Home / Seamanship / Navigation on board / Keeping the log book
The log book, and why it counts
The log book is the dullest job on board and the only one whose value appears afterwards. It is a chain of observations written before the event, and that is exactly what makes it stand up.
What belongs in it
Time, position, heading, speed, wind direction and force, barometric pressure, engine hours, and anything out of the ordinary: sail changes, reefs, encounters, defects on board, anchoring with bearings.
How often
Hourly on coastal passages, every four hours at the watch change offshore, and always in addition whenever something changes. An entry that only gets made in calm water is missing exactly when it is needed.
Paper or digital
Both count, as long as the series has no gaps and the time is fixed. Paper does not need power, digital is legible and can be backed up. If you keep it digitally, put a copy somewhere off the boat from time to time.
After a loss
Keep writing, do not backfill. What you add after the event is a report, not a log. The value of the record lies in the fact that it was not created in hindsight.
What this has to do with insurance
With us the log book is more than good practice: our blue water cover requires the digital NAMMERT log book once the boat moves more than 300 nautical miles from its reported location, and if a loss occurs away from that reported location the settlement may be reduced. Keeping it meets a contractual duty and at the same time produces the document that counts in a claim.
