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Sling bullets from ancient Cyprus, one very big (Read 10283 times)
HuntsmanSling
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Re: Sling bullets from ancient Cyprus, one very big
Reply #30 - Mar 1st, 2016 at 10:36am
 
Morphy wrote on Mar 1st, 2016 at 5:12am:
Flight through the air yes. But there is more than just it's flight through the air to take into account. Such as how well it can be released from a sling realistically.

That's what I've been telling you guys this whole time!  Smiley
It's all about proper contact with the pouch before release. For goodness sakes lol

Tomas wrote on Mar 1st, 2016 at 6:29am:
Sounds like this is a new idea to you Hunts but it is worth being open minded about it.
I think an egg shape would have great surface contact with a pouch whether it's a solid or split pouch. I suppose if you're arguing for better contact you should try a solid pouch too. An egg will fit great in either.

This also goes along with what I've been saying. Solid pouches have an egg shaped base for optimal contact with football shaped stones, eggs, or glandes. So again, the shape of the projectile is for best contact with the pouch whether it be a solid pouch or split. Split pouches also have an egg shape to their bottom but it follows an invisible path, plus has only two contact points which reduces friction.

I will try to be more open minded but damn guys you are essentially agreeing with me. Smiley Tongue




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Thearos
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Re: Sling bullets from ancient Cyprus, one very big
Reply #31 - Mar 1st, 2016 at 12:36pm
 
I hope nobody minds if I summarize my thoughts after reading this thread and rooting around a bit. 

I note that in fact, the most aerodynamic shape is the tear-drop / rain-drop / pear-shape which Jaegoor was asking me about a few weeks ago.

https://www.quora.com/Why-is-a-tear-drop-shape-more-aerodynamic-with-a-round-hea...

https://www.reddit.com/r/askscience/comments/21rz0t

Interestingly, one issue here is one of frontal drag: a point generates more drag than a smooth rounded end. Some sling bullets in fact do have very rounded, egg-like extremities (others, on the other hand, have super pointed extremities-- esp. in ancient Spain, perhaps on the instinctive idea that the bullet "pierce" the air in flight).

I assume that having the rear end of a sling bullet tapering is the same principle as a boat-tailed bullet-- in reduces drag in flight.

So perhaps the most aerodynamic sling bullet would be a tear drop (round nose, long sharp tail; the problem is that the asymmetrical shape would not facilitate clean release. So the next best shape is "football shaped", but with rounded extremities to reduce drag (rather than sharp points): it is aerodynamically efficient but also shoots cleanly. There are some asymmetrical "pear-shaped" sling bullets which in fact are aerodynamically optimal, but they may be harder to shoot, and in any case need a bit of thought to load (which, in a combat situation may be less than ideal).

Why are modern bullets, for firearms, not shaped like a tear-drop ? I assume this is because they need a flat base for the propellant to actually act on the biggest surface possible.
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Tomas
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Re: Sling bullets from ancient Cyprus, one very big
Reply #32 - Mar 1st, 2016 at 2:05pm
 
Thank you Thearos that's exactly what I'm getting at!
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Re: Sling bullets from ancient Cyprus, one very big
Reply #33 - Mar 1st, 2016 at 2:25pm
 
Thanks for the post Theoros.

Well those two articles are 100% true when comparing the drag coefficient moving in a forward direction.

However, I thought football shaped glandes spin upon release from a sling pouch in a helicopter fashion. It didn't occur to me that a football shaped glande was simply going forward like a bullet spinning on the smaller axis.

I'm pretty sure a football shaped glande thrown from a sling does not fly as an American football does in a conacle forward motion. However, this thought just occurred to me.

Is this what you guys have been talking about the entire time?

If so, you guys are right about the football shape being the most aerodynamic and you've just blown my mind. Tongue

I'll have to do some experimenting to prove your point. I just wish I had a slow motion camera!
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Morphy
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Re: Sling bullets from ancient Cyprus, one very big
Reply #34 - Mar 1st, 2016 at 4:06pm
 
A properly thrown glande will rifle like a bullet when leaving a sling.    The idea is finding the shape of the glande that has the best aerodynamics combined with the cleanest release.  Throw in changes in pouch shape, throwing technique, sling lengths etc, and you have a very-difficult-to-test weapon.   Smiley
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Re: Sling bullets from ancient Cyprus, one very big
Reply #35 - Mar 2nd, 2016 at 2:58am
 
Right, I just wish ONE of you would have put into words that the football shaped glande was flying on it's smaller axis in the air upon release.. If you had done this I would wouldn't have argued you. Instead I had to figure it out on my own and then reply.

grrrrr. come on it wasn't that hard  Angry

..but thanks for teaching me something  Wink
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Re: Sling bullets from ancient Cyprus, one very big
Reply #36 - Mar 2nd, 2016 at 5:09am
 
When i discovered "rifle spining" with a sling i thought nobody would use it, then i discovered it in older posts in this forum.The reason i needed it was that my place has more elongated stones than round , so i would rifle spin it or i would just throw buzzing stones all over the place.
Necessity is the mother of invention. Wink


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Thearos
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Re: Sling bullets from ancient Cyprus, one very big
Reply #37 - Mar 2nd, 2016 at 7:26am
 
I didn't, in fact, specifically mean spinning--though it's true that the football-shaped bullet does spin after stabilizing in flight, which no doubt also affects the performance. I assume a tear-drop shaped bullet also spins. In fact, don't all sling projectiles spin ?
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Re: Sling bullets from ancient Cyprus, one very big
Reply #38 - Mar 2nd, 2016 at 9:45am
 
@Thearos yes all projectiles will spin if launched with a sling.But at what direction? As a newbie back then i used narrow grip all the time and this means you have little control over the axis of the spin.So the stone may be released with : backspin/frontspin/spiral(rifle spin) or even a combination which will make the stone have unexpected trajectory.

I must add that for spiral throws and elongated stones the angle of attack plays a huge role on the trajectory .
Check this out : http://biomechanicsofajavlinthrow.blogspot.gr/2015/06/optimal-javelin-flight.htm...

we can learn a lot from javelin throwing and pitching mechanics.



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Re: Sling bullets from ancient Cyprus, one very big
Reply #39 - Mar 2nd, 2016 at 10:35am
 
I am going to guess that most sling projectiles spin to a greater or lesser degree, due to the gland "rolling" out of the pouch when thrown.

Also, projectiles with uneven or jagged corners "buzz" or whine when thrown, leading me to guess that they are spinning at a very high rate.

I have made some biconals about the size of a golf ball, most throws from a split pouch cause them to "rifle" or spin on their long axis.  You can see them wobbling as they first leave the pouch but as they spin, the wobble decreases and the gland stabilizes and goes a longer distance than a round gland of roughly the same weight.

And, FWIW, if it comes out of the pouch stable, that sucker is going to go a lot further than a wobbly one or a round one. 

I haven't experimented with egg shaped glands.  I have plenty of clay, so I will give it a try later on this year and report back.
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Re: Sling bullets from ancient Cyprus, one very big
Reply #40 - Mar 2nd, 2016 at 3:04pm
 
This is Morningstar's vid  on this phenomenon

https://www.youtube.com/watch?v=PvidIcGUXkQ

Bill's comment that the biconal flies further than the sphere seems to show that the shape *is* aerodynamic
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Re: Sling bullets from ancient Cyprus, one very big
Reply #41 - Mar 2nd, 2016 at 9:08pm
 
Of course it's aerodynamic... lol.  We are over thinking this. Football, egg shape etc are all aerodynamic.

As far as spin goes how you sling and even the orientation of your palm at release can really affect spin. I use to use a palm forward toward the target release with my Balearic throw. I was always puzzled when the glande would dive bomb into the ground after about 40 meters. I finally figured out if I keep my palm pointed more upwards upon release it would fly straight and level, and consequently maintain velocity much better because hard, non rifiling spin saps velocity.  This mainly happened with shorter sling lengths and my particular throw. No one else seems to have this problem.  So ya, tons of variables involved.
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Re: Sling bullets from ancient Cyprus, one very big
Reply #42 - Mar 15th, 2016 at 12:10pm
 
I'm just going to tip-toe away from this thread....


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Re: Sling bullets from ancient Cyprus, one very big
Reply #43 - Mar 15th, 2016 at 7:08pm
 
wimp whistle
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Re: Sling bullets from ancient Cyprus, one very big
Reply #44 - Mar 17th, 2016 at 6:56am
 
OK....

From my experience...

Getting a biconical to release cleanly and rifle-spin correctly from any sort of helicopter/sidearm throw is difficult due to pouch orientation and the tendency for the cords to twist when you "break" your wrist. Watch some slo-mo vides to see what I'm talking about. The shape of an oblong projectile also offers some aerodynamic challenges as you wind it up. It will want to go "flat side" into the wind, like a piece of plywood flying off a car roof (if that makes sense). It doesn't take much to get it go sideways.
Essentially what you are trying to do is fly one of those tethered airplanes.

I'm not saying a Balearic slinger cant rifle spin...you can rifle spin from any release, even underhand.

But there is one technique that is superior, again, in my experience. When you drop the pouch in a fig-8 with your palm up, you are "flying" the pouch in a nice, slow transition to release without twisting the cords, and the projectile will want to go up as it comes out of the pouch...in line with the lift that is created by the spin. Thats why quarterbacks throw overhand.

A biconical will stabilise better than a teardrop because the mass is in the center. Most of the pointy teardrop shapes I've fooled around with get "tail wobble" and increased drag. Biconical seem to naturally stabilise.
An American football is also helped by the laces. They keep airflow attached around the rear of the ball in flight, reducing drag. There are some videos that demonstrate the boundary layer, laminar flow, etc

It could be that the inscriptions on lead glandes were not only there for their psychological effect...they might have figured out that they flew further and were more stable with them than without them.

The tear drop may be the most aerodynamic is some situations, but we are talking ballistics here. There are other forces at work.

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