Anti-Ventilation "Fences" on Foils


A few days ago I saw these fins on the website of Macquarie Speed Team (MST), this is way different than windsurfing foils!!! 

The quatro-fin setup
This is very well discussed in the Netherlands, main reason to reduce depth. It would be intresting to know why MST chose for 4 foils instead. I think it is a combination of strenght of materials & depth.

You can sea the bottomshape is monoconcave, like the Fanatic Falcon series. Maybe this is just the fastest bottomshape...

Anti-Ventilation fences
This one supried me the most. These thing can only be found in some old literature I got. The idea is smart, to reduce drag in real-world conditions. But for windsurfers??? When thinking about this it can be to hard to handle for us.

Quote from website:
The foils that control Macquarie Innovation are tiny by comparison to the large dimensions of the craft. They are asymmetric foils with a total span of approx 270mm.
The foils have been thoroughly tested using both computer simulation as well as flow tank testing at the Australian Maritime Engineering facility in Tasmania. With such high design speeds and relatively large loads carried by the foils (each of the four foils experiences the equivalent of an average adult male standing on the end of them), the possibility of experiencing cavitation is real. The section profile is deliberately aimed at delaying the onset of cavitation, thereby ensuring that control is maintained with minimum drag. Two anti-ventilation "fences" also appear on each foil to prevent the low suction pressures from dragging air from the surface down the side of the foil.

Erik Loots

Erik is windsurfer for 10+ years. In his daily life he is professional in construction dewatering, advisor, troubleshooter. Erik likes adventures, explore and to challenge himself. During his life he is trying to get the best out of it and have respect for the earth, nature and future generations. The modern world is about sharing, in this blog Erik shares his experiences, selfreflection and lessons learned.


  1. Two anti-ventilation "fences" also appear on each foil to prevent the low suction pressures from dragging air from the surface down the side of the foil.

    Looks like they have the same purpose as the Flappers on old FormulaBoards

  2. Chris, I am thinking the same! Formula is really wide, so if you want air the shortest way to the fin is via the back!

    On speedboards it is often the opposite, air does come to the fin from the side. I have noticed a decrease of efficiency.

    To prevent airflow to the foil I think it is the best to push your front foot down and ensure the board makes good contact with watersurface (less air)

  3. Didn't ever noticed taking "valse lucht/ false air " myself.
    Bud maybe its an idea to mount a hispeed camera in the board to film the fin and surrounding water to monitor the behaviour.
    It must be possible to make a see through hull like the F2SXWindow (2005) between the footstraps

    PS use another backgroud ,nearly can't read the comments

  4. Chris, I have been thinking about how to film this stuff.

    Just to get some real data. But it is a bit expensive to do. Because you will need:
    -high speed camera (at least 10 frames/sec)
    -camera aquapack
    -shockproof storage
    -adjustments on boards

    Also in the Netherlands almost all lakes have lots of organic material in water, making it hard to see. @ sea we have lots of sludge, the coastline is one big transport of fine sand/sludge. So I can't predict if the endresults will be good.

    If you know more, or a cheap way please share. Because when there is a big chance of getting valuable data for a reasonable price I would like to take that step.

    ps, about that backgrond problem can you describe what exactly is the problem? So I can try to solve it. In my webbrowser (firefox, google chrome, internet explorer) no problems.

    Thanks for your comments!



  5. Foor the camera ypu could use a Casio exilim (lookup on youtube) upto 300fps.
    the camera should be mounted near the fin so its possible to look through the sludge. I think the sludge will help making the waterflow better visible.

    The back ground is darkgreen and the letters are black. So make a lighter background or lighter letters
    (like the name and timestamp)

  6. Chris I hope this is better? Could I ask what webbrowser you are using?

  7. The windows crap 6

    About the video

  8. And the result of the formula fin
    (why he's recording audio?)

  9. Chris that's a very smart construction!! The camera is a headcam, I have seen it somewere for sale, not very expensive solution. Guess 120,- euro's total?

    Today looked very good for windsurfing on Amstelmeer, wished I had some time, can you believe it? And I can't afford right now to get sick.

    Have 2 do in the next 2 weeks:
    3 exams
    3 assignments
    2 presentations