mechanical (not hydraulic) canting keel design

Discussion in 'Boat Design' started by KLFC, Jul 7, 2015.

  1. KLFC
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    KLFC New Member

  2. gonzo
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    gonzo Senior Member

    Have you seen the Herreshoff system that works with a lever?
  3. PAR
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    PAR Yacht Designer/Builder

    Plenty of mechanical actuation systems have been developed, nearly all a lot less draggy than that will be, unless of course the drawing are simply an armature that'll live within a faired appendage. If not, I can only image the vortices trailing off something like that underway.
  4. philSweet
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    philSweet Senior Member

    And the self locking feature is considered inherently unsafe. In case of failure, or without assist, the keel should go to center and lock, not stay where it is. Worm drives don't normally do that.
  5. SukiSolo
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    SukiSolo Senior Member

    My understanding is the same regarding Worm drives, in that they are inherently self jamming. It's why for example, car window motors use them, so they can stop at any position. So to self centre it would have to disengage swing to centre and re-engage, might be fun to engineer....;)
  6. KLFC
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    KLFC New Member

    i had a quick look at Herreshoff system, thanks.
    the triangulated keel fins are structurally many fold stronger than a single fin - consequent mass/weight reduction of fin(s) structure - would/should more than offset any negatives from 'vortices'
  7. daiquiri
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    daiquiri Engineering and Design

    Interesting idea, but you definitely have to refine it hydrodynamically.
    The current setup is a drag-generator.
  8. rwatson
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    rwatson Senior Member

    No. The eddies between the two fins alone will create major dramas. I have read a few threads where even catamaran hulls interfere badly. Add the gap between the half circle - and its a huge drag.

    oh PS - it also destroys the 'lift' that hydrodynamic keels provide when going into the wind.
    Last edited: Jul 8, 2015
  9. PAR
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    PAR Yacht Designer/Builder

    I toyed with some V shaped appendage configurations, the idea to hold all the ballast in a bulb at the bottom with splayed high aspect fins holding it. Wow, what a mess. Some improvement was seen with asymmetric foil sections, but wake convergence, vortice generation and merging, plus a host of other issues, negated any hope of this configuration. Do some flow studies and you'll quickly see the loses.

  10. alan white
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    alan white Senior Member

    Upside down A-frame rig. This looks like two ideas. One uses an inverted A-frame (V-frame?). The other is a worm gear mechanism.
    The worm gear is often used where high mechanical advantage is needed, where drive goes one way, or where a 90 degree turn is required. They can also hold enormous loads. The two gears have to be matched, unlike spur gears, which are totally interchangeable within same spec gears. Spur gears (especially straight-cut) are much more efficient, but don't lock at rest.
    I would think a spur gear setup would be ideal (where hydraulic rams aren't desired).
    It would be about the lowest friction way to go. A worm gear would have to unlock or a clutch would be needed. The clutch might be quite compact due to the high speed/low torque of the input crank.
    A spur gear setup wouldn't need a clutch but could use a brake. The same clutch could be used as a brake except it would be "normally un-engaged" as opposed to the "normally engaged" of the clutch.
    A safety device could actuate a release of a brake (spur gear) or engagement of the clutch.
    The simplest way to allow a controlled return to center is probably hydraulic since no other mechanism can be as easily controlled to allow infinite control of speed by simple adjustment of a tiny valve. Like some shock absorbers on a car.
    Now that you've got the ram, why not add a simple pump using a lever? This wouldn't be as fast as a spur gear by a fair margin but it is simple, long-lasting, and likely cheaper.
    Doubtless, all of these ideas are already out there.
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