Designing a sailing dinghy for expeditions

Discussion in 'Boat Design' started by BoraBoats, Feb 25, 2019.

  1. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Emilie, I think the ski( with its associated buoyancy) is the way to go. When you need this extra RM the boat may not be moving very fast so the hydrofoil won't be so beneficial-and they are likely to cost more. The foil , in the location you show it, could make it harder to right the boat(it may be in the way) and the crew might want to use it as a lever and hurt themselves on the trailing edge.
    ---I'd consider moving the main forward a little- maybe by reducing rake. In my experience on small boats like this if the geometric CE and quarter chord of the daggerboard are lined up she should balance well. The reefed rig should also balance well since weather helm would tend to increase in stronger wind.
    ---I think those vertical battens should be parallel to the mast-if not the sail won't roll up.
    ---As far as the main's CE goes I don't think its too high but you can do an analysis of it by figuring the RM of the boat with the crew in the center and then on the wing. You have to make a decision on how much wind you want to be able to use the main with the crew in center? In my opinion, it's not worth it to seriously erode the sailing performance so the crew can sit in the center and row.
    ---I've got to think about it, but you'll probably need a bowsprit(maybe retractable) with a Weta-like roller furling asy spin/screecher. In my opinion, the Weta solution is the easiest for the crew and will add power when you need it though when rolled up it will slightly impact upwind performance.....
    ---
    You're doing a great job-I hope the boat gets built!
     
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  2. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    Emilie, I was looking over your sketches again and it occurred to me that you might want to consider a redesign of your hiking wings. The shape now forces the crew to sit way aft to hike out fully which may not be a good idea when going upwind. The boat will need to be able to effectively develop maximum RM on a beat.
    Just a thought-see what you think.....

    a couple of Emilie's sketches:
    Emilie.jpg
     
  3. BoraBoats
    Joined: Feb 2019
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    Location: Norway

    BoraBoats Emilie

    Good point. I will see what I can do.
     
  4. BoraBoats
    Joined: Feb 2019
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    Location: Norway

    BoraBoats Emilie

    Hobie island has similar battens. They cannot be completely vertical because they need to hold the peak of the sail out. If the battens are flexible enough, they will still be able to roll up on the mast. It seems to be working for hobie.
    pedal-kayaks-hobie-mirage-tandem-island-kayak-2016-5.jpg
     
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  5. Doug Lord
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    Doug Lord Flight Ready

    Thanks for pointing that out!
     
  6. Doug Lord
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    Doug Lord Flight Ready

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  7. sharpii2
    Joined: May 2004
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    Location: Michigan, USA

    sharpii2 Senior Member

    I see you have made significant progress with your design.

    Two areas of concern:

    One, I see no cross-beam for the wings. With the crew on the windward one and the ski-float on the leeward one, there is going to be a considerable amound of bending loads. I see no structural elements to deal with this.

    Two, the sail design would probably work better without the flat top. Instead, a lot of roach can be put in the main. This way, you can use dead vertical battens, which will roll up easier.
     
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