Collision Avoidance, Cones of Uncertainty, and Appropriate CPA

[ramblinrod]

Originally Posted by Quebramar

I wonder why some comments that were quite denigrating I would say, also came from people who justify their less attentive attitude (no judgment) by pressing to relax and take it easy.

Cant speak for everyone, but I believe that in an internet forum, it is important for those with a different opinion to speak up, otherwise, followers may get a false sense of fact or conscensus.

It is clear, that in this group, I seem to be in the minority, believing that a minimum CPA of 1 nm is not necessary in all circumstances (which was the thrust of my initial post that seem to lead to what in the most part has been total nonsense due to the continued use of strawman arguments).

I suspect that many have not spoken up in support of a similar position, for fear of being exposed to attempts to publically ridicule, chastise, or humiliate.

I tend to stand up for what I believe is right and don't back down in the face of bullying tactics, so have persisted quite vociferously.

I object to the suggestion that my attitude toward collision avoidance is any less attentive.

While one has their head in their electronics, wasting several minutes to analyse a situation to death, and calculate a plan, based on totally arbitrary and unnecessary minimum CPA values (where that delay may have intensified the situation because as we discussed an I believe all clearly agreed, the longer one waits, the greater the risk) I have probably already taken action long ago.

My point is, that there is always more than one way to skin a cat, and "one way" is not necessarily the best way, under all circumstances.

It is good for there to be rules and a chain of command on every vessel.

Adhering to Colregs, should be part of those rules. How the vessel is operated in compliance to Colregs is at the discretion of the chain of command on that vessel. On our vessel, that means how I and my wife have agreed to address. Period! Nobody else, without any authority has any right to dictate (or attempt to dictate) how we operate our vessel.

I prefer to live in a society where one individual without any authority whatsoever does not dictate "rules" beyond those that have been accepted by democratic means.

Colregs are the rules established by a democratic process. 1 nm minimum CPA in all circumstances is not.

That simple.

[Exile]

Originally Posted by Dockhead

All this seems entirely reasonable to me.

A small comment to the question about size --

Probably doesn't make a difference if you're maintaining reasonable CPA's, not measured in fractions of cables. But at some point, the size of the ship affects how hard it is to get out of its way. A bigger ship covers a bigger piece of ocean. If you find yourself on an actual 0 CPA from its bow (something you can't measure precisely, but imagine you blunder into such a position), you have further to go, to get out of his way. To travel this further distance from danger to safety, you need to maneuver earlier.

Good point, and not something I've had to deal with in my relatively low-intensity encounters with ship traffic, especially compared to the busy waters you often sail in.

And fwiw, this is a factor expressly laid out in the Rules as you've already highlighted:

Originally Posted by Dockhead

Rule 7
Risk of collision

* * *

(d). In determining if risk of collision exists the following considerations shall be among those taken into account:

(i). such risk shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change;

(ii). such risk may sometimes exist even when an appreciable bearing change is evident, particularly when approaching a very large vessel or a tow or [COLOR="rgb(139, 0, 0)"]when approaching a vessel at close range[/COLOR].

And as Ping recently alluded to, speed can be a factor when encounters get close since a large, fast moving ship may present similar circumstances as a smaller ship moving slower. Good info to take into account as I have thus far not had a scenario where another vessel or mine haven't had the opportunity to maneuver well before these factors are in play.

[Kenomac]

Originally Posted by Quebramar

Just a comment. If not sharing the same interest one can just move on and skip the specific thread, letting others continue enjoying the thinking.

Sorry, but that's not the way an internet discussion works. You can sometimes be joined by people who disagree.

Oh the horror.....

[Paul Elliott]

Rod, didn't you observe, *many* posts back and possibly in a different thread, that a one-degree course change may be an appropriate reaction in a close crossing situation, and that a miss by mere inches was all that was required by COLREGs? If that wasn't you then I apologize, but you do seem to be continuing to defend and explain this point of view.

[Dockhead]

Originally Posted by ramblinrod

Cant speak for everyone, but I believe that in an internet forum, it is important for those with a different opinion to speak up, otherwise, followers may get a false sense of fact or conscensus.

It is clear, that in this group, I seem to be in the minority, believing that a minimum CPA of 1 nm is not necessary in all circumstances (which was the thrust of my initial post that seem to lead to what in the most part has been total nonsense due to the continued use of strawman arguments).

I suspect that many have not spoken up in support of a similar position, for fear of being exposed to attempts to publically ridicule, chastise, or humiliate.

I tend to stand up for what I believe is right and don't back down in the face of bullying tactics, so have persisted quite vociferously.

I object to the suggestion that my attitude toward collision avoidance is any less attentive.

While one has their head in their electronics, wasting several minutes to analyse a situation to death, and calculate a plan, based on totally arbitrary and unnecessary minimum CPA values (where that delay may have intensified the situation because as we discussed an I believe all clearly agreed, the longer one waits, the greater the risk) I have probably already taken action long ago.

My point is, that there is always more than one way to skin a cat, and "one way" is not necessarily the best way, under all circumstances.

It is good for there to be rules and a chain of command on every vessel.

Adhering to Colregs, should be part of those rules. How the vessel is operated in compliance to Colregs is at the discretion of the chain of command on that vessel. On our vessel, that means how I and my wife have agreed to address. Period! Nobody else, without any authority has any right to dictate (or attempt to dictate) how we operate our vessel.

I prefer to live in a society where one individual without any authority whatsoever does not dictate "rules" beyond those that have been accepted by democratic means.

Colregs are the rules established by a democratic process. 1 nm minimum CPA in all circumstances is not.

That simple.

I completely agree with, actually, all of this.

A vigorous discussion is the essence of what makes all this worthwhile. How useless would internet fora be if we all agreed with each other?

Even a completely wrong idea, energetically and intelligently defended, does a great service to everyone.

For the record, I also agree that a 1nm CPA is not necessary in every case, and I never said that. You don't need it in pilotage waters where you have other ways of knowing where the ship will be, and you don't need it with certain crossings, like, for example, an overtaking situation. You don't need it if your speeds are similar.

But I don't think Quebremar was talking about that. He can speak for himself, but I think he was talking about those posts which were of the form "You're talking about that? The whole subject is only interesting for anal compulsive geeks. Why worry about it? You are stupid to worry about it." As opposed to "You think you should do it like that? No, it should be done like that." Rod never argued the first thing. His posts have been very valuable, as a very good expression of a certain point of view, and I have enjoyed the discussion. They have helped me a lot with the work on my book.

[Quebramar]

Indeed. We can always agree to disagree and it forces to re-think some of what I sometimes took for granted. I did not want to judge anyone and think the internat is a great way to get more variety of opinions. I do enjoy constructive criticism any time also.

Got earlier today heading towards the entrance of the harbour and a speedy motorboat of the Customs was heading at me or very close. I asked my friend at the helm to stand on, there was no reason to change course and we stayed until they got around 250m. At 15kts they then made a quick turn to avoid us, then they continued and only slowed down at the entrance of the channel, causing strong waves towards a really small sailboat that was just leaving it. Not quite polite to say the least.
My take is, indeed distance was short and I was ready to go starboard if they had not changed course, but didn't have to do so. Distance and circumstances dictate, no doubt. And I'll continue to enjoy learning on what works and what doesn't, and why.

[ramblinrod]

Originally Posted by Dockhead

For the record, I also agree that a 1nm CPA is not necessary in every case, and I never said that.

Oh really?

Please let me draw your attention to your post...

Re: Collision Avoidance -- Dealing with Multiple Targets #101, 21-08-2017, 16:37

Where you clearly stated, with respect to maintaining distance from a ship...

"Less than one mile is dangerous, and a mile may be too close if passing ahead."

and...

"If you screw up and end up less than a mile from a ship at sea, you may even get the watchstander in trouble, not to mention the risk getting yourself killed."

Then in post # 151, 27-08-2017, 06:37

In open water, my definition of a "dangerous vessel" is usually 30 minutes TCPA and 1 mile CPA; in the middle of an empty piece of ocean far from land, maybe 2 or 3 miles.

*
So I guess I need to ask the question...

...At what point in this discussion did you change your position that one should keep a minimum CPA of 1 nm for all circumstances at sea, to the one which seems to be considerably different (and more in line with my position) that you are claiming is your position now?

[markpierce]

during my thirty years of boating experience in limited waters , i've never observed a commercial vessel avoiding a recreational vessel. as a result, I avoid all commercial vessels.

[Exile]

Originally Posted by markpierce

during my thirty years of boating experience in limited waters , i've never observed a commercial vessel avoiding a recreational vessel. as a result, I avoid all commercial vessels.

Depends on what you mean by "limited waters," but could very well be right in line with the Colregs. If the other vessels are in designated channels, restrained by draft, etc. If so then you have the obligation to give way.

[markpierce]

Large ships are limited in the SF Bay/Delta waters but the tugs either alone or towing/pushing a barge act the same without a nautical reason. Safest to avoid them all. ... Aren't we all just boys-on-toys in their eyes?

[Exile]

Originally Posted by ramblinrod

...At what point in this discussion did you change your position that one should keep a minimum CPA of 1 nm for all circumstances at sea, to the one which seems to be considerably different (and more in line with my position) that you are claiming is your position now?

Here are the examples DH just posted above:

For the record, I also agree that a 1nm CPA is not necessary in every case, and I never said that. You don't need it in pilotage waters where you have other ways of knowing where the ship will be, and you don't need it with certain crossings, like, for example, an overtaking situation. You don't need it if your speeds are similar.

So in DH's opinion, you don't necessarily "need" a 1nm CPA in (1) pilotage waters, (2) overtaking, (3) similar speeds, maybe others. If you want to avoid what you complain are "straw man" arguments (whatever those may be), then similarly provide examples where you believe it is safer to maneuver at 1nm CPA or less in the types of crossing scenarios you have been advocating (whatever they are). Or do you agree with DH that they are generally limited to the examples he just provided?

I understand your generalized comment that a closer in maneuver may be preferable so as not to interfere with a commercial ship's crossing plan, but by the time you're that close then isn't it safe to say that the ship has no plan and you're now in control? Obviously if you're stand on and the ship has not given way at that point, then the obligation falls on you. Colregs compliance or not, wouldn't it just make more sense to back the whole thing up and allow more time for both vessels to sort things out as needed? Or is this where "pucker factor" somehow plays a role in communicating intentions between vessels?? Obviously much depends on what type of crossing scenario is presented.

Rather than more straw man accusations, why not just present a specific factual scenario as others have done & explain why your approach is safer & more advantageous towards everyone's goal of avoiding collisions? Maybe it's a reading comprehension problem on my part, but if so it shouldn't be hard for you to clarify for me & maybe others who have repeatedly asked you questions which it doesn't appear you have answered.

Or maybe it's just your personal preference and, if so, then that's fine too, but I think it's now clear why merely the end result of your maneuver avoiding a collision doesn't necessarily equate with compliance. Fwiw, I don't think you need worry about anyone trying to actually restrict your freedom to sail your boat as you wish. It's only a harmless internet forum after all, where people are simply exchanging thoughts & ideas.

[Exile]

Originally Posted by markpierce

Large ships are limited in the SF Bay/Delta waters but the tugs either alone or towing/pushing a barge act the same without a nautical reason. Safest to avoid them all. ... Aren't we all just boys-on-toys in their eyes?

Don't know, but as I recall you are correct that tugs & tows don't have priority (if you will) over sailing vessels under sail (could be wrong). But I just remembered you are a power vessel. But either way, if the expectation -- right or wrong -- is that they won't be giving way for you then both common sense and the Rules support keeping out of their way! (Sounds analogous to the Chesapeake Bay watermen from another thread).

[markpierce]

Originally Posted by Exile

Depends on what you mean by "limited waters," but could very well be right in line with the Colregs. If the other vessels are in designated channels, restrained by draft, etc. If so then you have the obligation to give way.

Recognize large ships are restricted to navigable channels, but many commercial vessels are not. But I've observed it is best to avoid all commercial vessels regardless of the Colregs (won't press stand-on obligation in a potential collision situation). That tactic, as in taking early action, has worked well for me commanding both sail and motor vessels.

[Quebramar]

Originally Posted by markpierce

during my thirty years of boating experience in limited waters , i've never observed a commercial vessel avoiding a recreational vessel. as a result, I avoid all commercial vessels.

Not sure what limited waters means for you. In my case, crossing the TSS at SE England, I once was going to cross at 90deg with the gennaker and I saw one oil carrier at approx 6-8NM (not exactly sure, it was a while ago) with too close a CPA (less than 1NM) for my "comfort" shall I say, actually my personal safety rule. Conditions were very good, calm sea and good visibility.
I was the give way vessel and took the sock down on the genny and slowed down, couple of minutes later the ship had changed course 2-3deg resulting in a much better CPA and there went the sock up again. It did not cost much to the merchant ship as further down the shipway was turning in that direction so it merely anticipated that part, going quite a bit into the centre of the lane.
Skipper grateful of this gentleman's kind gesture in return to my precautionary one which, as I sense from some comments, some would consider as not being required.

[Exile]

Originally Posted by markpierce

Recognize large ships are restricted to navigable channels, but many commercial vessels are not. But I've observed it is best to avoid all commercial vessels regardless of the Colregs (won't press stand-on obligation in a potential collision situation). That tactic, as in taking early action, has worked well for me commanding both sail and motor vessels.

I do the same, and would like to think it's also compliant with the Rules since there are provisions which explicitly mandate taking whatever appropriate actions are necessary under the circumstances to avoid collision. (Someone will chime in with the Rule no. & actual text I'm sure ). In the Chesapeake, for ex., the tugs all seem to run down the west side of the Bay, perhaps to stay clear of fast moving freighters & tankers moving fast through the big ship channel. The tugs do so quite predictably and it seems accepted practice amongst recreational vessels (sail & motor) to stay well clear.