|
|
|
|
|||||
|
||||||
Subject: Taffrail log and an alternative
From: Arthur Pearson (arthurpearson@XXX.XXX)
Date: Mon Jun 17 2002 - 21:18:46 EDT
Trevor,
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?
Regards,
Arthur
-----Original Message-----
From: Navigation Mailing List
[mailto:NAVIGATION-L@XXX.XXX
Kenchington
Sent: Friday, June 14, 2002 3:58 PM
To: NAVIGATION-L@XXX.XXX
Subject: Re: sextant use
Ed Falk wrote:
> Maybe we should buy up all those sextants before the home decorators
get
> them.
>
> Does Southwest Instrument Company have any kind of web site? I
couldn't
> 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@XXX.XXX Gadus Associates, Office(902) 889-9250 R.R.#1, Musquodoboit Harbour, Fax (902) 889-9251 Nova Scotia B0J 2L0, CANADA Home (902) 889-3555Science Serving the Fisheries http://home.istar.ca/~gadus
|