Best hull for autonomous wingsail boat

Discussion in 'Boat Design' started by JGeddes, Dec 12, 2014.

  1. JGeddes
    Joined: Dec 2014
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    JGeddes New Member

    Hi,

    I would like to attach a wingsail to a boat, but I am undecided about which hull is best.

    http://vimeo.com/79511782

    The wingsail is a little different to normal because it will swivel to put itself into the optimum position, but also because with this design it is possible to power-up and power-down the sail.

    I would like to build a sturdy wing for long-distance autonomous sailing for several months at sea, which likely will be heavier than normal. I also need the boat to be self-righting.

    My question: which hull is best?
     
  2. messabout
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    messabout Senior Member

    Jgeddes; You are going to get some negative answers here, and for good reasons.

    I will start by suggesting that a wing sail at sea is a very bad idea. Aloft weight and the fact that they can not be easily reefed makes them dangerous at sea. Also wing sails require painfully delicate trimming if they are to work well. That is why large ones use all kinds of electronic feedback circuitry to determine optimum trim. Then there is the disproportionately large cost factor along with structural complications for the boat.

    Those sails do help to make the AC multis incredibly fast, but then The AC boats are not cruising boats.

    Let's see what the other guys say..............
     
  3. lucdekeyser
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    lucdekeyser Senior Member

  4. JGeddes
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    JGeddes New Member

    The saildrone is an excellent boat and made it from California to Hawaii in 34 days. It is built out of carbon fiber and is no doubt pretty tough.

    The design I would like to use is more like the one on this page:
    http://www.sailwings.net/tldescribed.html

    albeit minus the guy and the 4ft gap under the sail. Also, I would like to make the wing a bit larger than the demonstration in the photo.

    The wings 'self-trim' so that the angle of attack is optimum. The smaller wing at the back is the lever which puts the main wing in the right position, adjusting from moment to moment much faster than a person with ropes ever could.

    The problem as you state is if there is too much wind and there is a need to de-power the wing or reef it.

    If you read a bit about the automatic governor, you can see that there is also a 'throttle' mechanism, with forward, neutral and reverse as the governor rotates around a cam. The onboard computer will be monitoring the wind and will put it into neutral should the wind get too high. Once in neutral, it has far less drag than a regular sail and mast and so doesn't need to be reefed. No ropes either - just a 'throttle' and rudder at the rear. None of this is my invention, but it is all quite ingenious.

    But, I do need a sturdy wing which adds weight (probably rectangular like the photo). I also need the hull to self-right. When it is out sailing on it's own, I won't be there to lift it back up again. So, should I use a monohull, a catamaran or a trimaran?

    I am in mid-discussion on this forum:
    http://diydrones.com/group/arduboat-user-group/forum/topics/ocean-going-drone

    which is generally a more electronics-based forum, whereas this site is more boat design - hence the question on here about which hull design would be best.
     
  5. lucdekeyser
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    lucdekeyser Senior Member

    there is little to improve on the saildrone given similar reqs but make it a pacific proa to eliminate all under water appendages as a board with an asymmetric lw hull and rudders with a schooner setup of wings (robot sail challenger had one of those controlled electronically). For self right, have buoyant wings, lw hull pod and ama windage when capsized.
     
  6. daiquiri
    Joined: May 2004
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    daiquiri Engineering and Design

    The best hull will not depend so much on the type of propulsion. It will depend much more on what you will have to carry on-board. What is the scope of the project?
     
  7. JGeddes
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    JGeddes New Member

    The proa is an interesting design. I can see that the deep V-shaped keel would provide lateral resistance but also tend to avoid getting caught in floating debris.

    However, the trimaran looks like it will win. It is fast, and the hulls can be optimised for one direction with a single rudder. If the keel and rudder are swept back, it should pass over marine debris and I could possibly place a skeg to protect the rudder. It's really just a case of making the wing light enough and I think making the amas shorter than the main hull so that it will roll into an unstable position where the keel pops it back up again.

    As for payload, none. Right now I am just interested in building something that will travel very long distances on its own and reach its destination. Or, maybe a small compartment for a couple of cans of beer for the other end of the journey.
     
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  8. lucdekeyser
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    lucdekeyser Senior Member

    The Saildrone is not a trimaran but a stabilized monomaran.
    Your decision matrix seems not burdened by too many hard points but having some fun.
    That you will.
     
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  9. DennisRB
    Joined: Sep 2004
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    DennisRB Senior Member

    The monomaran with keel sure seems to fit the bill the best. The wing can be used to help self right by providing buoyancy should it tip over. The weight of the keel and size of the amas can be fine tuned so that a minimum weight keel / maximum buoyancy amas can be used in conjunction with the buoyancy from the wing. The lighter the keel and bigger the amas the better it will sail, but the less self righting ability it will have, so a compromise needs to be reached to self right. If the wing snaps off it won't right, but it will be a loss anyway without propulsion.

    I wonder if high buoyancy amas could be made that were designed to flood in the event of a capsize? The trick would be keeping water out when the boat is upright, and allowing it in when it is not. This would make for a faster boat with less keel weight and more sail carrying power.

    The catamaran will be the worst solution as it is not an efficient platform to make self righting. The proa might be decent, but rudders will be problematic. Which way do you rake them so as not to catch weed because they need to go both directions? It will be less stable, and the software could be difficult to program because shunting seems to need a good deal more information than if the boat only goes in one direction.
     
  10. johnhazel
    Joined: Jun 2008
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    johnhazel Senior Member

    It seems that any multihull could "turtle" and never come up or a if the wingsail was buoyant enough to break it out a turtle it would be so heavy that the boat would tend to stay lying on it's side after a knockdown.

    The only failsafe option seems to be a monohull with a very deep weighted keel and buoyant sail. The sail would cause the recovery from 180 degrees heel and the very long keel fin and weight would right it from a 90+ knockdown.
     
  11. Leo Lazauskas
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    Leo Lazauskas Senior Member

    But the long keel and weight would be more likely to catch weed.
    So, yes, it might be better at righting itself, but it might not actually go anywhere :)
     
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  12. DennisRB
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    DennisRB Senior Member

    Besides the ballasted stabilized monomaran. Any wing sail will be buoyant due to the airfoil shape as long as it is sealed. The strength will need to be there anyway to take a knockdown, so its not like it will be heavier to fulfil the dual purpose role of wing and turtle prevention device.

    Here is a pic of sail drone.

    [​IMG]

    The amas need to be low buoyancy otherwise it could stay turtle. Here you can see an ama fully submarining. But even so I imagine the sail carrying power would be much better than a regular monohull, which would be important when you cant reef. I think these guys nailed the design.

    [​IMG]
     
  13. Timothy
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    Timothy Senior Member

    A pacific proa with the rig canted to leeward ( self righting). No foils. Asymmetric leeward hull with rocker. Fore and aft sliding weight in the leeward hull (batteries maybe) to alter relationship of ce and clr to steer(windsurfer).
     
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  14. DennisRB
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    DennisRB Senior Member

    I imagine the weight would need to be shifted almost continuously a small boat to stay on course. That would use a lot of power. Still a good idea though!
     

  15. Timothy
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    Timothy Senior Member

    He could mount a 100 watt flexible solar panel(4 lbs) on the beams supporting the ama ( with the rig canted to leeward the panel would only ever be partially shaded). It could aid in self righting and should supply all the power he would need. I am pretty sure a smart app could be developed to administer the weight shifts required and it would not take much to adapt his forward reverse mechanism to the shunting procedure.
     
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