I'm into trebuchets. Visit thehurl.org for more info.
Here are a few facts I've learned from that great site.

1) Because of the way a trebuchet operates, the release of the sling can produce back spin of the projectile.

2) At high-ish velocity, back spin creates positive lift of the projectile.

3) This positive lift is known as the
4) Positive lift can improve range of throw.
(http://www.mathpages.com/home/kmath258/kmath258.htm)

Application:
1) An overhand sling-throw with release from between the thumb and forefinger causes fore-spin and therefore may cause a drop ball or sinker throw where the projectile actually dives in a curve into the ground.
(Any one here ever see that?)

2) If the sling is reversed in the hand so that the release end is forward of the retained end, then back spin of the projectile may be produced in enough rotational and forward velocity so as to generate the Magnus Effect and improve range.

I have to make a better belt-sling and try it out.

Anyone else do it this way?

ChuckRocks

Yup, consistent (american ) football spin is the holy grail of throwers using aerodynamic ammo.

As for seeing the effect, if you throw anything remotely round it's pretty hard to miss. Throwing golfballs, I'd guess that spin orientation can have as much as 40% impact on range, as the guys that nose-dive *really* veer off course. With an underhand/sidearm throw I tend to slice them off to the right pretty consistently

The overhand styles seem more adaptable to different release angles though I find the desirable release-cord-leading hold to be pretty awkward. Thomas

posted a great looking experimental rig

that included a rigid grip designed to make this easier.  Point first is pretty easy though.

Matthias

I think that there is a positive and negative to this:

1. The backspin creates lift, increasing range and possibly giving the projectile the ability to "hover" over the ground for low targets

2. The backspin conflicts with the air rushing over the top, slowing it down, causing a decrease in penetration power and maybe even range.

I've actually been able to get it to hover which looks pretty cool, especially when it just seems to "want" to smash into the beer bottle (the desert around my house has a lot of junk in it). Maybe further tests would clear up whether this is a good or bad thing?

[quote author=Chaotic Rage  link=1138457004/0#1 date=1138466420]So if you hold the release cord in your thumb and index finger, it will have a negative effect? Do you mean that if you hold it with say your ring or pinky and thumb it will spin better? I hope I understand you. I'll try it. [/quote]

I'm not suggesting that it will work with a corded sling, a belt sling would work best for this type of modified throw.

LoboHunter started a thread on making a belt-sling which can be found at: [font=Verdana][color=Blue][u][url]http://www.slinging.org/forum2/yabb/YaBB.cgi?board=1;action=display;num=1136770587;start=
[/url][/u][/color][/font].
When I use my beltsling, I hold the retension end between index and birdflipper fingers. I would normally fold the sling so that the release end came back into my hand between my thumb and index finger knuckle.
But with a reversed fold, I had to let the retension end come out between thumb and index finger and the release end fit under the tension end.
Both ends were sandwitched between index and thumb.

I agree, a football-like "forward-pass" throw is more accurate in many cases. BUT, as an experiment with the right ammo, this is a throwing method all of us should master. I'm getting over 600 feet with oranges.

And no, you can't make things "hover".
Forward motion is required.
[i]Dough[/i]!

ChuckRocks

Hey mgreenfield!

Take a look at Thomas' post I referenced upthread.  That handle is probably the best way I've seen to throw with backspin. You can sort of do the same thing using a wrist loop, but it's pretty awkward.

I have a bucket full of golfballs that is calling out for a day at the beach. Nice round consistent ammo would be good for experimentation with this design...

Matthias

Matthias, ....wow, that's some rig, but I cant figger out just how it puts backspin on the ball with a close-gripped overhand pitch.   Close grip gives little control over pocket orientation at launch.  The design doesnt seem to reverse the released side of the pocket.  Can you clue me in.   5oz baseballs are pretty heavy ammo!

Golfballs, tho pretty light at about 1.6oz, DO give a great picture of the spin you're launching with. 

I have to think about this backspin-launch puzzle some more.

Thomas' flipper gripper thingie works because the top line releases the bottom of the pouch via that lexan trip mechanism; thereby producing backspin.

I'm wondering is that handle can be extended just a little bit for more of a wand-sling. If I orient the pouch to open from the forward side (the side toward the target during the throw), then I think I can get a consistant backspin.

A low sidearm throw, like a lateral pass thrown from the outside, would produce a hook or a slice if speroidal ammo is not released point-on.

8) I think maybe I'll bow out of this one. Need to get some little pinky dumbbells to work on my gripping strength - or else make sure I've got a solid 150m behind me when I go to throw!

Good line of thinking. I bet you could make a "deadman" release handle that would use a spring loaded thumb-button to drop the cord at the pinky side. A bit like Techstuf's trigger release system.

Matthias