Stern thruster placment

Discussion in 'Boat Design' started by comfisherman, Mar 30, 2024.

  1. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

    As our price drops and labor competition goes up, my type of fishing is starting to look for more and more ways to automate. Or at least shuffle equipment and work on to the captain.

    One thing we've been playing with is stern thrusters to aide in net hauling. We've traditionally had a skilled individual in a skiff working like a mini tug manipulating the boat around the gear. As time has gone on its getting harder to find competent skiff men. The idea is to put a series of thrusters in to allow vessel manipulation in conjunction with the main to decrease the need of the support vessel.

    Conundrum is where to put one in the stern on a boat that hauls nets up its stern. Early attempts have been to fair in small diameter thrusters on the transom. It works, but in light condition it's east to aspirate the tunnel.

    Have recently noticed the Norwegian and north sea boats are adding stern thrusters in the aft keel/skew region just in front of the prop. Seems like a weird place, however it appears quite common. Posted a Pic of a drawing lifted from a Google search of an example.

    Seems like a bad place to introduced laminar disruption, maybe I'm over thinking it. What's the collective think of a tunnel thruster just before the prop?
     

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  2. mc_rash
    Joined: Aug 2020
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    mc_rash Senior Member

    In my opinion resistance wil increase a little but not as much as maneuvreability especially in a harbour full of fishing boats and too less (skilled) people. You might wanto run a costanalysis added resistance vs. less cost without renting a tug (or skiff, ...).
     
  3. jehardiman
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    jehardiman Senior Member

    Pretty much what Mc_rash said. If going hard ahead/astern you might get a starvation issue on the thruster, and probably more noise/vibration on the main overall, but otherwise I'll bet it was put there to ease cabling/plumbing runs.
     
  4. comfisherman
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    comfisherman Senior Member

    Cabling is pretty easy to run anywhere, just some stainless and a tube bender. Just seems like it's near the worst place for introducing a disturbance.

    Hard to place a large thruster, just s bit surprised it's in front of the prop. Guys spend so much time fairing bowthrusters, like it would be much more pronounced on the leading side of the prop.
     
  5. jehardiman
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    jehardiman Senior Member

    You do not want electrical fittings in the wet bilge, you do not want to have to access under the shaft....
     
  6. comfisherman
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    comfisherman Senior Member

    Fair point under the shaft, definitely cleaner and deeper than transom mounted. Think those are all hydraulic, and way outta the bilge.

    I'll have to try emailing some folks to see if it's a noticeable input of messy after flow with a deeper gear and slower prop.
     
  7. jehardiman
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    jehardiman Senior Member

    As Mc and I opined, for those box boats, I doubt you would notice it. A more slippery hull may have measurable amounts, but for most hulls I've worked with, thrusters in the skeg ahead of the prop did not make a significant difference to operations, just noise and vibration.
     

  8. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

    Good to know. I've room for a much bigger thruster with a shorter tunnel in my skeg.
     
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