Dynamic stability

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

  1. Doug Lord

    Doug Lord Guest

    Using foils to stabilize a boat is a well proven technology. The best examples I can think of are the Rave, Hobie trifoiler and Raptor 16. On these boats the crew sits in the center regardless how strong the wind is blowing and on the Rave and Tri-foiler RM is limited only by the structure of the boat.
    The DSS system is a bit different but quite innovative featuring a sliding foil.
    You can bet that company has done its homework and they have found that the increased RM trumps the increased drag-just like it does on the Rave,Tri-foiler and Raptor.
    The DSS system allows a completely retractable foil which is a great advantage for light air. It seems like a well thought out system to me.
  2. Cheesy
    Joined: Aug 2008
    Posts: 315
    Likes: 12, Points: 0, Legacy Rep: 189
    Location: NZ

    Cheesy Senior Member

    Doug, doesnt 'innovative' usually mean that something is new? ie not done before
  3. Doug Lord

    Doug Lord Guest

    As best I can tell using a foil in the specific way DSS is using it is entirely new-at least I've never seen it before-have you?
  4. bistros

    bistros Previous Member

    Just took a good look through the Dynamic Stability Systems website. One first impression it looks scammy. Anyone advertising their intellectual property lawyers on every page isn't trying to prove a technology, they are trying to market an intellectual property. Having an yachting insurance firm, said lawyers and sailmakers as front line partners in a sailing technology company just doesn't ring true.

    I'd rather see an accredited school of Naval Architecture or Engineering as a partner.

    I agree that there may be some benefit to the concept - complete with a balance of negatives.

    One thing I have learned in 30 years of engineering is that there is no such thing as a free lunch. People who promote a concept as providing nothing but benefits with no liabilities are generally grifters hoping their mark's lack of education and experience allows them to get excited and "invest".

    I also look at people who value "intellectual property" as a primary balance sheet level business asset as suspect. Intellectual property is a twentieth century fantasy concept invented by lawyers to try to move ideas on to a balance sheet.

    Ideas are not valuable - execution of ideas is potentially valuable. Once the execution of an idea is tangible, the market will quickly establish a real value. Letters patent are a legal construct that attempt to protect a potentially executable concept for a limited time period, allowing people to invest with less fear of loss. Patents, at least are intended to cover execution of ideas - diagrams, plans and explanations are part of the patent process.

    The appearance of originality is a function of the obscurity of the source of inspiration. Most patents are granted because the source of the inspiration or prior art of execution is sufficiently obscure.
  5. Doug Lord

    Doug Lord Guest

    The inventor in this case is a well known Naval Architect and they are investing big dollars in an ongoing test program.
  6. Cheesy
    Joined: Aug 2008
    Posts: 315
    Likes: 12, Points: 0, Legacy Rep: 189
    Location: NZ

    Cheesy Senior Member

    There were pictures of a NZ boat that had a very similar looking system on another forum
  7. bistros

    bistros Previous Member

    A well known and respected Wall Street financier was just indicted for a 50 BILLION dollar Ponzi scheme. Well known and respected can be a fleeting quality. Non-commercial institutions like Universities and professional associations have more credibility with me (and savvy investors).

    I'm not doubting the potential upside of this development. I'm just saying that it is balanced by a combination of downside factors that must be acknowledged and understood before buying into the concept.

    In engineering, the simplest possible solution to a problem tends to be the most reliable. In this case, righting moment is the problem and the simple solution is a ballasted keel. As the last couple year's public canting keel failures demonstrate, complex systems fail more frequently.

    There is no doubt that things like canting keels, this "sliding horizontal lifting foil" technology and other answers to righting moment issues can provide dramatic benefit when working right. Systems like this that require engine power, microprocessor control and hydraulics are questionably outside the realm of sail boats - to me they are actually power boats that have sails. Beside the religious issue of power needed to safely tack & gybe, which boat would I rather take my family on a long offshore passage on?
  8. Doug Lord

    Doug Lord Guest

    Why would this system require engine power? Trying to put this simple, elegant "foil assist" stability enhancing system in the same category with a canting keel is just plain silly.
  9. bistros

    bistros Previous Member

    How else do you propose anyone get the sliding foil across the boat (as in the animation) on a boat larger than 20 feet? Magic moon rays?

    This is basically a canting keel less the bulb - where lift instead of weight is used. It still has to move side to side during tacks and gybes, and has to do so in a reliable and predictable fashion. It would be a serious mess if the foil didn't get across on a tack and it started to push the windward side up instead of pushing the leeward side up.

    Simple? Theoretically, but not in the real world. Elegant? Less so under inspection.

    Even of the foil was lightweight (under 200 pounds) the loads induced by lift while the boat is moving make it non-trivial to slide across - because the boat movement is causing lift to be generated.

    In addition to the mechanical challenges, now the cabin has to deal with a lateral daggerboard slot (which can't leak) and that makes designing accomodations interesting.

    Doug, none of these miraculous ideas come without drawbacks.
  10. Doug Lord

    Doug Lord Guest


    You know I think it is totally irresponsible to engage in a discussion where-with NO KNOWLEDGE of the system you associate its inventor -Hugh Welbourn with a 50 billion dollar ponzi scheme and then argue points proven by DSS and Welbourn!!!!! Simple and elegant in the real world-you need more information!
    Read this: http://www.harken.com/Interviews/DynamicStability.php
    From the Harken page:
    "Welbourn Design Group

    Headed by Hugh Welbourn, The Welbourn Design group has been on the leading edge of innovation and yacht design for 30 years.

    With its long history of involvement at the top end of yacht racing, the Welbourn Design office is recognized as one of the leading lights in foil development as well as performance optimization. "
  11. bistros

    bistros Previous Member

    Doug, faced with a simple, straightforward analysis of material presented on their web page you respond with a personal attack, and no mention of the issues I raised.

    Nothing is simple, and no gains are free. Welcome to the real world.
  12. Doug Lord

    Doug Lord Guest

  13. Chris Ostlind

    Chris Ostlind Previous Member

    Besides this fact... It's as funny as all get-out that monohull sailors still wanna be like multihullers with the inherent stability, weight and speed advantages of the multihull genre. They want it so bad that they are willing to add yet more complexity to their boats. This kind of addition further increases the chances that they will suffer a complexity related failure beyond any failure regime being sustained by the original non-foiled craft.

    While looking at the article shown in the link supplied by Doug, I did get a surprise boost to an argument I put forward some couple of years ago. There was a rather peppy engagement here about the merits of canting keels vs just leaving the BS off the boat and sailing it well... or, horror of horrors for the led-sledders, simply go out out and get a multihull if they want real speed. In the article above, the designer of the foil in question, Hugh Welbourn, made a comment when asked this question:

    "Do you feel this could replace the canting keel?

    HW: Yes. The distinct shortage of canting keel boats being built other than Open 60s and Volvo 70s is an indication of a market voting with its feet.

    The complications of cost, systems, weight overheads and above all the total loss scenario when canting keels fail have been seen to outweigh the benefits."

    Nicely enough, that's the very same argument I made way back during the argument with Doug regarding canting keels and, as you might imagine, he used every one of his nasty invective comments to attempt to deride my position. Now, right out of the mouth of a guy that Doug, himself, brings to the discussion table, comes the simply phrased statement that supports my position on canting keels.

    Douglas... it's time to man-up about your previous short-sighted exclamations in light of the realities being shared by your very own witness. You do regard this guy, Hugh Welbourn, as someone of professional standing, do you not?
  14. bistros

    bistros Previous Member

    Read it long before I posted my response. And YOU answered nothing.

    Ropes? You think pulling yet more ropes while tacking or gybing to move the horizontal board is practical? Not on any boat I've sailed on (and yes, Doug I sail on full size boats). Tacking and gybing is the busiest time on a sailboat, and adding ANOTHER manual system that is timing critical to the process isn't exactly helping.

    THINK FOR YOURSELF, rather than looking for Internet quotes from people with a vested interest in the project. Better yet, gybe a kite going downwind and now add a long travel rope pull that MUST be done in the middle of crossing the boat. On anything bigger than a dinghy, you have to have a person on a grinder and a tailer. THINK. Move another 20' of rope in 15 seconds, while dealing with spinnaker poles, spinnaker sheets, jib sheets and oh, yes, duck under the boom and vang.

    Hydraulic movement of the board, with automatic control is a real world practical solution. Once you've got to move the board, you have to consider how the controls attach to the board - think about another stuffing box, attachment points and how you are going to pump hydraulic fluid on demand. People choose hydraulics for canting keels because it was the best compromise solution for the problem. I'm sure no one wanted to have an engine running to keep the pumps working, but they conceded it was necessary. Why? THINK for yourself.

    The people that develop systems, and are selling the systems are consciously trying to minimize apparent liabilities and optimize benefits. It's called marketing, Doug. I do it. You do it. Everybody does it.

    I have not said this idea is without benefit. I have said the benefits come at a price. I'm sure the developers (if they were being candid) would agree, and also they could point out dozens of problems I haven't noticed, that they may have already addressed.

    Harken is selling bearings to deal with the vertical loads induced by the lifting plane. Is Harken unbiased? They seem to be getting "free" advertising on every page of the DSS site.

    Bearings? Last time I attended engineering school, bearings were a maintenance prone, wear prone, failure prone component in a system. Bearings are necessary when there are unwanted forces applied to a system. THINK. Stiction. Wear. Environmental challenges. Failure modes. Maintenance.

    Nothing is simple. When you THINK for yourself.

    I've never stated this technology may not offer a NET benefit - but I do acknowledge that you have to add the pluses and minuses to reach a result.

  15. Bertil
    Joined: Feb 2006
    Posts: 33
    Likes: 1, Points: 8, Legacy Rep: 25
    Location: Sweden

    Bertil Junior Member

    It is nice to see the dioscussion is in swing.
    Some comments to the multihull-man. There are some advantages with a monohull equipped with the leeway-wing to multihulls:
    -They cannot turn around so easy without giving the signs that it is to happen.
    -Smaller width giving easier handling and less space in harbor.
    -Bigger living space for given width.
    -Less wet area per kilos deplacement.
    -Cheaper to build.
    -Dampening/slower movements in sea-state.
    -Deplacement by less weight in keel/bulb narrowing/alike to the multihull.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.