the Assassin’s Holroyd foils

there is not much going on at the moment as all lakes are solidly frozen and I haven’t sailed any boats since Nov. 28th. With the winter as strong as it is only DN sailors like Fred have some fun.

In the meantime I thought I take the time and show you some more details about the Assassin. The foils have been designed by Nick Holroyd who is involved with the Emirates Team New Zealand. The rudder is very radical in design with the vertical being aft the horizontal. My first one broke but after some reinforcements on the joint there haven’t been any complaints. The main foils jont is very unique as it connects on a wider area and features two screws. In addition the Assassin foils are a lot longer than the BRs.

The wand mechanism is very simple and direct. An axle runs over the bow and the pushrod is lying inside a channel to the center board. Here are some pics to explain all the bs I just wrote ;-)

8 Responses to “the Assassin’s Holroyd foils”

  1. Darren says:

    Hey Felix,

    The upper wing bar tie downs go over fwd strut and down around opposite lower wingbar.
    Also try rolling tiller over, looks like one slot is wider than the other.

    ps, you never showed how skinny the Holroyd’s are!

    Cheers

  2. Gerold says:

    Hi Felix,
    here I have to disagree with you:
    > The main foils jont is very unique as it connects on a wider area and features two screws.
    Olivier Guard (Sabrosa) was/is using exactly this type of joint since before the worlds in Weymouth 2008.
    His foils are used for his own Moth design and also for the Katana.
    You can see it on his schematic video at around 00:27.
    http://vimeo.com/3366064

    Cheers

    • NW says:

      The acid test is the mach 2 “castrate the builder if it fails test” as seen here:
      http://www.mach2boats.com/images/stories/foil%20bedn%202.jpg

      if assassin or katana could/would post a similar picture it would clear up some doubts…

      • Darren says:

        NW

        Doesn’t really prove much that picture, we do regular tests the same. We have broken foils testing on the water that handle more than 90kg tip load in the above asymmetric testing. If you ventilate one side and round up inducing more AOA quickly, the loading is absolutely massive.

        We will be doing some destruction testing soon, we will get some video, but we are expecting well in excess of 100kg on one tip.

        • NW says:

          Hi Darren,
          thanks for the response!

          The BR/Mach2 “mortise and tenon design ” interface has (to me) some intuitive integrity because of the amount of material that needs to deform for a failure to occur when doing a cantilevered load test like the photo showed.

          The (so far as i can tell) “flat strip/tab” ( shallow mortise, shallow tenon?) design that the assassin and katana images have seem to me to lack that deformation volume. In my head I anticipate the “tabs” prone to buckling if they fail – but I really haven’t seen pictures of the intersection of the foil and vertical close up to really understand it…. So I’ll readily accept that all my instincts are probably and completely plain wrong.

          I believe you about the potential massive loads that have to be endured by any successful foil assembly. Consider the momentum of a hull and 80kg sailor at 25 knots… coming to an instantaneous stop.

          • Darren says:

            believe me there is a lot involved in getting the foot just right without adding too much drag, our foils are very very thin. But in the lower wind range no torpedo is unbelievably fast and worth the work.
            check out sam and andrew brown testing in no wind, they were sailing at about 3 knots until they pumped the boat onto foils. http://www.youtube.com/user/Assassinmoth

  3. Nico says:

    Hey guys,
    I am the owner of the Katana.
    Gerold is true saying that the idea of the same system with 2 screws to assemble the foils was dated back in early 2008 with reflections from Olivier Gouard designer of the foils for Katana and Sabrosa moths.

    What happened to me on the Katana is the loss of the main foil during the first Katana sail in only 8 knots of wind and the loss of the rudder foil in 25knots wind at UK Nationals 2009. So I had to face this major breakage with our system mainly because the screws were only 10mm inside the main foil and mounted with helical coil thread insert.
    To fix it, I had to glue with structural epoxy both main and rudder foils to the vertical parts. Now the foils are definitely fixed and it is really really strong !
    I think Olivier had not such problems on his Sabrosa with the same foil system.

    So I don’t know the load amount calculated with the Holroyd foils, but you should be very careful to the length of the screw going inside the vertical part to be sure the fixation is strong enough.
    Cheers
    Nico

  4. Niki says:

    I agree with Darren! The foils are very thin, so the drag should be very low. Becouse of this thin shape the thickness of the material looks much more than BR or Mach2 foils. So also weight is much bigger than the others. Also a reason of this is the lengh of Assassin Foils! They are quite a gib distance longer than the others. Flying high is a good advantage so hope this is also a Pus for Assassin foils! I do not have experience in strong wind conditions, but in light winds the foils are excellent!

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