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Local conditions, drag and distance
joachimM:
I did quite some flight exercises lately, and was rather appaled by my results.
Bow-arrow combinations that gave me OK results last summer, yielded absolutely awful distances the past few days.
It has been awful weather, however. Lot of side wind, which increases drag quite a bit.
But still, I started to look for variables that could affect flight path, especially how local environmental conditions affect drag.
I knew altitude had and effect, but had no idea how large that effect was. The Bonneville range is at 1286 m asl. The air density at this altitude is about 15% lower than at sea level, which reduces drag by 15%. Say you shoot an arrow at the Bonneville flats and it flies 205 m (supposing a broadhead), it would fly some 8 m shorter at sea level.
Next, there is temperature: the higher the temperature, the less drag there is. At 25°C, there is c. 10% less drag than at 5°C (my current temperature).
Summer versus winter temperature alone would reduce my distance by c. 6 m.
Combining temperature and altitude, a flight shot of 205 m at the Bonneville range at 25°C versus at my place at 5°C would make a difference between 205 and 192 m.
That's rather considerable. And it makes me more comfortable not closing in on the 300 yard mark in flight with flight arrows yet ::)
Sources:
https://fogmountaintennis.wordpress.com/2014/06/05/atmospheric/
https://sites.google.com/site/technicalarchery/technical-discussions-1/trajectory
Badger:
I don't think it is that simple. You have less drag going into the direction of the arrow but you also have less drag that keeps the arrow from falling out if the sky downward. Cooler moist air tend to give better results that hot dry air for instance.
joachimM:
At high temperatures, moisture reduces drag, indeed. Bur at low temperatures the effect is much smaller and close to negligible. See attached graph, from the tennis paper.
willie:
Joachim
I wonder if the combined effects are worse than you estimate? Not all the corrections you cite are linear, (and I do not presume that your calculations/numbers are), but when combining factors to estimate drag, are the results simply additive?
https://www.faasafety.gov/files/events/NM/NM09/2013/NM0951144/Density_Altitude.pdf
the pdf has a nomograph that you might find interesting for comparision .
I realize not walking as far as hoped to get your arrow, can be disappointing, but not near as bad as failing to clear the tree at the end of the runway. ;)
--- Quote ---but you also have less drag that keeps the arrow from falling out if the sky
--- End quote ---
Steve, are you saying arrows might "glide" better with higher air density?
Edit: it is not exactly clear in the FAA publication if the displayed nomograph is adjusted for engine performance reductions.
this interactive nomograph might be more fun to play with. https://www.takeofflanding.com/
Badger:
Not necessarily glide but it seems to equal out advantages and disadvantages. Arrows are cutting through the air forward but also falling. Thin air is nice to cut through but it also doesn't give the good drag you want to keep the arrow from falling as fast.
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