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Air Drag On Sling Cords & Pocket (Read 23929 times)
mgreenfield
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Air Drag On Sling Cords & Pocket
Dec 28th, 2003 at 4:52pm
 
Fellow slingsters, has anybody done research on this?   Leather bootlaces are about 1/8"square.   Two of these 32" long will present about 8 square inches of flat frontal area to the airstream generated on sling spin-up.   Add frontal area of the pocket and projectile to this, and we may be looking at a huge impediment to launch speed of the projectile when "fat" cords and a large sling pocket is used.

Roman glandes were football shaped, which meant smaller pockets were needed per ounce of projectile weight.    I'll bet if we could find a well preserved Roman army sling, we'd be surprised by the tiny pocket, plus very long and very skinny cords used.

Modern "fat-corded" slings may be crude rock-lobbers by comparison.

Any ideas??             mgreenfield
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JeffH
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Re: Air Drag On Sling Cords & Pocket
Reply #1 - Dec 28th, 2003 at 9:54pm
 
I have been thinking about this some myself, of late.

Obviously, this smaller the cord and pouch, the faster we can sling.  What is the limit, though?  Is the size of pouch limited in smallness by the type of projectile?  Can we get by with a small pouch for general slinging where we can't know the size of stone until we pick it up?  Can we get a very thin cord to NOT tangle up after the throw or when being carried?

Who knows?

jeff <>< who is curious
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So David triumphed over the Philistine with a sling and a stone. (1 Samuel 17:50)
 
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mgreenfield
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Re: Air Drag On Sling Cords & Pocket
Reply #2 - Dec 29th, 2003 at 3:05pm
 
I went from 1/8"square leather bootlace cords to braided dacron fishline about 1/32"round.  The thin bare fishline was hard on the fingers, so I put a 4.5" bootlace "handpiece" on the end of each cord.   Length from center of pocket to toggle was 38" on both versions.    Pocket size is 6" x 1.5", but with small slits in the leather to let it hold the ammo well in spite of being pretty narrow.

Standard golfball ammo was used with the bootlace version AND the fishline version.   Results were these:

1/ Swinging a golfball (which is pretty light ammo at just 1.5oz) had a lot better feel in the fishline version.   It didnt feel like I had to drag the sling around to make it spin, ....which was the feel I had swinging a golfball in the bootlace version.

2/ The fishline version is absolutely silent.  NO cord whistle. 

3/ Just "letting fly", I'd say the fishline version had maybe 1/4 to 1/3 again more range.

4/ String tangling was not a particular problem in use.  However, I definitely will wind the sling on a spool for storage.

FYI, the dacron is pretty slippery, so I painted all knots with clear fingernail polish to keep them from slipping. 

Any other experiences/experiments to report on???

mgreenfield
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Re: Air Drag On Sling Cords & Pocket
Reply #3 - Dec 29th, 2003 at 7:04pm
 
HEEEE HAAAAAAAA!  I've been hoping someone would try this sort of thing out.  My idea was using very thin steel cable with a larger section of larger material at the end for comfort on the fingers.  The smallest pouch would probably be split.  With these sort of sling upgrades, someone on here, probably Jurek, could beat the world record on distance.  I believe it.  1/4 to 1/3 extension in range is a big extension!  Whipmaking has taught me how important air friction is.  A lead gland in a sling like that, will go forever!   

                      Ben
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JeffH
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Re: Air Drag On Sling Cords & Pocket
Reply #4 - Dec 29th, 2003 at 8:03pm
 
Ben,

How about plating 3 or 4 strands of spider wire, the kevlar fishing line, into the cords?  It would still be very small in diameter, but rather strong.  Attach these to a small pouch and viola, maybe this is it.

What do you think?

jeff <><
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So David triumphed over the Philistine with a sling and a stone. (1 Samuel 17:50)
 
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Yurek
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Re: Air Drag On Sling Cords & Pocket
Reply #5 - Dec 29th, 2003 at 11:42pm
 
The mgreenfield's tests absolutely prove Ben's idea about the considerable effect of reduce a sling drag. For my first tests with the glandes I have made (just inspired by Ben's and Hondero's posts) the more slender sling. It is rather the temporary design described here:

http://www.slinging.org/forum2/yabb/YaBB.cgi?board=1;action=display;num=10607402...

Durring the first throw of the glande I had a false feeling that this sling didn't give a pretty enough power, it was too quiet. No snap and only the gentle swish of the cords. I also tried this sling wih stones and I found they go markedly further than ones throwed by my previous slings designed for various stones.

The 3.5 mm diameter of the used cords seems to be similar to mgreenfield's bootlaces. I wonder what a distance improvment I will get if I maximally reduce my sling. The 1/4 or 1/3 improvment would be fantastic! I have fired about 4 kg of lead until now. All these shots was observed by hidden persons, and now I'm sure that I can exceed 500m distance constantly.

I know such numbers could cause scepticism or even distrust of some people, although I have decided to publish them here because just you guys caused the rebirth of my slingin passion and gave me a lot useful information.

Jurek



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In the shape, structure and position of each stone, there is recorded a small piece of history. So, slinging them, we add a bit of our history to them.
 
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JeffH
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Re: Air Drag On Sling Cords & Pocket
Reply #6 - Dec 30th, 2003 at 9:35am
 
Jurek,

It is not the distance you are slinging that makes us suspicious.  We americans just have a natural dislike of "hidden persons".  Make him come out where we can see what he is doing and we will be more comfortable.

As for people doing big things... Well, americans are used to stories of big things.  Our history is full of them.  We might make you an honorary citizen if you pull off the record.  And if we can't make you an american citizen, I sure Texas will take you regardless.  Texans just love bigger than life stuff like slinging 1,600 ft.

jeff <>< who hopes you make it
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So David triumphed over the Philistine with a sling and a stone. (1 Samuel 17:50)
 
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mgreenfield
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Re: Air Drag On Sling Cords & Pocket
Reply #7 - Dec 30th, 2003 at 10:39am
 
Cord material I used is a single strand of 40lb test braided dacron icefishing line.   It's very limp & flexible.   The earlier-used leather bootlaces were also pretty flexible.   How does a sling perform when you use stiffer materials for cords?   Seems like it could be a problem.

Slinging for distance would probably put the slingster:

1/ On the edge of a raised platform....

2/ Spinning a very long sling, .....each cord 6-7ft or more.

3/ Each cord of fine stainless wire maybe.   Here's where the concern with cord stiffness comes in.

4/ Loaded with a football shaped lead glande, experimentally weighted to maximize the interaction between weight, sling and slingster....

5/ In a smooth pocket just barely large enough to control the glande.

Anybody going to give it a try???

mgreenfield
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Yurek
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Re: Air Drag On Sling Cords & Pocket
Reply #8 - Dec 30th, 2003 at 8:03pm
 
Jeff,

When I was writing "hidden persons" I meant the observers who was hidden behind the shelter close the expected landing zone of the glandes. I mentined in my previous posts that observers was my son or my wife. If you want I will send to you our family photo Smiley Consider that I'm not anonymous here. I corespond with guy from my country, who has found me just through this forum. Probably my poor English is guilty of your incomprehension. But I hope this forum is open for slinging fans from all world and everyone who want to share own experiences is welcomed. I like this place because it is the best forum about the slinging which I know. I'm slinger like you and the others here and I tried to bring in some share. The slinging passion is the only reason of my stay here, believe me. For me nationality of the others here is not so very important as it what they say and think.

Quote:
And if we can't make you an american citizen, I sure Texas will take you regardless.


Jeff, it would be very nice, so I have the additional motivation now Smiley


mgreenfield,

Quote:
3/ Each cord of fine stainless wire maybe.   Here's where the concern with cord stiffness comes in.


The thin stainless wire is the best due to an air drag but for me it has a big fault. It is dangerous for the slinger. In the summer I remember when I was slinging with the long-leather-cords sling the release cord whipped my left naked forearm, so it was a bit sore and red. I imagine how the long, sharp, heavy and quick cord could sting.

I don't know sure but I suppose that too stiff and heavy release cord could impede opening the pouch.

Jurek







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In the shape, structure and position of each stone, there is recorded a small piece of history. So, slinging them, we add a bit of our history to them.
 
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Whipartist
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Re: Air Drag On Sling Cords & Pocket
Reply #9 - Dec 30th, 2003 at 11:02pm
 
Jurek,

Wow, I've been reading your posts about your range achievements!  I knew you could do it!!  AWESOME!!  I'm so excited. 

Don't worry about what Jeff said, it was just American humor.  I think you are the next world record holder with the sling!  We're all excited and displaying our pleasure.  Heeeeeee Haaaaaaa!  Man, you're making 500!  You'll beat it easy when you fine tune things.   

As for making a highly aerodynamic sling.  I was thinking about it today.  I've never heard of spider wire, but the very thin, maybe 1/32"- about 1,5mm steel cable, is very strong and flexible.  Infact if it was too flexible the cords would tangle.  Which is what I fear could happen with fishing line.  I haven't experimented, but I think a well made sling with the steel cable wouldn't be dangerous and would work really well.

I've been reading about other topics too, but I'll reply here.  I don't think that slight dimples on the surface of the glandes will affect the distance that much, but when every inch counts, I'd make those things as smooth as possible.  Watch out for lead poisoning though.  That stuff isn't good for you. 

Consider, just consider, that the last world record was made with a 2.5oz "dart."  Does that mean that the guy put fins on it and a point?  To me that seems like it would be a bad idea, but if anyone wants to give it a try, it's an idea.  I believe just plain roundish glands will be best, but I don't want to discount anything.

Jurek, I'm interested in what your new sling for glands looks like.  If you have time, take some pictures and post them.  And the glands too!

So when you sling for distance, you always use a 47" sling?

I don't want you to just beat the world record.  Wouldn't it be awesome to demolish it?! 

The pouch or cradle aerodynamics is another big factor.  It is traveling the fastest of any part of the sling and thus is very important.  Any excess little area of leather or whatever, that isn't necessary, should be removed.

I'm sure there are lots of ways to fine tune it, but if we really want to get radical, we could maybe drop it altogether.  In otherwords, make it out of two pieces of steel cable that overlap.  (in appearance like the Balearic slings but much smaller) But how would this grip the glandes?  Cut grooves into the glandes at two places, like the stripes on a football.  The cable could catch on the two grooves.  Now that's getting efficient!  Obviously such glandes would be a little more time consuming to manufacture, but only a few would have to be made and it would be pretty simple to get a small round file and carve the grooves into such soft metal as lead.  This isn't regular slinging, this is the world record, and anything helps. 

Can you imagine what you could do with such a sling!  That's prime efficiency! Space age slinging!   

                                           Ben      
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JeffH
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Re: Air Drag On Sling Cords & Pocket
Reply #10 - Dec 31st, 2003 at 12:10am
 
Jurek,

Sorry that my humor was so obscure.  I fully understood your english, and who your observers are.  I was just pulling your leg a little, as we say.  I am feverishly nationalistic and rabidly American, but not the least bit concerned about the nationalities of my friends here at Slinging.org.  You are all great guys!!!!!!!!!!! 

Ben,

Check out your local Wal-Mart or fishing store for spider wire.  It is very thin, plaited kevlar (I think) fishing line.  50 lb test line is the same diameter as 12 lb monofilament, I believe. 

As for thin lines.  I believe we may have also overlooked something here that is very important.  Stretch in the cords.  This is probably as important as the size reduction below 1/8".  All my platited cords have some stretch and this is just an energy waster.  I believe the spider wire would be worth a try due to its low stretch.  Less stretch is probably due some of the credit for mgreenfield's better slinging.  Jurek is also using some low stretch cordage, I think.

On the subject of a record.  I believe that there should be some reasonable limits set for the attempt.

1)  Sling of max length equal to say 48".  This should be a sling that could reasonably be expected to be used for hunting, warfare, etc.  I don't think it would be good to allow a sling specially made for the record attempt.  This precident is found in other sports, I think.

2)  The attempt should be made on level ground from the ground, not a platform.  This extends the throw if only a little, but again makes for a condition prepared especially for the attempt.

3)  Limiting the projectile should be done carefully.  I don't like the "dart" concept as this is an unnatural "stone" shape or object.  The bi-conical glande, or any round object (rock, ceramic, golf ball) would be o.k.  For that matter, an apple or canteloupe would be o.k.  I will throw most anything I can get to stay in the pouch, but a "dart" just does not seem right.

jeff <><  who thinks Jurek o.k.
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So David triumphed over the Philistine with a sling and a stone. (1 Samuel 17:50)
 
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Yurek
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Re: Air Drag On Sling Cords & Pocket
Reply #11 - Dec 31st, 2003 at 2:43pm
 
Ben,

Great thanks! I like your post. I haven't time to write too much in this year. So I put quickly only a few pictures.

There are my new sling (which is far to the optimal one) and the patterns for last my mold. I have the CIS scaner which is not good for 3-D stuff, so the pictures of the patterns are poor quality and a bit deformed.

In the last tests I set up the sling at 50".

See you guys in the New Year. Happy New Year!

Jurek

...

...

...


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« Last Edit: May 7th, 2005 at 6:46pm by Yurek »  

In the shape, structure and position of each stone, there is recorded a small piece of history. So, slinging them, we add a bit of our history to them.
 
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Re: Air Drag On Sling Cords & Pocket
Reply #12 - Jan 1st, 2004 at 3:44am
 
Jurek,

Very nice design.  I thought it might look something like that.  I like the way you doubled the leather on the ends of the pouch.  That design looks efficient and very nice.

I made an ugly looking, 45" sling with 1/32" steel cable today, after work.  Didn't take long.  In the picture you can see the grooves I carved into the gland.  The cable fits in the grooves.  This thing is so fast! It's too fast for my arm.  I can't move my arm fast enough to keep up with it.  I can't experiment with range because I don't have the place, but I can experiment with power.  And it is powerful!! 

The cable tends to kink just a little bit if you don't treat it nice, but what I like about it, is it's stiff enough to not tangle.  And it's tuff enough to not wear out or break.  I bet there is higher quality cable that would do better.  The filaments would have to be more fine than these.

The drag on the sling is so small, it feels weird to use.  I wish I had a place to experiment with range! It's incredibly powerful.   

Speaking of elasticity, it has none.  I propose this type of sling to you as an idea for you to try out if you're interested.  I think it will improve your range further with lead glandes than a more traditional design. It's ugly, but it's as aerodynamic and efficient as can be.   

...

Happy New Year.

                                       Ben
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Re: Air Drag On Sling Cords & Pocket
Reply #13 - Jan 1st, 2004 at 9:03pm
 
Great idea, I'm interested in, of course! Only still cables, no pouch. It seems there is impossible to find out somethig much more aerodynamic regarding to a sling. I imagine how it will be whisking! I must give it a try. The grooves are no problem because of they could be made on the patterns (models for molds).

Ben, it would be good to use stainless steel wire 7x19. This kind of it is pretty and flexible. The smallest diameter which I know is 2 mm, maybe it is possible to find a thiner one, but 2 mm still seems ok. In your newest sling the endings are very nice, I think it is your plaiting.

On "dart", from the last record attempt, here is the quote from Lloyd's website (http://www.staff.ncl.ac.uk/nikolas.lloyd/weapons/sling2.html):

"Recently, another sling enthusiast on the net quoted the following: "World record 2.25oz lead weight 477 meters!! (US), 8oz stone, 375 yards (British)". This is more like the ranges quoted for ancient warriors. The American record for the lead bullet used a bullet of typical ancient weight, but the British stone record used a remarkably heavy stone which surprises me. I do not know any of the details regarding these records."

I suppose he speak about the same record which Ben mentioned, the distance is compatible but the weight is a bit different. If Lloyd had a reliable information, it looks like the lead glandes were used then.

Jurek
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In the shape, structure and position of each stone, there is recorded a small piece of history. So, slinging them, we add a bit of our history to them.
 
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Re: Air Drag On Sling Cords & Pocket
Reply #14 - Jan 2nd, 2004 at 4:53am
 
Jurek,

Hmmm.  Lots of thinking huh.  I got the distance record out of a Guiness book I found at our local California University.  I've seen the other record in an older Guiness book I used to own.  I'm not sure if I still have it.  If you want me to look, I'll look tomorrow.  My memory is a 7oz stone and around 375 yards.  372 comes to mind, but I could be just pulling rabbits out of hat.  I think Lloyd's records are the same ones we are talking about.  I don't know much about cable or wire, or spider wire, or any of it.  If anyone has any ideas, try them.  It works good, I can tell you that.  I had a bit of difficulty getting used to positioning the wires in the grooves, it would have been helpful if they were deeper.  But otherwise it worked great.  Very powerful! 

Infact, this sling is 45" but if you want me to send it to you Jurek, or make you a 50" sling, I will.  I'll send it to you for free, just give me your address.  I don't need it, I'm just experimenting because I'm excited about your record attempt!  Or you can make one yourself.  I'm happy to be a part of this in any way.  I remember my awe when I first read the world record years ago.  I was especially in disbelief about the older record though.  7 or 8oz is a very large stone?!!  Why would he not use a smaller one?  It didn't seem right to me but it's recorded.  Maybe he was a very big man, and the bigger stone helped his sling to overcome the air friction?  Anyway, I ought to look into seeing if there is a higher quality steel cable and, attachments then the ones I'm using.  Or some other material like the stainless steel wire, or the spiderwire, you guys are talking about.  I'm pretty busy with other things right now, but I'll help in any way I can.  If anyone can think of another good material, speak up.

Lawn edger cord comes to mind.  But it may be too coiled and not straighten out.  It might also be too stiff and thick.

                                  Ben
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