula i have read about in a post that i would like to here anyones comments about, the builder claims that for example if he is building a 100in finished length string he sets the set up length at 99 7/8. What ever the finish length is he goes an 1/8in under. Now this is with 452x material, has anyone ever tried that or is it even possible to build that way?


That makes no sense at all! Is he twisting the strings? Especially at 100"! I would set the jig at 100 7/8"


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## Ray knight

Also if anyone wants my string calculator - email me at [email protected] and i will send it to you for your free use. Its a time saver.


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## 48archer

Ray knight said:


> That makes no sense at all! Is he twisting the strings? Especially at 100"! I would set the jig at 100 7/8"


Yep, i cant figure that one out either.


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## Flame-Tamer

length x 1.01 for post setting

Length x .67 for twist rate give or take. this allows for served end loops taking up a 1/4 inch..


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## BowBaker1640

BowBaker1640 said:


> I multiplied my end length x 1.007 to get my post setting and ended up with my buss cable 3/16" long


 I made another cable and this time I made it 3/16" shorter on the layout and it ended up perfect. so instead of 39 9/16" I went with 39 7/16" to get a buss cable 39 1/4"


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## Hoytalpha35

BowBaker1640 said:


> I made another cable and this time I made it 3/16" shorter on the layout and it ended up perfect. so instead of 39 9/16" I went with 39 7/16" to get a buss cable 39 1/4"


That would put your formula at 1.005. What did you use for your twist ratio?


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## BowBaker1640

Hoytalpha35 said:


> That would put your formula at 1.005. What did you use for your twist ratio?


that's a tricky one because when I used the formula from N W Spinner which is. Length x 1.0075 = post settings with a .67 twist ratio (which comes up with 26.2975) seems like it twists way to tight


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## wdunc

Great tool on the NWspinner website... http://nwspinner.com/index.php/adjusting-for-twists-and-stretch ... download the file and play around with it for a bit... there's a lot of preset string lengths already there. 

Nice thing about this is that you can modify the formula for what you desire... makes building strings easy


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## PB26

Ray knight said:


> Also if anyone wants my string calculator - email me at [email protected] and i will send it to you for your free use. Its a time saver.


Yep. Just finished my first string set and this calculator worked like a charm. Thanks!


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## johncraddock445

Tagged 

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## ron w

so much of that variation depends on your lay-up method and tension and post diameters. in string building, the length issue is a place where you have to work out what works for your lay-up methods by making small adjustments in the formulas. take notes and make changes accordingly, but don't change your methods to meets the formulas. staying with your same methods will eventually produce a basic consistency there, at the foundation of your string building, as you get more experience and then your notes and changes will remain valid and lengths will start to come out right on the money. if you keep changing your methods, there will be no consistent basis upon which you can compare the small changes you make to the formulas and you will be forever chasing that finished string length inconsistency.


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## Peteyur

Thank you all for posting some very helpful formulas!!!!!


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## rodboggs

This is a very informative thread, Good place to start.


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## dsal

Brown Hornet said:


> This is the formula I have been using....
> 
> Length X .75 X .012
> 
> So if your building say a 53" string.... 53 X .75 X .012 = .477 add that to your string length and you get 53.477...set your post there and build. Twist to length, stretch and serve.





drewbie8 said:


> this is the same one i use and it works well for me


Same here, and also use length x 1.007


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## redman

great info. String


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## tote

This has worked for me every time.
Not sure if it has anything to do with the jig I have. It's worked on 2 separate jigs so far so probably not.
All I'm saying is this is what works for me.
String or cable length x 1.008 = jig setting.
String or cable length x .66= twists. Round up.
I like things that are simple and work. For me, this fits the bill.


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## mfr22

BowBaker1640 said:


> that's a tricky one because when I used the formula from N W Spinner which is. Length x 1.0075 = post settings with a .67 twist ratio (which comes up with 26.2975) seems like it twists way to tight


This is the formula I have used since I started building and it works every time. Never have I felt it was too tight.


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## NoviceAddicted

I use the string formula, string length x .75 x .012 + string length and stay within manufacturers recommendations of .5 to .75 string twists per inch using bcy-x do tag ends and spectra end servings. I am leaning towards using .75 twists on string, cables to keep uniform and reduce or eliminate peep rotation. I know I can use glue on Dloop to match slight rotations of peep sights and have at times but would rather not.


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## jhhitman

So. I use the multiply by 1.008. I don’t worry about any other measurements for strings twist. I twist until the length is correct. I would rather have a proper length string. I also stretch them twist then stretch again. If done correctly the second time I stretch there is no movement in the strings. Just my way of doing it.


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## DKLOTZ

Bakers Archery Products has formula sheets that are very helpful and easy to understand plus he makes great products look him up .


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## Euddy

hello


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## Euddy

is that


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## Euddy

or sorry wrong foro


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## BowhunterJT

ron w said:


> so much of that variation depends on your lay-up method and tension and post diameters. in string building, the length issue is a place where you have to work out what works for your lay-up methods by making small adjustments in the formulas. take notes and make changes accordingly, but don't change your methods to meets the formulas. staying with your same methods will eventually produce a basic consistency there, at the foundation of your string building, as you get more experience and then your notes and changes will remain valid and lengths will start to come out right on the money. if you keep changing your methods, there will be no consistent basis upon which you can compare the small changes you make to the formulas and you will be forever chasing that finished string length inconsistency.


you've done this once or twice i believe... most articulate explanation on what is really important in string building. couldn't agree more.


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## 0311Grunt

Yes there is a formula


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## smokn_speed_bow

What constitutes a "twist" is it 360° or 180°? Using bap formulas and when I do 360° I come up short but if I do 180° it's on the money with .012 as the string length variable...thanks in advance! Love their equipment by the way!


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## CKCECB

I always took it as one twist is one revolution, and it comes close enough for me after stretching. I use Butch's spreadsheet and a 2-post jig.


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## smokn_speed_bow

Also I have found if I layup my string with too much tension the top strands are tight and the bottom are looser. So I bought the bap post tension thingy and lay it up with lighter tension and have more consistent tension and spend less time on the stretcher. The post tension thingy is worth the money!


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## BowhunterJT

smokn_speed_bow said:


> Also I have found if I layup my string with too much tension the top strands are tight and the bottom are looser. So I bought the bap post tension thingy and lay it up with lighter tension and have more consistent tension and spend less time on the stretcher. The post tension thingy is worth the money!


your are correct with the different tensions. you can set up tight with all strands the same by having a jig that is solid and immovable when pulling on each strand.


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## Cumbo

The BAP formula sheet you get for free off their website is absolutely amazing, BUT their formula depends on the amount of time you stretch. If you let a string stretch over night or let’s just say 5 hours, you will probably have to add an extra twist or two. The formula is perfect but you will have to tweak it very minutely to perfect it to the way you build a string.


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## packy

macnimation said:


> I am interested in the string building now and this thread is excellent.
> I have one question though.
> 
> When you calculate the correct length of the jig and build the string, then you calculate the correct number of twists, when you twist the string, will it bring it to the correct length required or will it be shorter than the correct length required?
> 
> Because if the twists bring the string to the correct length, then surely stretching the string will make it longer that it should be?
> 
> I have watched many videos of string making and they all seem to measure the jig the correct length of the string required and then build.
> They then add the required twists, which will shorten the string, and then put it back on the jig, then then implies that the string is stretched to the correct length.
> 
> Is that correct?


It depends on the material. I multiply length by ,67 to get number of twists I’m going to add. Then I multiply by .012 to get the “extra” length I need to add on the jig. This “extra” length is way is how much the string will shrink due to adding the twists. I usually build with 452x or BCY-X and they do not stretch very much. If I tension them and let them sit and then relax when I measure it hasn’t changed much—maybe one or two twists (if any!) to bring back to correct length.
So long story short: yes, set the jig with the “extra” length included when you layout the string.


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## packy

packy said:


> It depends on the material. I multiply length by ,67 to get number of twists I’m going to add. Then I multiply by .012 to get the “extra” length I need to add on the jig. This “extra” length is way is how much the string will shrink due to adding the twists. I usually build with 452x or BCY-X and they do not stretch very much. If I tension them and let them sit and then relax when I measure it hasn’t changed much—maybe one or two twists (if any!) to bring back to correct length.
> So long story short: yes, set the jig with the “extra” length included when you layout the string.


To clarify the above—I stretch them, let them relax, _then put them back at ~100lbs tension_ and measure them


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## pa.hunter

TTT THIS POST HAS LOTS GOOD INFO IN IT !


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