What string length?

[Pine]

I have seen this come up several times recently.
What length string do I need for this bow?

Recurve; AMO inches - 4 inches

Longbow; AMO inches  - 3 inches

[frank bullitt]

Pine, not always is the case!
Alot of factors in design of a bow, custom
Even manufactured bows in the beginning of AMO, didn't adhere to standards.
3" at under 100lbs of tension.

[Dave Worden]

String length is AMO minus 3" PERIOD.  Whether longbow or recurve is irrelevant.  You are confusing a "rule of thumb" for determining string length by measuring the belly of the bow with AMO.  Years ago, I sent a copy of the AMO book here to Tradgang and they included it in one of the windows? on the site.  I suspect it's still there,somewhere.

[Dave Worden]

I just looked for it.  It's in the How-To section.

[Kirkll]

i've never seen a bow that takes a 4" shorter string that is AMO length... 3" is closer, but not always the best. All of the bows i build are 2.5"-2.75" shorter and have high preload. But different bow designs will vary in string length for best results... On custom bows ALWAYS talk to the bowyer for his recommendation on string length and best performance. There is no one size fits all bows of the same AMO bow length which is measured tip notch to tip notch on the belly side running around the curve and straight to the top limb limb and around the curve.

The most common belief that string tension gets higher as you twist up the string making it shorter is dead wrong. Believe it or not, the string tension at brace or preload gets higher as you lower your brace height and increase the string length... If you are a non believer, use an in line scale and measure it yourself. it will surprise you.   Kirk

[Dave Worden]

If you read the AMO booklet you'll find that AMO string length is DEFINED as 3" longer than the the string that braces the bow properly ACCORDING TO BOWYER.  That is, the bowyer determines the proper length string, then adds 3" to it and that's the AMO number written on the bow.  Therefore, the proper "AMO" string length is 3" shorter than the number on the bow.  ALWAYS.  Note also that there is no longer an AMO.  They've changed their name and I don't think there is a "new" AMO length defined.  I find the whole AMO number stupid.  Why didn't/don't the bowyers just write on the bow the length of the proper string (loop to loop)?  Adding the 3" does nothing but confuse.  Kirk is absolutely right.  If you want to know the proper string length for a bow, ASK the bowyer.  I see questions here all the time like..."I just bought a used xxxxxxx bow without a string.  What string length/brace height should it be?"  If it's an old bow with an AMO number, the string length is that number minus 3".  If it doesn't have an AMO number, ask the bowyer.  If it has a length number on it but it doesn't say AMO, that just adds to the confusion.  Is that the string length or the bow length?  When you ask the question on line you can get a lot of OPINIONS.  The only one that matters is that of the bowyer.  And keep in mind, that number is still just a starting point, not an absolute.  Different people shoot differently and you still have to tune for your set-up and style.