AMO string length

[JamesV]

if a recurve is 48" AMO how long would the string be? This is a fiberglass kids bow.

[yamapup]

The consensus is that for a recurve the string should be 3 inches shorter than the AMO. I guess that would also apply to a short fiberglass bow as well. In your case a 45 inch string should work just fine. Pup

[SEMO_HUNTER]

The rule of thumb seems to be -3" from ammo length for recurve and -4" for long bow. That's what I go by and it seems just about right for my Grizzly and my Osage longbow (self bow)

I have read other places where it's -4" for recurves depending on who you talk to or what you read, but I think that's just a bit too short?
If you go 3" shorter, then you can always twist another 1/2" or so out of it to get the proper brace height.

Alot of it will depend on your brace height for your particular bow, how old it is, string material, amount of stretch, ect.
I know that some string materials just don't stretch at all, and others stretch quite a bit.

If using old style string material on older style bows, you'll probably get quite a bit of stretch before the string settles in. My experience with that is a string that's a bit shorter will be about perfect once it settles in.

I make my flemish twist strings using the -3" and -4" method with B50 and it works out nearly perfect. I can them add a bit more twist to keep the brace ht. where I want it, and after about 50-60 shots it stays put.

The problem with an even # AMO is you will find a hard time getting an odd# string length, so you will have to go up 1" or below 1" and add twist for the longer one, or just count on some stretch out of the shorter one.
Or have one taylor made for your bow length?

Have you actually measured your recurve from nock groove to nock groove to make sure of the exact length? I'd do that first then subtract 3" and see what you come up with.

Don't know if that helps or not?

I'm sure some string makers will jump in here and offer their expertise and correct me if my way of thinking is wrong?

[LBR]

AMO/ATA says, basically, 3" shorter--longbow, recurve, whatever. It's stated differently, but that's what it amounts to.

 http://www.texasarchery.org/Documents/AMO/AMOStandards.pdf

[smokin joe]

I know that Bear recurves from the late 60s through the late 80s all were  minus 4". So a Bear Kodiak Magnum, being AMO 52" would use a 48" string -- and a Bear Kodiak Hunter with an AMO length of 60" would need a 56" string.

Modern recurves seem to need a minus 3" string. I have a fairly new Bear TD from 2002 -- "A" riser with #3 limbs -- that is a 60" AMO bow that needs a 57" string. The same limbs on an "A" riser from 1972 need a 56" string.

It was a bit confusing at first until I figured out that the AMO string length had undergone a change at some point between the late 1980s and 2000.

Joe

[smokin joe]

I forgot to say that I really don't know what the standard for a kid's bow would be now. When my kids were little it was  minus 4, but that was a long time ago, and they were using kids bows that were old then.

[sffar]

In my limited experience the 3" shorter for either type bow doesn't work. Fine for a longbow, but every recurve I've gotten a string for has needed more like 4" shorter. I realize the AMO standard is 3" for either style bow, I just can't see why.

[JamesV]

Thanks guys,

[LBR]

I forgot to mention that the string is to be measured under 100# of tension, except for very light draw weights (50# for those, if I remember correctly).

Going by AMO is a shot in the dark.  For some it works, for others it doesn't...but it can be a good starting point either way.

Chad

[John Havard]

Unfortunately for the customer Chad is 100% correct - depending on the bowyer the AMO/ATA standard may or may not apply.  I have one bow made by a well-known company that's supposedly a 60" bow but it needs a string that's almost 59" long to properly brace it.  

If a bow is marked "XX AMO" then it should mean that a string that's three inches less than "XX" will leave that particular bow at a brace height that's appropriate for it.  I know that our bows are specifically designed to be true to AMO standards.  If every bowyer adhered to that standard then there would be zero uncertainty when the customer was deciding what length string to order.  As I said earlier, however, it's unfortunate but true that some bows are not marked appropriately.

[CG]

Typically (though not always), a 4" shorter string is used when the material is B50 (or B500). That length will usually provide the same brace height as an HMPE fiber ("fastflight") string made 3" shorter.  

IMO, that's part of the reason for the confusion concerning 3" vs. 4" shorter.

[LBR]

That can be part of it--that's why AMO/ATA says to measure the string under tension.

However, I've seen bows get HMPE strings anywhere from 1.5" shorter than the bow length to 4" or more shorter.

Like John said, there's just some bowyers that don't go by AMO/ATA specs.  That's why I always ask for actual string length before making a string.

[John Havard]

The whole reason that the AMO came up with a standard was to benefit the owner of the bow.  If a bow was marked properly then the owner would ALWAYS know what length string to buy.  I feel for folks like Chad who make fine strings and try to help archers get the correct string for their bow.

AMO standard calls for a string to be 3" shorter than "AMO length" (when measured under 100 pounds of tension stretched between two 1/4" diameter pins).  That way there's no confusion on what length string to buy.  If a bow needs a string that's different from that then it isn't marked properly by the bowyer.

[CG]

Agreed Chad/John....After reading my post, I think I was a little vague.  You are absolutely right that very few bows use true AMO length strings.  The only point I wanted to convey was that a dacron string is usually 1" shorter than its HMPE counterpart when both produce the same brace height.  Assuming a true AMO bow, then the 3" vs. 4" variation.

[Dave Worden]

I see this question over and over on this site.  The AMO booklet is available through the How-To section.  AMO string length is ALWAYS 3" shorter than AMO length as marked on the bow.  If the bow is marked wrong, then one can only guess at string length.  As for the 100# stretch, if I buy a string that's marked AMO 50, I expect the string maker stretched the string properly to 100# and 47" long.  If not, then it shouldn't be marked as AMO 50.  There is no rule of thumb for the AMO standards, they are precise.  Confusion comes about when people confuse the 3", 4" rule of thumb for bowstrings on longbows and recurves when measured along the belly and whn people mark something as AMO when they did not follow the standards.  As for the kids bow that started this conversaion, an AMO 48 string is the string to buy.  If you're making it, make it 45" long when stretched to 100# tension.  BTW many bows make today say XX for the length but do not say AMO XX.  Don't loose the original string or you'll be flat out guessing how long the make a replacement!

[Fischman]

All good info guys. I like Dave's idea of not loosing the original string makes it easier for us guys making a new string not to guess about the length it should be. Personally i have many extra strings on hand just in case someone doesn't have a string to compare with, you can always twist-untwist a little and figure out which length to build for that bow.Those extra strings come about from bad guesses over the years and so you just keep them in your kit!!