Multiplex / Plywood break

Discussion in 'General Slingshot Discussions' started by noah013, Dec 21, 2013.

  1. noah013

    noah013 Member

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    Hi,

    I've got myself a big nice piece of multiplex also known as plywood, a few months ago. I've cut a few slings out of it. They are all from the same design: the Dragon by Hrawk. It is a very nice design btw. But here is my problem: after reading about the risk of slings I decided to try to break my slingshots by hand to test their safety. 2 of the multiplex one's broke! I was surprised cause I thought it isn't that easy to break multiplex with bare hands and I've put a lot of time in them. My question is: Is it normal for multiplex to be broken by bare hands? (When I was trying to break them I heard some crackling sounds and then one of the forks broke right of). And what can I do to prevent something like this happen cause the other slingshot cut out of multiplex didn't break.

    Thanks, Noah013
     
  2. BeMahoney

    BeMahoney Builder of things

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    Hey Noah,

    can you post any pics?
    Any "blind" comment is
    frivolous..

    Greetings,

    Be
     

  3. noah013

    noah013 Member

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    Here are some pics:
     

    Attached Files:

  4. 4foruglenncoco

    4foruglenncoco Member

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    That actually is not multiplex, multiplex should have 13 plys, get baltic birch 3/4 inch with 13 plys/12plys
     
  5. Achso_42

    Achso_42 Senior Member

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    Correct, multiplex has more layers.
    A good source for multiplex are DIY-stores, I saw a 20*40cm piece for 2€ today.
     
  6. JoergS

    JoergS Administrator

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    You need to look for marine or furniture grade birch or beech plywood. The stuff you used is construction stuff. No wonder it broke so easily. Very few layers, cheap wood most likely. No wonder it broke.

    Multiplex is just a brand name, don't be confused.
     
  7. BeMahoney

    BeMahoney Builder of things

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    Multiplex

    Hey Noah,

    All those boards are "Plywood"- different layers of rotary veneer
    glued to another using a press, grain rotated by 90°.
    So if you make piles of plywood by stacking pieces,
    every second one should be turned by 90°, due to the cover
    layer meeting another layer of the same direction otherwise..

    As far as I´m used to it, the good stuff is made of baltic birch layers
    with a thickness of around 1.4mm each (there´s plane plywood,
    1mm thick, consisting of three layers, rather expensive, redish glue)
    glued together with that redish glue.

    What you used is "box plywood" to me: brownish glue, rather cheap
    lighter pinewood, layers up to 3mm thick. - Used to make boxes for
    shipping stuff..

    Concerning the "real" multiplex, the percentage of glue and strength
    of the wood is way higher!

    Maybe googling "baltic birch plywood" helps to find a good source?

    Greetings,

    Be
     
  8. 4foruglenncoco

    4foruglenncoco Member

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    Also I noticed u made the slingshot against the grain, u want it with it, so the one u made, the grain is horizontal while the grain should be vertical
     
  9. noah013

    noah013 Member

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    So I've been to my local DIY store and found this
     

    Attached Files:

  10. noah013

    noah013 Member

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    It is birch multiplex with 13 layers, is this good for making slings?
     
  11. VWscooby

    VWscooby Senior Member

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    Pretty much perfect!
     
  12. Achso_42

    Achso_42 Senior Member

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    Go and make some slingshots!
     
  13. ColtSmith

    ColtSmith New Member

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    Good thing it didnt brake while you were shooting it