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.
Keeping a log book: what makes an entry useful
A good log entry answers one simple question later on: where was the boat at that moment, and what were the conditions? To do that it has to be brief, clear and written at the time. Record what you read off or observe, not what you assume. An estimated position should be marked as such, for example as a dead reckoning position, so nobody later takes it for a fix.
Write in ink, not pencil, and never rub anything out. A mistake gets a single line through it so it stays legible, with the correct entry beside it. Whoever makes an entry initials it. This old habit from commercial shipping is what makes a log credible, because anyone can see that nothing has been tidied up afterwards.
Decide before you leave which time you are using: ship's time or UTC. Note it on the first page and there will be no confusion later when weather reports, radio messages and log entries are compared. On passages that cross time zones UTC is usually the simpler choice.
A log book template: the columns a page needs
Whether you buy a printed log or make your own, a usable page has a header and lines for the running entries beneath it. The header takes the date, boat name, skipper, crew, port of departure and destination, together with fuel, fresh water, log reading and engine hours at departure. At the end of the day add the readings on arrival and the distance covered.
A fixed order for the columns works best, so that everyone aboard knows at once where to look. A template with too many columns does not get filled in at sea, one with too few leaves out what matters. A wide remarks column is worth more than any extra measurement.
- Time, stating ship's time or UTC.
- Position in latitude and longitude, marked as a fix or as dead reckoning.
- Course and speed, plus the log reading.
- Wind direction and force, sea state, visibility and barometer.
- Sail plan or engine, with revs when motoring.
- Remarks: manoeuvres, encounters, defects, significant radio traffic.
- Initials of whoever made the entry.
Is a log book a legal requirement?
For privately used pleasure craft in Germany there is, on the generally held view, no general legal duty to keep a log. That can change if a boat is used commercially, sails under another flag or is used for training. Which rules apply to your boat depends on the flag state and how the boat is used, so check with the relevant authority or your national sailing association if you are unsure.
Whatever the law says, many others expect a log. Charter companies often require one in the contract, notices of race for offshore events frequently make it mandatory, and anyone who wants to prove sea miles for a higher qualification needs records that stand up. Insurance contracts can also ask for records, and what applies to yours is set out in the policy wording.
The more honest question is therefore not whether you have to, but whether you can afford not to. After a collision, a grounding or a dispute in harbour, a complete log is the only record that shows what happened beforehand. Without it, it is one memory against another.
The log on board: watch changes, harbour and anchorage
At a watch change the log is the handover. The outgoing watch writes up position, course, weather and anything unusual, and the incoming watch reads it before taking over. That way they know whether the barometer is falling, whether there is a ship nearby or whether a reef is already in. One sentence too many is better than one too few.
The log does not stop in harbour or at anchor. When you anchor, note the spot, the depth, the length of chain let out and bearings on two or three fixed landmarks. If the bearings change during the night, you know the anchor is dragging. In harbour, record the berth, how the weather develops and any work done on the boat, such as an oil change or a replaced part.
In this way the log quietly becomes a maintenance record too. If you can look up when the impeller was changed or the rig last inspected, planning next season is easier, and when you sell you have a credible history of the boat in your hands.
Keeping an electronic log and backing it up
An electronic log has real advantages: it takes position and time straight from the GPS, is always legible and can be searched. Many apps and plotters also record a track. The track does not replace the entries, though, because it only shows where the boat went, not why and not in what conditions.
What matters is that a digital log does not depend on a single device. If the power fails or the tablet goes over the side, the whole passage is otherwise lost. Make regular backups that are kept off the boat, and have a plain sheet of paper ready so entries can carry on during an outage.
When choosing an app, check that entries receive a fixed timestamp and cannot be changed later without trace. A log that can be rewritten at will loses exactly the quality that gives it its value.
Frequently asked questions
Do I have to keep a log on my own boat?
For privately used pleasure craft in Germany there is, on the generally held view, no general legal duty. Charter agreements, notices of race and other contracts may require one, and boats under another flag or in commercial use follow their own rules.
What should go into a boat's log book?
Time, position, course, speed, log reading, wind, sea state, visibility, barometer, sail plan or engine and anything out of the ordinary. The header holds the date, crew, departure, destination and tank levels.
Is there a good log book template?
Printed log books come with a ready made layout. Your own template works just as well if it has the usual columns and a wide remarks column. What matters is that the whole crew uses the same one.
Can I correct mistakes in the log?
Yes, but visibly. Strike the wrong entry through once so it stays readable, then write the correct one beside it and initial it. No rubbing out, no correction fluid, no torn out pages.
Is a GPS track enough as a log?
No. A track shows the route but not the weather, the sail plan, the decisions or the events on board. It is a useful addition, not a replacement.
How long should I keep an old log book?
There is no fixed rule for pleasure craft. Keep it at least as long as questions about a passage might still arise, and ideally for good, because it also records the history of the boat.
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.
