Alsatian,
Quote:You picture 4 describes very closely the style I use currently...
That picture doesn't ilustrate any definite style, only shows a behaviour of the cords (changing the angle of their deviation), and the stone trajectory during the final stroke. Imagine that a slinger makes the stoke in the horizontal plane. Of course, it is a simplification in order to show the idea on the plane surface. It doesn't a matter what style a slinger uses, nitty-gritty is the same - the cords should make the additional clear turn around the palm, if he wants to get a really good shot. So, a preliminary motion of a sling should be enough quick in order to get a initial tension of the cords, but shouldn't be too quick, because it causes permature "escape" of the cords, hence a slinger can't pull them efficiently. I compared the centrifugal force to a spring which have variable rigidity. That rigidity grows up like square of the tangent velocity and the "spring" tries to erect the cords more and more during the acceleration. The trick is to chose such kind of initial motion, either trajectory or velocity, in order to get the suitable big initial angle of the cords deviation (the optimal range of the pulling angles depends on the L/R ratio), and don't let the cords to erect early, because it reduces your ability of acceleration of the sling and extorts permature release. Of course, the quicker slinger, the bigger can be the initial velocity of the stroke.
Imagine a running trolley with a spring on its back. If you want to accelerate it, you should overtake it in order to push (compress) the spring as very as possible in the first stage of acceleration, since you know, that in the next moment you don't be able run more and more quick and push the spring. When your acceleration starts became smaller and smaller, then the spring will start its work and give the stored potential energy back to the trolley, driving them additionally. I needn't say, what happens when the initial trolley velocity is bigger than your max. speed
In case of sling is similar. If initially sling isn't too quick, you are able to "compres the centrifugal spring", that does its work when sling becames too quick for your hand. In opposite case, you simply don't keep up with the sling and your joints, tendons and muscles take almost entire part of the unused kinetic energy on themself and the shot is poor. It also can hurt, we know.
Quote: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)...
I dont't think that Mgreenfield intended to contradict you. From your article and earlier post one could get an impression, that you overvalue an importance of speed of premilinary rotations for building the final velocity. I have got such impression too.
You wrote, for example:
Quote:To get 400m you need a release velocity of 63m/s in the vacuum (or even more if the release angle isn?t 45deg). That is 4 times the velocity of the fastest hand motion...
or
Quote:So, in my opinion, you need at least 2.5 full rotations or rather 3 as the air friction is probably higher as I supposed and not all you hand movements will have the maximum possible velocity.
As I know the fastest hand can reach velocities above 40 m/s durring a single-motion throw. Good baseball ptchers can do it. 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.
Quote: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.
I'm not sure, if you are thinking about the same thing as myself, when you use the term "whiplike". For me "to whip" mean the same like "to stroke", it is a simple violent move in a one direction, but you are usig this term for the complex motion. I have got an impression you are descibing the "nwmanitou's" style with the "nuber 8" loop for initiating the final stroke, maybe I'm wrong.
Quote:...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.
It is a true, but not all true. The gift of matter is in it, that you acelerate the stone along the longer trajectory than the palm's trajectory is, during the single stroke of the hand in the same time.
Quote: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.
I'm conscious how complex is to find a mathematical equations of a sling motion. I think the best way is to find a numeric solution. I suppose we should start solving from the lagrangian. I'm neither a mathematician nor physicist too, so it isn't trivial for me. It would be great if some day one make a sling motion simulator with a lot parameters and charts
Anyway, mathematical eqations could give a lot very interesting conclusions, but alas could't teach anybody slinging.
Quote: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.
It is just why my considerations are started from the known from experience behaviour of a sling
Quote: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...
Not exactly, I said this:
Quote:...We can compare the Fcf to a (more and more stiff) spring, which is indirectly diffracted by the Fa, and which gives the kinetic energy back just before the release. That gives an additional spur for the stone, and makes a shape and lenght of the stone trajectory more beneficial, bacause lets us to release the stone in a much more profitable moment (I mean, more to forward, when the slinger's arm is alredy streched)
Meaning of that is, that such kind of trajectory furthers a better using the full range of the efficient arm motion. As you can see on the picture, the release is when the arm is pointed between the 9 and 12 o'clock. If the cords erect too early you must release closer to the 12 o'c