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Old 13-02-2014, 20:29   #1
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Man Overboard Alarms & Devices

I've been pondering choice of MOB devices for our family for offshore cruising and would appreciate feedback and thoughts. We crossed the Pacific in 2011 and are heading out again long term cruising in 4 months or so.



We still rely on jacklines and harnesses to keep us aboard, but if it's a nice day we often don't clip in or wear the harness. Somebody might be in the cockpit and somebody else may be inside reading a book or making lunch. We're a catamaran so motion is generally less and heeling isn't an issue. In other words I feel less likely to fall overboard on our boat than sailing on previous monohulls.

But we still approach walking around as "if I go for swim I will probably die".


Here's the choices as I see them:

1) MOB Alarm. You wear a device that talks to the base station. It polls the device and if the device doesn't reply (out of range or in water) the Alarm sounds. But doesn't give any indication of where the MOB is located. Activates automatically (MOB doesn't have to do anything)

Examples: Raymarine Lifetag, MOBI-lert.

I think these have been superseded by better options.


2) AIS Beacon. A new choice in the marketplace.

The MOB activates this once they hit the water. It sends a AIS distress alert out. Your AIS receiver sounds an alarm, and if it's got the right software, the AIS target shows up as a different symbol (circle with an + in the middle). Our Standard Horizon GX2100 VHF apparently will sound the alarm but the target will only show up as a standard AIS target due to old software. Helpful for the crew left on board because they have a target to steer towards. Probably we would only get 1 and the person on watch would have it worn in a belt pack with a few flares and small waterproof light when changing watches. If both of us are on deck it's unlikely that a MOB will occur and the 2nd person left aboard will not notice so I'm only thinking 1.

About $300 each

Examples: http://www.kannadmar...en/safelink-r10


3) waterproof VHF with GPS/DSC. Another idea to find the person. Again, the MOB activates it when they hit the water. The MOB pushes the DSC "Distress" Button and the VHF with DSC on the boat alarms with a DSC distress call. Our VHF gives the Lat/Long of the distressed person but doesn't give you a steer to waypoint until you do a few button presses but not too difficult.

If the chart plotter is on, it will also see the Distressed DSC person as a target (OpenCPN does this apparently). The MOB can give directions to the boat as the boat gets closer and discuss how to be picked up and steer them the last 100 m... Heck if the MOB acts quickly they can drawl "honey I'm about 1/4 mile astern, can you come and pick me up...."

Example: http://www.standardh...=3&isArchived=0

About $250


4) 406 MHz PLB - forget about it. By the time a rescue agency gets a fix the MOB has been in the water for some time and areas we are in there won't be a local coast guard to find them for any time.

In all these scenarios we assume we are far away from civilization, cruising in isolated areas or in countries where any CG is barely there if at all. Our PFDs are manually inflating so we assume if we are knocked unconcious, we're probably gone anyway so manual activation of a device is OK with us.



I am strongly leaning toward #3 as I can use the VHF on a regular basis to test it. And another waterproof VHF is a good idea if we ever have to abandon ship. The person on watch would be wearing it so it's likely to come along in an abandon ship situation.


I'd appreciate your thoughts.
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Old 13-02-2014, 21:23   #2
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Re: Man Overboard Alarms & Devices

Go for #2. I just threw my Mobilert into the dumpster.

The Kannad is a McMurdo device so very good.
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Old 13-02-2014, 22:26   #3
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Re: Man Overboard Alarms & Devices

The gold standard would be a PLB and getting a RDF set to the 121.5 frequency. I don't have one, and haven't played with them, but they are available starting in the $200 range.

Possibly backed up with an ais transponder or MOB alarm.
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Old 13-02-2014, 23:11   #4
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Re: Man Overboard Alarms & Devices

I just went through the same questions.

I went for 2, 3 and 4. For a few hundred bucks, why not.
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Old 14-02-2014, 00:05   #5
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Re: Man Overboard Alarms & Devices

I see some flaws in your logic:

1)- the MOB is assumed to have his AIS Beacon or portable VHF unit on his/her person at all times, so it is ready to activate once the MOB hits the water.

On most boats I've been on /around, mobile radios are left at helm stations, in staterooms, or on their chargers. I'll assume that the same would be true of an AIS beacon. Not practical.

2)- the MOB is assumed to be clear of head once the MOB situation occurs, and to have the situational awareness to activate the MOB device manually without dropping the unit into the depths.

When we trained for MOB in the Navy, we were taught that person in the water was to be assumed to be catatonic, and not in their right mind; survival instincts have taken over from logical thought.


I think that the Raymarine Lifetag would be a very logical choice- slip the transmitter onto a wrist/belt loop and its worn at all times. Very unobtrusive and light, and will not occupy a hand that would otherwise be carrying a radio.

When the MOB occurs, the chartplotter puts a MOB symbol (approximate position) onto the screen, and a loud audible alarm sounds.

To me , this seems like a system that will be utilized much more than the other options.
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Old 14-02-2014, 00:11   #6
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Re: Man Overboard Alarms & Devices

Just a thought but if you had a MOB situation, say mid Atlantic for example, and the MOB had a PLB. If you contacted the Coast Guard via Sat Phone would you be able to get the GPS co-ordinates? If you had the Sat Phone number registered as the primary contact on the PLB, maybe they would even call you.

Not as good or accurate as some of the other options but better than nothing if you didn't have any other means of location. I don't see why it wouldn't work but I don't know CG procedures - I was just wondering if it was possible.
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Old 14-02-2014, 00:15   #7
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Re: Man Overboard Alarms & Devices

The portable AIS device we have is small and attached to our life vest at all times.
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Old 14-02-2014, 21:00   #8
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Re: Man Overboard Alarms & Devices

Yep, number 2. AIS SART . Like this
AIS SART
And yes I'd like to sell you one, of course. I picked this type of SART, because it's what I think is the best. Your call of course, I'm happy to discuss.
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Old 14-02-2014, 21:18   #9
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Re: Man Overboard Alarms & Devices

The Kannad AIS beacon is small enough to fit easily on your person, or stuffed inside an inflatable PFD. The Kannad beacon can be attached to some PFDs so that it auto-triggers when the PFD inflates. This would be an excellent solution.

I have the Kannad beacons packed inside our PFDs, but the beacon requires yanking a ripcord to activate it (since my PFDs aren't compatible with the Kannad auto-trigger).

These AIS beacons are useful when your boat is able to rescue the MOB, and possibly when used in well-traveled waters, but I suspect that most recreational boaters wouldn't recognize the MOB symbol or alarm when it popped up on their AIS/chartplotter. It's also not a substitute for a PLB -- that's a different thing.

For what it's worth, I also have a receiver made by ACR that triggers an alarm when it hears the 121.5 MHz homing beacon from the PLB. This was a nice receiver, and not horribly expensive, but unfortunately ACR no longer makes these.
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Old 14-02-2014, 21:20   #10
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Re: Man Overboard Alarms & Devices

For option 3, even if the MOB wasn't able to press the DSC Distress button the mothership can send a position request to the unit as long as someone aboard realized that there was someone missing and the unit was on at the time.

Our 'on-watch' kit includes a PFD with a Standard Horizon HX851 clipped on.
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Old 14-02-2014, 22:30   #11
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Re: Man Overboard Alarms & Devices

Go for #2

I stopped using the Raymarine Lifetags because they -too often for my taste - set off accidentally, the button being easy to press inadvertently while on watch, for eg if you have it clipped on to your pfd or your foulies.

Just bought a MCMurdo AIS beacon for around 200 Euros - It is more effective than the lifetag, not just for MOB, but also for SAR, as all boats nearby will pick up the AIS distress signal.

The prices seem to be coming down on these types of devices, a year ago they were retailing around 250 Eur, if you can wait...
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Old 14-02-2014, 22:37   #12
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Re: Man Overboard Alarms & Devices

Its amazing what people will spend to attempt to overcome their fears and add to their perceived sense of safety.
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Old 14-02-2014, 22:42   #13
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Re: Man Overboard Alarms & Devices

It's amazing what people won't spent to increase their safety.
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Old 14-02-2014, 22:54   #14
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Re: Man Overboard Alarms & Devices

I wasn't trying to jerk any ones chains but I also wanted to make a point, most of the so called safety is perceived.
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Old 14-02-2014, 22:56   #15
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Re: Man Overboard Alarms & Devices

You have any stats to prove this? How can triggering an alarm and having an exact location back to a MOB be 'perceived safety'?
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