Getting the right size string for your recurve or longbow is critical to getting the best performance out of that bow.

To do so, you’ve got to get a string that’s the correct
length for your bow, and has the correct number of strands.

LENGTH

When figuring out the correct length for your bowstring,
you’re likely to come across the acronym “AMO.” This stands for Archery
Manufacturers and Merchants Organization, and it represents a uniform system of
measurement for recurve and longbow bowstrings.

Let’s say you have a 68-inch recurve bow. You might think,
“Well, I need a 68-inch string.” What you need is a 68-inch AMO string, which
will actually measure 64 to 65.25 inches long depending on the bow and the
string material. 

According to AMO standards, the correct bowstring length for a particular bow is three inches shorter than the stated bow length. That is a good rule of thumb, but it’s not guaranteed to be optimal in every case.  The latest modern materials (such as BCY DF 97 or 8125 Dyneema) and string-building methods give us bowstrings that do not stretch nearly as much as Dacron B-50 or Flemish bundle-made bow strings. 

Dacron bow strings can measure up to one inch shorter untaught then they would under
100 pounds of tension, while a new material, such as BCY DF 97 or 8125, may
only vary by a quarter-inch. 

Using the correct string length allows you to achieve the
correct brace height to ensure quietness and maximum performance for that bow
once it’s strung.

Brace height can be easily adjusted by increasing or decreasing
the number of twists over a wide range in your bowstring.  For example, on a string for a 68-inch bow, anywhere from
20-60 twists will produce world-class results in order to get your bow’s brace
height correct.

Usually, the bow will have its length measurement printed somewhere on it. But what if you have a bow that doesn’t indicate its length anywhere? You can measure it for yourself.

Set the unstrung bow on its side on a flat surface. Now measure a longbow from string groove to string groove on the belly (grip facing you) side of the bow. For recurves, your groove-to-groove measurement should follow the curvature of the top limb, run straight over the riser, and follow the curvature of the bottom limb.

That measurement is the length of your bow, and the string
you put on it should have an AMO measurement to match it. Again, a 68-inch bow
gets a 68-inch AMO string.

By understanding this standard, you can then match a string
that doesn’t have an AMO designation with the proper bow. If a string measures
65 inches long, then you know it should be used on a 68-inch bow.

STRAND COUNT

A bowstring is a collection of individual fiber strands bound together by serving. Generally, you’ll find recurve and longbow bowstrings with anywhere from 10-20 strands. The number of strands needed in a bowstring depends on the draw weight of the bow.

Modern bowstrings for recurves and longbows are generally made
from one of two types of material – Dacron(Polyester) or Dyneema/Spectra (HMPE-
High Molecular Polyethylene). 

If your bow was made prior to 1990, only use a Dacron
bowstring to avoid damage.  Dacron is
more forgiving on limb tips and string grooves as it elongates, or gives a bit,
on each shot. Dyneema or Fastflight/Spectra bowstrings offer very little
creep/stretch and higher arrow speeds on newer bows.

Dyneema materials such as BCY’s DF 97 and 8125 offer even
less creep than Fastflight strings made of Spectra material. 

Bowstrings made of Vectran or Vectran/Dyneema blend are
rarely used on recurves and longbows due to the harshness created by zero creep
or stretch. 

The number of strands required for your bowstring can vary
depending on string material and serving thread.  Be careful to check your arrow’s nock fit
onto the center serving. It should lightly click onto the string, but not
require more than a tap on the bowstring to dislodge.

Here’s the strand guide our recurve and longbow experts at Lancaster Archery follow:

For bows with draw weights from 10-30 pounds, use Dacron strings with 10-12 strands or Dyneema/Fastflight strings with 12-14 strands.

For bows with draw weights from 30-40 pounds, use Dacron strings with 14 strands or Dyneema/Fastflight strings with 16 strands.

For bows with draw weights over 40 pounds, use Dacron strings with 16 strands or Dyneema/Fastflight strings with 18-20 strands.

Finding the “perfect” bow string for your bow can make a huge difference with accuracy, quietness and performance.  The most important factors are brace height and proper nock fit on the serving.