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Exile 28-10-2017 15:36

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Many thanks to Dockhead for starting & sticking with this and other Colregs-related threads that have been so helpful & educational. I have been impressed with your patience, purposefulness & restraint in keeping this thread on track despite significant challenges.

Please put me down for one of the first batch of your new book. An autographed copy is always nice. :wink: If nothing else, this and other threads have shown that there are many gaps in knowledge amongst recreational sailors, and so to that end a book directed specifically towards that market could fill a needed niche. :thumb:

Dockhead 28-10-2017 17:28

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by Exile (Post 2508114)
Many thanks to Dockhead for starting & sticking with this and other Colregs-related threads that have been so helpful & educational. I have been impressed with your patience, purposefulness & restraint in keeping this thread on track despite significant challenges.

Please put me down for one of the first batch of your new book. An autographed copy is always nice. :wink: If nothing else, this and other threads have shown that there are many gaps in knowledge amongst recreational sailors, and so to that end a book directed specifically towards that market could fill a needed niche. :thumb:

Thanks for the kind words! You'll have your copy.

Yes, there seems to be a total lack of any comprehensive resource on this subject. It wasn't my idea at all -- the publisher figured it out. I'm just the fool who agreed to do the work (despite having a more than full time day job :banghead:).

It's been a great discussion, and I guess I learned more than anyone. I'm sorry if anyone was offended by anything. I'm especially grateful to the pros who weighed in -- Lodesman and TJ -- and to our mathematician Juho. And special thanks to Rod, who by challenging ideas with -- ahem -- vigor, that the rest of us just take for granted, has forced us to think these through in ways we otherwise never would have. Who would have ever thought that someone would demand proof, that you can't approach a large ship moving at sea speed, closer than a certain distance? Taking stuff for granted is harmful to understanding; these kind of challenges are really useful.


Now that we've done to death the question of "Is there even such a thing as a safe CPA", maybe we can move on with the fascinating (to me, anyway) question of how the quality of information feeds into what makes a safe CPA. And also the quality of information coming from different sources -- especially naked eye data -- what can we perceive, from what distance? What do you say, guys?

evm1024 28-10-2017 19:13

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
1 Attachment(s)
Sign me up for a copy as well.

How about a chapter on crossings with vessels as the one in the photo? Perhaps a section on what they will do if you appear to be on a collision course with them.

I was still around 2-3 nm away and astounded that they let me get this close. The original CPA was less than 0.2 nm when they were over 5 miles out.

Stu Jackson 28-10-2017 21:21

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by Stu
...I would appreciate your observations on what I did "so terribly wrong" given my post which I thought explained it, and why he was long gone by the time I "got there."

Quote:

Originally Posted by ramblinrod (Post 2507913)
Already answered.

I would have had to see it, to understand what you did so terribly wrong.

It is at best disquieting to have you tell me I did something "terribly wrong," and then, when asked why, to tell me you had to be there.

Can you not see the inherent lack of coherence in your response to my simple question? It included a detailed explanation of what happened and what my analysis was. Post #671 page 17

Dockhead,

Thanks again for this. I look forward to learning more. I shared the salient points of this with a friend I've been cruising with this past week, about an hour before he saw his own "fast ferry" in these same waters. He "got it," right away.

You might want to start a new thread with a link back to this one, kinda like how you started this one.

ramblinrod 28-10-2017 21:38

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by Stu Jackson (Post 2508367)
It is at best disquieting to have you tell me I did something "terribly wrong," and then, when asked why, to tell me you had to be there.

If you were trying to put your boat near another, and you didn't get it anywhere near where you were trying, you obviously did something wrong.

What did you do wrong?

I have no idea, how the heck could I know, I wasn't there to see what you did wrong.

Maybe your range to the ship was wrong, maybe your bearing was wrong, maybe your speed was wrong, maybe your heading was wrong; how the heck could I know?

If I was there to see it, I could probably tell you what you did wrong, but I wasn't, so I can't.

Sheesh.

ramblinrod 28-10-2017 23:02

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by Stu Jackson (Post 2506633)
I, too, am surprised by Rod's lack of answer as to whether or not he has ever tried this, dead conning crew on the ship or not! :facepalm:

Well, not in broad daylight, but here's a shot of an iron ore ship we crossed during the LO300 (race around the little puddle known as Lake Ontario).

https://www.cruisersforum.com/forums...cture28154.jpg

He was doing 18 knots est. (I didnt have AIS or Radar).

(PS, he never moved an inch, just maintained their course and speed from horizon to horizon along the normal shipping route.)

IIRC we had 5 close encounters with ships during that race, all of which were between one quarter to 2 nm.

We sail in close quarters all the time in the St. Lawrence.

https://www.cruisersforum.com/forums...cture28153.jpg

Here there are bends, and shoals, and narrows, and all kinds of tricky things to navigate while dodging ships.

Open water...piece of cake compared to this chaos.

Just hang outside Alexandria Bay in August during Bill Johnstons Pirate Days, when a Laker goes through. Fun. They just kinda push the little rafted power boats out of the way with their bow wave. No biggy.

https://www.cruisersforum.com/forums...cture28152.jpg

Juho 29-10-2017 00:32

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by ramblinrod (Post 2508368)
If you were trying to put your boat near another, and you didn't get it anywhere near where you were trying, you obviously did something wrong.

What did you do wrong?

I have no idea, how the heck could I know, I wasn't there to see what you did wrong.

Maybe your range to the ship was wrong, maybe your bearing was wrong, maybe your speed was wrong, maybe your heading was wrong; how the heck could I know?

If I was there to see it, I could probably tell you what you did wrong, but I wasn't, so I can't.

Sheesh.

We don't have record of the course and speed history of the vessels, so it is hard to tell exactly what went right and wrong, or how close to each others the vessels could have crossed. But based of the description of the crossing, it seems that one contributing factor was unwillingness to confuse and cause distress to the other vessel. I'm not sure if this action should be called "wrong". Maybe better "right".

It is possible that he could have taken a more aggressive course, pointing in front of the bow of the ferry, and thereby getting closer or even hitting the ferry. But he decided to follow the spirit of the colregs, and keep his course such that the other vessel would understand that his intention was to cross behind the ferry, not in front of it, and not with a course that would carry with it a risk of collision, or what would seem to the captain of the other vessel as a course that might aim at collision.

TeddyDiver 29-10-2017 00:45

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by ramblinrod (Post 2508378)
Here there are bends, and shoals, and narrows, and all kinds of tricky things to navigate while dodging ships.

Open water...piece of cake compared to this chaos.

Fair point, but don't expect to be a master of the ocean with that experience. In confined channels it's impossible for large vessels to navigate freely so their behaviour is foreseeable (as said earlier by others). Looks like chaos but ain't so.. IMHO

Dockhead 29-10-2017 04:00

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by TeddyDiver (Post 2508399)
Fair point, but don't expect to be a master of the ocean with that experience. In confined channels it's impossible for large vessels to navigate freely so their behaviour is foreseeable (as said earlier by others). Looks like chaos but ain't so.. IMHO

Collision avoidance in pilotage waters is a completely different activity, from doing it in the open sea. Completely different problems and techniques.

What works in crowded pilotage waters -- which is vastly simpler -- is completely inapplicable to open water situations.

carstenb 29-10-2017 07:04

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by Dockhead (Post 2508222)
Now that we've done to death the question of "Is there even such a thing as a safe CPA", maybe we can move on with the fascinating (to me, anyway) question of how the quality of information feeds into what makes a safe CPA. And also the quality of information coming from different sources -- especially naked eye data -- what can we perceive, from what distance? What do you say, guys?

Well Dockhead, my ships library obviously would not be complete without an autographed copy - you write something personal to me like "To Carsten the best sailor since Cook" or similar. Modesty forbids me to tell you what to write though....... But I definitely want a copy

On a more serious note. Informaton quality is in crossing situations (as in virtually any other situation) - vital.

Our has has AIS, naked eye, and furuno radar. Generally we only use AIS and eyeball (the radar is only turned on when foggy).

Since we do not have the famed "pucker factor" that others do - we never let a crossing situation develop that could give us brown shorts. in open water, when we spot a ships (AIS), we simply make our course corrections far enough out that we maintain at least 1nm distance. If for some reason we are unsure of the others intentions, we call them on the VHF (never had one not respond) and reach an agreement on who's doing what to maintain the 1 nm.

Since we (in open water) never get close enough for "pucker factor" to kick in - AIS has more than enough accuracy for us.

In closed water situations, this is different though and we've had situations where larger boats (large but less than 300 tons) didn't have AIS and here the situation is entirely different. We virtually always call on the VHF but have experienced a number of times without response. Radar is invaluable here.

I suspect most would echo our experience or am I dreaming?

conachair 29-10-2017 07:12

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by carstenb (Post 2508551)
Our has has AIS, naked eye, and furuno radar. Generally we only use AIS and eyeball (the radar is only turned on when foggy).

Since we do not have the famed "pucker factor" that others do - we never let a crossing situation develop that could give us brown shorts. in open water, when we spot a ships (AIS), we simply make our course corrections far enough out that we maintain at least 1nm distance. If for some reason we are unsure of the others intentions, we call them on the VHF (never had one not respond) and reach an agreement on who's doing what to maintain the 1 nm.

Since we (in open water) never get close enough for "pucker factor" to kick in - AIS has more than enough accuracy for us.

In closed water situations, this is different though and we've had situations where larger boats (large but less than 300 tons) didn't have AIS and here the situation is entirely different. We virtually always call on the VHF but have experienced a number of times without response. Radar is invaluable here.

I suspect most would echo our experience or am I dreaming?

Echo!
Quite often no action required even in the busy channel a ship will have manoeuvred a long way away to give a 1Nm CPA. Or more mid ocean.

Almost echo, VHF rarely gets used to transmit.

Dockhead 29-10-2017 07:44

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by carstenb (Post 2508551)
Well Dockhead, my ships library obviously would not be complete without an autographed copy - you write something personal to me like "To Carsten the best sailor since Cook" or similar. Modesty forbids me to tell you what to write though....... But I definitely want a copy

On a more serious note. Informaton quality is in crossing situations (as in virtually any other situation) - vital.

Our has has AIS, naked eye, and furuno radar. Generally we only use AIS and eyeball (the radar is only turned on when foggy).

Since we do not have the famed "pucker factor" that others do - we never let a crossing situation develop that could give us brown shorts. in open water, when we spot a ships (AIS), we simply make our course corrections far enough out that we maintain at least 1nm distance. If for some reason we are unsure of the others intentions, we call them on the VHF (never had one not respond) and reach an agreement on who's doing what to maintain the 1 nm.

Since we (in open water) never get close enough for "pucker factor" to kick in - AIS has more than enough accuracy for us.

In closed water situations, this is different though and we've had situations where larger boats (large but less than 300 tons) didn't have AIS and here the situation is entirely different. We virtually always call on the VHF but have experienced a number of times without response. Radar is invaluable here.

I suspect most would echo our experience or am I dreaming?

Of course. All experienced blue water sailors do it just like this.

Heavy traffic in open water is rare enough, that you are normally not forced to get into close (for anyone who doesn't know what "close" is in blue water -- I mean less than a couple of miles) crossing situations. But to avoid ending up in one by accident, you have to analyze and deal with targets systematically, from a safe distance, and take early and decisive action as the Rules require. If you do get into heavy traffic in open water, the work can become very complex -- the special skills we have been discussing.

In pilotage waters the job is totally different. You know where the ship will be, and you know and can see what piece of water to stay out of. No matter how crowded it is, it's a no-brainer compared to a complex open water situations.

Dockhead 29-10-2017 07:48

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by conachair (Post 2508553)
Or more mid ocean. .

Yes, it's important to remember that a 1 mile CPA is a small CPA for open water, considered tolerable only in busy areas. There are incident reports on CHIRP where one vessel filed a formal complaint against another for passing less than 2 miles from another (but more than 1), refusing to give more room.

Not just mid ocean, but anywhere without so much traffic that maintaining 2 miles everywhere becomes impractical.

robbievardon 29-10-2017 08:06

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Dh I don't understand the waffle that you did not write the post I quoted 576. You then go on to justify your remark and fail to advise/respond to my question as to why you repeated your incorrect statement in the first place.
Following my question regarding visual distance to the horizon+ extension to Bridge, one would assume that the Merchant ship regardless of electronics would see and follow the track of the sailboat,judge it to be stand on and make an obvious change of course as required by Cregs. well in advance of any risk of collision. Assuming sailboat is approaching port side of vessel, I would anticipate a turn to port. There then would be no requirement for the sailboat to change course. In the posts 518,520 videos of a,collision and b, near miss, I would like to hear your views and the exact actions you believe all the captains should have taken and this question is open to all to respond to.
I am in the Gulf at the moment, but do keep a sailboat (37 foot) on Lake Ontario to use when I come up to visit Relatives, so I am familiar with "Lake Sailing" and it is by no means a walk in the Park. Conditions can change very quickly and have sent a lot of Lakers to the bottom along with entire crews and I am talking about steel ships under power.

robbievardon 29-10-2017 08:15

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
I forgot to mention that in court hearing regarding collision in gulf it was stated that one Captain had sufficient time to make an International phone call to advise the owners that "He was going to be in a collision" So much for the highly manoeuvrable cargo ships? I read about!!


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