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Old 01-02-2012, 23:40   #1
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Best MOB Alarm System ?

My partner and I will be crossing the Pacific this year in a Beneteau 423. At times (for the long crossings as far as the Marquesas) we will have a couple of crew members, but for the majority of the remainder of the trip it will just be the two of us.

We want to get a MOB alarm system for obvious reasons, and I'm just wondering if anyone can recommend a particular system over another?

The systems around that we're considering are:

Autotether - "The Screamer"
NASA Marine Mobi alarm
Raymarine Lifetag

I realise that there are probably better, and certainly more expensive systems but these are out of our reach and I'm looking for feedback specifically on the above.

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Old 02-02-2012, 00:32   #2
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Re: Best MOB alarm system?

I'm glad you asked-- I also hope to get one of these systems for my family and want to learn about them.

You specifically asked not to be told about other systems, but this has a low incremental cost if you do not already have a handheld VHF -- the Standard Horizon HX851. This radio can send an AIS GPS report that is then plotted on your navigation system. Our plan is that whoever is on night watch will have this strapped to their harness, and god forbid they fall overboard, this may help us find them in the darkness and waves.
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Old 02-02-2012, 00:57   #3
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Re: Best MOB alarm system?

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Originally Posted by msponer View Post
I'm glad you asked-- I also hope to get one of these systems for my family and want to learn about them.

You specifically asked not to be told about other systems, but this has a low incremental cost if you do not already have a handheld VHF -- the Standard Horizon HX851. This radio can send an AIS GPS report that is then plotted on your navigation system. Our plan is that whoever is on night watch will have this strapped to their harness, and god forbid they fall overboard, this may help us find them in the darkness and waves.
the hx851 can send a DSC call, not AIS. but it is a really good idea
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Old 02-02-2012, 01:01   #4
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Re: Best MOB alarm system?

That's the solution we put in place. Even if the person is unconscious the radio can be set up to automatically respond to a position request from a DSC radio on the boat. The HX851 also has a nice strobe light.
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Old 02-02-2012, 05:28   #5
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All well and good, but if there's only two of us on the boat, one on watch and the other asleep, how would this system let the crew know that someone had fallen overboard?
Definitely a good idea in aiding the recovery, but without an alarm as the person hits the water, it's not a complete system. Unless I'm missing something?
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Old 02-02-2012, 11:08   #6
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Re: Best MOB alarm system?

Hi.
Yes, it's true, I don't know if this radio has an auto-wet-DSC alert function. The sales sheet mentions something about a blinky light that goes on when it gets wet, but I don't know if it does more than that. If not, the person in the water would have to use the radio to either send off a DSC alert (that'd make your radio beep) or just call you on the radio (if the volume was up loud). Which of course does not work for someone unconscious and etc. Though not to be morbid, but ... for one person to retrieve an unconscious person from the water, you'd have to be very skilled and very lucky with the conditions. Since they can't just grab a rope that you throw to them and then you pull them to the boat, you'd have to somehow drive the boat nearly ontop of them so that you could snag them with a boat hook or, tie yourself to the boat and then jump in and get them... Both seem to need very flat seas. Jumping in after them (with no one else on the boat) takes a kind of true love suicidal devotion-- "I'm going to die with you, you bastard"-- kind of thing.

Sorry, I'm rambling. I think if I were to have to choose between a manually activated homing beacon VHF thing and an automatic thing that doesn't help you find the person. I'd go with the homing beacon, since falling overboard at sea is nothing like swimming in an anchorage. In many conditions the persons head would disappear in the waves before you'd wake up and get up on deck. So... in some sense, the MOB alarm would give you a fighting chance, but I feel it's pretty dubious.

Though I did once "rescue" crew in the Coral Sea who had jumped overboard after a boat hook. It was calm, there were three other people in the cockpit that watched her do it, kind of surprised, and thus it was very, very easy to get her. An MOB alarm would have worked in that case, maybe even at night if it marked the GPS position, because it was calm enough that we could have come back to where she left the boat and then waited and blown the fog horn and shine flashlights around so she could find us and swim to us. But in the more common conditions where a swimmer usually can't see a boat more than a couple hundred yards away... I don't know.

But it's of course best to have both.

The problem with this type of safety technology is that pretty soon you are spending a lot of money to go from 99% safe to 99.2% safe and then 99.23% safe and etc. So it's hard to draw the line with hypothetical situations. Which I think is why many people do not have MOB alarms.
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Old 02-02-2012, 11:41   #7
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Re: Best MOB alarm system?

jack lines and a harness, with a line to the ships bell ! old timey but it works .On the sailing vessels I have had or deliverd, the on watch hand was required to use harness and and jack line at night or whenever weather required it's use . always worked for us ! Bob and Connie
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Old 02-02-2012, 11:44   #8
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Re: Best MOB alarm system?

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There are inexpensive (under $50) gadgets sold for LUGGAGE of all the odd things. One fob goes on the bag, the other in your pocket. If you get more than 50' away from the bag, or it gets moved away from you, the one on the bag starts screaming.

So even if you get a "marine grade" MOB system? A couple of these, sealed into plastic bags, make a cheap backup. Obviously the "screamer" stays in the boat and the pocket fob goes with the deck watch. Small, simple, cheap, easy enough to buy and keep a spare and have one assigned to each of you, left in the harness or PFD all the time. Probably available at Magellan's and Brookstone's or Hammacher-Schlemmer if you don't find a cheaper source.
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Old 02-02-2012, 11:55   #9
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Re: Best MOB alarm system?

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jack lines and a harness, with a line to the ships bell ! old timey but it works .On the sailing vessels I have had or deliverd, the on watch hand was required to use harness and and jack line at night or whenever weather required it's use . always worked for us ! Bob and Connie
As I read this, I was thinking clearly there should be some easy way to make sure you remained on board first and foremost.

I have no experience in this myself yet as we've never had to strap in at any time, but I would think you could treat it like they do working on skyscrapers. You don't unclip from one line until you are clipped into another.
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Old 02-02-2012, 11:55   #10
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Re: Best MOB alarm system?

There was a story on here some years ago about a man who went OTS in the Caribbean. His wife was woken by the cat. She searched for him for hours, finally finding him at last light. After getting him back on board, and the tears and hugging, he apparently said "D'you know, all the time you were searching for me, I never lost sight of the mast. You just did not know where to look"

Since we read that, a waterproof hh vhf has been our preferred system.
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Old 02-02-2012, 13:52   #11
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Re: Best MOB alarm system?

"You don't unclip from one line until you are clipped into another."
That's the theory and modern tethers have two clips, two ends, for that purpose. Theories don't impress Poseidon. He'll just snap the one jackline your two tethers are both tied into, or snap the one while you're reaching with the other.
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Old 02-02-2012, 16:48   #12
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Re: Best MOB alarm system?

I would get one of the new AIS based systems.

The major issue in most MOB situations is to find the person. With an AIS MOB system you know where the person IS, not where they WERE when they went overboard.

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Old 02-02-2012, 18:11   #13
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Re: Best MOB alarm system?

The new stuff is good !! no question. But the old stuff works to ! and it cost's a heck of a lot less ! some of us can't find the bucks to buy more fancy electronics we would rather use a tried and true and less expensive harness. And spend the difference cruiseing more ! just a old timers 2 cents Bob and Connie
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Old 02-02-2012, 19:02   #14
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Re: Best MOB alarm system?

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"You don't unclip from one line until you are clipped into another."
That's the theory and modern tethers have two clips, two ends, for that purpose. Theories don't impress Poseidon. He'll just snap the one jackline your two tethers are both tied into, or snap the one while you're reaching with the other.
I hope you're not saying that tethers and jacklines don't save lives and that they shouldn't be used. They do and they should. If these break, they've either been improperly installed or improperly maintained.

As for MOB alarm systems, you need to look at what you want them to do.

PLBs can be a useful MOB alarm if you have a local beacon receiver on board. The MOB needs to be conscious and able to activate the PLB, and the Coast Guard (etc) will also be notified. This may or may not be what you are looking for.

There are beacon-type alarms that *only* trigger an alarm on the boat. Some of these must also be manually activated, but I believe that some are water-activated.

The "dead man" style alarms (such as Raymarine's LifeTag) automatically trigger the on-board alarm once they go under water or otherwise get out of range. These give you no homing signal, and you need to keep the alarm's battery charged. Look at how you would use these, the battery life, and the possibility of nuisance triggering on larger boats.

There was a dead-man alarm that used a sonar signal with multiple through-hull sonar detectors, and this allowed for homing in on the MOB (within a certain range). Pretty complicated IMHO.

There is a new breed of AIS-transmitting MOB beacons. These are just starting to become available, and you may need to update your on-board AIS system in order to get a local alarm. I don't think these are approved in the USA yet.

The handheld VHF with built-in GPS and emergency DSC capability is attractive, if a bit bulky. The battery life may be too short to keep the unit on at all times, and if you keep it off until you go OB, you need to be conscious and able to turn it on (and press the button).

On my boat I have PLBs stuffed inside our auto-inflate PDFs, and a beacon receiver/alarm on board. This isn't a perfect solution, but so far nothing is (at least not for my boat).

Sorry, I have no personal experience with any of these other approaches.
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Old 02-02-2012, 19:10   #15
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Re: Best MOB alarm system?

one could fabricate a system like the tethers on the ignitions of jet-skis that cut the power when you bail. But instead of cutting the power, it sets off an alarm. That combined with one of thoses VHF's that have a locating becon sounds like a good set up. Although i would just tie in to a lifeline and not leave the boat in the first place.
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