It's just the way they're shaped as a bit of a slope for me. I'd be afraid of my string eventually stretching over the single shoulder. If there was a peak keeping the string in place it'd only be a question of whether or not one point of contact is enough to keep the string from splitting the tip.
Ah, yes. I see how you could get that impression. Those two pictures, especially the one from the back side, don't really make it look like there is a whole lot there for the string to catch on. So I took a few pictures that will hopefully show the situation a little better.
Two bows side by side with the same style nocks, though they look a little different.
That's the view from the belly side. See how the strings kind of ride down and to the right? Because they do this they basically pull themselves
into the shoulder.
With this view from the side, you can see that the strings are secure on the shoulder and not risking sliding down further. If I made huge loops I might have to worry about that. But in general I make my loops just big enough -- they usually don't ride down the limb more than six inches or so.
And a view from the back side again shows the angle the strings sit at. The shoulders are wide enough to completely cover the width of the string.
So in the end, I can definitely see where nervousness could stem from, but I have perfect confidence in these nocks. Both in holding onto the string and in holding up. The bow on the right has probably been shot 1000 times by now (made in February) and the nocks show no sign of degradation. That's with "fast flight" (BCY Force 10) too. Every bow I've made has had self nocks, and almost every one of them I've put a low-stretch string on.
Another benefit is that these style nocks make stringing and unstringing very easy.
