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  1. #1
    Join Date
    May 2015
    Location
    Fairfield, Victoria
    Posts
    2

    Default Cross ? grained eucalypt

    I have just come across a specimen of Blue Gum (Eucalyptus Saligna) which has grain running at different angles in adjacent rings. The angle between rings is of the order of thirty degrees. It appears to have spiral grain running one way for a few years (3 or 4 millimetres of growth) and then running the other way for the next period. And then back to the original direction, and so on... It splits easily (with an axe) along the rings but splitting it across the rings is very hard. And if you know how tough Australian hardwood is under usual circumstances and then think of something that takes at least three times as much effort to split you have some idea of how tough this stuff is. It is like trying to chop a piece of plywood 150mm thick. This is firewood, not timber for woodwork, sorry. And it has been eaten out by termites in the middle of the trunk. This tree has been dead for ten or more years, possibly decades. The other notable thing about it is that is doesn't burn as well as the straight grained variety. I had a slightly embarrassing time with a bbq on Saturday.
    Does anyone out there know why trees grow this way? And why is it not so burnable?
    Cheers
    Ian

    The wood in question is at a weekender property so I can't get pictures until next weekend. I will do my best, but then I am OS for about three weeks so...

  2. #2
    Join Date
    Jun 2015
    Location
    Wolvi
    Posts
    193

    Default

    It splits easily (with an axe) along the rings
    That type of split is very common among Eucalyptus and Corymbia. For those that don't know it's the really old method of making timber roof shingles. Often times you don't even have to have much penetration, nor even much pressure, of the axe as the shingle has a tendency to jump off the log.

  3. #3
    Join Date
    Mar 2004
    Location
    Brisbane (western suburbs)
    Age
    73
    Posts
    9,069

    Default

    The description sounds like what is called "rowed" grain, which is very common in some Eucalypts. E. tereticornis around here typically has that sort of pattern, which, added to its hardness & gummy nature makes it a pig of a wood to hand plane (or plane with a machine).

    I've never come across an explanation of how a tree manages to instruct its cells to grow like that, but I presume it's come about as a result of natural selection for trees that survive high winds & twisting.
    Cheers,
    IW

  4. #4
    Join Date
    May 2015
    Location
    Fairfield, Victoria
    Posts
    2

    Default

    So now I've managed some images.Image-1.jpegImage-2.jpeg
    These are the front and back of the same piece of wood. It is about 75mm thick.
    I am not sure how many changes of grain direction are in between these two.
    I exaggerated when I said thirty degrees, this looks more like twenty.
    And I think I know why it burns slowly. The termite galleries (dark diagonal line in image), and the nest itself, allow water to accumulate inside the tree and soak into the wood. Even though the tree has been dead for years it is still damp.
    Now that it is cut up and stacked under cover it should be good in a year or so.
    Cheers
    Ian

  5. #5
    Join Date
    Apr 2005
    Location
    Nerang Queensland
    Age
    62
    Posts
    10,621

    Default

    Lightning strike can twist the grain
    Neil
    ____________________________________________
    Every day presents an opportunity to learn something new

  6. #6
    Join Date
    Apr 2015
    Location
    Warragul Vic
    Posts
    930

    Default

    Here is an example of a cross-grained eucalypt (a box) which shows a very old weathered log, but a good example of how such cross grain grows in alternating directions in some eucalypts. This results in an "interesting" figure making such woods very hard to split eg for firewood.
    This pic was published in World of Wood (IWCS) some years ago.

    Cross grain.jpg

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