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Intuitively, it may seem that we'd want to shoot a slingshot as fast as possible so you don't have to adjust for drop. That's really not what we want. We actually want to shoot reasonably fast. Not slow, but also not crazy fast.

At around 70m/s (230fps), at 10m (about 10 yards) a projectile drops 10cm (4 inches) on the way to the target. This is a typical speed for a set of well designed flats with some light-medium weight balls. That's already a pretty good improvement over your typical commercial tubes (Trumark reds which Bill hays tested at 63m/s). The difference in drop is about 2.4cm or about an inch.

But what if you keep on going faster?

Q: What is the difference in drop between a projectile travelling 80m/s vs 70m/s? A: under 3cm
Q: What is the difference in drop between a projectile travelling 100m/s vs 80m/s? A: under 3cm
Q: What is the difference in drop between a projectile travelling 120m/s vs 343m/s (the speed of frickin' sound)? A: under 3cm

The relationship between velocity and drop is a curve. Eventually, you hit a wall. Even bullets have some drop. Theoretically you'd have to be doing at astronomical speeds to achieve negligible drop.

Welcome to the exponential (power technically) relationship of velocity to drop!

Skip to the chart if you have an aversion to numbers.

drop = 4.9 * (range/velocity)^2

because...

d = 0.5*g*t^2 ... equation given in http://en.wikipedia...._a_falling_body

where g (acceleration due to gravity) = 9.8m/s/s

and t (flight time) is range/velocity

Rectangle Slope Plot Font Parallel


When the speed you're shooting at is real low, When you get above 70m/s, the benefit gains become very small for target shooting at competition ranges. The propensity for spin starts to pick up over 90m/s. You can compensate for drop, accurately and repeatably. Just refer to the red line chart and aim that high above your target. Spin and knuckling you can't adjust for. If you want to be accurate, focus on getting a decent medium speed out of your bandset and abandon all fantasies of making super speed bands. Even slower bandsets or tubes can be just as accurate; you just correct a bit more.

Why not just blitz it?

When you go for a super high velocity, you start making other compromises.
  • Thinner, aggressively tapered bands don't last as long
  • Lighter ammo hits with less energy and is more liable to be affected by wind and spin
  • If bands are too heavy they can be hard to draw and release accurately
  • Some people are more accurate with a chin draw than butterfly
If you are into high velocity slingshots, then cool, go for it as long as you don't find the above effects are starting to become unmanageable.

Just be aware that there the returns in terms of drop diminish as you get faster.

But what about long range shooters?

When you double the range, you quadruple the drop. Longer range shooting involves more drop. You compensate in aim and/or in velocity.

Rectangle Slope Plot Font Parallel


Rectangle Slope Line Font Plot


However, if you try to compensate entirely in velocity (faster bands, lighter projectiles) you quickly get into the velocities that start to give rise to spin effects. Also at longer ranges, spin effects are greatly magnified.

http://slingshotforu...shot-knuckling/

As a rule of thumb, you can increase velocity a bit, but unless vertical clearance is limited or you are approaching the limit of your reachable range, if you are firing at fixed ranges, mostly deal with it by increasing elevation (pointing up).

When do you want really fast projectiles?

If you are shooting small (in terms of arc) targets or at an uncertain range beyond target shooting distances but below really long range, then you want all the speed that you can handle. A flatter trajectory means less variance in drop. If the target is small and at an uncertain distance, you could do with a slightly lower velocity and range in with successive shots. Otherwise, you are just taking pot shots.

The same applies to moving targets. If you can't estimate degree to which you must lead your target well, then a shorter flight time will reduce the error. You can't range in, so you have to train and improve your estimation ability or increase the velocity. The same laws of diminishing return apply though.



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strikewzen
Oct 31 2011 10:45 AM

been doing bit of research and calculations recently, these curves are very valuable to me.

being indoor with limited range i have to tune setup to match similar drop as outdoor range while scaling/downsizing the target to get similar experience.

this is my favorite article on slingshots and thanks so much for sharing!


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Rayshot
Nov 01 2011 06:38 AM

Enjoyed it Dan. You are a brainiac. In a good way. Thanks!


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King Cat
Nov 01 2011 07:09 AM

This is very important information Dan, thank you so much.
Jack Koehler


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monoaminooxidase
Nov 01 2011 10:15 AM

Just found out about your blog (or blogs on this site in general, I'm not quite familiar with every aspect of this forum yet...), and heck you put a lot of work into it!
Anyway, thank you for all of it, I find it very interesting and helpful!


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GreyOwl
Nov 01 2011 02:56 PM

"When you double the range, you quadruple the drop"

I noticed an important drop when shooting at 40-45 meters,
but I din't thought so much then you say. Very interesting.

That's why I love butterfly shooting with very fast bands.


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steveinessex
Nov 04 2011 02:18 PM

Thanks for the info. That is where i am weak at the moment, on estimating the drop.
 
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