Curved Lifting Foils on Cruising Cats??

Discussion in 'Multihulls' started by Doug Lord, Sep 4, 2011.

  1. patzefran
    Joined: Feb 2011
    Posts: 253
    Likes: 26, Points: 28, Legacy Rep: 10
    Location: france

    patzefran patzefran

    IMHO the only gain will be the boat looks faster (only looks !) and cost more
  2. Doug Lord
    Joined: May 2009
    Posts: 16,670
    Likes: 337, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Just for comparison, on a racing tri like Gitana or Banque Pop weighing about 15.5 tons, the maximum total lift and/or downforce on the mainfoil is around 2.5-3 tons.
  3. Angélique
    Joined: Feb 2009
    Posts: 3,003
    Likes: 328, Points: 83, Legacy Rep: 1632
    Location: Belgium ⇄ The Netherlands

    Angélique aka Angel (only by name)

    Their higher speed capacities give them of course also higher lifting forces, I would be surprised if it was otherwise.
  4. OzFred
    Joined: Nov 2015
    Posts: 509
    Likes: 56, Points: 28, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    Given the curve of the board, if the lift is resolved into vertical and horizontal components, it seems to me that about 75% of the lift is horizontal (pure guess). So a C board is pretty inefficient if your goal is to reduce drag by lifting the hull to reduce wetted surface. I think their main benefit is to prevent the lee bow from burying (effectively increasing RM) so the boat can be pressed harder, or just be better behaved if sailed more conservatively.

    It would be interesting to measure the effect vs a small canard foil mounted closer to the bow—but that might raise questions as to why it's needed (when C boards are somehow excused from that discussion).

    But like others, I suspect that the curve in the Catana boards is more for reducing the intrusion of the boards into interior space, a happy payback is a bit of lift, modern looks and ability to make rapturous marketing claims. It's undoubtably more expensive, but probably insignificant in the cost of a 20m luxury cruising cat. Value for money? You'd have to ask the owners who can feel smugly superior to owners of straight–boarded cats without ever putting it to the test. :)

  5. Angélique
    Joined: Feb 2009
    Posts: 3,003
    Likes: 328, Points: 83, Legacy Rep: 1632
    Location: Belgium ⇄ The Netherlands

    Angélique aka Angel (only by name)

    That's in accordance to what Catana claims... (the link needs for me a few seconds to open up at the quoted piece)

    ‘‘ . . . . curved foil-type daggerboards to help avoid the risk of "tripping up" . . . . ’’
    According to the vids and pic in post #129 in the other thread they sail a lot with both boards up, a simple test for speed gain would be to drop them, and ‘‘ . . . to optimise the pointing angle . . . ’’ from the first above link would also work better with the lee board down when they're not straight down wind sailing.
    Last edited: Feb 28, 2019
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.