Combined planing and foiling

Discussion in 'Hydrodynamics and Aerodynamics' started by alan craig, Nov 5, 2023.

  1. alan craig
    Joined: Jul 2012
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    Location: s.e. england

    alan craig Senior Member

    I've made a model airboat which is designed to lift the bow from the water on a foil at high speed, and plane on what remains of the flat bottom hull aft. The model is made from an old boogie board and the transom area has been filled to give a sharp bottom edge to the transom. The foil is just a suitably bent aluminium strip with camber. There is no control of the foil so actually it planes at the water surface. It works! but I can't see any significant difference in speed between with and without foil.

    Does anyone know of a real boat using this foiling (but really planing) forward and planing aft?
    Could it increase the efficiency of a full size boat?
    IMG_5265.JPG
     
  2. Robert Biegler
    Joined: Jun 2017
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    Location: Trondheim

    Robert Biegler Senior Member

    Seems like a stepped hull, but probably your foil has less drag at low speed than a step.
     
  3. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    Yes, I have ridden in one.
    It was made in Russia many years ago.
    It was great in 1' chop.
    Beyond that the waves would contact the raised hull at speed
    causing it to come crashing down
    creating huge drag and yaw to that side.
    Eventually, a wave made its way through the front window landing on my lap.
    The trip was aborted.
     
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  4. BMcF
    Joined: Mar 2007
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    Location: Maryland

    BMcF Senior Member

    I'm aware of at least two "tail dragger" foil-assisted passenger craft. One fairly large one built with titanium forward foil and with transom intercepters at the stern; that entered ferry service for at least some period of time, in the Baltic if I recall correctly. Have not heard of it in a long time. The other was a craft built by Westport (WA) that was originally configured to be a fully flying hydrofoil but later modified to be a forward foil tail dragger.....I know the craft was tested to some extent in Hawaii but I don't think it ever entered service.
     
  5. baeckmo
    Joined: Jun 2009
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    Location: Sweden

    baeckmo Hydrodynamics

    A forward foil (in line with the hull) creates a wave that the hull tail has to plane on. Since the wave-length depends on speed, the combo at best will have a very narrow "positive" operational window. The situation is different if the forward foil is mounted in the tunnel of a catamaran; there is still an influence on hull planing, but not as critical. But, as with most "engineering hybrids", the benefits seldom outweigh the drawbacks.
     
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  6. alan craig
    Joined: Jul 2012
    Posts: 381
    Likes: 131, Points: 53, Legacy Rep: 14
    Location: s.e. england

    alan craig Senior Member

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