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Thread: The Science of Shooting String

  1. #1 The Science of Shooting String 
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    Firstly, hi. I've joined up to ask a question that is probably going to cause a lot of laughter and mockery - not usually a good first post on any forum!

    The question is about shooting string attached to weights with an air rifle. The application is to win high value prizes at a fair.

    I already won an iPad and, as I'm a pretty good shot, thought I'd be able to get a MacBook Pro for much less than its worth in the shops. I was wrong and have, despite being a generally sensible type, have ended up in a bit of a gambler's dilemma where to pull out guarantees a loss but to carry on might at least recoup my losses.

    The idea is that you have boxes with pictures of various electronic toys that contain lead weights attached to a piece of string. If you manage to break the string, you win the item pictured on the box.

    The boxes are hanging from a rail and resting against a hard surface - although this means that you're hitting the string at an angle, reducing the impact of any hits, it at least means that the box isn't moved when the string is hit. The firing position is fairly low-ish relative to the string.

    The stall holder claims the string is made of cotton but I'm fairly sure that it's some sort of synthetic mix, let's say nylon. I have a sample of the string I broke for the iPad at home and will try a few tests later.

    The pellets are standard lead 0.177 air rifle pellets - obviously very soft but still capable of doing damage to metal or flesh at close range.

    The firing position is perhaps 1.25 metres from the string, with the barrel perhaps 0.75 metres from the string - so nearly point blank range. Close enough to kill a person if you hit them in the right place.

    I have hit the string for the MacBook hundreds of times (the stallholder keeps the string back for you when you return and yes, mine is the same piece of string as I have photographed it). Many of the hits were probably not completely direct - these often bounce back at me - but most were quite severe and often caused fibres to noticeably break. The string is seriously damaged but the core fibres are intact and seem to refuse to break - even direct hits are having no apparent effect now. I'm fairly sure there's no foul play going on with regards to the material as the authorities here would be unlikely to tolerate it, and the guy returns year after year.

    Looking at the other strings that have broken, including mine, there seems to be a high degree of luck as to whether the string breaks or not - some strings appear to have far fewer damaged fibres around the break point than mine.

    This indicates to me that I need to create a weak point in one area - hitting above or below that point will waste shots on fibres that already have a break in them. But I've been doing exactly that and I don't understand why the string is still intact. As said, I don't think the game is set up, but I do think it's very cleverly arranged to make it look much easier than it really is.

    Sorry for the long post, I think I've covered most of the facts!

    Finally, please, no telling me what an idiot I am. I am furious with myself enough as it is and I really am not normally this stupid. I just want to understand the process here.


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  3. #2  
    Universal Mind John Galt's Avatar
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    Quit while you are behind. :wink:


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  4. #3  
    Forum Bachelors Degree x(x-y)'s Avatar
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    How thick is the string? And how fast do the pellets 'fly' when shot?

    This is assuming you get more than one shot:

    Perhaps you need to fire at one side of the string making sure some of the fibres have broken, then fire at pretty much exactly the same position (symettrically) on the other side- which would leave a very thin strand of string that could break easily.

    I'm not sure really, hope it helps though!
    "Nature doesn't care what we call it, she just does it anyway" - R. Feynman
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  5. #4  
    Forum Ph.D.
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    Easy to tell cotton from nylon or polymer- light it cotton will just burn and has the smell of a burnt cotton rag. Nylon will melt and then burn making a gooey mees and smell like burnt hair.
    how many shots??
    how thick?
    howmany strands?
    and yes it's harder than it looks
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