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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    Anelito Junior Member

    HJS
    Does it have a keel? It looks nice, what are the deck dimensions?
     
  2. HJS
    Joined: Nov 2008
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    Location: 59 45 51 N 019 02 15 E

    HJS Member

    As I see it, it is a delicate task to create harmony between the deck area for the solar cells, the instability in the cantilevered position, the minimum possible total weight and optimal length.
    I have no experience at all about this type of craft. My suggestions are only based on calculations and experiences from model boats and full-scale boats of all kinds.

    JS
     
  3. JamesG123
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    JamesG123 Senior Member

    Clear... anything will rapidly get hazed at sea. Solar panels do not need to be in a flat horizontal sheet. In anything but a flat sea, this vehicle will be pointing at random angles to the sun all the time. The entire outer surface above the (notional) waterline of it should be encrusted with PV cells.

    Fretting over details of hull shape on a vehicle of this diminutive scale and application is silly.
     
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  4. HJS
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    HJS Member

     
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  5. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    Anelito,

    We need a clear, prioritized SOR (Statement of Requirements).
    What do you need the vehicle to do, exactly, when, where, and why.
    Perhaps you don't know, but you are inspired to do better than your colleagues did in their build.
    6 pages of speculation is just confusing when you don't know, or can't clearly define, what you need.
    Designing what will best suit your needs is far better than picking an existing hull design.
    We can't help you to get where you're going if you can't define where you want to go.

    And then there is the design spiral...
     
  6. JamesG123
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    JamesG123 Senior Member

    Please do. "Over think" is a very common problem, esp. when as "BlueBell" states, you don't have all the problems to the OP's answer. ;)
     
  7. Anelito
    Joined: Aug 2018
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    Anelito Junior Member

    Okay I will try to recap the whole project.

    Aim
    Test a collision avoidance system for autonomous boats to create a COLREG-compliant robot over a long route in a real case scenario.

    Objective
    The boat needs to move autonomously from point A to point B harvesting energy from the environment (just solar power for now) and transmit telemetry data back to the GCS.

    Requirements
    The hull should be designed to withstand harsh sea conditions, big waves and currents as well as recover from capsizing.
    The inner space will have to host two watertight boxes measuring 10 x 10 x 20 cm and a battery of 1.1 Kg and size 16.5 x 5.5 x 6.3 cm.
    Deck usable surface should be at least 0.5 m^2 in order to host 21 cells and provide 100W at max.
    LOA within 1 and 1.5 m, average speed between 1 and 2 knots.
    Total payload weight, including electronics, batteries, solar cells and motor(s) is 2 Kg at max.
     
    Last edited: Aug 17, 2018
  8. JamesG123
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    JamesG123 Senior Member

    No one requested simple.
     
    Last edited: Aug 17, 2018
  9. Anelito
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    Anelito Junior Member

    I edited my answer to include extra elements. However, the whole project is summarised in two simple lines, as being autonomous and solar-powered means there will have to be enough deck space to host a number solar cells able to provide enough energy to charge onboard batteries and keep the boat systems alive.
     
  10. portacruise
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    portacruise Senior Member

    This has been done before with fairly successful results, with other autonomous boats! Simplest is to copy the most successful design that is closest to the size of your boat. Experiment with it for a Maybe a year, and then tweak it to get it perfected. Why spend the time to reinvent the wheel, without knowing what kind of Road you will be going on?
     
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  11. Anelito
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    Anelito Junior Member

    That can be a nice approach, however exulting SeaCharger and SolarSurfer (a surf table), other designs are not open source.
     
  12. JamesG123
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    JamesG123 Senior Member

    There is nothing proprietary about the scale boats that they used. Nor even in the electronic systems they developed. Its all pretty much plain jane RC and autonomous operation stuff. The code will be the important/valuable part. If that is your actual focus of this project, don't even worry about what it looks like, Just build a stout boat-ish thing that facilitates your learning and development process. You can always transplant your electronics into something sexy later.

    Don't try to be excessively clever, you just want reliable and Murphy-proof. If you notice most of these USV competitions or record attempts, the vehicles fail because either they are built too flimsy (because they are modeled on RC boats or worse, full sized boats), or their software fails (because they spent too much effort on making the hardware pretty?).

    This isn't RC boat.net or a drone forum, so there is limited help you are going to find here on the electronic aspect of the project, which is really going to be the hard part. Just pick an off the shelf RC boat, or even just a PVC sewer pipe as a model/mold and get going. Ask those specific detail questions because that is all you need from here.
     
  13. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    So, what is your average 24 hour electrical draw?
    And your average full-sun hours each day during your season of operation?
    Your weather service may have that info, it's very important for you to have
    unless you're okay with the vehicle going dead occasionally.
     
  14. Anelito
    Joined: Aug 2018
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    Anelito Junior Member

    4W of electronics and 3W of navigation lights, so if I manage to get 100W of panels the remaining power will be dedicated to propulsion.
    I plan to test the boat in winter with small trips of a couple of hours, and in that period I expect to have 10 hours of sun. During early summer, the period I'd like to set the boat free, it can get up to 14h of sun.
    I would strongly prefer cutting out the engine or reducing speed rather than going completely off.
     

  15. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    Well there you go.
    Just write a program that does that and you're away.

    What is your average 24 hour electrical draw?
    And your average "full-sun" hours each day during your season of operation?
     
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