Thursday, February 28, 2013

Logbook Procedures

Navigators and vessel owners usually have set ideas about logbooks and recordkeeping underway. They vary from the most formal (pondering the notion of the ship’s log as a legal document) on down to none at all (pondering… or rather, not pondering anything). A visit to Captains Nautical Supply store today found some two dozen logbook options for sale, varying from 2 x 3 inches in size to almost 2 x 3 feet in size. The preprinted forms included varied from blank lined pages to amazingly complex patterns of forms and tables to be filled in.

The choice inevitably has to be personal, but I offer here some guidelines to what has worked for me and then come back to the legal matters alluded to above. For an ocean voyage I typically have three logbooks. One is the ship’s log, or deck log, which is the normal logbook referred to above. Every vessel should have one of these for all voyages and day sails. This is best done with some structured layout in a bound book. We will come back to what goes in it, and when, and why. To this basic logbook, I like to add a weather logbook and a third bound book, which could be called a notebook or a logbook.

The weather log is for transcriptions of voice broadcasts or a place to paste printed forecasts or maps, and generally a place for notes about the weather. This can be just a blank notebook. Numbered pages are nice for cross reference. Make entries sequentially from the front, and record the date at the top corner of the page. Try to avoid setting up some coded system of starting a new section in the back. Dated pages in sequence are always best. It will grow to be one of your most important books. Even on a day sail or race, you will have a set of VHF weather reporting stations you care about. You can record these in the broadcast sequence and record the reports in columns to watch how things change throughout the day. Remember the Marine Weather Service Charts explain all weather resources in your area along with their schedules (see You can also make notes on your own observations related to weather that are too specific or personal for the ship’s log. It can also be the place you make a time schedule of when various reports and forecasts are available for quick reference so you don’t miss any. This is a deceptively challenging task, discussed in depth in the book Modern Marine Weather.

The third book is a navigation journal of sorts. A place to do all general reckoning related to the navigation of the vessel. In other words, do not use scrap paper. All computations go in this book, no matter how simple—if something ends up not making sense, the paper trail can be helpful. Also record your observations and insights along the way that improve your navigation. Navigation knowledge proceeds much faster with a written record. You may learn some trick about radar tuning, or how far you can hear a buoy gong in certain sea state, etc. When you do a piloting fix there are always pertinent notes that can be added to describe it. At the end of the voyage you can then go back over what you learned. Sometimes I find these books that are 20 years old and discover when I first learned something that I now take for granted—or relearn something I had forgotten about. Though I discovered the value of this extra logbook by experience, I have since learned that the US Navy uses the Navigation Workbook (OPNAV 3530) for exactly the same purposes, so this has proven value in prudent navigation.

This book need not be for navigation alone, it could be for other matters of seamanship you picked up on the voyage. I recorded once, for example, a fantastic knot that I learned from an experienced sailor, and to this day I have never seen that knot in any other book. Again, sequential entries from the front with dated pages are best.

If you sail on a race boat with a lot of crew, boldly mark your notebooks “DO NOT USE FOR SCRAP PAPER,” otherwise you will find pages torn from them at random.

The ship’s log, however, is the main point at hand. The bare minimum it should include is time, date, position, course, and speed, entered every 4 hours or so. A more appropriate and useful log would include more columns and be entered more often.

The design we use ( is two-up letter size pages with 30 numbered rows. Columns on the left hand page include Date, Time, Log reading, Tack, Course (compass), Speed (knotmeter), Lat / Lon, and then 3 columns without headings for your choice of data. The usual ones I use here are COG, SOG, and WCV (waypoint closing velocity), which may have different names depending on your GPS model. In some cases you might want to change this to VMG, which is progress relative to true wind direction. The thin column for tack (P or S or M for motor) would seem redundant with the wind and course data we have, but it is still often referred to. It is best to record actual compass course and knotmeter speed (instead of just COG and SOG) because these are the data you will need to check your previous DR if you end up without GPS.
On the right-hand side we number the rows again 1 to 30 and the columns are Apparent wind speed, Apparent wind angle, Barometer, and Comments. We also ask that the person filling in the log put their initials in the Comments column or beside it. If you have true wind instruments and are confident they are working properly, you could record true wind instead of apparent.

The comments could be weather or sea state notes—these are ones related to the navigation at hand, as opposed to general matters of weather and forecasts in the weather log—sails set, when you charged the batteries, if you sight or speak another vessel, fridge or freezer temperatures, etc. Sailing anywhere near the Gulf Stream or similar currents around the world, the sea water temperature would be another key factor to log. I have never recorded or found much use for air temperature outside of the Arctic, but the full picture would include the outside air temperature. Certainly if you are sailing in very high latitudes, the air temperature becomes crucial.

When to enter the log is easy. Make an entry anytime something changes. An average steered course change of 5° is a lot, and calls for an entry, as does a change of speed by a knot or so. Racing sailors tend to make an entry every hour, which is helped by the numbered rows. If not entering on the whole hour, record the time in the row with the nearest hour. This way the several watches can carry out distance made good contests per hour or per watch. When cruising it would be unlikely to enter every hour, but on any voyage the rule is at least every four hours, even if nothing changes, and if something does change make an entry. Keep in mind that if all your electronics fail, your latest logbook entry determines your navigation knowledge. In an emergency or near landfall you will be happy to have this be recent data.

You will also find that in doing weather analysis underway it is crucial to have a log entry at the synoptic times of 00, 06, 12, and 18 GMT, which are the times the weather maps are valid. Then you can compare your barometer and wind with the weather maps. You might set your watch alarm to remind you in local time when these entries should be made. Remember, too, the free service Starpath offers to provide you with live weather data at sea from ship reports. Send an otherwise blank email to with the word “help” in the subject line to learn about the service. With this you can get all the ship reports within 300 miles of your (or any) position over the past 6 hours. Do this an hour or so after synoptic times to check your barometer and weather maps. You can also read about this at

If you are on a route to a foreign port in a vessel of any size, or your vessel is over 100 T in local waters, then 46 USC §11301 ( explains the legal requirements for logbooks, which are indeed rather elaborate, though the regulations are addressed mostly to safety issues, along with the makeup and behavior of the crew. Specific types of vessels have specific logbook entry requirements, although navigation entries are not addressed. Logbook procedures for Sailing School Vessels, for example, are covered in CFR 46 §169.841. We learn from all these required procedures that we might want to include in our non-required logbooks a couple of pages to list:

• Departure and destination
• Documentation or registration number of the vessel
• Draft of the vessel
• Names and nationalities of all crew members. (If you are sailing into foreign waters you should also know if any has been convicted of a crime.)
• List of the safety drills and inspections you have carried out, station bills established, and a statement that all crew members have been informed of the safety procedures on board.

Furthermore, it is not really an option as we learn from 46 CFR §78.37-3, Part (b): “The master or person in charge of a vessel that is not required by 46 U.S.C. 11301 to have an official logbook, shall maintain, on board, an unofficial logbook or record in any form desired for the purposes of making entries therein as required by law or regulations in this subchapter. Such logs or records… must be kept available for review by a marine inspector for a period of 1 year after the date to which the records refer.”

I must admit that I have never sailed on an ocean passage in a yacht where these data were specifically included as part of the ship’s log, but the virtue of the addition is clear in the event there were an accident. It could also be helpful in some port operations in foreign waters. On the other hand, there have been many times I wished in retrospect that we had kept a list of the crew members we sailed with on specific voyages. These records can also be valuable to crew members who one day want to apply for a USCG deck license, as this book can then help document their sea time.

You might also want to start a logbook numbering sequence for your vessel, so that as you sail more there is an order to your sequence of logbooks. The USCG offers a free copy of their Merchant Marine Official Logbook for those who are required to carry one. It is called CG 706B. It contains much information and references, but it is not very useful for small-craft deck logs. The master or owner of a sailing vessel on international routes may want to request one and read the official requirements. If you are playing Nautical Pursuit and need this answer, this is the place you will find the phrase “the ship’s logbook is a legal document,” but admiralty attorneys will still remind us that this is an imprecise phrase. §

Sample Pages from the Starpath Sailor's Logbook

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