Hickman Sea Sled Information

Discussion in 'Boat Design' started by DogCavalry, Feb 12, 2021.

  1. BlueBell
    Joined: May 2017
    Posts: 1,781
    Likes: 501, Points: 113
    Location: Victoria BC Canada

    BlueBell "Whatever..."

    Like this:
    Lorne Campbell Design : Sea Sled Dive Tender http://www.lornecampbelldesign.com/boat-commercial-military-SeaSled.htm

    I vaguely remember seeing this build thread:
    https://www.community.boatbuildercentral.com/forum/viewtopic.php?t=15124

    "This is Jacques HS18 scaled down. A variant of the TX18."
    I like what he did with the bow box.
    If nothing else, scroll through the pictures.
     
    Last edited: Nov 19, 2021
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  2. baeckmo
    Joined: Jun 2009
    Posts: 1,299
    Likes: 268, Points: 83, Legacy Rep: 1165
    Location: Sweden

    baeckmo Hydrodynamics

    You're right about the "classical" sled, with its flat bottom aft; it won't work with jet(s) due to ventilation. We have used an inlet collar, protruding about 50 mm below the bottom on v-bottom jet boats to reduce the inhalation of soft saltwater ice, but it comes with a slight reduction of jet efficiency. I imagine that this trick could work reasonably well on a sled as well.

    We also have used a central pod for single jet in asymmetrical cats, again with an efficiency reduction. In those cases this reduction was more than compensated for by the total avoidance of propeller and drive train damage in commercial coastal water operation. This arrangement would certainly work in a negative deadrise hull.

    The reason for the efficiency loss is that normally, the jet inlet swallows a portion of the boundary layer, which is fluid that has been "brought up to boat speed", ie it has zero speed relative to the hull. With the collar, this "pre-energized" fluid cannot be used for propulsion, hence the loss. But, as always this loss has to be weighed in when considering the SOR.

    The non-tripping chines are too narrow for good inlet conditions, but twin jets far to the sides of a bottom with, say 12 to 15 degrees negative rise would be quite possible.
     
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  3. DogCavalry
    Joined: Sep 2019
    Posts: 1,752
    Likes: 907, Points: 113
    Location: Vancouver bc

    DogCavalry I aim to misbehave.

    Extremely informative @baeckmo , as always. Thank you.

    I thought as much re air ingestion, and the chine width, but
    guessing<knowing
     
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