Aluminum Sharpie outrigger canoe

Discussion in 'Boat Design' started by sidetrack, May 28, 2013.

  1. sidetrack
    Joined: May 2013
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    sidetrack Junior Member

    Hey everyone,

    First time here on the forum.

    I'm looking seriously at putting together an outrigger/proa very similar to Gary Dierking's 24ft Wa'apa but with slightly more flare and without out a lot of the permanent deck structure and I'd like to investigate an aluminum hull. The goal is to get the three hull sections to nest.

    Could anyone point me in the right direction to calculate what kind of thickness I'm going to need for the aluminum sheet for hogging/sagging, etc... so I can see if the weight is feasible?
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Sounds like an ideal application for frameless GRP/PVC foam sandwich construction.
     
  3. gonzo
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    gonzo Senior Member

    It depends on what structure you design. The skin is only a small part of the overall design. If you want the structures to nest, they can't have a deck.
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    There's a couple of ways to go - a thin skin with supporting structure, which would be typical or a thicker "loaded" skin, possibly with rolled, beaded or folded elements to offer panel stiffness, while requiring less supporting structure. The thin skin will have to be glued or fastened, as it's just impractical to weld, though the thicker skin could be welded, of course depending on gauge.

    Naturally, you'll have to work up weight estimates, loading, etc. so you can develop scantlings, particularly for this building approach. As to where you might get the information you need, short of a engineering course, well you might try some of the basic texts of the subject.

    Try the book store here:

    "Aluminum Structures: A Guide to Their Specifications and Design"
    "Boatbuilding with Aluminum: A Complete Guide for the Amateur and Small Shop"
    "Aluminum Boatbuilding"

    These would be the logical place to start. I might add, this isn't the easiest, lightest nor least costly way of getting what you want. Considering the size of your project, this will likely be the most costly Wa'apa derivative attempted.
     
  5. sidetrack
    Joined: May 2013
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    sidetrack Junior Member

    Thank you PAR

    I've had the engineering courses, looking for more of a shortcut to the specific application. The weight though is the thing: 1.5mm sheet isn't so bad, 2mm+ and it's things get way too heavy. Looks like there's not much short of launching into (and learning) a fairly complete design to find out.
    I've been looking at DNV standards for that, but they don't seem to completely translate from ships to small open canoes. The books you recommend are something I'll have to check out.
    The cost is a funny thing, there's a ready supply chain on island for marine aluminum, sourcing and shipping good marine ply and fiberglass materials (hazmat) doesn't come out much cheaper and might take a couple of months to arrive. Easier for me to just sail to Fiji, I know Gary Dierking got material there!
    Something between a small aluminum rowing/sailing dinghy and an Aluminum Canoe should be possible to my mind. But, there's not going to be many complex engineering feats pulled off in this little corner of the world if that's what it'll take.
     
  6. gonzo
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    gonzo Senior Member

    Why the requirement for three nesting sections? That will easily double the weight of the boat.
     
  7. sidetrack
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    sidetrack Junior Member

    It'll need to be stored on deck on a 38ft monohull during passages.

    Removable seats/thwarts/stiffeners are a possibility though, and I think I can place the iakos away form the bulkheads, and they might stiffen things up a bit as well.
     
  8. gonzo
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    gonzo Senior Member

    Have you done any stability calculations for the 38 footer with a second boat on deck?
     
  9. sidetrack
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    sidetrack Junior Member

    No, I do live human testing

    [​IMG]
     
  10. PAR
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    PAR Yacht Designer/Builder

    I don't see any issue with an aluminum Wa'apa like craft, on the deck of a 38' mono. It just doesn't weigh enough to get all excited about.
     

  11. sidetrack
    Joined: May 2013
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    sidetrack Junior Member

    That's pretty much my opinion. It will be replacing my existing dinghy, and as long it's a weight that I can manhandle around it should net out around the weight of additional passenger. If the stability went to hell every time I went up to the bow, I wouldn't take it to sea.
     
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