Thread for Basic COLREGS Questions

[Lodesman]

Originally Posted by four winds

I watched the over the horizon glow of a ship divert from a constant bearing after watching it for some time. She altered to pass at what appeared to be two miles.

If CPA is relatively close (like 2 miles) then the bearing change over the horizon, far away enough to be just a glow, is very slow and would appear stationary.

[four winds]

Well it did appear stationary for quite some time, don't know exactly how long. And then appeared to change bearing. But I get your point. Maybe I couldn't detect the bearing accurately so far away.

She was to starboard. And stand on if power to power.

But I was sailing. IF she gave way how did the captain determine this so far away?

Again, as to the quote I mentioned, do any big ships change course before COLREGS applies for all small vessels with weak radar returns?

Forgive my ignorance.

[StuM]

Originally Posted by four winds

Well it did appear stationary for quite some time, don't know exactly how long. And then appeared to change bearing. But I get your point. Maybe I couldn't detect the bearing accurately so far away.

She was to starboard. And stand on if power to power.

But I was sailing. IF she gave way how did the captain determine this so far away?

Again, as to the quote I mentioned, do any big ships change course before COLREGS applies for all small vessels with weak radar returns?

Forgive my ignorance.

Many big ships will change course "before risk of collision" is reached (i.e. before COLREGs apply) for both large and small vessels.so as to ensure a safe crossing with a large CPA. At that stage it's not a question of "give way", it's a question of prudent navigation.

[Dockhead]

Originally Posted by four winds

Well it did appear stationary for quite some time, don't know exactly how long. And then appeared to change bearing. But I get your point. Maybe I couldn't detect the bearing accurately so far away.

She was to starboard. And stand on if power to power.

But I was sailing. IF she gave way how did the captain determine this so far away?

Again, as to the quote I mentioned, do any big ships change course before COLREGS applies for all small vessels with weak radar returns?

Forgive my ignorance.

"Forgive my ignorance?"

Are you kidding? This is a really, really intelligent question.

Why do so few people wonder about what goes on, on the bridge of ships? About WHEN they make what decisions, to do what?

I interviewed a bunch of professional mariners to try to figure out the answer to this question.

The answer is -- yes, they do maneuver far ahead of time, when possible! No one who really understands collision avoidance likes standing on -- it's the passive role; you are giving control of the crossing to the other vessel. Commercial mariners absolutely do not trust us to know how to behave -- and for good reason, as we see here over and over again. Many of them call us "WAFIs" -- Wind Assisted F**** Idiots -- and have a very low opinion of our seamanship and, especially, of our understanding of collision avoidance. They consider that whatever maneuver we make is usually wrong, and they try wherever possible to avoid getting into a risk of collision situation with us in the first place. 10 miles in open, uncrowded water is a common decision point for them (many of them are trained to have plotted all potential targets by that point), and at that range no one is obligated to stand on. So they don't care whether we are under sail or not -- they like to get themselves into a position where no stupid thing we do, can create danger, and they are free to do that at that kind of distance.

Their main complaint about our maneuvering is that we do it erratically and unpredictably, that we do it too late, and that we fail to stand on when we are required to. They also complain that we fail to keep a lookout behind, and that we sail in channels and fairways when we don't need to, creating unnecessary problems.

[Lodesman]

Originally Posted by four winds

But I was sailing. IF she gave way how did the captain determine this so far away?

I agree with Dockhead, it's a good question. A small radar target at distance, that is not yet visually identified, if shown by ARPA to be stationary or moving slowly, would normally be assumed to be something that should be avoided - maybe a sailboat, or a small fishing boat, or even net markers. Changing course by a few degrees many miles off is a cheap and easy solution to avoid potential problems. I can't speak for every watchkeeper, but I would tend to make such a manoeuvre within the visual horizon - say 6-8 NM. At that range, might not see a net marker, but a sailboat can be seen, given daytime good vis.

[Exile]

On one of these Colregs threads going right now I recall Stu quoting a Cockcroft passage to the effect that "nobody would claim that 6nm was close enough for the Rules to apply." Definitely not an exact quote but suggests that 6nm is still well beyond the distance for a "potential" risk of collision & thus the stand on rule to kick in. Doesn't really matter for our boats (if under sail) since we should be maintaining course & speed either way, until it appears the give way vessel is not maneuvering that is and an "actual" risk of collision has presented itself.

The Rules deliberately (and appropriately) don't delineate specific distances for when a stand on vessel faced with an actual risk of collision should begin her own maneuvers. But assuming open water, is it prudent to assume that 1nm is an absolute red line? I'm basing this on previous comments about big shipping making 1nm a "wake the captain" limit, along with Dockhead's comments about the speed differential rendering our small vessels potential sitting ducks regardless of attempts at maneuvers.

Again assuming open water (too many variables otherwise), there is that somewhat unmeasurable point where maneuvering too early can screw up the give way vessel's plan, and maneuvering too late can be dangerous. I suspect the vast majority of recreational vessels maneuver far too early. Thoughts?

[Dockhead]

Originally Posted by Exile

On one of these Colregs threads going right now I recall Stu quoting a Cockcroft passage to the effect that "nobody would claim that 6nm was close enough for the Rules to apply." Definitely not an exact quote but suggests that 6nm is still well beyond the distance for a "potential" risk of collision & thus the stand on rule to kick in. Doesn't really matter for our boats (if under sail) since we should be maintaining course & speed either way, until it appears the give way vessel is not maneuvering that is and an "actual" risk of collision has presented itself.

The Rules deliberately (and appropriately) don't delineate specific distances for when a stand on vessel faced with an actual risk of collision should begin her own maneuvers. But assuming open water, is it prudent to assume that 1nm is an absolute red line? I'm basing this on previous comments about big shipping making 1nm a "wake the captain" limit, along with Dockhead's comments about the speed differential rendering our small vessels potential sitting ducks regardless of attempts at maneuvers.

Again assuming open water (too many variables otherwise), there is that somewhat unmeasurable point where maneuvering too early can screw up the give way vessel's plan, and maneuvering too late can be dangerous. I suspect the vast majority of recreational vessels maneuver far too early. Thoughts?

Excellent questions.

In my opinion, 1 mile in open water when dealing with a ship at sea speed is far too late. I would like to have a CPA of at least one mile if at all possible. When there is a big difference in speed, your options disappear with breathtaking rapidity. I will usually maneuver at 3 or even 4 miles if the CPA is still uncomfortable by then.

[Exile]

Originally Posted by Dockhead

Excellent questions.

In my opinion, 1 mile in open water when dealing with a ship at sea speed is far too late. I would like to have a CPA of at least one mile if at all possible. When there is a big difference in speed, your options disappear with breathtaking rapidity. I will usually maneuver at 3 or even 4 miles if the CPA is still uncomfortable by then.

I think I would too, and probably do. Even at the risk of making me a WAFI in the eyes of the big ship watch crew. If nothing else I'll be paying a lot more attention to these distances the next time I'm out there. It's a judgment call and can only come with a combo of studying the Rules and experience on the water I'm sure.

[StuM]

Originally Posted by Exile

On one of these Colregs threads going right now I recall Stu quoting a Cockcroft passage to the effect that "nobody would claim that 6nm was close enough for the Rules to apply." Definitely not an exact quote but suggests that 6nm is still well beyond the distance for a "potential" risk of collision & thus the stand on rule to kick in.

Mea Culpa!

Unfortunately, that was a short quote to illustrate a particular point about when "risk of collision" occurs, Those words could be misleading. The subsequent section is important.

The above case was heard in the last century when ships were relatively slow. The two vessels concerned were involved in an overtaking situation in Dublin Bay, their speeds being respectively 6 and 7 knots. The distance at which risk of collision begins to apply might well be considered to be greater than 6 miles between vessels approaching one another at high speeds, in the open sea, on reciprocal or nearly reciprocal courses. The distance must depend very much on circumstances and particularly on the speed of approach. In rivers and harbours where vessels frequently have to change course risk of collision may only be considered to apply at relatively short distances.

[Exile]

Originally Posted by StuM

Mea Culpa!

Unfortunately, that was a short quote to illustrate a particular point about when "risk of collision" occurs, Those words could be misleading. The subsequent section is important.

The above case was heard in the last century when ships were relatively slow. The two vessels concerned were involved in an overtaking situation in Dublin Bay, their speeds being respectively 6 and 7 knots. The distance at which risk of collision begins to apply might well be considered to be greater than 6 miles between vessels approaching one another at high speeds, in the open sea, on reciprocal or nearly reciprocal courses. The distance must depend very much on circumstances and particularly on the speed of approach. In rivers and harbours where vessels frequently have to change course risk of collision may only be considered to apply at relatively short distances.

AH HAH! Not only does this context now explain the comment, but is also more congruous with Dockhead's recommendations about appropriate distances for when the Rules are triggered in open water.

[Lodesman]

Originally Posted by Exile

But assuming open water, is it prudent to assume that 1nm is an absolute red line?

As a rule of thumb, I'd use 2nm for a slower merchant; if it's going 3-times my speed or faster, I'd bump it out to 3nm.
I wouldn't flinch at a 1/2-mile passing, daytime good vis; and would be ok with a couple cables if we had talked by vhf. Night or fog, and I'd want a mile between us.

[Dockhead]

Originally Posted by Exile

I think I would too, and probably do. Even at the risk of making me a WAFI in the eyes of the big ship watch crew. If nothing else I'll be paying a lot more attention to these distances the next time I'm out there. It's a judgment call and can only come with a combo of studying the Rules and experience on the water I'm sure.

I think anything which makes you look like a WAFI in front of the pros, is going to be something which is not safe. Predictability is a key element of safe collision avoidance.

As you say, it's a judgment call -- the bigger difference in speed and the further from traffic, the earlier you can/should take action, in my opinion.

I think the main thing to understand in deciding to take action yourself, when you're the stand-on vessel, is when HE is going to make his move. Remember the only purpose of standing-on is to give him the chance to take control of the crossing, so you need to have some objective reason to believe that he will not take action, before you take action yourself. 4 miles is not too late for him to take action, in most cases, so that's pushing the envelope for taking matters into your own hand. I will do it at that distance only if there is really no reason in the world, that I can perceive, why he would have waited until then. Based on a lot of observation (I've done crossings with more than 100 ships just in the last couple of weeks), and interviews with pro mariners, I believe that in open water and light traffic, most ships will take action before 4 miles out, and normally it will be more like 6 to 8 miles out. Unless they have to deal with other traffic first, or in case they are about to make a turn for some other reason, 3 miles out is about the last moment you can imagine they would do something. Maybe Lodesman or some of the other pros on here would weigh in on this, as it's a really important question for us.

In heavy traffic, this all becomes vastly more complex, and sometimes you have to guess as to what he's doing -- maybe you're in line to be avoided after x and y other vessels, and so he needs to leave you until later, and maybe he really, really needs for you to keep standing on in the mean time. A VHF call can clear up this kind of question, but in heavy traffic you are doubly loathe to distract the busy watchstander with a call. So there's a lot of judgement involved, and experience really helps a lot.

The other thing which helps enormously is either radar plotting training, or at least a really good AIS display like OpenCPN, so you can visualize several crossings at once.

[Dockhead]

Originally Posted by Lodesman

If CPA is relatively close (like 2 miles) then the bearing change over the horizon, far away enough to be just a glow, is very slow and would appear stationary.

Indeed. One should know the limitations of the sight-across-a-stanchion method -- you cannot distinguish a 0.0 CPA from a 2 mile CPA with your naked eyes, from a few miles away. It's harmful to jump to conclusions based on data whose inaccuracy you don't understand, and make a sudden maneuver which has an approximately 50% chance of making the crossing worse, including making a perfectly safe pass, already set up by the other vessel, into a renewed collision course.

[Lodesman]

Originally Posted by Dockhead

Maybe Lodesman or some of the other pros on here would weigh in on this, as it's a really important question for us.

You have summed it up pretty well. The only thing I would add, is that there is a tendency with junior watchkeepers to carry on to a fairly close distance before they take the required avoiding action. What I mean is that even if a risk of collision is determined and they understand themselves to be the give-way at 6nm, they will choose to close to 2nm monitoring the situation, before altering boldly to starboard. I don't know why this is; I think it may be a product of knowing the rules by rote, but not yet having developed a full understanding of them. Of course my experience is Navy, so I don't know that this isn't just a navyism, but my gut tells me from interacting with many merchant vessels, that this behaviour is also common amongst "third world" watchkeepers. Maybe a marine institute grad or someone from the commercial side could chime in.

[nigel1]

Deep sea, I want the OOW to be taking action at a minimum of 4 miles out.
As I explain it to them, if the boot is on the other foot, and they are stand on, at 2 miles range, they would be twitching if the give way vessel was yet to take action.

I have witnessed other merchant vessels pushing the limits, I got the impression that they were hoping that the stand on vessel would take avoiding action.

With ECDIS now being the norm, there is a tendency for junior OOW to stick rigidly to the electonic track.