Kort Nozzle Diameter (19A + Kaplan)

Discussion in 'Props' started by Callum Stark, Apr 29, 2021.

  1. Callum Stark
    Joined: Oct 2019
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    Location: UK

    Callum Stark New Member

    Hi,

    I am wondering what is the average full-scale diameter of kort nozzles (19A duct and kaplan propeller) for vessels such as tug and fishing boats? I have looked on the internet and can't find anything, so I am looking with someone who has some experience on this subject. Any reference would be appreciated as well.

    Kind regards,

    Callum
     
  2. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

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  3. Callum Stark
    Joined: Oct 2019
    Posts: 3
    Likes: 0, Points: 1
    Location: UK

    Callum Stark New Member

    Hi,

    Thank you for your answer. The reason I ask is because we are developing some new technology for such an application. However, most experimental tests are done at model-scale, around 250mm. I asked so that I could look at the performance change of the new technology also in full-scale because it may be different due to scale-effects.

    Kind regards,

    Callum
     
  4. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Junior Member

    Nozzle guy in the gulf only stocks nozzles in 60 and 72 inches.... everything else is custom fab.

    Smallest I've seen is 48, they were all the rage in both the Alaska and canadian Atlantic coast but fell out of favor as trawling declined and consolidated. Most are still present but on boats over 70 loa.

    Actually know if at least one nozzle boat going open wheel. A 58 that wanted to be able to spin on pots better for trailing.

    In tugs they made all kinds of sense, fishboats not so much.


    I'll never forget my first time at the helm of a nozzle boat..... like turning a train in a harbor. Triple rudders helped but catch on nets from appendages. Theoretically the articulating rudder could help, but I'd try before buy....
     
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  5. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Yeah, accelerating nozzles are pretty much limited to tugs and pushboats in the gulf/rivers, both of who want to spin as big a wheel as possible and don't have tuck up displacement issues. There was a whole move in Europe to move the draggers and stuff to nozzles because of the "interesting" choice of the EU and other fisheries to move to length regulation (U10) vice a more sane (speaking from a NA's perspective) fish hold volume. This lead to some really strange box limit boats that needed nozzles. As Ted Turner said "Even a turd is pointed on both ends".
     

  6. comfisherman
    Joined: Apr 2009
    Posts: 55
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    Location: Alaska

    comfisherman Junior Member

    We have similar such rules up hers, were not limited by volume like EU and Canada so our boats have much more fretboard and reserve buoyancy.

    Sadly it makes for a turd sandwich hydrodynamiclly.

    Several weeks back I had a conversation with an owner of a boat that went from a nautican to an open rudder. As the trawl season decreased and the pot season increased the inability to rapidly turn negated straight line benefits of the nozzle. It gave it more 3-5knot net towing speed but slowed the top end. If the fishery morphs it may require another change, I'm doubtful that nozzles will become a significant player in that class fish boat. Mainly due to the demise of the heavy torque fisheries in the political environment.

    Right now the trend is slightly more draft, a deeper ratio, and a larger wheel. Thankfully the only reasonable trend in fishing boats in a while.
     
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