hreko

Discussion in 'Boat Design' started by hreko, Sep 14, 2012.

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  1. hreko

    hreko Previous Member

    "
    Dinghy looks like RIB but it is rigid structure (composite tubes are covered with thin PE sponge) of about 150 pounds and 2m3 "hermetically" closed air. It is not structural but integral part of hull that can withstand full load (complete immersion under water.) Hreko has B stix category with 30,4 points. For unlimited ocean sailing it should be redesigned.
     
  2. hreko

    hreko Previous Member

    I am absolutely agreed that crossection 2 is much better than section 1.
    Hreko has lifejacket and not lifepants.;)
     
  3. TANSL
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    TANSL Senior Member

    HReko, I'm sorry but I do not know what are the "lifepants". I do think you are taken as a joke some things that are very serious but, after all, is your project and you who must enjoy or suffer it. Farewell, my friend.
     
  4. viking north
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    viking north VINLAND

    hreko --my comment on early reefing would be only necessary if under sail in a strong breeze the lee sponson becomes submerged and starts acting like the bow planes on a submarine, dragging her bow under at the same time increasing heel. This could quickly become a dangerous situation prevented only by reducing sail early before the cycle is initiated. If as you state, her initial stability is designed to prevent this from ever happening then it should be a fun boat. However if those sponsons do have a negative angle of attack be ON GUARD when running at speed under higher angles of heel. I'd do so until you get some hours and sea conditions under your belt with her. All in all I commend you for thinking outside the box, having the conviction right or wrong to throw "faith to the wind" (actually a good name) and give it a go. She's a new horse to be broken and her saddles me thinks might require some adjustments, ride her with that thought in mind and I'm sure you'll make it work. Good Luck --Geo.

    A yacht is not defined by the vessel but by the care and love of her owner ---
     
  5. Skyak
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    Skyak Senior Member

    A 150 lb dingy that can take more than 2 metric tons in it's solid mount? Quite surprising. I think I will reconsider mine.
     
  6. hreko

    hreko Previous Member

    Dinghy is cc 3,2 m long; 1,8m wide and 0,5 m high. This is cc 2 m3 volume and about 80 kg weight (with 20 kg Li ion battery and 10 kg electro motor jet propulsion) . Its made of carbon/glas/epoxy/corecell sandwich. What's wrong?
     
  7. Skyak
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    Skyak Senior Member

    I am no expert on RIBs. All I know is from handling them on deck (the worst part of my sailing day) and a few calculations I did on a concept similar to yours of using the dingy to extend waterline. 150 lbs would be a very reasonable weight for a RIB that size with no motor. For that to include the electric propulsion is impressive. For that to include the ability to support 2 metric tons or more cantilevered...makes me want to check calculations.

    If this works as planned EVERYONE will want one.
     
  8. hreko

    hreko Previous Member

    This is not RIB (there is nothing to be inflated). This is integral part of mother ship made of most modern materials, properly fixed to sustain forces you can expect.
     
  9. bpw
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    bpw Senior Member

    So the dinghy will be built to the same scantlings as the mothership?

    I understand the dinghy will not need to deal with more load than its buoyancy or weight when full of water, but very few small boats can survive those loads when supported at only one end. And that is ignoring the dynamic loads the stern of a boat encounters.

    Sounds very difficult to deal with while keeping the dinghy light enough to drag up a beach.
     
  10. bpw
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    bpw Senior Member

    Also, I am curious, do you have a stability curve? To my eyeball it looks like a boat that would be very happy floating upside down. Would be interesting to see the shape of the inverted stability curve.

    I don't really understand how a wide flat boat with no keel will be self righting, plenty if ocean racers float quite happily upside down, even with very deep heavy bulb keels.
     
  11. TANSL
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    TANSL Senior Member

    bpw, in general the term "self righting" is not used properly. It is always necessary to help a capsized boat to regain its upright position. To my knowledge there is only one type of lifeboat, very special, which is really self righting. What it is true, and here is, probably, the mistake is that most sailboats have a positive righting arm at angles of heel greater than 90 °. The angle of "vanishing stability" can be 120 degrees or more. Precisely on the boat HReko this angle is not the greatest I've ever seen.
     
  12. bpw
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    bpw Senior Member

    Aware of this, was what I was getting at with my question, 110 degree positive stability and claims of self righting do not make much sense to me. Though it is possible to have very little stability and still self right, it is not very common and don't think it applies I this case.
     
  13. hreko

    hreko Previous Member

    Attached Files:

  14. bpw
    Joined: May 2012
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    bpw Senior Member

    I am also curious about where all the weight in this boat is coming from, is it the batteries etc...certainly not a light weight boat.

    A Dudley Dix Didi 40 weighs exactly the same amount (in IMS race trim), but has 2000kg of ballast.

    I found the stability curve on your site, lots of area underneath, not surprised.
     

  15. bpw
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    bpw Senior Member

    A catamaran will also self right with an airbag on top....

    Edit: I now notice you said can be righted without outside help, not self righting. My fault for reading quickly.
     
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