Scow Moth Designs

Discussion in 'Sailboats' started by luckystrike, Nov 26, 2014.

  1. luckystrike
    Joined: Feb 2010
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    luckystrike Power Kraut

    Hi There!

    Yesterday I found a video on youtube and was fascinated by the simple elegance of this boat. Must be great fun to build and sail one.

    https://www.youtube.com/watch?v=vpPPYhM_2-U
    (More from this guy in his channel)

    It is unlikely that anybody can define the design in the video but perhaps there are a few people that can help me to find a good scow design.

    My own researches lend to the bunyip. Is this a good boat or is there a better one to build.
    What is this boat, looks quite actual?
    View attachment 96047

    Are these blaning bottoms are really rectangular or is there a little curve on the outside? What is a typical width of a planing bottom?

    I know that these questions are a little crazy, but I would be thankful for some answers from the scow sailers here on boatdesign.

    Best Regards, Michel
     
  2. daiquiri
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    daiquiri Engineering and Design

    A good info about scows, their history and various classes can be found in this Wiki page: http://en.wikipedia.org/wiki/Scow

    Since the size, number of crew and handling varies a lots between different scow types, the first question would be: what type or size of scow are you after?

    Cheers
     
  3. luckystrike
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    luckystrike Power Kraut

    Sorry, you are right, thats really important.

    looking for a singlehander scow of Moth class, maybe a foot longer (12') because Iam a little heavy for a Moth. But no leasure boat, should be a racer.

    McFrawd lines shall be around somewhere, this would be nice.

    Many thanks, Michel
     
  4. gggGuest
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    gggGuest ...

    The earlier australian scow moths were certainly absolutely flat bottomed, indeed some were completely rectangular in section, albeit with a lot of shape in plan and profile. The later ones got a lot more complicated though. If you can get hold of a copy of australian Wooden boats Vol 1 (eg http://books.google.co.uk/books/about/Australian_Wooden_Boats.html?id=ISyPAAAACAAJ) that has lines for the Australian Mk 2 Moth, which looks a pretty straightforward build.
    Also have you seen this...
    https://www.youtube.com/watch?v=wWkd2e8apSI
     
  5. Doug Lord
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    Doug Lord Flight Ready

  6. CT249
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    CT249 Senior Member

    The Bunyip was a very good design from memory. The later Moths like McFrawds had narrower sterns. This allowed the sailor to sink the stern when going downwind in heavy air and reduced nosediving.

    There is curve on the outside of the bottom, and this curve is very important as it determines the shape when the boat is heeled in light winds. The scow Moth was extremely popular in Australia and most Moths used to be home built, so these designs were actually very refined in terms of shape and construction.

    Contact the Australian Moth class for more information.

    Scows are fantastic boats; I wish we still had ours. Ian Ward, who is involved with the Glyde foiling Laser, was involved in the McFrawd project and may have a set of the plans, perhaps.
     
  7. gggGuest
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    gggGuest ...

    Well, looky what's turned up with some searching...

    From the Australian Moth site we have some plans in their design guide...
    http://www.moth.asn.au/rohans_site/design_guide.html

    Firstly the Mk2, and these are even basic building plans
    http://www.moth.asn.au/rohans_site/download/mkII_moth_plans.pdf

    And then the later "Mouldie", which had to be cold moulded from veneers, although later on folks made multi chine boats to the same basic shape.
    http://www.moth.asn.au/rohans_site/download/Cole_super_moth.pdf
     
  8. tdem
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    tdem Senior Member

  9. NoEyeDeer
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    NoEyeDeer Senior Member

    Interesting note on that Aus. Moth page about WA boats in the '70's having the bottom plywood at 45 degrees to give a stiffer bottom.
     
  10. luckystrike
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    luckystrike Power Kraut

    Many thanks for your help!°!! I searched the internet too.

    What I have found (so far) is:

    Bunyip: The complete building instructions, lines and bulkheads.

    McFrawd: The building instructions and some drawings (no scale) of profile and deck. (A set of lines would be nice to have for further research)

    Perverted Moth: A high tech remake of bunyip from a pro-designer, complete plans in carbon / foam.

    And a lot of informations from various forums where the design path went in the 1980's, after the skiffs dominated the race scene and practically no scow won a major race. (Narrower boats and single chines, this is the kind what the japanese guy from the video seems to have).

    CT249: Yes bunyip and McFrawd have nearly the same bottom, profile, deckline and measures. The curve of bottom in the decksview must have something to do with planing behavior too, not only light wind. I think it makes planing more stable and controlable. Must be the same theme as for the windsurfers, who are narrowing their sterns also, from the 80's until today.

    A interesting detail are the tunnels at the front, they seem to be really important for channeling the water under the bottom.

    Nevertheless, I have enough informations to open freeship and draw a nice looking fun-scow-moth with a lot of sexy curves in the sheer and the panels. If you are interested I will post my results here.

    More funded informations are welcome!

    Best Regards, Michel
     
  11. messabout
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    messabout Senior Member

    Any more comment about the "gull wings" at the bow of Bunyip? What is the rationale for that feature? Since a lot of the OZ designs seem to have them, there must be some merit.
     
  12. PI Design
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    PI Design Senior Member

    There's an excellent facebook page if you search 'scow moth'.
     
  13. NoEyeDeer
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    NoEyeDeer Senior Member

    That was just the way the tunnel hull ran out at the bow. Gives a concave in plan view.
     
  14. The Q
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    The Q Senior Member


  15. luckystrike
    Joined: Feb 2010
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    luckystrike Power Kraut

    Facebook and tunnels

    Hello Everybody,

    I heared about the Facebook group and joined it, even if Iam a facebook denier.

    Lots of good stuff, the japanese guy (from the video) is also there and has posted his design to share.

    The tunnels at the front, and sometimes even hollow bulkheads there seems to channel the incoming water and guide it under the planing bottom. I think it creates more lift at the front which is quite important as the scow moths have only a little freeboard and tend to nosedive when sailing in (even small) waves.

    I know this hollow bottom stuff from the 80' and 90', when we made these channels into our windsurfboards to create more lift. From our feeling we did right. I had a board with 4 channels, worked well!

    Ok, I have now 5 different and succesful designs on hand, thats more than enough to read the principles of scow design. And two written construction manuals including the scantlings. Thanks to the god of old fashioned paperwork ... I would have made it far to strong, heavy and expensive.)

    Next step is to start design work. To adapt the Moth for my physical needs (48 years of age, 1,92m tall and more than 100kg heavy, it seems as the "fat moth" will be 3,6 to 3.7m long. Beam is not decidet yet, but bottom width will be around one meter. It will have a single chine hull with a slightly rounded bottom to allow permanent planing even if the boat is not perfectly trimmed upright. Stressforming the plywood a little will stiffen the structure. And the details I mentioned above, I like sexy curves.

    I will be offline until sunday 7th and looking forward for more discussions.

    Again, many thanks for your help and ...

    Greetings from the ******* cold North Sea Coast, Michel
     
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