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Re: [Michalak] AF4 Electric powered

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  • Kenneth Grome
    ... Jim designed another of his cuddy cabin motor boats specifically for electric power, so maybe Electron would be better:
    Message 1 of 12 , Jun 6, 2006
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      > Time for another hairy idea. How about a shaft driven electric AF4?


      Jim designed another of his cuddy cabin motor boats specifically for electric power, so maybe Electron would be better:

      http://www.duckworksbbs.com/plans/jim/electron/index.htm

      Kenneth Grome
      Bagacay Boatworks
    • John Kohnen
      AF4 being flat-bottomed she has a lot of skin friction (directly related to the area of the immersed skin), which is a major component of drag at low speeds.
      Message 2 of 12 , Jun 6, 2006
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        AF4 being flat-bottomed she has a lot of skin friction (directly related
        to the area of the immersed skin), which is a major component of drag at
        low speeds. AF4 is also a planing boat, at non-planing speeds her immersed
        transom creates a lot of wave drag. An electric AF4 would work, but not
        very well. If you brought the bottom up in a fair curve so the bottom of
        the transom was just barely above the waterline with crew and gear aboard
        it'd help a great deal.

        On Tue, 06 Jun 2006 13:49:04 -0700, M Russon wrote:

        > ...
        > Time for another hairy idea. How about a shaft driven electric AF4?
        > ...
        > The Af4 being flat bottomed has pretty low
        > displacement and could move along nicely at 5 knots or so.
        > ...

        --
        John <jkohnen@...>
        You can safely assume that you've created God in your own image when it
        turns out that God hates all the same people you do. <Anne Lamott>
      • Kenneth Grome
        ... Hi John, I have a question here: I always seem to see people post messages saying that the transom should just kiss the waterline or be just barely
        Message 3 of 12 , Jun 6, 2006
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          On Tue, 06 Jun 2006 21:29:34 -0700, John Kohnen wrote:
          > If you brought the bottom up in a fair curve so the bottom of
          > the transom was just barely above the waterline with crew and
          > gear aboard it'd help a great deal.


          Hi John,

          I have a question here:

          I always seem to see people post messages saying that the transom should "just kiss the waterline" or be "just barely above the waterline". I don't understand the reason for this type of recommendation ...

          If the water is not supposed to touch the transom anyways, it seems to me that the better recommendation would be to make sure the bottom of the transom is WELL ABOVE the water line. Wouldn't this be a better recommendation?

          Then if they happen to put more weight in the boat than they anticipated, the transom will still be above the water, and the boat will still be driven efficiently without any transom drag.

          Kenneth Grome
          Bagacay Boatworks
        • Ron Schroeder
          Hi Kenneth, The two main things for a displacement hull is that the transom doesn t drag AND the waterline length. If the transom is way up out of the water,
          Message 4 of 12 , Jun 7, 2006
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            Hi Kenneth,

            The two main things for a displacement hull is that the transom doesn't drag
            AND the waterline length. If the transom is way up out of the water, the
            waterline length shortens, lowering your speed.

            Ron Schroeder
            WD8CDH

            ----- Original Message -----
            From: "Kenneth Grome" <bagacayboatworks@...>
            To: <Michalak@yahoogroups.com>
            Sent: Wednesday, June 07, 2006 1:55 AM
            Subject: Re: [Michalak] AF4 Electric powered


            On Tue, 06 Jun 2006 21:29:34 -0700, John Kohnen wrote:
            > If you brought the bottom up in a fair curve so the bottom of
            > the transom was just barely above the waterline with crew and
            > gear aboard it'd help a great deal.


            Hi John,

            I have a question here:

            I always seem to see people post messages saying that the transom should
            "just kiss the waterline" or be "just barely above the waterline". I don't
            understand the reason for this type of recommendation ...

            If the water is not supposed to touch the transom anyways, it seems to me
            that the better recommendation would be to make sure the bottom of the
            transom is WELL ABOVE the water line. Wouldn't this be a better
            recommendation?

            Then if they happen to put more weight in the boat than they anticipated,
            the transom will still be above the water, and the boat will still be driven
            efficiently without any transom drag.

            Kenneth Grome
            Bagacay Boatworks
          • Rob Rohde-Szudy
            What Kenneth said. AF4 actually IS a bit of a speedster, if you have the stomach to push it that fast. Jim had his up to 20 mph testing it with an 18hp motor.
            Message 5 of 12 , Jun 7, 2006
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              What Kenneth said. AF4 actually IS a bit of a speedster, if you have the stomach to push it that fast. Jim had his up to 20 mph testing it with an 18hp motor. Most of us wouldn't care to go much faster. The result is that the stern is wrong for displacement speed operation. To plane you need that transom down in the water to provide bearing surface. But at lower speeds that same transom drags in the water, and the eddy currents rob you of power. Batteries are damned heavy, so you can't afford to waste their power. You need a lower resistance hull for electric. A fantail launch might be ideal, but you at least need the transom not to drag. A sailboat hull would be far superior, as would Jim's purpose-designed electric boat.

              There are also problems with using electricity for main propulsion. Batteries are expensive and the power to weight ratio is abysmal compared with even the oldest piece of junk gas outboard. I don't think it's practical for a trailered boat.

              Why are you trying so hard to avoid an outboard, anyway? It's what AF4 is designed for, and it's about the cheapest propulsion you will find.

              --Rob



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            • jmbell1
              ... the stomach to push it that fast. Jim had his up to 20 mph testing it with an 18hp motor. My AF4 could run 22.5 mph (GPS) at WOT with a 15 HP motor. I ran
              Message 6 of 12 , Jun 7, 2006
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                --- In Michalak@yahoogroups.com, Rob Rohde-Szudy <robrohdeszudy@...>
                wrote:
                >
                > What Kenneth said. AF4 actually IS a bit of a speedster, if you have
                the stomach to push it that fast. Jim had his up to 20 mph testing it
                with an 18hp motor.


                My AF4 could run 22.5 mph (GPS) at WOT with a 15 HP motor. I ran a 25
                HP motor for a short period of time and it would do an honest 30 mph.
                It was happiest at about 12-14 mph giving the best ride, fuel economy,
                and handling/tracking at that speed. As others have said, AF4 is
                supposed to be a fairly fast boat. A better choice for a slow boat
                would be either to start with Jim's ELECTRON, or to take a sail boat,
                delete the rig, and add power.
              • Chuck Leinweber
                Speaking of electric, I bought an electric RC airplane the other day. It weighs almost nothing yet it will fly for 6-10 minutes on a charge. What kind of
                Message 7 of 12 , Jun 7, 2006
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                  Speaking of electric, I bought an electric RC airplane the other day. It
                  weighs almost nothing yet it will fly for 6-10 minutes on a charge. What
                  kind of battery does that sucker have? It only cost ten bucks for the whole
                  thing (they were on sale - now they are back up to $15)
                  http://www.hobbypeople.net/gallery/222714.asp
                  The point is: changes in this field are coming rapidly so you have to check
                  every 10 minutes to see what is different.
                  Chuck


                  > What Kenneth said. AF4 actually IS a bit of a speedster, if you have the
                  stomach to
                  > push it that fast. Jim had his up to 20 mph testing it with an 18hp motor.
                  Most of us
                  > wouldn't care to go much faster. The result is that the stern is wrong for
                  > displacement speed operation. To plane you need that transom down in the
                  water
                  > to provide bearing surface. But at lower speeds that same transom drags in
                  the
                  > water, and the eddy currents rob you of power. Batteries are damned heavy,
                  so you
                  > can't afford to waste their power. You need a lower resistance hull for
                  electric. A
                  > fantail launch might be ideal, but you at least need the transom not to
                  drag. A
                  > sailboat hull would be far superior, as would Jim's purpose-designed
                  electric boat.
                  >
                  > There are also problems with using electricity for main propulsion.
                  Batteries are
                  > expensive and the power to weight ratio is abysmal compared with even the
                  oldest
                  > piece of junk gas outboard. I don't think it's practical for a trailered
                  boat.
                  >
                  > Why are you trying so hard to avoid an outboard, anyway? It's what AF4
                  is
                  > designed for, and it's about the cheapest propulsion you will find.
                  >
                  > --Rob
                  >
                  >
                  >
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                • Ron Schroeder
                  Hi Chuck, Unfortunatly, the cost of the Li-Poly batteries in the size needed for an electric boat is very expensive. It would take 15,000 of those cells from
                  Message 8 of 12 , Jun 7, 2006
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                    Hi Chuck,

                    Unfortunatly, the cost of the Li-Poly batteries in the size needed for an
                    electric boat is very expensive. It would take 15,000 of those cells from
                    the small R/C plane to equal 6 golf cart batteries. That blows my budget.

                    Ron Schroeder
                    WD8CDH


                    ----- Original Message -----
                    From: "Chuck Leinweber" <chuck@...>
                    To: <Michalak@yahoogroups.com>
                    Sent: Wednesday, June 07, 2006 11:18 AM
                    Subject: RE: [Michalak] Re: AF4 Electric powered


                    >
                    > Speaking of electric, I bought an electric RC airplane the other day. It
                    > weighs almost nothing yet it will fly for 6-10 minutes on a charge. What
                    > kind of battery does that sucker have? It only cost ten bucks for the
                    whole
                    > thing (they were on sale - now they are back up to $15)
                    > http://www.hobbypeople.net/gallery/222714.asp
                    > The point is: changes in this field are coming rapidly so you have to
                    check
                    > every 10 minutes to see what is different.
                    > Chuck
                  • mrusson
                    So a good little 10 HP outboard may get her to 10-12 Mph....which would be ideal really. I guess i ll start hunting for a 10 HP outboard...... MRusson ... have
                    Message 9 of 12 , Jun 14, 2006
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                      So a good little 10 HP outboard may get her to 10-12 Mph....which
                      would be ideal really. I guess i'll start hunting for a 10 HP
                      outboard......

                      MRusson




                      --- In Michalak@yahoogroups.com, "jmbell1" <smallboatdesigner@...>
                      wrote:
                      >
                      > --- In Michalak@yahoogroups.com, Rob Rohde-Szudy <robrohdeszudy@>
                      > wrote:
                      > >
                      > > What Kenneth said. AF4 actually IS a bit of a speedster, if you
                      have
                      > the stomach to push it that fast. Jim had his up to 20 mph testing
                      it
                      > with an 18hp motor.
                      >
                      >
                      > My AF4 could run 22.5 mph (GPS) at WOT with a 15 HP motor. I ran a
                      25
                      > HP motor for a short period of time and it would do an honest 30
                      mph.
                      > It was happiest at about 12-14 mph giving the best ride, fuel
                      economy,
                      > and handling/tracking at that speed. As others have said, AF4 is
                      > supposed to be a fairly fast boat. A better choice for a slow boat
                      > would be either to start with Jim's ELECTRON, or to take a sail
                      boat,
                      > delete the rig, and add power.
                      >
                    • John Bell
                      Depending on load, 10 will get you 16-18 at WOT, but cruise nicely at 12. Good choice.
                      Message 10 of 12 , Jun 14, 2006
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                        Depending on load, 10 will get you 16-18 at WOT, but cruise nicely at
                        12. Good choice.

                        mrusson wrote:
                        > So a good little 10 HP outboard may get her to 10-12 Mph....which
                        > would be ideal really. I guess i'll start hunting for a 10 HP
                        > outboard......
                        >
                        > MRusson
                        >
                        >
                        >
                        >
                      • Rob Rohde-Szudy
                        I think you re on the right track. If you re the slightest bit mechanically inclined, the Late 50s through very early 70s OMC outboards are quite easy to
                        Message 11 of 12 , Jun 15, 2006
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                          I think you're on the right track. If you're the slightest bit mechanically inclined, the Late '50s through very early '70s OMC outboards are quite easy to work on and quite cheap to buy. I've found Max W's Duckworks articles to be right on the money. Better yet, his book will be out soon. --Rob


                          by: "mrusson" mrusson@... mrusson
                          Date: Wed Jun 14, 2006 8:07 am (PDT)

                          So a good little 10 HP outboard may get her to 10-12 Mph....which
                          would be ideal really. I guess i'll start hunting for a 10 HP
                          outboard......

                          MRusson


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