Balsa Strip Canoe 11ft 12lbs

Discussion in 'Wooden Boat Building and Restoration' started by BOATMIK, Aug 29, 2005.

  1. BOATMIK
    Joined: Nov 2004
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    Location: Adelaide, South Australia

    BOATMIK Deeply flawed human being

    Hi All,

    I have just put up a web page about a Strip Plank Canoe I built a few years ago. It includes information about scantlings which may be useful and/or interesting.

    My original thinking was to go as light as I dared and be prepared to dispose of the boat after a couple of years - but I found that the boat lasted very well, and sold it after 5 years of use for a useful amount of money.

    Best Regards
    Michael Storer

    Balsa Canoe Link
     
  2. Raggi_Thor
    Joined: Jan 2004
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    Location: Trondheim, NORWAY

    Raggi_Thor Nav.arch/Designer/Builder

    Very intersting!
    What is the cost of balsa as strips?
    I suppose it's much cheaper than the end grain distance material we buy...
     
  3. BOATMIK
    Joined: Nov 2004
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    BOATMIK Deeply flawed human being

    Hi Raggi_Thor,

    I built the boat a few years back and timber prices have changed a lot in the past few years - so I don't know.

    I got the balsa in the form of rough sawn flitches about 4"x5" by either 8ft or 10ft long. Then resawed and cusp and coved to make strips finished 7mm x 24mm. (How simple sawing makes imperial size timber goes metric is a bit of an Australian miracle - a lot of us use both systems!).

    The short lengths were not a problem with quick joining using cyanoacrylate glue. In fact I just made continuous strips and docked them to close to the right length for each strip as needed. Balsa wastage would have been less than 5% once the strips were milled.

    Basically it was the raw material that is sliced to make end grain balsa. So less processing probably means it will be cheaper. Not REAL cheap, but cheaper.

    I got my balsa from "Australian Balsa". Elsewhere in the world the only name I know of is Baltek

    One thing to be aware of if you manage to find a supply - the sap wood is pretty spongey so is best avoided - when you go to sand it compresses rather than abrades. In the lot I used it had a slight pink hue so was easy enough to avoid.

    But the building was pretty trivial in terms of effort - a few tricks to learn about not denting the balsa as I went but that was it. One of the most fun boatbuilding projects I have undertaken.

    Note that it was not really my idea, but a whole bunch of people as mentioned in the first paragraph of the webpage, I was just lucky enough to stumble on the idea of using it for a canoe as cute as the Rushton "Wee Lassie".

    Best Regards
    Michael
     
    Last edited: Aug 29, 2005
  4. Raggi_Thor
    Joined: Jan 2004
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    Location: Trondheim, NORWAY

    Raggi_Thor Nav.arch/Designer/Builder

    Thanks again for an interesting story.
    We also make a 2x2 (inches) into 48x48 (mm) by planing it :)
    The lightest wood we have here is spruce with a density of 400kg/m3 (or more).
     
  5. BOATMIK
    Joined: Nov 2004
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    BOATMIK Deeply flawed human being

    Your English is excellent!

    And I was wrong to assume Australia was the ONLY place where imperial timber turns into metric on sawing!!

    You are lucky to have spruce. In Australia we have a wonderful range of timber colours but most of them are hardwoods of relatively high densities - not really ideal for building a lightweight canoe

    Thanks again.

    Michael
    web page
     
  6. Doug Lord

    Doug Lord Guest

    Balsa + cyano

    I've built dozens of model boat plugs using balsa and cyano and have been thinking about building a bigger boat. I wonder about the wicking of water on long strips-those little "tubes" in balsa seem like they'd carry water a long way-have you had any trouble with that?
    I've rarely used cyano on a boat that actually touches the water -mostly on plugs. I used it once to hold two halves of a keel together and it came unglued while immersed(!). I've heard of others who say that cyano and water don't mix-any experience like that? The fumes from cyano are really bad and I recommend anyone using it uses a respirator-not just a dust mask. Cyano and balsa is a quick and fun way to plank a model and I'm looking forward to hear of experiences on full size boats-I know how to work with it and other than the two concerns I mentioned I like the idea.
     
  7. BOATMIK
    Joined: Nov 2004
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    BOATMIK Deeply flawed human being

    Hi Lorsail,

    There was a 32ft ULDB built in Australia by Arnie Duckworth who is the WEST agent in these parts. It was some years ago and it led to the development of the BALTEK DURAKORE product. I was only briefly on the scene during the time, so don't really know exactly what the end result was.

    The downsides of balsa plank for bigger boats from what I have heard were

    1/ denting of the balsa with light glass layups
    2/ problems with non predictable resin absorbtion - ie in building large boats where you have a target weight

    I don't know how serious the problems were.

    You could always send Arnie Duckworth an email. Their website is
    http://www.atlcomposites.com/

    I didn't have much problem with denting of the balsa canoe, but I am used to handling foam sandwich racing dinghies, so take some precautions (as mentioned on my web page).

    Where the glass is intact there is no problem, but with damage ... I guess you want to do something about it in the short term whether it is Cedar Strip or balsa strip.

    Regards
    MIK
    http://www.ozemail.com.au/~storerm
     
  8. BOATMIK
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    BOATMIK Deeply flawed human being

  9. Brands01
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    Brands01 Senior Member

    Hi Michael,

    I came across your balso canoe some time ago on your website, and found it a very interesting idea. Do you think it could be replicated with foam, as it is essentially a sandwich construction? Or do you think the fore-n-aft grain of the balsa adds considerably to strength?
     
  10. BOATMIK
    Joined: Nov 2004
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    BOATMIK Deeply flawed human being

    Howdy Brands,

    The balsa strip adds considerable longitudinal strength.

    I remember doing some calcs at the time - just simple first year engineering stuff and there was a big difference between foam and the longitudinal balsa.

    The point one can draw from the whole experience is that the standard weights of construction of cedar strip canoes is much more to allow the boat to survive handling loads on land rather than flat water "in use" loads.

    For example the cedar strip canoes are typically
    6mm cedar strip
    1 layer of 4 or 6oz glass inside and out.

    I used
    7mm balsa strip
    layer of 0.75oz glass inside and out
    second layer 0.75 glass outside over the flatter area of the bottom
    second layer 0.75 glass inside over crew area.

    Michael
     
  11. BOATMIK
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    BOATMIK Deeply flawed human being

  12. Mr Efficiency
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    Mr Efficiency Senior Member

    Paulownia is supposedly 280kg/cu m, stronger than balsa, but heavier too.
     
  13. BOATMIK
    Joined: Nov 2004
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    Location: Adelaide, South Australia

    BOATMIK Deeply flawed human being

    Howdy,

    I've posted a lot of information about Paulownia including using for framing for lightweight dinghies and strip.

    Another use is framing. The Goat Island Skiff had its basic hull weight of 130lbs built of gaboon ply and cedar brought down to 105lbs with extensive use of Paulownia for framing.
    http://www.storerboatplans.com/wp/?s=paulownia



    105lbs for a 15'6" performance dinghy with traditional features.

    Yes, in many ways paulownia is a much better candidate for strip planking and is much cheaper than cedar in many countries.

    In the Philippines there is an inexpensive species called Falcata that is very similar to Paulownia.

    Michael Storer
     
  14. BOATMIK
    Joined: Nov 2004
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    Location: Adelaide, South Australia

    BOATMIK Deeply flawed human being


  15. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Good to see your post my friend and also glad to see, the success of this design and scantlings approuch. How about a round bilge GIS maybe with balsa or Paulownia strips? Sure'd be pretty, lighter and even faster I'd dare suggest.
     
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