A model rocket is a lot like an arrow in a lot of ways. The same physics are at work. A rocket requires a little more stabilization, but it will fly stable as long as the center of gravity is forward of the center of pressure. There are a number of model rocket builders that have altitude competitions that resemble our flight archery competitions. The model rocket builders are also looking for that perfect balance of center of gravity to center of pressure. They need enough stability to keep the rocket on a straight upward path. An over-stable, point heavy rocket does not do as well because it tends to weathervane into every fluctuation of the wind currents that it passes through.
I do pay attention to the angle the arrows strike the ground. Every arrow seems to have a hard limit in how far it can be thrown. There comes a point where faster launch speeds from the bow makes little difference in how far the arrow can be thrown. If you start to notice the arrow starts landing at a very steep angle, like 75 or more degrees from horizontal, then this is a sign that the only way to progress is to work to improve the arrows. I experienced this first hand a couple of years ago at one of our Salt Flats events. I launched about 20 arrows from different bows over a wide range of launch speeds, launch angles, and wind conditions, and every arrow landed within +/-15 yards distance of each other! The arrows launched at high speeds went a little bit further, but landed almost vertically. The arrows launched at slower speeds landed at a little shallower angle, but still went nearly as far. It was as if there was an invisible wall that these arrows were not allowed to cross.
This led to a long process of trying to figure out how to break past this barrier. I was able to rule out atmospheric conditions by running into this same distance limit at completely different shoot locations and atmospheric conditions. I started playing around with arrow geometry and test shot my arrows alongside arrows made by past flight archers (arrows made by Harry Drake, Ike Hancock, and George Alavekiu). I found each of these groups of arrows had their own limits. Some were better than others. I considered an arrow topped out if it landed at an angle greater than 75 degrees. Faster launch speeds were a waste of time beyond this.
I even went as far as creating computer models of these flight arrows, and I used a fairly sophisticated model rocket program to shoot these virtual flight arrows at various launch velocities and angles. Funny thing is that these simulations showed the exact same symptoms that indicate the point of reaching the performance limits of a flight arrow.
The hard part is to figure out what to do to get the most out of an arrow. All I can say for certain is that there isn't a simple formula to make a great flight arrow. There are several factors that all interact with each other. I played around with several experiments to try to find some breakthrough. I tried an experiment shooting numerous arrows from a shooting machine that were identical weight, and identical nock and fletching geometry, but with different shaft geometry. Some were barreled with more thickness toward the rear, others barreled with more thickness to the front, others barreled with greatest thickness to the center. About the only consistent result from this indicated that the barelled arrows with more thickness at the rear performed worse than the rest. Also, arrows with more radical barrel tapering performed worse than arrows that had less radical barrel tapering. But it is kind of hard to isolate if this performance difference is due to the geometry differences, or due to shifts in the center of gravity due to the shape differences.
There's much more to this, but this post is long enough already. I will say that I did manage to break through the performance limit that I ran into a couple of years ago, but I am also sure there is still much to learn. For example, I cannot figure out how Harry Drake shot as far as he did using the equipment he had. I've ruled out the bows. They were very good, but not magic. It had something to do with his arrows and how they were shot. Pictures indicate Drake's record footbow arrows landed at pretty exceptionally shallow angles at distances exceeding 1-mile, but I don't understand how this was achieved. Drake's arrows were barreled with more of the thickness toward the front, and this pushes the center of pressure toward the front of the arrow. Drake's footbow arrows did not have metal points, but had a metal nock and steel razor blade vanes, which pushes the center of gravity rearward. My farthest flying arrows have similar properties, so maybe there is something to this.
Alan
