MOB on the ARC Rally

[Roberto]

Can an AIS transmit if it is submerged, as might happen in this situation?

No, not submerged nor even if very wet; well yes it transmits but it's all grounded into water and EM waves cannot go anywhere. Another likely problem, after having made such a large change in position coordinates, the beacon GPS could take several minutes before getting a fix: the boat was a VOR70 (?), what is its likely speed?
It depends also on the specific AIS MOB model, we tested some of them and some were almost useless: 5-10min to get a gps fix, no station beyond a few hundred meters could receive anything, etc. Some were very significantly better.
Except if having made one's own real life tests with the specific onboard model, IMHO it's the most overrated safety electronic device.

 

[westhinder]

No, not submerged nor even if very wet; well yes it transmits but it's all grounded into water and EM waves cannot go anywhere. Another likely problem, after having made such a large change in position coordinates, the beacon GPS could take several minutes before getting a fix: the boat was a VOR70 (?), what is its likely speed?
It depends also on the specific AIS MOB model, we tested some of them and some were almost useless: 5-10min to get a gps fix, no station beyond a few hundred meters could receive anything, etc. Some were very significantly better.
Except if having made one's own real life tests with the specific onboard model, IMHO it's the most overrated safety electronic device.

Which one performed best in your test?

 

[Deleted member 478]

No, not submerged nor even if very wet; well yes it transmits but it's all grounded into water and EM waves cannot go anywhere. Another likely problem, after having made such a large change in position coordinates, the beacon GPS could take several minutes before getting a fix: the boat was a VOR70 (?), what is its likely speed?
It depends also on the specific AIS MOB model, we tested some of them and some were almost useless: 5-10min to get a gps fix, no station beyond a few hundred meters could receive anything, etc. Some were very significantly better.
Except if having made one's own real life tests with the specific onboard model, IMHO it's the most overrated safety electronic device.

Thank you, that's very good info.

 

[BurnitBlue]

Not a good day for Sweden. The MOB and the unrelated incident of the abandoned leapord 45 are both Swedish. According to the Swedish news.

 

[dunedin]

Yachting World article:
'The yacht’s position was approximately 130 nautical miles east of Bermuda,'

Man overboard in ARC: US MRCC calls off active search. Another yacht abandons. - Yachting World

The map in the article clearly shows the boat mid Atlantic, a lot more than 130 miles from anywhere. As one might expect roughly a week on from the start.
Also anybody who has crossed this route would know no sailing boat would go anywhere near Bermuda heading from Gran Canaria westbound to St Lucia. Bermuda would be a huge northerly diversion, only taken on the return / Eastbound route.

But hugely sad for the family and rest of crew. Sadly ocean crossing is never risk free.

 

[Laser310]

No, not submerged nor even if very wet; well yes it transmits but it's all grounded into water and EM waves cannot go anywhere. Another likely problem, after having made such a large change in position coordinates, the beacon GPS could take several minutes before getting a fix: the boat was a VOR70 (?), what is its likely speed?
It depends also on the specific AIS MOB model, we tested some of them and some were almost useless: 5-10min to get a gps fix, no station beyond a few hundred meters could receive anything, etc. Some were very significantly better.
Except if having made one's own real life tests with the specific onboard model, IMHO it's the most overrated safety electronic device.

there aren't very many of these

i have tested several of the MOB-1 AIS devices, and I don't think any took 5 minutes for a GPS fix

They are very low power though - the MOB 1 is 0.5 watt

the signal is receivable even without the fix - i would like to know whether any signal was received.

They definitely work though...

I know this because in the days leading up to any big ocean race, my laptop's nav program display is littered with activations all around the harbour.

people accidentally activate them while trying to fit them to the pfd for automatic activation, and also when trying to use the test mode. the other thing that happens is that the PFD's with the dissolving wafer sometimes go off in heat and high humidity, causing the AIS to activate.

 

[boomerangben]

there aren't very many of these

i have tested several of the MOB-1 AIS devices, and I don't think any took 5 minutes for a GPS fix

They are very low power though - the MOB 1 is 0.5 watt

the signal is receivable even without the fix - i would like to know whether any signal was received.

They definitely work though...

I know this because in the days leading up to any big ocean race, my laptop's nav program display is littered with activations all around the harbour.

people accidentally activate them while trying to fit them to the pfd for automatic activation, and also when trying to use the test mode. the other thing that happens is that the PFD's with the dissolving wafer sometimes go off in heat and high humidity, causing the AIS to activate.

I don’t think it is surprising that you get good signals from MOB devices that are set off in the cockpit/cabin etc. but what about in the water? These things only work if held clear of the water. As for the GPS fix, did you test any that had been moved a couple of thousand miles since their last test? I’m not doubting your experience, just wondering if we are comparing apples with apples here

 

[john_morris_uk]

No, not submerged nor even if very wet; well yes it transmits but it's all grounded into water and EM waves cannot go anywhere. Another likely problem, after having made such a large change in position coordinates, the beacon GPS could take several minutes before getting a fix: the boat was a VOR70 (?), what is its likely speed?
It depends also on the specific AIS MOB model, we tested some of them and some were almost useless: 5-10min to get a gps fix, no station beyond a few hundred meters could receive anything, etc. Some were very significantly better.
Except if having made one's own real life tests with the specific onboard model, IMHO it's the most overrated safety electronic device.

IIRC Ocean Breeze was doing 10 to 12 knots when I last looked. (I’ve been monitoring another boat and checked out a few other boats at the front of the fleet while I was looking at the ARC tracking page.) Ocean Breezze was lying second behind a 105’ boat and like a lot of the boats her track appeared to show her gybing regularly.

 

[Roberto]

I don’t think it is surprising that you get good signals from MOB devices that are set off in the cockpit/cabin etc.

Not even. Have a look at the images at this link (I cannot link them directly)
AIS SART: caso reale
This was an AIS SART, so a boat AIS emergency beacon rather than MOB, the first image shows the active beacon, it was activated at a few tens of meters from my boat (the red icon above), OpenCpn rang the bells, no one on the VHF, I looked around the pontoon but could not see anyone. I radioed the CG (Cross) and told them I received the signal, they have a very dense radio coverage in all the area but could not see anything. I gave them the beacon MMSI 970xxxxxx but they could not find it in their database (owner fault of not registrering the beacon).
A few minutes later, second image, the mother boat had switched on its AIS txr (green icon near the red), now I had their ship MMSI, called CG again and they had received the boat AIS message too, I told them the two signals were one on top of the other so presumably from the same vessel, this time they found the boat MMSI, so could get in touch with the contact number --> there was no distress, the boat was simply testing the beacon.
I think the assumption "everyone around with an AIS will see your distress signal" is very, very optimistic with this type of beacons, even a supposedly "better" SART in optimal conditions.

 

[Minerva]

No, not submerged nor even if very wet; well yes it transmits but it's all grounded into water and EM waves cannot go anywhere. Another likely problem, after having made such a large change in position coordinates, the beacon GPS could take several minutes before getting a fix: the boat was a VOR70 (?), what is its likely speed?
It depends also on the specific AIS MOB model, we tested some of them and some were almost useless: 5-10min to get a gps fix, no station beyond a few hundred meters could receive anything, etc. Some were very significantly better.
Except if having made one's own real life tests with the specific onboard model, IMHO it's the most overrated safety electronic device.

That’s interesting in a concerning way. I wonder if they would fair better strapped atop a danbuoy in a MOB situation?

 

[Roberto]

Which one performed best in your test?

Hello,
it was not done in any structured way so prefer not to say (I cannot even remember, actually), it was just a group of friends with a few beacons and support from the local signal station (sémaphore) at a few miles distance. Occurrences:
Signals received from immediately to 4-10 minutes after activation
Signals not received by anyone (ok antenna in the water)
Signals only received by the motherboat AIS and not by other boats at a few hundred meters distance
Signals received by boats and not shore station
Signals received by both boats and shore station.
Also, people were all looking at their screens, but depending on systems: a) beacons could appear as just an additional regular target, b)there could be either be a visual/audio alert or nothing at all, and c) on a couple of other occasions I saw beacons appearing here and there when there was actually no one.
My impression, these Ais mob are very far from having enough reliability, why not wearing one but I would not count too much on it.

 

[Roberto]

That’s interesting in a concerning way. I wonder if they would fair better strapped atop a danbuoy in a MOB situation?

IMHO it would definitely be better. The antenna position should be considered: they are made to send polarized signals so the antenna should be kept vertical, lifejacket stuff often has an antenna which sprungs perpendicularly to the body of the beacon, so strapping the beacon to the length of a MOB pole would keep the unwinded antenna in an horizontal position, not the best orientation (though I have no idea of the loss in performance).

 

[capnsensible]

The problem as I see it with a danbouy is the time taken to deploy it. Even in a crew who are expecting a man overboard exercise. I've crash stopped lots of smaller yachts but never a Volvo 70 doing more than 10 knots. It's the best chance of getting a Danbury somewhere near the casualty but I get the feeling...supposition of course.....that something large, heavy and important might break.

 

[Minerva]

The problem as I see it with a danbouy is the time taken to deploy it. Even in a crew who are expecting a man overboard exercise. I've crash stopped lots of smaller yachts but never a Volvo 70 doing more than 10 knots. It's the best chance of getting a Danbury somewhere near the casualty but I get the feeling...supposition of course.....that something large, heavy and important might break.

I’m not considering the process for Volvo 70 - I am very unlikely to skipper one and be responsible for the crew.

I am however responsible for my family on my own 10m moody and thinking how I can better protect them…

 

[capnsensible]

I’m not considering the process for Volvo 70 - I am very unlikely to skipper one and be responsible for the crew.

I am however responsible for my family on my own 10m moody and thinking how I can better protect them…

OK, that's different. Thanks for clarifying. Speeds slower, everything easier.

I found that on boats this size, you will always have a reaction time problem still and may end up with danbouy some distance from casualty. My tips are to immediately heave to, pull in really hard on mainsheet and drift back towards mob. Then chuck them danbouy and flotation aid whilst you sort boat out and nip back for recovery. Of course there are many ways to finesse this depending on circumstances but regular practice with you family will help them to see what needs doing.

Releasing the danbuoy is aways a pita. They get easily tangled in just about anything. And of course, if they aren't secured against motion they just fall off. I've not used these inflatable ones but have wondered how effective they are.....provided they are maintained according to manufacturers instructions.

My experiences have always shown that reaction times to any emergency can be slow, even in a training environment so for me, practice is the best way to try and mitigate that.

We lived on our Moody 33 mk 1. It works! We would always have a short practice whenever we left harbour.

 

[Stemar]

It all seems to come back to the same thing. Don't go overboard.

 

[capnsensible]

It all seems to come back to the same thing. Don't go overboard.

Very true. But that's also a bit like saying don't have a car crash!

Stuff happens. Being prepared and practising is what nails it for me. Icluding practising tasks around a yacht whilst being clipped on. Don't have to wait until it gets bumpy.

 

[RunAgroundHard]

It all seems to come back to the same thing. Don't go overboard.

Of course, but as this and other incidents show, it happens, so how to maximise recovery is key.

We don’t know anything about this incident beyond a basic description, so my following comment is not relevant to this case.

If you experience an MOB and you’re a skipper, have you really drilled and trained sufficiently to recover the casualty? Do you understand in detail how to mark an MOB position, manage sails and boat to return to MOB, perform a search pattern and recover an incapacitated MOB?

If you just have a vague idea, or only practised on a Day Skipper course with a bucket and fender, then the probability of success is low.

 

[BurnitBlue]

I realise that this thread is an interlectual discussion about electronic MOB gizmos. Very interesting too. However there is a system dealing with MOB prevention.which has been in use for a hundred years or more. It is called a harness. Augmented by guard rails and flotation vests they can be maintained and tested before setting off.

This discussion should include the choice of whether it is sensible to rely on a gizmo that can and do fail. Or even whether or not to carry one at all. I spent most of my working life fixing and improving electronic equipment.so my mistrust is deeply ingrained.

Modern chips are fantastic and reliable but they work within limitations of voltage, temperature, humidity and surrounding items like cases and buttons and software updates. Remember that most items are only random tested. You, the wearer are their testing system with a warranty.

You have probably guessed that I would not be found dead wearing such gizmos frankly because it could turn out to be true. As the joke goes.

PS stenar mentioned "dont go overboard" as i wrote the above.

 

[flaming]

Sadly MOB from VO70 and VO65 have a bad history of fatality, even when fully crewed by the best offshore pros on the planet. There's a racing buoy in the Solent named in memory of one of the casualties.

When we practice MOB drills we know it's coming, so our reaction times are not "real". We're generally not going downwind with preventers rigged or kites up either. A real MOB in open ocean on a fast boat sailing downwind in fresh conditions at night.... There's a lot stacked against you right at the start, even before you start talking about it being a charter boat with paying guests, not a pro'd up boat.

All of the MOB aids, the PLB, the AIS transponder etc. They're all great. But the reality is that if you fall off the boat you are reliant on a lot of things going right in order for you to survive. Both in systems, and in the reaction of those people still on the boat.