Choosing the best marine hull for an autonomous boat

Discussion in 'Boat Design' started by Anelito, Aug 6, 2018.

  1. Anelito
    Joined: Aug 2018
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    Location: Italy

    Anelito Junior Member

    Hi everyone,
    for a university project I need to build a hull of 1.2m length able to withstand harsh marine environment, strong currents and waves while traveling at a low speed, ~2 knots. Useful extra requirements would be a very good stability and ability to recover from capsizing.
    The hulls I found so far are mainly for RC speed boats and are totally incompatible with my requirements.
    [​IMG]
    The one in the picture is well suited for my needs, also thanks to the weighted keel and can recover from full 180° capsizing.

    Do you have any similar model with construction plan or a hull to suggest that can satisfy my requirements?
    For the building process I'll use a CNC to mill a block of insulation foam and cover it with fiberglass and polyester resin with a finish of marine gelcoat.

    Thanks for the help
     
  2. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    I won't do your assignment for you. Do more research.there are many similar threads in this forum. Read them.


    Good luck
     
  3. Anelito
    Joined: Aug 2018
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    Anelito Junior Member

    Well actually it's not an assignment rather a self-aided project and being an electronics engineer my focus is on the electronics and software side to ensure a reliable and self-sufficient propulsion system. For the hull, since I am not a naval architect, I would prefer to find something already done in a build plan.
    Unfortunately I have seen dozens of such build plans and there is no trace of a hull for my specific requirements, since most are just for speed or sailboats.
     
  4. Blueknarr
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    Blueknarr Senior Member

    Good to hear that it is not a school assignment.

    You need to give us a much more detailed Statement Of Requirements. Are you intending to stalk and photograph wild hippopotamus or autonomous circumnavigation?

    2 knots is very slow. Ocean currents often exceed 5 knots and tides can run faster than 10 knots. I don't know how fast hippopotamus swim.
     
  5. Anelito
    Joined: Aug 2018
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    Anelito Junior Member

    The aim is to sail across the Mediterranean Sea using a combination of solar power and thermoelectric generator (converting waste heat from the motor and ESC).

    The requirements are as follows:
    - sturdy design able to withstand sea waves and harsh marine conditions;
    - ability to self recover from capsizing;
    - low profile to avoid wind drag.
    I would also add minimal drag in water as an added point but that’s actually conflicting with the other points above. It shouldn’t be too heavy anyway, otherwise it won’t be autonomous energy-wise.

    For the propulsion I’m using two 10V 960kV brushed motors with a five-blade propeller, either 3D printed in ABS or made out of steel.
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    What does the world gain from these autonomous "boats" ? Just seem like unnecessary navigation hazards for small manned boats. Do the owners leave their contact details on board, in case they cause damage ?
     
  7. Anelito
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    Anelito Junior Member

    The boat uses AIS to perform path replanning in case of a possible intersecting route, and it is equipped with navigation light as well as a visual obstacle avoidance system to steer in case of floating objects and small boats detected.

    The sea is a very useful test bed for space technologies as it can offer a huge range of diverse environmental conditions and challenges while being quite easy to access.
     
  8. BMcF
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    BMcF Senior Member

  9. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    The short answer appears to be "No", we have no plans.
    I'd look to the radio controlled boat world for what you seek.
    Is draft an issue?
    If not, then go deep and put batteries down low.
    Many such craft have been built.
    Semi submersibles seem a good way to go.
    Good luck, post pictures.
     
  10. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    You'd think national security people would not be happy with autonomous boats lurking around.
    What kind of space technologies might this help?

    It would help to know how big the waves and how much the winds and how fast the currents, plus weights of all the equipment to be on the boat.

    Are you going to control this boat or just let it loose and see where it goes?
     
  11. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Much better SOR, but still some questions
     
  12. Anelito
    Joined: Aug 2018
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    Anelito Junior Member

    Currently submersible ROVs are being tested in the Antarctic to be employed in future exploration missions, for instance to explore Jupiter's icy moon Europa. That is just a simple example on technologies developed on Earth and then ported into space, same for terrestrial ASV.

    Anyway, the boat is completely autonomous and I still have to plan a route long enough to acquire enough data and, at the same time, away from commercial routes (which will be a challenge as the Mediterranean Sea appears to be extremely trafficked).

    My energy budget is very low, since on such a small model I managed to mount semi-flexible panels up to 110W together with a MPPT charge controller.
    The Peltier waste heat recovery system has to be tested, I expect it to be able to power the navigation light only, which is a couple of 3W white LEDs.

    Energy-wise, these are the elements to be powered:
    • Engines: at 12V full throttle 123W (x2)
    • Companion computer and piloting uC: 2.5W + 2W
    • Navigation lights: 3W (x2)
    • Marine sensors: 60W *used once every 5mins
    • Camera and AIS receiver: 1.5W + 2W
    TOTAL: 320W
    I omitted counting the servomotor used for rudder positioning as it is activated every 10 minutes to avoid extreme wear.
    It is also worth saying the boat can automatically switch between three different power saving statuses, gradually deactivating units to save power, starting from marine sensors.
     
  13. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Either my understanding of your energy budget explanation is faulty; or you have only 112w of input driving 320w of demand!
     
  14. Anelito
    Joined: Aug 2018
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    Location: Italy

    Anelito Junior Member

    That's correct, but the 60W used by the marine sensors are quite negligible due to their random activation. Secondly, as I am unsure which type of hull to use, motors will probably change, I took their values from previous calculations on a double-sized boat, 2.4m in displacement.
     

  15. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Ok peak demand exceeds input.
    How about daily demand?
    Allowing for clouds, 10 hours of solar provides 1100 w per day. What will be the total daily usage of the continuous and sporadic electronics? The difference is your pulpution potential. How long can motors run at 75%.

    Between translation and me not being electrical engineer, I hope correct terms or at least understandable. I fear insufficient power to go anywhere.

    I know you're not a navel architect because you gave displacement as length. It is a measurement of weight. So KG not Meters. How heavy are moters, batteries, electronics, solar panels - everything?!
     
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