Crossing Vessels

[fisherman]

yes to the one nm range, it's what i relied on when beset by ships, I became very attentive if a ship got inside a mile.
The advantage of you turning to port is it immediately makes him give way as overtaking vessel, and reduces the closing speed. As you carry on turning he remains give way and it gives you more options if he misbehaves. A complete 360 of sufficiently large radius places you astern and safe.
If you were in a ship rather than a boat you would have to.

 

[mainsail1]

Presumably thought if CPA >1 mile then noone needs make a course change ?

We are talking about collision or near miss avoidance here. If your CPA remains at more than 1/4 of a mile (or about 3 cables) I would not expect action to be taken by a small boat in good visibility although it would be helpful for you to alter to pass a bit further away.

 

[Yealm]

So would this an accurate summing up (eg if crossing TSS) ?

1) A long way apart - either vessel can change course to keep CPA >1nm
2) Getting closer - Colregs applies so only one vessel should be changing course if necessary
3) Very close - Colregs collision rules now apply !

And the distance that defines the change from (1) to (2) is mysterious and undefined

 

[GHA]

I love AIS. Actually observing a professional change course to give me a CPA>1 nm when I'm the stand-on vessel. Very comforting.
And I can do the same for him when I'm giving way.

?
Seem in the channel quite a few times, ship many miles away will tweak its' course to give almost exactly 1nm cpa. Really good idea to stand on as the ship will be doing the same for many vessels you don't even know exist..

Way offshore often they do course changes before they appear over the horizon.

Having a good radar return is a really good idea, even with ais transmitting.

 

[GHA]

So would this an accurate summing up (eg if crossing TSS) ?

1) A long way apart - either vessel can change course to keep CPA >1nm
2) Getting closer - Colregs applies so only one vessel should be changing course if necessary
3) Very close - Colregs collision rules now apply !

And the distance that defines the change from (1) to (2) is mysterious and undefined

Rule 8 >
Rule 8
The action taken should allow sufficient sea room for the safe passage of the other vessel. You are required not to impede the passage or safe passage of another vessel

(f)

(i) A vessel which, by any of these Rules, is required not to impede the passage or safe passage of another vessel shall, when required by the circumstances of the case, take early action to allow sufficient sea room for the safe passage of the other vessel.

?

Everything you need is in the irpcs, read and comply And they say don't comply if it's a stupid thing to do


Just came across some more youtube....

 

[mainsail1]

So would this an accurate summing up (eg if crossing TSS) ?

1) A long way apart - either vessel can change course to keep CPA >1nm
2) Getting closer - Colregs applies so only one vessel should be changing course if necessary
3) Very close - Colregs collision rules now apply !

And the distance that defines the change from (1) to (2) is mysterious and undefined

So would this an accurate summing up (eg if crossing TSS) ?

1) A long way apart - either vessel can change course to keep CPA >1nm
2) Getting closer - Colregs applies so only one vessel should be changing course if necessary
3) Very close - Colregs collision rules now apply !

And the distance that defines the change from (1) to (2) is mysterious and undefined

This is too simplistic. Seamanship is learned with experience. No two cases are the same because there are variable factors such as the weather, size of vessels, speed of vessels, types of vessels etc. If you stick to the basic rule that if you are give way vessel and there is a risk of collision you need to give way in good time with a bold alteration of course (so that there are no misunderstandings). To begin with, any vessel with a CPA of less than 1 mile is a risk but you can refine that as you gain more experience.

 

[johnalison]

In my experience, a single ship seldom gives cause for concern, but it is when there are two vessels, maybe from different directions and at different speeds, that difficulties arise. This is possibly where AIS comes in most useful, but, as m1 says, facility only comes with experience.

 

[GHA]

If you stick to the basic rule that if you are give way vessel and there is a risk of collision you need to give way in good time with a bold alteration of course

?
You sound like you may have spent some time on the bridge of big ships - if so what distance would you start getting a bit concerned in open water/shipping lanes if a risk of collision existed and the a give way yacht did nothing? Usually think I'd be doing something obvious at about 2 or 3 Nm off, even if it was a big course change for a couple minutes then back a little just to hopefully make it clear that to the ship that it's been seen and shouldn't need to do anything.

 

[Buck Turgidson]

CPA > 1nm is very cautious in my mind, especially If you are crossing a busy shipping lane. I'm interested at 1nm CPA, I'm active if it less than 1/2 nm.

 

[mainsail1]

?
You sound like you may have spent some time on the bridge of big ships - if so what distance would you start getting a bit concerned in open water/shipping lanes if a risk of collision existed and the a give way yacht did nothing? Usually think I'd be doing something obvious at about 2 or 3 Nm off, even if it was a big course change for a couple minutes then back a little just to hopefully make it clear that to the ship that it's been seen and shouldn't need to do anything.

Would start thinking of action at 1mile but does depend on closing speed and all kinds of other factors.

 

[GHA]

Would start thinking of action at 1mile but does depend on closing speed and all kinds of other factors.

So on a ship you wouldn't do anything 'til under 1Nm???
That's bit odd, often in the channel the ships will take action many miles away and the cpa will stay very close to 1Nm.

 

[GHA]

CPA > 1nm is very cautious in my mind, especially If you are crossing a busy shipping lane. I'm interested at 1nm CPA, I'm active if it less than 1/2 nm.

Steering a ship? That was the question.

1Nm in open water isn't very close.

 

[johnalison]

Although I might be happy to pass a few cables astern of a ship, I would be less happy if it were fast-moving and its wake likely to be a problem. On the other hand, I might have a mental image of leaving a mile clearance, but in practice seeing a ship pass half a mile or less ahead or astern does happen occasionally and I don't remember being concerned about it.

 

[TernVI]

The problem is often that a yacht's course and speed varies and the calculated CPA may change a lot.
A smaller CPA is acceptable if you are clearly going to go behind the ship.
Committing to passing more than 2 miles in front of something can get nervy when the wind drops or shifts.

 

[GHA]

No one seems to care what the guys driving the ships think, no wonder they call us wafis.....

 

[TernVI]

Although I might be happy to pass a few cables astern of a ship, I would be less happy if it were fast-moving and its wake likely to be a problem. On the other hand, I might have a mental image of leaving a mile clearance, but in practice seeing a ship pass half a mile or less ahead or astern does happen occasionally and I don't remember being concerned about it.

A ship which passes half a mile dead astern of a slow yacht is not as much of a risk as yacht being a mile dead ahead of the ship.
You can be 50ft from a ship alongside it and there's no way it can hit you. If you are passing in front of it and lose power, how much time does the ship have to react?
Margin for error is not equal in all directions as the yacht can alter course or speed very quickly, the only thing it cannot do is outpace the ship.
I can't immediately express this clearly but CPA is not a very good measure of the margin for error between a slow yacht which can turn in its own length and a faster ship with a limited rate of turn and acceleration/deceleration.

Also when your AIS computer calculates the CPA, there is a lot of uncertainty to be added into the yacht's course and rather less in the course of the ship.
The big advantage of AIS is seeing the ship's COG change before it's visually obvious.

I might be thinking there's a risk of collision, while he knows he's turning into LeHavre.....

 

[mainsail1]

So on a ship you wouldn't do anything 'til under 1Nm???
That's bit odd, often in the channel the ships will take action many miles away and the cpa will stay very close to 1Nm.

Remember I am on the stand on vessel.

 

[GHA]

Remember I am on the stand on vessel.

So when would you get nervous? That was the question.
You'd really do nothing 'til 1Nm, 3 or 4 minutes before hitting??
Thank goodness for ais

 

[mainsail1]

Yes, I am on the stand on vessel. I would have been monitoring the muppet vessel for some miles but it is his job to alter course. I would have devised a plan of action if he fails to do anything.

 

[Buck Turgidson]

When you have this:


followed by this:


for the good part of 6 hours. 1nm CPA would have you never crossing. This was off the Portuguese coast south of Lisbon outside the TSS.

sorry about the quality of this one, it's a video screen grab but you get the picture!