Dynamic stability

Discussion in 'Sailboats' started by Bertil, Dec 8, 2008.

  1. Bertil
    Joined: Feb 2006
    Posts: 33
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    Location: Sweden

    Bertil Junior Member

    To Chris:
    The boat design is ONE 40. You can see it on the net ( I have the yellow one) thats on the net. Designer is Guy-Christer Lönngren from Finland. He also designed the Guy-boats, mostly as mine with a keel that is by hydraulics possible to fold backwards. I have the mast to coal-fiber, standing rig is dynemaa, and a lot of other things.
    To Bistro: I will be back with some answers. Just now wrapping christmas gifts.
    1 person likes this.
  2. Chris Ostlind

    Chris Ostlind Previous Member


    If you had told us from the beginning about the specific boat you have, it would have solved a whole bunch of my concerns from an aesthetic and design philosophy position. The ONE40 is very much for an owner who is already thinking outside the box of the typical norms. I'm sure the boat creates new conversations wherever you may go. I see how the DSS system might appeal to an owner who has invested in the design aesthetic of the ONE40.

    From a technical standpoint, I both admire the swinging (fore/aft) keel form (especially for the waters in which you probably sail) and I have very serious concerns about the use of the DSS foil in combination with the swinging keel.

    Let’s say you were to be sailing along at a fast pace, and encountered one of the many thousands of underwater formations that dot the archipelago environment of, say, Stockholm. Let’s further assume that relied on the DSS foil to provide your righting moment security. I think you could be in for some really interesting problems. This is especially true if you are considering the business of shaving weight from the existing swing keel of your boat.

    What if you were banging along at 15 knots and the lightened keel hits a fixed object below the surface? The keel will fold-up to absorb the contact, as designed, and the reduction in righting moment will be considerable. At the same time, the boat will slow noticeably with the contact. This slowing, combined with a lighter RM weight of the keel, which is in a fully retracted status, will reduce the fixed righting moment to a very small number.

    The slowed vessel will also not get as much lift from the DSS foil with the reduced speed and the whole boat will want to lay over on its side, as the wind will not change at all in this encounter. This is a position from which it will be difficult to recover until the keel drops to its fully deployed condition. A further delay in recovery will take place due to the lightened keel, even when it returns to full deployment. A whole complex series of actions will then be necessary to restore the boat to an upright condition. In the meantime, the crew and you will be scrambling to stay on the boat, as it will be over hard on its ear.

    These are not the kinds of sailing qualities that I would want while out sailing with friends on a warm Saturday afternoon. You'd likely not see them again for another sail, as the above process could be very disruptive for the casual, or non-sailors among your friends.

    Bill (Bistros) is much better at describing the physics of all these actions, as he is an engineer by trade. Let my description serve as the pragmatic, real world conditions that you could face should this type of scenario become a part of your summer sailing experience.

    If you do go forward with the alteration to the DSS foil system, I wish you all the best in your sailing experiences. I hope that something like the event described above, will not become a process which you will experience often, if at all.

    Best regards,
  3. Boston

    Boston Previous Member

    interesting thread guys
    Im surprised no one mentioned the KISS principle yet
    keep it simple stupid
  4. bistros

    bistros Previous Member

    Very interesting design - obviously done by an artist with more of an eye for beauty than a lowly industrial designer with utilitarian low cost in mind. More Anna Sundstrand than Magnus Jaderberg to put it in Swedish terms.

    Hard to admit it, but I fall more into the utilitarian industrial design side. I'm pretty function oriented, and physical beauty is an accident of functional requirements for me. I appreciate the functional swing keel, given your location.

    If I were fortunate enough to own your boat, I would find it very hard to take a reciprocating saw to it and lessen the beauty in the quest for 4-5 knots more speed. It is certainly possible to make a classic car much faster, but then it is no longer a classic car. I can't imagine adding lateral foils for performance doing anything but reducing the long term value of your boat. And you would probably not attract any more beautiful women to go out if the boat was 10% faster.

    If you want speed, you can buy & tinker with a much faster boat for far less than what you can sell your boat.

  5. Bertil
    Joined: Feb 2006
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    Location: Sweden

    Bertil Junior Member

    To Chris:
    If I get aground or pump up the keel it doesn't affect rigthing moment so much. When keel down it stands for 11% of the rigting moment, and with keel up for 6% of rigthing moment. The main part of righting moment comes from the wide hull 4,5m and the Bwl 2,85 when not heeled. When going fast using the wing it will decrease even more.
    To Bistros:
    -From my answer to Chris you can see the the designer hasn't only been thinking on designbeauty.
    -I willnot destroy the looks of the boat mounting the wing, as when it is deployed only the outer end of the wing will be seen from close distance in plane with the hull. I will paint it yellow as the boat.
    -Inside you will not see the wing as it is with its "garage" under the floor. So
    I do not think it will decrease the resale value.
    -I think the hull in GRP is a bit heavy for sailperformance as a multihull on all wind directions. But a hull of coalfiber would be 1000-1500kg lighter, then I think there will be a match. Think about that the boat with wing beeing ligther the faster it sails. The multi will have the same weight whatever the speed.
    -Perhaps there will be nessasary with hydraulic to move the wing. (I have that onboard for the keel). But perhaps it will slide over by its weight when you tack. In both cases I will have control and I do not know how to put on the hydraulics or ropes as the garage is always filled with water. Ideas how to do it ???
  6. Doug Lord

    Doug Lord Guest

    Why don't you make a deal with Hugh Welborn and take advantage of all their experience?
  7. bistros

    bistros Previous Member

    I've done a little thinking about this. I envision a small stuffing box in the middle of the top surface of the "garage", making a shaft access into the boat hull. The drive shaft I see having a small toothed gear on it inside the garage, fitting down into a geared slot lengthwise in the top of the movable foil. Turning the shaft one way moves the foil to port, reversing the shaft moves the foil to starboard. This could also simplify installation/removal and calibration if the gear could pull up into a recess in the garage top.

    I like gear drives because there is no unpredictable motion, no driveline losses and they can be very positive and the gear ratio is easy to adjust for both speed and strength. You could drive the shaft easily via a hydraulic pump, or via a manual crank handle if the hydraulics fail.

    I hope my description is adequate to create a picture in your mind!

  8. Henning P
    Joined: Dec 2008
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    Location: Sweden

    Henning P New Member

    Hi Guys,

    Now we start to discuss serious matters, I´ve got a boat similar to Bertils.
    Still under construction, Engine and steering ready, boat get 9 knots with 39 hp diesel. 5200 kg displacement It´s an easy driven hull. Rigging is the job right now.
    Carbon rig and Gary Hoyt jib boom is waiting to be installed

    My experience with folding keel is that I´ve been sailing Guy Christer Lönngren boats since 1986 all with this feature. Hit ground couple of times each season. No damage to boat structure or dramtic action on board.
    Only minor deformation of lead.

    You can visit www.guydesigngroup.fi

    The reason is that the hydraulic cylinder got an overflow valve and act as a shock absorber. I´ve never been able to get the keel to go all the way up before the boat stops or passes obstacle.

    When stop, sails down, start engine and reverse from where you came,
    nothing dramatic, but a bit embarrassing.

    The benefits are low draft when needed, shallow water in secluded bays, and high AR when sailing.

    So I´m not unfamiliar to technical stuff onboard, including everything needed for comfort living.

    What we need is qualified assistance for profile of wing and working mechanics for deploying and retraction.

    This was what I was expecting from this forum.
  9. bistros

    bistros Previous Member

    Mr. Lord does make a good point here.

    As I have stated before in this thread, I'm certain the DSS folks have encountered and dealt with many of the issues raised here. It would cost you nothing to contact them and inquire about costs, and also to obtain references of people who have had the DSS technology in use. Talking to existing paying customers is going to provide better feedback that you are going to get here from people (like me) theorizing. Paul B.'s comments regarding head to head performance of DSS-modified one design boats versus unmodified hit the target perfectly.

    I do believe that the DSS website and subsequent marketing articles may not be frankly discussing all the negative issues with the technology.

    I'm concerned about the loads on the horizontal foil - these loads may be very high, and also may be cyclical with out of cycle spikes in load and unload. It would be interesting to see data from load cells over time. Basic boat design acknowledges the design strength necessary for keels - this technology may require similar strength and structural engineering - which may be difficult to do adequately on a refit of an existing hull.

    The DSS site indicates their "fail-safe" strategy is to engineer the foil to break before the "garage" or horizontal daggerboard trunk is damaged. A fully powered-up boat, with reduced effective displacement (due to DSS foil lift) may react violently to a foil failure - and the missing righting moment from the DSS foil may allow a complete knock down and swamping.

    Welborn and company are the first place to start asking questions. If you get answers, please post them here!

    Given the basic configuration of the concept, it certainly may be possible to test function using a deck mounted lateral foil as an experiment. This is probably how Welborn did his first experiments - trying a leeward foil without damaging the boat permanently. If a horizontal foil is going to provide benefit you would see results immediately. You could also quantify loads with load cells measuring the deck mounting points.

    You could do a $4000 experiment that would give you a good idea about what to expect without damaging your boat unnecessarily.

  10. Boston

    Boston Previous Member

  11. Bertil
    Joined: Feb 2006
    Posts: 33
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    Location: Sweden

    Bertil Junior Member

    I have got in touch with the inventor, and he will help us. When things begins to happen I will report on this forum how it developes. Thank you all for your interest!
  12. Boston

    Boston Previous Member

    keep us posted please
    that thing was pretty cool

    did anyone do any time trials with identical boats
    one with and one without
  13. Doug Lord

    Doug Lord Guest

    Bertil, I'm very glad to hear that! Best of luck!
  14. Bertil
    Joined: Feb 2006
    Posts: 33
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    Location: Sweden

    Bertil Junior Member

    Some things has happened with the so called lee-wing:
    -A mailing between me and the inventor have been going on since I last wrote here. We also met at the Mets in Amsterdam last year where the inventor Hugh Welbourn showed a prototype.
    -Hugh have tried it on a 27-footer with a leewing on one side. He have also tried ii on a 30-footer "Drinks Trolley" (see the net), and last spring a retrofit on a 38-footer.
    -The results is closedhauled an increase in speed of app 5%, and when reaching 30-40%.
    -The boat gets more stable in waves and feels as appr 30% bigger, and heeling 5-6% less. So it is very nice for cruising too.
    -On the 38-footer the wing were mounted too near the bow of structural reasons and a new problem arised. When closehauled OK as expected, but when reeching the wing didn't work. It was disturbed by the bowwaves and did not work.
    -My question to this forum is now:
    Where to place the wing to avoid this?

  15. Perm Stress
    Joined: Sep 2009
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    Location: Lithuania

    Perm Stress Senior Member

    Why not to ask Hugh Welbourn? He is in the best position imaginable to answer this question.
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