Advice on hull design for solar-powered boat

DELFTship forum Hull modeling Advice on hull design for solar-powered boat

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    • #38717
      El Kroketto

      Hi everyone,

      I am planning to send a solar-powered, unmanned & autonomous boat (length max. 1.7m) out to onto the Atlantic Ocean. For more than seven months I have been working on the software and electrical parts, avoiding a reasonable hull design. I am neither a mechanical nor nautical engineer therefore your support would be much appreciated.

      One of the most popular types in the field of autonomous sail boats is a hull called MaxiMoop, created by the US Naval Academy. In a 2014 published paper they show two design approaches:

      The original design, built and tested in 2014

      Improved hull design

      Although this design is intended for sailing boats I think it is great for stability reasons: The ability to safely flip over after capsizing is crucial for a boat out on the sea far away from any human help. On the downside the deck does not offer lots of space for solar cells and every inch counts when harvesting energy. I do not intend to add any sails, only solar cells and a (small & max efficiency) motor.

      What hull design do you think would be the best for this project? Should I stick with the MaxiMoop, try to design it in DELFTShip and resize the deck for the maximum flat area? Or dou you have any other design ideas, at best with a file for DELFTship?

      Again, your help is much appreciated! All the best

    • #38722

      Neither I am a mechanical nor nautical engineer… :blush:

      I think the answer is in the document you mentionned (p.3 & 4).

      I just wish to point out a problem:

      If your ship is powered 100% by solar panels, I assume it will be drifting during the night, and maybe losing… “ground”.
      So I think you’ll need different designs according to the dominant winds and streams (strong draught to profit by the stream, weak draught to profit by the wind)… or a half-submersible ship. In this eventuallity, the ship computer would be able to “understand” if the wind or the stream will help the ship drifting in the right direction, and adjust its draught by filling or emptying a water-ballast just before the night.

      It may sound daunting, but when I see the MaxiMOOPs’ performances I think you’d have to think it over…

      An other idea for your project is to use a vertical solar panel and use it as a sail, too. Thus during the night the ship will be still moving along… provided there’s some wind and you can get light-weighted panels.

      Anyway, I’m preparing a DS file for a classical design melting both the two designs you posted (lenght: 1.425m). Maybe it will give you ideas… :whistle:

    • #38724

      Here you have a design I quickly made to start your thoughts.

      As you can see, there a connection between the keel and the rudder. Thus I think the screw (still not drawn) and the rudder will be protected. The shaft’s other end will be connected to the motor… located in the bow. I chose this configuration because I imagined a shaft rotating in a flooded sheath, thus the pipe’s end will be above the water level.
      The main solar panel (motion) will be sloped leftward or rightward according to the sun’s position. The little panels (bow and stern) will be used for the electronics.
      The CG location is too high because I didn’t place the ballast at the keel’s bottom but on all its height (I attributed the keel’s layer a high-density material stats). For a more acurate drawing, the ballast itself will have to be drawn.
      I didn’t draw the panels supports, but I quickly closed the deck using a fake tarpaulin (just for deveiving the software when checking the leak points). I assume you’ll use a hard top.

    • #38729
      El Kroketto

      Hi Icare and everyone,

      thank you very much for your great input on this project. I would like to explain some of my thoughts to hear about your opinion:

      I hope to harvest enough solar energy to power the motor not only during the day but the biggest part of the night as well. Should the battery charge get lower than a certain threshold (e.g. when days are short) the motor stops and only starts for short “bursts” to stay more or less on course. Adding a sail may be useful when energy is low but it could possibly raise additional problems, like navigation and controling the sailing mechanics.

      I really like your idea on filling ballast tanks to stabilize the course when the boat is drifting. I will definitly try to think this through, even though pumps and water tanks on the inside of the boat may cause new problems.

      Your hull design is great, especially “hiding” the propeller and the rudder will reduce damages from algae and sea debris. I redesigned the deck to maximize the area for the so crucial solar panels. What do you think of this edit?

      Edit of Icare’s design

      Compared to the original MaxiMoop design, this keel is more shallow. Do you think that (assumed I added enough weight to the lower part of the keel) the boat will reliably straighten up after capsizing?

      Again, thank you!

    • #38736

      Hi Elias!


      The idea I suggested (using a water ballast when drifting to profit by the wind or the stream) will be really efficient when the wind and the stream will try to move the ship with different strenght, mainly if their directions are opposite… and only if there’s some wind or stream, of course.
      This idea will be more or less efficient according to the seas the ship will navigate and according to the weather.
      Maybe the best efficiency would occure when leaving the shore, when the there’ll be a risk the ship surf the waves backwards, like it seems happening on the fig.1 of the document you provided us. (This gave me an other idea, but I’ll disclose it later).

      If you want to test the variable buoyancy, I think you’ll need:
      – a popdrink bottle (P.E.T.);
      – flexible air pipes (found in the aquaria department of a pet shop);
      – an air pump working on batteries (found in the fishing department of a sports shop);
      – two valves;
      – all the required paraphernalia to send the whole on the water, provide energy to the air pump and to operate the valves.
      Broadly, the bottle will be laying at the lowest point of the hull (below the waterline) and three pipes will get out of it:
      – downwards to let the water get freely in and out of the bottle;
      – upwards to inject air from the air pump into the bottle (when finished close the valve to be sure there will never be water flowing back to the pump… trust me: I have two aquiaria and I lost two pumps this way, when the air pump stops, water can flow UPwards for 5 cm, matter of pressure, I’ve been said);
      – upwards again for an air intake, with a valve (open the valve to let the water in, close it to keep the air in).
      Do you need a sketch?


      As I said before, I ain’t an engineer.
      But I assume the sailboats need a deep keel mainly to thwart the wind force and the lateral drifting (caused by the wind, too), but your ship won’t be really concerned by these forces.
      The keel weight will just make up for the solar panel weight, and the battery location will help if you can place it in the keel’s pane… provided flat batteries exist…
      Furthermore, the keel is long enough to contain more lead than the sail MaxiMOOPs.
      Anyway the file I posted must be considered just a preliminary sketch. Once you’ll know the intended elements’ weight and dimensions, you’ll draw them and fill the LAYERS’ stats. Then the DelftShip software will tell you about the ship’s buoyancy and stability.

      MY NEW IDEA (mentioned upper):

      Maybe I’m nuts…
      I imagined it can be possible to use the waves’ energy. Of course, it won’t work it the eventuallity of dead calm, but the solar panel will then work.

      First I thought of using a pendulum.
      I’ve heard from a “new energies” generator using this technology and couldn’t believe it’s efficiency (french link: Meanwhile the waves roll the ship to and fro, the pendulum tries to remain vertical, so there’s a to-and-fro movement between the pendulum and the hull. This movement can actuate a dynamo.
      I’ve been said that such a generator (real size ~100 fts long) can provide a little town its electricity.
      I made a sketch (see below).

      Then I thought of a purely mechanical process, using mobile panes (like oars) on the hull’s sides (each shaft having a limited rotation ~90°) to provide an antibackward movement effect.
      When the wave will lift the bow, the ship will tend to move backwards, then the mobile panes will unfold and stop the movement.
      When the wave will lift the stern, the ship will tend to surf on the wave, then le mobile panes will fold along the hull and allow the movement.
      Thus the ship will “swim” like an aquatic insect, using just the waves’ energy…
      The solar panel will provide energy only to the electronics… I assume this ship can profit by any wave size.
      If it isn’t neat enough, I made an other sketch with the oars in different positions.

      Is there any engineer here to comment both ideas?

    • #38739
      El Kroketto

      So many great ideas coming in :cheer:

      When speaking of alternative forms of motors, I can highly recommend this documentation on the inventors of the wave glider. Take a look at this 30 min video on YouTube.The basic idea is so simple but yet powerful and persistent (as long as there are little waves):

      Using a pendulum to harvest energy from the ocean’s movements could be an interesting topic for further research. Unfortunately I don’t live close to the sea and tests would be pretty hard to perform. I think that sticking with solar panels and conventional batteries will be fine for the beginning.

      & others: Do you think it would be possible for you to help me determinig the buoyancy and stability of the model, as soon as I designed a hull?


    • #38763
      El Kroketto

      Hi everyone :side:

      I created another hull design, trying to minimize the water resistance and maximize the deck area. This is the result:

      The deck offers enough space to fit 150 watts solar panels on top. It has a curved shape to support the roll-over after capsizing.

      I’d really appreciate your help on two or three questions I currently have:

      Hopefully you can see the that the deck is not closing with a sharp edge at the aft end. I tried to set each point as a corner on this very last edge, but without any good results. Any suggestions on this?

      I would like to remove the red marked area to insert the propeller (orange) and rudder (yellow). Is there any simpler way than just moving every point and edge?

      Last: How are hydrostatic informations calculated? I am especially interessted in stability and the possible weight I could fit into the boat.

      I have added the DELFTShip modell to this post if anyone would like to see my results in action.

      I really appreciate any support on this topic!

      Thanks and regards

    • #38766
      Robert Holme

      Hi Elias,

      1. To make a full corner crease the deck.

      2. to remove the unwanted bits delete them then add new faces.

      Attached is a rough hack of your model



    • #38768
      El Kroketto

      Hi Maryak,

      thank you very much for your help on the design! :cheer:
      I will refine some parts and hopefully start to build a small scale prototype during the next weeks. Maybe I am going to keep record the process – if so, I will post a link here to keep anyone interested informed on this project.

      Thanks again and all the best

    • #38784
      El Kroketto

      Hello again :blush:

      after rethinking the propulsion and steering systems, I came to the conclusion that two water-tight motors will help reducing the risk of water intrusion. Plus the mechanics of a rudder are not too complex but more fault-prone than this solution. I managed to do some minor changes on Maryak’s design, but now I’m stuck with two new problems:

      The blue circle represents the position where the propellers should be placed (the second one mirrored). The green rectangle shows a sloped face I’m not able to close. Could anyone please help me with these two changes if it’s not too much work?

      Thank you very much! Best regards

    • #38786
      Robert Holme

      Attached is mod fpm and jpg of mod


    • #38796
      Robert Holme

      The jpg is not clear enough so here is a clearer image

      Regards Maryak


    • #38810

      I can’t open your file (I’m still using an FS old version on an old computer).

      But I still can explain you how to do:
      – Toggle the view on the half hull (symmetry not shown);
      – Select all the edges of the (half) hole;
      – Extrude them toward the symmetry plane;
      – Select all the new points and align them on the symmetry plane by changing their lateral coordinate to zero.

      Note: If you have an horizontal edge (two points on the same horizontal coordinate), extrude the edges slightly downward for the new edges DO NOT get superimposed, collapse one of the two problematic edges (generaly the most distant one from the symmetry plane), then align horizontaly the new points with their relating origin.

      I hope it’s clear enough without screenshots (presently I’m not using a computer with FS installed on)…

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