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Noon speed when the clocks went back

Bu sayfanın Türkçesi

Noon to noon running west: the clocks went back, so the ship's day is longer than 24 hoursThe ship ran west from yesterday's noon position to today's and made good 336 nm (the log showed 344 nm, which is not used). Running west the clocks were put back 1 h, so the day from noon to noon was 24 + 1 = 25 h, drawn to scale against the calendar's 24 h. Noon speed = 336 ÷ 25 = 13.44 kn.NOON TO NOON · NORTH UPNnoon yesterdaynoon today336 nm made goodlog 344 nm: not usedrunning west: noon comes latercalendar day 24 hship's day, noon to noon 25 h06121824+ 1 h: clocks put back336 ÷ 25 = 13.44 knnot 336 ÷ 24 = 14.00 kn

The rule

  • Work out how long the ship's day really was: running west, noon comes later, so each hour the clocks go back is an hour added to the day.
  • Running east it is the other way: clocks put forward, the day is shorter.
  • Use the distance made good between the two noon positions, not the log: the noon report is about the ground.
  • Divide the distance made good by the real length of the day.

Formula

  • Length of the day = 24 h + clocks put back (− clocks put forward)
  • Noon speed = distance made good ÷ length of the day

Worked example

Distance made good between the two noon positions336 nm
Distance shown by the log over the same period344 nm
The day, before the clocks were altered24 h
Time the clocks were put back1 h
  1. The clocks went back 1 h, so the day was 24 + 1 = 25 h
  2. Distance made good = 336 nm (the log's 344 nm is not used)
  3. Noon speed = 336 ÷ 25 = 13.44 kn

Answer13.44 kn

Common mistake

Dividing by a plain 24 h because the calendar says one day.

She steamed for 25 h between those two noons; 14.00 kn credits her with speed she never made, in a report the charterer checks against the warranted speed.