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Message started by xerces on Jul 11th, 2004 at 12:25am

Title: New Pictures--Range Boost
Post by xerces on Jul 11th, 2004 at 12:25am
In a previous post of mine, I wrote about a modification to lead sling projectiles that allowed for a low-pitched buzzing sound in flight.  This modification involved cutting notches vertical to the length axis of the projectile along the sides of a 4 oz lead fishing weight.

Someone mentioned that the notches may give the projectile additional lift.  I gave that statement a lot of thought and came up with something.    I purchased a bag of 4 oz lead weights that had a tiny hole drilled along it's length(to insert the fishing line).  I cut the 4 standard notches, 2 on either side of the football-shaped weight.  Only, instead of the notches being vertical, I made them diagonal to the length axis of the football.  

So basically each notch began on the outer edge around the middle of the football, and converged upon one tip of it.  Then I hand drilled a tiny hole  from the beginning of each notch to the shaft running along the center of the projectile.  I thought that as the projectile is on the ascent stage of it's parabolic trajectory, air would rush into the central shaft from the upper tip of the football.  When the air got to the middle of the football, some of it would pour into the four holes that I drilled and directly onto the notches that I carved on the surface of the football.  The air would rush against the notches and converge on the bottom tip of the football.  This would serve two purposes.  The first is that the diagonal notches would cause the football to spin faster and thus lower it's cep(circular error probability).  The second purpose is that the air rushing out of the bottom of the notches would exert force against the sides of the football, thus giving it abit of extra lift during the ascent stage.  I thought I had recognized my error after I made the projectile.  I thought that if the notches provided lift for the stone on the ascent state, surely the same notches would speed up the stone on the descent stage and thus negate any advantages of extra lift.  

But with a stone already made I decided to test it out for kicks.  So on friday, I took my medium sling and the stone with me on a fishing trip.  The lake that I fished in has a small island near it's center.  Using my laser range-finding binoculars, I ranged the distance from the shore where I fished to the island to be 310 meters.  Now normally, I would be able to cast a leadweight out to about 140-150 meters max.  Now this modified projectile, once leaving the pouch, flew way up, much higher than the unmodified weight.  There was no buzzing sound, but that was expected since the notches weren't designed to resist the air pushing against it.  The flight was extremely smooth(almost like a rifle bullet), I didn't see any wobble on the tips of the projectile.  Now that looked very odd, since it was as if the stone was flying through the air without any movement upon itself.  The projectile flew until it became a tiny dot in the sky and then it descended.  It appeared to me that the projectile struck the waters very close to the island.  Using my binoculars, I ranged the ripple pattern that the stone made.  The distance ranged was from 278 meters to 291 meters depending on where on the ripple the laser was hitting.  Taking the average of these two values yielded 284.5 meters, that's about double the range on a normal projectile.  That's longer than any stone that I've ever casted with any sling.

Now with this in mind, I'm making a few more of these projectiles.  My heavy sling was able to cast a normal lead-weight out to 195 meters.  If this works, then maybe these projectiles of mine will travel out to nearly 400 meters with that sling.  I'll post the results.

     

Title: Re: New projectile design....range boost
Post by TechStuf on Jul 11th, 2004 at 2:17am
The reflection of an infrared laser pulse from a water 'ripple' is certainly possible, although unlikely.  I too have managed it on occasion, albeit at shorter distances than the numbers you give.  Assuming your account is factual,  you would have to have been stationed considerably higher than the surface of the water to have received a reading as the angle of incidence is much too low otherwise.  At the range you indicate,  your position to obtain an accurate reading would have to have been 130ft. ABOVE the surface of the lake at a bare minimum.  And this, of course, assumes the water was quite placid at the time!  Not that I completely doubt your entire account.....but I would also add that 4 ounce fishing weights make for very.....very small ripples.  Especially small to be trained in on by a laser range finder in time....and at the proper angle, mind you, to be of ANY value whatsoever.   Your account is not without some anecdotal value, however.    I found it very creative and indicative of a keen and inspiring intellect.   Have you entertained the notion of submitting a short story to any publishers of the Sci-Fi genre?  

Title: Re: New projectile design....range boost
Post by xerces on Jul 11th, 2004 at 2:34am
Well, I was spotting from a short slope above the water.  But I was only about 2 meters above water level at the most.  This was done in the late afternoon and the lake's surface was very placid.  That ripple started small, but by the time I ranged it, it was quite noticeable.  If you don't believe me, buy a fishweight and try it yourself.

Title: Re: New projectile design....range boost
Post by TechStuf on Jul 11th, 2004 at 2:41am
It is of no consequence.  I do agree with you in part. Ripples (of varying kind) do seem to get bigger as time goes by.   ;)

Title: Re: New projectile design....range boost
Post by Mithras on Jul 11th, 2004 at 6:39am

wrote on Jul 11th, 2004 at 2:17am:
Your account is not without some anecdotal value, however.    I found it very creative and indicative of a keen and inspiring intellect.   Have you entertained the notion of submitting a short story to any publishers of the Sci-Fi genre?  


I don't like your patronising tone.

Title: Re: New projectile design....range boost
Post by Dan_Bollinger on Jul 11th, 2004 at 8:14am
Interesting and worth continued investigation, I think.  Post some photos when you can. Dan

Title: Re: New projectile design....range boost
Post by mgreenfield on Jul 11th, 2004 at 9:03am

Quote:
I don't like your patronising tone.


That's just part of TechStuff's special "charm".   We all have our own form of special charm.   Ask our wives.  mgreenfield  (Who's old enough to have seen a lot of special charm)

Title: Re: New projectile design....range boost
Post by David_T on Jul 11th, 2004 at 2:48pm
Blessed are the peacemakers...---Mgreenfield, you have a way with words and smoothing out rough spots  ;D

The forum needs all sorts to keep things straight and on the level.

I would love to try some of your lead bullets! Can you send a digital picture of one that we can post?

Send the picture to the email address on the home page and I will post it or make it ready for you to post.

David

Title: Re: New projectile design....range boost
Post by xerces on Jul 11th, 2004 at 9:20pm
I've sent the pics.

Title: Re: New projectile design....range boost
Post by TechStuf on Jul 11th, 2004 at 9:24pm
Good point, Dave.   Would that one day I obtain the patience to join their ranks on a full time basis.  :-/

Title: Re: New projectile design....range boost
Post by Hobb on Jul 12th, 2004 at 10:52am

Quote:
We all have our own form of special charm.   Ask our wives.


"Special Charm," huh?  That's not what my wife calls it... ;) :)

Title: Re: New Pictures--Range Boost
Post by David_T on Jul 14th, 2004 at 6:22pm
Check out the pictures of the modified lead projectiles. I added them to the end of the first post.

Title: Re: New Pictures--Range Boost
Post by TechStuf on Jul 15th, 2004 at 12:16am
lol....mine either Hobb......mine either.  :-/

Title: Re: New Pictures--Range Boost
Post by Douglas on Jul 15th, 2004 at 12:46pm
I'll bet you've seen this:
Why Do Golf Balls Have Dimples?

Because the dimples maximize the distance golf balls travel. Dimpled balls travel up to four times farther than smooth-surfaced golf balls.

Title: Re: New Pictures--Range Boost
Post by nwmanitou on Jul 15th, 2004 at 12:52pm
ya know what I'd like to see? how about someone make a glandes with the same dimple pattern as a golfball?

Title: Re: New Pictures--Range Boost
Post by Matthias on Jul 15th, 2004 at 1:06pm
I found this through the links when I was first reading this site, and was surprised that I couldn't find any discussion here...


Image linked from golfcross.com, copyright 2001 Conclusion Trust.
http://www.golfcross.com/frames/ball.html

Balls are pretty expensive, but combined with a silicone mold, you could make some pretty sweet "magnum" lead.

Matthias

Title: Re: New Pictures--Range Boost
Post by Gun on Jul 15th, 2004 at 1:22pm
has anyone slung these balls yet? I had an idea about golf ball ammo. What if you dilled into the golf ball and hollowed it out. Then filled it with lead or some other metal. You would have a prefectly cermetical ammo with the weight that you need.

Title: Re: New Pictures--Range Boost
Post by justin Ball on Jul 15th, 2004 at 2:11pm
Ever been hit by a regular golf ball, or seen what one does to a car roof or windshield? Do you need to add lead?
Justin

Title: Re: New Pictures--Range Boost
Post by Hobb on Jul 15th, 2004 at 4:30pm
Lead would help -- not so much to increase the damage done as to get a better cast.  Assuming you can sling at the same speed, a heavier missile will go farther.  Golfing is different, since the golf-club's swing (at the same speed as with a lighter ball) would lose more energy to inertia when it hit the ball.  I'm sure there are physics types here who can explain it better than I can.

Title: Re: New Pictures--Range Boost
Post by mgreenfield on Jul 15th, 2004 at 5:27pm
Golf ball dimples work because a well-hit ball has fast backspin on it.  With dimples "gripping" the air, backspin creates high pressure under the ball, and low pressure above the ball, so it actually flys like an airplane.

Of course anything BUT pure backspin produces hooks, slices, and other bad results.

nwmanitou says he puts backspin on his overhand shots, so could benefit from dimples on his glandes.  I put rifle-spin on my shots, so couldnt.

Golf balls at just over 1.5oz are a little light even for me.  

mgreenfield

Title: Re: New Pictures--Range Boost
Post by Matthias on Jul 15th, 2004 at 5:44pm
Not just spin. Inducing a turbulent boundary layer can do some neat things when it comes to form drag. One of the reasons why "turbulators" are/were illegal in sailboat racing. They show up all over the place, once you get to looking.

This article is decent, and has nice pictures.

http://www.golfjoy.com/golf_physics/dynamics.asp

Even a rifle spin throw (we should all be so lucky) could benefit from dimples (or even better, come to think of it, a simple ridge/ring type turbulator - golf balls don't have a preferred orientation so you have to "waste" dimples... good idea mgreenfield!)

Time to make new glands? Who is going to try this?

Matthias




Title: Re: New Pictures--Range Boost
Post by David_T on Jul 15th, 2004 at 6:19pm
Hey All,

A while back we had a long thread on dimple...in regard to Yurek and his atempt for a distance record.

I'm no physics guru but I remember Yurek and some others thinking that the dimple effect on leed glandes would be negated by the weight. They felt that the dimples were only beneficial for light weight projectiles like golf balls. It nay be worth a try anyways.

Title: Re: New Pictures--Range Boost
Post by Gun on Jul 15th, 2004 at 6:44pm
What is in a golf ball? I plan to make a golf ball filled with lead soon. Are they hollow or is there a little rubber ball in them ( this is what i think). Any information would be helpful.

Title: Re: New Pictures--Range Boost
Post by ZaQ on Jul 15th, 2004 at 7:04pm
No Gun, they're not hollow inside.  I'm not sure what the center is but it's kinda hard.  I've seen people carve faces and things like that into a golf ball, so I'm sure you could hollow it out.  Might take a bit of work but I'm sure you could do it.

Title: Re: New Pictures--Range Boost
Post by mgreenfield on Jul 15th, 2004 at 7:17pm
Great website on golfball flight dynamics posted by Matthias as reply #20!  

Maybe I get some of those elliptical golf balls, use them as mold patterns, then find a material that will net out at about 2.5oz instead of the golfball 1.56oz.   Between the dimples and a point-first pitch, I bet they'd fly a mile.

Yurek, how abt your 120-gram lead glandes with dimples?

mgreenfield

Title: Re: New Pictures--Range Boost
Post by Shaun09 on Jul 15th, 2004 at 7:23pm

wrote on Jul 15th, 2004 at 6:44pm:
What is in a golf ball? I plan to make a golf ball filled with lead soon. Are they hollow or is there a little rubber ball in them ( this is what i think). Any information would be helpful.


All the ballsi've opened (drilled a couple of them to make a bola) had green rubber string type stuff over an inside layer of rubber, but those were really cheap balls. I have heard of newer ones with gas cores though.

Title: Re: New Pictures--Range Boost
Post by longwinger on Jul 15th, 2004 at 7:28pm
Golf ball dimples work because a well-hit ball has fast backspin on it.  With dimples "gripping" the air, backspin creates high pressure under the ball, and low pressure above the ball, so it actually flys like an airplane.

Of course anything BUT pure backspin produces hooks, slices, and other bad results.

Hi MGreenfield,
I thought that a well hit golf ball did not spin, and the dimples on it helped form a boundry layer of air around it, giving it a more streamlined shape than just a round  smooth ball, a spinning ball will have more lift on one side, doesn't matter which, and not fly as true a line as one without spin and may not develope and benefit from a well formed boundry layer, as a non spinning ball.
So it seems to me the dimiples on a golf ball do not benefit the sling projectiles. Apparently the best approach to added distance would be the football shaped glandes, spinning on their axis and it that same direction. Although the ones you speak of with backspin may develope lift, makes sense.
But, I may be way off base here too!

Title: Re: New Pictures--Range Boost
Post by Matthias on Jul 15th, 2004 at 7:51pm
Lead will certainly decrease the effect of boundary layer manipulation, but won't negate the benefits entirely.

Ok, pulled out the trusty spreadsheet and the thinking cap (no guarantee that I don't have it on inside-out, but you get what you pay for) No spin-lift (Magnus effect) included. These calculations are for spheres - an elliptical shape will show less effect still.

Using a 40 degree launch angle and 60m/s throw I get:

Max range (size / density irrelevant) ~367m

Smooth golf ball = 117m
Dimpled = 168m

so dimpling adds 45%, and air resistance knocks more than half off the total range.

Lead "golf ball" size smooth sphere = 296m
Lead dimpled sphere = 327m

In this case, dimpling only adds 10% and we are close to max range

A half diameter lead sphere gets 254m and 296m respectively

A double size lead sphere (if you could throw it) would take you to 350m and 356m

It should be noted that the scale of surface deformity needed to trip the boundary layer is pretty small, and a cast glans is probably half way there already. I still vote for a raised lip at the shoulder of the leading edge. That 5-10% could be pretty useful for something that doesn't cost anything.

Matthias

(Oh and new golf balls are pretty much all solid resin core - the "titanium" that people pay extra for is in the form of the worlds most common white pigment... drives me nuts...)

Title: Re: New Pictures--Range Boost
Post by longwinger on Jul 16th, 2004 at 4:27am
I did a little research, and looks like a well hit golf ball does have alot of back spin to it, open mouth, insert foot.

Title: Re: New Pictures--Range Boost
Post by mgreenfield on Jul 16th, 2004 at 8:37am
Matthias, ....as a given smooth-surfaced mass moves from spherical shape to eliptical, air drag is reduced.   This is good!

If that mass gets too elongated, it will be tough to handle in the sling pocket.    This is bad!

So, as you move the mass shape from spherical (with diameter/length ratio = 1.0), to eliptical with diameter/length ratio = 0.5, and further, where do diminishing returns in reduced drag start to show up??

Anything in your magic spread sheet let you tell us about this?    It would be very interesting to me who pitches eliptical glandes point first.

mgreenfield

Title: Re: New Pictures--Range Boost
Post by Matthias on Jul 16th, 2004 at 10:35am
Here is a nice "dimpling calculator" it only works for spheres, and only gives forces. The drag coefficients calculated by this one give very slightly less of an edge to the dimpled shape than what I used above (and the previoudly linked article claims) - not enough to make a very big difference.

http://www.mame.syr.edu/simfluid/redder/dragforce/DragForce.html

You can answer the length/diameter question (like most questions actually) without using any math/engineering. Historical glandes are shaped that way for a reason, as are bird bodies and (american) footballs. All with different constraints, of course. If you take pure aerodynamic drag with a ton of assumptions, the trade off between form drag (what we're talking about) and skin friction, usually occurs somewhere around 30%


Figures borrowed form Dalhousie Univeristy, and I'll be willing to bet theat they "borrowed" them from White, the standard first year fluids text...

Turbulent flow (induced or otherwise) will flatten the curve, so that anywhere from 2:1 to about 4:1 should be just fine. By the time you take into acount the effects of a possible "off-axis" (even by a small amount) throw, 2:1ish is looking pretty attractive...



One thing to keep in mind with these graphs is that we are only looking at cd for a shape with no scaling. An ellipse of same mass as a sphere will have a smaller projected area, so total drag for matching projectiles will be as much as 50% lower again (1/4 sphere drag! why was it that we like these things so much :D) The other nice thing is that as cd goes down, the advantage you get from lead is reduced as well, which gives some of us other guys a fighting chance!

Matthias

Title: Re: New Pictures--Range Boost
Post by Hondero on Jul 16th, 2004 at 11:33am
Matthias, very interesting your ballistics information. We have discussed before the subjet and didnīt find a proper way to calculate the ballistics of the sling. I think you are the right person to make such a calculator, that moreover is essential to have online in a site like this. Questions like the max. range with a stone or lead projectile, the optimal weight of a projectil, or the start speed for the distance world record (let us say 500 meters), will find a proper answer :D

Which parameters uses your spreadsheet?

Title: Re: New Pictures--Range Boost
Post by Yurek on Jul 16th, 2004 at 12:34pm
I see that the question has been revived again!

Here is the other nice toy, the Golf ball Trajectory Simulator:

http://www.ecs.syr.edu/centers/simfluid/green/traject.html

Matthias could compare his result with that one. Pitty it doesn't allow to change the density and ratio as parameters :(

Mgreenfield,


Quote:
Yurek, how abt your 120-gram lead glandes with dimples?


I rolled the glande model of heat-hardened modelling paste for children, and next imprinted the dimples with the rounded ending of one of my ball pens :) That one seemed to have the suitable shape and size.

Here is the reposted picture, alas that one is from the flat scaner and its quality is poor.



Jurek

Title: Re: New Pictures--Range Boost
Post by Yurek on Jul 16th, 2004 at 5:40pm
Ooops! I didn't read Mgreenfield's inquiry correctly before. I thought he asked how I made the dimpled glandes.

Well, I tried the dimpled ones only one time among the smooth ones, which you can see on the above picture. There was too little tries in order to get the clear conclusion. For me they flied similar to the smooth ones. Some of them reached pretty good ranges, indeed, but the best range I got with a glande without dimples. There are a lot factors, I'm not able to get the 100% constancy in each range throw. The launch angle, orientation of glandes durring a fly, my timing and energy put into throws are a bit different evry time, I do it nearly the limit of my possibilities after all. Durring that try I got about the 100-120 m diference between the best and the worst range. I couldn't see any regularity regarding to the dimpled glandes, which would prove the adventage of them.

Now I use the smooth ones because making them is easier, it is only reason. Probably the dimples can help a bit, but the adventage is difficult to percceiving. Curently for me the proper technique is a more important factor.

Jurek


Title: Re: New Pictures--Range Boost
Post by Matthias on Jul 16th, 2004 at 6:52pm
Yup, I guess we are going to have to keep dredging up old threads until we come up with a definive answer. I'll put some more effort in this weekend. You can tell that this week has been mind-numbing because my post freq has gone waay up... I've been doing sling calcs at work to spite my boss, who won't give me any time off... that guy is a loser (the joys of being self-employed)

I'd suggest that Yurek's dimples are much too large for the size of the glandes, to the point where they would start to harm performance. If you can achieve consistent point-forward flight, the ideal could be a single raised sharp edged ridge (or dashed ring) about 25-30% back from the forward edge.

If people want to play around with experimental glans design, I might suggest building large scale, light projectiles. A tennis ball sized series of wood projectiles would give pretty solid feedback (differences in drag are emphasised) and be easier to test and retrieve. Any advantages that turn up would be applicable with smaller/denser ammo...

Matthias

Title: Re: New Pictures--Range Boost
Post by Sean on Jul 16th, 2004 at 11:52pm
oh my god you people are smart... or maybe im just really tired im not sure... but anyways i think that golf balls arent solid but are the shell then normally some string and a rubber ball... or was that a baseball... i cant remember right now need sleep be back with you later
Sean

Title: Re: New Pictures--Range Boost
Post by mgreenfield on Jul 17th, 2004 at 7:53am
Matthias, .....this discussion of aerodynamics has gotta end up in the articles section, I say.    It's dynamite good info.     mgreenfield

Title: Re: New Pictures--Range Boost
Post by ZaQ on Jul 17th, 2004 at 5:25pm
Guys, I think the only way to solve this golf ball mystery is just for one of us to hack one up and find out.  I think I have one around hear somewhere so I'll be on the lookout for it.

Title: Re: New Pictures--Range Boost
Post by Matthias on Jul 17th, 2004 at 7:03pm
I've cut up dozens of golf balls... They used to be (10-15 years ago) consistently rubber band wound around around (usually) a grape sized black rubber ball, which was often liquid filled. Lately, every ball I've cut up is a solid resin core with a hard/tough white cover. Some "range balls" are one piece.

A quick survey of an online golf ball shop (golfball.ch) reveals the following selection:

2 wound balls
36 2-piece (white cover around a solid core)
20 3-piece balls (two piece with an extra thin layer under the cover) **cough**-gimmick!-**cough**
6 4-piece balls **cough**-expensive gimmick!-**cough**

Matthias

Title: Re: New Pictures--Range Boost
Post by Zorrro on Jul 24th, 2004 at 5:59am
i've opened a few golf balls too  we used the rubber filament to tie it on the top of a pencil or ballpen and  tie a  lead pellet (one of those biconical "diabolo") on the end of the rubber .
then hold the pencil with one hand and  the pellet  with the thumb and index fingers of the other hand...
stretch.... aim...  and let go... Short range (1 to 1.5 yards) but deadly for flies, grasshoppers, roaches and some other "wild life" and nice for bothering other kids at class  as well
(Should i post this in the "other primative weapons" section? ;D )
Golf balls were  a rare item in Spain those days, (a minority snob/rich people sport)and i used to get mines at the Torrejon  USAF  base golf course.
Yes... i did a lot of bussiness selling metres of rubber to other kids ;D

Title: Re: New Pictures--Range Boost
Post by Zorrro on Jul 24th, 2004 at 6:02am
Jurek
that golf projectile at the left side looks pretty cool   :)
Great job!

Title: Re: New Pictures--Range Boost
Post by english on Jul 24th, 2004 at 7:44am
This is one of those threads, like the staff sling question, which we will keep going over, when someone new comes along with a neat new idea.  I thought we came up with the idea that dimples would be detrimental for glandes, unlike for golfballs.  I think it was something like, golf clubs do not create their own backspin on the ball, because you are basically just whacking it, whereas a sling creates the backspin anyway, so dimples are not required to grip the air.  Or something.  Maybe I'm wrong.

Quote:
Would that one day I obtain the patience to join their ranks on a full time basis.  
Or even part-time.

Title: Re: New Pictures--Range Boost
Post by Yurek on Jul 26th, 2004 at 11:59am
Thanks Zorrro!

English, I'm not a golf player but I think that just clubs create  the backspin. The dimples only streighten the Mangus' effect and reduce the air drag of golf balls.

Jurek

Title: Re: New Pictures--Range Boost
Post by David_T on Jul 26th, 2004 at 12:45pm
Yes, the club strike creates backspin unless you are a lousy golfer like me ;D Then it creates topspin, or side spin... :o  Four!!! That is golf talk for: LOOK OUT or DUCK!

Title: Re: New Pictures--Range Boost
Post by Chris on Jul 31st, 2004 at 6:59am
As several people have explained, the dimples do increase range in a few ways, including reducing drag.  This is also why tennis balls are furry.  

Although the density of a lead projectile is far greater than a golf ball, I think dimples would still be beneficial.  One of the things to remember is that sling projectiles have long flight times, perhaps similar to golf balls at their slower speeds, or even greater.  If you could reduce drag by a fraction for a 6 second flight, that could extend your range by a noticeable amount.  

Yurek, how long are your projectiles in flight?

Chris

Title: Re: New Pictures--Range Boost
Post by Yurek on Jul 31st, 2004 at 5:57pm

Quote:
Yurek, how long are your projectiles in flight?


Chris,

Welcome you back!

I didn't make exact time measurments. But today, during slinging into the lake with my long thin sling I was calculating the times of flying of stones. They were a bit different: from 6 to 8 (seems even 9 seconds). These times were mainly dependent on angles of throws (how high were trajectories). Of course, quality of the used stones and each throw, were significant factors too. So, the longer time of fly, not always means the grater range.

My problem with glandes is that I usually have a limited amount of them, so I concentrate on making good throws and don't  measure the times. During one of my first tries I counted one throw at ca. 10 s. Next time I will ask somebody for measuring with a stopwatch and let you know more exact results.

Jurek


Title: Re: New Pictures--Range Boost
Post by Chris on Aug 3rd, 2004 at 7:20pm
If you could cut the drag in half for a ten second flight, you are looking at perhaps dozens of gained meters in range.  Any physics buffs care to give us an explanation?  I'm no expert by far.  

Chris

Title: Re: New Pictures--Range Boost
Post by Matthias on Aug 3rd, 2004 at 8:43pm
I really need to clean up that spreadsheet and migrate it to a nice sling-specific web-app. How is your Java Chris?

Not having access to it at the moment, I'd hazard that Jurek is probably slinging to around 90% of max (no drag) range already. If it was possible to reduce the drag (shape, surface trickery or higher density ammo) even further, say by half, it stands to reason that he could pick up an extra 25m or so. Slinging lead is obviously the easiest way to pick up distance, as it does tend to minimise the aerodynamic effects...

It would be very valuable validation if we could try to compile some caparative range data. We need common projectiles across a range of shape/density efficiencies. Golf balls and tennis balls are good candidates for "standards". I was thinking about maybe water filled tennis balls as well. What is important is not so much how far a given contributor can throw these, but how what the range difference is. Anyone have any ideas for a "standard" set of sling ammo that is consistent among different locations? If we stick to spheres for now, it will keep things manageable. There is going to be some pretty big spread due to different people hitting different limits with different style/physiologies, but the more data the better...
  • Golf ball
  • Tennis ball
  • "orange" street hockey (nice and smooth)
  • Baseball
  • Squash ball
  • Baseball
  • A bucket of snooker balls would be ideal... lol


If anyone has ammo that is fully describeable we should add those off the top of my head I can think of concrete tennis balls and really pretty 1" lead spheres (hint hint)

Matthias

Title: Re: New Pictures--Range Boost
Post by David_T on Aug 3rd, 2004 at 10:18pm
We need to have a few people experiment with pouch design related to the orientation of the gland at release.

I am thinking that purhaps a tilted or angled pouch would put the gland in the optimal point fist position at the snap of release--I don't know but I would think that that would make a very big difference. If the gland is having to orient itself in the first few seconds of flight, it is wasting much energy as compared to a perfect orientation at launch---just a thought??

What do you think?

Title: Re: New Pictures--Range Boost
Post by Matthias on Aug 3rd, 2004 at 11:40pm
For sure glans orientation and throw mechanics are going to have a big impact with non-spherical ammo. As you noted in the other thread, just the spin orientation has a big effect on lighter projectiles due to the lift generated. A badly slung golfball is pretty depressing to watch as it dives into the sand rather than soaring out over the beach!

I would be quite surprised if an ovoid that leaves the sling with anything other than perfect orientation and spin will change significantly during the throw. If a spun-on-axis glans takes off pointing 40 degrees nose up (direction of throw) it is almost certain to land in the same attitude. Luckily, the benefits of lowered drag are most significant during the initial half of the flight anyway, so it doens't matter _too_ much that it ends up crosswise. This will be another argument for lower than "perfect" aspect ratios. My sim should be able to be modified to allow for changing attitude throughout the flight... if we can get it refined to the point that the difference made is outside the error I'll add it.

I used to have access to a 500 frames per second camera... what a blast it would have been to be playing with these ideas then!

Matthias

Title: Re: New Pictures--Range Boost
Post by Hondero on Aug 4th, 2004 at 2:23am

wrote on Aug 3rd, 2004 at 10:18pm:
I am thinking that purhaps a tilted or angled pouch would put the gland in the optimal point fist position at the snap of release--I don't know but I would think that that would make a very big difference.
What do you think?


Yes, David, I had the same idea, a special pouch design for glandes, maybe with a lateral hole or little loop that put jus a bit of retention at the release on and end of the glans, or an inclined and splited pouch than can throw the glans point-first but that prevent its release when spinning.
Iīd like to have the time to experiment throwing  against a wall and see the impacts on the glandes.

Title: Re: New Pictures--Range Boost
Post by David_T on Aug 4th, 2004 at 5:12am
Ahh yes, to have the time to pursue such things!

A loop ;D That is an idea. An angled loop on the trailing end that would still allow spin as it rolls out of the pouch.

Yes, and still stay in the pouch at all points during the spin.

Title: Re: New Pictures--Range Boost
Post by mgreenfield on Aug 4th, 2004 at 9:37am
Friends, friends, friends!   I launch elliptical glandes point-first all day long with a plain "standard" sling, ...no special pockets, etc.   Many of these (not quite all) have no wobble.  The secrets are just 2:

1/  Use a "wide grip".  I put the retained cord on my ring finger to keep it far away from the release cord.  I let the retained cord hang free outside my fist.

2/ Be sure your palm is pointed forward at the moment of release, ....and I suppose as long before that moment as you can manage.   If you use a underhand delivery this makes it feel a little like bowling.

Glandes launched point first, and in stable flight, look like little high speed rockets.   They're very pretty to watch, ....and it's easy to do.

mgreenfield

Title: Re: New Pictures--Range Boost
Post by TechStuf on Aug 4th, 2004 at 10:03am
Yes!  The centrifugal force acting on the widened grip imparts more corrective torque on the cords assuring a correct orientation at release.  This must've been how the Romans learned it!  I have had midlevel results with obloid ammo using my normal grip, with both cords eminating from between thumb and forefinger and have used a bit of fletching attatched to the bottom of the pocket via thin carbon rod to effect the same results.  This allows me to keep my the style with which I have become most accustomed, with negligible loss in speed while getting rock solid perfect spiral releases every time.  

For those who wish to try it:

http://www.nyblimp.com/superior/carbon-rods.htm

has reasonable pricing.

Title: Re: New Pictures--Range Boost
Post by THOMAS on Aug 4th, 2004 at 12:54pm
For more range with heavier ammo try a bead or ball on the end of the release cord.  
I don’t have very strong hands so I use a 1” dia. wood ball drilled through and counter sunk for the knot.  These can be found at most craft stores.  

This increased my 5 oz. hardball range by at least 30%.
The release cord and its end ball have never interfered with the shot.

THOMAS

Title: Re: New Pictures--Range Boost
Post by Hondero on Aug 4th, 2004 at 6:28pm

wrote on Aug 4th, 2004 at 9:37am:
Friends, friends, friends!   I launch elliptical glandes point-first all day long with a plain "standard" sling, ...no special pockets, etc.   Many of these (not quite all) have no wobble.  The secrets are just 2:

1/  Use a "wide grip".  I put the retained cord on my ring finger to keep it far away from the release cord.  I let the retained cord hang free outside my fist.

2/ Be sure your palm is pointed forward at the moment of release, ....and I suppose as long before that moment as you can manage.   If you use a underhand delivery this makes it feel a little like bowling.

mgreenfield



Yes, yes, mgreenfield, you are right in the two points  :) With sidearm throw, and almost any inclination, you can also get the point first flight, but with all these styles the little problem is that you have to release just when the hand is at the level of the body and not more advanced, so that the palm point forward, and so you lose the last part of the snap, not developing the maximum momentum. But if one donīt look for max. range but penetration, the style is right.
You are the number one vertical thrower  :D

Title: Re: New Pictures--Range Boost
Post by David_T on Aug 4th, 2004 at 8:36pm
Oh yes Mike I agree that spirals are had with the regular pouch. I was just curious as to the "absolute opimum orientation" for record slings. I would love to see a high speed camera capture the sling motion to show the exact angle of the gland at release.

From this film, one could either change the rotation angle of the spin or the shape of the pouch to make it fit with the most powerful arm movement of the individual doing the slinging.

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