Flying Canting Keel-Extraordinary Innovation!

Discussion in 'Sailboats' started by Doug Lord, Jan 3, 2010.

  1. Doug Lord
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    Doug Lord Flight Ready

    =====================
    Not sure I get the point. As best I can tell "Lateral Resistance" in sailboat design would refer to a means of generating a force to resist leeway. The form of drag originally referred to by "once" was not "lateral resistance".
     
  2. groper
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    groper Senior Member

    the design of this thing is amusing... i fail to see the point?

    Assuming this things keel is designed to 'fly' above the water line, then what you have is essentially a catamaran... a poorly designed catamaran at that because you have all the crew on the lee hull and heap of dead weight on the windward hull!

    So unessesary weight and added complexity.... i havnt read all 8 pages, but unless im missing something whats the point of this thing?
     
  3. Doug Lord
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    Doug Lord Flight Ready

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    Speed. It's a way to increase the speed of a monohull.
     
  4. CutOnce

    CutOnce Previous Member

    Doug:

    Okay, so yesterday's simplified discussion may have penetrated the fog a tiny little bit. Here is today's:

    Imagine a CBTF boat on a very light wind day. No point in canting the keel, unless it is to leeward a little to help put shape in the sails. Although the twin steering foils are providing all the lateral resistance needed, the canting keel is still a foil, and it is still providing a percentage of lateral resistance as it is pretty much vertical, and it has a foil shape. How much lateral resistance depends on the area of the canting keel strut, and the comparative area of the twin foils (ignoring the hull for discussion purposes).

    As long as the canting keel is not perfectly horizontal, it will be providing some degree of lateral resistance. Make a vector diagram, just like you are constantly reposting for the benefits of windward heel, and figure out the math. Lateral resistance approaches and reaches zero as the canting keel strut reaches horizontal. As the canting keel strut (foil!) approaches vertical, lateral resistance contribution increases. Simple. Undeniable.

    There is no magic quality to the steering foils in that they somehow remove the lateral resistance, drag and lifting foil properties from the canting keel strut. The lateral resistance developed by the canting keel foil strut may not be needed (or wanted) but it is there.

    My best guess is that you are only considering the extreme case of fully deployed canting keel horizontal to windward, and fully functional steering foils doing the job as they were designed. In this case, the canting keel is providing no lateral resistance. The third party source (CBTF Inc.?) you are quoting as validation are most likely also referring only to the fully deployed condition as well. I'm sure they've oversimplified things to make understanding CBTF easier for the average bear.

    If you choose to accept the clear logic of this, it becomes apparent that CBTF boats most likely display average to reduced performance in very light winds, as the added drag of the canting keel, plus the twin steering foils may exact a penalty compared to conventional designs. The very clear benefits of the canting keel only becomes a factor when the wind pressure allows it to work in it's optimal configuration.

    The subject(s) of this thread take the optimal configuration one step further - lifting the canting keel out of the water to remove the wetted surface area from the equation. Since the bulb may be beyond horizontal, the righting moment may actually be reduced a little, but the reduced wetted surface area more than makes up for that. The benefits of the canting keel are predicated on the assumption that the wind pressure allows optimal deployment of the keel - but in the real world wind pressure varies, and wind shifts exist. During maneuvers the canting keel is immersed, and when it is immersed and vertical, it is subject to all the same issues (and physics) a normal keel is.

    Using hydraulic power to force the canting keel laterally through dense water adds yet more complexity and encounters resistance as explained in yesterday's paddle discussion.

    --
    CutOnce
     
  5. CutOnce

    CutOnce Previous Member

    Rather than poorly interpret the material posted by others, try thinking for yourself and experimenting. Your interpretation of CBTFco's technology is quite different than mine. I saw no bold, red proclamations of 100% elimination of keel strut lift, lateral resistance etc. on their site. The CBTFco site was quite careful and scientific about their representations - and quite credible. The information they posted was optimized to make their presentation appealing, but they did not deny physics or reality as you have.

    Nowhere in CBTFco's site does it conclude that lift, lateral resistance and drag is eliminated from the canting keel strut. Reduced - yes, due the smaller chord they mention but nowhere do they say eliminated as you have concluded.

    Doug, your understanding of basic science is suspect. I'm certain if you ask one of the principals of CBTFco to read this thread and comment they will quickly acknowledge my sensible and reasonable interpretation of the issues. They will also quickly acknowledge that your "zero" lift, "zero" lateral resistance position is not correct.

    Don't believe me? Go ask them to join the discussion and post their opinions. They seem like cautious, scientific and balanced representatives of interesting technology. I'm perfectly willing to submit all my comments for critical review by the developers of the technology. I have absolutely no doubt as to the outcome. If you don't ask them, perhaps I will as you are misrepresenting their technology and overstating the benefits while ignoring physics.

    Put up or shut up.

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    CutOnce
     
  6. Doug Lord
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    Doug Lord Flight Ready

    You're amazing! The designers and patent holders of CBTF themselves say that the strut is designed to NOT develop lift!!! The strut does NOT develop lateral resistance. It's on their site, I heard it in person, and I built several models to their specs that all worked like a million dollars. Stop trying to rewrite the physics of CBTF! You don't get it......

    What you fail to understand is that the design of the strut does not eliminate drag, it eliminates induced drag, the drag that is produced due to lift. It reduces the wetted surface of the strut. This is the critical element of CBTF and the reason for the twin foils in the first place(in addition to eliminating crabbing of the hull and improved windward vmg). It is also why CBTF is so very ,very fast.


     
  7. CutOnce

    CutOnce Previous Member

    History changed .... again

    I notice Doug has deleted the post I quoted above. Another case of revising history. Thankfully I quoted it before it was deleted. I stand by my observations.


    NOTE: added at 10:15AM to avoid another post:

    Now he's edited his last post again. History is changing faster than the original events. Weasel words added a few minutes ago are gone. Do we have to quote every post made by Doug to keep his original words intact for five minutes?


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    CutOnce
     
  8. Doug Lord
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    Doug Lord Flight Ready

    Flying Canting Keel

    Expecting to hear from Guy Whithouse momentarily(more or less) on testing of the Whitehouse-Richards concept. Said he will send pictures!
     

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  9. CutOnce

    CutOnce Previous Member

    Thank you. I've obviously left you with a serious impression!

    Hmmm. Let's think about this. A streamlined, symmetrically foil shaped, strut, designed to operate in a fluid medium with minimal drag. Can you design "out" lift? (using some special NACA no-lift section!) No, you can't. You can try to minimize lift but you can't avoid lift entirely, unless you want to place a problematic high drag/no lift shape in the stream. By angling the steering foils so that leeway is eliminated, you can theoretically reduce lift on the keel strut by keeping the flow at a 0 degree angle of attack, BUT (and there is always a but) now you have three foils in the water with two of them at a different angle of attack to the flow than the keel strut. I'm sure it is possible to play with the steering foils to minimize lift on the keel strut - but the lift avoided there shows up as a drag increase due to the difference in angle of attack of the foils in the flow stream.

    If the canting foil is operating in it's theoretical best position horizontal (or lifted out of the water), there is no lift contribution, and the twin foils operate without the drag of conflicting angles of attack. Read back a few posts and you'll see I already said this.

    Given the designers and patent holders seem like smart folks, I doubt they said the keel strut is "designed" to avoid lift. Minimize lift perhaps, but not eliminate it, as the desire for low drag and high strength in this application demands a foil-shaped appendage to support the high density bulb.

    On the CBTFco website's Technology page, here is the only quote I see that refers to this topic:
    Funny, but I don't see unequivocal denials of lateral resistance as you do. Perhaps they have special pages visible only to you, or secret text that I'm not finding. Then again, perhaps you are reading or hearing the things you want to hear and see.

    There is no such thing as "the physics of CBTF". Period.

    Doug, everything operates according to one set of rules, not different rules for different technologies.

    Now you get interesting and out come the weasel words trying to distance yourself from your earlier proclamations (likely edited/deleted out by now), as you have probably figured out by now you are on thin ice.

    You must have missed CBTFco's major point that the canting keel reduces the need for ballast by 25-50% for a given rig. This reduction in displacement and weight allows faster acceleration (remember F=MA from middle school?) and more rig power for a given displacement. My read of the CBTFco's technology leave me with the impression they have a pretty good handle on the significant sources of the benefits in their design. I did not see "Elimination of lift and lateral resistance from the keel strut" as one of their major benefits. What browser are you using? Maybe mine is defective.

    I take from their text that the placement of the twin foils in high pressure areas fore and aft of normal keel placement increased efficiency and reduced wavemaking drag. This is the reduced induced drag they seem to be referring to, but I'd love to hear from one of the designers to confirm this. Given that wetted surface area presented is less than or the same as a conventional design, it seems to indicate the reduced keel strut area is most likely compensated for by the addition of the two steering foils.

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    CutOnce
     
  10. Doug Lord
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    Doug Lord Flight Ready

    ======================
    When the words: " it is not required to generate lift like a conventional keel" are used it means that the strut is NOT designed to generate lateral resistance and is designed to be able to use a short chord ,thick, non lifting section . Again, the twin foils generate ALL lateral resistance in the CBTF system. Period.

    =======

    A) Peter DeAnjou, Sailing World review of the Shock 40 CBTF-- http://www.sailingworld.com/sailboats/schock-40-0 :

    "Just so there’s no misunderstanding, this is not a canting keel—it’s a canting ballast bulb. The stainless steel foil supports the bulb, which provides the righting moment. The twin rudders provide lift and prevent leeway ."

    ===============

    B) Bill Burns, CBTFco, http://www.cbtfco.com/Company.html :

    CBTF Co., formerly known as DynaYacht, came to fruition when Chuck Robinson, Alberto Calderon, Bill Burns, Matt Brown and Peter Isler joined forces to create a radical new appendage design that uses a canting ballast for righting moment and twin foils - one aft of the keel - for side force* and steering functions of the yacht.

    *for those not up on sailboat design terminology side force=lateral resistance.

    ===============

    C) Bob Perry, Sailing magazine, http://www.sailingmagazine.net/boats/3-perry-on-design/110-cbtf-52 :

    The lift*, usually provided by a keel, is shared between fore and aft rudders. The "keel" is basically just a strut to hold the canting ballast bulb.

    * for those not up on sailboat design terminology, lift(in this context)= side force=lateral resistance.

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    The End

    > Picture: CBTF plaque* awarded to DL for model development work, including commisioning the first professionally designed CBTF RC model-the F100 (by Graham Bantock),and for defense of and explanation of CBTF on numerous forums. DL was awarded an exclusive license to produce CBTF RC boats in 2003 which ended when the company ceased rc model production.
    * this is the same carbon plaque that is installed in every CBTF boat that has paid the license fee.
     

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  11. groper
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    groper Senior Member

    you blokes are amazing... arguing over the semantics of "reduced vs eliminated"... we get it, the canting keel strut provides *almost* no lift, its negligible... im glad you both agree on this...dont suppose you can move along now can we?
     
  12. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

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    Sometimes it goes that way. I'm still waiting to hear back from Reichel-Pugh about the system on "Q" and from Guy Whitehouse on the Whitehouse-Richards flying canting keel. More info as soon as I get it.
     
  13. yachtie2k4
    Joined: Jun 2004
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    yachtie2k4 Anarchist

    HOW DARE YOU USE MY IMAGE, u have no right to use my image, i have no knowledge of you asking to use my image. please remove that image and all images that have been taken by myself.
    thank you
    yachtie2k4
     
  14. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    ==========================
    As best I can tell those images(in post #76) were taken by Andrea Francolini and duly credited in post #47. They were also used on many other forums with due credit. If one of your pictures was included by mistake ,please specify exactly which one and I will try to get it removed.
    They were published on Sail-World: http://www.sail-world.com/index.cfm?Nid=84072&refre=y&ntid=0&rid=4

    UPDATE: The middle pix in post 76 is y2k's. My mistake for failing to give credit. From here: http://forums.sailinganarchy.com/index.php?showtopic=122364&st=0
    --
    UPDATE # 2: The image has been removed.
     

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

    Flying Canting Keel-Extraordinary Innovation

    Potential combination of technologies:

    While CBTF has proven many times over that it is the fastest system for a canting keel their original keel cant angle was 55 degrees. With the flying canting keel that angle is upped to 90-110 degrees or more. Yet the advantages of the twin foils remain.
    If we look at the second CBTF patent it shows a keel that is NOT a strut but a lifting foil designed to create downforce with the keel at max angle -but still in the water-further reducing the ballast requirement. To my knowledge this version has not been built.
    Now, as time has gone by a new technology has emerged to increase stability
    DSS- a sliding foil(see the Quant 28 thread) http://www.boatdesign.net/forums/sailboats/quant-28-foil-assist-keelboat-dss-38421-2.html
    So what if we take the flying canting keel, the twin foils from CBTF and Hugh Welbourns DSS and combine them all in one boat!*
    Advantages:

    -- The CBTF-like twin foils allow "collective" steering eliminating leeway drag from the hull as well as reducing drag further by placement of the foils on the hull.
    -
    -- The flying canting keel 100% eliminates drag from the keel and bulb.
    a. would be ideal to be able to quickly adjust the horizontal keel in and out-probably easier on a system like this where DSS develops significant RM.
    -
    -- The DSS foil can increase RM significantly allowing even greater reduction
    in the ballast carried by the keel bulb. This is probably superior to the second CBTFco patent when coupled with the flying canting keel.....
    -
    -- When used in combination with high dihedral racks with designed in buoyancy the self-righting characteristics may be improved.
    -
    -- Any others?
    * UPDATE 7/2/11 : There will be an additional technology that can be potentially "blended" with the above and that is on-deck movable waterballast in a dynamic pressure, pumped or sliding tank system. Such a system was considered years ago by Julian Bethwaite and by Sean Langman in conceptual systems for ocean going speedsters.(see pix below) This is an exciting era in sailboat design and development and when the economy really turns around wild, new and exciting projects will spring up all over the place. Hope I get to see it!

    =============
    Disadvantages:

    -- not as fast as a full flying keelboat foiler,
    -
    -- ballast could be reduced so much that the self-righting characteristics that are ideal in a keelboat are compromised. Analysis of the effect of racks with buoyancy would be important.
    -
    -- Relying on buoyancy in racks may not be acceptable in ocean racing rules.
    -
    --Any others?


    click on image:
     

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