Foils and Foil-assist for Sailing Super Yachts

Discussion in 'Sailboats' started by Doug Lord, May 17, 2019.

  1. Doug Lord
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    Doug Lord Flight Ready

    Thanks to David for this:
     
  2. Doug Lord
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    Doug Lord Flight Ready

    Chistera.jpg Figaro 3 with Chistera foil.jpg
    I read this paper and was curious where the term "Chistera" came from relative to the foil used on the Figaro 3. Turns out a Chistera is a wicker scoop used by a jai alai player!
     
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  3. OzFred
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    OzFred Senior Member

    Some more revealing quotes:

    4.5 DISCUSSION
    The towing tank testing of the three main options for foil-assisted monohulls has been conducted for a range of upwind and downwind conditions.

    Overall, building on the experiments undertaken and hydrodynamic data gathered, it appears that, for foil-assisted monohulls, no resistance advantage over a design without foils could be achieved, thus demonstrating their inefficiency under the present test conditions and inherent limitations, namely the pure hydrodynamic efficiency of foil-assisted monohulls.

    5.3 RESISTANCE
    The results proved very consistent with the original hydrodynamic efficiency experiment in that the lowest resistance is always achieved without foils. Indeed, despite the vertical heave (only significant from Fn=0.5), the reduced displacement and wetted surface area are never sufficient to overcome the added resistance and induced drag of the foil. Notably, the configurations providing the most righting moment, namely the Dali-Moustache in both conditions and the DSS upwind, also have the most drag, as shown upwind in Figure 8 (a) and downwind in Figure 8 (b)

    The authors note that their research is not conclusive and more is required, but they couldn't find any overall advantage for the three configurations tested over a boat without foils. The biggest benefit was in heave attenuation, which in itself doesn't make boat faster. It may make it more comfortable, so easier to drive harder but not necessarily faster.
     
    Last edited: May 19, 2019
  4. CT 249
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    CT 249 Senior Member

    But given the enormous cost of the foils - reported at about one third of the cost of a Figaro - it would be vastly more effective to make the boat longer which would reduce pitch (the greatest contributor to seasickness) while also improving speed.
     
  5. philSweet
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    philSweet Senior Member

    Why the duplicate thread? there's a discussion already on the original.

    CT, no doubt there is a huge development cost still associated with foil systems. That should come down fairly quickly if a few more people prove themselves able to develop such systems, and deployment and seal components become standard kit. We need guidance on safety factors and impact loads both for the foil itself and for the crashbox and seal systems. We need heuristics for gust response and other perturbations. Something like AVL software for aircraft, but able to plot stability analyses on a wind polar. Once we can look at dynamic stability characteristics and performance characteristics side by side on a polar chart, these different configurations can be sized and located on the hulls much easier.

    The relative roles of active pitch adjustment and control vs elastic compliance is another item that needs sorted. This will be different for the different foil types.
     
  6. Doug Lord
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    Doug Lord Flight Ready

    =========================
    I thought that since there are several foil assist topics here including the Figaro 3 and Baltic 142 that this was a good place to also have the topic.
     
  7. philSweet
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    philSweet Senior Member

    Maybe edit the first post to explain the broader purpose.
     
  8. CT 249
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    CT 249 Senior Member

    But Phil, the Figaro III doesn't have that sort of complicated system and the foils are STILL extremely expensive. Those fairly simple foils are said to cost 1/3 of the entire price of the boat - lengthening the hull would probably create a much better improvement in speed and motion for less cost and more convenience.
     
  9. Doug Lord
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    Doug Lord Flight Ready

    On the false* assertion above that the foils "cost 1/3 the entire price of the boat", I wrote to Vincent Prevost about that-this is his answer:
    * post 4 & 8 this thread

    Hello doug,
    The set of 2 foils chistera is sold less than 15 000 euros
    We are far from 30% of the boat price
    Best
    Vincent

    Boat cost about 204,545 Euros / foils = 7.4% not 33%
     
  10. CT 249
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    CT 249 Senior Member

    Well, then, someone had better tell Beneteau's General Manager that he's wrong. "The deeply curved foils and the cases supporting them, according to Beneteau’s sailboat marketing director, Gianguido Girotti, will represent almost a third of the cost of the boat." https://www.sailmagazine.com/boats/foiling-monohull-design

    GG told another publication that the "full carbon foils.....are worth 32 to 33,000 Euros".
    Pulling G’s with Beneteau – Pt II https://www.sail-world.com/Australia/Pulling-Gs-with-Beneteau-%E2%80%93-Pt-II/-156849?source=google Yachting World earlier said E35,000 for a pair.

    Initial pricing for the F3 was E155,000 (Figaro 3 : les 50 premiers exemplaires livrés début 2019 http://sport24.lefigaro.fr/voile/la-solitaire/Fil-Info/figaro-3-les-50-premiers-exemplaires-livres-debut-2019-887314) so given THE CLEAR STATEMENT FROM GIROTTI THAT THEY COST 1/3 OF THE COST OF THE BOAT the difference must be the foil boxes which is not hard to believe.

    One important thing is that the Sail Magazine article from which I got the information about the foils costing about a third of the entire boat was posted here by one Doug Lord. So if Doug is going to complain that the information in that article is misleading then he can only blame one person for posting it - and that is Doug Lord.

    You'd have to be pretty weird to get upset for someone repeating information from an article that you yourself posted here. Obviously the point is that Doug posts articles that contain misleading information.
     
    Last edited: May 23, 2019
  11. Doug Lord
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    Doug Lord Flight Ready

    Two year old articles vs Vincent Lauriot Prevost two days ago? I thank Mr. Prevost for his answer to my question.
     

  12. CT 249
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    CT 249 Senior Member

    YOU posted that article twice this year! I cannot believe that someone would post an article and then claim the article THEY posted was misleading.

    It is equally bizarre for anyone to post a 2017 article in February and then imply that it is too old in May.
     
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