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    Taffrail log and an alternative
    From: Arthur Pearson
    Date: 2002 Jun 17, 21:18 -0400

    Celestaire lists small taffrail-style log in their catalogue (and
    website at http://www.celestaire.com/catalog/products/3801.html).  It is
    battery powered with an LCD display and a wire to trail the impeller and
    the literature indicates it reads out both speed and distance run. I
    have not purchased one but I would if I were planning passages of more
    than half a day out of sight of land.
    For bay crossings in the fog of Maine and Nova Scotia, a simple 30 foot
    chip log allows one to measure speed often enough and accurately enough
    to keep an accurate DR for several hours. Simply tie a bit of wood
    (weighted on one edge to be traditional and to minimize wind drift) on a
    length of light line, drop the chip overboard and time the number of
    seconds it takes for 30 feet of line to run out.  Divide 18 by the
    number of seconds to get nautical miles per hour, so 6 seconds indicates
    3 knots. I measure speed and plot a DR every 15 minutes. Any inaccuracy
    in speed measurement is less important that whatever allowance one makes
    for current and lee way. This is all I have had on dozens of trips
    Downeast and back in Maine and combined with a good ear and a good nose
    you should be fine (keep the engine off so you can hear surf, gulls,
    barking dogs, etc.).
    I join Trevor in his enthusiasm for traditional navigation other than
    celestial.  While I still aspire to get my lunars to within 3 minutes of
    truth (still working on them thanks to encouragement found here), most
    of my sea time has been spent along the coast and I would love to swap
    insights on traditional piloting with list members.  Anyone doubled an
    angle off the bow recently?
    -----Original Message-----
    From: Navigation Mailing List
    Sent: Friday, June 14, 2002 3:58 PM
    Subject: Re: sextant use
    Ed Falk wrote:
    > Maybe we should buy up all those sextants before the home decorators
    > them.
    > Does Southwest Instrument Company have any kind of web site?  I
    > find one.
    No answer to offer on that but I did chance to find "Robert E. White
    Instruments Inc." of Boston at www.robertwhite.com  Besides selling
    assorted new navigational and meteorological instruments, they
    recondition and sell used sextants. That can't be good for the business
    of the few remaining manufacturers but it does keep some fine
    instruments in use.
    For those whose interest in non-electronic navigation extends beyond
    celestial, Robert White also offers taffrail logs (Walker Knotmaster)
    and his "Nantucket Sounder" -- a nice hand "lead", though moulded in
    bronze. The latter is calibrated in fathoms (of course!) but the
    leadline is marked only by overhand knots at fathom intervals. Are we so
    far from a time when every seaman knew from birth that seven fathoms was
    red wool bunting while eight was a "deep" with no mark on the line?
    Does anyone know of other sources of working taffrail logs (including
    the spare impellers and lines which are inevitably needed sooner or
    later)? Off this shore, navigating in fog can't always be avoided and
    I'd like to know my distance run without resorting to electronics.
    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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