Bamboo Core - What's Wrong With Idea?

Discussion in 'Boat Design' started by James Mills, Jul 5, 2004.

  1. JSL
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    JSL Senior Member

    Interesting idea but don't get bamboozled!
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    I don't know what happens to bamboo when you open the end-grain, whether there is a strong wicking action for water, glue etc.
     
  3. Satsquatch
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    Satsquatch New Member

    Thanks Par
    I understand what you're saying, that if I cannot make a stronger core of the same weight or a lighter core of the same strength then I am working against myself. For strictly performance applications I agree. I do not plan to build a performance boat, not by modern standards at least. I will risk making an *** of myself by presuming you work primarily with performance designs where weight is often more of a concern than strength. Having spent the majority of my maritime career in the sub-arctic waters I am loath to build a boat that cannot be guaranteed to endure the abuse one finds at sea. My first consideration for the hull was steel. for my purpose, weight is considerably less an issue than strength. That said, I would prefer a lighter weight hull so long as I can maintain my standard of strength and durability. I would not be making a solid bamboo laminate, that would nearly as heavy as steel for the same strength. The material I will begin experimenting with would perhaps be more aptly described as a biaxial bamboo reinforced, high and mid- density epoxy foam core with glass and Kevlar inner and outer skins.

    There are those of us who feel that too much emphasis is being placed on building a boat light and not enough consideration taken for the abuse it may endure.
     
  4. rxcomposite
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    rxcomposite Senior Member

    Bamboo is a magnet for termites and wood borers and starts the moment you cut it and place it on the ground. I think it has something to do with the sugar content in the fibers.

    It is not a good core material as the density changes from the inner to outer core. You have to strip away the soft inner part and scrape the green outer part build up.

    By itself, the cylindrical bamboo is of composite construction. Hard outer shell, soft inners, fibers longtitudinaly aligned, and supported at ends with thick nodes I call bulkheads. On a specific strength basis, rattan (another weed variety) beats bamboo hands down with its very tough outer skin and full soft inner core.

    The best use I find for the bamboo is when the skins are stripped into thin sheets and coarsely woven to form a sheet. Great for bulking material. Much cheaper than coremat.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    I am old enough to remember fishing with "Rangoon cane" rods. The de luxe version was the "split cane" rod, which was made from, if I remember correctly, quadrant sectioned lengths glued together. Glass made them all obsolete.
     
  6. PAR
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    PAR Yacht Designer/Builder

    Don't bother with the external Kevlar skin, just a waste of resin and fabric, though as the inner most skin, it will improve puncture resistance considerably, particularly if the cure is fairly thick. I use Xynol as the external most sheathing, to offer abrasion resistance. Of course it's not going to add much to the modulus, but this is what the rest of the laminate is for.
     
  7. Jeremy Harris
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    Jeremy Harris Senior Member

    Interestingly I've just finished (as in a couple of hours ago) laying a few tens of m² of bamboo flooring. The stuff comes as T&G boards, 12mm thick and is incredibly hard and dense.

    As I was cutting and laying the stuff it occurred to me that it should be possible to machine the boards up into strips for a strip planked hull. Not lightweight, that's for sure, but the very hard finish would make for a durable boat. The stuff looks nice too. The flooring I used was this stuff: http://www.bambooflooringcompany.com/solid-natural-strand-woven-bamboo-flooring-wide-board.html

    I'm guessing that there must be a source of the raw (not machined into T&G or lacquered) boards somewhere in the Far East, and if so then getting some machined up into strips with convex/concave edges might well make for a nice material for making a tough, but nice looking, small boat.
     
  8. rxcomposite
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    rxcomposite Senior Member

    Anybody who has the mechanical properties of a bamboo strips?

    All I have found in the net are test results of the whole cylindrical bamboo tested with the nodes on. Claims have been made that its fiber is stronger than steel but until I see the lab test results. hard to believe.
     
  9. rxcomposite
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    rxcomposite Senior Member

    The school where I graduated from in the Philippines claims (or exhibits a prototype) that was made from wood and woven bamboo strips for the skin. It was designed by one of the founding fathers, an aero engineer.
     
  10. portacruise
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    portacruise Senior Member

    There are around 1000 species of bamboo, and it depends on what part you look at, so measurement will vary considerably. Some species do surpass steel and even carbon fiber in tensile strength and sometimes other measurements. There are some good links at previous discussions on this list- search "bamboo" or "bamboo boats". Preservation can be with a procedure done with boric acid, as I recall

    Here's a couple of links:

    http://bambus.rwth-aachen.de/eng/reports/mechanical_properties/referat2.html (comparison 4th heading down)

    http://www.networkearth.org/naturalbuilding/bamboo.html

    PC
     
  11. rxcomposite
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    rxcomposite Senior Member

    Thanks Portacruise.

    The local state university on wood research tell us to immerse the bamboo in water and cleanse it with running water to remove the starch and the sugar content. Boric acid treatment for fire retardancy.
     
  12. Jeremy Harris
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    Jeremy Harris Senior Member

    The bamboo boards are made using some sort of very high pressure press or roller system, I think, where stripped bamboo fibres are reconstituted with some form of waterproof resin into boards.

    The fibres run one way, so the stuff looks, feels and cuts just like very hard and stiff wood. If I had to guess I'd say the boards are much stiffer and stronger longitudinally, but much weaker across the "grain", than the hardest of hardwoods. It's also pretty dense, on a par with something like white oak at a guess.

    It cuts, planes etc like a very, very hard timber, with a nasty twisted grain. It's so hard that it tends to blacken when being power sawn or sanded - cutting and sanding needs to be done slowly to avoid over heating the surface. It tends to split slightly, but not as badly as straight grained timber - you can saw across the "grain" with a table saw and it doesn't tend to break out much, if at all.

    It definitely needs carbide tools to machine it, as it quickly takes the edge off HSS steel tools.

    If I could get a source of bare bamboo planks I'd be tempted to build a strip planked small boat. Coated with epoxy and varnished I reckon it's look as good as a cedar strip built boat, but be far more resistant to knocks and dings.
     
  13. portacruise
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    portacruise Senior Member

    Yes, the second source tells of a similar rinsing procedure and placing the poles in a slanted non-horizontal position to drain and dry more quickly. A solution of 0.3% caustic soda helps with preservation according to that source. Boric acid +borax for insects is mentioned. Plaster for fire retardancy...

    The best bamboo can have strength to weight ratios that at least matches synthetics such as carbon fiber, and can be very low in cost for the raw material compared to the synthetics. It is a fast growing, eco friendly, renewable resource that has been used to build aircraft of various sorts as well as in other unique applications. It has been considered for earthquake resistant small structures because of its considerable flexibility. There are more interesting applications in the second link above.

    I can't say that the information is completely accurate for any sources coming from the internet. But there are many other references/links that indicate support in the same areas.

    PC
     
  14. Emerson White
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    Emerson White Junior Member

    Bamboo flooring and cutting boards are made by taking a stalk of timber bamboo (one of several large species) and cutting or splitting radial strips from it. Those strips are then machined down to make uniformly dimensional stock which is then glued together to form larger pieces. Could these strips (maybe 1/8th ro 3/8ths inch thick and an 1 to 1 and 1/2 inch wide) be used in cold molding?
     

  15. Satsquatch
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    Satsquatch New Member

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