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Jukebox 3 update

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  • Eugene Dixon
    Hey Nels are you out there? all bulkheads/frames are built, waiting for final sanding and paint. The question is the transom {its already built} JM does not
    Message 1 of 7 , Mar 25 7:59 PM
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      Hey Nels
      are you out there?
      all bulkheads/frames are built, waiting for final sanding
      and paint.
      The question is the transom {its already built} JM does not give dimensions for motor Hts.
      What I have done is to raise cut out portion 0f transom to level of angle of side frames,and move motor board inboard {Used 2 x 10]
      am going to use commercial motor mount offset to one side of transom,
      use ruder for all steering and mount for mizzen to opposite side.
      Any comments or suggestions?
      Eugene
    • prairiedog2332
      Hi Eugene, Not sure why you would raise the cut out portion. Seems the size of the cut- out is not shown on the plans is it? The motor board ht. is not given
      Message 2 of 7 , Mar 26 6:42 AM
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        Hi Eugene,

        Not sure why you would raise the cut out portion. Seems the size of the
        cut- out is not shown on the plans is it? The motor board ht. is not
        given because it depends on the length of the leg of your motor. Fot a
        15" leg the board height is going to be pretty low down on the transom.

        If you look at sheet 1 you will see that at a full load (1310 lb.) the
        bottom of the stern is still about 6" above the water surface and the
        top of the board about 9" above the bottom. So that is maybe the correct
        height for a 15" motor leg?

        Sailboats with the amount of rocker Jim's designs have are a bit tricky
        when it comes to motors. In waves of any size the prop might pop out if
        the OB mount is too high or get washed by following waves if too low.
        That is why so many sailboats have extended legs.

        My plan is to do what Gary Blankenship did with his Toon2 "Oaracle".
        First photo here. (Ignore the unpainted plywood addition - that is just
        his trailer tail light board.)

        http://www.duckworksbbs.com/plans/jim/frolic2/index.htm
        <http://www.duckworksbbs.com/plans/jim/frolic2/index.htm>

        Motor opening on centerline. Rudder offset to port with a tiller
        extension added. Tube for mizzen mast to starboard. Steer with rudder
        even when motoring.

        I would also bolt the motorboard to the outside of the transom so it
        could be removed and adjusted if a different motor is obtained later.
        Also looks like Gary left the top of the cut-out open so easier to tilt
        the motor and work on it. If it works for him I think it would work for
        us!

        But I am not sure of the advantages of a commercial motor mount? Which
        one are planning to use?

        Nels
        --- In Michalak@yahoogroups.com, "Eugene Dixon" <edixon193941@...>
        wrote:
        >
        > Hey Nels
        > are you out there?
        > all bulkheads/frames are built, waiting for final sanding
        > and paint.
        > The question is the transom {its already built} JM does not give
        dimensions for motor Hts.
        > What I have done is to raise cut out portion 0f transom to level of
        angle of side frames,and move motor board inboard {Used 2 x 10]
        > am going to use commercial motor mount offset to one side of transom,
        > use ruder for all steering and mount for mizzen to opposite side.
        > Any comments or suggestions?
        > Eugene
        >




        [Non-text portions of this message have been removed]
      • John Nystrom
        Gene, Jim has a discussion of transom height adjustment vs. motor shaft length and cavitation plate depth in his book.  Did you buy the book?  A bargain, and
        Message 3 of 7 , Mar 30 8:59 AM
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          Gene,
          Jim has a discussion of transom height adjustment vs. motor shaft length and cavitation plate depth in his book.  Did you buy the book?  A bargain, and my favorite 'Boatbuilding for Boneheads' volume out there.
          John Nystrom


          [Non-text portions of this message have been removed]
        • prairiedog2332
          Jim writes in part: (page 109) The usual advice for a small motor is that the cavitation plate should be about 1 below the bottom of the boat. So a
          Message 4 of 7 , Mar 30 11:28 AM
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            Jim writes in part: (page 109)

            "The usual advice for a small motor is that the cavitation plate should
            be about 1" below the bottom of the boat. So a 'short-shaft' motor
            usually needs a 15"-deep transom on the typical powerboat. And a
            'longshaft motor' usually needs 20". "

            By "typical powerboat" I think he means a boat where the transom bottom
            is touching the water when at rest. And transom height I think he means
            to top edge of the motorboard - not the top edge of the transom.

            The problem is that Jukebox3 is not a "typical powerboat". Due to it's
            rockered hull the transom bottom is not touching the water when it's at
            rest but may be 6" or so above the water. So to get the cavitation plate
            1" below the water the motorboard top edge has to be lower than with a
            typical powerboat. The cavitation plate might have to be even lower
            than 1" to allow for when crew go forward to handle anchor and dock
            lines for example.

            He also mentions "Transom Tilt" on the next page. Commonly being 15
            degrees. If the transom is vertical then the motorboard often has the 15
            degree outward angle slope cut into it on a sailboat. This is because
            the location of the prop is below the location of where it's power
            thrusts against the boat which is at the OB clamp. So this leverage
            tends to push the bow down and the angle holds it level. Jim says this
            is not even noticeable with a small OB but it might be if you are
            planning to use a long-shaft motor with a high-thrust prop?

            If you put the 15 degree angle in the motorboard then it can only be
            attached to the outside of the transom obviously.

            Nels


            --- In Michalak@yahoogroups.com, John Nystrom <johnduck134@...> wrote:
            >
            > Gene,
            > Jim has a discussion of transom height adjustment vs. motor shaft
            length and cavitation plate depth in his book. Did you buy the book? A
            bargain, and my favorite 'Boatbuilding for Boneheads' volume out there.
            > John Nystrom
            >
            >
            > [Non-text portions of this message have been removed]
            >
          • prairiedog2332
            Corrections to previous post - which I will delete. Forgot to add the word NOT and also some spelling errors:-) ... might ... so.) ... deeper ... same ... that
            Message 5 of 7 , Mar 30 2:50 PM
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              Corrections to previous post - which I will delete. Forgot to add the
              word NOT and also some spelling errors:-)


              --- In Michalak@yahoogroups.com, "prairiedog2332" <nelsarv@...> wrote:
              >
              >
              > Further this post below - on further thinking it may be useful for new
              > builders to really consider painting a "boot stripe" on their hull. I
              > describe how to do that in a previous post, but the best source of how
              > to it is in Payson's book, "Building the New Instant Boats".
              >
              > I think it is really most useful with a hull with considerable rocker,
              > like Jukebox3. The boot stripe gives a visual reference in keeping the
              > hull balance correct for best performance and also shows when you
              might
              > be getting overloaded or in fact may need more added ballast.
              >
              > If a hull like this is running bow up or bow down when underway it
              > effects both steering and hull speed.
              >
              > If looking for a motor for a hull the size of JB3 (20' waterline or
              so.)
              > it might be a good idea to consider a long-shaft as a viable option.
              > Especially if your motoring may involve some fairly large waves or
              > powerboat wakes. Better to have the cavitation plate going a bit
              deeper
              > at times and still keep the power head high enough to prevent waves
              > washing over it, rather than having the prop come out of the water.
              >
              > It might be an idea to add a protective skeg as well that is at the
              same
              > depth as the lowest part of the hull. And have the prop located so
              that
              > it does no extend further than the depth of the skeg. That way the
              skeg
              > hits bottom first in a grounding and may save a shear pin. If you ever
              > had a shear pin go when hitting a reef trying to fend off a lee shore
              under power that
              > is a scary experience. Been there done that. Motor over-reving and no
              > power to the prop!
              >
              > Michalak designed that on his Eisbox design, as well as the option of
              a
              > small drop board in the bow well to maintain forward steering in
              > cross-winds. This design also has an inboard rudder protected by the
              > skeg, but Jim was NOT that happy with it as he felt the draft was too
              much
              > for him. About 12" instead of 6". But if you motor a lot in a rocky
              area
              > and can live with that draft it seems like a designe worth
              considering.
              >
              >
              http://f1.grp.yahoofs.com/v1/0B52T7Zd6Kg19_ioJo0yPrrwMTsdDZ6kK_zFq06019B\
              \
              > pK3K7ynosezxT5ytut5aRlfb7Y7kedawfXTKsc88q/Eisbox.jpg
              >
              <http://f1.grp.yahoofs.com/v1/0B52T7Zd6Kg19_ioJo0yPrrwMTsdDZ6kK_zFq06019\
              \
              > BpK3K7ynosezxT5ytut5aRlfb7Y7kedawfXTKsc88q/Eisbox.jpg>
              >
              > Nels
            • John Nystrom
              Thanks for posting the complete information, Nels.  I m overseas and don t have the book with me. John Nystrom [Non-text portions of this message have been
              Message 6 of 7 , Apr 1, 2012
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                Thanks for posting the complete information, Nels.  I'm overseas and don't have the book with me.
                John Nystrom


                [Non-text portions of this message have been removed]
              • Eugene Dixon
                Hi All Have posted photos of my JB3 build in photoa under JB3 Traveler Please excuse unorganized mess, just learning camera software. Eugene
                Message 7 of 7 , Nov 12, 2012
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                  Hi All
                  Have posted photos of my JB3 build in photoa under
                  "JB3 "Traveler"
                  Please excuse unorganized mess, just learning camera software.
                  Eugene
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