Canting Keel as a Lifting Foil

Discussion in 'Sailboats' started by Doug Lord, Nov 1, 2011.

  1. Doug Lord
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    Doug Lord Flight Ready

    I found something today that seems rather bizzare in its application though the idea of using the canted keel as a lifting foil has been around for a while.
    In this interview from Scuttlebutt Michel Dejoyeux is describing innovation in the Open 60 class and says:

    An example of the changes that have occurred with the most recent boats?
    MD: "The angle that has been given to the axis of rotation for the keel. The front part is higher up, which means that the keel is angled and can be seen as a foil, which helps lift the boat up. On the Farr designed boats this angle was 2 degrees, but 5 on Safran and now we're up to 7.5."

    This doesn't seem to make sense since angled the way he says it is would lift up ,canceling part of the RM developed by the keel. Maybe they have the most effect from it on a reach and somehow upwind it doesn't matter?
    Any thoughts on whats going on here?
  2. yipster
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    yipster designer

    hi Doug, interesting stuff, like it, its almost a HISUCAT rite?
    long as the bulb stays submerged and dont fly as counterweight
    i dont see why a lifting foil in this config partially should cancel RM.. eh?

    found some RC video's, first one shows she 's really taking off :eek:!
    but although titel here is Canting Keel RC Yacht beginning to foil
    middle of this film has got me puzzled, looks more like
    crossed deep daggerboards or perhaps horizontal foil
  3. Doug Lord
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    Doug Lord Flight Ready

    Thanks, yipster! Take a look at this CBTF patent: they use the canting keel fin for downward lift-to increase RM.
    Heres a picture of a small model of a Moth foiler that uses sliding on-deck ballast instead of a canting keel. Was extremely difficult to control since altitude control was manual-using the radio:

    Attached Files:

  4. Steve Clark
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    Steve Clark Charged Particle

    The blade on Red Herring's keel actually trims nose down as it cants. This is done by the same mechanism, except the aft bearing is higher than the forward bearing. I don't recall the number off the top of my head but it is in the order of 3 degrees. This at least assures the blade is doing nothing as long as the boat is on her normal trim and making "normal" leeway. As she squats at higher speed, heaves and pitches in waves, I am pretty sure that the blade develops both positive an negative angles of attack. In general I would expect that having the blade at positive angle would be bad at least on a boat like Herring that has so little form stability.
    On an open 60, which has tons of beam, and which needs to be optimized for down wind sailing, it may turn out that there is enough form stability reaching and running that they get a net benefit by using the keel blade to reduce displacement even at the cost of righting moment. Unexpected but possible.

    The model would appear to have a T foil canard. It behaves just about as you would expect, lifting the hull and hammer head stalling when it gets too excited. Demonstrating yet again why airplanes have stabilizers on their tails.
  5. Luc Vernet
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    Luc Vernet Senior N.A.

    That's exactly what it has, Steve. Look at these two other videos from this person, who is doing some interesting research using RC model.

    The first video shows how, in an earlier model, he has mechanically coupled the canting keel with the dagger-board moving the opposite way.

    The second video shows the big inverted T foil shape of his new dagger-board (at the end of the video) that he uses in his last model.

    In the second video posted by Yipster here-above, we can see this last model lifting on this foil, but the absence of foils on his (twin) rudders made it go bows up (could have been the opposite!), the foil loose it's lift....and the boat stall and go back to "normal" floating.

    Added: is it normal that the video does not show here directly since I had used the YOUTUBE link icon???

  6. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    CBTF #2-canting strut as lifting foil

    For reference ,here is the pdf of the second CBTF patent wth the canting keel being used to create lift(down) increasing the RM of the boat:

    Attached Files:

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