Foils (Bruce?) Question

Discussion in 'Multihulls' started by BobBill, Feb 1, 2012.

  1. Doug Lord
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    Doug Lord Flight Ready

    Cav, hydrofoil lift control on the Slatts is not automatic-it is manual. It doesn't uses a surface sensor(wand).
  2. cavalier mk2
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    cavalier mk2 Senior Member

    It has been a long time, they were introduced in the 80s, I might still have a brochure. The manual control part of the fun and was supposed to lift on one tack and hold down on the other which is the basic foil idea. The price is a lot lower now. I think they were around 10 grand new in then dollars.
  3. Auntie Frannies
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    Auntie Frannies Junior Member

    I know this thread is old, but didn't want to start a new just for this video clip. It's a promo video for the Slatts 22, better than a brochure.

  4. Marmoset
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    Marmoset Senior Member

    That is very cool, pretty simple as well.

  5. BobBill
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    BobBill Senior Member

    Much to like; much to go awry. I was going to buy one of these boats, used, and decided against the cockpit approach.
  6. PerthMini40man
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    PerthMini40man Senior Member

    In my experience, The wand-controlled foils are not easy to configure. I am working on a set for a one metre cat, and you can see the entertaining results in this video clip taken this weekend. I think part of the problem is that the foils do not always change angle of attack when the hulls are out of the water, even though the wand is encouraging them to do so. I need to move the pivot point further up the leg, to make sure that the water pressure will push the foil into negative attack. ie scrap them and start again....

    Half way through the video is a good run from my Mini40, which uses Hydroptere-style foils, no hold down.

    Attached Files:

  7. Auntie Frannies
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    Auntie Frannies Junior Member

  8. Jim Caldwell
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    Jim Caldwell Senior Member

    Longer lever arm on the wands will help or maybe too much friction ??? I would try the longer wands first much easier than rebuilding the foils.
  9. edvb
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    edvb Junior Member

  10. PeteCress
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    PeteCress Junior Member

    I know this is a really old thread, but I can't resist...

    I may have bought the boat you were going to buy - was it a yellow/white Raptor 16 from The Man Himself, John Slattbo?

    I have been fooling around with the one I bought for a couple months now and my observations so far are:
    • This is an "Interesting" boat to sail: .i.e. it demands your full attention.... Sailing it is a little bit like flying a helicopter in that, on ama tack, you need both feet (to steer) and both hands (one for the mainsheet and one to control the foil).
    • The boat is fragile: After capsize I attempted a deep-water remount by heaving myself up on the ama and then sliding across an aka to the main hull like I do on my Hobie Adventure Island..... Bad Idea because the racking induced by sinking the stern of the ama tore out the fiberglass tube that the aft aka was in.... "Fragile" is probably the wrong word.... "Rigid" seems better.... The Hobie system has the akas in over-sized tubes in the ama with plenty slop and held in by bungees instead of alu pins - resulting in a system that responds to racking by flexing/stretching instead of breaking.
    • This is a good light-air boat: 9 meters of sail and it goes in the slightest breath of air.... and the Paddle-Sailing aspect is what I was hoping for... a little exercise along with the sailing.
    • There is plenty to go wrong:
      • For instance I don't know what happens when one accidentally cocks the foil to 90 degrees at speed, but I am betting it involves a new foil.
      • Deploying/retracting the foil can be problematic if there is a trampoline out there because the lever can get hung up/tangled in the tramp.
      • There is a lot of line laying around in that itty-bitty cockpit and entanglement upon capsize is a definate consideration. .... I have taken to trailing some lines at some times - like the foil control line, the mainsail furling line, and the mainsail unfurling line.
    • You hit shallow water on ama tack with the dag deployed and you're going over - because the loss of speed causes instant loss of lift in the foil.

    If I were re-engineering this boat, four priorities would be:
    1. A less-rigid ama/aka interface: Something more like Hobie's implimentaion on their Adventure and Tandem Islands.
    2. A kick-up daggerboard: Also like Hobie's AI... so when you sail into a sand bar in murky water it just gets pushed up into the hull.
    3. An upside-down Bruce Foil: instead of a symmetrical foil which can be used to pull the ama down or lift it up depending on it's attack angle, I would make the foil one-sided so that all it does is generate downward lift to keep the ama from flying....This would allow a "Set it and forget it" option where the foil semi-locks into the right angle of attack to keep the ama down...."Semi-Lock" because there would need to be some provision for it's retracting if it hits something.
    4. Hinged akas: Again, like the Hobie AI. These would greatly decrease rigging time for the boat and also introduce some fault-tolerance via shear pins if/when one manages to sail the ama/akas into a bouy or channel marker or something...instead of breaking, the assembly just folds as the shear pin breaks.
    Edit 2018 05-22 1058: Made some changes in accordance with Doug Lord's observation that my idea of a "Bruce Foil" was incorrect.
    Last edited: May 22, 2018
  11. BlueBell
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    BlueBell Ahhhhh...

    The video is good.
    The pitch-pole at 3:10, classic!
  12. upchurchmr
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    upchurchmr Senior Member


    Can you post some pictures? To show what you are talking about?

    I don't know if this kind of foil setup is really called a Bruce Foil.

  13. PeteCress
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    PeteCress Junior Member

    I suspect you are correct on the naming.

    I came up with the term after reading a description somewhere.

    Here is an illustration of what is on the Raptor 16:

    Can anybody cite the correct term?

    I have .MOV showing it in action but YouTube does not seem to do .MOVs and this forum says it is too large to upliad.

  14. Doug Lord
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    Doug Lord Flight Ready

    I'd say that,technically, it's probably not a "Bruce Foil". It's a hydrofoil* capable of vertical lift and downforce due to a manually adjustable angle of incidence.

    * A "Bruce Foil" is a single foil that develops both vertical lift and lateral resistance.
    The Slatts 22 uses a T-foil which consists of two foils -one vertical, one horizontal. The angle of incidence of the horizontal portion of the T-foil is controlled manually-the AOI of the vertical foil which develops lateral resistance is automatic and not controlled manually.
    Last edited: May 21, 2018
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