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Projectile Shape (Read 16196 times)
mgreenfield
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Projectile Shape
Dec 23rd, 2003 at 5:09pm
 
Almost all glandes and other special sling ammo pictured or described are roughly football or double cone shaped.    Why not spherical?

One theory is that air resistance causes the "football" to orient itself point-first in the flight path.    Bad football punts dont straighten out in flight, so I have doubts about this theory.    Any ideas???     Thanks!        mgreenfield
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Yurek
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Re: Projectile Shape
Reply #1 - Dec 23rd, 2003 at 7:58pm
 
mgreenfield,

Some discussion about glandes shapes you can find here:

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

I don't think a somersaulted lead projectile can point itself, even though, it will be too late for a good range. So a spherical one seems to be safer. But if you release an elongated projectile right, then it will go further. I suppose elongated projectiles give a greater chanse to get a very good range, however it is more random and require a bigger skill.

Jurek

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« Last Edit: Jan 9th, 2004 at 6:18am 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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Chris
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Re: Projectile Shape
Reply #2 - Jan 6th, 2004 at 4:52pm
 
I have similar concerns as well.  It's really hard to say how a football-shaped projectile is actually flying without seeing it clearly in flight.  When I tested spherical and football shaped glandes, I found they were similar in range, but that the spherical ones were more consistent.  I don't doubt the football like ones are more accurate or deadly, otherwise the romans wouldn't have used them.

Chris
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Gaius_Cornelius
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Re: Projectile Shape
Reply #3 - Jan 8th, 2004 at 2:26pm
 
Writing as a non-slinger who is mainly interested in the History of these weapons, I'd like to venture the opinion that Greco-Roman Glandes were almond shaped for the prosaic reason that they will sit in a small flat sling cradle without rolling out. After all, a soldier might have to wait a while for just the right time to let loose. He may even be expected to move with his sling at the ready while on the battlefield or while hunting. To the ancients, this may have been a consideration that overrode aerodynamics etc.

Of course, some ancient glandes were at least approximately spherical. Is it possible that the ancients understood that for that extra long range, a sphere was the best shape?

By-the-way, ancient glandes are actually generally oval in cross section whereas an American football (or a Rugby football) is circular in cross section. I think "almond shaped" is a better description of the general form of glandes.
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Chris
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Re: Projectile Shape
Reply #4 - Jan 8th, 2004 at 3:40pm
 
Interesting.  Anyone have any ideas why such a shape (with an ovular cross-section) would be beneficial, other than making it less likely to roll out of the pouch.  Any aerodynamic reasons?
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Whipartist
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Re: Projectile Shape
Reply #5 - Jan 8th, 2004 at 4:07pm
 
Gaius Cornelius has a compelling point.  An oval cross section doesn't seem at all right to me for aerodynamic efficiency.  I won't throw it out, but it seems they maybe had other considerations in mind.  Manufacturing or speed of throw, or who knows?
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WalkingBird
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Re: Projectile Shape
Reply #6 - Jan 8th, 2004 at 9:13pm
 
Seems to me that everything exiting from a sling pocket has a spin imparted to it by the unfolding action of the sling. This appears to be the reason for the hum observed when throwing flat shaped stones. Because the glandes would be placed cross ways in the pocket and  perpendicular to the sling, the spin would imparted around the long axis of the glandes, (this would not be the case with a punted football). This spin would have a stabilizing effect on this type of projectile, If indeed they end up flying point first, it would not take place until the apparent wind had time to take effect and slowly turn the glande into a position of least resistance. In short, It ain't no short range thang. The further the glandes goes the more likely it is to be flying point first.  But perfectly matched cone shaped ends would receive the same effect from the apparent wind making it difficult for a glande exiting a sling to "choose" which end points first, that is to say no "weather vain" effect. So my guess is that if one end were bigger, left with a casting seam, flater, or what ever, may help to cause the glande to smooth out to point on flight.  Having said all that, I could be wrong, but that's the view from here.

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Chris
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Re: Projectile Shape
Reply #7 - Jan 9th, 2004 at 3:07am
 
But if it were to leave the pouch spinning, like a bullet or good football throw, the ovular cross-section would cause drag (because it's no longer circular) and cause it to slow down.  It would be like riding in a car with square tires.  If they really are not circular in cross section, the whole theory of point first, spinning, bullet-like projectiles seems out of the question.
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Gaius_Cornelius
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Re: Projectile Shape
Reply #8 - Jan 9th, 2004 at 8:52am
 
It would be interesting to know if anybody has actually experimented with hunting (or simulated hunting) using an sling and glandes of ancient form. i.e. a sling with a flat diamond shaped cradle and almond shaped lead bullets.

In which case, is the shape of the glandes convenient for holding in the cradle without falling out? Or is this simply not how it is done?
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WalkingBird
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Re: Projectile Shape
Reply #9 - Jan 9th, 2004 at 11:26pm
 
Chris, if I'm reading your reply right, what you are saying is that when the glande first leaves the sling it will be cross ways to the direction of flight? And due to this orientation would present more surface area to the apparent wind, thus causing a greater amount of drag.

If that is what you mean, I would agree the initial drag would be greater even if later it becomes less. But the reason for making glandes in the shape they are may not be for greater range, but greater effectiveness. That is, if indeed they do end up flying point first, the cross sectional density would go up for the same weight of projectile. As you know pointy things do a better job of bashing through shields, armor, flesh and bone better than blunty things. So to throw pointy things may just plain be more effective on impact even though the range may not be increased at all. Any way that would be my guess.
I've literaly got enough lead to throw away and one of these days when theres time I'll make up a couple of molds, make some pointy things and see how they work. Make some blunty things to compare to. I'll try and see what difference shape makes.
It ain't science but it is fun!  Cheesy

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Whipartist
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Re: Projectile Shape
Reply #10 - Jan 13th, 2004 at 4:45am
 
So far, with clay glandes, I've noticed they tend to hit my target on the sides, not the points.  This is close range, but shows approx how release is.  

They spin on the axis.  My glandes are watermelon, not almond.  I think that the almond shape could be because they are easier to load and fire.  However, round shouldn't be a lot harder, so who knows.  It could be that ancient casting techniques made almonds easier to make than footballs.  Who knows?  I'm not sure how aware the Romans were of aerodynamics.  But if they were, there are other considerations.

A backspin on an appropriately shaped gland, would produce a lift.  I'm sure every slinger here has observed that effect in their slinging.  Depending on your stone, and your style, and your release, you've had sling stones curve up, down, right.  Probably not often to the left.  But maybe left too.  Well if you're left handed......  

In airsoft guns, they produce a backspin on the bb's called "hop-up" to keep them flying level over a great distance.  And it works.  My 250fps, airsoft pistol shoots a flatter tragectory over 30 yards, than my 400fps pellet pistol.  Backspin on smooth bb's.

If a gland was made right, and the slinger released right, the backspin would effectively increase range.  The glandes would be literally "flying."  Normal projectiles don't fly, they fall.

I don't know if anyone on our forum uses the underhanded "baleric" slinging technique, but I've found it puts a bottomspin on the stones, and they curve into the ground.  Overarm should do the opposite with shorter slings.  Longer slings need a horizontal throw.  

So we need to consider what types of slings we are talking about and so on.  In a hoard of other slingers, and other various battle conditions, long slings may not be too practical.  But short, over the top slings, could be.  And almond glandes in over the top throws, could be really nice.

Having said all that, the explanation is probably just manufacture, or speed of loading and some other utilitarian thing.   Smiley

This forum is pretty cool.  It's amazing how much of a resource it's become, so quickly!  And new members every week!  Who would have ever known slinging was so popular!  You've started a revolution Chris!  That's a pun btw  Wink

                                         Ben    

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Hondero
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Re: Projectile Shape
Reply #11 - Jan 13th, 2004 at 2:04pm
 
Hi Ben... The famous design in almond that so many doubts raises... As you say, the projectile takes a certain effect according the launching technique.This effect takes place when rolling the projectile on pouch, and have a fundamental utility that it is to maintain the stability of the position of the projectile in the fly (gyroscopic effect). Also it can be used to obtain more range by elevating the trajectory, like in golf, but the fundamental thing in slinging is the is first, that it can be used with the suitable technique to send projectiles point forward. Then, like glandes are small and smooth, the effect that they takes when throwing is small, because they slip on the pouch  instead of rolling. For it, almond shape was the solution, that used to have even two edges marked in the widest section, so that when rolling on the pouch got more clench and didn´t slip, taking the projectile better spin. That is the secret of the famous Roman almonds of plumb. Those guys were very clever  Smiley.

Saludos
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He brought a conquering sword..., a shield..., a spear... , a sling from which no erring shot was discharged.&&
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Yurek
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Re: Projectile Shape
Reply #12 - Jan 13th, 2004 at 9:26pm
 
I have observed two extreme kinds of a fly of the flat stones:

The first one, when the stone is rotating like a throwed up coin. Then it flies making a loud hum, and the trajectory is crooked due to the strong Mangus' effect and a lift of a flat profile. Such shots are short and inaccurate, of course.

The second one, when the stone is rotating like a disc or a boomerang.  Very probably it slips itself off from the pouch flat, and get the flat rotation by cathing the pouch edge. This kind of a fly can be very far and stable, sometimes. The rotation stabilises the stone which gets a lift just like a disc or a wing. It happends rather seldom.

How the flat stone will start depend on how it is situated in the pouch and what is an angle of the pouch relative to the trajectory durring the release.

Such effects sure aren't so very apparent for the flat shaped lead glandes, but they could appear however. Then maybe the ancient warriors would like to get the loud hum which had the psyhological working durring a mass volley. Or maybe just the "disc" fly of the glandes? Well, it only my free reflections. I dont't know how flat is the cross section of the Roman glandes.  

Maybe it is worth the consideration.

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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justbarak
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Re: Projectile Shape
Reply #13 - Jan 13th, 2004 at 10:18pm
 
I was wondering the same thing about the almond shape - that it might possibly provid grip in the sling to increase spin when it is released.  The same thing is done to the drill in a bow drill for making fire without matches.  The drill is given an oval shape or edges in order to provide a gripping surface for the bow string to grab and rotate the drill.  Otherwise the string just slides without spinning the drill.

The various techniques for throwing are mentioned throughout this thread.  Can someone describe them: overhand, underhand, etc?  I'm assuming that a clockwise rotation (relative  is the most universal ,and in that, a vertical rotation or a horizontal rotation, and then something around 45 plane of axis (the blue, green, and red circles on my little photoshop stick man slinger - the starred arrows being the rough point of release). Then there is a counter clockwise rotation as well, which I imagine is only used in a vertical spin.  What purpose is a cc throw?  Is it accurate at all (I only use it for spelunking frogs in the pond out back Grin)

...

Just imagining the throws, it seems like the clockwise 45 degree rotation would release the projectile in a more pointed position rather than totally broadside.  But I'm not sure.  I need to make another sling and try it out.  In PNG (Papua New Guinea) down in the Sepik flood basin where there are no rocks but lots of clay the village kids made clay shot which they dried in the sun.  It was round.  Not that they are as advanced as the Romans were  Smiley

Barak
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JeffH
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Re: Projectile Shape
Reply #14 - Jan 14th, 2004 at 1:12am
 
Barak,

Great illustration!  I think the release points are a bit late in the circuit, but otherwise seem accurate.

I can't get anything but distance from the underhanded sling style.  So I use a one-circuit (wind-up) style.

It starts with the stone hanging.  I sling the stone up and around my head and let go in an elevated side release.  Stand and point your right hand at the ground.  Then raise your arm until it is about 30 degrees above horizontal.  This is the change in angle of the stone, but it occurs in a full rotation.

This is probably not a very good style, but I have no one to teach me better.  I find multiple rotations to be very difficult to master, though sometimes more accurate if I limit it to two.

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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