I asked a golf playing buddy of mine about the speed of a golf ball when it leaves the club head.  He said the big guys are sending the balls away at about 175 mph +/-.  This is over 250 fps.

To achieve this velocity, you would have to sling about an 8' diameter circle at 10 revolutions per second.  I find it hard to believe that anyone could achieve this velocity within any reasonable style or level of practice.

Indeed, I think most of us probably attain to about half that with some practice.

So, maybe the dimples would get us something, but It would be, I strongly believe, immeasurable.  My calculations on bullets with greatly differing ballistic coefficients shows that at velocities 10 times the 10 rps above there is no appreciable difference when fired at the same velocity.

So, I think that dimpling a stone or glande would be a waste of time.

jeff <><

Correct, David, but it is still hard to believe we can achieve the equivalent of over 250 fps, snap or other accelerating technique notwithstanding.

I did not mean to imply that rps is the only or even the actual way we should/can measure our velocities.  It was conveinient for the discussion at hand though and is relavent for discussion.

Did I mention that I find it hard to believe that we can achieve the velocities that golfers do with the club/ball combos?

jeff <><

I think that I am not so much arguing theory here as I am reality.  Certainly, slings of greater length would generate greater velocity.  That is if you could swing it that fast.  There is a limit to how fast I can sling with any given weight and length of sling.  I think that at some point the increase in length would begin to show up as a decreas in rotational velocity.  This is because of the dynamics of the sling itself and that old gremlin conservation of energy.

For instance, when I swing one of my bullroarers it is obvious that it slows down as I let the string out longer and speeds up as I pull it in.  We only have so much energy and speed built into our shoulders.  Overcoming the longer sling to get more velocity would not be as easiy as it seems.  Besides, a 57" sling would require me to hold my sling hand above my shoulder just to keep the stone off the ground prior to slinging.  Now, the human ergonomic comes into play in another way.

In practical terms I think the sling works like a bow or gun in that there are limits that can't easily be exceeded; even with increased x, y or z ellements of the device.  An 80 lb bow does not shoot faster than a 50 lb bow of similar design by any appreciable amount, it just shoots heavier arrows at the same velocity.  All cartridges based on the 30-06 shoot bullets of similar sectional densities at similar velocities. But, if you shoot the same weight bullet in all of them you get very different velocities or sometimes dangerous pressures.  With both the bow and gun you can increase the velocity only so far.  Then you begin to risk either damage to the gun/bow or wasted energy that cannot be applied to the projectile.

This probably seems irrellavent, but in reality it is not.  The dimples may increase the range of a golf ball but a stone from a sling is a different matter.  In fact, a stone thrown overhand would actually hit the ground faster if the dimples had such a great affect, since that stone would have top rather than bottom spin.  We can't expect to get consistent direction of spin like a golfer.  And besides, even if we could, we still have to ask how much would the dimples increase the useful range of the sling.  Without great study it is probably not to be known, but still seems like a moot point due to the likely small improvement for the effort invlolved in making dimpled projectiles.

All that said, I would happily throw anything handy fromo my sling, cute dimples or no.

jeff <><

Well, they just throw a really long way.  How else could they get the rock so far?

I could not resist that.

Chris and David,  sorry if my posts have seemed obtuse or argumentative.  Not intentional at all.  I really don't know how much velocity is produced, I am just naturally skeptical about large numbers without proof.  I have no problem believing that a stone has been thrown in excess of 1000 feet.  This obviously happens and takes a lot of velocity.

My contention is with the supposed effect of dimples.  Sure, they are great on the smiling faces of  4 year olds and get your attention every time.  But on stones from slings?  I just can't see the return on the investment of making them (just as Chris said.)

So, just ignore the previous posts and suffice it to say that I am a believer in the mighty power of the sling.

jeff <><

My wife asked that State Trooper who brings his child to our daycare if he thought his radar gun would work on slingstones.   He told her that he just got one of the new high tech ones but could not really say. I need to set a definate time to meet him an see He is willing and interested.

Then all we have to do is "FEDEX" Yurek in a box to SC, USA from Poland so he can sling the stones or lead glands while we try to get a reading on them. I wonder if "lead" would record easier than a stone on the radar?? Hey, while we are at it, we could test for a Stylth?, stelth?,  shape for our glandes 8)

Got to run but I will ask my wife to ask the trooper for a time. Then we wil at least know how fast this old ex-baseball player can sling a stone. Then you science guys can try to extrapolate my arm mass and length to Yurek's arm and mass --taking into consideration that he has a beard and I do not, of course we Americans have bad jokes  about those from Poland so you would have to consider that factor. One thing that may help is that I too have Polish in my family on may mothers side so that my equalize other factors.

Seriously though I will try to get with this guy before the years end.

Guys   ???

I see the better solution. Simply I will sling some deep dimpled (they should come flying) glandes from Poland to the prearranged place in SC. At agreed time David will be waiting with the radar gun and with the tin hat on his head.

Jurek

Jeff, it works. I forgot to mention before, that all glandes hit the aim after a big lag. So they must surround the earth (maybe several times). I know it seems to be incredible, but it is quite simple, just the inward (spiritual) forces keep the proper trajectories and shape of molten glandes. Low temperatures in Poland help too, very cold air inside the deep dimples makes the pretty protective layer. So a tungsten is not necessary.

Jurek 8)

I agree, a sling will become the most important source of mechanical power in the not far future. It will terminate all present energetistic problems on the earth. Alredy it is used even for acceleration space ships in the outer space, the well-known fact. I suppose that air crafts will be similar to dirigible, but wil be made of lead and dimpled. Sure, sling is the key to find the perpetum mobile.

So, slingers will very desirable in future.

PS. Chris, sorry for the whiz. I will try to sling higher.