Engine well - fore or aft?

Discussion in 'Boat Design' started by Jon E, Sep 2, 2017.

  1. Jon E
    Joined: Jan 2005
    Posts: 54
    Likes: 3, Points: 8, Legacy Rep: 22
    Location: Norway

    Jon E Junior Member

    I have got an old 22' sailboat hull that i will convert to a electric motor boat. I plan to remove the mast and keel entirely, and replace the weight with batteries. Boat weight 650 kg include keel weight (250 kg).

    Any thoughts what is the best placement of the engine (Torqeedo Cruise 2 kw)? The original configuration is hard to control downwind.

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    kranringen2.jpg kranringen3.jpg

    A link to the boat class rules: Norsk Andungeklubb - KLASSEREGLER http://www.andunge.no/website.aspx?displayid=1263
     
  2. alan craig
    Joined: Jul 2012
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    Location: s.e. england

    alan craig Senior Member

    Looks like the original rudder position doesn't have much of a moment; quite close to the centre of the boat.
    Would you consider chopping off the pretty canoe stern and making a small transom? Best for control, worst for looks. Best for looks would be a well entirely below the waterline aft. There are pods and electric saildrives available which would avoid the drag of a well, but that would increase the draft.
    Are you going to put some sort of cabin on it?
     
  3. Jon E
    Joined: Jan 2005
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    Location: Norway

    Jon E Junior Member

    No, just a couple of seats.
     
  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Place the well just forward of station 1, say about 100mm, maybe 150. Make it wide enough so you can rotate the motor, so you'll need to work up some templates to get a good idea of the swing space you'll need. This will eliminate the the need for a rudder and provide vectored thrust steering, which is far superior. Make the well just big enough to house and permit the motor to swing through say 45 degrees (each way). Rather than tilting it up to get it out of the water, consider a sliding mechanism of some sort, which will permit a much smaller hole in the hull shell.

    I dew up a revised rudder for one of these several years ago, when a client (Finland) pick one up cheap and wasn't intending on racing. It seems they all steer lousy, so I designed a trapezoidal plan, which much more "meat" at the bottom, considerably less at the root and it steered much better.
     
  5. Jon E
    Joined: Jan 2005
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    Location: Norway

    Jon E Junior Member

    Like this?
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  6. BlueBell
    Joined: May 2017
    Posts: 91
    Likes: 1, Points: 8
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Or a little further forward.
    May as well get rid of the rudder, less wetted area.
    You may want to taper the end of the skeg.
     
  7. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Maybe another 150mm farther forward than you've showin. The idea it to retain the combing, while still having enough room for the motor to slide up and out.
     
  8. Kerstin
    Joined: Nov 2017
    Posts: 1
    Likes: 0, Points: 1
    Location: Marstrand, Sweden

    Kerstin New Member

    Hej Jon! I can easily understand your fascination for the idea of converting your Andunge but find it sad because it is a very nice boat to sail. In Sweden the wooden boats have been popular for a long time with new ones still being built. The main andunge race in Sweden has been won by plastic hulls the last two years and there seems to be a growing demand for GRP boats. Why don't you consider selling your boat if it is in reasonably good condition and use another hull for your project? Otherwise good luck!
    andunge https://andunge.wixsite.com/andunge
     

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  9. JSL
    Joined: Nov 2012
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    Location: Delta BC

    JSL Senior Member

    is the propeller going to have sufficient diameter (blade area) to push (and maneuver) the boat reasonably efficiently???? 22' boat I would guess you need at least 14" -16" dia.
     

  10. xellz
    Joined: Jul 2017
    Posts: 63
    Likes: 3, Points: 8
    Location: Japan

    xellz Junior Member

    When i was looking for electric boats already on water i saw similar conversion to yours. But 5kw brushed motor as inboard was used, 21ft, 5knots cruising speed at ~1kw. Looks like fun boat, torqeedos aren't cheap, might be worth going for inboard conversion? For some reason i really don't like outboards just for aesthetics.

     
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