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shooting with a jerk ;-)

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joachimM:
Turkish flight shooting with a sipher is said to be best with a sudden jerking movement, "mefruk". Instead of drawing a bow and holding it for a few seconds, the draw (at least the final part) is performed very suddenly.

Now it seems there is a very good physical reason for doing so: reading through scientific papers on all kinds of natural fibers (sinew and all kinds of plant fibers) I noted that the tests that are typically done with tension testing machines are performed very slowly, think in the order of millimeters per minute for samples of say 50 mm. That is very slow indeed.

One paper (and I forgot already which one) tested different speeds of tension loading, and concluded that the faster the extension is performed, the stiffer the material is (the higher its modulus of elasticity, its "draw weight" or stiffness), and the lower its maximum strain is.
If you slowly increase the tension, the stiffness is lower, but the maximum strain is also higher. 
For example in such tests, sinew can stretch up to 30% if the extension is performed very slowly. (Note that most of that extension is plastic, non-elastic deformation). Hair and wool can also stretch this way to at least 30%. Sisal fibers can thus stretch to nearly 15%, flax to 4%. But the force exerted to stretch these per unit of deformation is smaller than for fast stretching.

What's the relation with flight shooting?
The faster we draw and release the bow, the higher the immediate draw weight might be, and the faster the bow can shoot (for the same limb mass). I guess that's why the Turks used to shoot with a jerk.
there is, however, a risk of overstraining the bow in this way. 

just my thoughts. Maybe you guys already flight-shoot this way?

Joachim

Badger:
   I discovered this while shooting through a chrono, very effective technique.

PatM:
Jozsef Monus shoots with a slow "double" draw and holds at full draw for a long time. Not sure about the actual constituents of the bows he uses though. Including the all natural ones. ;)

Selfbowman:
If going for distance .release at full draw done quickly gets me about another 20 yd or so.   Arvin

Urufu_Shinjiro:
Hmm, I wonder if this would partially explain the FPS increase when performing khatra...

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