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  • shinai hairline cracks

    hi folks,
    i bought the "musim" shinai from kendoshop 2 or 3 weeks ago - now it shows hairline cracks on the inside as pictured in the attachment.
    i sanded it and oiled it with a cloth wrapped around, which i dipped in raw linseed oil before. the cracks did not show before i oiled it - maybe they were made visible through the oiling process.

    my questions are now: can i still use this shinai safely for practise? and where do these cracks come from?

    thanks!

  • #2
    I had those when I got a shinai from my dojo, I also had an H shaped crack on the surface of the outside. It seems to be okay (mine atleast), even with beginners pounding on it(im a beginner too, and I've done my fair share of pounds). I could probably sand off the surface crack.

    I don't know what to say about those things though.

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    • #3
      I've seen such things before on my own shinai's. None of them have ever broken. I'd say you are probably ok.

      Brian

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      • #4
        Originally posted by moetl
        hi folks,

        my questions are now: can i still use this shinai safely for practise? and where do these cracks come from?

        thanks!
        they might come from these little beetles that eat bamboo.......
        this happened to me 2 weeks ago......
        try if white powder comes out of the shinai......as for the use:
        I don't see why you shouldn't still use it.....

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        • #5
          Originally posted by Zaphiel
          they might come from these little beetles that eat bamboo.......
          LOL, i don't think there are little bamboo eating beetles living in my shinai

          sorry, couldn't restist - it just sounded too funny. i know that these varmints exist

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          • #6
            Exactly, mine appeared in the winter, and I live in canada, and it was reaching -30 this winter. Couldn't have been beatles.

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            • #7
              just an idea........sorry

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              • #8
                i use only musim shinais last 2 year - this lines are from oiling bamboo and they are not cracks - its just some lines.

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                • #9
                  zaphiel, i meant no harm. no need to say sorry

                  streetcleaner, i think this are cracks, because the lines do not only appear on the surface, but also go deep - about half a millimeter.

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                  • #10
                    where are the cracks? under the tsukagawa or on the daitotsubu?

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                    • #11
                      the cracks are erratically distributed in a few "bundles" on the inner part of the shinai, exept were the tsukagawa is. additionally there are some cracks at the joints.

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                      • #12
                        I have viewed these cracks under a high powered microscope and found that they do not impare the structural integrity of the bamboo what so ever.

                        A good coat of oil would do.

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                        • #13
                          you actually DID that? :S:S:S

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                          • #14
                            most impressive,

                            Originally posted by Marine_Boy
                            I have viewed these cracks under a high powered microscope and found that they do not impare the structural integrity of the bamboo what so ever.

                            A good coat of oil would do.
                            you have my applause. .. ...<clap, clap, clap, clap>

                            Comment


                            • #15
                              Originally posted by moetl
                              hi folks,
                              i bought the "musim" shinai from kendoshop 2 or 3 weeks ago - now it shows hairline cracks on the inside as pictured in the attachment.
                              i sanded it and oiled it with a cloth wrapped around, which i dipped in raw linseed oil before. the cracks did not show before i oiled it - maybe they were made visible through the oiling process.

                              my questions are now: can i still use this shinai safely for practise? and where do these cracks come from?

                              thanks!
                              (rolling up sleeves and trying to utilize engineering know-how..)

                              You should still be able to use the shinai. The bamboo's strength is greatest if stressed in the "fiber direction". I don't want to go too much in to engineering principles, but the cracks in the shinai (in your case) are usually caused by high axial stresses in areas where there are no fibers (ie no "inner support"). Why do you think that every time we hit men or kote that the shinai never breaks? The forces on the shinai are pretty much perpendicular to the surface of the shinai everytime the shinai impacts something and the resulting stresses are always put on the fibers.

                              You will have a problem if the shinai is "split". I never use a shinai that is split in half. The split crack is along the direction of the fibers and therefore will propogate each time you give the shinai a good, hard whack. Why is that? There are fibers running the length of the shinai, and between, there is usually something filling the void. Some membrane that holds the fibers together. That membrane is very weak when stressed and will fail easier compared to loading the shinai in the previous example. If you load the shinai in that direction, CRACK!!!. Plus, the fibers flake off from thereand is pretty dangerous.

                              my 0.02$(US),
                              Tim
                              Last edited by samurai999; 26th May 2004, 03:17 AM.

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