Author Topic: shooting with a jerk ;-)  (Read 8303 times)

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Offline joachimM

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shooting with a jerk ;-)
« on: February 02, 2016, 04:30:39 pm »
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

Offline Badger

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Re: shooting with a jerk ;-)
« Reply #1 on: February 02, 2016, 04:35:48 pm »
   I discovered this while shooting through a chrono, very effective technique.

Offline PatM

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Re: shooting with a jerk ;-)
« Reply #2 on: February 02, 2016, 05:39:30 pm »
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. ;)

Offline Selfbowman

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Re: shooting with a jerk ;-)
« Reply #3 on: February 04, 2016, 09:21:28 am »
If going for distance .release at full draw done quickly gets me about another 20 yd or so.   Arvin
Well I'll say!!  Osage is king!!

Offline Urufu_Shinjiro

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Re: shooting with a jerk ;-)
« Reply #4 on: February 04, 2016, 09:39:48 am »
Hmm, I wonder if this would partially explain the FPS increase when performing khatra...

Offline joachimM

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Re: shooting with a jerk ;-)
« Reply #5 on: February 04, 2016, 10:40:59 am »
I don't have the impression that khatra relates to the speed of loading and releasing an arrow. I have understood that khatra is aimed at reducing unwanted arrow oscillations by reducing the archer's paradox (thereby reducing lateral drag of the arrow during flight), through better control of the bow during release. See for example here https://www.youtube.com/watch?v=dTZkrmM5hx4
 
Joachim

Offline Badger

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Re: shooting with a jerk ;-)
« Reply #6 on: February 04, 2016, 02:11:07 pm »
  That woud be a good science for flight shooters to study up on. My belief is that we are having a much bigger problem with geting the arrows out of the bow cleanly than we are speed. Flight arrows are som individually unique it is very difficut to tune. I thing finding a style of arrow that shoots best and then experimenting with release techniques is our best strategy.

Offline joachimM

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Re: shooting with a jerk ;-)
« Reply #7 on: February 05, 2016, 07:08:28 am »
Badger, you're probably right that there are lots of gains in controlling arrow flight (like this khatra stuff). Until now, I thought of release techniques as controlling your arrow hand. But the bow hand is likely crucial as well.
I did try shooting with a jerk yesterday, but that really wasn't as easy as I thought, requiring much more force and control than I had expected.

Offline Badger

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Re: shooting with a jerk ;-)
« Reply #8 on: February 06, 2016, 09:53:44 am »
   I don't really think of it as a jerk, it is a quick but smooth motion. You want to get yur fingers off the string without allowing any forward creep of the string You want your bow arm slightly broken at the elbow so it is preloaded and ready to push forward right at release.

Offline mullet

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Re: shooting with a jerk ;-)
« Reply #9 on: February 11, 2016, 08:58:32 pm »
I do it when hunting, but a little more suttle, by squaring my shoulders and back muscles at the last second before release.
Lakeland, Florida
 If you have to pull the trigger, is it really archery?

Offline Badger

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Re: shooting with a jerk ;-)
« Reply #10 on: February 11, 2016, 10:19:38 pm »
  Eddie, I was shooting 50# hickory bow with field points into a 3/4" piece of plywood. I used a common target type release and the point never penetrated the other side at all. When I went to the dynamic release we use in flight it blew right through.

Offline mullet

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Re: shooting with a jerk ;-)
« Reply #11 on: February 14, 2016, 03:43:12 pm »
Steve, I don't know when I started doing it but I have released that way for a long time. I'm sure that's why my draw length is long for my height. I'm real comfortable shooting my Horn bows.

Do you remember a few years ago we were discussing that reflex/deflex bow that I shot a 209 through the Chrono, I was using a dynamic release then. A target release was getting in the 196 range.
Lakeland, Florida
 If you have to pull the trigger, is it really archery?