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Re: Twinkle Twinkle little boat

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  • rljssn
    I don t have Gerr s book yet so I suppose the spreadsheet would not help me much. Thanks for the offer though. Part of the problem is that I m not sure what
    Message 1 of 10 , Jan 4, 2008
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      I don't have Gerr's book yet so I suppose the spreadsheet would not
      help me much. Thanks for the offer though.

      Part of the problem is that I'm not sure what engine was supposed to go
      in these boats originally. Typical small sizes (3hp) were often cast
      iron, two stroke, make-n-break ignition. Above twenty horsepower they
      were often small marine four cylinder equipped from Grey marine or
      Redwing, etc. What were the in between marine motors like? A ten horse
      make-n-break is heavy. That could weigh as much as the hull! I would
      suppose the hull to be around 300-400lbs. This makes estimating the
      weight to horsepower difficult.

      I would think the tunnel would force the bow down in acceleration like
      on Mr. Whites RM. The jet of water from the tunnel would pull the water
      from transom and make it difficult to tell when she would be on plane.
      This design is right at the threshhold of a semi-planing boat. The
      concern is that she might not perform well unless very lightly loaded.
      If fuel mileage in this day were not a concern I would build a Little
      Water. :)
    • Ronald Fossum
      Well, since we re talking a planing (or semi-planing) boat and somewhere in the same time period as RM, the 15HP RM engine was pegged by Bill A at about 340# &
      Message 2 of 10 , Jan 4, 2008
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        Well, since we're talking a planing (or semi-planing) boat and somewhere in the same time period as RM, the 15HP RM engine was pegged by Bill A at about 340# & 91ci. As to the smaller engines, I remember in the late 40s that 16' inboards in the Puget Sound (rental boats at "resorts") usually had a 2 or 3HP Briggs & Stratton or equivalent (Reinell and Marysville Boat Works both used that) and they moved along quite nicely at 6 or so knots (nobody really measured that sort of thing back then - it just got you there fast enough or it didn't).


        ----- Original Message -----
        From: rljssn
        To: AtkinBoats@yahoogroups.com
        Sent: Friday, January 04, 2008 3:46 PM
        Subject: [AtkinBoats] Re: Twinkle Twinkle little boat


        I don't have Gerr's book yet so I suppose the spreadsheet would not
        help me much. Thanks for the offer though.

        Part of the problem is that I'm not sure what engine was supposed to go
        in these boats originally. Typical small sizes (3hp) were often cast
        iron, two stroke, make-n-break ignition. Above twenty horsepower they
        were often small marine four cylinder equipped from Grey marine or
        Redwing, etc. What were the in between marine motors like? A ten horse
        make-n-break is heavy. That could weigh as much as the hull! I would
        suppose the hull to be around 300-400lbs. This makes estimating the
        weight to horsepower difficult.

        I would think the tunnel would force the bow down in acceleration like
        on Mr. Whites RM. The jet of water from the tunnel would pull the water
        from transom and make it difficult to tell when she would be on plane.
        This design is right at the threshhold of a semi-planing boat. The
        concern is that she might not perform well unless very lightly loaded.
        If fuel mileage in this day were not a concern I would build a Little
        Water. :)





        [Non-text portions of this message have been removed]
      • rljssn
        i tried one of those prop calculators on the net. 9hp engine running at 3600rpm reduced 2:1 at the prop. The boat displaces 1000lb total (hull, motor, people).
        Message 3 of 10 , Jan 4, 2008
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          i tried one of those prop calculators on the net.
          9hp engine running at 3600rpm reduced 2:1 at the prop.
          The boat displaces 1000lb total (hull, motor, people).
          15.5' waterline length brings a 5.2mph displacement speed.

          All of this yields a propeller of 11 inch diameter and 18 inches of
          pitch to get the hull to 16 mph.

          I think I'm getting close because the Atkin drawing looks like a 10"
          diameter propeller with a little clearance.

          Russell
        • Kenneth Grome
          ... Maybe, but I wouldn t bet on it having as much downward thrust as the Atkin tunnel-stern boats. The tunnel-sterns use the entire width of the boat to
          Message 4 of 10 , Jan 4, 2008
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            > I would think the tunnel would force the bow
            > down in acceleration like on Mr. Whites RM.

            Maybe, but I wouldn't bet on it having as much downward thrust as the
            Atkin tunnel-stern boats.

            The tunnel-sterns use the entire width of the boat to direct the water
            downward. By directing so much more water downward, they can use far
            less hook in the aft hull bottom than I see in Twinkle's tunnel
            section ... and I think the less hook used to direct water downward,
            the more fuel efficient the boat will be.

            Do you need a tunnel hull for propeller clearance where you're planning
            to use the boat?

            Sincerely,
            Ken Grome
            Bagacay Boatworks
            www.bagacayboatworks.com
          • rljssn
            The tunnel boat is for the super shallow water we have here. We are in drought level four here in Georgia and the water levels are so low most boats are seeing
            Message 5 of 10 , Jan 6, 2008
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              The tunnel boat is for the super shallow water we have here. We are in
              drought level four here in Georgia and the water levels are so low most
              boats are seeing very little use because of the danger to exposed
              stumps. This large man made lake is notorious for eating props (even at
              high water levels). The shallow draft on Twinkle along with the
              efficient four stroke engine might work very nice in these conditions.
              I'm not tournament bass fishing so I don't need alot of speed.

              I understand about the Rescue Minor's tunnel. In the article on Twinkle
              it is mentioned. I have studied all the tunnel boats but like this one
              for the simplicity and size.

              I'm waiting for Michigan Wheel to get back to me on the prop size.
              I'll let everyone know what they recommend.

              thanks,
              Russ
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