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    Re: Propulsion power: was [Nav-L] Barrels
    From: Trevor Kenchington
    Date: 2005 Jan 19, 21:38 -0400

    Bill asked:
    > 1. Do you know the formula/ratio involving LAW, speed and depth when this
    > limiting factor/resistance comes into play?
    I can't find it. (Hope someone else can!) But it does act at a
    surprisingly great depth:  A 600 ft ship running at 25 knots experiences
    some extra drag from the seabed at 25 fathoms depth, for example. It is
    a problem for designers of measured miles, who need to find sufficient
    depth close enough to land.
    > 2.  Would a submarine making speed very close to the bottom be slowed down,
    > and or forced upward (perhaps bow up, stern down) because of the above
    > dynamic?
    Yes -- except that a submarine running fast, close to the bottom is all
    too likely to be slowed even further by hitting something solid.
    Something similar can slow ships in deep water if there is a shallow
    thermocline, though the mechanism of energy loss is rather different and
    so are the ways of escaping the extra drag.
    Trevor Kenchington
    Trevor J. Kenchington PhD                         Gadus@iStar.ca
    Gadus Associates,                                 Office(902) 889-9250
    R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
    Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555
                         Science Serving the Fisheries

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