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Air Drag On Sling Cords & Pocket (Read 27226 times)
SnapCut
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Re: Air Drag On Sling Cords & Pocket
Reply #60 - Feb 9th, 2004 at 3:18pm
 
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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



The slings that I made were from leather boot laces with small leather pockets.  When used they sounded like the crack of a whip or a 22 being fired.  I guess that means some part of the sling is going faster then sound.
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Re: Air Drag On Sling Cords & Pocket
Reply #61 - Feb 9th, 2004 at 5:12pm
 
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I'm full of admiration for this man. I'm very interested on his
next posts, if they exists, of course. Hondero, do you have maybe a contact with this man?

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I´m writing a slinging friend from New Zealand that posted him and David P.Engevall, just wait if he answer me... two years without contact.
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Dan_Bollinger
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Re: Air Drag On Sling Cords & Pocket
Reply #62 - Feb 9th, 2004 at 6:08pm
 
Jurek,  Thanks for the clarification, I didn't understand your point.  I think a pocket could be made for a long dart. Some of the point and most of the tail could extend past the pocket. After all, cestrosphendrons can be tossed with a sling and they have a 1:30 aspect ratio! Where is it said that GWR requires a classic sling? I've not read that.

There is a historical note about grooved glandes being tossed by a simple loop of cord. I forget where. I machined one and it works. It looks like a yo-yo. Did you know that yo-yos are descendants of Phillipine hunting slings?  

www.claycritters.com/sling/groovedglandes.jpg
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Re: Air Drag On Sling Cords & Pocket
Reply #63 - Feb 9th, 2004 at 7:38pm
 
magnumslinger,

Thank you for the interesting tips, as usual. They have given me the idea. If we wrap up (maybe two or 3 timesand maybe a bit slantwise) the projectile and folding fins tightly with the band (belt,tape ?) of a soft leather or something like that, and fix the free ending of the tape to the ending of the retention cord, than we will get the tight roll rested in the cradle. That roll should sit in the cradle pretty stably. Durring the release the dart will roll off and will get the good spin and the free fins will spread themself. I know that rolling off will take a part of energy but it will give the pretty good rtotation instead. Tan maybe the fins would't be unnecesary? Just idea.

But I'm still not sure if such projectiles will admited by GWR, since they have said "a stone" in rules.

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 #64 - Feb 9th, 2004 at 7:46pm
 
Dan,

Go to the site nr 5 of this thread. I have quoted the GWR rules and the information about the last record. I have got this information just from GWR.

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 #65 - Feb 9th, 2004 at 7:54pm
 
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I´m writing a slinging friend from New Zealand that posted him and David P.Engevall, just wait if he answer me... two years without contact.


Hondero,

Please, let me to know if you will get something new. I would be grateful.

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 #66 - Feb 10th, 2004 at 4:50pm
 
Wow,

This is a long thread.  I will throw in my two cents.  Most of my slings have used had oval or diamond shaped pockets.  Generally these measure 6" x  3".  The one I am currently using  is more of an oval.  I have tried various things for the cords. 

Round leather lace from Tandy leather (1/8") was susceptible to breakage.

Mason layer's twine was fair but tended to twist and tangle.

On my current sling I used 1/4" square cross section leather lace.

Going from diamond to oval pouches has definitely increased the size of the rocks or dirt clods I throw.  They are held more securely but with the combination of the increased pouch area and larger diameter cords wind resistance is increased, I think?  To compensate for this missile size has increased.

Scott Adair
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Re: Air Drag On Sling Cords & Pocket
Reply #67 - Feb 10th, 2004 at 5:36pm
 
Quote:
There is a historical note about grooved glandes being tossed by a simple loop of cord. I forget where. I machined one and it works. It looks like a yo-yo. Did you know that yo-yos are descendants of Phillipine hunting slings?

...



Dan I just have seen that picture, before it didn't download itself. This is interesting, I'm curious if that missile isn't rubing the cord. I understand that the groove must be deep due to stability but it seems to make  the release more difficult. I'm also curious if the missile gets a strong rotation.

If the thin split-cradle is used than two grooves on the projecile may be more pointless.

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 #68 - Feb 10th, 2004 at 6:00pm
 
Welcome adair3

I see you use rather a big pouches, the same like me not long ago. My new stone slings have reduced pouches however. Now I see that smaller ones are more efficient due to smaller drag and an easier release. Often the full surface of a big pouch isn't holding up the stone. I think it is good to cut surpluses off a bit. Unless you throw very big rocks.

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 #69 - Feb 10th, 2004 at 6:24pm
 
Yurek, The cord in that picture is very thin, about 1.0mm, probably too thin for this glandes.  And, I think the groove doesn't need to be that deep. However, the deeper it is the faster the rotation will be. Of course, brass is a poor material for a glandes, too slippery and too expensive. I just made this because it was easy to do on my lathe.
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Re: Air Drag On Sling Cords & Pocket
Reply #70 - Feb 11th, 2004 at 10:41am
 
Yurek,

I saw a post of yours with a picture of several sling pouches.  What is the length and width of your pouch with the split running down the center?

Scott Adair
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Re: Air Drag On Sling Cords & Pocket
Reply #71 - Feb 11th, 2004 at 3:04pm
 
Scott,

That pouch dimensions are 3 x 13 cm (1.2" x 5.1"). That one is a bit used and  streched now. I have made that for lead glandes but I use that for stones too. If stones aren't too big or irregular, they sit in that pouch not so bad. This is mainly the "sport" sling for ranges. Normally I use a bit bigger pouches for stones.

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 #72 - Apr 10th, 2004 at 4:54pm
 
What is there about the classic Roman lead glande shape???

I was out today picking up stones I'd pitched the last few days.  I found one about 50% further out than the bunch on the ground at my usual range.

It weighs 55grams and is an almost perfect copy of the Roman glande shape, ....just a little more blunt on the ends, and just a little more rounded on the edges.

What IS there about that shape???   mgreenfield
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Re: Air Drag On Sling Cords & Pocket
Reply #73 - Apr 10th, 2004 at 6:14pm
 
Im not sure if anyone has sugusted this or not but if u were using something that hurt your fingers you could put a small piece of leather or something around your finger.  Im not sure if it would mess up your performance but its worth a shot if your sling starts to hurt cuz you because it is so skiny.  just a suggestion.
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Re: Air Drag On Sling Cords & Pocket
Reply #74 - Apr 11th, 2004 at 11:38pm
 
Mike, I often wonder the same.  I'm in contact with a physicist who does fluid dynamics.  I'll keep everyone apprized of any developments.


For those that are wondering what that shape looks like:

...                ...

...
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