Design for DSS-Foil Assist for Keelboats

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

  1. Gary Baigent
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    Gary Baigent Senior Member

    But the point is, CT, if the bow is down 12 degrees, you're screwed anyway, foil or no foil. However, up until that fateful moment, maybe, those foils saved them a number of times from going down the mine.
    On Elf Aquitaine 111, the large chord wing masted, balestrom version, foils were placed high on the bows just below the gunwhales to counter nose diving but by the time the foils were buried, it was too late and they actually made the condition worse ... but if they had been placed just above the waterline, then, like the historic Kiwi 18, they may have done a good job. If you look at bow mounted foil designs like Keiper's Williwaw and the various canard tri foil versions, the bow mounts provided major lift without burying.
    And anyway, full marks to the 18 sailors for thinking beyond the confined box.
     
  2. fng
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    fng Junior Member

    Just thinking of boats that hobby horse around, go down the mine, require lots of helm movement to keep em going.... Doug have you had any word from Hugh if that mini transat with the dds is sailing yet ?
     
  3. CT 249
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    CT 249 Senior Member

    I assumed from the description that the pic in question was of Entrad, not a Kiwi boat.

    The foils didn't work that well, which is why they were abandoned. Lock had found out just the same thing in an A many years before.

    As you would be well aware, most high performance designers seem to have gone away from trying to develop extra lift in that sort of way to stop nosediving, as far as I know. Modern cats regularly go down quite deep but pop back up because the bows are designed to reduce drag when immersed rather than to increase lift in an attempt to avoid immersion. That seems to work a lot better than foils, although I've never been able to find out why there could not be foils that lift up, but are pivoted so that they cannot create downward force. Simple limited travel should do the trick, but there's obviously something I'm missing.

    I'm not sure what classes think inside boxes all that much more or less than other classes. It often just seems that there are different boxes. For example, many high performance designs could be said to have remained inside a box of thinking that revolved around expensive and complicated designs that provided good performance but could basically only exist in fairly small fleets, sailed almost entirely by expert men. Eighteens could perhaps be very much restricted by such a box.

    On the other hand, a class as pedestrian as the Snipe or Enterprise could be said to the product of brave and far reaching thinking outside other boxes; boxes that said that speed was critical, that a boat should be only built and sailed by expert men, that it should only appeal to richer sailors, etc, etc. Such boxes were probably often older and stronger than the boxes "escaped" by people who were following an old tradition of using technological advances to create lighter and faster high-performance boats for male experts from a few cities.

    Perhaps what we think are boxes are only the boxes we look out of?
     
  4. CT 249
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    CT 249 Senior Member

    Frank in person did not say that his own "experimentation resulted in a major leap forward in design - planing boats that were able to exceed windspeed around a race course". In person he was gave much more credit to the influence of others, as does Julian. Frank was a polite man, apart from anything else.

    As Frank put it, "you couldn't do (the huge advances in technology in recent years) if you're out on a limb by yourself, because you've got nothing to compare with and nothing to support you." Julian notes that the 49er used technology from 18s, 14s and Moths and he greatly respects people like Bieker, who have a different approach because they are coming from a different angle (e.g. designing boats that have to fit within class rules).

    However, IMHO it's fair to say that balanced view this may have been rather lost in High Performance Sailing and Frank's articles, which very much concentrate on Bethwaite boats. To some extent this could be seen as perfectly fair - he was a businessman and promoting Bethwaite products was obviously an interest of his and if he could do it good luck to him in many ways - but there's no doubt that other very reasonable people with vast knowledge of skiff design and many winning boats to their credit see this as a slight on the many other designers who created the modern boat. This is an outlook held by those who designed a very large proportion of current Aussie Skiffs. You've only got to know who some of the people from Sailing Anarchy are, for example, to see public proof of the depth of feeling.

    Therefore Paul's views are not uncommon.
     
  5. Timothy
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    Timothy Senior Member

    carbonicboats.blogspot.com/.../class-catamarans-look-at-state-of-art . Lots of stuff on lifting foils and pitch
     
  6. Doug Lord
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    Doug Lord Flight Ready

    Dss

    -----------------
    Lets keep in mind that the foils on that 18 were in no way whatsoever DSS.
    Picture below from page 258 of "High Performance Sailing " by Frank Bethwaite.
    click on image:
     

    Attached Files:

  7. Doug Lord
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    Doug Lord Flight Ready

    DSS Mini

    ==============
    None at all. But the guys may be holed up somewhere training with the boat and foil..
     
  8. Cheesy
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    Cheesy Senior Member

    I would say that in writing the book his designs were used as he had a pretty in depth understanding of how they got where they were and why, which is one of the reasons the book is so good.

    Yes it was Entrad I was referring to
     
  9. Cheesy
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    Cheesy Senior Member

    Well if the boat was heeled and not on a plain surely the leeward foil would have been generating some lift? sounds pretty similar to the DSS concept to me.....

    I did also hear about someone trying it on a 12 at some stage as well (actually a proper DSS type foil, not the bow foil on the 18)
     
  10. Doug Lord
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    Doug Lord Flight Ready

    dss

    =====================
    Not even close.......The 12 sounds interesting but your definition of a "proper
    DSS type foil" would also be interesting-I think.
     
  11. Silver Raven
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    Silver Raven Senior Member

    "A' class ???

    Gooday 'C-T' Which 'A' class of Lock's was that - can you remember & what year - Please. Thanks - ciao, james
     
  12. Doug Lord
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    Doug Lord Flight Ready

    Dss

    ===========
    As I know you're aware most small cats with "wave piercing" bows do use foils for lift-not the little low aspect foils used on the 18 Cheesy mentioned but curved lifting daggerboards that contribute to a reduction in pitchpoling on boats that use them. For monohulls, DSS or a version of curved lifting foils could also reduce and/or prevent pitchpoling among other improvements in boat performance.
     
  13. CT 249
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    CT 249 Senior Member

    The idea of reducing drag on small cat bows (rather than increasing lift) when immersed dates back to Nacra days, at least in available literature. It has been seen in many other boats, e.g Taipans (although not as dramatically as modern boats) Nacra 5.2s. 5.8s. 14 and 16sqs, F18s etc, which do not have curved foils.
     
  14. Doug Lord
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    Doug Lord Flight Ready

    ==============
    My point was that one of the benefits of curved lifting daggerboard foils is the reduction or elimination of pitchpole tendencies in modern cats that use them.
     

  15. Silver Raven
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    Silver Raven Senior Member

    Gooday bloke. Does that require moving the c/b's any further forward or changing them in any way - like bigger, deeper, changing the foil section, &/or changing the section of the foil from top to bottom.

    There's been some talk as to the diagonal-flipping/tripping of tri's apparently due to the lenght of the ama hulls. There is a lot to learn in this area. Sure hope I can get to know a lot more about all these important matters without getting into a slinging match with some of the more negative members.

    Thanks for all & any info - greatly appreciated. My very best to you - thanks for your great positive & uplifting attitude - IT IS fabulous. Ciao, james
     
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