Hinged Bruce Foil Proa

Discussion in 'Multihulls' started by Manfred.pech, May 7, 2013.

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  1. Manfred.pech
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    Manfred.pech Senior Member

    [​IMG]

    First German selfadjusting hinged Bruce foil proa is sailing in southern Germany. A young guy calling himself "loony" built her from two old catamaran hulls with superbly finished craftsmanship especially in welding stainless steel. More pictures can be found here (please scroll down pg 1 and 2): http://www.boote-forum.de/showthread.php?t=119396&highlight=proa

    She will be a testbed for further development.
     
  2. Manfred.pech
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    Manfred.pech Senior Member

    Tests

    There have been first tests under a 4hp motor on river Rhine. Best speed was 17km/h (9,2kn or 10.56mph) which seems to be a good result for the 6,5m main (1:20) and the 3m ama (1:10). Loony found 83% of drag at the main hull and 17% with the ama. The Proa was runnig straight ahead without corrections of motor or rudder.

    Adding the hinged Bruce foil there was only a very slight tendency to luff and the drag was low. The drag remarkably increased when the motor was turned a bit to simulate the sailforce on the foil.
    The best position for the foil was to lift it in the front 2cm and to luff 2cm.

    In my opinion the main hull has a slight Kiribati Dimple and is running very well though it is made from two catamaran hulls.
    [​IMG]
    [​IMG]
     
  3. peterAustralia
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    peterAustralia Senior Member

  4. proagenesis
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    proagenesis Junior Member

    hinged vector fin proa

    hello ....

    I have been working on a modern proa concept > since 1979 .....

    becoming a vector fin proa around 10 years later !
    see on http://www.proagenesis.org >>
    the small white model a ways down on the page

    then becoming a manned size 23'in 1995 > later in 1997 a 31'
    see as well information on http://www.proatech.org

    and since 2001 we are working on a hinged vector fin proa >
    see on http://blog.proagenesis.org

    if we can help with answering any questions ....
    you can do so here or via email

    http://www.galacticdesign.org

    regards fritz
     
  5. Manfred.pech
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    Manfred.pech Senior Member

  6. upchurchmr
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    upchurchmr Senior Member

    Looks like a Bruce foil to me, just with additional complication.
    A rose by any other name.....
     
  7. tspeer
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    tspeer Senior Member

    There's actually a significant difference. As the ama lifts up, the foil stays in the water, drooping down on the hinge. That changes the dihedral angle of the foil, raising its line of action. That generates an additional down-force on the ama. So there is a stabilizing feedback mechanism between heel and the foil. The farther outboard the hinge line, the greater the feedback gain.

    Without the hinge, the foil lifts out of the water as the boat heels. A hooked foil will change its line of action because there will be of the more vertical area and the horizontal area will remain the same. But the total area will decrease. With a hinge, the whole area can stay in the water and all of it changes orientation as the boat heels.

    It's worked well in models. I haven't seen any data on it from full-scale craft.
     
  8. upchurchmr
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    upchurchmr Senior Member

    A properly designed "Bruce Foil" is set up to where the boat doesn't heel. Never mind.
     
  9. John Perry
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    John Perry Senior Member

    Not even if the crew accidentally moves to the wrong position in the boat, or is forced to do so for some reason? - or if there are big waves and the foil skips out of the water so that lateral resistance falls onto the hull or some other immersed part? The hinged version would seem to add extra security. Giles Whittaker made a number of models with the hinged arrangement a good few years ago, others may have done similar. Video film showed that the models made by Giles did work remarkably well. I think it is an interesting idea and Tom Speer has explained it concisely in his post above.
     
  10. proagenesis
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    proagenesis Junior Member

    thanks ......

    ...... we will soon have a 31' hvfp tested > but I expect no real supprise in data !
    since the difference in scale is minimal for the action .....

    thanks a lot for your remarks about this > the critics we can simply forget
    there are billions of them > so never mind them !

    thanks as well to john perry for re marking about other test with models >
    http://www.proatech.org > all the 100 xxxxx files you can check out ......

    regards

    proagenesis
     
  11. Manfred.pech
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    Manfred.pech Senior Member

    To understand the hinged Bruce foil it might be helpful to read the info of Prof. Hagedoorn who invented it as far as I know in the sixtees of the last century.

    [​IMG]

    [​IMG]
     
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  12. proagenesis
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    proagenesis Junior Member

    a few remarks on the above ....

    a flat plate is not self adjusting > but totally erratic >
    going ever more out > if gone some out !
    going ever more down > if gone some down ....
    the only limit .... the force it can create !

    especially on a hinged foil .....
    so any drawing showing such > not even to be .....

    a curved plate is self adjusting >
    if the radius of the circle is much smaler then the hinge point is away !
    in this case the boat ....

    but a fixed fin has to follow the waves > dragging the out rigger up and down with it !
    using up energy to over coming this rotational inertia
    and creating discomfort to the crew .... especially in short waves ......

    this can be improved upon ... by having more draft on the vector fin >
    and the neccessary increase in boa ..... but the use of the boat is then some what limited
    because of these parameters

    the hinged curved lateral area > has as well to have a radius > much smaller
    then the distance to the hinge .....

    additionally > the hinge has to have some play > or being flexible > see http://blog.proadesign.com
    or the angle of attack will be becoming negativ > as soon as the boat will squat on taking up speed !

    further more ..... having no float at the hinge point >
    will leave the main hull free to roll either way > in a real environment

    ever though .... the vector diagram shows it will be stable > but not in a swell > with not much wind .....
    for example .... so there is definitly .... a need for one !

    only then is the set up safe > see > http://www.proatech.org > the very first file

    if we have not the proper angle of attack >
    we would not see more the a second of this ... sailing test video !

    if any one has any question about all this > feel free to ask .....
    here or via email ...

    regards

    proagenesis
    .
     
  13. proagenesis
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    proagenesis Junior Member

    hello .....

    if we are looking at a trimaran from under oder above ....
    like take a look at the tread >>>> " capsize " here at " multi hull " !

    we are seeing a square or rectangular structure !

    being not as easy to build and have the neccessary strenght
    as a triangular or pyramid form >>>

    of the hvfp > just take a look and see !
    this we can build at a fraction of the weight and money

    or a lot longer hull for the same effort as any other principle
    having a lot higher hull speed ..... a lot wider boa


    regards the team of proagenesis

    .
     
  14. proagenesis
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    proagenesis Junior Member

    tom speer

    we have been learning a lot from your research .... about 2 way foils !

    and now may be the time to asking you > what you think about our work ?
    like the hvf at http://blog.proadesign.com

    the section being about finished 1" thick and at the wl not quite 2 ' long
    we have been making all of the curvature the first 4" on the wind ward side
    the rest flat and ....

    on the lee ward side just a round radius of 1/4" .... the rest as well flat

    does this sound ok to you ?

    regards proagenesis
     

  15. spidennis
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    spidennis Chief Sawdust Sweeper

    ...... watching with interest .........
    and would like to know how this boat is working out!
    (his site is all in german, oh well)
     
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