Thursday, August 16, 2012

Watermelon Woman - why she failed

The watermelon fail video, published by the CBS show "Amazing Race", has received over 4 million views by now, and counting.








It has a rather negative effect on the slingshot hobby, as many people are now afraid of returning balls.

I have looked at the video another time and found that the pouch design and - mostly - the grip technique the poor woman used were the cause for the epic fail.

Returning ammo is - from my point of view - always caused by a twisting pouch. These twists can have several reasons, and a shooter is well advised to avoid all of them.

a) Bad pouch design, with basket or bowl shaped pouches
b) Bad rubber/pouch attachments, using attachment points at the pouch corners rather than in the middle
c) A release technique that releases the upper or lower side of the pouch first

The (still) biggest forum for slingshots (I no longer use it) recommends a narrow fork, but I disagree - the fork width has no influence on such issues. I have slingshot crossbows that feature 70 cm fork width, and no such issues ever occured. I think this theory is scientifically unproven and more like a superstition than a fact. 

In the case of the watermelon woman, a), b) and c) have caused the fail.

Let us look at the pouch first.

This pouch consists of a piece of raw hide or textile (hard to tell) with eight holes, two in every corner. The thick rubber bands (I estimate 12mm industrial rubber) have been put through the top left/top right holes (upper band) and, respectively, the lower left/lower right hole, with the rubber bands running through on the back side of the pouch. Like this (view of the backside):
This pouch design and band attachment are both rather bad. They create a "tobacco pouch" effect, as the bands will tighten the pouch edges until they touch each other. And they won't open at the end point of the acceleration either.

The band attachment is also very dangerous because it twists the pouch easily. If you pull out slightly off center, the upper and lower bands won't be stretched evenly, and this leads to twisting. Look at the shot, taken right after the release, with the bands still swinging.


 
You can see the twisting - and that was a SUCCESSFULL shot.

She did in fact draw out nicely, for the most part. See her draw before the success shot:

She holds the pouch in the middle, and both bands are evenly stretched. It worked.

Now see how she drew out when the shot failed:

You can clearly see the difference. The upper bands are stretched more than the lower ones, and the melon is totally off center. This no doubts caused the pouch to twist, the melon did not release - but came back at her.

Now let us look at a much better pouch design - employed by my slingshot cannon.

As you can see, it is longer, but narrow. And it has a generous center hole, so the ball will always be in the middle. The bands are centered, too - not much room for twisting. And it works - see the bands after release!






No twisting, just a totally clean release.

If course, it is harder to draw out a pouch like this with your bare hands. A mechanical release makes a lot of sense. Just an upscaled version of this here would do the job just fine:


So - I think I have demystified the video just nicely. I may make a small scale model and record the effects in slow motion, someday soon - it is on my list of future projects.

9 comments:

  1. Thanks, I had often worried about this happening and your research has put me much more at ease, good job!

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  2. POW!!! Right in the Kisser! Great investigation though and a great read!

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  3. Good read. The only question you left unanswered is whether or not Penny served up a SLIPPERY NIPPLE on the Big Bang Theory.

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  4. People should ask the master of slingshots when it comes to public and untrained people using them especially when you can make an epic slingshot cannon

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  5. Jorg, My Son, Josiah 7 and I (Alan) love watching your show. He is always trying to get me to make a sling shot with him. So the other day we went through the woods behind our house and found some cider wood. Could you give or refer us to some advise on how we should process it. Is it even good wood to work with?
    thank you

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  6. ^ you should check our his Forum, you'll probably get a faster response, but from my understanding, if you found dead branches or pre-cut wood, I would not use it. There's no knowing how long it's been there, and if the wood was stored outside, there is a good chance that it has started to rot, and is not safe to use.

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  7. errmmm im pretty sure this watermelon video is completely fake, it was an advertising thing. being hit in the face by a watermelon and that velocity would put you in hospital

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    1. No it wasn't. She actually attempted to file a lawsuit against CBS, but it failed for obvious reasons.

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  8. Who said she didn't go to the hospital?

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