Hi warriors !

I’m slinging since some months. It is really unbelievable and fantastic how far it is possible to throw a stone just with your own force when using a sling !

I was interested in how slinging physically works (especially also because at the beginning my range wasn’t what everybody was speeking about). So, now I’ve written an article - already posted by chris - with some physical formulas (addition of velocity, centrifugal force...). Of course the formulas, just written as text, are cumbersome. At a blackboard they would be much nicer and easier to understand. I’ve also added some pieces of advice for beginners (in order not to get their own stones on the head).

Alsatian

Welcome Alsatian

Thank you for your effort. Looks like you are skilled physicist and mathematician. We have just started the thread about physics of sling. I'm sure you could be very useful. So please, register your nick and start sharing.

Jurek

Alsatian, ....here's the "nut" to successful slinging.

1/ Any turns just keep the cords taut, and move the sling "into position".
2/ From "the position", it is a near whip-like snap that accelerates the stone before release.

I wish I could describe for you "the position".   It's just something you learn to feel.   My longest pitches are almost always from the slowest wind-ups.   I use almost x2 turns to release.  Some slingsters use more.  Some use none.

Hope this helps.    mgreenfield

I would add that it is imperative that one release as near to a 45deg. angle of inclination from horizontal as possible when  launching ellipsoid ammo which spins about it's longitudinal axis.  Such axis being parallel to the direction of travel.

Yurek

You picture 4 describes very closely the style I use currently. Mgreenfield is completely right when he says that a whip-like movement is the nut of slinging and that no whole rotation is necessary. He wants to contradict me but in fact what he says is not a contradiction to my explanations (even if just to compare the sling motion to the motion of another device is not a description in physical terms). Myself I sling exactly in this way: a whip-like movement without preliminary velocity ! I stopped to do complete rotations very soon because it was too tiring especially if you do hundreds of shots in a row. To shoot, I start with my sling hanging downward, I put my hand a little bit forward, then begin to move it backward, upward and end with a fast movement forward. The backward and upward motion put the sling into position but also gives me the necessary preliminary velocity to which the fast movement forward is added. For the onlooker it looks like a whip-like motion. And with this style I still get ranges around 80m. (But in fact I don’t use this style for range but instead to shoot at a target at 25m - with an orbit which is only slightly curved.)

Some time ago I tried to apply my „addition of velocities" theory too strictly. My style consisted of just a fast movement backward and a fast one forward. But I got timing problems. Because my snap forward was often too early, instead of getting an addition I often rather got a subtraction of velocities (as my snap already began when the sling had not yet travelled enough backward). So, to correct this timing problem, my hand had to wait until it fell the sling in the right position for the fast snap forward. But I too often missed the right position to begin the snap forward. I realised that the best thing is to begin with a moderate acceleration backward which I increase always more, the hand going upward and at the end forward with the maximum acceleration. So, instead of adding two fast velocities, now I rather apply a continuously accelerated acceleration in a curved motion. Of course in a bit simplistic explanation I could still say that I add the absolute value of a little velocity vector backward, the absolute value of a little velocity vector upward and the absolute value of a bigger velocity vector forward. That explanation is true enough to explain in a few words to a curious onlooker how the whole thing works. And of course you can describe each shot with a sling as the sum of an infinite number of infinitesimal straight accelerations of you hand. So theoretically at the end you could have a very accurate description of the sling movement. The problem is that you won’t find a closed solution and you will have to use complex mathematical tools as Taylor series (which implies that you have to make approximations depending on how exact you solution should be)... So, to explain in a book in a manner understandable for everybody how a sling works principally the simplest model is still my first explanation model (described in my article): Preliminary velocity vector upward where a velocity vector forward is added (overhand style).

Just to show you how complex it would be to find a mathematical solution for a given shot with the sling: Just a few days ago I saw the mathematical solution for the motion of a pendulum (for which I have given the equation in my article) in a physics book. But in this case this wasn’t just the trivial solution for little angles but the special solution for a pendulum which starts from the horizontal, falls down and moves up on the other side until it reaches again the horizontal. The whole solution went over several pages where complex mathematics as Taylor series were used. (And all this just for one special solution!) As any shot with a sling is more complex than this very simple pendulum movement, you can imagine the lot of work just to describe one special shooting pattern.

There could be still a difference between my style and the explanation with picture 4. You say that at the end you arm is stretched forward. Instead, I sometimes have the impression that in the end phase of my throws I tend to shorten my arm and that this adds a lot of velocity. It seems that here the principle of constant angular momentum for a central force is partly applicable.

I can imagine that with a bit of practice with the whip-like style with no prelimirary velocity one is able to reach 100m. But in my opinion - unless you are a giant - much more will not be possible. I’m sure that if one really wants to get high ranges - 200m or more - this style can’t give enough velocity. And in fact, you write that you use one or more full rotations. I expected that you need at least 2.5 full rotations. But, of course, first my addition of velocity theory is only a coarse approximation. Second: Probably you also throw a stone much farther than just 25m without a sling (which is my standard assumption for an average person).

It would be interesting to know if anyone has ever tried to get a maximum range with a whip-like movement and no preliminary rotation of the sling and of course the range he got.

Douglas
When doing a shot my legs are spread. At the beginning my weight is on my back foot and at the end it is on my front foot. So it’s probably similar to you movement in the end phase of a shot. (That is probably the same for most of the slingers.)

Thanks a lot Yurek for you long answear

Sorry for being unprecise. I should have said that you picture looks very closely like my overhead style for an observer on my left (I’m right handed): I put my weight on my right foot which is behind and move my hand a bit forward. Than I begin to move it backward, ever faster and end with a fast movement forward where I also put my weight on my left (front) foot. (I think that this is what Mgreenfield would describe as a whip-like snap.)

So, I don’t do a lot of rotations. The opposite is true as I just do about one half of a full rotation!!!

You say
„I believe that a average fit man is able to get about 25 m/s during single stroke, even when he pulls a sling with a stone."

If that is true I’m not an average person (but rather a disabled one) because I can throw stones (without sling) not much farther than 25m. And as air friction is probably rather low at this latitudes this means that my release velocity is about 16m/s. If you are really able to throw at 25m/s that should mean that you get over 40m without sling (22m/s is necessary in the vacuum to get a range of 50m). If that is the case I have no doubt that you don’t need a lot of rotations to build up the needed velocity to reach you high ranges with the sling.

Conservation of the angular momentum in a central force:
AngularMomentum=Mass.Velocity.Radius
So (as the mass is constant), a lower Radius means a higher Velocity. (It’s not only the angular velocity which gets faster.) For example: When a satellite describing an elliptic orbit comes closer to the earth it gets a higher velocity which again pushes it away from the earth.

So, last but not least, I would still like to know how far you can throw a stone without a sling.

Saludos

Alsatian,

You were precise, now I have got understanding of your way. Sorry, but I simply didn't get an idea, that it may be a style of slinging. I have just reminded, that I saw a movie on some website showing one girl, that was using just that style. So my picture may be mistakenly interpreted, indeed.

That way is very very ineffective. I'm sure I would get very poor ranges with that one too. But you may transform it easy into the nwmanitou's way, which is much better. I can't explain it, but look at his movies. It's pretty easy,  practically you should add  only some ingenious motion of the wrist.

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Well... maybe I exaggerated a bit. I will measure how far I can throw by the hand and let you know. But I'm sure it is a bit more than 25 m.

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Yeah, you are absolutly right. I simply made a gaffe. I will remove that from my post, because it may misinform.

Jurek