Foiling Windsurfers

Discussion in 'Sailboats' started by Doug Lord, Feb 10, 2016.

  1. Doug Lord
    Joined: May 2009
    Posts: 13,880
    Likes: 118, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

  2. Doug Lord
    Joined: May 2009
    Posts: 13,880
    Likes: 118, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

  3. OzFred
    Joined: Nov 2015
    Posts: 107
    Likes: 1, Points: 18, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

  4. waikikin
    Joined: Jan 2006
    Posts: 2,212
    Likes: 86, Points: 58, Legacy Rep: 871
    Location: Australia

    waikikin Senior Member

    Well that would be going to far, easy to look up yourself.

    What's cool here is demonstrating the 30 year difference in control including sail although the first is really harken cool;)

    Jeff.
     
  5. OzFred
    Joined: Nov 2015
    Posts: 107
    Likes: 1, Points: 18, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    The point is that simply posting videos from YouTube is a bit pointless.

    I expect that most of the people who visit here know that hydrofoiling boats have been around for over 100 years, however recent improvements in the cost and accessibility of high strength composites means they can be reasonably cheaply attached to all sorts of marine craft. That, combined with cheap, high resolution video cameras and a forum like YouTube, means there are now also thousands of reasonably slick, high–quality videos to watch. But after the first few they are all very much the same.

    In regard to the posted video, the interesting facet for me is that sailboard design has changed far more than foil design. Even comparing foiling kiteboards to 30 year old stunt water ski foilers shows remarkable similarity, the notable difference is the kite, not the foil.

    The biggest recent advance in sailing hydrofoils has been the inward–facing J, L, Z, whatever boards developed for catamarans that have been reversed to outward facing for monohulls. But even their application is limited to high–performance craft, so great to look at and fun to sail but irrelevant to the vast majority of boat owners and passengers.

    If the Windrider Rave V ever gets its marine version of a sonic tube working, maybe that will be another step forward. But it's not looking good at the moment.
     
  6. Doug Lord
    Joined: May 2009
    Posts: 13,880
    Likes: 118, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

    Foils

    ===============
    You're absolutely right about these foils being the "biggest recent advance in sailing hydrofoils" but not J,L or Z: these foils are UptiP("uptip") foils according to the people that invented them:

    Link to Part 1 and Part 2: http://www.cupinfo.com/en/featuresindex.php

    Quote from the article,Part 1, Pete Melvin:

    When we were working on the rule, we knew you wanted to get as much lift as possible when you were going fast downwind,” Melvin says. "For instance, in the 2010 America’s Cup, sailed on giant multihulls, the maximum amount of lift we thought we could get was about 50% of the weight of the boat. At that time, we were still relying on the hull to provide pitch control, so what’s come out of this is the boats all now have elevators (the horizontal foils on the rudders).

    At Team New Zealand, we developed a new type of foil that allows you to keep your height above the water more or less steady. No one had been able to do that before, at least not on a course-racing boat that was not going downwind. We developed that mostly on our SL33 test boats -- they came with the stock constant curvature “C” foils and with those kinds of foils, you can generate 50% boat weight lift before they get unstable. But we noticed that when we could get one boat up fully foiling for a few seconds it would really accelerate away from the other boat – and that got the wheels turning. How, with such a huge potential benefit, can we achieve stable flight downwind? So our design team came up with the “up-tip” type of boards. We refined those on the 33s and our 72 is designed to do that and fortunately it worked right of the box.”
    [/QUOTE]
     
  7. Doug Lord
    Joined: May 2009
    Posts: 13,880
    Likes: 118, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

    Foils

    ======== ===========
    Not reversed at all-the physics of the way the IMOCA foils operate is nearly identical to the way an UptiP foil operates with respect to leeway. But entirely different with respect to lift: the uptip foils are unique because of their ability to control the flight altitude of the boat they are attached to with leeway coupling. Since the IMOCA boats are not foilers(they don't fly above the water) the altitude is irrelevant but the foil assist lift -similar to DSS foils- generates substantial additional righting moment as well as reducing the displacement of the boat.
    There is absolutely no reason why these foils need be limited to "high performance" boats-"foil assist" ,particularly retractable versions of DSS, can be used on cruising boats as well as high performance boats.
     

    Attached Files:

  8. OzFred
    Joined: Nov 2015
    Posts: 107
    Likes: 1, Points: 18, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    Reversed in the sense that they protrude outward, away from the hull, not inward.

    Except that hydrofoils are expensive, more complex to operate than a fixed keel (or even ballasted centerboard), encroach into interior space, are a maintenance headache, especially if the boat is left in the water for more than a few days (most cruising boats spend at least weeks at a time in the water and usually 12 months or so), and only offer benefits on a small range of sailing angles.

    Most cruising boats spend at least half their time under power, either fully or sail–assisted, because conditions are unfavourable. The conditions under which they can make any use of hydrofoils might occur 10% of their transit time, which is a tiny percentage of the time the boat spends on the water.

    So while retractable foils can be used on cruising boats, the incentives to do so are hugely outweighed by the deterrents.

    But anyway, back to sailboards…
     
  9. Doug Lord
    Joined: May 2009
    Posts: 13,880
    Likes: 118, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

    DSS foils don't encroach into interior space-they fit under the cabin sole and take up zero room in living accommodations. Maintenance is not a problem since the board is easily accessible.
     
  10. Doug Lord
    Joined: May 2009
    Posts: 13,880
    Likes: 118, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

  11. Doug Lord
    Joined: May 2009
    Posts: 13,880
    Likes: 118, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

  12. Doug Lord
    Joined: May 2009
    Posts: 13,880
    Likes: 118, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready


  13. Doug Lord
    Joined: May 2009
    Posts: 13,880
    Likes: 118, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

Loading...
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.