April WNS Supplemental

T

TonyJones

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This WNS revealed that several people considered the originally intended crossing distance of the motor cruiser to be inadequate at 0.7nm. (It was deliberately set up like that to produce the 'awkward situation' when the mobo's speed reduced, not because I considered it to be safe).

What distance would YOU consider safe assuming your speed to be around 30kt and the ship's to be in the low to mid twenties? This is not a trick question or anything; I'm simply curious.

Best wishes
TJ
 
Ah, but it's more complex than a straight calc of "how far in front".

It seems that this channel contains only two ships, and going astern of both would have taken us less than two minutes - getting astern of that slower one means we approach his stern at around 40knots net. So I wouldn't go ahead, and i think that's what others were alluding to too.

But if there were lots of ships like in gibraltar or English channel etc when going behind one means in front of another, and then I supose 0.7nm is okay.... but even then, i wouldn't choose the TJ option yeehah of going in front of TWO ships one overtaking another, which obviously carries extra risk - i'd go ahead of a slowish lone ship, and behind faster combo's, such as in the example, and especially if channel otherwise empty.

So, yes -I think 0.7nm is safe -BUT in the example there's a safer ption, hardly takes any time at all, and wouldn't be in that mess.
 
0.7 definitely too little in those open water circs. 2nm is more like it. I am talking pure pen water, not busy places when less is ok. Of course, you'll have seen/radar-ed the ship miles beforehand and only a small speed/course adjustment will give you the two miles.

Ever done that thing where you approach a landfall and ask your guests how far away that headland is? They often say about a mile, when it's 4 miles. 0.7miles is and looks very close indeed, in open water when you're a plastic yoghurt pot and the other guy is 100,000 tonnes steel.
 
[ QUOTE ]
Ever done that thing where you approach a landfall and ask your guests how far away that headland is? They often say about a mile, when it's 4 miles.

[/ QUOTE ]

Funny you should mention this. I was thinking about the same thing yesterday when approaching Bembridge. A straw poll put a group of ships at anchor at less than a mile away whereas they were showing at 3 miles distant on the radar screen (and, indeed, proved to be that far away).
 
Does this count as one of my allowed ration of WNS posts, or will I get told off again? If it does, then I'm not saying anything.

If it doesn't, then I'd say that in open water I'd aim to cross at least 2 miles ahead with a CPA of at least a mile.

Darting across a narrow channel like Southampton Water, that might squeeze down to half a mile (except in the Exclusion zone, where I'd have to squeeze it up again to five ninths of a mile!)

In the WNS situation? Dunno. You didn't tell us what was behind those two ships. Maybe there was a whole procession of them, all following each other at 1.5 mile intervals.

I'm never very interested in how the WNS situations might have started: the fun bit is seeing how to get out of them. Plus, of course, I enjoy winding up people who think "You are doing 28 knots. How far do you go in six minutes?" is "a clever calcky thing!" /forums/images/graemlins/smile.gif
 
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