Foil Assist Monohulls

Discussion in 'Sailboats' started by Doug Lord, Jun 14, 2018.

  1. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    This was posted in the "Route du Rhum-monohulls" thread and seems to be a great result for the viability of "foil assist". One needs to substitute the words "foil assist" for the word "foiler" below for a proper understanding of the meaning technically. The word "foiler" is used by some writers to describe boats that aren't actually foiling:

    Summing up the Azimut Challenge:
    VALIDATE THE TECHNICAL CHOICES
    More generally, the challenge Azimut was used to test and compare the different types of foils, to make a technical assessment of the innovations of the moment. Antoine Mermod: «I think we have definitely buried the debate between foilers and non foilers. The Challenge confirmed that foils are the answer. From now on, we enter a new debate between small foils and large foils. We have seen that PRB, with its large appendages, has interesting attitudes at all speeds. The choices made by Vincent Riou and his team seem very positive. "
     
  2. Doug Lord
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    Doug Lord Flight Ready

    Foil Assist---Charal: big air!
    pictures from catsailingnews by Yvan Zedda:

    CharalDefiAzimut2018byYvanZedda_52.jpg Charal Azimut.jpg CharalDefiAzimut2018byZedda_05.jpg CharalDefiAzimut2018byZedda_06.jpg CharalDefiAzimut2018byZedda_35.jpg
     
  3. Doug Lord
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    Doug Lord Flight Ready

  4. Dolfiman
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    Dolfiman Senior Member

    Video of the new Code 1 Foiler de Black Pepper yacht, Naval architect Marc Lombard :
     
    Doug Lord likes this.
  5. OzFred
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    OzFred Senior Member

    That's an ugly boat. No interior shots to show how much cabin space is lost to the centreboard and foil cases plus associated tackle. It's got twin hexagonal wheels though, very ergonomic. ;-)
     
  6. Doug Lord
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    Doug Lord Flight Ready

  7. Dolfiman
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    Dolfiman Senior Member

    Very interesting article, thanks.
    Within the evaluation of the foil effect that I did for the Figaro 3 case, I showed that there are 3 steps in the foil assistance :
    - in light winds, the lift/drag ratio (.i.e the finesse) of the foil is a lot lower than the one of the boat (where lift = buoyancy) : the extra RM created by the foil is very small and moreover does not compensate the extra drag of the foil.
    - in moderate winds, the lift/drag ratio of the foil is still lower than the one of the boat but in the same order of magnitude (let'say no less than 0,5 times the boat one), and then the extra RM created can give a bit more speed as long as that overcomes the extra drag of the foil. So one positive effect (more RM) which can counterbalance a negative one ( more drag).
    - in strong winds, the lift/drag ratio of the foil finally becomes higher than the one of the remaining buoyancy of the boat (especially when Froude is in the 0,4 to 0,7 range) and then we have a double positive effect : a large fraction of the boat weight is supported by a device (the foil) with less drag, and an important extra RM is created ( + a small but non negligeable effect : the heeling arm is slightly reduced as the drift resistance from the foil is at the water surface level) : then we can have a significant extra boat speed.
     

  8. Doug Lord
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    Doug Lord Flight Ready

    Vincent Lauriot-Prevost from the article:
    "Today, especially when talking about a Vendée Globe boat, you have to respect tonnage rules. They are binding compared to the foils because we are not allowed to add carrying planes on the rudders, which would allow to balance and to plan the boat completely. If we could rely on other buoyant plans, it would allow us to fly even more. But today, as the gauge forbids, we will try to adapt in this direction. Unless it evolves " (Bold by dl)
     
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