I got an email from a friend regarding a problem you may have encountered in your coaching. Here it is.
I wanted to bounce something off of you if you have a moment. I had some unexpected issues with arrows over this past weekend when I was shooting my first FITA. I was struggling much more than anyone else with the light wind we were having. Right before the competition, I had been trying to tune in my new arrows that were acting too weak and I ended up reducing the point weight to 90 grains, which had them finally performing well in practices. I put up some personal best practice scores with my adjusted arrows right before the FITA round and was feeling good about my performance. I suspect, though, that the light point weight was my downfall and part of what was giving me such problems. My longer distance scores were the worst I’ve ever done in my life, however my shortest distance score (30m) was right on the money with my normal practice scores, even though the wind was the same and I should have been the most fatigued and dropping points at the end.
I bought my arrows slightly long and am thinking about cutting off a 1/2˝ and putting 110 grain points back in the shortened arrows. My theory is that that will have a similar effect as having the longer arrows with lower point weight, but will give me more ability to cut through the wind. However, I can’t find any literature online or in my many archery books about point weight vs. arrow length in trying to make adjustments to arrow spine. Which is a better adjustment to make, and is there any such equation such as “each 1/2˝ of length = 20 grains of point weight” or whatever? I’m not keen on cutting down my arrows if that might not give me the results I’m looking for.
Thanks in advance for any help or advice you can give!
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I doubt your point weight made all that much difference so it may or may not have been the source of your woes.
First I have to ask: when you were tuning in these arrows, did you have a reasonable centershot, plunger button resistance, nocking point height, and was your aperture centered above your arrow? If not, you were tuning to a less than optimal setup. It is always important to have a bow in a proper setup when trying to tune. If your aperture is off center, for example, you are then trying to tune your arrows to a dynamic spine that will compensate for a mis-set sight!
Most Olympic Recurve archers have a FOC balance point of 13-15%, so that is something you might want to check. (FOC guidelines are the equivalent of the “equation” you desire.) The vast majority of OR archers have 100 gr points (110 gr being in second place, I think), unless … you are shooting a very lightweight all-carbon arrow such as McKinney IIs, then 90 gr and even 80 gr come into play.
As far as wind stabilization goes, there are two strategies: use a heavier arrow (like Easton X10s) or a lighter arrow (like Carbon Tech McKinney IIs or Carbon Express Nano Pros or Medallions). The heavier arrows have more mass and therefore require more wind force to move them (inertial stabilization). The lighter shafts are faster and hence spend less time in the wind for the wind’s forces to act on them (speed stabilization). When an arrow is shot long distance, a higher FOC is generally desired to keep the arrow on track during those longer flight times. When I was shooting field archery a lot I was using 60, 70, and 82 gr points in very long arrows with little downside. But shooting FITA rounds, I was using 100 gr or even 120 gr points (again, in very long shafts).
So, research Front-of-Center (FOC) balance and how to measure it (it is easy) and check your current arrows. If you are close to 13-15%, then it was not your point weight that was a problem. If it is 6-9%, then maybe so.
If it was not your point weight, I suggest you go back to a basic setup and retune (nocking point height 1/2˝ above square, centershot has inside edge of arrow point visually lined up with outside edge of bowstring with string centered on the riser (visually), plunger pressure mediumish, aperture centered above arrow when bow is vertical (I just run the aperture down to the bottom of the sight bar and eye-ball it)). Also, you need to take off all vibration absorption devices (Doinkers, et. al.); they can only mask the feel of good shots.
You may find that the tune you had wasn’t all that good.
The reason the tune is so important is the tune establishes the launch angle of the arrows (at what ever angle the bow is being held), so if the centershot is way outboard, for example, the arrows are launched point left. Then the fletching has to correct for that, but if the wind is blowing more than a bit, that “sideways” launched shaft is going to be blown in unpredictable ways (the shaft itself is a bigger source of drag than the fletches) and you are going to have very large groups as a consequence.
I hope this helps!