I don’t think we find anything as worrisome as the idea of a man overboard. Since we often sail with just two on board, one of us is always on watch, while the other needs to try and sleep in order to stay useful. For me, the idea of waking up to find that Lisa had disappeared in the last few hours is truly horrifying. So, we take measures to keep that from happening. We wear life jackets underway. We use a harness at night staying physically attached to the boat even in the lightest conditions. We agree to wake the off watch before doing anything on the foredeck. We do our utmost to contain this risk.
The icing on our cake of man overboard protection is the Ocean Signal MOB1 device. This compact unit is installed on our life jackets and is automatically triggered when a life jacket is deployed.
DSC (Digital Selective Calling) is an alarm system that lets a radio user “ring” a specific radio using the radio’s MMSI number. Like a telephone number, the MMSI number allows another user to contact a specific vessel in the area. The MOB1 uses this system to “ring” ALL the radios in the area, so that not only our boat, but every other boat in the area gets an alarm that says MOB. This happens seconds after the person hits the water. On Footloose, our ICOM M506 marine VHF rings loudly enough to wake the off watch.
AIS is another electronic system that is normally used to identify other vessels by showing them on your chart plotter. In about one minute after entering the water the MOB locates itself using GPS and begins to send an AIS signal to all chart plotters in the vicinity that are equipped with AIS. This places a return on the chart that says Man Overboard, and marks the exact position of the device/person on the chart.
Our average cruising speed is about 7 knots which translates to 12 feet per second, so in only one minute our boat has moved about 700 feet. While the standard procedure for man overboard is for the crew to keep one set of eyes on the person in the water, for a couple cruising there is no way that can happen as the person on the boat needs to get the boat stopped and turned around. The MOB1 acts as the additional watch stander, allowing the driver, even when they can’t see their partner in the water, to maneuver the boat to the position marked on the chart by the MOB1. When they are close enough (GPS accuracy is well under 100 feet), they should be able to see the person or the flashing beacon on the MOB1 if it is night time.
On Footloose, we carry six inflatable life jackets with harnesses and installed MOB1 devices, which we test once every 6 months.
Here is a video we prepared for crew training that demonstrates how the MOB1 works, and yes, it was made before we changed to the ICOM.
