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Top Secret Classified Flight Arrow

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avcase:

--- Quote from: willie on December 05, 2021, 03:12:43 pm ---
--- Quote from: avcase on November 30, 2021, 07:58:51 pm ---I have some arrows that consistently enter the ground at a much shallower than expected angle, which implies that the arrow is descending at a positive angle of attack.

--- End quote ---

Hi Alan,
do these arrows differ from your other arrows by fletching or mass distribution? or?

--- End quote ---

My best flight arrows tend to be on the edge of aerodynamic instability.  The center of gravity is usually close to the center of the arrow. But center of gravity is not the only significant point on the arrow. The center of pressure is equally as significant. On my arrows, the center of pressure is a short distance aft of the center of gravity.

I have put together some experiments to see if I can make some definitive progress in this area. For these experiments I have built a pneumatic arrow launcher and created a number of small and light arrows that I can easily change the center of mass, vane geometry, and vane position.  The arrows have a mass of only a couple grams, or about 30 grains, and are made from paper straws that have a hard polished cyanoacrylate glue finish to improve durability and help resist moisture. This helps keep the distances within 200 yards so I can run the experiments in a nearby field.

Most of my work so far is with qualifying the equipment. This started with a number of chronograph shots at different air pressures so that I have a good idea of the launch speeds. Over a 10 shot chronograph test, I rarely see 1fps variation for any given pressure and arrow mass. My plan is to shoot a group of six arrows at a time.  Four of the arrows will be adjusted for whatever variable I am studying (adjustments to center of gravity, vane geometry, etc.), and two arrows will be control arrows that never change. The control arrows will indicate if there are differences in atmospheric conditions, like wind from shot to shot.  On a perfectly calm day, I can consistently place the two control arrows in about a 1-yard radius circle at a distance of 130 yards away.  This means any differences in distance greater than this are probably driven by whatever variable that I might be interested in studying.

I have little doubt that a flight arrow can use drag perpendicular to the arrow shaft to slow its descent.  The big question is how to design this into the arrow so that it increases the distance the arrow travels. I am not quite to this point yet, but hope these experiments can help answer these questions. 

Alan   

Del the cat:
V interesting post Alan.
Great to see thorough and methodical experimentation, in what is a very tricky/almost-impossible area.
Thanks for sharing :)
Del

Selfbowman:
The arrow was to light and to much drag. Just an opinion.

willie:

--- Quote from: avcase on August 17, 2022, 08:26:55 pm ---My best flight arrows tend to be on the edge of aerodynamic instability.  The center of gravity is usually close to the center of the arrow. But center of gravity is not the only significant point on the arrow. The center of pressure is equally as significant. On my arrows, the center of pressure is a short distance aft of the center of gravity.

--- End quote ---

Thanks for the reply and my apologies for not seeing your response earlier.

your consistency with the pneumatic straw shooter must be satifying. seems amazing to me actually.  Is there a MK 2 for heavier arrows in the works?

Selfbowman:
Del I tried your arrow on a string going around . The interesting thing I found out was when the arrow went around like it should in flight. The string ended up 1to1-1/4” front of the centrifugal balance point. Did not matter if it was a broadhead arrow or flight arrow any arrow. Don’t know what that means . Just an observation.🤠

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