Failure Mode of Using D97 String on Unreinforced Limb Tips

[LoneRanger]

Hello,

There is apparently something different in the construction of limb tips which enables the use of these newer, high performance string materials, as opposed to the older B50. Could someone please explain the difference in construction of the tip? Also, how does a limb tip typically fail if a high performance string is used when it was not built to do so?

Thank you!

[Kirkll]

A lot of the older bows, and some self bows do not use a reinforcement on their tip overlays. Typically modern bows use a phenolic material of some sort that the string loop pressure is applied.

But….That’s not to say there aren’t natural materials like horn or antler material that could be used successfully. Even some hardwoods alone can be very effective if shaped properly.

The older bows without any tip overlays at all seem to suffer the most, and the non stretch string typically splits the fiberglass.

Another issue that can effect how the string wears on the limb tips, is how the tip notches are shaped. If the tip notches are not rounded into the limb properly , and have a sharp angle from the groove to the limb transition. This can allow the string to wear unevenly in the loop and it applies more pressure to the glass at the base of the tip notch which can result in splittIng the glass.   

Shaping tip overlays is an art form….

 Kirk

[The Whittler]

When a bow brakes useing low stretch string it's automatically the strings fault. When a bow breaks useing Dacron 50-55 string it's was a fault in the bow. You decide.

[LoneRanger]

That all makes good sense, thanks. I suppose padded string loops would help to reduce the pressure where the string contacts the loop. This would be at the expense of speed, in added weight at the limb tip.

I certainly agree that it is wise to play it safe with B50. Just curious on how bows actually fail from incorrect string type.

Thanks again!

[M60gunner]

It’s been awhile but I saw two bows that had split limb tips. One was Kramer LB the other a Damon-Howatt recurve. It was like the string split the laminations. This was back in the nineties before “padded loops” were used. Then bowyers started to add reinforcement as well.

[black velvet]

I have been at this game for 70 years now and have seen many limbs split way before the use of low stretch material. If it's going to happen it's going to happen doesn't matter what string material you are using.

[Mike Mecredy]

The initial question was about explaining the difference in limb tip construction.
So, in regards to tip construction;  to make a limb tip compatible for low stretch string material (anything other than B-50 and B-55) there are typically several layers of addtional materials lamintated onto the back side of the tip and the string nocks have a groove around the back and it keeps the string in a semi circular shape around the back, eliminating any corners or edges, giving it a solid, continuous bareing surface.   The material can be, layers of hardwood and fiberglass, phenolic, horn, antler, etc.   It's especially important on recurve bow tips.