# String length?



## dchan (Jun 29, 2004)

how do you know you want a final BH of 8.5?

Many 68" bow seem to BH tune best closer to 8.75"-9" even 9.25"

Which riser/limb combination (by MFG) may also be helpful. Some riser/limb combinations will yield different BH's than most conventional ILF setups.

Do you have a string that seems to BH tune at 8.5" if so, measure that string under tension and build it that way.

64.25 (or 3.75 less than 68") would most likely be too short.

AMO is actually 3" shorter than bow or if you read AMO specification correctly the string is what dictates the length of the bow. ie: a 65" string would be your starting point, and the Boyer should build a bow that will BH best using this 65" string. This would be called a 68" bow (even if it's no where close to 68")

So if you follow AMO standards, your "68" bow" *should* use a 65" string.


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## dchan (Jun 29, 2004)

And that's probably way more confusing than you need..

The point is, you may have to test a few different lengths to find what works best with your setup.

Starting at 64.75" for a string and twisting it up to get to the quietest length would where I personally would start..

I have my configured with markings showing "AMO" bow length, and actual string length as 3.50" different. Depending on the actual bow, I may adjust longer or shorter depending on what the BH works out to be. I then write the string length as "actual length" on the bow or at least on a table that has the bow configuration on it.


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## Alohaguy (Jun 13, 2016)

Following the riser manufacturer ( win & win) recommendation for 8 1/2. Actually they list 8.25 - 9.25 as the range. Using SF medium limbs. My string builder made one at 63.5 and the best I could brace was 9.5


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## Alohaguy (Jun 13, 2016)

I also chatted with an LAS tech expert and he said the AMO was 4 to 4.5 shorter than the rated bow length. Seems like a lot of conflicting info


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## limbwalker (Sep 26, 2003)

3" shorter.


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## GoldArcher403 (Jun 25, 2014)

Alohaguy said:


> he said the AMO was 4 to 4.5 shorter than the rated bow length.


That's way to short. You would never get the full potential out of the limbs when they are restricted by such a short string. He needs to retake the LAS tech class


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## GoldArcher403 (Jun 25, 2014)

3 inches shorter is a good start. I make all my strings 3 inches shorter and I usually am able to BH tune them from there. Right now I'm shooting a Uukha 68" bow with a 65 inch string and running a 218mm (I measure in mm because you can get it more exact) brace height and it's quiet as a mouse. And for those who can't convert metric in their head, 218mm is roughly 8.6 inches.


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## stick monkey (Mar 9, 2015)

For my win win axt with inno powers string length 65 1/2 will get you right at 8 1/2 but I found that it shot better for me at 9 1/4 to 9 1/2


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## Viper1 (Aug 21, 2003)

A - 

For a standard AMO 68" ILF bow:
65", assuming it's not Dacron.

On older (vintage) 68" target bows, using Dacron, you'd be looking at 64". 

If some one at LAS told you 4-4.5" shorter than the AMO measurement, I'd report the guy to Rob or John. 
Unless the bow in question is non-standard (non AMO) that info is just wrong. 

Viper1 out.


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## stick monkey (Mar 9, 2015)

From what I have been told...The rule for 4 inch is a old rule for using dacron string because it would stretch so much. Newer fastflight can be made 3 inches shorter because it stretches far less.


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## zal (May 1, 2007)

Some W&W riser plus non-W&W limbs take 4" shorter. Some Samick + non Samick limbs combos take about 2" shorter. General rule is 3" but you never know.


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## ssxd (Apr 15, 2015)

For people who know their equipment well this probably isn't useful, but as a starting point for finding your string length I thought it might be helpful.

Shibuya's online store in Japan gives you a chart when ordering a pre-made string that tells you which length to choose based on your brand of riser and limbs (in Japanese, but it's mostly numbers and company names).
http://gigaplus.makeshop.jp/SBAEC/6sp17.jpg

There's a table for each AMO length, then each row is for riser maker and each column for limb maker (Hoyt column is pre F7, next column to the right is F7 and later "Gran Prix" limbs, right-most column and bottom-most row are for formula). You order by the code.

To know what you're getting, they have a chart showing actual length in cm corresponding to the codes.
http://shibuya-online.com/shopimages/SBAEC/000000001830_1.jpg

Looking at the charts, it looks like for W&W risers they tend to suggest a slightly shorter string but the main difference is in the limbs, with W&W and MK limbs taking a shorter string while modern Hoyt limbs take a longer one (which I believe is down to the limb tip shapes).


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## dchan (Jun 29, 2004)

AMO is string length first. 

Then the mfg is supposed to build a bow that will BH correctly. Then they would size that bow as 3" more than that string.

Example. 

String (using a steel cable master) is 63" long. 
A bow regardless of actual length, if the mfg wanted a 8" BH, would be built so that using the 63" string, it had a resulting BH of 8" 

Then they would call that particular bow AMO 66" regardless of the actual length or makeup of the bow.

This came from a time before takedown systems when boyers would build most bows as one piece. The writers of the standard were trying to make it so that string mfg's didn't have to custom make every string for every bow. 

Since we now have different mfg's of risers, limbs, etc this standard has been adjusted here and there but the AMO standard remains the same and is 3" shorter than the rated length of the bow.


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## gdrudd13 (Feb 16, 2016)

Since this hasn't been posted yet, I'll share it. Has string dimensions including a couple variations for risers/limbs. Should give you a pretty good starting point.

https://www.ocf.berkeley.edu/~archery/wp-content/uploads/docs/bowstring-dimensions.pdf

As an aside, check out the resources tab on the UC Berkeley archery page. There's a lot of other good information there.


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## DK Lieu (Apr 6, 2011)

gdrudd13 said:


> Since this hasn't been posted yet, I'll share it. Has string dimensions including a couple variations for risers/limbs. Should give you a pretty good starting point.
> 
> https://www.ocf.berkeley.edu/~archery/wp-content/uploads/docs/bowstring-dimensions.pdf
> 
> As an aside, check out the resources tab on the UC Berkeley archery page. There's a lot of other good information there.


The overall string lengths shown in this document are for non-overlapping (what I designate as "R3", and what I now build exclusively) end/loop servings. Since non-overlapping servings sit flatter on the limbs, a slight shorter string is recommended. If using an overlapping serving, which is most common in the US, 1/2" should be added to overall string length shown in the document, thus bringing the overall length to approximately 3" shorter that the AMO length of the bow.


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## Odieus (Feb 29, 2016)

Find with the brace height extremes out there that you have to really twist them for something like Win Win to get to 9" or have one build shorter. Then on the other extreme, you need a longer build for the super recurves like Border. Out of the box is becoming less useful.


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## Corene1 (Apr 27, 2014)

Not a string expert but for my 25 inch SF forged plus with medium Win&Win Winex limbs. The strings I build are 64.25 untwisted and 63.6 twisted which gives me a brace of 8.75 . This is with BCY 8125G and 18 strands.


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## Byron67 (Jan 13, 2013)

Awesome Chart - Thanks for posting!


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