CBTF(Canting Ballast Twin Foil)

Discussion in 'Sailboats' started by Doug Lord, Sep 25, 2003.

  1. usa2
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    usa2 Senior Member

    You say you have nothing against Maximus yet you have insulted and criticized the owners and designers of the boat. And you still dont seem to understand that unless a court says Maximus has infringed and/or EBS Yachting pays the $87.5K for a license, then the boat is not CBTF. As of now she is considered a TMF boat by the world at large excepting you and CBTFco.
  2. Doug Lord

    Doug Lord Guest

    CBTF Max

    What you don't seem to understand is that the boat didn't do anything the onwers and designers have culpability here. They have, according to people I trust, made a deliberate attempt to directly affect the livelihood of the patent holders of CBTF. The patent holders ,when faced with such a threat, have NO CHOICE under the law but to take aggressive action to defend their patent.
  3. usa2
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    usa2 Senior Member

    well of course the "people you trust" will say they are deliberately affecting their livelihood. I know the boat didnt do anything-but the boat is an inanimate object, so if you are insulting Maximus's owners and designer (who are all sailing on board her) but saying you want the boat to win is going against yourself. Also, do these "people you trust" have names to back up their alleged credibility? It doesnt matter if you trust them, it matters whether they are actually capable of backing up what you and they have said about Maximus.
    If CBTFco sues Maximus but not the other TMF boats, than it will become apparent that the only reason they sued them is because they were in the States for a few days. If CBTF is really an international application as some have claimed than CBTFco would have to follow through and sue the Aussie supermaxis if they have a case against Maximus. If they dont have a case against Maximus then they wont be suing anyone..they may be getting sued themselves. I've heard that Max's owners and designers are extremely annoyed with the American company and may come up with a countersuit. This is going to be interesting. You said that Skandia was "definitely NOT CBTF..." Well, Skandia has a TMF system. Maximus has a TMF system. Maybe the CBTF patent covers TMF systems, that is a possible. They would have to come up with a new name for it though because CBTF does not have anything about trim tabs, or retractable forward daggerboards.
  4. Doug Lord

    Doug Lord Guest

    Preferred Embodiment CBTF

    I imagine most people know by now what the"preferred embodiment" of CBTF is:a boat with a canting ballast strut and two high aspect foils one forward of the canting keel and one aft. The key element of the patent is that the twin foils can both be turned collectively to eliminate leeway allowing the hull, keel and bulb to move straght thru the water instead of sideways like most boats. This allows the keel fin to be designed with a non lifting section.
    Now here is a description of the Maximus foil system:
    The Maximus system consists of a canting ballast strut and twin fore and aft foils both designed to work collectively to eliminate leeway upwind; in other words both foils(the moving parts) are turned the same direction going upwind in order to eliminate leeway.Again, the flap on the forward foil of Maximus is turned the exact same direction as the forward foil on a CBTF boat for the exact same reason and is turned collectively(in conjunction with) the rear foil upwind.
    Isn't that interesting the foils do the same exact thing as CBTF; they are turned the same way at the same time just like CBTF. Sounds just like CBTF.
    Doesn't matter that the fore and aft position is different,or that the forward foil retracts or that the forward foil is like a skeg rudder(flapped fixed foil) what matters is that the forward foil is there for the same reason and does the same thing as the CBTF foils.In order for the Maximus foil(the moving part) to work properly upwind it must be operated collectively with the rudder.That is the essence of CBTF....
    Almost every patent has a phrase that says something like :"this is the preferred embodiment and is not to be construed as preventing other embodiments".
    I know for a fact that CBTF tested this system in almost the exact configuration as it is on Maximus and chose not to use it because they found that the all moving foil gave better manouverability(and other tactical advantages). But twin foils used to develop all the lateral resistance of the boat ,adjustable from tack to tack are part of the patent regardless of whether they are in a skeg rudder(flapped fixed foil) configuration or whether they are all moving foils or any combination thereof.
    Case closed....
    5/30- Well, almost: just took a look at the original CBTF patent for the firt time in a long while and right thre on the front cover illustration is a FORWARD FOIL WITH A FLAP/TRIM TAB! I hadn't remembered that... Now, once again case closed...
    Last edited by a moderator: May 30, 2005
  5. brian eiland
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    brian eiland Senior Member

    Tracking Stability observation

    ....courtesy of Scuttlebutt...

    * From Ray Tostado:
    I find that my mind cannot create an image of a canard
    steering the bow to windward using an oblique canting keel as a pivot
    point. Oh sure, it can be demonstrated, but why bother? A fixed deep keel,
    perhaps. Designers have always sought tracking stability for hull forms. A
    hull has to be inherently wanting to track, rather than wandering
    erratically, constantly in need for rudder correction. D. Peterson's
    application of aeronautical cord shapes allowed a hull form to literally
    move sideways to weather. This was achieved by balancing the hull form,
    inclination, the sail plan, and the keel/rudder interaction. There was
    "lift" in this balance. With a canard the hull is being asked to passively
    allow itself to be "bent" sideways to weather against it own stability
    form. And if the canard is inclined at 15 degrees, what steerage can it

    Has anyone asked the sail plan how high it can point and still have any
    merit? The optimum 26/29 degree angles are old hat. Power is back in and 30
    is just fine, thank you. A conventional deep spade rudder is nothing more
    than a detached trim tab for a high lift keel shape. The keel shape never
    rotates out of alignment to the hull form. A canard does not perform this
    duty. It wants to argue with the rest of the boat. But I must remember. We
    are comparing Cessna 210s to combat fighters in this discussion. There are
    the big guys, then us
  6. DSmith
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    DSmith Junior Member

    It is only his opinion but Dave Hollom states in the latest Seahorse magazine that he sees "no advantage, other than manoeuvrability, in having a forward steerable foil provided that the rule to which the boat rates does not penalise lifting [retractable] foils. The wetted surface penalty, which increases viscous drag, has to be carried upwind and downwind. As, with such a concept, lift is produced in the high pressure area of the boats natural wave system and thus reduces the amplitude of that wave system rather than amplifying it as does a conventional foil situated around the mid-section, there is a reduction in lift-induced wave drag. However, that reduction can equally well be had by placing a retractable foil in the same longitudinal position as the forward rudder, without the viscous drag penalty off the wind".

    Another interesting quote is that if the hull "does not produce lift or produces less lift, as with a gybing board, the board must produce more lift to remain in equilibrium. To remain within its low drag bucket, at a particular operating condition, it must, therefore, have greater area than the non-gybing board, assuming of course that both that both boards have the same width of drag bucket and both sized for the same operating condition".
  7. usa2
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    usa2 Senior Member

    Morning Glory had trouble steering offwind with CBTF
  8. Doug Lord

    Doug Lord Guest


    D, I haven't seen the Seahorse article and I have great respect for David Hollom; he even designed the foils for my F100CBTF Unlimited One Meter model.
    With a canting keel boat as the keel cants the boat needs extra lateral resistance.The CBTF system uses many design points to achieve the necessary lateral resistance with the lowest possible drag. The high aspect foils; their placement and the incorporation of collective allowing the virtual elimination of leeway are important ingredients.By using collective the canting strut can be designed with less wetted surface, by using a 50-55 degree cant angle the boat can be narrower and lighter.All of which works to reduce drag.The twin foils, according to CBTFco and to people that have sailed the boats dramatically improves the tracking of the boat on all points but especially downwind in a seaway.
    But the real fact is that CBTF boats are proven in numerous races to be exceptionaly fast-thats the bottom line. Interesting that three CBTF boats now lead the Transpac....

    2,you're wrong again about Morning Glory at least according to Jim Pugh.There has been no report whatsoever of "difficulty in steering because ther is a canard to control".
    Even your phrasing of that comment shows a misunderstanding of how CBTF works: the forward foil is automatically controlled in steering and ADDS NOTHING to the workload downwind.
    According to CBTFco these boats have MUCH BETTER control in any seaway than a comparable fixed keel boat or one of the rip off systems like Maximus. In fact "tripping over the forward foil" is ridiculous and has NEVER happened.
    But you don't have to believe that just believe the market place: Neville Crichton(sp?) was initially skeptical of CBTF but was won over by the stunning performance of the boats-and he specified CBTF not any alphabet soup("TMF") ripoff.. Neither he nor the owner of Wild Oats would have specifically ordered new multimillion dollar CBTF boats to race in the S-H if there was one iota of truth to your comment.
    And 2 don't you find it curious that there are no "TMF" boats in the transpac? Oh, thats right: they would be seized if they showed up.....
  9. usa2
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    usa2 Senior Member

    Doug, explain to me what Magnitude 80 is.
  10. Doug Lord

    Doug Lord Guest

    Mag 80

    Either paid up, in litigation, or a fixed forward foil-and I guess pretty slow isn't it?
    2, according to Bruce Sutphen of CBTF Mag 80 is NOT a CBTF boat since it has a non rotating forward foil. The owner considered making it CBTF but changed his mind.....
    Last edited by a moderator: Jul 21, 2005
  11. usa2
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    usa2 Senior Member

    Mag 80 didnt use CBTF because the owner decided to sacrifice a marginal percentage of upwind performance percentage in order to be able to fly off the wind.
  12. Doug Lord

    Doug Lord Guest

    Mag 80

    Hows it doing in the Transpac?
  13. usa2
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    usa2 Senior Member

    horrible. Not surprising though. That boat has never performed exceptionally well. Do you have any idea why Morning Glory has 70+ miles on Pyewacket?
  14. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    Praise and damnation.

    It seems like this(cbt) technology is the most effective way to maximise a mono's sailing speed. It is also, arguably safer than others such as water ballast.

    If a cbt boat turtles (180 deg. capsize) it could cant its counterweight (I hesitate to call it ballast) to one side and probably right itself (if the counter weight strut dosen't jamb or break off in the accident).

    Another advantage is that all this wieght is always significantly below water line whereas many of the water ballasted boats I've heard of have had thier ballast considerably above the waterline which certainly doesn't help if, heaven forbid, it should end up on the wrong side of the wind.

    The two major hazzards I can see with this set up are: 1.) the counterweight breaking off, and 2.) it getting stuck all the way out on one side.

    In the 1st case it would be no different than your typical deep draft bulb keeler which faces the same risk. The boat will probably turtle and do so violently. With proper floatation (which should be required for all blue water racing anyway) the hull, free of its ballast, would float higher and may be haditable in this (inverted) condition until rescue.

    In the 2nd, The boat would end up floating on its side. If the hatches and ventilaters are kept close enough to the centerline, the boat may weather this mishap without even flooding.

    The objections I have to this concept are that it seems to: 1.) be costly and complex, 2.) encourage or even reqire deep draft (1/4 draft/length ratio, by the looks of it) and 3.) be very vulnerable to damage from (usually unseen) underwater obstacles.

    I can imagine the Summer haul out list being filled with such boats with broken and dammaged struts and foils if this system were to ever catch on. The unfortunate consequence could well be even more expensive (due to limited supply and increased demand on such facilities) boating for everybody, not just those who use this system.

    For this reason, it is easy for me to imagine this system being widely banned in local racing fleets.

    I think that this is yet another example of a technology (like wing masts and wing sails) that is both effective and impractical. It is therefore, as I see it, deserving

    both praise and damnation.


  15. SuperPiper
    Joined: Jan 2003
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    SuperPiper Men With Little Boats . .

    Draft : Length Ratio

    Draft : Lenght Ratio.

    This is the first time I have heard of this parameter. Sharpii2, did you just invent this measure or has it been around for conventional boats?
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