Building solar-wind-powered outrigger double-ender for student voyages in the tropics

Discussion in 'Multihulls' started by Martin Henz, Jun 25, 2017.

  1. Martin Henz
    Joined: Jun 2017
    Posts: 2
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    Location: Singapore

    Martin Henz New Member

    I'm going to build a solar-wind-powered vessel for 4 to 40 day seafaring excursions with students in the tropics.

    Students spend their time on board navigating and sailing and on projects ranging from astronomy to zoology. To get an idea of the kinds of voyages to be undertaken by the vessel, watch this video:

    Key requirements:
    * Safety: The vessel is made for student voyages; safety of students is not negotiable
    * Quiet operation: Propulsion via sails and electric motor(s)
    * Small carbon footprint: Solar, wind and water power only
    * Decent cruising speed: Around 10 knots average would be great
    * Space: A typical number of students is 15, plus 2-3 instructors and 3 crew
    * Accommodation: tropical setting; sleeping "under the stars" while at anchor, with awnings for rain protection
    * Overall style: No-frills; low-cost; camping feeling

    Design challenge:
    The main design challenge when combining solar power with sails is to avoid large parts of the solar panels to be blocked by the shadows of the sails. The solution: A double-ender outrigger design with mast(s) on the main hull and solar panels between the hulls. The outrigger is always kept on the sunny side so that the shadow of the sails is never cast on the solar panels. To achieve this, the vessel needs to "shunt" whenever necessary, by switching the roles of bow and stern. This means the everything on board needs to be symmetrical with respect to a transverse plane.

    Some initial ideas:
    * both hulls (main hull and outrigger) made of fibreglass, for lightness, perhaps around 75 foot LOA
    * about 2 tons of lead acid batteries, along the keels of both hulls (main and outrigger): around 70 kWh
    * about 100 square meter of solar panels between the hulls: combined max power around 15kW
    * rudder in the centre of the boat, between the hulls, can turn 360º
    * electric motor(s) in the centre of the boat, between the rudder and the main hull, can turn 360º
    * Motors should be outboard style, removable by tilting. Combined max electric motor power around 25kW. Using 10-15kW for cruising and motor-sailing, i.e. 5-7 hours on one charge
    * schooner junk rig: 2 equal free-standing masts (perhaps carbon fibre?) on the main hull; hoping for ease of operation of junk-style sails, perhaps removable "forestays" for hanking foresails?
    * optional: wind turbines on each mast top: perhaps 3kW each

    I'm looking for a boat designer with track record in multi-hull designs. I'd appreciate any recommendations for designers, or any comments or suggestions regarding this project.
    Last edited: Jun 25, 2017
  2. jorgepease
    Joined: Feb 2012
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    Location: Florida

    jorgepease Senior Member ... I think you could mod this boat to suit your needs. I would roof in most of the bridgedeck and raise the booms so they can clear the roof. Then panel the whole darn thing and you will have enough power to suit you and a huge area to pitch tents, hammocks, etc... underneath. Leave room for a protected galley and heads and make the cabins your store rooms for supplies
  3. groper
    Joined: Jun 2011
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    Location: australia

    groper Senior Member

    Yep- sounds like a job for a harryproa.

    Your battery idea is flawed however - you really should not consider anything but lithium battery chemistry- for the same useable power lithium is the same price now but 1/3 the weight.
    Also , despite the sails being over 1 of the hulls only- there will always be points of sail where they shade the solar array- just depends on the wind direction and your sailing angle...
  4. Richard Woods
    Joined: Jun 2006
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    Location: Back full time in the UK

    Richard Woods Woods Designs

    You will also need to get it coded/certified, so it isn't just a case of buying a stock plan or even having a one-off design built. You will need to contact the MCA/USCG or whichever is appropriate before going too far

    Richard Woods of Woods Designs
  5. Martin Henz
    Joined: Jun 2017
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    Location: Singapore

    Martin Henz New Member

    Thanks, everyone, for these insightful comments. The help I get from you exceeds my expectations. So glad I found this forum!

    jorgepease: Thanks for pointing me to Will contact them to get their views and see if we can work together. Your suggestion to roof in most of the bridgedeck is interesting. I haven't thought of that! Plenty of space for galley and living area.

    groper: Thanks for pointing out the lithium battery option. I was scared by the cost, but the prices did come down. Will investigate more. Regarding my "solution" to the design challenge: I'm still convinced that by turning the boat suitably, we can avoid that the sails on the main hull cast a shadow on the solar panels. In general, if the sun and the wind come from the same side, it's a good idea to have the outrigger on the windward side (Pacific style). If the sun and the wind come from opposite sides, the outrigger should be on the leeward side (Atlantic style).

    Rchard Woods: Yes, good point. I will need to contact the local authorities, in my case the Maritime Port Authority of Singapore, and understand how to achieve registration for carrying paying passengers. I suspect that MCA/USCG approval would help. Need to work closely with the boat designer/builder and the authorities.
  6. jorgepease
    Joined: Feb 2012
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    Location: Florida

    jorgepease Senior Member

    I would add, when your anchored, you won't have that much shade. But the masts could cast a shadow on some solar panels. I would spend the extra bucks and get a controller for each panel so the shaded panels don't de-power the rest.
  7. groper
    Joined: Jun 2011
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    Location: australia

    groper Senior Member

    Solar panels - even the cheap ones- now come with individual optimizers pretty much standard these days. This essentially negates the need for mppt tracking on every panel - nevermind an entire string.

    Martin if your serious about this- i can help you with elextrical equipment selection to keep costs to a minimum. Cost is the biggest challenge on a project like this.
    Solar panels here in australia i can now buy at 54c per watt. This stuff is getting cheaper by the month. Batteries not as quick to drop , but they are coming down also.

    I see your idea on the sailing config- nice. Harryproa has always designed rig on the lee hull with all the weight in the windward hull to maximise righting moment. I guess a few design changes and increased engineering would allow it to sail the other way around using symetrical foils rather than the asymetric he normally uses.
  8. lucdekeyser
    Joined: Aug 2004
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    Location: Belgium

    lucdekeyser Senior Member

    60' Kleen Breeze is one of the larger Harryproa's inspired boats that just hit the water
    With symmetric foils. Brand new solar installation about to be finished.

  9. rob denney
    Joined: Feb 2005
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    Location: Australia

    rob denney Senior Member

    Jorge and Groper,
    Thanks for the recommendation.

    A harryproa would do the job nicely. My answers follow your questions. A couple of months ago we designed an 80' harry to be built by unskilled labour and used as a ferry/cargo carrier for isolated island communities in the Banda Sea. It is not very close to what your boat would look like, but could be a starting point. My comments are based on that boat. Attached are some drawings.

    Stunning! Lucky students.

    Harrys are safer than conventional multis. No foredeck work, no extra sails to handle, lightly loaded mainsheets and the ability to stop within a boat length and sail in reverse back to a man overboard, then stop to retrieve him.
    No flapping sails, wind whistling in the rigging or any need for shouted commands makes harrys pretty quiet.
    Easy enough, but the biggest part of the carbon footprint is the materials to build the boat. I'm pretty sure a low weight boat, built from sensible materials using a system that minimises waste and processing will generate less carbon than the diesel required to run it for a few years. The main (huge) advantages of solar, wind and water power are the lack of noise, smell and maintenance and not having to find somewhere to fill the tanks.
    No problem under sail reaching or running in 15 knots or more. Not sure how often you will get this in your part of the world. Upwind and in lighter breezes, it will be a function of the motor and the amount of power you can generate. Performance could be improved by reducing the weight or increasing the sail area.
    Neither is a problem. Pretty sure you will only need 2 crew, and could get by with one if the students and instructors are willing to help.
    My kind of boat!

    A novel solution! I would not use it for a harryproa, but if the 2 hulls were the same length, then it would certainly work. Would be a little slower and a little more expensive than a proa, but would have more payload. The rudders and rig would work as they are.

    No problem. Intelligently Infused (INTELLIGENT INFUSION – Harryproa would minimise the weight, cost and build time. The cargo proa was designed to not require expensive core.
    No problem, except I agree with Groper about the benefits of lithium.
    I would not have the area between the hulls completely covered as seeing the stars at night is one of the joys of sailing offshore. There is 40 sq m on the cabin roof of the cargo proa, 72 sq m if the roof was extended to cover the beams, the ww hull and the passageway immediately to leeward of the deckhouse. The other panels could easily be walk on panels on the ends of the hulls. The layout for a shunting cat would probably have the deckhouse in the centre of the boat, with plenty of deck space to walk around. This could be covered with tarpaulins for shade, or removed to enjoy the wind and sun in your hair and the stars at night.

    Rudders need to be near the ends to provide turning force. They should also be able to lift up for shallow water sailing and kick up in a collision.
    a small electric motor mounted on a steerable tube on the centreline makes it very easy to manoeuvre in tight spots. Only one is required.
    The cargo proa is intended to be primarily a sailboat, using the tender outboard for in port and light wind propulsion, and providing a fast, capacious tender for cargo. This set up would also work for you using batteries and an electric outboard. If not, alternatives are pretty easy to arrange.
    If you want to go upwind, an unstayed schooner with a single conventional mainsail per mast is best and very easy to operate. If not, then a junk rig will do the job as well as being cheaper.
    Could do, but if you will be sailing a lot, then a water charger would be worth a look as well.

    Attached Files:

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