If you want to really get to know a new bow well, or perhaps just learn more about the influence a given part of the modern recurve/Olympic bow has on the system then you might consider following the example of the military.
Most will know that the typical soldier is taught to completely dismantle and then properly reassemble a weapon, so often that they will dream about it and even do it blindfolded. NOT suggesting anything quite so drastic for you or your archer, but as a coach you should do what I am about to suggest. Once you have done it you may see the value in having your students do this, particularly those that are showing promise of becoming dedicated to the sport. As I well know, the coach does not get to be there at the most important matches and it is coach’s duty to prepare the archer for those moments. Knowing the bow and ALL of the components and how/why/when to change them effectively is crucial to reaching the top step.
Start with: riser, limbs, served bowstring, arrow rest properly attached relative to the thickness of the arrow shafts, arrow shafts with nocks/points(no fletching), clicker if you will use one, and plunger.
Set the plunger to have no give, using Rick Stonebraker’s matchstick method, or else if it is a Beiter you can probably just tighten the spring down till it doesn’t move. We want raw influence, no “buffering” by the spring that might lessen visual evidence. Set the depth of the plunger to the skinny/shallow side, where it is just barely touching the side of the arrow shaft. Set the brace height to a middle-of-the-mfr-spec, and set the tiller to zero. Put the nocking point(s) to zero with a bow square. These settings are going to wrong to some degree (we want that!), and you are going to set them right by shooting bare shafts (only) close enough to the bale to not miss it, but far enough away to allow the arrows to be in the air as long as possible. You will want to pay attention to the symptoms, that is the way the arrows fly. Minnowing up and down, porpoising left and right, wobbling because of excessive weakness, flailing because of a grossly high angle of attack from a really wrong nocking point, skewing due to the hugely wrong centershot, are the clues you want to see, and ultimately eliminate on your way to perfection.
Also you want to note the angle of the arrow in the target. It will be off perpendicular, but with tuning you can make it less of an angle, and if you play your cards right, they will look just like fletching arrows! With X10 arrows, the barreling causes enough aerodynamic influences that even at 70 meters an elite archer will find his way to the gold routinely, regardless of whether there are vanes on the shafts.
Let’s start with the premise, that a perfect tune for the archer’s technique will result in the energy from the bow pushing through the center mass of the arrow completely, yes, well, “perfectly”. When it does that, it is a joy to witness, a knowledge of perfection for a brief moment. The feeling every archer strives for, “YEAH, I did that…”. When a bare shaft arrow porpoises, when it fish-tails, flails about, energy is being lost because it was injected off-center. So tuning is bringing the elements to balance, to harmony, to reduce the energy wasted outside of the center axis of the arrow. “Tuned”, the arrow behaves like a dart, and its flight is a beautiful thing of purity to behold.
SO! With the plunger “off” and the tension on the spring 100% so it doesn’t give, the center shot off, the arrow will minnow left/right. With the nocking point wrong, the arrow shaft will porpoise, up and down. Fix the nocking point first because it is simplest. For this exercise, use a tied-on floss nock, with sufficient tension so it can be rotated/screwed up and down the serving but stay set between shots. Shoot, adjust, shoot, till the arrow no longer porpoises up and down, or at least, does so as little as possible.
Next, change the center shot gradually by moving the plunger deeper into the riser and pushing the arrow further from the riser. As with the nocking point, you are learning the impact on the flight of the arrow this device has. And as the minnowing decreases you know you are getting closer to the better center shot setting. As it re-increases you know you have probably passed that point.
Through all of this you must decide each shot whether your release messed with the arrow too much and caused an energy diversion, or whether your release was as good as the tune at that point. Do you see truth or artifact? When you minimize minnowing, you might re-visit the nocking point position.
I was taught by the greatest coach I have ever met that tuning is like kneading dough. Adjusting the nocking point in the right direction is like pushing a ball of dough down, which makes it (the arrow pattern) squeeze wider. So you adjust the plunger, squeezing the ball taller, more vertical (the arrow pattern). Working in the right direction you gradually end up with a round ball of dough (the arrow pattern) that is smaller than when you began. The size of the ball at the end depends also on the spine of the shaft – a just-right spine’s doughball will be smaller than that of an arrow with too weak of a spine. You ask about the too-stiff spine? It will be smaller still but only when the release is perfectly consistent. A too-stiff arrow will likely be unforgiving of an inconsistent release. And once you have fletchings on the arrow, a too-weak spine will be more at risk for hitting the bow particularly with inconsistent releases. A slower release – stiff fingers – magnifies the flexing of the arrow, all other things being equal, resembling a weaker shaft – “dynamic” flexing.
Once honed to the best bare-shaft arrow behavior, the perfect plunger depth/center shot, the ideal nocking point (for that brace height/tiller), it’s time to start weakening the totally stiff plunger to find the best arrow flight again.
React to the arrow flight, the angle in the target, and the pattern of impact points on the target face. Remember that you will need to make smaller adjustments – for example, you may find that moving the nocking point by a single serving thread diameter yields a profoundly better tweak to the group!
Remember that fletchings serve to average out the imperfections – in the arrow shaft. The point weight/forward-of-center. The tune. The release. The wind. By causing the arrow to rotate through 360 degrees continually, the vanes reduce the flaws. They were critical when arrows were wood and vanes were feathers. As long as the device loosing the arrow is human fingers, there will be imperfections that vanes can mitigate.
SO that begs the question, in a perfectly tuned compound bow shooting with no winds, why are vanes useful? Well, a compound bow needs tuning as well. I suspect that due to the built-in accuracy associated with a bowstring in tracks with a string-guide, with a magnified sight with a level, and yes, with a defined wall and a mechanical release, most compounders never learn to micro-tune and are unknowingly relying on the vanes to mitigate subtle flaws in the tune.
Doing the things I suggest will result in a much better awareness/knowledge of the bow, the arrow, and the relationship the archer has to both. It may even result in better scores.