Efficient Hull Design for small autonomous solar boat

Discussion in 'Boat Design' started by highamperage, Jan 5, 2011.

  1. highamperage
    Joined: Jan 2011
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    highamperage Junior Member

    I am toying with the idea of building a small autonomous solar powered boat for fun. I am wondering if anyone can provide some pointers on how much power will be needed to move it through the water?

    I am thinking of building a long and thin hull, maybe around 10' long with a 2' or 3' beam and expecting it to weight around 500lbs. My estimations make it appear like the boat will require about 150 watts to move at ~4 knots. However, I am far from an expert.

    Any thoughts? :)
     
  2. Lurvio
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    Lurvio Mad scientist

    A similar thread was active about a year ago, that probably has a lot of the answers you are looking for. The site search should find it.

    Lurvio
     
  3. Submarine Tom

    Submarine Tom Previous Member

    I have a thought, thanks for asking.

    Is this project for drug smuggling?

    -Tom
     
  4. highamperage
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    highamperage Junior Member

    Oh, why yes, it is. That is why I am posting questions on here. That is why I am using a very small design. That is why I care about efficiency. That is why it's slow and solar powered. That is why.. oh wait... None of these characteristics would be is well suited for smuggling drugs. How stupid of a statement is that?

    Anyway, back to the topic at hand. I checked out the post by amaurer for his 20' solar powered lonleybot and that is basically what I was thinking as well, although his is on a larger scale, with more abilities. I may actually go smaller than 10'. I need more data on how much power this will use. I may do some basic testing with a trolling motor and jon boat. ha. I'm poor. Oh well. Anyway, I was thinking of using an arduino with a connection via satellite Digi m10 modem. (I have done the PC route with a remote controlled "tank" which is controlled via 4G/3G - guzzles the power) My boat is small and will have limited resources) For photos I was thinking I might modify some type of smart phone to take pics and save them when commanded from the arduino and then transmit them once within GSM range. I have a lot of learning to do when it comes to setting up this type of stuff, but I think this would be a fun way to learn. Lots of lakes around here for testing!

    I like his website's title "Plying the waves to rescue one man from his cubical" AMEN to that. Although after reading his site, I must say his job is alot more interesting than mine! haha.
     
  5. BertKu
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    BertKu Senior Member

    Hi Highamperage,

    You should also look at the electic boat which Jeremy Harris made. Search under Jeremy Harris, theads. All what you have to do is to add a 35 - 100 watt solar panel with a regulator. He used a 2 Kw inexpensive 3 phase, with controller, motor, but drastically powered down to 100 watt. Therefore does not need to be cooled. They cost approx 40 dollar with a 50 dollar controller, if I still remember.

    Bert
     
  6. Tiny Turnip
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    Tiny Turnip Senior Member

  7. messabout
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    messabout Senior Member

    ten foot boat, very low power, 500 pounds, 4 knots...................these are contradictory factors. If you have made a good weight estimate at 500 pounds, you need a much longer boat.

    Four knots in a ten foot boat is crowding the bounds of probability. 500 pounds is going to involve a lot of wetted surface (and have to push a lot of water out of the way). Wet surface is the enemy for low powered boats such as kayaks and canoes and solar powered ones too.

    Think in terms of long, narrow and lightest possible weight.
     
  8. Lurvio
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    Lurvio Mad scientist

  9. Joakim
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    Joakim Senior Member

    True, it is not the best option. However, I just calculated my sailboat as 1:2.32 model using Delft Series. This gives it 500 lbs displacement and 10.7 feet LWL. The drag at 4 knots was 47 N (50% friction drag), thus requiring 97 W power and needing 64% efficiency for 150 W electrical power.
     
  10. highamperage
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    highamperage Junior Member

    Well, that seems pretty do-able. But I appreciate the advice, I will look at something a little lighter.

    If I use the 10 foot design I am thinking of it will be a conventional displacement hull design but with a flat top of roughly 10x6, and should produce around 550-650 watts. Assuming there are 6 hours of usable sunlight per day, if my estimates are correct, should total around 3000-4000 watts. My 150 watt motor operating 24/7 should use about 3600 watts, and the on board eletronics about 100, so a total of 3700 watts per day. (May have to go in sleep mode sometimes, although the total battery capacity was looking like 6kw/h so it could go a few days in medium-poor solar conditions before being forced to sleep)

    Anyway, 500lbs is a high estimate, batteries would only account for about 250 of that. And, the thought has crossed by mind to go smaller, cheaper, have less capacity and have it only operate during sunlight, basically having enough battery power to operate the aurdino for a few days in the event of poor solar conditions, otherwise motor is basically run on solar.

    I'm brain storming here. Anyone have a solid estimate on how much power an ardunio uses? I was basing it on 9v 500ma.
     
  11. Joakim
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    Joakim Senior Member

    The first one is correct, but assumption of 6 hours usable full power is quite much, if you have cloudy days as well. Around here 4-5 hours seems to be more accurate.

    Arduino is an Atmel AVR. I have made several of those and depending on what you do you can easily get 20 mA at 5 V and with a bit of more thinking 1 mA. I have no experience on Arduino, just Atmel AVR, thus I don't know if they are using good regulators and other components, which are the key to low power. Anyway 500 mA would be huge for any Atmel AVR. I'm running a full Linux system at 400 mA 5 V with USB, Ethernet etc in my boat.
     
  12. highamperage
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    highamperage Junior Member

    In regards to the solar power, you're probably right. I do live in an area with a large amount of sun, however, the boat shouldn't be confined to just this local area. About the Aurdino power usage, that is good to know. I figured it couldn't really be that high, but don't know. overestimate vs under. That really lowers the "reserve" my batteries need to have to keep it running in the lack of solar power should I opt for a smaller boat. Obtaining enough speed out of an even smaller boat to deal with currents looks like an issue or at least really slow progress down tho... although if I could find routes where the currents/winds go where I want it to go anyway, could work out.

    Can you give me some more info for Delft Series? I did a quick google search but didn't find much, other than a referece to an excel file? Is it part of freeship? (Just found that, will install when I get home from work :D )
     
  13. highamperage
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    highamperage Junior Member

    Nevermind on that delft, I figured it out. Very useful.
     
  14. tspeer
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    tspeer Senior Member

    The hull is the least important part of a boat like this. The real issues are in the development of the control system and, to a lesser degree, the development of the propulsion system. It also needs to be fault tolerant, and this requires a big effort, too.

    I'd get a canoe or kayak around 16 ft long and use it as a hull to get the systems worked out. The canoe would be large enough for you and the electrics, so you can observe and troubleshoot on the water. You will need a safety pilot onboard when you are testing your autonomous control, especially during the initial development.

    Once you have the systems working and you have been able to validate your performance prediction methodology against the measured performance of your testbed, then you'll be ready to design the real boat.

    There is no doubt that the state of the art in autonomous vehicles allows one to make a vessel that can charge blindly along a preprogrammed course. However, that doesn't meet the COLREGS. Both for the safety of the boat and for the safety of others, you need to solve the problem of maintaining an adequate watch, and avoiding collisions. It is irresponsible, and possibly illegal, to unleash something that does not have a collision avoidance capability. Not to mention the civil liability associated with such a craft.

    As a hobbyist, you can have all the fun of developing an autonomous vehicle with an optionally-manned vehicle. Just be sure you ride along on it at all times to handle the situations you didn't anticipate.
     

  15. BertKu
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    BertKu Senior Member

    Hi Highamperage,

    You are optimistic not to have losses. Your efficincy for the motor is about 90%, and for the controller another 90% and you may have losses in your cabling. All in all you need 190 watt for 24 hours, which give you a need of +/- 4500 watt per day. 6 hours of solar energy is very optimistic, except if you are able to follow the sun.

    My recommendation is serious to look at
    group9 [group9@eemb.com] or www.eemb.com
    For a 6Kwh battery , you only need about 45 Kg + mounting brackets ( 100 lbs in total)
    However if you use such low weight for batteries , your heavy solar panels may make you unstable. You have to do some calculations. Except if you yourself glue the cells on the roof with clear epoxy. Like they do with solar cars for competition. At the entrance hall of the marine faculty in Delft , Holland, there is a nice example on how to do it.
    Bert
     
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