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willie:

--- Quote ---There is a new LabRadar chronograph that tracks the speed of projectiles up to 50 yards out. I would love to play with one of those. I think much of the initial loss depends on how clean the arrow is released.
--- End quote ---

Thanks, Alan. I will see if I can find out more about that product. Have you seen one in action?

Am following your latest calcs with interest, as I hope to test some arrows soon.

avcase:
Here are some calculations to give some idea of how much the material used to make the arrow can affect its potential for ultimate distance. This is just based on a few samples I had around the shop. There is a big range in properties, especially with the softwoods. A friend of mine has this one Douglas Fir arrow that is far superior to the one I measured here.

So here, I kept the shooting at sea level, and varied the temperature and wind.


                      Distance in yards, 42 deg
                     -------------------------------
             Max                   Launch  Sea     Sea    Sea Lvl Sea Lvl
             Dia           Weight  Speed   Level   Level  +10mph   -10mph
Arrow         in.   mm   grains   (fps)   @40°F  @85°F   HdWind     TlWind
-----------  ---    ---  -----    -----   ------   -----   -----   ------
Ipe-Case     0.296  7.5    522     202     313    325      320       331
Sitka Spruce 0.343  8.7    275     251     315    341      330       352
Douglas Fir  0.341  8.7    363     230     320    341      332       350
W. Larch     0.319  8.1    374     227     328    347      339       356
 

avcase:
That table was a mess. I’ll try an image to see if it is more readable.

willie:
Alan,
are these arrows all simulations? I assume that they must fit well with you real life collected data. The .319 Larch
is an actual arrow?

avcase:
This is simulations. So this doesn’t take into account arrow wiggle from a finger release, or initial misalignment due to improper arrow spine.

This is what I am doing:

I have established a reference barreled flight arrow geometry that dictates the geometric proportions for a pretty decent performing flight arrow.

I developed a good approximation of the drag coefficient for this reference arrow.

I then do a spine test on a straight dowel that I intend to make into a new flight arrow. I also measure  the diameter, mass, length, span, and weight used for the spine deflection test.  Finally, I supply the finished arrow length and spine needed, plus some information about the stored energy and virtual mass of the bow.

The program then calculates the shape of the arrow needed to meet the spine and length requirements (based on the reference arrow proportions). It also calculates the new drag coefficient based on the new arrow geometry.  The diameter and mass of the arrows in my example are dictated by the geometry necessary to meet a required spine value.  These all have the same spine. So very stiff materials will generate a thinner arrow and v
ery dense materials will drive up the mass of the arrow. 

The arrow launch speed is dictated by the calculated arrow mass, stored energy, and virtual mass of the bow. Lighter arrows have a faster launch speed, heaveier arrows have a slower launch speed. The distance calculated  is just ballistics.  I can include the effects of temperature, altitude, and wind.

It is really pretty eye opening. It takes about 15 minutes to spine check, weigh, and measure the length and diameter of a dozen dowels made from different materials. After that, it gives instant feedback on which dowel should be the best to meet the requirements.

Alan

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