String length

Robbie Nude

Member
I've just ordered and received a string as a back-up for my 66" bow (SF Forged+)
I set about to get the new string twisted to the correct length to achieve the bracing height and to establish the position of the nocking point.
My existing string has several twists in it and when I lined up the two strings the new one is fully three quarters of an inch shorter - without any twists.
I don't want to attempt to put the new string on the bow as it will certainly increase the bracing height to well above the recommendation.
My existing string is fully 63 + half inches while the new one is 62 + 3 quarters inches.
I'm just back into archery after a 5 year absence and while it may have been the case, I previously never noticed that the actual length is marked on the tube. (It's a 66" string but it is also marked on the tube as 62 and three quarters.)
What ACTUAL length should a 66" string be?
- and is there an 'industry variation' in actual lengths for each given 'official' string length.
("Official" length meaning a string for a 66" bow, or for a 68" bow, etc.)
Hope I've made it clear what I'm asking?
 

Rik

Supporter
Supporter
The answer is "it depends" - different limbs in different handles may need slightly different lengths of string to get an acceptable bh.

But... 62.75 sounds dead in the middle of what I would be trying on a 66" bow. 63.5 sounds on the long side. Can you tell us what bh you're aiming for?
I'd be looking for something between about 20.5cm and 23cm, measured from the grip to the string.
I'd be expecting to put 20 twists or so into a string of that length and be in the lower end of that bh range, once it's stretched in.
Is possible the old string started out that sort of length.
 

AndyS

Supporter
Supporter
Like Rik said "it depends"...

I've been making my own strings for a little over 3 years now, and in that time I've used exactly the same "long" SF limbs on 3 different 25" risers (different brands), but I needed to make slightly different length strings for each riser to get to the same sort of bracing height with a similar number of twists (all 8190, with the same strand count).
Likewise my wife shoots short MK limbs on a 25" Hoyt Prodigy, and her strings need to be 20mm shorter than I make for a friend who has short Hoyt limbs on a 25" Hoyt Epik - same material, same number of strands, same nominal 66" bow length, same string maker, but a 20mm difference!

The string material will also affect the initial unloaded string length that's needed to give the correct length on the bow. If I'm using 8125 I'll make the string around 3mm shorter than when I use 8190 because 8125 stretches slightly more once it's under the tension of being on a bow, likewise I'd go slightly shorter again if using FF+ which stretches more than 8125. Strand count will also affect stretch - the more strands in the string, the less stretch under the same load, but higher poundage limbs will cause more stretch than lower.

So there are a lot of variables before you get into what length a standard shop-bought string length should be - whatever length you make a "standard" string for a 66" bow, it will probably be a good length for some limb/riser combinations, and not for others.

As well as length, your other potential variable with a pre-made string is the nock-fit unless it's the same brand & spec, or if it specifically targets a particular nock fit. For example, using the same serving material and 8125G string material, a strand count that gives a nice fit on Beiter No1 nocks is slightly too tight for Easton small groove pin nocks, where I get a better fit from 1 less strand in the string - so also compare the nock fit.

Whilst all that fails miserably to answer what length a string for a 66" bow should be, it hopefully shows why it's a difficult question to answer.

For what it's worth, I set the jig to 1584mm(62.4") for the MK/Prodigy 66" and 1604mm(63.1") for the Hoyt/Epik 66" when using 8125, which give the required brace heights on the two bows with around 30 / 35 twists, and sitting exactly either side of Rik's 62.75 starting point. However by the time they've been left under 120kg for a few hours (no twists), they are a few mm longer than the jig was initially set for. I've never actually checked to see if they fully revert to their original length after stretching is removed, but depending on what string you get, it may or may not have been pre-stretched.

If you've got problems with pre-made string lengths, is there anyone in your club that makes strings (and is prepared to do so for other members)? you might be on a restricted selection of colours, but you can get a custom length and hopefully a good nock fit.
 

Robbie Nude

Member
Thanks for all your comments.
The recommended B.H. is between 21.5cm -- 23.5cm. With my existing string the B.H. is presently just on the upper figure. The bow hasn't shot an arrow in 5 years so I'm wondering if the string will stretch a little with use thus lowering the height.
If not, it looks like I might have to take a few twists out of it as I'd prefer to have the height in the mid-range rather than at the top end, so that would make the string a little longer than its current 63.5"
That means that the difference between that and the new string would be even greater . . . oh dear!
The new string is an 8125 so would it stretch a little?
Even so, possibly not as much as I would need.
I'll keep a hold of the web link (Evans bow strings).
 

Timid Toad

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I would expect an off the peg string to have had little if any stretching. My suggestion would be to pop it on the bow untwisted, and let it sit a few hours. Then measure. If it is stretching, get a couple of twists in and shoot it; the stretch will continue for perhaps a couple of dozen shots. Then you should be able to get some more twists in and a happy bh.
 

Rik

Supporter
Supporter
Er. 21.5 to 23.5cm is the bh range for a 68" bow (medium limbs on a 25" handle). Didn't you say 66"?
 

Robbie Nude

Member
Er. 21.5 to 23.5cm is the bh range for a 68" bow (medium limbs on a 25" handle). Didn't you say 66"?
Rik ? your comment above prompted me to re-examine, probably more thoroughly than I previously did, exactly what I have been shooting with.
Your comment has changed the whole complexion of this thread ? but more than that, it has changed the whole complexion of my relationship to my equipment.
My embarrassment is equalled only by my annoyance that I find myself in this situation.
I shoot 26.75? arrows so I should be using a 66? bow. My 3 previous bows were all 66?, and when I ordered my current equipment in 2012 that is what I specified.
I specifically requested limbs that would give me 38lbs @ 28? in a 66? bow.
I assumed and believed that the bow I have been using was 66?.
Yes, I know that the information has been available had I just been a little more careful and fastidious in researching.

In case anyone is wondering how I didn?t spot the difference between this and my previous bow, that?s because my previous bow went on ebay around 5 years prior to 2012 so there was nothing physical with which to make any comparison.

This has voided the original question I posted above in connection with string length and has introduced a whole set of new issues ? not the least of which is my embarrassment at feeling like a beginner who has purchased unsuitable equipment.

I have been intending replacing my existing limbs with carbons. I would have been ordering ?medium? limbs as replacements. I now see that they will have to be ?short? and this throws up at least 1 new question:

How much of a difference am I going to find by changing from medium to short limbs while still using the same riser?

I?ll wait to see what responses come on here before posing any more questions ? I?m sure there could be more?

I have to finish this by saying that by far this has got to be the most embarrassing post I have ever made on any forum on this planet ? but I?d rather be embarrassed than continue blundering on in my ignorance.
 

Rik

Supporter
Supporter
It makes the string length problem clear, at least...
On the bow length - not so fast...
You're on the borderline between 66 and 68. I know because that's where I am too. I shot 66" bows for years. I changed over to a 68 a couple of years back, and I'm feeling the benefit in terms of reduced wear on my fingers...
I would recommend at least considering sticking with medium limbs.
 

Timid Toad

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With 26.75" arrows, therefore probably a 27" or less draw, (measured to the button plus 1.75"), I'd go with a good quality set of shorts. Unless you have hands like bear paws.
 

Rik

Supporter
Supporter
With 26.75" arrows, therefore probably a 27" or less draw, (measured to the button plus 1.75"), I'd go with a good quality set of shorts. Unless you have hands like bear paws.
That's the thing... If it's a proper 26.75" shaft then the draw length is 27.5" and that's borderline...
 

Timid Toad

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My guess would be that RN ought to get measured up correctly for his current form before making any (more) assumptions and splashing the cash ;)
 

Robbie Nude

Member
It makes the string length problem clear, at least...
On the bow length - not so fast...
You're on the borderline between 66 and 68. I know because that's where I am too. I shot 66" bows for years. I changed over to a 68 a couple of years back, and I'm feeling the benefit in terms of reduced wear on my fingers...
I would recommend at least considering sticking with medium limbs.
With 26.75" arrows, therefore probably a 27" or less draw, (measured to the button plus 1.75"), I'd go with a good quality set of shorts. Unless you have hands like bear paws.
Now you guys have got me really confused! (and no, I don't have hands like bear paws!)

My reason(s) for leaning towards a 66" bow are based on "what I think I know" and information that is widely available, such as a chart showing this:-
Draw length:​
Bow length:
23" and under​
62"​
23 to 25"​
64"​
25 to 27"​
66"​
27 to 30"​
68"​
30 to 32"​
70"​
31 to 34"​
70 -​
*​
72"​

I can see how a 27" arrow is borderline, but when I look at the 68" bow, it can comfortably accommodate arrows up to 30".
My feeling is that at a draw length of 27" the potential energy of the limbs would appear to be substantially under used, whereas in a 66" bow a 27" draw would be close to optimum.

I do know that my performance with my current bow has not been up to the same standard as with my previous bows -- whether that is down to the different bow length or (possibly more plausibly) my advancing age I'm not sure!

Right now I remain 'open'.
 

Mark31121

Member
Ironman
Do you use a clicker? If so measure how far away it's set from the button and measure the point length on your arrows.

I'm assuming that the 26.75" is from the nock grove to the end of the shaft?

With this information we can work out what your AMO draw length is - It's my preferred method as whenever I try to measure someone for an arrow it tends to do weird stuff with their form.
 

Rik

Supporter
Supporter
Okay...
Regarding the "potential energy" - that's driven by the force applied to the shaft between the draw length and the bh. With a (normally) slightly higher bh on a longer limb, you've got a slight reduction in that draw stroke. So longer limbs are said to be slightly slower.
The recommended draw for a length of limb is more of a guideline unless you're looking at radical designs (like Border Hex). You can get away with shorter limbs, with a shorter draw length, because it's not going to stress your fingers so much.

But the reduction in the power stroke doesn't change things much. It's not something I would consider, unless there was some desperate reason to squeeze every ounce of performance out of a setup. I'd rather go with something that makes the shot feel a little easier. Mind you, it took me around 30 years to bite the bullet and go to medium limbs, which in itself is an indication that the difference between the two choices around this draw length, is small.
I'm enjoying not having my third finger callous up as much as it used to...
 

Robbie Nude

Member
Do you use a clicker? If so measure how far away it's set from the button and measure the point length on your arrows.

I'm assuming that the 26.75" is from the nock grove to the end of the shaft?

With this information we can work out what your AMO draw length is - It's my preferred method as whenever I try to measure someone for an arrow it tends to do weird stuff with their form.

Mark ~ I do use a clicker, and the 26.75" IS from the nock groove to the end of the shaft -- without the point.

Rik ~ thanks for all your input and helpful advice.
As I said, I'm hoping to change to carbons soon and normally I would just go online and order them there . . . and that's what I was going to do. But having considered all that has been written in this thread I'm going to make an 'away trip' to a dealer with a shooting range so that I can FEEL what I'm buying rather than wait for the postman to bring me a 'blind order'.
Like you, I've been through the calloused fingers and the shaking bowsight before 72 arrows have been shot. (The bowsight itself doesn't shake -- it's the person whose hand is on the grip!)
I want to be able to shoot without the pain, AND to be able to shoot to a standard that I know I should be able to shoot.
Without having too much weight on the fingers I'd still like to be able to shoot 90m/100yds without having to aim at the top bedroom window of the house behind the target!
 
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