Matolay,

Yes that is helpful!  Thanks.  I've seen some Peruvian slings made with a cradle with a net center.  Very intriguing. 

                                   Ben

Jurek,

Great looking sling up there my friend.

Keep up the good work.

jeff <><

More one week ago I tested the lead projectiles. Some was ball-shaped and some prolongated. The weight of the balls was almost 120 g (4.2 oz).  Although I intended to get 100 g but I didn't measured off volume of the modelling paste too precisely. Elongated ones was 100 g (3.5 oz), exactly as I wanted. I used the last ones in the previous test too.

The sling is made of the 1,1 mm (0.043") "Dyneema" thin line, according to the Ben's idea. That line is able to raise 90 kg!

The projectiles had no grooves for keeping in the cradle, so I used the short and narrow sleeve made of chamois-leather. You can see that in the left-bottom corner of the picture.

I throwed the glandes on the frozen and snow-covered lake. Alas, I wasn't able to find any of them due to the traces on the snow and coming dusk. So I have no conclusion what the shape and aerodynamic sling do for a range. I have written about it in some post before, but here are the pictures. My wife had painted the projectiles with the nail enamel

I see that finding (marking) the fall-points is the big problem. I'm thinking about it. Maybe you guys...  and girls have a good ideas?

Here are the pictures:





Greetings,

Jurek

Very interesting discussion and one I'd thought about before. But then, what slinger hasn't thought about setting the world's distance record!?

This conjurs up all sorts of old memories. Hondero reminded me offline that I once had offerred to host an International Slinging Competition including distance. I have a piece of property long and skinny. I think it is almost 500 yards long, maybe not long enough!

Some idle thoughts to keep the gears working:

If you are going to place a world's record, it would be wise to observe the Guiness' methodology, even if you weren't going to send it to them. They've worked out the kinks a long time ago.

Stretch in skinny cords is disconcerting (I know) and I'm sure it steal velocity, but it may increase spin. During the release, the cord shortens, pulling the pocket with it, spinning the glandes.

As velocity doubles, drag quadruples. So, at some point, the drag on a long sling will actually REDUCE velocity!

Consider using low drag cords. Not only reducing width like you have all talked about, but making the shape aerodynamic, or adding longitudinal grooves on the surface of the cord.

Also, consider using aerodynamic glandes having a cross-section like a airfoil (plane strut). Somewhere I have a NACA foil shape CAD file that you can resize to any width and length if anyone cares for it.

Finally, use something heavier than lead like depleted uranium to cast your glandes.   

Ain't this fun!

If anyone cares for the math (it is way beyond me) here is the formula for calculating the drag and power needed to rotate a pair of wires in a circle. How perfect is that!

http://www.mh-aerotools.de/airfoils/control_line_aero_3.htm

What it boils down to is:

Halve the cord diameter, halve the drag and power required.

Doubling the velocity increases drag 4 times (like I mentioned earlier).

Here is what surprised me. Doubling the velocity increases the power required to obtain that speed by 8 times!  We've all experienced this trying to 'helicopter whirl' a sling faster and faster, but hit an upper limit.

With a little more math one should be able to figure out what the ideal cord length would be for the fastest release velocity given the power available in the human arm.

Yurek!  Those look amazing!  I'll add them to the gallery at some point.  What is the approximate cost of each one? 

Once the snow clears, will you head out to some field for an official range test? 

Chris

mgreenfield,

Thanks for an idea of measurment. It is very inventive and would be a good way but I'm afraid that GWR require that the projectiles should be marked and recovered. All must be probably documented pretty exactly, filmed and photographed.

Lately I thougt about the local sport airdrome, the problem would be in good marking the points of impact on the concrete slab. The projectiles probaly will bowl far from the impact points , maybe not (?)

Quote:


Me too, maybe the (mentioned by Jeff) snikers molds are the good way for it? Each time I casted limited number of the glandes in the plaster mold and they was finishing off too quickly

Dan,

Thank you for the quidelines. Each of them is worth consideration. I like that site about a lines drag. The formulas give some image of numerical influence of different factors, interesting.

Jean,

I have read your posts with care. They are interesting and substancial. I like idea of the net pouch and way of fixing it. It is pretty simple to do and really seems working well. I'm under the impression of your privity about different uses and techniques related with a sling. I'm sure I couldn't describe my slinging ways as well as you in my native language

I never thoguh seriously about a sling as a defensive tool, because I'm not sure what my accuracy would be in the critical situation. Hope I never will be in that situation in the future. However it happened once when I was yang man. Then I really used the sling for the self-defence. But that story seems to be out-topic.

Chris,

They don't cost much money, bacause I have bought some lead cheaply on the scrap yard. The plaster (of paris?) and the modeling paste are pretty cheap too. But making the good mold required a trial-method. Casting and removal of some surpluses eat up a bit time too.

Before I thought to do it at the ice-plate in the winter, but now I see that it require special weather conditions. It is almost impossible for me to hit them with all organisational job . Thus I hope it will happen in the early spring, probably at the airdrome-plate, when we won't be dependent on the weather so much. I would like to do it as quickly as possible.

Ulrica,

Thanks, the metal-dedector is great idea! I have no experience with it and I'm curious how sensitive that device is. I would be honoured seeing you as the second

Jurek