Missing sailor

[alanhanson]

i have just purchased 2 sea marshall 121 mhz beacons to be worn round the neck the neck band also lights up
i also bought the locator device which stays onboard for the persons left onboard to home in on you.
not much use if you are single handed.
but good if you have other crew.

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[wishbone]

I am planning on doing some singlehanded, I have my diving dry suit, very easy to get in and out of and easy to move around. if weather is bad I may be tempted to wear it. it's the sort that rnli use! I seem to remember a sailor surviving in low temps for 12 hours because he was wearing a dive suit after falling overboard!

<hr width=100% size=1>Wishbone
Rolling, rolling, rolling keep them doggies moving!
Where’s me chuck wagon gone?

 

[bedouin]

I suspect those figures relate to people wearing light clothing and not wearing a lifejacket. Wearing a lifejacket, especially one with a sprayhood, vastly increases expected survival times.

The "expected" survival time of an average adult in 10C water wearing an LJ is said to be 7 hours, compared to 1.5 for someone swimming. Wearing standard yachting oilies will give some additional protection.

I would imagine that the average time to being rescued from activating a 406 EPIRB in the Channel is about 3-4 hours. So falling in in LJ, carrying an EPIRB, I reckon the chance or survival is better than evens.

Yes, clearly it is better not to fall in in the first place but equipment does fail.

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[longjohnsilver]

Interesting figures, 1.5 v 7 hrs, where do they come from? Surely the main danger is hypothermia and I can't see how wearing a LJ will extend your survival time by a factor of 5.

Appreciate that a sprayhood will make quite a difference, but in reality how many leisure sailors have a LJ with one of these? I can't recall even seeing one for sale anywhere.

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[bedouin]

The figures came from the Internet somewhere - found by Googling.

I think there are a number of causes why the LJ helps:

Primarily if you don't have a LJ then you have to swim/tread water to keep afloat which wastes a lot of heat. Secondly the LJ allows you to adopt the curled up position that helps to minimise heat loss.

In water 25% of heat is lost through the head, the LJ holds the head out of water so vastly reduces that.

Finally the LJ itself covers a significant proportion of the "core" body area and acts as insulation in its own right.

Anyone who races will have lifejackets with sprayhoods (and crotch straps). Most manufacturers supply them as extras for their lifejacktets and fit them as standard on their more expensive models.

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[IanR]

DSC MOB?

What options if any exist for the MOB detector to trigger a DSC signal with the GPS location of the trigger?

It would seem that allowing for the obvious false alarms, the technology is in place to lik a MOB wristband with DSC and maybe even the autopilot, mind you it could spoil your evening even more to see your pride and joy sailing around you in circles like a toy train!!!!

I have seen components of this but not all three, does anyone know different?

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[Goby]

You may all be interested in the following:
121.5 MHz beacons are available at low cost and because of this there are about 680,000 of them around world wide. The frequency that they emit is picked up by SAR satellites but the information that they transmit is not reliable as position information cannot be transmitted. A SARSAT will need more than one pass to get a reasonably accurate position (within 10.8nm ).

The technology behind them is outdated and SARSATs cannot differentiate between them and other types of transmitters in this band. This causes a great deal of false alerts in the system and has significantly increased the work load of RCC's worldwide, because of this the IMO ( International Maritime Organisation) has asked for COSPAS-SARSAT processing to be discontinued from 2008.
If you are going to buy an EPIRB get a 403 preferably one which is tied into your GPS.

121.5mhz
100mW output
Transmits continuously
Local mode only
Position accuracy 10.8nm
battery life 48 hours

403mHz
5 Watt radio signal
Signal burst 0.5 seconds duration
Signal transmitted every 50 Seconds
Fitted with homing signal (Currently either 121.5 or SART)
Global coverage mode
Detection probability 98% on first SARSAT pass
Location accuracy 90% within 2.7nm
Battery Life 48 hours.
For further information try a search on COSPAS-SARSAT, GMDSS

Note. Local mode means that the if there is no LUT in the footprint of the SARSAT the information is lost.

Global mode means that information is stored on the SAT until it detects an LUT in its footprint, it will then download the information to the LUT

LUT (Local User Terminals track the satellites, ours is in North Devon)

Hope this helps


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[Goby]

Ref my last post
Sorry I meant 406MHz not 403

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[alanhanson]

is the 10 miles accuracy from a satelite ?
as i have a onboard locator which guides you back to the 121 and will not even pick up a signal at 10 miles
but this is onboard.
i have just run it in test mode and it is accurate for guiding back to a few hundred metres.

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[Goby]

Yes the 10.8nm accuracy is from the satellite, once it has resolved the position but as I have said the 121.5MHz is not that accurate and will normally need more than 1 pass of a SARSAT to resolve the position; this could take as little as 1 hour and as much as 4.

Once the position has been resolved by the SARSAT search units are tasked and can then home in on the beacon. The height of the beacon will determine how far it can be detected by surface units, which may not be very far but a high flyer such as military or commercial jet could pick it up from a fair distance. In fact a lot of the reports the SAR authorities get are from high flyers.

Hope this helps

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[alanhanson]

thats fine as i bought the 121 as a local homing device
i have a 406 gps for outside assistance which also has 121


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[Goby]

Yes, the 121.5MHz is ideal for crew to wear, then if they go over you can turn around and home in on them providing of course it's not too long before you miss them. The main thing is to have some sort of system so that you can find them again.

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[rallyveteran]

A missing yachtsman has turned up safe at home - a month after his vessel was found smashed on rocks.

http://news.bbc.co.uk/1/hi/england/hampshire/dorset/3936451.stm

Bizarre!

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