Propulsion Options for a 5t utility barge

Discussion in 'DIY Marinizing' started by NicB, Nov 18, 2022.

  1. baeckmo
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    baeckmo Hydrodynamics

    The bow and aft shapes are double curvature, which means a lot of extra work with no extra benefit. I suggest you look at simpler shapes.
     
  2. NicB
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    NicB Junior Member

    Thanks, Baeckmo

    What shapes would you go with?
     
  3. baeckmo
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    baeckmo Hydrodynamics

    Is the main hull already built?
     
  4. NicB
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    NicB Junior Member

    Yes it is, we are adapting this structure.
    upload_2022-11-25_13-3-25.png
     
  5. baeckmo
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    baeckmo Hydrodynamics

    Ok, then I will come back with a suggestion, based on the geometric elements already used.
     
  6. NicB
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    NicB Junior Member

    Many thanks, Below are the dimensions here incase they are useful
    upload_2022-11-25_13-20-28.png
     
  7. portacruise
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    portacruise Senior Member

    I don't see how the "V" will help anything hydrodynamically, but maybe I'm just missing something.. If the water touches at the middle, the V might tend to act like a cup, so as to drag/ slow things down. Seems like you need a point there instead to reduce water drag and cut wave slamming. If the V is always above water surface, it probably doesn't make any significant difference to the remaining aerodynamic aspect, and it *sacrifices* the platform cargo space compared to just running square or having a point? Two engines would presumably increase propulsion complexity but maybe increase overall reliability (and give better turning radius for maneuverability compared to a forward power only twitchy long tail with the prop at the end of a lever), especially if the whole barge can be instantly converted and reasonably powered / maneuvered with just a single engine, should the other go out. Two engines give better maneuverability for docking a massive cargo compared to a rudder, especially at very low speeds. JMHO.
     
    Last edited: Nov 26, 2022
  8. gonzo
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    gonzo Senior Member

    That is looking much better.
     
  9. NicB
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    NicB Junior Member

    Thanks, Portacruise.
    I guess I am hoping the V helps hydrodynamically, in the sense that in the event of encountering a wave that would have slammed into the forward mid-section the V moves the point of impact further aft and requires a larger wave for this event to occur. Agreed there is a point where V would act as a break, but it would be expected that the helmsman adjusts course to avoid this event.
    Point noted on the loss in cargo capacity, but at this time the vessel only needs to accommodate the pile-driving rig and I figured, the V shape would help with the stability of the pontoon, by allowing the rig to operate closer to the center of the vessel.
    Thanks for the pointers on the advantages and disadvantages of 2 engines.
     
  10. NicB
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    NicB Junior Member

    Thanks, Gonzo
     
  11. baeckmo
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    baeckmo Hydrodynamics

    Ok, since you already have used rolled panels with a constant radius 1000 mm, I suggest you stick to rolled segments and flat surfaces as shown below. Light blue shows rolled pieces and red flat ones. The stem angle is 60 degrees and the aft bottom 20 degrees to horizontal. I'd recommend that you fit a triangular fin under each bottom panel aft for directional stability.

    Although there are some knuckles in the waterline shapes, this configuration will have considerably lower resistance and better behaviour than the original square box.
    Good luck and fair winds....!
     

    Attached Files:

    DogCavalry and gonzo like this.
  12. NicB
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    NicB Junior Member

    Great stuff, thanks very much Baeckmo!
    Very doable design!
     
  13. NicB
    Joined: Nov 2022
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    NicB Junior Member

    Update,

    Hi Everybody, thanks for the help on this, just an update on where we ended up.

    Turns out the light weight of the base vessel was closer to 8.5t once re-evaluated on-site, we took the weight up to about 30t all in.
    We ended up using a secondhand 100hp Ashok-Leyland engine as it was available on short notice in the country and put a 24"x 18" 3-bladed prop onto a centrally mounted in a 3rd hull.
    Spuds were made from borehole drilling shafts.
    The vessel was just needed for a one-off job and not intended to be in regular use.

    Some photos:
    upload_2023-5-8_9-33-4.jpeg
    upload_2023-5-8_9-33-16.jpeg
    upload_2023-5-8_9-33-33.jpeg
    upload_2023-5-8_9-34-32.jpeg
    upload_2023-5-8_9-40-51.jpeg
    upload_2023-5-8_9-50-50.jpeg
    upload_2023-5-8_9-52-12.jpeg

    The lake level rose fast and early (Cyclone Freddie helped too) so we didn't get as much time on the beach as we thought we would.

    upload_2023-5-8_9-54-32.png

    Doing what she was built to do.

    Thanks again for the help Everyone

    @baeckmo your suggested cones worked extremely well both at fabrication and functionally, we didn't install aft to save money and time, considering that it's not going to be in regular use
     
    Last edited: May 8, 2023
  14. Ad Hoc
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    Ad Hoc Naval Architect

    Pictures....please??? :D:D:D:D
     

  15. NicB
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    NicB Junior Member

    Edited with picture ;-)
     
    DogCavalry and Ad Hoc like this.
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