8125, 652, 97, 99, 450, 8190, 777 ... bingo??? It sounds like the number edition of alphabet soup. What does all this mean and how do I choose the best string material for my needs?
Let's start from the beginning. Where do string materials come from? The raw fibers come from these 5 manufacturers:
Dupont - Dacron polyester fiber
Honeywell - Spectra HMPE fiber
Toyobo - Izanas SK60 & SK71 fibers
DSM - Dyneema SK75 & SK99 fibers
Kuraray - Vectran fiber
All our string materials are one or more of those base materials. So how does it get so complicated? I've spent the last few months mapping this out:
Different materials will have different characteristics and figuring out your preference for each will help you determine what bow string material is right for you.
The chart above is organized by stretch with the most stretch on the left and the least stretch on the right. Why does this matter? The more stretch in a string material the more shock it will absorb when you shoot. If more shock is going into your string then less shock is going into your bow. On the other end of the spectrum is a dry fire, where all the shock is going into the bow because no energy is being transferred to the arrow. We all know that much shock is bad for a bow and can cause serious damage and injury. Well the stiffer a string material is the closer it gets to that end of the spectrum.
In talking with Douglas Denton (the recurve engineer at Hoyt) he says he recommends 652 Spectra and 8125 was his second choice. He shared that at Hoyt they did a 3000 shot dry fire test to test out new risers and when a set of limbs breaks, they just put on a new set and keep going. When they were using BCY X as the string material they went through 52 sets of limbs before encountering riser failure. When they used 652 Spectra they went through only 16 sets of limbs. The stiffer material (BCY X) is clearly much harder on the limbs and caused them to fail much faster.
The stretchier materials will give you less arrow speed while the least stretchy materials will give you more arrow speed (at least when it comes to Dacron, Spectra, and Dyneema fibers). BCY says Vectran blends will be slighter slower than pure Dyneema or Spectra.
Strings with more stretch can feel "squishy" or "softer" than strings with less stretch. Stiffer strings tend to feel a bit "snappier" or "more responsive".
Stretchier strings tend to have a longer break in period and the brace height needs to be checked and adjusted more often. Stiffer strings won't move as much (if at all) and the brace height will remain more consistent.
With a stiffer string, more energy is going back into the bow. If you are shooting a modern recurve with reinforced limb tips, that may not be a big deal. However if you are shooting a traditional bow or one without reinforced limb tips it may not be able to handle the shock after each shot. This vibration can cause small cracks to form over time and you may not notice until you have a catastrophic limb failure.
Bow manufacturers may have recommendations for what material is to be used with their bows but not all of them include such information in their user manuals. I've reached out to the major olympic recurve and barebow manufacturers and asked them:
Do you have recommendations for what type of string material should be used with your recurve bows?
Are there any materials that would void a bow's warranty and should not be used?
Here's what they had to say:
Anything with Vectran in it should not be used for recurve or longbows. It is only appropriate for compounds. It's too stiff and will put too much vibration into the limbs.
BCY 8125 and BCY D97 are the same material, but different diameters. D97 is much larger than 8125.
I have reached out directly to the manufacturers in collecting this information. If anyone has contradictory information, please reach out and provide your source. The goal here is to provide complete and accurate information so archers can make the best choice for their bowstring material.