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Thread: Riving (splitting) to get good aircraft wood

  1. #1

    Join Date
    Jun 2019
    Posts
    12

    Riving (splitting) to get good aircraft wood

    I have been thinking about building for a long time. I even bought a set of Jodel D-18 plans. Douglas fir is the specified wood for this design.

    With regard to getting good wood with appropriate grain properties, what about the idea of selecting pieces of Douglas fir from the big box home store, and then to get the appropriate grain properties, such as runout, vertical grain, etc., take larger pieces like 2/4 and 2/6, and rive smaller pieces of out of those larger pieces.

    It seems to me that by appropriate orientation of the froe (or whatever splitting device is used) one could produce long pieces with the right sort of grain properties.

    Of course after being riven the wood would need to be shaped using spokeshaves, planes, or whatever tools so it has the appropriate size and shape, such as rectangular, tapered, etc.

    One would have to select pieces at the store that have a tight enough grain and straight enough grain to start with, but it seems like that should be a manageable problem. There is also the issue of getting sufficient density. However, because lumber dimensions are standardized, weighing the pieces and applying a little math should allow one to determine density. The light pieces could then be returned to the store without being split.

    There would be a fair amount of wasted wood using this process, but the wood would be easily available and not very expensive. Also, it seems to me that the wood obtained using this method could actually be better than sawn wood that you might buy from an aircraft wood supplier because, for example, the grain would have no runout over the length of the piece, and by choosing the angle of the splitting tool the grain could be virtually perfectly vertical.

    This would probably mostly apply to the problem of getting wood for longerons and stringers. This might not work as well for getting wood for making spars or other pieces of larger dimensions, but for that purpose what about using LVL lumber and cutting it to the appropriate dimensions? Generally speaking, LVL has better strength and uniformity than raw lumber of the same species, partly because the individual sheets that make up the LVL are graded and selected before being glued up into billets.

    What do you think?

  2. #2

    Join Date
    Oct 2011
    Posts
    41
    Riving seems like overkill especially for small pieces. I think the strength comes from the structure (eg: ribs) more then individual pieces. The wings on my project are wood. I used conventional methods to build them; wood spars, ribs, bows and plywood leading edges. They also are Sitka Spruce vs fir. Less strength but also less weight.

    LVL looks promising for spars though. The biggest downfall of laminating is the weight of the glue. Kind of like fiberglass. High resin content makes for a heavy piece. Using vacuum bagging to keep the ratio of resin to cloth minimized helps keep the weigh down. It would be interesting to see a strength, weight and cost comparison for spars. LVL vs conventional solid wood.

    If you do go ahead with your project keep us updated on your materials and techniques.

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