how to figure out string length?

[MTArrowLauncher]

I need a string for my learner bow, how do you know what length you need?
thanks

Fin

[sbschindler]

recurve or longbow ??

[MTArrowLauncher]

Its a 57" recurve

[stevem]

I believe for a recurve you subtract 4" from it's AMO length and subtract 3" for a longbow.

[sbschindler]

stevem is correct.

[JRY309]

Thats not always true,I make them 3" shorter for both recurves and longbows if I don't have the old string.My Martin Hunter 62" recurve takes a 59" string and I set my brace height at 7&3/8".Alot has to do with the bowyers design and recommended brace height range.I also like to measure the actual bow length from nock to nock.

[Rob DiStefano]

use a tillering string.  

this string is about 72" to 80" long, has a loop at one end only.  slide the loop over the top limb, drop it down about 3" from the top limb string nock, tie a bowyer's knot (timber hitch) to the bottom limb and brace up.  

adjust the bowyer's knot 'till you achieve a good brace height, remove the string and use it as a guide for either a flemish or endless string.  

tillering strings make good, extremely adjustable bowstrings that are every bit as good as a double loop bowstring.  i have a strong guess that this is how medieval bowstrings were built - single loop or no loops at all, since those old bows and strings changed the brace height on at least a daily basis.

[jdemoya]

On the same line: how much do you need to lengthen or shorten a string to change your BH by 1/2"? Is there a formula? Thanks.

God bless,

José

[Rob DiStefano]

Originally posted by jdemoya:
On the same line: how much do you need to lengthen or shorten a string to change your BH by 1/2"? Is there a formula? Thanks.

God bless,

José

no formula, far too subjective in terms of the TRUE ntn bow length, the string's length working range (via twisting) and the fiber type (precise same static length polyester and hmpe strings will have different brace heights due to fiber stretch/creep).

this is where a tillering string is needed.

[Swamp Yankee]

Rob is right on with the tillering string.  Very few (if any anymore) bowyers actually comply with the true AMO "standard"; which in theory says you could order a 57" AMO string (which would actually be 54" long when under 100 lbs of stress) for a 57" AMO bow.  The 57" AMO string will work, but you may or may not be anywhere near the recommended brace height for that particular bow.

[PowDuck]

The best thing is to ask the string maker. They have knowledge about different bows' preferences.

Case in point:
I traded for a Shrew and the previous owner had bought a string for it but never actually mounted it. When I tried it out the brace height was a full inch higher than recommended and there was no more untwisting left to do. I called the string manufacturer and before I could even finish my explanation he stopped me. He said, "You said it was a Shrew. The string is an inch too long. Shrews take 2" less than AMO. Not 3."

But the general rule is:
Longbows 3" less than AMO