Design for DSS-Foil Assist for Keelboats

Discussion in 'Sailboats' started by Doug Lord, Dec 6, 2011.

  1. CutOnce

    CutOnce Previous Member

    Sydney Harbour 18' skiffs. High Performance Sailing, Frank Bethwaite, page 407.

    Design evolutions took place in the Northbridge Senior (evolving to Tasar), HSP series and 18'skiffs, including Grand Prix and B-18s. High Performance Sailing Chapter 20, Hulls.

  2. Paul B

    Paul B Previous Member

    Frank was not a designer of 18s.

    NS14s don't sail around the course faster than the windspeed. Neither do Tasers.

    HSPs were experimental craft that were not racing in any class and did not sail faster than the windspeed on all points of sail. Maybe on a reach. Then again, so do 505s and FDs from the 1950s.

    Just because someone wrote something does not mean they were THE innovators. It just means they were THE self-promoters. I think you should give more credit to BenBob for the breakthrough into the modern 18s.

    Of course the I 14s and the 12s and the 16s also played a part in the development of planing dinghys. Some of this development occurred far from any influence from Frank B.

    If you believe everythig written in some books you would also believe the Bethwaites invented the Asso kites in 18s. Bucko might have a different opinion on that.
  3. Wuzzi

    Wuzzi Previous Member

    You asked CO for specific boats. Perhaps you have reference points for the observations you make, Paul? It seems to me that Frank's son, Julian, had more than a little to do with the B18 design. Are you telling us that he operated in a complete vacuum away from the work of his father in that regard?
  4. CutOnce

    CutOnce Previous Member

    Seems like you've got things a little backwards.

    Confidence comes from hundreds of documented race results over an extended period of time. Read up on Portsmouth Yardstick handicapping to understand how long it takes (seasons of reported results) to build confidence and reliably handicap sail boats. Confidence has absolutely nothing to do with who designs a boat and their reputation, nothing to do with test results that have no baseline datum reference, nothing to do with RC testing and whatever one reads on the Internet.

    Scientific evidence is different from anecdotal evidence. Using your personal trust in someone's reputation, their own reported results (without the raw data used to reach the conclusions), random Internet posts and third party reports from RC model testing falls into the "anecdotal" or "gut feeling" level of credibility.

    This isn't to say that a "gut feeling" isn't right - it is to say it does not meet criteria necessary for scientific peer review.

    There is not enough data present, nor enough verified results present to have any more than "gut feeling" confidence at this point. I'm not doubting the technology or it's assumptions - I'm doubting the volume and quality of the "proof". Paul B's response is worth considering and he has not indicated he disagrees with idea of DSS - only with some of the results to date.

    I think there is some merit in some conditions for DSS - or I would not be participating in this thread and following developments.

    Some people may be confident and perfectly happy to accept anecdotal evidence as enough. I'm surprised at this stage you are "amazed" that others have different (and higher) standards of proof - this is a recurring theme we've encountered before.

    Please note I have not posted that you are wrong, that anything you've written is false, mistaken or addressed you in any fashion that can be thought of as a personal attack - please respond in kind or not at all.

  5. Paul B

    Paul B Previous Member

    I'm not saying that at all. I will say he was not operating in a vaccum away from the other work that was being done in the class.

    I don't think Uffa Fox was much influenced by the work of Frank B when he was designing planing dinghies in the 1930s. I14s developed quite outside of the Sphere of Influence of FB all the way through the Proctors of the early 1960s in the UK to the Kirbys of the early 1970s in North America (pre-dating the Tasar).

    Similarly, I don't think BenBob was influenced by any of FBs work when he designed Taipan in 1958/9.

    All design work is a continuum. Nothing is developed in a vaccum. Some similar things are developed in parallel in different places without any influence from the other. Physics sort of demands that.

    For anyone to say their work in some obscure class was the basis for all that came after is really stretching it.
  6. CutOnce

    CutOnce Previous Member

    Agreed. The only boat I noted can make it around the track at better than windspeed is the 18. The others were to cite the design evolution process Frank went through multiple times, not to use as examples of "faster than wind" hulls. Sorry if I wasn't clear.

    But - the environment, methods and evolutionary "built, test, quantify" experimentation created by Frank Bethwaite was a significant contributor to Julian's design career. Frank's participation in Cherubs, Ants and various Laser designs can't be discounted or ignored.

    Ben Lexcen / Bob Miller's contributions aren't being discounted by me.

  7. Wuzzi

    Wuzzi Previous Member

    Not necessarily. It completely depends on the work having been done and the influence it generates throughout the class.
  8. Paul B

    Paul B Previous Member

    Surely you are not suggesting that The Big Fella was more influenced by some out-of-date NS14 than the boats that were winning in the 18s when he did his first design?

    Murray's designs dominated for what, about eight years? They pre-dated any Bethwaite 18s by almost a decade, and sailed pretty quickly upwind and down.

    So who was influenced by who?
  9. Paul B

    Paul B Previous Member

    No. You are drinking the kool aide. This is simply scientific method and was used by Uffa Fox and others long before FB ever thought about designing a boat.

    There are many Laser II sailors who would not ignore FB's involvement in the design of that thing. In fact, I'll bet quite a few would have loved to punch him in the face to repay him...
  10. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready


    Are tank test results anecdotal evidence? Are test reports by the inventor anecdotal evidence? Are the test results of RC models anecdotal evidence? Are extensive full size boat tests anecdotal evidence? No they are not yet they seem to be ignored. There seems to be a divide in what the naysayers are asking for in terms of "proof":
    1) Proof that a lifting foil generates lift at X distance from the CB thereby creating Righting Moment? That has been proved 100% scientificaly thru tank tests, model tests, full size boat tests.
    2) Proof that such a foil can result in the boat using it going faster than the same boat not using it? Proved scientifically in tank tests, model tests and full size boat tests.
    3) Proof that such a boat using a DSS foil is faster than other boats not using a DSS foil? The majority of results so far for the only two DSS boats designed from scratch to use DSS(and one 27' full size model) are very good to excellent in the one year + since these boats have begun racing.
    4) Proof that a DSS foil functions well in rough seas? Proved 100% in tank tests, model tests and exhaustive full scale boat tests.
    5) Proof that a DSS foil can be used on any boat? No, the scientific evidence shows that a boat not designed specifically for DSS from scratch
    is not likely to benefit from DSS.
    Most of the backup info for this is available in this thread-it is fact-not speculation.
  11. Paul B

    Paul B Previous Member

    Often times, yes. Call Britt Chance and ask him...

    What scale were these tests run at?

    How did they scale the hull and the foil sizes in these tests? If you understood tank testing you might wonder about that.

    Often times yes. What are these reports based on? Good science or bad science?


    Yes. Almost the definition of it.
  12. Wuzzi

    Wuzzi Previous Member

    Obviously, there is a seriously prejudiced opinion when it comes to all things Bethwaite. Tough to engage a conversation when one member chooses to front that position. Count me out of the idea exchange.
  13. Gary Baigent
    Joined: Jul 2005
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    Location: auckland nz

    Gary Baigent Senior Member

    Paul, it was all a development from old stuff dating way back to around the turn of the 19th/20th Century ... and you know the designs, Half and One Raters, Thames Raters, Napier Patikis, US scows and so on, all would have been capable of exceeding windspeed ... and then there was a gap until Uffa did his International 12 and International Canoe work (WW1 killed off huge numbers of young innovators). Frank Bethwaite was a Kiwi and he would have known about Jack Logan's early scow 18's, also the much earlier Patikis - knowledge and history passed on to generations, hence Julian carrying it forward. Ben Lexcen was looking all about him too. Also Bruce Farr did a breakthrough 18 design before Ian Murray arrived, same story. Not to mention John Spencer's Cherub and Javelin and Russel Bowler's innovations. There was this fast dinghy gas in the air in the Southern Antipodes, all sailor/designers watching one another.
    Back on topic - all the posters here KNOW (yeah, gut feelings) that there is much to learn and be impressed by DSS - and I'll be surprised if this speed and power development turns out to be a blind alley. I guess the slight negativity was also expressed when the first planing dinghies arrived. Give it time.
  14. Paul B

    Paul B Previous Member

    Agree 100%.

    I doubt Uffa was much influenced by NZ Patikis. I also doubt the boys at Johnson Boatworks were influenced by any downunder designs when they did the first inland lakes scows. That's what I meant earlier by similar designs being done in parallel, physics and all that.

    Julian would also have known about the evolutions from Farr's Travelodge through the Colour 7s. Do I think the Dribley design experiments were more influential on Julian's 18s than Murray's 18s? No I don't.

    Pre-dating FB's experiments.

    Farr's 18 predated any Bethwaite designs by 20 years, and it was pretty "modern" considering the materials they had to work with in those days.

    All predating FB.

    I think the pitch issue needs to be solved. The video of the first DSS27 proto in the waves looks ugly, and the reports of the DSS25 having similar issues sounds like a trend.

    I would fully believe the boat would be faster close reaching in breeze and flat water. It is not a common situation, although we do have it here in Long Beach, CA due to the breakwater.

    I don't think it would be quite as happy in SF Bay in a big ebb.

  15. Cheesy
    Joined: Aug 2008
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    Location: NZ

    Cheesy Senior Member

    Since we are on the topic of Franks book (well worth the read regardless of who invented what) there is a picture of an old high volume 18 in Auckland fair hauling down hill with some "mini" DSS foils on it......

    Actually Im guessing that they were there to try and keep the bow up but still....
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