Motor height for a displacement hull

Discussion in 'Outboards' started by boat fan, Jan 29, 2016.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    He is probably calling 20" short shaft. The 60hp high thrust Yamaha is a 20" motor only, according to the website.
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Hard to fathom why you'd have that kind of stern treatment.
     
  3. HJS
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    Location: 59 45 51 N 019 02 15 E

    HJS Member

    Pod design

    Put a streamlined pod directly above the watersurface. It is important that the bottom is completely horizontal and flat, otherwise may uncontrollable wave formation occur.
    This solution I have applied on all my past catamarans. The experience is based originally from my own catamaran, Fancy Free.

    JS
     

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  4. daiquiri
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    daiquiri Engineering and Design

    I see what you did there. Smart solution. :)
     
  5. boat fan
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    boat fan Senior Member


    Looks simple HJS , but I suspect the exact shape is the key here ?

    How is this marked out to get the correct curve / arc ?

    The other question is , does the horizontal flat face lie on the exact flat horizontal plane as the anti - ventilation plate ?

    Like daiquiri says , it appears to be a smart and rather elegant solution.
     
  6. HJS
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    Location: 59 45 51 N 019 02 15 E

    HJS Member

    Just shape the pod like a boat with a pointed bow and it will work.

    Since we do not know how the waves in the tunnel will be formed at different speeds, we can not say how it will work. These showed hulls has an odd shape that complicate it all. So it all becomes still just a guess. So be prepared to rebuild after a few trial runs under different conditions.

    Also be prepared to change the propeller to match the speed. This is very important to get it to work. Measure speed and check that the slip is within reasonable limits. On my own boat, I got to change the propeller three times before it worked. The speed increased from eight to twelve knots. Do not trust the sellers word.

    Good luck

    js
     

  7. Mr Efficiency
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    Mr Efficiency Senior Member

    You certainly need some kind of deflector ahead of the leg, above the highest splash plate. Otherwise you will have a fountain, plus the grease being washed out of the swivel tube.
     
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