No matter what the size of the yacht, there are only 24 hours in a day. Divide this by the number of crew onboard qualified to stand watch and you have the number of hours each crew member will be standing watch. The longer the passage, the more important this is as fatigue is a cumulative effect. Coming up with the right number of crew for a particular passage is crucial but more so on the longer passage and the one in challenging weather conditions.
Also to be taken into account is the equipment onboard that can help to reduce fatigue. Is there an autopilot available? A soft or hard dodger to get out of the wind and weather? Location of winches such that the single person on watch can reach everything if needed?
The policy on our yacht is for the person standing watch at night to wear their lifejacket, have a PLB in their pocket and clip the EasyRescue AIS unit on their belt. In addition, they need to be clipped into the one of the hard points located around the cockpit. On the HR, it's easy to do almost everything and remain in the cockpit however if one needs to leave the cockpit for any reason, another crew member needs to be woken up to help.
The security and safety of sitting in the center cockpit of a yacht under a hard dodger at 02:00 in the middle of the ocean is wonderful. Having a place to hunker down when the wind is cold or spray is constantly hitting the windshield is great as well.
Note on the hard dodger option for the Hallberg-Rassy... get it!
It's very important to crew morale to know everyone is treated fairly. Onboard there are always tasks that need to be done that may not appeal to all crew members. Some may be OK with cooking or cleaning up after a meal but are not enamored with cleaning a head (who is?). Everyone onboard should be assigned to do every task. There should not be just one person stuck washing dishes or cleaning heads all the time. Seems obvious but you'd be surprised how often this turns out to be the case. Better to post a written schedule and stick to it or have a clear understanding of duties before you set out.
I also feel that sharing meals together is important and we planned to have the crew member coming on watch prepare the meal for the others. We all sit down together and eat at least lunch and dinner together. We set the table and
For a recent passage from Gibraltar to the Isla de Canaria we had three of us onboard and decided on three hour watches with six hours off in-between. It worked out wonderfully. Over the four-five day passage we all felt rested and enjoyed cooking meals for each other. it was a great time made better by our choice of watch schedules.
Watches can be fun especially at night if you enjoy watching meteors or satellites going by and trying to identify star constellations. We have a nice application for our iPad, Star Walk that helps identify night sky objects for us and I'd highly recommend it. During the day, watching for 'critters' is always a crowd favorite too. On this last passage we had a number of dolphin visits, spotted some giant Sunfish and had a African Wood Warbler come visit for a day or so.
Enjoy your passages!