AMO and actual string length

[Norminator]

Is actual string length supposed to be 3 or 4 inches less than the AMO.

[JRY309]

I usally go 3" shorter for longbows and recurves if I don't have the old string to measure.Like my Martin Hunter 62" it takes a 59" string.My Venom 66" takes a 63" string.I like to measure to actual bow from nock to nock when I make a string for one of my bows.I've had three 64" longbows and they all three were slightly different lengths upto 5/8" difference.

[michbowhunter]

3" for both.

[John Havard]

michbowhunter is absolutely correct.  Lots of people have the strange notion that the AMO standard is different for recurves versus longbows.  It is not.  

The AMO (now ATA) standard says that a bow that requires a string of X" length (stretched between two 1/4" diameter pegs under tension) that YIELDS THE PROPER BRACE HEIGHT results in a bow that's X+3" AMO length.

So, a 60" AMO recurve OR longbow requires a string that's 57" in actual length.  

The only fly in the ointment is that quite a few bowyers do not know what the AMO standards are and mark their bows improperly.  

The reason the standard was developed was to make it simple for the customer/consumer/archer to know exactly what length string to order when they need a replacement.  If a bow is marked properly (like 66" AMO) then you know that it needs a string that's 63" long.  Simple if everyone would follow the standards.

[Jeremy]

Another thing to note is many stringmakers don't measure their strings properly either.  

Here's a copy of my rant on another thread  

 

The confusion, then and now, is bowyers and string makers not going by the standard. The standards were adopted for a reason.

If a bow is marked 64" AMO it should need a string that measures 61" under tension. A 10 strand string out of dacron that measures 61" under tension will measure under 60" resting. An overbuilt FF string measuring 61" under tension will measure right around 61" when resting.

I should be able to order 6 strings, all with different strand counts and out of different materials for my bow by just giving the AMO length of 64". That was the whole idea behind adopting an industry wide standard. Those 6 strings will all measure differently when resting, but they should all measure 61" under tension and after settling in.

I should also be able to put those 6 strings on any of my 64" AMO bows.

Bowyers not going by the AMO standards or, worse yet, not going by the standards and marking their bows "AMO" is a HUGE pet peeve of mine. String makers not measuring or marking their strings properly is a very close second! And the ones that send out a 61" string that wasn't pre-stretched so you have to twist it up like crazy...  

Ok, end of rant.

[Night Wing]

When I buy a custom bow from a bowyer, I let him tell me what length the bowstring is. When I called Norm Johnson and asked him what is the string length for my 66" Blacktail take down recurves, he told me 62".

So, when I order a new bowstring from a string maker, I order a 62" string.

[zepnut]

If a bow says 62" it does not automaticaly mean a 59" string. I've already measured and found a 3/4" difference. Most often on older recurves.

[RM81]

Yeah, I agree with Jeremy.  I've had it go from 2" shorter to 4" shorter on some bows to get the correct brace height without too much twist.

[Swamp Yankee]

Yup, the AMO "standard" simply isn't adhered to anymore.  You have to ask the bowyer or measure a string that works and ask the string maker to make a string that will match the one that works after it's shot in.

[Dave Worden]

The AMO standard is what it is; loop to loop length is 3" less than the AMO number.  It has nothing to do with the length of the bow as measured along the belly.  Doesn't care if the bow is a recurve or longbow.  All that being said, if they were trying to make it easy, why the 3" difference.  Why didn't they just say the AMO length is the length of the string which properly braces the bow?  Then the the AMO and loop to loop would have been the same.  End of confusion.  
When I order a string, I order the loop to loop length and have the seller measure the string for me, regardless of how it is marked.  As mentioned above, there is too much confusion among bowyers, string makers, shooters, catalog houses, etc.  If a catalogue house is not willing to open a string package and measure it for me, they don't get my business.  That is the ONLY WAY TO KNOW WHAT YOU'RE GETTING!