138 NICHOLLS'S SEAMANSHIP AND NAUTICAL KNOWLEDGE
3. What length of log line would you pay out ?
The length of line will depend on the freeboard of the vessel and
her speed, more line being paid out when in ballast than when
loaded so that the rotator may be kept well submerged and clear of
eddy water in the wake. The usual length is 40 fathoms at 10 knots,
but for small vessels and slower speeds shorter lengths can be used.
The accuracy of a log may be tested by checking it against the
known distance steamed between two fixed points, or by trials on a
measured mile, making due allowance for the effect of tide, if ,any.
On measured mile trials the mean of the speeds, not of the times, is
used. If the log registers too low, lengthening the line usually increases
the log registration.
^. When a patent log line is hauled in, how do you get the turns out
before drying it and stowing it away?
By paying it out over one quarter as it is hauled in on the other.
When I haul it in from the rotator end, it comes up clear of turns. Where
a clear run of deck is available, by hooking the line on to a swivel and
running along the deck with it, it can be hauled in without any turns
getting in it.
5. What do you do with the part which you unship from the rail before
stowing it away?
Clean it well, both inside and outside. Work some kerosene through
it, and, when you have got it thoroughly clean, some olive oil will
keep it in good condition till you want to use it again. The rotator
should also be cleaned and oiled.
Electrical Ship Logs have been devised to give a continuous record
of the speed through the water and the total distance run by measuring,
either in pressure units or in units of rotation, the flow of the water
passing the ship.
The Chernikeefi Log is ..manufactured by the Electric Submerged
Log Company, London. It records the distance run through the water"
at any speed from practically zero up to 40 knots.
The apparatus consists of a distance recorder (2) fitted in the chart-
room, which registers every 20th part of a mile, the dial being calibrated
up to 10,000 miles. A speed table is fitted below the speed indicator
dial and an electric flash lamp below the table. If the time is taken by a
atop watch between the flashes, the speed can be read direct from the