Roll Control using foils

Discussion in 'Sailboats' started by Wingz, Oct 19, 2010.

  1. daiquiri
    Joined: May 2004
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    daiquiri Engineering and Design

    Sorry - I am not, Wingz...

    I have tried to explain you the fundamental problem with your idea. What you have envisioned, the way you have envisioned it, is not physically possible and will surely not work for sailboats. It's all about understanding some elementary laws of physics. You are thinking two-dimensionally, but a boat is an object free to move in 3 dimensions, with 6 degrees of freedom. Doug Lord has tried to explain you the same thing with graphical examples, and I applaude him for patience and effort.
    Nevertheless, you keep on sticking to your idea. Which means that the only way you can be convinced is to let you build that prototype and see with your eyes. Keep us informed.

    As about possible use on commercial motorboats, I am affraid that current stabilization systems are much simpler and occupy less internal space, as Apex1 has pointed out. So... sorry mate.

    Anyways, don't let this failure (yep...) stop your creativity. Keep thinking and inventing, but don't forget that everything in this world is subject to laws of physics, and you should try to comprehend them better if you want to come up with something practical and useful.

    Cheers mate
     
  2. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    ================
    Wrong. I've taken the time to try to communicate with you-it seems like you should , at least, read what I wrote.





    Non-keel ballast at twice 8 knots illustrated/ DSS25 foil, again:
     

    Attached Files:

  3. apex1

    apex1 Guest

    Senseless Doug,

    just another stubborn "inventor" of a triangled wheel....................
     
  4. Wingz
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    Wingz Junior Member

    I have read what you wrote, several times. And what you are telling me is nothing new. That there is ballast, there are various forms of movable ballast, and that no other solution is possible.

    There are two problems here. One is leeway, or side slip. The other is roll control. If I take side slip out of the equation by mounting extremely large and thin longitudinal fins to the bottom of the boat, so that all side slip caused by the wind is eliminated, and the only leeway left is due to current drift, then we can concentrate on roll control alone.

    If then, given sufficient speed, I extend the starboard wing, what will the effect be?
     
  5. CutOnce

    CutOnce Previous Member

    There is a world of difference between reading and understanding.

    You appear to be closer to understanding now that you've acknowledged side slip as a problem.

    The "fin" you are proposing to counter the "side slip" is effectively a foil section that provides enough sideways "lift" to counter the boat's tendency to slip to the side. Without the side slip "fin", the boat goes sideways.

    The "wing" you are proposing is a foil section that provides your "counter-heeling" force - directly opposite to the force produced by your anti-side slip "fin". Two opposing forces cancel each other out, and the result is a boat that heels, and goes sideways.

    --
    CutOnce
     
  6. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    The effect will be a big total drag, due to full-length shallow fin and due to high wetted surface of vertical fin. Where is the advantage then?
    I can see no improvements with regards to the current state of art of keel / ballast righting systems.
     
  7. Cheesy
    Joined: Aug 2008
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    Cheesy Senior Member

    Im betting that you wouldnt.... I would also predict that the GPS and magnetic compass bearings will be closer than your intended design and you may go faster as well. I think that what is happening with your setup is that you are effectivly using an asymetrical foil at a negative AOA which is allowing the boat to sail, it will produce a lot more drag than a conventional foil though, that is why I am predicting it will work (well sail better anyway) the opposite way to what you intended
     
  8. Wingz
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    Wingz Junior Member

    Well, if you had some spare time and thought you might need a bit of a vacation, maybe you could round up Doug Lord, Daiquiri and some of the other posters to come here and help me prove that one way or the other.
     
  9. CutOnce

    CutOnce Previous Member

    I'd agree with Cheesy here. Basically the result would be a higher drag implementation of what effectively is a gybing centerboard design - with augmented lift to windward due to the (wrong by you) asymmetrical "wing" in use. You'd probably see less leeway and better lane holding.

    Since you haven't acknowledged or appeared to understand all the folks here trying to help, I'm done trying. Ask yourself why all these folks are not in agreement with you? One possibility is that they may be right.

    --
    CutOnce
     
  10. Wingz
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    Wingz Junior Member

    Actually, what I have seen here in my most humble opinion, is every attempt to avoid, evade, circumvent, confuse or negate the idea without ever answering the question directly. I think we have a bunch of politicians here.

    The question is: If we eliminate side slip caused by the wind to the greatest degree possible, using flat non foil fins, and with sufficient speed I lower my starboard wing vertically down, that has a foil shape on the starboard side only, what will be the effect?
     
  11. CutOnce

    CutOnce Previous Member

    Wingz:

    You've got your answers. The foil you think of as "flat non foil" to stop side slip is NOT operating in isolation and you can not think of it as one problem solved and then you address another. It IS a foil, and the foils interact whether you choose to acknowledge it or not.

    Solving one problem ALWAYS causes another. Adding a "flat non foil" keel to a boat stops the side slip problem, but causes a heeling problem - the boat can't slip sideways any more. Keels, centerboards and daggerboards CAUSE heel.

    Adding your "wings" affects how the "flat non-foil" works and the keel affects how your "wings" work. In airplane terms , these interactions are all happening on the roll plain. The keel causes a "heeling" force (lift to windward), and the "wing" causes a "non-heeling" force to leeward. These forces cancel each other out, as they are both affecting the roll axis in opposite directions of rotation.

    You can't isolate parts of a system and evaluate performance in isolation. All foils under water work together and can not be considered in isolation. You seem to think that ONLY the sail is causing the heeling, but you are dead wrong. Without the keel, the sail just causes the boat to go sideways with little to no heeling. Adding the keel causes the boat to heel, and the boat to no longer go sideways. Adding your "wing" will defeat the keel and the boat will slow and develop severe leeway. It is simple vector physics.

    No one has been evasive here except you avoiding the effort to understand what people have been trying to tell you. Make a simple model and you will get it. Use a pencil and apply forces on the roll axis
    .

    I can't think of any more simple way to explain this.

    --
    CutOnce
     
  12. FAST FRED
    Joined: Oct 2002
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    FAST FRED Senior Member

    A couple of years ago , when discussing the Atkin boats with reverse deadrise and box keels (power boats) , my suggestion was for a very wide center board trunk in the box keel..

    The "center board" could be angled by machinery (or foot treddle) to create force resisting the roll. Of course the board would be shaped to this goal, and the "center board slot would be wide enough to allow the board take a good useful angle of attack.

    Like most boards it would pivot up to suffer no damage on grounding.

    To install a similar device on the bottom of a common keel would require the keel to be special built from the start , and higher loads to be anticipated from the extra depth.

    Would not this solve the problem from the first post?

    FF
     
  13. Wingz
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    Wingz Junior Member

    That sounds to me like the basics of a rotatable keel system which seems to have some merit. If we take a boat at speed and extend simply a flat board down below the boat, and then turn that board, the water striking the forward surface will provide anti roll force. On the other side of the flat board however, will be turbulence and drag which on a power boat might be a minimal problem.

    I know there was some work done on this in the past. As I recall one idea was an asymmetrical foil keel that could be rotated either direction, up to its' stall angle of 8 - 10 degrees. This uses the fluid dynamic forces of a foil rather than the blunt impact force of the water striking the board to provide roll control. Another was a keel with flexible sides and two internal bladders that by controlling air pressure could vary the foil shape from side to side. Yet another was a keel with two flaps, one just under the boat, the other near the bottom of the keel. The upper flap to control leeway, and the lower to control roll.

    As far as the leeway problem, I am banking on the idea that at speed, one wing extended fully will provide roll control, and the other extended partially will provide leeway control, with directional stability provided mainly by the lesser extended wing. If that proves inadequate, then dagger board or center board fins fore and aft should solve the problem.

    I think your idea is definitely in the right direction.
     
  14. BATAAN
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    BATAAN Senior Member

    The problem with all of these things is what happens when it breaks? Does the boat become uncontrollable? Many times I replaced the hi-tech bearings in ocean racing sailboats spade rudders and have trouble accepting that this gadget would work for any sort of long-term use in the real world with its constant unexpected nautical surprises.
     

  15. Wingz
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    Wingz Junior Member

    This is my biggest problem. As I mentioned somewhere above, my first time in the water, I snagged my rudder and tore it loose, requiring a rescue. Here in Mexico I am plagued by the inability to find parts or quality materials. In spite of the name - North American FREE TRADE Agreement, if I order something from the U.S. customs adds a tariff that nearly doubles my cost, then adds a value added tax of 16%.

    Sailboats here are few to non existent, which means that parts and materials that are normally available elsewhere do not exist here. As such a whole lot of 'make due', improvising and scavenging is necessary just to get the basic workings. Fiberglass, for instance, is only available in a woven roving and a chopped strand mat, the weight of which is questionable as that the vendor does not know that it is made in various weights. Metal work is confined to a torch, hammer, drill and hacksaw. I could continue with stories about this for quite a while.

    So my biggest problem is how far can I go this time before it breaks.

    I need some help here, sponsors, investors, knowledgeable hands on, contact me directly. twest@tampicoventures.com
     
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