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From: CarlZog (no email)
Date: Thu Nov 04 2004 - 09:21:21 EST
Regarding taffrail logs:
I've used a large Lionel log extensively on a schooner I worked on that did
educational voyages in the northeastern United States. I've also used
Walkers extensively offshore on a couple similar vessels (tops'l schooner,
brigantine; 120'-150' LOA; 9'-12' from the rail to waterline).
On the coastal schooner, our biggest concern with the log was having the
line to the rotator cut by inquisitive motorboats. Replacing these was
particularly expensive and difficult, so we took to using bright orange line
and hauling in the rotator in crowds.
Offshore, we paint the rotator black. Unpainted metal glittering in the sun
tends to turn the rotator into a fishing lure for sharks.
Motoring up on to Silver Bank near the Turks and Caicos once, we were
followed by a humpback whale who became quite enamored of our rotator,
nudging and poking at it, for reasons I never understood. I assumed the
vibration of the engines would have drowned out any hum from the rotator. We
hauled it back before she got carried away.
Anyway, a good taffrail log is usually very accurate, even in a following
sea. A couple factors that contribute to accuracy, in no particular order:
-- Speed. The ship has to be moving fast enough for the rotator to spin, not
slip through the water or sink. This is a product of the size of the
rotator, and to a lesser degree, the resistance of the line to twisting.
Most of the ones I've used are pretty good as long as you can maintain about
1.5 to 2 knots on average.
-- Length of line. As George indicated, the line needs to be long enough to
keep the rotator below the water. This is obviously a product of the height
of the gauge above the waterline. However, you also want to keep it far
enough away from the transom to minimize the turbulence from the ship's
wake.
-- Line material. The line's ability to transfer the twist from the rotator
to the gauge is critical. Avoid anything stretchy; use braided, not
three-strand.
-- Calibration. The rotator must be designed for the gauge it's attached to.
You would think was obvious, but as most of these are no longer produced,
insuring accurate calibration in shoppping for spare parts can be a
challenge. Additionally, any damage whatsoever to the fins on the rotator
will render it virtually useless.
-- Gauge condition. Keep the gears oiled and running smoothly.
On a separate note, I've also used a chip log quite a bit on a historical
replica vessel. This is a lot of fun, but a lot of work. It, too, can be
surprisingly accurate, but definitely takes some practice. The rise and fall
of the transom with the seas affected this far more than a taffrail log. We
found that how the line spools off the reel was the biggest factor in
determining how accurate we could get. The line needs to remain taut, but
not so much so that the chip is dragging through the water.
Making sure the peg popped when you wanted to collapse the chip for
retrieval -- but not sooner -- was also important not only to our accuracy,
but to crew morale. At six knots, having to haul back the chip if the peg
hadn't popped was a serious workout!
Carl
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