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Flight arrow design & tradeoffs

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Badger:
    Tradeoffs in stiffness for smaller diameters is something I have been debatiing. I can make 200 grains with pine and maintain good stiffness but a larger diameter. With the larch I have been using I can get the diameter down to .25 or below and my weight to 200 grains but struggle with enough spine. I think the larch would be ideal for 80# bows and above.

avcase:
Michael,
There may be an error in the spine deflections reported in the following report:

http://margo.student.utwente.nl/sagi/artikel/turkish/

Notice how the arrow deflections are listed from higher to lower, but arrow diameter is listed lower to higher. The trend is perfectly opposite what it should be. I think the author may have typed in the deflection data backward. I'd expect the .25" diameter arrow to deflect 0.88", and the 0.30" diameter arrow to deflect .33", not the other way around.

The 0.58" average deflection of the 18 arrows, with an average diameter of 0.27" is more plausible, but still outstanding.

Arrow stiffness is proportional to the diameter raised to the fourth power, so a very small diameter difference makes a very large stiffness difference.

I believe I can match the average deflection of the Turkish flight arrows using a high grade of heat treated Sitka Spruce. I plan to make a serious effort at it later this year.

Another observation, these Turkish flight arrows averaged just over 190 grains, but they were shot out of very heavy bows. If we assume one of the lighter Turkish Flight bows pulled 125 lb, then that would be the equivalent of shooting only 76.4 grain arrows out of a 50-lb bow!

Alan

avcase:
I believe that a 200+ grain flight arrow for a 50# flight bow leaves a lot of untapped potential unless the bow has a long draw length.  By long draw, I mean the arrow is drawn 26" or more past the arrow contact point or arrow rest on the bow.

The trade-off going to light arrows is that the arrow becomes much more sensitive to tuning and release issues. Excessive paradox/wiggle has a huge effect too. Wind tunnel testing indicates that paradox on even a very well tuned arrow shot by an Olympic-level target archer can induce double the drag of an arrow launched from an air gun without paradox.  The same doubling in drag was shown for an arrow launched with as little as three degrees misalignment to the direction of flight.

I have a pretty extreme example of this from my foot bow shooting last year(sorry, non primitive).  Only two arrows were found on my last day of shooting. Fortunately, I have video of these shots and saw that my release loop broke at just past half draw. Based on my chrono testing, that arrow was traveling around 480 fps, but it left the bow very clean, and landed nearly 1300 yards away. The release loop broke free early on the other arrow too, but it was drawn 3-4" farther than the first, and probably left the bow around 580+ fps. But I had also forgot to tighten the arrow rest and it was blasted off the bow with the arrow. I assume this resulted in a misaligned arrow launch because the second arrow landed a few hundred yards SHORT of the first, despite the longer draw and much higher launch speed.

Alan

Badger:
   Allen, those are just the kind of things I feel we really have to learn to control if we ever want to establish some serious records. The year before I entered flight shooting I had a very light but very stiff river cane arrow, taperred from front to back that weighed about 240 grains with a 60 grain tip up front. I got better distances from that arrow than I am getting today from much faster bows. I hope in the future you will open some threads on this topic and discuss it more at length.

redhawk55:
Alan, I suspect the numbers to be somehow wrong, but Klopsteg is Klopsteg, almost every info about Osmanian flight- arrows are based on his researches. Thanks for clearifying.
Your post has driven me much more suspicious. A 76grs. arrow shot by a 50lbs bow will explode.
Asking a turkish friend and consulting wikipedia is showing that maybe the "avoirdupois" method used by Klopsteg for to convert the weights is wrong!
Obviously Klopsteg used " dram" instead of "dirham".

Go here: https://en.wikipedia.org/wiki/Dirham and here:https://en.wikipedia.org/wiki/Avoirdupois

An Osmanian dirhem(dr.) is equivalent to 3, 1gr. or 47grs.. So these arrows are weighing at an average of about 320grs., which is much more realistic.

Nowadays flight- arrows are matching these measurements quite exactly, no more brain racking over it!

Klopsteg, where had you been last night?

Michael

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