RC Solar powered Boat

Discussion in 'Boat Design' started by Zain, Dec 19, 2013.

  1. Zain
    Joined: Dec 2013
    Posts: 27
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    Location: pakistan

    Zain Junior Member

    Hi i need help...I am doing mechanical engineering and our last year project is remote controlled solar powered boat which is just a prototype of length 1m....so my question is whats the imortant things and the principles do we need to start buiding a boat..
    We want to acheive the following things
    1.Speed of the boat should be 15-20km/hr
    2.it can bear the weight of solar panels,batteries,motor

    so i need to ask how can we determine the servo motors,,motor type and size,the hull type and hull size,impellers and propellers,shape of the boat,which material should be used,how much the power is needed to run the boat of 15-20kgs

    Thanks in advance
     
  2. Baltic Bandit

    Baltic Bandit Previous Member

    Well first you need to figure out how much power you will draw at 15-20 kph

    And its basically a looped design principle. your optimal displacement hull will run roughly 22:1 aspect ratio, which really isn't stable enough to carry a wide array of solar panels. (but you can perhaps try a very very very long design)

    So that suggests a catamaran hull since that gives you arbitrary width for the panels and still lets you have slender low drag hulls.

    so then you swag the drag equation for the hulls

    you hit a massive drag increase at 1.34 sqrt of the length of the hull in feet (or roughly 2L0.5) in knots

    15kph == 8.1 knots means your lowest drag hull will be 32-33' long. and 1.5' wide at max beam.

    that might be wide enough to get you enough surface area for solar cells.

    the next step is to figure out the drag on that hull - which then tells you the amount of power you will have to generate to http://sanderroosendaal.wordpress.c...-2-acceleration-and-deceleration-of-the-boat/

    The rowing shell equation in that link is pretty accurate

    Basically your biggest drag factor is surface drag which is given by F = alpha v2 and alpha is roughly 1.2xsurface area in meters.
     
  3. Baltic Bandit

    Baltic Bandit Previous Member

    so you have

    F (newton s^^2/m^^2) = 1.2 surface area. and your surface area is going to be

    vol of water displace = L x beam x depth. (this is a swag here since you are really going with a cylindrical shape

    remember 1m3 = 1000kg, so your displacement is going to be very low. A rowing shell of that length weighs 50kg and needs to handle much higher stress loads. if you built your hull out of carbon tubes covered with thin mylar plastic, odds are you could get the weight down to 25kg.

    so that gives you

    0.025 = 10 x .5 x Depth ==> 5cm

    So your surface area is roughly .5 meters squared.

    so you need about 0.6 hp motor and you can find that here http://www.baldor.com/support/Literature/Load.ashx/BR600?LitNumber=BR600


    So really the primary weight is going to be the power panels and the motor and the reduction gears.
     
  4. Zain
    Joined: Dec 2013
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    Location: pakistan

    Zain Junior Member

    Thanks dear....one thing more how do we use impeller and propeller.and how to decide the shape and size of it..and what should we use for the rotation of the boat...??
     
  5. Baltic Bandit

    Baltic Bandit Previous Member

    "rotation of the boat"?

    don't understand the question.

    Prop - you want to go for max efficiency - so that means a slower speed rotation but a steeper pitch. Essentially if you assume 70% prop efficiency you will be fine out of the box, but that's where your engineering fine tuning will come into play, the better the prop efficiency,, the less motor you need

    the less motor you need the less solar panels you need

    the less solar you need, the smaller a motor you need
     
  6. fredrosse
    Joined: Jan 2005
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    Location: Philadelphia PA

    fredrosse USACE Steam

    Solar Powered Model

    Solar power and your stated speed requirements are so far apart that there can be no realistic solution.

    The solar collection surface could charge a battery, perhaps for a few days or weeks, then the battery could drive the boat at the high speed for a few minutes at most.

    You must reduce your speed requirement, and most probably increase the model length considerably, depending on how much performance you can accept, and if battery propulsion with reduced running time is acceptable.

    For such a small hull, without battery storage of energy, (going direct from solar collector to drive motor), the speed would be very very low, and the slightest headwind will easily overcome the boat's propulsion system and push the boat backward.
     
    Last edited: Dec 20, 2013
  7. Baltic Bandit

    Baltic Bandit Previous Member

    1hp motor should be fine for doing this with a 33' long platform weighing 50kg

    that's 746 watts

    So depending on where you are in the USA, https://www.kencove.com/fence/131_Solar Panel Calculator_resource.php

    So in Seattle you would need about 19 of these panels https://www.kencove.com/fence/Solar Panels_detail_MSP40P.php which if assembled on top of a 33' long hull will take up 31 ' of it.

    so if you build your hull to look a bit like the image below (ignore the mast and the mini hull under it, you will end up with something that weighs about 95kg (80 kg for the panels, 5kg for the motor, 10 kg for everything else)

    You will be hard pressed to do 15kph but you should just about make it.

    Of course you do need a battery for some power smoothing but you should be able to do it

    though my initial swag about the motor being the primary weight factor was wrong. its the panels.

    1" diameter CF tubing weights 0.11#/ft so assuming 4 tubes x 33' => 7kg

    Wrap it in shrink wrap http://www.usshrinkwrapinc.com/industrial shrink wrap supplies.html which will add about 3# to the whole thing (8kg now) leaving you with 18' of tubing for cross bracing - which should be enough.

    And at 90kg you only add about 1sq meter to your immersed surface area. (10cm vs 5cm)


    [​IMG]
     
  8. Baltic Bandit

    Baltic Bandit Previous Member

  9. kerosene
    Joined: Jul 2006
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    Location: finland

    kerosene Senior Member

    15-20km/h for 1m boat with on board solar panels and 15-20kg boat = not gonna happen.
     
  10. Timothy
    Joined: Oct 2004
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    Location: canada

    Timothy Senior Member

    For 746 watts you could use 8 cheap semi flexible Chinese panels that weigh altogether less than 16 kilos. I bought four for my boat to test them for a solar electric sail boat I am contemplating building. They work like a charm.The hulls of my design are similar in concept to those of Miribaud LX. I agree with Baltic Bandit that this is the way to go with your project but I doubt you can achieve the speeds you want under motor without stored energy.I would love to see you prove me wrong. Good luck with your project and keep us posted .
     
  11. Baltic Bandit

    Baltic Bandit Previous Member

    Agreed that 1M isn't gonna work. 10 meters can
     
  12. Zain
    Joined: Dec 2013
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    Location: pakistan

    Zain Junior Member

    Sir..!! We are new to this field....we dont even know the basics of this project but e have to work on it...I live in Pakistan....We have not any experienced guy who can guide us...okay leave the length 1m..Leave the weight..leave the speed too...The point is we have to build a solar powered boat.....A complete working model.....So whats the minimum length we use?.whats the best dimensions..whats the minimum weight..?? whats the best hull..??and the dimensions?? we have to drive it on the canal which is 3m wide and The average depth of the Canal is 5 feet (1.5 m) and it is bounded by roads...
     
  13. Zain
    Joined: Dec 2013
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    Location: pakistan

    Zain Junior Member

    and kindly tell me the things which are to be used in this boat......we have to give the presentation to our teacher on monday that what we are doing,what lengths we are using,which type of motor we are using,which material we are using,which type of solar panels we are using,what is the mechanism and arrangement of the boat, i searched alot on the internet but din't understand any thing at last i fount this forum....will be really thankful to u...:)
     
  14. Zain
    Joined: Dec 2013
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    Location: pakistan

    Zain Junior Member

    Our basic aim is to run the boat even it is 10-12km/hr or less than it...and should looks like a project not a children toy...:p
     

  15. Zain
    Joined: Dec 2013
    Posts: 27
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    Location: pakistan

    Zain Junior Member

    our model design looks like this
     

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