Hinged Bruce Foil Proa

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

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  1. proagenesis
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    proagenesis Junior Member

    how is texas doing .... now a days ?

    ..... this not the only problem !
    he copied > http://www.proadesign.com

    but with out under standing a lot of the facts ......

    regards proagenesis
     
  2. tspeer
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    tspeer Senior Member

    You'll notice that I was careful to say the computer predicts the performance of the round-edged foils will be good, but I am skeptical about how well they will work in practice. And the constant-edge-radius + arc sections weren't predicted to work well at all. It took very careful contouring of the round edges to get them to work, because their performance depends sensitively on how the flow separates on the two sides.

    It was an interesting design exercise, but I'm not convinced it's the way to go for a real design. I'd be prepared to add sharp edges if the round ones don't work out.
     
  3. tomas
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    tomas Senior Member

    I'm still learning about boating and I was unaware of this design.

    It is a beautiful, simple, elegant and efficient scheme.

    Thank you.
     
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  4. proagenesis
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    proagenesis Junior Member

    ...... thanks for you thoughts ....

    from our tests .... I can say > that a constant radius for the profile > is no good it all !
    because the flow will separate on this ww side > if any stalling condition are in force ....

    so we need definitly a lot more entrance angle at first >
    so the flow will stay on the section >

    the change becoming less and less to wards the center ....

    the end section > seeming not critical .... .
    if > we make the over all section as thin as we can .... from a structural point !

    regards proagenesis


    .
     
  5. proagenesis
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    proagenesis Junior Member

    ...... yes .... this whole idea .... just amazing !

    if there is any thing you cant find an answer for at the many sites
    let us know !

    http://www.galacticdesign.org

    regards proagenesis
     
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  6. Manfred.pech
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    Manfred.pech Senior Member

    Roots

    Yes it is indeed. Dr. Hagedoorn, Prof. of geophysics in the Netherlands, invented the self adjusting foil and Robert Biegler passed the idea to Fritz Roth (proagenesis, proadesign ... and so on) who has the most experience (at least theoretically or with models) with the hinged foil: http://tech.groups.yahoo.com/group/ayrs/message/1220.

    Loony added the idea of variable geometry. When he is shunting his proa the mast is forced forward and the foil backwards to reduce the weather helm of the hinged foil proa. The system is now working perfect as he found out in his test sails on the lake "Bodensee". He is sailing the first hinged foil proa in Germany.

    The idea of the variable geometry proa with a sliding foil seems to be perfected by Mal Smith with his model: http://proafile.com/forums/viewthread/219/. Please scroll down to posting 7 of Mal Smith.

    [​IMG]

    Another father of the hinged foil is Giles Wittacker a retired physicist, who has got it patented as I think. You can read of his "Hapa Stabilised Sail Craft" in Catalyst 13, 2003, of the Amateur Yacht Research Society. You can google with "Catalyst 13 AYRS" and download it for free.
     
  7. proagenesis
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    proagenesis Junior Member

    the real vector fin proa

    is not the one > which has a " variable geometry " >
    since both improvements are not scalable to any great degree ....

    the using of a wind ward sail or the use of small roller jibs
    being a lot more fitting for real use !

    the moving mast and the moving fin > especially the angle of attack being all wrong >
    since the fin will have > on going down as soon as any heeling will be happening >

    having no holding capability any more .....

    soooo .... this will not be working at any thing other then the conditions tried
    flat lake enviroment and wind at 15 - 25ktn

    as soon as the swells > and gusts will be there .... the thing will go over
    and his inventer will get soaked ..... poor thing !

    since he turned out to be an analphabetical >
    not being able to learn any thing from the many .... who have been trying this !

    having thought about this long and hard
    an having decades of experience with the vfp .... principle .....

    for any one wanting to see more take a look at > http://www.proadesign.com
    http://www.proatech.org .... and all the other links .....

    regards
    the team at proagenesis
    .
     
  8. proagenesis
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    proagenesis Junior Member

    tom speer > 2 way section

    your comment about using sharp edges > has brought me onto thinking about the following >

    starting from the lee ward flat plate we will be using a tiny radius
    becoming exponentially ever larger ... till at the center of the section >
    we will be having a radius much bigger then a constant arc !

    the flow separating at the small edge .... having enough force to press it toward the section
    then at the center we dont need this any more > so the flow can be parallel

    what do you think > have you ever tried this in you predition program ?

    regards proagenesis

    http://www.proatech.org
     
  9. tspeer
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    tspeer Senior Member

    This is similar to my P1 family of section shapes, that had a circular radius for the edges and a larger circular profile for the body of the section:
    [​IMG]
    The performance was pretty abysmal.

    I've not analyzed a section with a logarithmic spiral like you describe. Designing a section to a specified pressure distribution results in a continuously varying radius of curvature, but it's not a logarithmic spiral.
     
  10. proagenesis
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    proagenesis Junior Member

    ..... ok

    but basically being first a smaller radius and then becoming a larger ...... ?
    and .... is a constant pressure distribution what we need ?

    I am thinking of conditions > where shock loads .... from ... like waves on the boat >
    are causing a stall ..... at the very beginning of the section ... at the very edge
    for this reason > I think > we need round edges ......

    but of cource asymetrical in function ....
    meaning the problem only exists toward the low pressure side ...

    the section shown ..... seems about right ..... towards point > 0.1
    but then it should flatten out and the most thickness being 20/1

    a finer overall section should not have any problems with the end section then ....
    dragging ....... so much ?


    regards proagenesis
     
  11. tspeer
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    tspeer Senior Member

    That's a bad section. Here's a better section (according to the computer):
    [​IMG]
    I don't think you can look at a section and tell which will be better. The differences are subtle - this section needs to be accurately constructed if one hopes to achieve the predicted performance.

    Section design is all about controlling the boundary layer development by shaping the pressure distribution, and thus shaping the section. The most important thing to accomplish is to avoid having an adverse pressure gradient that is so steep that it causes separation. That tends to happen near the trailing edge, and on the downstream side of leading edge pressure peaks. The rounded edges aim to reduce the leading edge pressure peaks, but suffer from trailing edge separation. That's why it takes a careful tailoring to get the desired characteristics on both ends with the same shape.
     
  12. proagenesis
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    proagenesis Junior Member



    well ok > but this section looks already better to me > even though its .... too thick for me or too short >
    this will depend ... I guess > on the application > what speed envelop ?

    what environment .... meaning > is this for an ac72 sailing on protected waters
    or an effective cruising boat ..... as the hvfp !

    and yes the purpose you describe I agree on >
    but does this ... your program calculate shock loads ?

    from waves into their results ?
    or the movements with in this moving water ?

    so I am certain > those results are limited by their limitations .......

    the other consideration we have here at proagenesis >
    is not to be the fastest or to win any race it all
    but to being as effective as we can >

    meaning > with what amount of funds > materials > can we produce the most boat for .....
    the most lenght > meaning the most comfort on the ocean

    here .... some thing I have been writting up on this subject earlier >

    the edge .... on a section of an ac 72 .... can be sharp or nearly so .....
    because the thing is always going so fast ?

    but on a hvfp ... having not nearly as much sail area >
    and being out on the ocean >

    the flow going from the pressure to the low pressure side > on any sudden load
    and separating at the edge > causing a stall .....

    especially > if we have a radius there >
    because this squishes the flow actually forward > on a sudden load !

    for this purpose > we should be having a larger radius on the entrance
    like an airplane wing > right ?

    but this of course .... not feasible on a 2 way foil !

    so we should have ... a sharp edge on our pressure side >
    and nearly a 1/4 radius on our low pressure edge ?

    going from there .... with a continuosly larger radius towards the center .... ?


    what do you think about this ?
    to me ... it says about the same as you have been saying above ......
    the only difference being .... me bringing in this > un steady fluid

    the ocean


    .
     
  13. raf pali
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    raf pali Junior Member

    I like this concept, I think it would perform well.
     
  14. proagenesis
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    proagenesis Junior Member

    ..... yes .... the hvfp does perform well .... http://www.proatech.org

    but this particular model has never ever even sailed !
    just ask mal smith him self .....

    and this sliding hinge ... well .... what can I say ???

    regards proagenesis
     

  15. proagenesis
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    proagenesis Junior Member


    .. what we have to keep in mind as well ...... http://blog.proadesign.com
    this hvf operates directly on the boundary of air and water

    and where the wl ..... most of the time >

    is where the wl lenght has been made more !
    so the section is around 1/20 there > .... to not create any big waves !

    your section shown above > being 1/10 is about what the hvf is ...
    half way on down ..... towards the tip .... so this would be alright > there .....

    regards proagenesis

    .
     
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