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Comment by sparker72678 | Hacker News Reader

Any idea what motivated the decision to run on an 18 hour day? You mentioned the drawbacks (widespread fatigue), but there must be some (many?) benefits. I'm curious what those might be.

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There's only enough space to have 3 sections of watchstanders on board. So then it becomes a matter of length of watches. 6 hour watches aren't too long, and match up to meals every 6 hours. It's easy/straightforward, and no one gets screwed with always having watch on the midwatch and then also running drills during the day (meaning very little sleep).

8 hour watches could be a bit long, and more problematic is that crew members would always be on the same watch: 0000-0800, 0800-1600, etc. That's potentially even more disruptive.

Back during the age of sail it was common to divide the ship's day up into seven watches with five four-hour watches plus two two-hour afternoon "dog" watches. That way no one had to stand the same watch every day. But fatigue was still a problem, especially on vessels that were short handed and only had two watch sections; crewmen were frequently punished for falling asleep on watch.

> crew members would always be on the same watch: 0000-0800, 0800-1600, etc. That's potentially even more disruptive.

Does that really matter underwater? After a few days it is just as if you moved to a different time zone. It’s not like one watch would get more sunshine than the other.

8 hours is a ridiculous length for something like sonar. Sonar, even if you are just steaming from one location to another, you are constantly working, thinking, checking, updating. I'm not sure how it has changed since my time, but it was exhausting, and we had to do 8's a number of times when we were short operators.

For me though 6's were worse. You lose your sense of which direction 'up' is in time.

Makes sense. Thank you for the explanation!

You're not just standing watch, though. There's training (SO MUCH TRAINING), drills (SO MANY DRILLS), meals, and at least a little time for movies/relaxation. Trying to fit all this in is more complicated with 8 hour watches. (With 6 hour watches, you do all training/drills in the 0600-1200/1200-1800 time periods, and it works out easily.)

Oh I see, i didn’t think about the extras. I thought watch means all of those things too.

Thank you for the explanation!

Got it - thank you!

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