October 28, 2010
By Randy Ulmer
The fit between the arrow nock and the bowstring can affect accuracy
By Randy Ulmer
Most archers believe a tight fit is best. The author believes that when using a string loop, a looser fit may be the way to go.
As you may have noticed from reading my columns, I am a stickler for details. Most serious archery hunters and competitors understand all the obvious issues affecting accuracy, but often you gain the most decisive advantage by sweating the small stuff--the stuff that everyone else overlooks. For example, I have long wondered how the fit between the arrow nock and bowstring really affects accuracy. I have always felt that a tight fit was the way to go, but after watching a number of slow motion videos showing arrows being released, I now have my doubts.
If you have never watched an arrow launched in slow motion, you really need to make a point of doing so. You can find sample footage on the web by doing a search under "slow motion arrow flight." It is shocking to see how the sudden release of energy rattles the bow and its accessories. I was particularly surprised by the amount of movement exhibited by the bowstring nocking loop. It flops to the side and twists the string dramatically at the moment when the arrow snaps free. This twisting action of the string must affect the flight of the arrow even if only slightly.
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Q & A With A Professional
Randy: How tight (or loose) do you think a nock should fit for maximum accuracy and forgiveness? The more slow motion video I see, the more I think that a loose fit is best because the amount of string twist caused by the nocking loop. It seems that if the nock were tight, the twisting motion at that critical time in an arrows flight might cause some inconsistencies down range.
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Also, what serving material would you recommend that isn't malleable, so the serving will maintain a perfectly cylindrical shape inside the nock even after thousands of shots? I know monofilament nylon might be best, but it is impractical because it tends to break. What are your thoughts?
Mike Slinkard: I have played with nock fit quite a bit, and now I want my nocks to snap onto the serving. However, when they are on the string, the nock should be able to slide up and down with little or no pressure. As you state, the string is twisting inside the nock during the shot, and with a loop, this is even more pronounced because the weight of the loop itself will intensify this action. In my mind, if the nock fit is loose, then this twisting action will have much less effect on the arrow and deliver it more in a straight line out of the bow.
Of course, you really need the nock to snap onto the string to keep it in place, especially in a hunting situation, but that "snap" off the string really does not occur until the arrow is leaving the string, and then twisting could only affect it for a very short time before it is gone.
From a practical standpoint, I have seen better arrow groups from nocks that fit as I just described, especially with broadheads. All this is really one of the main reasons our strings come with the .021-inch diameter serving instead of a larger size. I believe, for most shooters, it will yield a more accurate shot and be easier to tune. Of course, this all depends on the nocks a person is using, but for the most part our 20 strand BCY 8125 strings with .021-inch serving will produce the correct nock fit for most regular sized nocks such as Super-Uni nocks and large groove G and X Nocks.
As far as serving material goes, probably the best stuff out there for holding its shape is the BCY Halo in .019-inch diameter. However, Halo is a little more susceptible to separation, which is a definite negative. Some of the top shooters we have on staff use this center serving with great results. This diameter will provide even a little looser nock fit than the .021-inch material but it is still within the acceptable range. Our standard center serving is our exclusive X-Braid Plus, which also holds shape very well and does not have any separation issue.
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