Hi everyone. I'm new here- first post.

Its been my habit for some time to pass Sunday afternoons up on a mountain behind my house, where I usually spend a couple hours enjoying the scenery, peace and quiet, and chucking rocks off of cliffs. Its a great deal of fun to watch and listen to stones fall through about 800 feet of air before crashing into the brush. Especially when they gain enough speed to "fly," and track forward like a frisbee. This week, I was throwing for distance, and in my wishing that I could acheive greater velocity, I came to the intellectual discovery of "the sling." So now I want/need one...

In pondering how a sling works, and how I'd like to build an accurate one, I keep getting caught up on this one issue of physics:

It seems to me that, by mere mechanics, the stone would be inclined to come in contact with the released line of rope on leaving its pouch, affecting momentum and accuracy. In my slow-motion imagination of the throw being released, the stone would begin moving out of the pouch as soon as tension is released, tangent to the arc of the swing. The stone would begin moving out of the arc, and thus, toward the outer line of rope. The released end of rope, however, would take some time to accelerate toward, and past the pouch, fully freeing the stone to move into open space. Basically, that because the stone would likely push into the rope before the rope could get out of the way, there would be some friction, and maybe even deflection before the stone got into open air.

So what's the real word on this? Does this actually happen? Or does the stone pretty much take off without any interference? I'd really appreciate some feedback.

Thanks a lot!

Umm scratch that about other replies... sorry....

If you sling hard enough with a heavy rock, you can make the sling crack like a whip.  When that happens, it means that the end of the release cord is traveling pass the speed of sound.  So I'd think that would be fast enough to get out of the way of the rock.  Even if it doesn't, it rarely effect the flight of the rock since it is much lighter and is moving out of its way.  Some wear and tear shows on the releasecords on my slings near the pouch.  I think that means the rock rolls out of the pouch and onto some part of the cord before it leaves the sling.

Some friction is inevitable between the rock and the pouch.  That can be used to your advantage if you sling with a overhand or figure 8 style since it adds underspin to the rock and give it more lift.  Using an open grip, that is holding the cords so that there is a gap between them before release, you can position sling so that the pouch is at right angle to the flight of the rock rather than behind it.  This would eliminate the release cord getting in the way and produce spirial spin on the rock.

Some slings are design so that the cords would not get in the way:    

http://www.slinging.org/membergallery2.html


Take a look at mitch robinson's nija star multi cords design at the bottom.  


I hope that helps.

I love sling from a cliff too.  the one I go to isn't that hign, about 20 meters but slinging from there seem like I could sling much further!


Oh, and welcome to the forum!

Quote:


I have wondered the same thing myself and think you observation is probably correct. The release cord of a sling shows wear sooner than the retention cord especially at the end from the whipcracking effect and also the first few centimetres, near the pouch, from the abrasion of the stone leaving the pouch. Heavy ammunition definitely leaves the pouch quicker than light stuff which tends to hang up and so fly low and to the left, (depending on your handedness and throwing style). This would also support the theory that the stone pushes the release cord out of the way. To get the best accuacy it is necessary to select stones to be as consistent in weight as practical. However when slinging with an empty pouch the release cord still flies forward under its own momentum which would indicate that the stone assists in, but does not entirely perform, the action of opening the pouch on release.

So much for the theoretical postulations. As others have said, some slings have been built with twin release cords so that the projectile passes between them on release. But whether the efficiency gains are worth the effort and extra risk of tangling is uncertain. By far the majority of slings ar built with only a single release cord as they have been for countless millenia. Build one for yourself and experience the thrill. Sure beats throwing the rocks by hand!

I have little experience with other than braided slings with woven pockets, and some with the Balearic style split. To me these 'feel' utterly different, I suspect because the dynamics of the release are influenced by the different style of pocket. I don't know if that matches the feelings of those with wider experience?
However, I recently made an 'andean' style sling with a much lighter and more flexible pocket, this feels to me much more like the Balearic style than my other 'andean' slings which I wove to give quite stiff pockets. I think one would expect that from a comparison of weight and/or stiffness distribution in the two kinds.

Certainly I get much heavier spin with the woven pocket. Examining them, I don't find any wear at all beyond the woven part of my 'andean' slings.

All the 'andean' slings I made and still possess have tapered release cords. I think this does help with avoiding 'hang ups' - but I don't still have the other sling to compare properly, it may be mainly that I am just a little better at slinging.

Wow. Maybe it's time for the annual revival of the "Physics" thread in the Project Goliath forum?

Dsparks,

I need to amend my previous remarks; I should have said, "almost unaffected by the release cord."

When you release the sling, the stone/ball/whatever is exerting a large outward force on the pouch and the cords.  The release cord is whipped outward very quickly.  Of course, it has to be accelerated, and the stone can be thought of as rolling out of the pouch, and often rolling/sliding along the first several centimeters of the release cord before it can get out of the way.  I recall Yurek posted a photo of one his slings, showing the release cord frayed for a couple of centimeters past the pouch.  Yurek consistently puts a rifle-spin on his stones, and the sling orientation required for that, puts the cord as out-of-the-way as it is going to get.

First, I appologize for being out of the loop for so long. Between work, a wife, and my infant son, I've hardly been online since I posted this.

Thank you all very much for the responses! They are a wealth of knowledge.

I built my first sling shortly after my original post, last weekend, and had a great time with it. It wasn't anything fancy: I took an old belt that I had sitting around (my father's, so significantly longer than one of my own) and I sewed cloth from an old pair of pants into the center for a pouch.

I'd have to say that I was impressed with how well a simple design like this worked- I took it up unto the mountain behind my house (which, to answer former questions, is in San Diego, California) and threw rocks for a couple of hours. I'm fairly certain that at one point, I was nearing 100 yard throws... I'll attempt to make a new pouch this weekend and try to improve.

From what I gathered as a concensus, and from my own observations, there is definitely some friction between the ammunition and the release-cord of the sling, varying according to the flexibility, weight, and length of the release cord. The weight of the ammunition, of course, must also factor-in.

I suppose its much like a bullet leaving the barrel of a gun- there is actually a great deal of friction for a bullet passing through a barrel, because of the rifling grooves: the barrel literally carves out a portion of the copper or lead in order to cause the bullet to spin, and this happens under rediculous pressures, creating quite a backlash of resistance. If you were to try to manually push a bullet through a barrel, it would prove more difficult than you'd expect. This works as sort of a flat-tax: the harder the bullet hits the grooves, the more energy is lost, but more is also present to lose (because the bullet is being pressed harder). In lighter shots, the bullet does not hit the grooves hard, but also doesn't have as much energy to lose.

So, I suppose that if a bullet loses, say 2% of its energy to the barrel, that 2% doesn't compare to the 500 ft. lbs. or so of force that it gains (for my trusty 357): I suppose a rock leaving a sling also has a proportionate "tax" on it, but of course, the energy gained far overpowers the energy lost.

Thanks again for all the great reading material guys (and ladies)! This is a great site, very friendly folks.

Happy slinging.

yep, it's enough of it being loose
read this thread if you are interested in slings with no-release release () cord: http://slinging.org/forum/YaBB.pl?num=1079645737