# The effects of uneven band length



## Charles (Aug 26, 2010)

Some folks have suggested that uneven band length can cause fork hits. I thought I would test this idea using my testbed slingshot.









On a slingshot with a 2 inch gap between the forks, I used a pair of bands with one 7 inches long and one only 6 inches long. I did find a significant deviation in the placement of the shot as compared to a pair of bands both 7 inches long. However, there was no fork hit. You will find the video here:

http://slingshotforum.com/videos/view-45-the-effect-of-uneven-band-length/

I figure a one inch difference in band length is pretty severe, and I doubt any of you have accidentally had bands that were that unbalanced. So based on these tests, I do not believe that in general different length bands are a major cause of fork hits.

Cheers ...... Charles


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## ash (Apr 23, 2013)

Good test. A close-up view looking down onto the forks might be revealing. In slow motion it would likely show the ammo and pouch passing perhaps 3/4-1" closer to the short-band-fork, but not hitting because the fork itself is still a little bit wider than that.

In practice, a human hand is going to react to the assymetric loading given by the uneven bands, which itself have an effect by way of the speed bump or tweak effect, which ever term the reader prefers.


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## Charles (Aug 26, 2010)

Using similar triangles, a 1.5 inch deviation at 128 inches (96 inches target distance + 32 inch draw) amounts to a 3/8 inch deviation at 32 inches (at the fork gap). So there was a lot of room to spare.

With a 2 inch fork gap, the shot would have to deviate by more than a full inch at the forks to get a fork hit. The unbalanced bands would have to produce a 4 inch deviation at 8 feet in order to have a 1 inch deviation at 32 inches ... I just do not know how unbalanced the bands would have to be to produce that much deviation, but it would be very substantial.

Cheers .... Charles


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## e~shot (Jun 3, 2010)

Good info Charles,


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## mr. green (Nov 3, 2012)

Thank you for sharing, Charles. Very comforting to know that we have a lot of room for error.


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## Bill Hays (Aug 9, 2010)

I'm kind of thinking that uneven bands being pulled by a person would have a different result... as a person's natural instinct is to even out the draw force while pulling, so it may cause a person to tilt the fork with the shorter band back towards the pouch more... thus causing a smaller gap and an increased likelihood of a fork hit as compared to clamping the fork for a perfect perpendicular draw.

One thing I might suggest though is, having the release mechanism be adjustable so that it matches the angle of most people's release... what I mean is, is it should be able to release in the vertical, horizontal and or diagonal plane.

Anyway, it's an interesting device Charles and I'm sure with a creative mind such as yours you'll find all sorts of things to check out!


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## SuperMonkeySlinger (Jan 28, 2013)

Great test Charles! I appreciate it.

Also happy to see that your still having fun with those office bands! Atleast those bands look like #105's.

SMS


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## Charles (Aug 26, 2010)

Bill Hays said:


> I'm kind of thinking that uneven bands being pulled by a person would have a different result... as a person's natural instinct is to even out the draw force while pulling, so it may cause a person to tilt the fork with the shorter band back towards the pouch more... thus causing a smaller gap and an increased likelihood of a fork hit as compared to clamping the fork for a perfect perpendicular draw.
> 
> One thing I might suggest though is, having the release mechanism be adjustable so that it matches the angle of most people's release... what I mean is, is it should be able to release in the vertical, horizontal and or diagonal plane.
> 
> Anyway, it's an interesting device Charles and I'm sure with a creative mind such as yours you'll find all sorts of things to check out!


You are absolutely right about twisting the forks, leading to a closing of the gap, and that leading to a fork hit. I discussed the problem of twisting the forks in my first video on fork hits. Here I was just trying to isolate the pure effect of the uneven bands. Uneven bands alone probably will not cause fork hits, but as you correctly point out, twisting the fork AND having uneven bands might well produce disaster.

I have given some thought to the angle of the release relative to the angle of the fork. On my rig, it is easier to alter the angle of the fork rather than the angle of the release. The relative effect will be the same, and I will be doing that shortly.

Cheers ...... Charles


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## Charles (Aug 26, 2010)

SuperMonkeySlinger said:


> Great test Charles! I appreciate it.
> 
> Also happy to see that your still having fun with those office bands! Atleast those bands look like #105's.
> 
> SMS


Those are Sparco 107s ... mentioned it in the video but did not emphasize it, as the result did not depend on the bands.

Cheers ..... Charles


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## SuperMonkeySlinger (Jan 28, 2013)

Oh, Sorry Charles the sound on my Computer is not working. At this moment i just have to hear with my eyes.

SMS


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## Oldkid (Jun 12, 2013)

Thanks Charles for this and all the videos you post. They are extremely helpful.

Thanks, Richard


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## AnTrAxX (Jul 18, 2012)

Cool Video. Thanks for your work!


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## jazz (May 15, 2012)

Hi Charles,

very interesting info, thanks.

I would like to know how the unevenness of the bands (in your case 6 and 7 inc) affected the accuracy, that is, has it deviated from a intended path towards the target significantly - and how much?

thanks,

jazz


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## stej (Jan 16, 2013)

jazz said:


> Hi Charles,
> 
> very interesting info, thanks.
> 
> ...


I remember (hopefully correctly) that you tried to point out that when one band is 1mm wider than the other then it makes a big difference in total band surface and that it might affect accuracy.

It would be interesting to somehow measure whether really the 1mm difference (or 2mm) is really important or not.


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## Charles (Aug 26, 2010)

jazz said:


> Hi Charles,
> 
> very interesting info, thanks.
> 
> ...


With a target 8 feet away, the shot went wide by 1.5 inches. From those results, it is easy to calculate using similar triangles that at 10 meters, your shot would be wide by a bit over 4.5 inches.

Cheers ..... Charles


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## Charles (Aug 26, 2010)

stej said:


> jazz said:
> 
> 
> > Hi Charles,
> ...


Yet one more thing to investigate!

Cheers ..... Charles


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## Dr J (Apr 22, 2013)

VII (very important information) Master Charles. Thanks for your continued contribution to the forum. I know that I appreciate it very much and would never take it for granted


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## reset (Apr 13, 2013)

Yes thanks for all the interesting info Charles. Much appreciated.


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## All Buns Glazing (Apr 22, 2012)

Man, I'd love to have a shot with that rig!


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## Charles (Aug 26, 2010)

All Buns Glazing said:


> Man, I'd love to have a shot with that rig!


No problem, Buns! Just come for a visit to Victoria ... or make one yourself. As you can see, mine is put together from scrap materials. As I said, it is easier to build one of these rigs than to make a fancy laminated frame.

I need to figure out how to make one pocketable .... :rofl:

Cheers ....... Charles


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## trobbie66 (May 13, 2012)

Love all the info you are getting from your rig. Looking forward to more vids!


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## Dayhiker (Mar 13, 2010)

Charles, I just had the experience of messing up on cutting myself a bandset from TBG. Simple straight 3/4-inch set. On one of the bands, the rubber sneaked under the straightedge as I rolled by with the rotary cutter and made for a band that was fat then skinny for most of its length and then fat again at the end. I was really noticeable.

Thinking of your experiments and Bill Hays' comments about the shooter being able to compensate for differences in band strength, I decided to do my own experiential testing (i.e. using only my own body's feedback system as the test instrument). After 2 or 3 shots going to one side, I compensated at first by just adjusting my aim. But soon I started hitting where I aimed instead of hitting the target.

Hmmm... So I carefully aimed right at the target again (I aim only by concentrating on the target, focusing my eyes and letting my body adjust to the information.) and started hitting at my usual rate of accuracy. But I paid attention to what was going on with my body and it seems that as I concentrated on focus, I was feeling the balance between the bands in a very delicate way -- far more subtlety than I could do consciously, but detectable if I really paid attention to my hand. After a while I was shooting this set of bands as well as any other.

I feel this is important in that it goes to show that good shooting technique can overcome pretty glaring imperfections in rubber. It seems to me that if I were to try and shoot like a machine as some shooters do, I would have stayed aiming to one side and had success. This shows the difference in shooting technique. Whereas I don't use any part of the fork to aim, and just go by feel in gripping my forks, my muscles do the compensating, kind of automatically, but it does require some deliberate focus.

I don't know if any of this matters. :iono:


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## Charles (Aug 26, 2010)

Hey there DH. Thanks for this input. I think that after a bit of experience, we all learn to subtly compensate in the way you describe ... but as you say, it does require focus. I reported that in my experience, I must recalibrate my aiming technique every time I change the bands, and I am sure many find the same.

My goal in this little test was to see if the unevenness in the bands would result in a fork hit, and it seems that was not the case. I was not attempting to assess accuracy, although it is fairly clear from my limited test that the deflection of the ammo was quite consistent ... meaning that one can compensate for the deflection and still be accurate.

Cheers ..... Charles


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## trobbie66 (May 13, 2012)

Charles said:


> Hey there DH. Thanks for this input. I think that after a bit of experience, we all learn to subtly compensate in the way you describe ... but as you say, it does require focus. I reported that in my experience, I must recalibrate my aiming technique every time I change the bands, and I am sure many find the same.
> 
> My goal in this little test was to see if the unevenness in the bands would result in a fork hit, and it seems that was not the case. I was not attempting to assess accuracy, although it is fairly clear from my limited test that the deflection of the ammo was quite consistent ... meaning that one can compensate for the deflection and still be accurate.
> 
> Cheers ..... Charles Hey Charles I thnik that it doesn't matter how y You are giving a definitive measure hold the catty. intuitive response to your draw cant be measured.


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## Dayhiker (Mar 13, 2010)

I think that if you keep watching dgui's videos it starts to seem as if only the shooter matters. No ammo, pouch, fork (or lack thereof) seems to change the situation. If you really learn to shoot, you can shoot with anything. Even just rubber. No fork. No pouch. Darrell's done it all.


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## Charles (Aug 26, 2010)

Far be it from me to suggest that one cannot learn to shoot with a vast array of equipment, good, bad, and mediocre. All I was trying to do is to isolate various factors that folks seem to think result in fork hits. Uneven band length and uneven band width do not.

Cheers .... Charles


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## Dayhiker (Mar 13, 2010)

Of course! I like what you're doing, Charles. Don't mean to rain on your parade. Most of us can't do what Darrell does so we need all the knowledge we can get.


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## Charles (Aug 26, 2010)

No offense taken at all. Just some folks seem to think I was trying to do something that I did not intend.

Cheers .... Charles


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## Dayhiker (Mar 13, 2010)

Hey Charles, this may be silly, but in light of my post (above) about one band being thinner than the other, I wonder, if you were to equalize for total surface area, if the effect of a thinner band would differ from the effect of a shorter band? Probably not, but who knows? :iono:


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## Charles (Aug 26, 2010)

Well, a narrower band does not have as much deflection as a shorter band, and I believe the reasons are as described here:

http://slingshotforum.com/topic/24759-the-effect-of-uneven-band-width/?p=311120

I suspect that the thinner band would act much like the narrower band, and the deflection would not be as much as you would get with a shorter band.

One might test it by beginning with two doubled bands and making test shots. Then remove one band from one side and make experimental shots. But that would not really capture the case you are asking about ... because the surface areas would not be the same. However, I see no other viable way to test it ... splitting a band along its thinnest dimension is not something I am capable of!!!

Cheers ...... Charles


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## Dayhiker (Mar 13, 2010)

Ah! I *meant *a narrower band, not a thinner one. If one band in a set is narrower than the other but has the same surface area as if it were one inch shorter, would the result be the same as in your experiment?


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## Charles (Aug 26, 2010)

I did do the narrower band test:

http://slingshotforum.com/topic/24759-the-effect-of-uneven-band-width/

In that test, I cut 1/8 of an inch off of a band that was originally 5/8 of an inch wide. Let me ignore the thickness of the bands here.

1. surface area of narrow band = 4/8 x 7 x 2 = 7 square inches

2. surface area of standard band = 5/8 x 7 x 2 = 8.75 square inches

3. surface area of short band = 5/8 x 6 x 2 = 7.5 square inches

When 1 was paired with 2, the ammo was deflected a bit, but only a bit, toward the side of 2, the band with larger surface area.

When 3 was paired with 2, the ammo was deflected a lot, toward the side of 3, the band with less surface area. For 1 and 2 to have the same surface area, I would have had to trim 1/28 of an inch less. When paired with 2, the deflection would have been even less than I found.

In short, the general conclusion would be the same: differences in the width of the bands produce much smaller deviations in the path of the ammo than do differences in the length of the bands.

I hope this is what you are asking. If I have not understood your question, just poke me again. :stickpoke: :thumbsup:

Cheers .... Charles


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## Dayhiker (Mar 13, 2010)

No, that's it! Thanks, Charles. It's funny, that. But it's what I suspected from experience. Keep going, you mad scientist!


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## hickymick (Feb 23, 2011)

I Have not been on here for a while .. How I have mist the common sense that these blokes on here give out .. strange the self proclaimed experts from uk dont come on here and read all this free info ... I am sick to death of reading how great this Rolyan tubing is in uk, sales name Dub Dub .. :what: while I understand this thread is about size of elastics to % of fork hits and other theories .. I would like to know what your views are on this stuff Rolyan As I tried the orange I thought it was :stupidcomp: faulty snapping after maybe 20 shots .I wonder If any of you on here could work out they strengths and weaknesses of this against other elastics.. Loved the tests and info you give out /Charles,, I still cant work out out to do a catty video once I do I am sure I will win me some comps on here :violin:


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## Charles (Aug 26, 2010)

hickymick said:


> I Have not been on here for a while .. How I have mist the common sense that these blokes on here give out .. strange the self proclaimed experts from uk dont come on here and read all this free info ... I am sick to death of reading how great this Rolyan tubing is in uk, sales name Dub Dub .. :what: while I understand this thread is about size of elastics to % of fork hits and other theories .. I would like to know what your views are on this stuff Rolyan As I tried the orange I thought it was :stupidcomp: faulty snapping after maybe 20 shots .I wonder If any of you on here could work out they strengths and weaknesses of this against other elastics.. Loved the tests and info you give out /Charles,, I still cant work out out to do a catty video once I do I am sure I will win me some comps on here :violin:


Sorry ... I have no information about Dub Dub tubing. I do not have any, and so cannot test it.

Cheers ..... Charles


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## All Buns Glazing (Apr 22, 2012)

Hi Hicky Mick,

Do a search for that information, and if you can't find what you're looking for, ask the question here: http://slingshotforum.com/forum/93-slingshot-bands-and-tubes/

My search found this: http://slingshotforum.com/topic/20554-elastic-test-results-compiled/?hl=dubdub



hickymick said:


> I Have not been on here for a while .. How I have mist the common sense that these blokes on here give out .. strange the self proclaimed experts from uk dont come on here and read all this free info ... I am sick to death of reading how great this Rolyan tubing is in uk, sales name Dub Dub .. :what: while I understand this thread is about size of elastics to % of fork hits and other theories .. I would like to know what your views are on this stuff Rolyan As I tried the orange I thought it was :stupidcomp: faulty snapping after maybe 20 shots .I wonder If any of you on here could work out they strengths and weaknesses of this against other elastics.. Loved the tests and info you give out /Charles,, I still cant work out out to do a catty video once I do I am sure I will win me some comps on here :violin:


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## mopper (Nov 17, 2012)

My own experience confirms those findings ... I actually shot a slingshot with such uneven bands because I had forgotten that I had already shortened one of the bands before attaching it. I thought what the heck I am not gong to do it all over again and shot it - no fork hits.

On the other hand I have just tried out a new release technique (full butterfly with the thumb and forefinger holding the pouch "sideways" at a 90°angle, not letting the pouch slip out "forward" towards the fingertips. It looks similar to what Bill Hays shows in his video on why he gets more speed out of his bands than other people) and I had several times more fork hits this afternoon than in all the tens of thousands of shots that I fired before changing my technique combined.

The more I shoot the more I am convinced that as long fork width and ammo size are within reasonable limits it is faulty release technique that is responsible for at least the vast majority of fork hits, if not all of them.


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## Charles (Aug 26, 2010)

mopper said:


> My own experience confirms those findings ... I actually shot a slingshot with such uneven bands because I had forgotten that I had already shortened one of the bands before attaching it. I thought what the heck I am not gong to do it all over again and shot it - no fork hits.
> 
> On the other hand I have just tried out a new release technique (full butterfly with the thumb and forefinger holding the pouch "sideways" at a 90°angle, not letting the pouch slip out "forward" towards the fingertips. It looks similar to what Bill Hays shows in his video on why he gets more speed out of his bands than other people) and I had several times more fork hits this afternoon than in all the tens of thousands of shots that I fired before changing my technique combined.
> 
> The more I shoot the more I am convinced that as long fork width and ammo size are within reasonable limits it is faulty release technique that is responsible for at least the vast majority of fork hits, if not all of them.


Thanks for you first hand report!

Cheers .... Charles


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## KyleReynolds (Jul 21, 2013)

Wow nice setup! I'm surprised there wasn't anymore deviation in between the shots. I would recommend doing another test, this time testing the affects of one of the bands being stronger than the other. Perhaps double bands on one side and a single band on the other?


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## Charles (Aug 26, 2010)

KyleReynolds said:


> Wow nice setup! I'm surprised there wasn't anymore deviation in between the shots. I would recommend doing another test, this time testing the affects of one of the bands being stronger than the other. Perhaps double bands on one side and a single band on the other?


That is effectively what happens when one band is shorter than another ... the shorter band turns out to be stronger than the other.

In this test, I was examining the effect of uneven band length on the possibility of fork hits. Of course if I doubled one band, there would be even greater deviation in the path of the ammo ... and perhaps one might be able to produce enough deviation to get a fork hit. But I do not really see the practical application of such a test. I doubt than anyone would mistakenly put two bands on one side but only one band on the other side.

I have also tested what happens when bands are uneven in width.

http://slingshotforum.com/videos/view-47-the-effect-of-uneven-band-width/

Again, that makes one band stronger than the other. But the deviation in the path of the ammo is not nearly as great as when one band is shorter than the other.

Cheers ......Charles


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## ash (Apr 23, 2013)

I just thought of something, Charles. In your tests the pouch is being held firmly in line with the forks by your rig. In a real human shooting situation, the lateral position of the pouch relative to the forks will more than likely be influenced by the differing tension from one band to the other.

Perhaps another test can be done whereby the fork it located an inch or two off the axis of the rig... such that the tension of the stronger and weaker band is closer to equal.

Will the ammo fly along the axis of the rig (possibly hitting a fork), along a straight line from release to the centreline of the forks or some other trajectory?


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## Charles (Aug 26, 2010)

The sort of test you suggest is not that easy to arrange, because of the difficulty of measuring the tension in the individual bands when attached to the fork and the pouch. It is probably easier to attack the question analytically. Measure the draw weight of each band at a number of elongations (stress strain curve for each). Then use elementary trig to determine what offset is needed so that the two bands would have equal tension at some specified draw length. Then just look at the resultant vector of the force vectors of the two bands.

Intuitively, I seriously doubt that anyone would be offsetting their draw to any significant degree. To see what I mean, just set up a couple of bands on a frame, one stronger than the other, and attach a pouch. Then put a ball in the pouch and draw it. I have done essentially this when shooting with office rubber bands when one of the rubber bands on one side lets go. I did not find any tendency to offset the forks. I think the greater tendency might be to twist the fork in response to the uneven pressure on the fork tips, and of course that might well result in a fork hit because of the narrowing of the gap between the tips as a result of the twist.

Cheers ....... Charles


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## ash (Apr 23, 2013)

I don't think any tension measurement, calculation or analysis would be required. I would just offset the forks by something like 1/4" at a time until either the alignment because ridiculous/unrealistic/impractical or a significant effect was observed. You may only have to do four or five shots.

One thing that I think will be interesting or apparent is that with the pouch gripper remaining on the same axis, but the forks moving laterally, any offset also introduces a certain amount of tweak (relative to the forks) that is (possibly) going to accentuate the error in trajectory.


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## Charles (Aug 26, 2010)

Offsetting the forks a bit at a time is of course not difficult to do, not worrying about the tension in the bands. Offsetting the forks will automatically induce unequal tension if the bands are initially equal. Except for the slight "tweak" and resulting speed bump effect, the geometry is almost the same as twisting the forks ... that is, the gap available for the ammo will narrow. It is easy to see that, by just considering the extreme case of the forks offset by, say several feet. With enough offset, you will certainly get a fork hit.

Cheers ...... Charles


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## lightgeoduck (Apr 3, 2011)

That is a cool set up Chuck. I think with a few modifications you can simulate some more factors of shooting and get closer results, though it still won't be the same as doing it by hand.

Things you may want to consider for mechanical testing.

1. Set up where the forks pivot at the base. This will simulate (sort of) how the different tension of the bands would change how some would end up holding the slingshot at draw

2. Set up the forks to shift left or right , referencing the same point of the fork to target. This should (sort of) simulate a shooter keeping the same form not knowing the changes caused by uneven bands.

Another thing that might aid this is to attach a spring or soft cushion in front or back of the forks to sinful ate the pressure of ones grib.

With that being said, like others already mentioned, it all boils down to technique of the shooter that would determine if an inaccurate band set would cause a fork hit. An experienced shooter, whether fork referencing to target or not, will always compensate to hit the target. I know this for a fact, just from personal experience of shooting. I am a haphazard band set maker, meaning sometimes they come out good and other times not so good . I haven't (fortunately) had a fork hit, and after a few shots or so find the spot that will allow me to hit the target.. What I did find, is that it seems the pouch release is the culprit for most hazards... I find this happening to me after shooting for extensive periods of time. Also, tight slingshot grippers have more room for error than relaxed.

I guess, after all of that, it might just be best for you to set fear aside ( taking safety precautions of course ) Is to set the mechanism aside and do some personal trial and error, trying to accomplish what you are trying to prevent... Then take note as to what caused it... That's how I go about tackling something in this hobby/sport when I am trying to help someone tat is having issues that they need assistance in solving. Now don't get me wrong, what you did and are doing does help eliminate something in one way shape or form... All pieces of a puzzle are need for a picture to be made.

LGD

*annotated one finger tap on the ipad at a time


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## jazz (May 15, 2012)

Charles said:


> In short, the general conclusion would be the same: differences in the width of the bands produce much smaller deviations in the path of the ammo than do differences in the length of the bands.


Hi Charles, hi all,

I tried to figure out why this is so.

Is it because making bands narrower diminishes the power (and vice versa) in a very strict proportion: 10% wider bands (for example) should yield 10% more power; 10% narrower bands should yield 10% less power while in the same time shortening the bands for 10% (say from 20 to 18 cm) FOR A SAME STRETCH, say, 20 active length stretched to 80 cm = 400% gives somewhat more power than 10% as in the first case with narrower bands?

For example, if a 20 cm band is stretched to 80 cm than it is 400% total elongation, while 18 cm stretched to the same 80 cm is 444% total elongation, and if mathematicaly allowed, than 444/400 = +11%.

First I would like to know if this one percent is correct and if yes is it realy significant enough to "produce" significant deviations, as your experimetns evidened?

Cheers,

jazz


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## jazz (May 15, 2012)

Hi Charles, hi all,

Last sentence in my comment above should read: "First I would like to know if this one percent is correct and if yes is it realy significant enough to "produce" significant deviations, as your experimetns evidenced or there is some other influential factor on top of the first one?"

cheers,

jazz


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## Craig Lockwood (Oct 29, 2013)

Charles:

Nicely documented.

CL


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## Charles (Aug 26, 2010)

Craig Lockwood said:


> Charles:
> 
> Nicely documented.
> 
> CL


Thanks, CL!

Cheers ..... Charles


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## Lug (Nov 12, 2013)

Helpful bit o' slingshot science and something I have been wondering about. Thank you!

Reminds me of the old story about medieval philosophers theorizing and arguing for hours about how many teeth in the mouth of a horse and finally someone wiser (a servant) goes out to the corral and counts how many teeth.


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