For the loop that goes around your finger (or wrist in some cases), you could pad it out by sliding on some sort of tubing (like miniature pipe foam) or wrapping it in a fabric.  It might be possible to modify a driving, paintball, or archery glove to cover the upper half of the finger you use for the retention cord.  This would distribute the cord’s force better and probably be comfortable after a while. 

The thumb ring was developed by the Mongols I think.  Keep in mind the forces involved with drawing back a real (battle) bow are higher than with a rotating sling (in my opinion).  The thumb ring was to protect the thumb in addition to providing an accurate release.  It might be an overly complicated design for a sling.

But, you have got me thinking about some sort of release system.  Like on composite bows with there pinching release thingy (sorry, I only shoot traditional).  What if a similar device could be held/attached and "clicked" at the appropriate point?  Anybody think there would be better accuracy or comfort? 

Slinging relies a lot on sensation, and the more you add, the less you feel.  It's a tough compromise, but if anyone is willing to give it a try, I'd love to hear how you get on.

Chris

Archeorob, I have fairly soft, weak, whimpy hands. (Except for the calluses from my chain maille hobby.)  As such, I pad my hands as needed, others may not need to. People differ.

Consider a simple finger ring though.  If one is made that is twice as wide as the string, then you've distributed the load over twice the area.  This may be enough to prevet any blisters, abrasions, etc.

Your correct though in that some folks may not like the loss of "feel".  Again, different strokes for different folks.

Another possible griping method (just to add fuel to the fire), one that I did try a long time ago.

Instead of anchoring the sling to a finger or wrist, I braided a handle, using paracord. (Forgive me, but the name of the weave I used escapes me at the moment.)

The result though was a flexible length of braided cord about 3/4" thick.  This I grabed in the palm of my hand, using the last 3 fingers to do so.  The other sling end was gripped in the usual fashion between thumb and forefinger.

It did take a little gettting used to, but I did and prefered the way both lines ran parallel to each other, even through my pinch of the release end.

One of the results was that the only part of my hand that got abraided at all was the thumb tip and inside edge of my forefinger, which wasn't so odd of course.

I know I am getting in on this one a bit late, but here are a couple of thoughts.

As to the release mechanisms discussed earlier like the ones used in archery (I shoot both compound and traditional), I would say that the purpose is different all together.  If you think of the movement required by an archer when releasing a string by hand, the fingers have to move quite a ways.  The sling, on the other hand, has only the movement of two finger about 1/4 of an inch apart.  If you where to replace the fingers with a caliper style release, I would say that accuracy would be compromised quite a bit because the trade off of movement vs. feel is too great.

As to the wear and tear to the hand, I have found a good quality leather glove (usually deer skin works best) allows me to overcome the abrasion factor while still maintaining the feel.  I am, however, interested in the braided "tail" to hold on to.  Did it seem to help that it was still flexable, or would a solid (possibly wooded) handle add more stablilty?  I guess that starts getting into the sling staff area then.

Well, those are my thoughts.

Ron

I made a 9-foot sling that fired bricks and it only had a finger loop.  Making a fist around the cords helped distribute the weight.   Attaching to the wrist does seem like a good idea though.

I've tried with water balloons before, and it's very difficult to launch them without breaking.  The centripetal force is so intense; they flatten out in the pouch and break.  I remember a water balloon sling being sold at slingstones.com (since closed).  It had rubber tubing for cords and a sizable net for the balloon to sit in.

My first experience with slings was with some nylon webbing that we improvised for a sling.  It was about 3" wide, I'm not sure how thick, I think about 1/8" or less.  We took a couple of wraps around our sling hand with one end, and pressed the other end against the wrapped end with our thumb.

Unless you used a very heavy rock, there wasn't enough sensation to tell where the rock was when you were winding up for the release, so we had to use pretty heavy stones, I think a half pound or more in weight.  That contraption worked remarkably well, and we were able to get pretty fair distances with a throw. It has been so long ago I would only be guessing at the distances, but I think it was greater than a city block.

Even with the heavy stones we were throwing there was no discomfort. I am going to look into locating some webbing and try that again.  At any rate, if you did use webbing for the grip it would distribute the weight better?  What do I know? Anyway I couldn't resist passing that along.

seat belts are a pretty solid strap - how do you get webbing from them ?