Choosing the best marine hull for an autonomous boat

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

  1. BlueBell
    Joined: May 2017
    Posts: 1,163
    Likes: 208, Points: 63
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Not a good idea.
    Think about it.
     
  2. Anelito
    Joined: Aug 2018
    Posts: 46
    Likes: 0, Points: 6
    Location: Italy

    Anelito Junior Member

    I can think of extra drag, but I will make the keel detachable for an easier storage; then it will be fully solid without any air inside.
    What about the A-Tirma hull? Do you think it can be a good starting point for a prototype?
     
  3. BlueBell
    Joined: May 2017
    Posts: 1,163
    Likes: 208, Points: 63
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    A-Tirma is a nice looking little boat.
    But you are still searching for existing hulls rather than building what you need.
    Why keep looking for something when you can make exactly what you need to serve your purposes?
    If 90 watts of power isn't enough, build longer, and wider if necessary, to meet your needs.

    Easy storage is one of your priorities?
    If it gets destroyed, or doesn't do what you want it to, then it's not worth storing.
     
  4. portacruise
    Joined: Jun 2009
    Posts: 1,112
    Likes: 32, Points: 48, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    Water cannot be used as ballast for a keel, it is the same density as the surrounding water, you need something much heavier.

    If you want to save weight, you could use a smaller amount of weight at the very end of a longer, lightweight carbon fiber keel to give you the required leverage.

    I agree with CDBarry that a kayak Hull is quite enough, since the speed will be so low. If you can find a good used child's kayak made of material that is easily worked, altered, and sealed, that would be ideal and low cost.

    PC
     
  5. JosephT
    Joined: Jun 2009
    Posts: 856
    Likes: 106, Points: 43, Legacy Rep: 218
    Location: Roaring Forties

    JosephT Senior Member

    Just now reviewing this interesting project. My my own past research in the past the wing sail for the autonomous mini ocean drones would be your best bet for primary propulsion. The solar + battery power for the motor could power the boat for some time until sea life seizes up the prop, which will happen in due time. Anything below the waterline (especially moving parts such as a propeller) is fair game for barnacles, nets, etc.

    e.g.
    [​IMG]

    The sail drone below, from what I have studied, is among the latest state of the art designs and has achieve some good distance testing. You may be able to scale it down to suit a less complex mission if the instruments you are using are suitable. Note the bright color makes it easy for passing vessels to spot and avoid. Give them a shout and perhaps they can collaborate with you on your project.

    Ref: Saildrone https://www.saildrone.com/

    [​IMG]
     
  6. JosephT
    Joined: Jun 2009
    Posts: 856
    Likes: 106, Points: 43, Legacy Rep: 218
    Location: Roaring Forties

    JosephT Senior Member

  7. Anelito
    Joined: Aug 2018
    Posts: 46
    Likes: 0, Points: 6
    Location: Italy

    Anelito Junior Member

    SeaCharger used an anti-vegetative paint to avoid barnacles and other sea life to grow on the hull; there should also be non-polluting alternatives as most of these paints contain heavy metals.

    I am pretty sure to go for the mixed solar+wingsail approach, because the two compensare pretty well. The engine can work when there is almost no wind (and calm sea) whereas the wingsail can opt in when the wind gusts get stronger.

    Having read the A-Tirma design paper, it seems to contain pretty much all my SoR, that’s why I think it is suited for my needs.
     
  8. CDBarry
    Joined: Nov 2002
    Posts: 790
    Likes: 30, Points: 28, Legacy Rep: 354
    Location: Maryland

    CDBarry Senior Member

    You will probably want a two blade prop, btw. Compare efficiency given large allowable diameter. A Kort nozzle would be appropriate if you have a limit on diameter, If your u/w components are copper bearing or copper plated, they won't foul so much.

    There is a lot of literature on autonomous boats now, check it out. Paul Miller at the Coast Guard Academy has done a lot in this area. As I recall, there are various contests among colleges.
     
  9. Anelito
    Joined: Aug 2018
    Posts: 46
    Likes: 0, Points: 6
    Location: Italy

    Anelito Junior Member

    I don’t have any limit for the boat propeller size, but considering the LoA will be between 1.3 and 1.5m there’s an obvious limit to its size.

    Interestingly, I’ve seen pictures of turbulatots applied to sailboat keels and wing sails (mainly catamarans). Is it a useful feature? On airplanes there’s a necessity to break the laminar flow but on (slow) sailboats?
     
  10. JamesG123
    Joined: Mar 2015
    Posts: 655
    Likes: 75, Points: 28, Legacy Rep: 10
    Location: Columbus, GA

    JamesG123 Senior Member

    No there isn't if you aren't thinking inside the box.

    Reynolds numbers
     
  11. BlueBell
    Joined: May 2017
    Posts: 1,163
    Likes: 208, Points: 63
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    The ocean is huge but you're limiting the vehicles LOA for easy storage?
    It's going to be designed for the open ocean, why not store it outside?
    Put a small fan inside to ventilate and circulate and through a tarp over it.
    Seems silly to restrict it's size due to storage issues don't you think?
     
  12. JamesG123
    Joined: Mar 2015
    Posts: 655
    Likes: 75, Points: 28, Legacy Rep: 10
    Location: Columbus, GA

    JamesG123 Senior Member

    Have you seen how small the cars are in Italy? ;+D
     
    BlueBell likes this.
  13. Anelito
    Joined: Aug 2018
    Posts: 46
    Likes: 0, Points: 6
    Location: Italy

    Anelito Junior Member

    Haha well depends which city you go to.

    I asked the A-Tirma boat designers for some more detailed hull measures, I'll try to determine how many solar cells I can fit on the deck. Apparently there would also be space on the sides, just above the water line.
    This is a rough scheme of how should it look like.
    [​IMG]
    I will use only one wingsail and add an extra third fin to host the propeller and a rudder.
     
  14. BlueBell
    Joined: May 2017
    Posts: 1,163
    Likes: 208, Points: 63
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    "I asked the A-Tirma boat designers for some more detailed hull measures"
    They are surf skis.
    Lots of statistics available for them.
    They're usually 20 feet long (6.5m) with a design weight of ~220 pounds (100kg).

    "Apparently there would also be space [for solar cells] on the sides, just above the water line."
    If you mildly dome the top of your vehicle, you can panel to the water line, yes.
    Your MPPT charger/controller will accommodate this layout quite nicely.
    This has been mentioned several times already.
     

  15. Earl Boebert
    Joined: Dec 2005
    Posts: 377
    Likes: 47, Points: 28, Legacy Rep: 302
    Location: Albuquerque NM USA

    Earl Boebert Senior Member

Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.