Inflatable sailing catamaran with tubeclamps

Discussion in 'Multihulls' started by DimitriW, Jun 13, 2013.

  1. DimitriW
    Joined: Jun 2013
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    Location: belgium

    DimitriW Junior Member

    I'm new to this forum and I just wanted to share my first boatbuilding experience with you. I managed to buy second hand two floats from a cataraft (hypalon fabric) and I made a new frame for it so I can use it as an inflatable catamaran. The frame is build with 60 mm diameter aluminium tubes, 3 mm thick and they are connected with standard tubeclamps (available in all shapes). It has a centreboard, two rudders and retractable wheels for beaching. The sails I used are from a 470. The total weight is 120 kg and all pieces fit inside my car (a Citroen Berlingo), the mast consists of 4 sections. Time for assembly is about 90 minutes but I guess that will shorten if get more routine.
    The catamaran is 2 meter wide and 4.5 meter long. I went sailing with it already 2 times and I'm very happy with the result (that's why I'm posting this now :)). Because of the construction with tubeclamps it's very easy to make adjustments on the design. For instance, at first the retractable wheels were at the back of the boat but then I had too much weight at the back. It took me two hours to change the design and now the wheels are below the mast, which makes it also a lot easier to move the boat. I also can move the centreboard very easy back or forward to find the best position (concerning wheaterhelm). I'll try to post some photo's here in the near future.
     
  2. mebebo
    Joined: Jun 2013
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    Location: istanbul

    mebebo New Member

    Hey, I have something really similar in mind to what you constructed. I dug up most of the internet and there's so few information about how to build inflatable sailboats. Can you please post some photos of yours?
     
  3. Nnnnnnnn
    Joined: May 2012
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    Location: MOW

    Nnnnnnnn Junior Member

    What kind of boat are looking for? On gik.fordak.ru you can find a lot of information. It is in russian, but google translator can help.
     

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  4. DimitriW
    Joined: Jun 2013
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    Location: belgium

    DimitriW Junior Member

    inflatable catamaran with tubeclamps

    I added some photos. If you want I can post more details on construction. The total cost for my project was about 2000 euro, the most expensive part being a Harken carbo block (500 euro). Al the aluminium tubes and tubeclamps cost about 1200.
     

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  5. DimitriW
    Joined: Jun 2013
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    Location: belgium

    DimitriW Junior Member

    I went sailing with my boat now for several times and I think I need to increase the surface of my centreboard because I experience to much drift. The centreboard (and rudders) are made of plywood covered with glassfiber and epoxy, they have NACA profile. Next step is to buy an electric outboard but I'm still checking out the best option for this type of boat (any advise is welcome). I think a Torqueedo would be great but I need to save some money first :). And after that I might consider to install solar panels in the front to charge the battery (should be possible in 8 hours full sun).
     
  6. Nnnnnnnn
    Joined: May 2012
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    Location: MOW

    Nnnnnnnn Junior Member

    Dmitri,
    I like the idea of landing wheels. How much is the weight of your boat?
    Used method of attaching floats to frames is considered rather unreliable, at least in ex-USSR. Glued/sewn pockets for longitudal links are now most popular solution. Something like on the pictures:
     

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  7. DimitriW
    Joined: Jun 2013
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    Location: belgium

    DimitriW Junior Member

    Total weight (fully rigged) is 120 kg. Glued pockets is a good idea, I might change that if I get problems with the attachement of the floats but I have no experience with glueing that material and therefore I don't rely on that. For now the floats are roped between two aluminium tubes and they seem to stay nice in place, even if I flip the boat on it's side with the total weight pressing lateral on the tube. It is how the floats where attached to the original frame of the raft, able to withstand white water conditions.
     
  8. Petros
    Joined: Oct 2007
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    Location: Arlington, WA-USA

    Petros Senior Member

    What a great idea, rally nice work. I have considered something similar but with a folding wood frame, wood costs less and is more attractive I think, but more work to build and would weight more since the structure would have to use larger members to get the same strength.

    The centerboard/dagger board is usually figured about 5 percent of the sail area. If you sail in light winds at lower speeds slightly large would be helpful, if always at faster speeds it can be a bit smaller.
     
  9. DimitriW
    Joined: Jun 2013
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    Location: belgium

    DimitriW Junior Member

    Ok, thanks Petros, that's very usefull information about the centreboard. Wood indeed is more attractive I agree, but building time was important for me. I can build this boat from scratch in 10 days (full time) and there are allmost no parts that can easily break and if they do, it's very easy to repair. I also think I overdimensioned the tubes of the frame and I used steel tubeclamps instead of aluminium because of the price difference, so I think in the future I can bring the weight down to maybe 90 kg. Aluminium tubeclamps also would be better in preventing galvanic corrosion if I start to use this boat in salt water, but first I wanted to have a working prototype before investing more money in it.
     
  10. raf pali
    Joined: Mar 2012
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    Location: Australia

    raf pali Junior Member

    It's a nice Idea. I too some years back have thought of some sort of inflatable little cat but I could not find the rubber tubes. I'd love to put my hands on rubber tubes like yours. Please let me know if those things are available in Au. I think it would make a more efficient dingy for yachts, easier to row, more economical on fuel and faster plus a joy to sail, by far better than rubber duckies and possibly foldable for deck stow. I might be wrong but there could be future for a production.
    Well done M8
     
  11. raf pali
    Joined: Mar 2012
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    raf pali Junior Member


    Top notch. Good work
     
  12. mebebo
    Joined: Jun 2013
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    Location: istanbul

    mebebo New Member

    It's mostly like Dimitri's boat, but I'm gonna have to glue together my own floats with PVC coated polyester fabric. I'm trying to find a solution to make more hydrodynamic ones, rather than plain cylinders with end cones on both sides. For example here's a detail of HappyCat's floats' peak: http://www.happy-cat.at/typo3temp/pics/c2f0de2f00.jpg . I guess it would be a little hard with house tools though.

    And thanks for the photos, they're really informative!
     
  13. SuenosAzules
    Joined: Apr 2010
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    Location: Palm Beach Gardens, Florida

    SuenosAzules Junior Member

    Very Cleaver Design..

    Very cleaver design, looks like a lot of fun even if it is not as perfect as you want it! Good work!
     
  14. Skyak
    Joined: Jul 2012
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    Location: United States

    Skyak Senior Member

    I have been following the site NNNNN posted -chrome will translate but not well. There are some real artists making these inflatables in Russia. I don't think we will have the time to develop the skills so I think the best solution for us is nose cones with an expanding foam fit to the float.

    Some frame inside the float with inflatable liners would offer some improved capability -then the skin could be PVC on polyester or even polyester with a coating applied after shaping without the problem of slow leaks from pinholes. Hypalon is pricey and hard to work with.

    If sailboats didn't take so much space when they were not in use there would be a lot more sailors.
     

  15. DimitriW
    Joined: Jun 2013
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    Location: belgium

    DimitriW Junior Member

    I got a problem... A few weeks ago one of the outer pockets teared from back to front for about 2 meter while I was using it as a raft (without the mast) on a calm river in my city (Ghent, Belgium). We were actually not moving at all at that time, just floating and having a drink (maybe too much :)). We didn't hit anything it just happened like that. I don't measure the pressure (maybe I should), but from my subjective opinion the pressure was not that high. I guess the material is getting old.
    The floats are constructed with an inner float of neoprene and an outer pocket made of hypalon. It was the outer pocket that ruptured (not on a seem), so the boat was still floating and stable and we managed to continue the trip back home. I managed to stitch the outer pocket (it doesn't need to be airtight and it was constructed with stitching) but my confidence is gone in these pockets, so I want to make new ones.
    The fabric doesn't need be airtight but strong enough to hold the pressure of the inner tube, resistant to rocks (white water use), not soke up water, UV resistant, it should not stretch out when I inflate the tube but hold the shape. Any ideas on which fabric to use? I've been thinking of kevlar or polypropyleen but it can't be too thick because I need to be able to stitch it with a regular machine. Having it custom made will cost me a fortune and I can't buy new floats on the market here in Belgium. Using hypalon again is also an option but that will cost me around 500 euro and I have never worked with that material (I don't want to mess up 500 euro...).
     
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