New High Performance Monofoilers

Discussion in 'Sailboats' started by Doug Lord, Dec 19, 2008.

  1. Doug Lord

    Doug Lord Guest

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  2. ancient kayaker
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    ancient kayaker aka Terry Haines

    I find myself becoming more and more interested in these strange craft. Perhaps you would answer a few simple questions for me.

    What distinguishes a class B foiler? What other classes are there?
    I notice sailing foilers have surface piercing Vee foils or fully immersed foils. Do these provide heeling resistance or is that entirely done by body weight in the smaller boats?
    The foil can lift the hull surprisingly high out of the water without breaking the surface; is that to accommodate wave height or to make manual height control less critical?

    I have also seen ladder foils and surface skimming foils but only on power boats.
     
  3. Doug Lord

    Doug Lord Guest

    Here's a link with speed sailing classes: http://www.speedsailing.com/Background_records.htm
    This is an excellent article by Greg Ketterman(designer of Longshot and the Hobie Trifoiler among other things) about his design philosophy and why he thinks fully submerged foilers are better than surface piercing foilers at least in small sizes. http://www.hobiecat.com/sailing/TriFoiler History Original/Magazine Articles/Multihulls 1990.htm
    ---------
    Surface Piercing foils generally don't provide RM-their RM comes from the distance the CG is from the center of lift. Thats why Hydroptere uses movable water ballast. Fully submerged foils (on multifoilers NOT monofoilers) can develop RM up to the structural limits of the boat. Surface piercing foilers can have the advantage because the area they use is regulated by speed so they can sail at optimum wetted surface all the time whereas fully submerged foils can have too much area sometimes. On small multifoilers the fully submerged system may be best for high end speed because of the virtually unlimited RM.
    The first Moth to win a race back in 2000 sailed on surface piercing foils but they were outlawed as a "multihull configuration"-the guy that did it reckons that with the same development time as Ilett's wand based system they would be competitive or faster today...
    Keep in mind(as demonstrated on the I-14) foils can be beneficial without fully flying the boat. If I remember correctly Tom Speer once said that if the wetted surface of the boat is reduced by 4 times the planform area of the foils there is likely to be a net gain.
    ----------
    Pix below Andy Patersons surface piercing foiler-may be the first Moth to foil.
    White boat is Brett Burvills Moth first to win a race on foils... And Bora Bgulari
    on a bi-foiler Moth....
     

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  4. gketterman
    Joined: Dec 2008
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    gketterman New Member

    Doug, I appreciate your posts. I do not always see everything that is new on the internet so it is good to see a summary like this.

    It is also good that you share your ideas. It is unfortunate that so many are so quick to put down new ideas on this forum. This forum could be a very good means of brainstorming and everyone knows that the first rule of brainstorming is you do not put down any idea.

    I appreciate your enthusiasm for hydrofoils. It is taking a long time but hydrofoil development is accelerating. I believe there will be some real innovations with hydrofoils that will make sailing much more interesting.

    Greg Ketterman
    Vice President of Engineering
    Hobie Cat Company
     
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  5. Chris Ostlind

    Chris Ostlind Previous Member


    Welcome to the Forum, Greg.

    It's one thing to brainstorm and it's another thing entirely different when the so-called, brainstorming is factually innacurate, excessively effusive and completely one-sided. What is the result of brainstorming when the baseline data being used to concoct the source idea is faulty?

    Being an engineer, certainly you understand all too well, that there has to be a balance in that thinking, or things get quickly off-track?
     
  6. bistros

    bistros Previous Member

    Well, that's truly scary. VP of Engineering at Hobie Cat and he needs to get his innovation information from Doug.

    The I-14s pictured are older than time. The older moth pictured a couple posts ago is ancient. The Hobie Trifoiler is from the last century, and if I recall correctly, wasn't exactly a barn burner in the sales department. Most of Doug's photos showing the "breadth" of foiling development are of one-off projects that have no volume potential.

    The only significant growth in foiling in sales volume has happened in the Moth development class. Almost every other sailing class (18' skiff, 16' skiff, 12' skiff, I-14, B14, IC, 49er, 29er, RS800 etc.) has specific prohibitions written into class rules preventing class-sanctioned racing using hydrofoil technology to lift the boat out of the water.

    These prohibitions are for good reasons:

    • foiling isn't easy
    • it significantly increments the arms race and obsoletes boats
    • not everyone is thrilled with the idea of foiling
    • kills resale value on existing fleet (and fleet growth from re-cycling old boats)

    Brainstorming is not sitting around a fire singing Kumbayah while accepting every idea is wonderful and great. It is a tough, competitive, trial-by-fire arena in which peer review of concepts happens. More importantly than the arena for discussion is the need to actually design, build and sail boats. This is Boatdesign.net, not HappyFoilingCheerleaders.net, so expect people to look at ideas critically.

    All ideas are very welcome here - but re-posting the same old crap over and over again to a new audience isn't news.
     
  7. Chris Ostlind

    Chris Ostlind Previous Member

    (pre-empting the argument)

    Wait for it, now...

    Doug's going to come on here and complain about the disrespect, the insolence, the absurdity, the asininity, the just plain silliness of arguing a collection of points with Greg, as if he doesn't get plenty of that at Hobie from the other executives and it might harm his persona. As if he never heard anything like this when he wheeled-out the first Trifoiler, or the Mirage drive, or any of the other stuff in which he's had a hand.

    Come-on, Doug, give Greg some credit for being a guy who knew fully well where he might be stepping when he showed-up here. I didn't pose any questions that were out of line at all. They're the kind of things that have to be answered no matter what the brainstorming might be about and Greg is not automatically removed from the process.
     
  8. ancient kayaker
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    ancient kayaker aka Terry Haines

    Doug: interesting end shape to the foils in the middle pic. I presume that's to retain lateral control in the event the boat rides too high. Thanks for staying on the topic.
     
  9. Doug Lord

    Doug Lord Guest

    ----------
    Helps with tracking I would think- as well as acting as a sort of endplate reducing induced drag. Like winglets on aircraft..
    See the pix for a similar tip on hydropteres foils:
     

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  10. bistros

    bistros Previous Member

    Don't worry AK, he's been on this exact same topic for about five years. If you care to use the search feature of the site, you could find the exact same photos, talking about the same foiling "epiphany" moments in every foiling thread he's "helped" (infected) over the years.

    It is like subscribing to a magazine month after month and seeing the same centerfold using the same pictures and stories. If it is the first time you look at the magazine, you think it's great stuff - after reading 2 or 3 issues you start to get sick of it.

    Don't know if you've see the Bill Murray comedy "Groundhog Day", but it sums up Doug's foiling contributions quite well. People on Sailing Anarchy now race to post "GROUNDHOG DAY" once Doug jumps into a thread.

    The foiler in pics 1 and 2 (same boat) quickly precipitated a rule change to render the dual foil design illegal for Moth class racing.

    I'm waiting for the insults and tantrums to start.

    --
    Bill
     
  11. BWD
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    BWD Senior Member

    While on the Hydro subject,
    Regarding those wings:
    wingtips: stabilize vortexes/reduce drag, + a bit o' lateral bite. commonplace, effective.
    dogtooth: reduces cavitation propagation from surface towards root. Stabilizes lift under not-so stable foil yaw and AOA condition. So it doesn't crash, when the boat heaves or pitches.... at least not before it gets up a head of steam ;)
    Perhaps the next iteration will have 2 dogtoofs rather than one?

    The dogtooth is the greater novelty gadget for sure (insofar as I never saw it on a boat before), whether them Frongchez's computamachinations see it the way my speculations do or not. It may be a way forward, controlling the cavitation without adding more draggy fences.
     
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  12. ancient kayaker
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    ancient kayaker aka Terry Haines

    Doug and BWD: thanks fo the info. L'hydropteres "winglets" seem to go in the opposite direction to those I have seen on planes but it would depend on the force vector. I didn't spot the leading edge features, should pay more attention. There are similar features on humpbacked whale fins according which are usually fully submerged, but I have seen similar features on plane wings.

    Bistros: OK, its my first time! I appreciate Doug bringing it to my attention, and it's a lot easier than searching through this ginormous forum even if I knew what to search for.
     
  13. BWD
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    BWD Senior Member

    yeah they do go the other way -time to lay off the eggnog I guess!
     
  14. Doug Lord

    Doug Lord Guest

    The Foiling 18's

    This is most interesting since for as long as I can remember as a kid these boats mesmerized me. There are now two Swiss 18's that have been converted to hydrofoils: the Access 18 and AET(Thomas Jundt). Another 18 is rumored to be on the way. These boats are conversions like the 14's, the RS600FF and early Moths. Not being designed from scratch as a foiler has some drawbacks but these are magnificent machines:
     

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  15. Doug Halsey
    Joined: Feb 2007
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    Doug Halsey Senior Member

    Surface-Piercing Foilers

    I don't really want to send this thread any further off its original subject (monofoilers), but I'd like to clarify a couple of the comments that have been made about surface-piercing foilers (like Hydroptere).

    Actually, surface-piercing multifoilers get most of their righting moment from the lift differential between the windward & leeward foils. As the boat heels, the leeward foil area increases & the windward foil area decreases. If the boat heels far enough, all the weight is supported by the leeward foil, so the righting moment develops in a similar way to a conventional (nonfoiler) catamaran flying the windward hull.

    If the boat did not have the vertical fins at the foil tips, and it heeled far enough to get the windward foil out of the water, then the leeward foil could not balance both the vertical force (L) & horizontal force (S) simultaneously, except when the tangent of the effective, heeled dihedral angle= S / L. Any side force not balanced by the leeward foil would then be shifted to the rudder, so yes, tracking might be a problem. I believe this is more important than any possible tip end-plate effect that might occur.


    To Greg Ketterman:

    Let me second Chris's welcome to the forum. I'm looking forward to hearing your opinions about foilers & boats, in general.

    Doug Halsey
     
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