The rotating three-watch system that splits the watches into five four hourly stints, with the 1600 to 2000 watch split into two dog watches, has been used by the Royal Navy since at least 1700 if not earlier, so it's the one that is perhaps best known.
A variation of this is the simple 'four hours on, eight hours off' system that dispenses with the slightly awkward dog watches. But its big difference to the rotating system is that it also fixes the watch-keeping pattern so that the crew members always keep the same watches. If you draw the middle watch on day one, it's the middle watch you'll do until you get to your destination.
Some people think this is a good thing, because the body adapts to the new sleeping pattern fairly quickly. You know that you'll always be able to sleep from 0400 to 0800, or right through until 1200 if you really need to. You'll always have the same period of time for sleep, for eating, and for general relaxation. But it has its disadvantages, too.
There are times when the whole crew will be needed. Maintenance periods will need to be built into the system on a long passage, and the best time for this is the Forenoon watch. So the Middle watch-keepers won't be able to sleep much beyond 0800, and will then have the afternoon watch.
If they're to catch up on sleep, they need to sleep from about six in the evening, so the main evening meal is eaten just before sleep. Not the best arrangement. On a fixed three watch system, the best watch to have is the forenoon watch, because that's the maintenance period anyway, and you can sleep in the afternoon, stand the First watch, and then sleep right through the night until you turn to the following day - brilliant!
But pity the middle watch-keepers, who have to turn to at midnight, get only four hours sleep, have to stand the afternoon watch, then get their main sleep from 1800. It works, but in my view it doesn't spread the pain enough, and on a long passage, resentments can creep in.
There are other issues to consider as well. Night-time watch-keeping can be either boring or nerve-wracking, depending on where you are. Sailing through a Spanish fishing fleet at one in the morning can be huge fun, or daunting, depending on how well you can interpret the various lights. The ideal is to keep completely clear, but at five knots it's not always possible.
My rule of thumb when I find myself surrounded by fishing vessels has always been to try to maintain a steady course, rather than try dodging this way and that to avoid individual vessels. At least then the fishing skippers can predict your course, and they can probably see you better on their radar than you can predict their course changes on a paper plot.
The golden rule is to keep clear, and that works for individual fishing vessels, but when you are surrounded by a whole fleet of them (and it can happen very quickly at night) trying to keep clear of one will almost certainly stand you into danger with another.
The point is that four hours of either total boredom or adrenaline pumping activity is a long time at night. And when you're tired, it's easy to make mistakes, get disorientated, or settle down in the warm Mediterranean night air, and find yourself fast asleep. Or if the weather is a bit lumpy, you won't see the spray that suddenly hits you in the face.
Either way, four hours at night is a long time. So I sometimes use a variation of the three-watch system that splits the middle and morning watches into two hours rather than four. This won't suit everyone. It means that you get only an hour and a half's sleep between night watches. But for short two or three day passages, I find it sometimes suits a crew better than the rotating three watch system, which takes a good few days to get used to.
Whatever system you use, stick to it. There's nothing worse than the skipper who starts off with one system, then finds he doesn't like it and switches to another mid passage.
Richard Thomas holds a Commercially Endorsed RYA Yachtmaster and Cruising Instructor (Sail) certificate. He runs his own delivery business, www.yachtmovers.co.uk He is available for deliveries, assisted passages, own-yacht tuition, and yacht management.
