Discussion in 'Sailboats' started by nabberuk, Sep 1, 2012.

  1. nabberuk
    Joined: Sep 2012
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    nabberuk Junior Member


    Hope you guys don't mind me posting here. We're in the process of designing an autonomous sailing boat that will attempt to sail the Atlantic in the challenge (nobody has completed it yet). The sail boats brains will the Raspberry Pi, we're detailing every step so once complete other's can build there own.

    I've spoken to various companies for sponsorship, we've so far secured satellite communication and discounted carbon fibre supplies and i'm always talking to other potential sponsors.

    We were planning on using the 2 meters plan from but we don't think the hull plan's would work best at sea.

    Is there anyone here interested in this sort of project and could take the lead in designing the hull?

  2. CutOnce

    CutOnce Previous Member

    Raspberry Pi

    Good little embedded platform. What are you developing in? Linux, Android? GPL'd? Language? C, C++, Python? Everything in flash? SSD? Custom watchdog?

    Be interested to hear how you are talking to the external data collection sensors. Are you polling through embedded custom hardware or using USB and/or existing serial comms? It would be interesting as well to see a schematic of your control circuitry external to the Pi.

    How are you handling external data communications?

  3. nabberuk
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    nabberuk Junior Member

    Hey, We'll be using mainly Python as i think it's simpler for people to learn than say c/c++. We'll be interfacing with various sensors via the GPIO pins (We will be using an add-on board) or maybe USB. As you can probably tell we haven't got all the details finalised so there is no schematics just yet.

    We've agreed with a commercial company who will sponsor by supplying a two way sat comms module and including some of the comms cost.

    I plan to get the hull/sails done and use RC gear to test the boat before starting getting the electronics inside. We have programmers and electronic people on board (excuse the pun!) just nobody with knowledge in the hull side of things. I've been looking at the Volvo 70 Ericsson plans but i'm unsure if this would handle the the Atlantic.

  4. Doug Lord
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    Doug Lord Flight Ready

    You should contact Graham Bantock at Sails etc in the UK. He is one of the best model yacht designers on the planet and is a supplier of hulls, rigging sails---etc. He's done work for me in the past and is first class to deal with.
    If you catch him at the right time he may well become interested in your project and their are few- if any at all- that could help you like Graham could. Make sure you approach him professionally.
    Heres his website:
  5. nabberuk
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    nabberuk Junior Member

    I'll drop him an email, thanks for that.

    I was having a little discussion with a friend about the effects of having a sloped transom (hope that's what its called). He says it helps stabilise the hull. Is this true?

    I've been looking at the RS2000 plan from for this project. What do you guys think? Would it survive in the Atlantic? It would be a Balsa Wood construction with Carbon Fibre. It would also have a keel in the range of 10-15KG.
  6. nabberuk
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    nabberuk Junior Member

  7. gonzo
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    gonzo Senior Member

    The transom, being out of the water, does not stabilize the hull. If you are referring to reverse transoms, they are mainly designed to reduce weight at the stern.
  8. sharpii2
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    sharpii2 Senior Member

    I would suggest you go with a more conservative hull and keel.

    Since the boat is not going to be able to shorten sail (or at least that's what it looks like to me), you're going to need a rig that can stand terrific punishment. Even a small gale is going to be a cat 5 hurricane from your autonomous yacht's point of view.

    Also, your little pond racer (though fully found and arguably seaworthy) will have crappy directional stability (it is designed for tight tactical maneuvers, like a fighter jet). You need something more like a bomber (or passenger jet), something that has a tendency to stay on course on its own, so it needs minimal control inputs.

    I would also want a sail that can be reefed reliably, or feathered. Some wing sails have survived hurricane winds, because they can feather so well. Such a system needs minimal machinery to work. It resembles an airplane set on edge, with the horizontal stabilizer acting as a sail trim control, with the wing, itself pivoting on its main spar.

    Another possibility would be a sail made up of panels, separated by heavy boomlets, similar to a Chinese junk rig, but with the boomlets further apart.
    Then, all you need is a hoist, when the time to reef has passed. Each of these two systems require minimal mechanical gear to work, and only one RC channel.

    The boat should be on the heavy side, as it will be a bit under canvassed, and 'heavy' boats tolerate this better than light ones. What I mean by 'heavy' is a boat which has a displacement of: 20*Volume/((Beam^2)*Length) = 1.5 or more. Measure all of these with any unit you choose, but stay consistent.
    In the case of cm, use cm, scm, and ccm.

    The keel will have to be quite heavy, as to insure the boat finds it's feet, if it's rolled over. I would go with either a rather long keel, which is half as long as the Waterline, or I would go with tandem keels, which share the same ballast bulb (for greater depth without excessive whetted area).

    The hull form should be be round or 'V' in section, as ultimate stability is what you're after, as well as low rigging loads from gusts. Below I'll attach a sketch of a 'plank on edge' boat, made up of flat facets, so you can see such a concept ('plank on edge', not the facet hull) might work for your design goals. The advantage here is that the keel and hull are perfectly blended together, reducing whetted surface for it's displacement, while having adequate Lateral Area. Such could use batteries, or other heavy equipment as ballast, forgoing the need to add such separately

    Below, also, I'll attach a drawing of what I call a 'stack sail', so you can get the general idea of how such a system would work. I would favor it, over a wing sail system, as I feel it can be made more durable

    If someone actually pulls this off, they are bound to upset Homeland inSecurity, on this side of the pond.

    Attached Files:

  9. Tim B
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    Tim B Senior Member

    Sounds like a fun project, and there is now plenty of info around on the web to enable you to do it. So, here's the advice...

    Don't discount C/C++ too quickly. It's very powerful, good for low-level I/O and has libraries like QT4 available, which can make life a lot easier.

    Have a look at and . It's a simple and pretty well-proven servo controller.

    I would remove the USB socket on the R-PI and wire direct between the USB and onto the add-on board. You may wish to invert the GPIO header as well, and then squeeze foam (the plastic, non-absorbant stuff) between the two boards.

    For the moment don't worry too much about the vessel design itself. Find a reasonable plan on-line for a "pond-racer" (there are loads, and the marblehead class is probably a good one to go for). You'll probably find that you'll need a few iterations before you get a boat that will reliably sail a straight course (Autopilot stage 1). A few more iterations for tacking and gybing (Autopilot stage 2) and a few more again before you can autonomously sail a given triangle (Autopilot stage 3), and a few more again before the boat will autonomously beat to windward. Get that working on a pond, then you can start looking at bigger lakes and open sea. Again, starting small and working up to longer passages, in presence of a chase-boat.

    You will also need to consider GPS (which is easy but will consume power, so you may wish to switch it off when a fix is not required) and some form of wind-vane, preferably at the mast-head, which will give you a way to set the sails. Sattellite communication is fine, but you may find a 3G dongle or even wifi would be effective on lakes and in-shore, and again, would simplify your setup.

    Hope this helps, feel free to e-mail me any further questions you have,

    Tim B.
  10. Petros
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    Petros Senior Member

    I agree with Sharpii2 comments, all out performance is not as important as durability and survivability. this is no to much a speed race as one of durability. A very simple sail rig with as few elements to get tangled or caught on debris.

    I would consider a single junk rig, with a short and stout cantilevered mast. A stout and deep weighted keel so it self rights quickly, as large a hull as is reasonable for your power requirements. Minimize all external protuberances so it will collect less junk and will more quickly right itself without picking up weeds or other trash from the ocean. Consider it has to be durable enough to survive storms, waves, crashing beaches, repeated capsizes, etc. without any repairs or assistance.

    Good luck
  11. nabberuk
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    nabberuk Junior Member

    thanks for the replies guys, just busy googling some of the terms! lol

    We have got plans in place for lots of testing, but would rather do it with a hull the same as the ocean going one. I'd like as little to change from the testing phase to final ocean going one.

    I'll reply back in a bit once i've decoded some of the terminology.

    thanks again!
  12. nabberuk
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    nabberuk Junior Member

    In simple terms what makes a hull stable? low centre of gravity being one.
  13. Tim B
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    Tim B Senior Member

  14. tspeer
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    tspeer Senior Member

    How do you propose to comply with the International Regulations for Preventing Collision at Sea (72 COLREGS), and in particular the section below?

    Section I - Conduct of vessels in any condition of visibility

    Rule 4
    Rules in this section apply in any condition of visibility.

    Rule 5
    Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision.

    Rule 6
    Safe speed
    Every vessel shall at all times proceed at a safe speed so that she can take proper and effective action to avoid collision and be stopped within a distance appropriate to the prevailing circumstances and conditions.

    In determining a safe speed the following factors shall be among those taken into account:

    By all vessels:

    the state of visibility;

    the traffic density including concentrations of fishing vessels or any other vessels;

    the manoeuvrability of the vessel with special reference to stopping distance and turning ability in the prevailing conditions;

    at night the presence of background light such as from shore lights or from backscatter of her own lights;

    the state of wind, sea and current, and the proximity of navigational hazards;

    the draught in relation to the available depth of water.

    Additionally, by vessels with operational radar:

    the characteristics, efficiency and limitations of the radar equipment;

    any constraints imposed by the radar range scale in use;

    the effect on radar detection of the sea state, weather and other sources of interference;

    the possibility that small vessels, ice and other floating objects may not be detected by radar at an adequate range;

    the number, location and movement of vessels detected by radar;

    the more exact assessment of the visibility that may be possible when radar is used to determine the range of vessels or other objects in the vicinity.

    Rule 7
    Risk of collision
    Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.

    Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plotting or equivalent systematic observation of detected objects.

    Assumptions shall not be made on the basis of scanty information, especially scanty radar information.

    In determining if risk of collision exists the following considerations shall be among those taken into account:

    such risk shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change;

    such risk may sometimes exist even when an appreciable bearing change is evident, particularly when approaching a very large vessel or a tow or when approaching a vessel at close range.

    Rule 8
    Action to avoid collision
    Any action to avoid collision shall, if the circumstances of the case admit, be positive, made in ample time and with due regard to the observance of good seamanship.

    Any alteration of course and/or speed to avoid collision shall, if the circumstances of the case admit, be large enough to be readily apparent to another vessel observing visually or by radar; a succession of small alterations of course and/or speed should be avoided.

    If there is sufficient sea-room, alteration of course alone may be the most effective action to avoid a close-quarters situation provided that it is made in good time, is substantial and does not result in another close-quarters situation.

    Action taken to avoid collision with another vessel shall be such as to result in passing at a safe distance. The effectiveness of the action shall be carefully checked until the other vessel is finally past and clear.

    If necessary to avoid collision or allow more time to assess the situation, a vessel shall slacken her speed or take all way off by stopping or reversing her means of propulsion.

    A vessel which, by any of these Rules, is required not to impede the passage or safe passage of another vessel shall, when required by the circumstances of the case, take early action to allow sufficient sea-room for the safe passage of the other vessel.

    A vessel required not to impede the passage or safe passage of another vessel is not relieved of this obligation if approaching the other vessel so as to involve risk of collision and shall, when taking action, have full regard to the action which may be required by the Rules of this part.

    A vessel the passage of which is not to be impeded remains fully obliged to comply with the Rules of this part when the two vessels are approaching one another so as to involve risk of collision.

  15. nabberuk
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    nabberuk Junior Member

    Would anyone even realise if they collided with a 2m vessel?
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