canvas cement boat

Discussion in 'Boat Design' started by mike palmer, Dec 6, 2020.

?

can make sailboat using canvas cement

  1. no won't work

    4 vote(s)
    100.0%
  2. great idea should work great

    0 vote(s)
    0.0%
  1. mike palmer
    Joined: Dec 2020
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    Location: texas

    mike palmer New Member

    I am thinking about making a small sailboat using canvas cement - do you think this would work?
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    What do you mean by "canvas cement", I have never heard of it.
     
  3. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

  4. brendan gardam
    Joined: Feb 2020
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    brendan gardam Senior Member

    i think he means canvas impregnated with cement powder. they were like tarps you could pullover a frame and then wet with a hose to make the cement go off. i would think it would be too heavy for a boat.
     
  5. brendan gardam
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    brendan gardam Senior Member

  6. wet feet
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    wet feet Senior Member

  7. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    The survey is really biased. It is a bad idea, but a floating thing could be built.
     
  8. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    Cement, reinforced with fiberglass, has been used in construction for years. If the canvas is fiberglass and the cement is applied correctly, the result can be good. Fiberglass, working under tension, has better properties than steel.
     
  9. Squidly-Diddly
    Joined: Sep 2007
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    Squidly-Diddly Senior Member

    Not very well. I'm guessing those "tents" rely on wicking to keep most of the water that seeps through draining downwards to create an illusion of a water-proof roof. If you leave a boat in the water it better be well painted and how long is that paint gonna stick? I'd try a small barge, floating dock, etc first. Maybe use some of this stuff. AMICO - Stay-FormĀ® Concrete Forming System https://amicoglobal.com/stayform-concrete-forming/
     
  10. Ilan Voyager
    Joined: May 2004
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    Location: Cancun Mexico

    Ilan Voyager Senior Member

    Fiber in different ways (strands, canvas, in a lot of materials from linen to steel cloth passing by bamboo and fiberglass) with cement is an old idea. That may work when the stresses are moderate and the composite is not in the water. Cement is not very waterproof so in a lot of applications like roofs you have to add waterproofing chemicals. It's not a good glue so in a lot of applications you have to add a glue like polyvinyles, water based epoxies et some even more strange chemicals. It's extremely alcaline so it's able to destroy a lot of materials.
    Furthermore its ratio strength/weight is poor, and acceptable only in compression. The fibers improve just a bit in traction but the poor performances in gluing make that never you get a good bond between the fibers and the cement so the composite collapses well before the limits of the fiber. Flexion is a disaster. Vibrations destroy it.
    During the 2005 Wilma hurricane at Playa del Carmen, with 150 mph winds during 48 hours, most of the electrical posts in concrete collapsed by the alternance of flexions while none of the older ones in wood some almost 40 years old with similar constrains was damaged.
    Working cement composites is long and messing, asking for molds and a very long cure (28 days) unless using vapor. It needs a costly waterproof finishing unless having a thick coat of cement over the fibers or steels, the rule of thumb generally being one inch at least.
    Thousands of boats have been made in some composite of concrete mostly ferro cement. Except some barges with extremely confortable scantlings, few have lasted. Even less have been successful. It's horribly heavy and totally not suited for small boats. The construction in ferro cement after the 70ies fashion is almost extinct. There are good reasons. It's heavy, not so cheap, and it ages badly. If it was a good material for boat building we should see hundreds of thousands of fishing boats, small ferries, small working boats and yachts on the water. A lot of poor countries cry for cheap boats...
    The famous example of the canoes in cement challenge is not a good one. These canoes are not destined to last, their life span is a few weeks; although being far too heavy. The wood and the composite ones last years. Even kraft paper with glue canoes give far better results.
    The tents of the example are also not made to last, generally it's for operations of 3 years max. Their use is for military and humanitarian NGOs. These tents are considered disposable items.
    Composite cements work well in their domain: construction when weight is not a consideration, or it's an advantage. When a good ration strength/weight is needed, steel is preferred, look at the bridges...
    Interestingly we have seen boats and planes made in wood and canvas, plywood, composite sandwich wood like the Mosquito, composites and sandwiches using polyester, vinylester or epoxy, foams, honeycombs, glass and/or exotic fibers, aluminium and even some planes have been made with steel (inox sandwiches) like the XB70, steel and alu like the Mig 29, or sometimes a steel structure and canvas like the Fieseler.
    I've never heard of a working plane in cement.
     
    bajansailor likes this.
  11. Ilan Voyager
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    Ilan Voyager Senior Member


  12. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    The cement tent does not appeal, a large problem moving it to another camp site !
     
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