MOB Epirb Mayday

[Scotty_Tradewind]

As/Simon.... when offshore always keep the track shown on the plotter.. so valuable to keep that and MOB leeway in mind when doing a search

 

[haydude]

Would you remain in the area ? For how long ?

It depends ... Se e' la suocera ...

 

[Seajet]

I think the answer to the question ' how long would I search ? ' boils down to whether I knew the MOB's PIN number or not; then I am half Aberdonian !

Just a thought re. danbuoys & floating markers, a lot of us who've been on sailing courses can confirm a fender tied to a bucket works well; not as good as a proper danbuoy by any means, but might be a useful supplement to mark a search area ?

 

[Scotty_Tradewind]

If ther'e an MOB in bad conditions time is extremely limited.
Seconds count, so bucket to fender may be the last thing I'd want to organise providing all other basic gear is available. If not, why not!

Possibly o.k. in clear calm conditions to aid other recovery systems. ??

 

[Simondjuk]

The tide acts on both boat and mob, so disregard it. The wind only affects the boat.

We had this argument when two of us went overboard in 1974.
"Why didn't you chuck the lifebuoy?" (he saw us go, and was nearer the stern than us)
"Because the tide would have taken it away from you"

"My dear chap, you're talking absolute balderdollocks!" or words to that effect.

Sorry, what Margetts said...

I don't think I'm explaining myself properly. I know the tide acts on everything in the water - MOB, danbuoy and boat - and that what your man said back in 1974 was nonsense. The relationship between MOB and danbuoy will remain constant once both are in the water, but in the example given in the OP the MOB happened some time ago as we've already lost visual contact with him, so it's going to be necessary to travle some distance from the danbuoy and the MOB will have been carried by the tide prior to the launch of the danbuoy.

Before going motoring off looking for him then, throw the danbuoy in to give a visible object which will behave like the MOB due to the tide and provide a reference. The boat won't behave like the tide as it'll be motoring in a search pattern across, with and against it. If the pattern were perfectly symmetrical, the tide would keep the search pattern aligned with the tidal drift experienced by the MOB, but it won't be so give yourself a visual reference.

 

[Simondjuk]

As Simondjuk and Seajet say its important to get a reference marker into the water at the best estimated MOB position ASAP. That gives you something to baseline a search on. A proper dan-buoy will move down tide at a similar rate to MOB. Failing that put out a fender or two. Why not attach the EPIRB to the dan buoy also, or just chuck it in the sea? It's more useful near the MOB than on board now - any later rescue attempt can use it, you cannot.

A box search is done around a floating reference mark, so tide can be ignored. Your initial circuit is done at the distance you can just see the bottom of the buoy, and you increase by this distance each circuit.

In strict answer to the OP question, after the failed seach and no radio contact. That would be the (too late) time to activate and DEPLOY the EPIRB and danbuoy or other floaty device. Also deploy the liferaft - MOB might get to it. Then head inshore to make radio contact.

I agree except that searching in a box from the 'now' point where we've deployed the danbuoy is pointless since there's no way the MOB will be uptide or uptrack of that point, so why waste time looking there. Better a squared zig zag search back down the track line, offsetting for estimated tidal drift of the MOB between him falling and the search commencing, during which time the boat may have been going in any direction relative to the tide.

 

[ithet]

I agree except that searching in a box from the 'now' point where we've deployed the danbuoy is pointless since there's no way the MOB will be uptide or uptrack of that point, so why waste time looking there. Better a squared zig zag search back down the track line, offsetting for estimated tidal drift of the MOB between him falling and the search commencing, during which time the boat may have been going in any direction relative to the tide.

Agreed, but when you have passed the point on the backtrack where the MOB ocurred you need to search from your best estimate with an expanding circle of uncertainty - all moving down tide. The OP was asking about the case where initial seach had failed.

 

[Scotty_Tradewind]

leeway of an MOB.....


My instinct is to say that tide is most effective but at which point does a lot of wind become more effective than a little tide ?

I can imagine many variables over a few hours.

 

[Simondjuk]

Agreed, but when you have passed the point on the backtrack where the MOB ocurred you need to search from your best estimate with an expanding circle of uncertainty - all moving down tide. The OP was asking about the case where initial seach had failed.

Indeed so, if the initial squared zig-zag search back down the track fails. At that point, commencing an expanding square pattern search would make sense, but so as not to conduct one in which the squares start taking me uptide of the danbuoy I launched previously, that portion of the search square being of no use, I'd take the time to calculate a new start point for the search.

Assuming I can still find my danbuoy, plotting its current position and comparing that to the position at which I launched it, as marked by the GPS MOB waypoint recorded within the same minute or so, and knowing the time elapsed between when it was launched and when its at its current position will give a very precise picture of set and drift.

Using that data, I'd plot the point on my GPS track midway between where the MOB was last known to be on board and the point at which he was discovered missing. Then I'd plot the set and drift of the danbuoy from that point, adding to it a distance allowance equating to how far the tide would have taken it if it had also been in the water for half of the maximum possible time between its launch and the person last being known to be on the boat.

Let's say, for example, the MOB made a log entry at 1800, so we know they were on board then, it's now 1900 and the danbuoy has been set 1 mile to the west since it was launched at 1830 when the person was missed. I'd assume the MOB went in at 1815, so add an additional 0.5NM to the danbuoy water track to allow for the midway point of the additional time the tide may have been carrying them versus how long it has been carrying the danbuoy. I'd then plot this from the track point which corresponds to 1815, and make the resultant lat/long my search start point. It should only take a couple of minutes to do and would be time well spent to turn the search from a failed visual one into a viable navigational one.

 

[Simondjuk]

leeway of an MOB.....


My instinct is to say that tide is most effective but at which point does a lot of wind become more effective than a little tide ?

I can imagine many variables over a few hours.

I can't say I've ever consciously noticed that I'm swimming upwind. Can you?

 

[Scotty_Tradewind]

I can't say I've ever consciously noticed that I'm swimming upwind. Can you?

No but doing my refit often seems the equivalent of swimming against tide and wind..

 

[Seajet]

I can't say I've ever consciously noticed that I'm swimming upwind. Can you?

Well yes, but that was off a beach trying to reach someone in trouble; I'm sure a MOB could sense where upwind was, but I wouldn't think they'd choose to go that way unless there was a reason, such as making for the danbuoy / lifebuoy maybe.

 

[Sybarite]

After all these Mayday procedure threads, suppose the following:

You are sailing offshore, say 100+miles from the coast, or outside of VHF range anyway.
Man overboard, after a bit of circling you lose sight of the unfortunate person. The water is warm, so hypothermia risk leaves quite a few hours of hope.
You try to send a VHF Mayday in case there is a ship around, but no acknowledgement.
You write it on the log book.
Then:

Would you activate the epirb ?
Would you remain in the area ? For how long ?
What other things would you deem appropriate or sensible to do ?


Would your course of action change in case of different distances from the coast? for example would you do something different in the middle of the ocean in respect to being 50-60 miles offshore (in which case in a few hours sail you could be inside VHF coverage for example ?

There might be a case for having mast steps. Higher up you have a better view.