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Twisting Cords (Read 2770 times)
mgreenfield
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Twisting Cords
Feb 2nd, 2004 at 12:42pm
 
Every 360deg spin-up of the sling will try to twist the two cords around each other 360deg, ....unless the projectile rotates around the axis of the cords.    Potential problems of this behavior are:

1/ Inconsistent launches as twisted cords "untangle" on release.

2/ Misalignment of football-shaped projectiles upon launch.

Lightweight spherical projectiles probably rotate readily to keep the cords (mostly) untangled.    But I'd anticipate some problems 1/ & 2/ above when using heavyweight football-shaped  projectiles, especially if a multi-turn spin-up is used to launch these.

Has anyone any thoughts or done any experiments on this issue?   One thing to try would be to pre-twist the cords in the opposite direction, so spin-up actually UNtwists the cords for launch.   A cord grip with the retained cord exiting the hand close to the pinky finger spreads the cords apart and probably reduces twisting.

mgreenfield
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Ulrica
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Re: Twisting Cords
Reply #1 - Feb 2nd, 2004 at 2:14pm
 
Well, I did have my thoughts about it.

When I did some practice indoors. I put a stone into the pouch and make it stay there by a rubber band around it. Anyway. There I could study it without "loosing" my stone.

I tried to rotate without twisting the cord, but it was hard. My thought was to rotate and not move my wrist too much, so I just rotate with my arm somehow..

But I didnīt come to any conclusion...

Ulrica
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JeffH
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Re: Twisting Cords
Reply #2 - Feb 2nd, 2004 at 8:06pm
 
While I believe that twisting cords has some to do with technique, it may have more to do with the cords themselves.  I have never had any trouble with my 4 stranded, plaited cords.  I just make sure they are straight before I sling and all goes well.

Stiffer cords are certainly the answer to the problem, however.  I have slung a few golf balls with my newest sling and can tell that twisting won't be a problem.  Thick, heavy, stiff cords.  This should also be the case with the wire sling that whipartist made, but he will have to speak for that.

I know that thinner cords make for faster slinging, but the tradeoff is greater twist.  I belive that a nice sling could be made of stiff cords without much loss in performace.

Using heavier stones also contributes to less twist.  Another reason to go for the 5 ounce stones.

Jeff <><
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So David triumphed over the Philistine with a sling and a stone. (1 Samuel 17:50)
 
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Travis
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Re: Twisting Cords
Reply #3 - Feb 4th, 2004 at 12:29am
 
With the lack of real detailed information available to us about the exact techniques employed by the ancients, we are left to speculate based on ammunition (such as stones, glandes, etc)., and artists' images.

Perhaps one of the reasons certain slingers held the pouch in their non-sling hand, extended in front of them, was to do just such a thing.  They might have counter-wound the pouch quickly after, or as, they loaded it (and with practice, automatically), adjusting for a set number of revolutions based on their technique and the range of the target.  This may have been more practical with shorter, lighter slings used at closer distances, which would have used lighter cordage than the slings meant to hurl tennis-ball sized rocks, hence they would be more prone to twisting. 

Just speculation, but ????
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Gaius_Cornelius
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Re: Twisting Cords
Reply #4 - Feb 4th, 2004 at 8:58am
 
I have made conventional rope in much the same way that the ancients did. Indeed, the method has not essentially changed - it has just been mechanised. Rope is held together by a combination of twist and friction, if you strech it, the rope "wants" to twist. I would be pretty sure that conventional rope is quite unsuitable for sling cords.

Braided cord is another matter, it is much less prone to twisting when streched. The only sling extant from ancient times was braided. See here:

http://www.petrie.ucl.ac.uk/search/detail/results/detail.asp?01_objectidentifier...

There is a way to make a cord that will not twist at all. Such cord is a braid of yarns where half the yarns are twisted one way (S-layed) and half the yarns are twisted the other way (Z-layed). Medium and large synthetic fibre ropes made this way quite frequently; if you visit your local DIY store you will probably be able to find some examples. Such ropes not only do not twist, but are very flexible.

I have never seen any small diameter cords made in the way I have described. It may be possible to make your own S and Z-layed yarns from which to make a braid. Suitable materials might include dental floss. Grin
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Yurek
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Re: Twisting Cords
Reply #5 - Feb 4th, 2004 at 7:13pm
 
I often use the long sling that is susceptible to twisting. Lately even I used the sling with the 1.1 mm thin cords. I prevent twisting by the cords separation in the palm (2 or 3 finger separate the cords), next, I use the wrist and forearm durring the windups, next, I accelerate the sling fluently and often reduce a number of windpus to 1 or 2 before the whip. It works for me.

Jurek
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In the shape, structure and position of each stone, there is recorded a small piece of history. So, slinging them, we add a bit of our history to them.
 
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magnumslinger
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Re: Twisting Cords
Reply #6 - Feb 5th, 2004 at 1:22am
 
This is a good, and important issue.  Most of the fraying and wear I experience with my favourite slings is related to this very issue, as well as rapidly repated reloading and shooting quickly with the sling.  I believe the excellent quotation  of the elite Achaean/Balearic long distance slings with the extremely stiff, rigid triple cords which allowed these virtuosos to strike "not only the face, but any part of the face..., etc." supports the belief of some of the best slingers in the ancient world in the superiority of stiffened, non-bending, non-twisting long cords for the ultimate in long-range precision marksmanship with the sling.

On the old "Stoneslings" forum, from which many of us derive, and have been fortunate enough to regroup here at "Slinging.org", bigger, better and more dedicated than ever to our ancient, and ever-new sport/self-improvement skill, some of our slinging brethren and sisters had mentioned stiffening their cords with melted parafin wax dripped the length of the release cord, (or perhaps, both cords?).  I think that I should try this at some point.  We wax strings on crossbows to give them better life and efficiency, so why not?  Or perhaps just rubbing something in like violin resin or surfboard wax onto the strings occasionally would be enough to help.  Or you could just used a pine tree as a target, and when it bleeds sap from the gaping hole in its bark, rub the cords against the trunk to soak it in that.  I suppose I'm a pine sap vampire, anyway, since that's how I get my quick energy "food" when slinging on long mountain hikes in Korea, when I don't have any other food left.

Anyway, this would allow the cords not to twist, and would probably increase the efficiency of rotation speed, resulting in less cord lag/more efficient acceleration just before the critical moment of release, and would allow for a pinch grip rather than the still excellent, more sophisticated, but possibly energy-consuming separated finger grip, if one needed just a little extra edge when going for something like the world distance record (I know that Jurek knows I'm suggesting this mainly to him, as something to try in the future, if he thinks it might help him!:->)!

I know that if I use a rotation, my lines try to snag.  Usually they don't, but as they grow less stiff with wear, they begin to do sop often, and to fray against each other.  The projectile also will touch the release cord, as I can prove with the difference in wear patterns when I use jagged vs. non-jagged projectiles, which is why I agree that heavier projectiles and lighter, less obtrusive release lines are another key to avoiding this problem.  That's one reason I believe my use of the lightest possible materials in my own ultra-light "magnum" slings works so welkl for me.

I wonder, however, if waxing might add to the drag factor on my nylon fishing net line, whose main virtues are its combination of being both thin AND POUROUS to air resistance, yet cheap, strong and stiff enough to give excellent day-to-day slinging performance (possibly not, since the net pouch size doesn't seem to make a lot of difference due to similar qualities and composition as the lines).  I like the consistency of the perfomance of these things even if I replace the components, due to their inherent uniformity and consistency.  Since the major drag and resistence is supplied ONLY by the projectile, it tends to make for some very efficient slinging even for shorter length slings.  Even after using these things for several months (before I was using thick, spongy "weightless" polyurythane cord, and thought that THAT was the ultimate cord material...well, it DOES tend to resist twisting, and to untwist a little better!) , I STILL feel like a kid with a new toy every day I go out slinging!
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