Collision course, radio and procedures

[poiu]

Originally Posted by Richard_W

It is an interesting real life case, and the discussion up to somewhere on page three where I got lost in conflicting arguments. I have a question or two, but first let me review, starting with the context:



The situation started developing some 30 minutes to CPA, and presumably 8 miles apart.



Seems that this was the time for the stand-on vessel to take action.



Myself, like Mark, came to the conclusion/question, why wait any longer?



Referring to the previous post, the 10 mile marker was already passed with no action taken by the give-way vessel.



My first question is … why wait? At the point when the OP's situation started developing, 30 minutes and 8 miles apart, it was the perfectly safe time for a stand-on vessel to take Colregs sanctioned action. Correct?

My second question is … if so, what would be wrong with making, then and there, a few degree course change (oh no, to port!?) to pass to stern of the give-way vessel?

With the benefit of hindsight I think probably the other boat did see me. I think he was happy passing two cables behind. The best action would have been to motorsail a bit to open up the distance as this would have been without risk. I could have equally reduced speed to maybe a couple of knots. This would have put him ahead of me and opened up the CPA to close to a mile. As I said before, I was not in danger here unless we got into a pavement dance, so slowing down would not have been without risk as he could have turned to stay behind me. Had the ship done nothing I could have stopped my boat even much later to give a safe separation distance again assuming he doesn't turn.

I had rather poor AIS equipment at the time (now upgraded). At 8 miles it wasn't clear there was a problem, just that there might be one. I couldn't do anything until I was sure what to do or I could well have made things worse, so after a while of monitoring the changing CPA and cross checking it with a EBL on the radar to be sure there was an issue, it became clear there was a situation at 15 minutes and 4 miles, so as to your question of why not maneuver at 8 miles, the question did not arise. It does make sense that it should be possible to detect a conflict at over 8 miles and with my upgraded equipment it should help me react earlier. Also an aural alarm needs to be fitted to improve things further.

As to why not make a few degrees course change - that would have been as good as nothing. Maybe if it was a very distant overtaking situation a small turn right by a few degrees would be perfect. I can see why you might do a small turn as a precaution at 8 miles in a head on situation, but it would need to be more like 5 to 10 degrees, but here the boat was coming at me perpendicular to my track from the right. At my desk and with time at hand I can estimate that I would have had to make about a 40 deg turn to port at 8 miles if I had known that was the right thing to do and about a 70 deg turn at 4 miles. A little less if I could have turned to starboard, (I couldn't do that because of the wind direction). This is why I said above the best option would have been to slow or stop the boat.

An interesting question is how to calculate the optimum avoidance turn. Turning not enough such as by only a few degrees as you suggested can in certain circumstances be as good as doing nothing and dangerous. Also, colregs require a clear and significant turn. I wonder if there have been collisions resulting from such errors. I can't remember seeing such a discussion.

[nigel1]

This might be a useful link for anyone trying to get a better understanding of the Colregs

http://www.google.co.uk/url?sa=t&rct...,d.ZGU&cad=rja


Problem with making small alterations is
1) Not easily detected by the other vessel.
2) If you make a series of small alterations, it can lead to change of bearing but the risk of collision remains.

Whats really bad is when both boats start making small alterations.

[rwidman]

Originally Posted by four winds

Amazing. Someone actually thinks the "Law of Gross Tonnage" might possibly actually be real.

I've always taken the "Big boats have the right of way." statements as a sure sign of naive inexperience.

Whatever dude. Yep, you are much smarter than me. You go ahead and challenge that giant freighter or cruise ship. Me, I'll just stay out of danger.

[rwidman]

Originally Posted by four winds

Amazing. Someone actually thinks the "Law of Gross Tonnage" might possibly actually be real.

I've always taken the "Big boats have the right of way." statements as a sure sign of naive inexperience.

Dude, I understand that you think you are right and I am wrong but why do you feel the need to phrase your post as a personal insult?

Are you trying to intimidate people who may disagree with you? Drive them away from the forum? Trying to be "king" of the forum?

You are not going to "educate" anyone with that sort of attitude. How about more understanding and less insulting.

[Sssssailor]

Originally Posted by poiu

An interesting question is how to calculate the optimum avoidance turn. Turning not enough such as by only a few degrees as you suggested can in certain circumstances be as good as doing nothing and dangerous. Also, colregs require a clear and significant turn. I wonder if there have been collisions resulting from such errors. I can't remember seeing such a discussion.

COLREGs, like many laws out there, was written in blood. If there is a rule, there most certainly has been a collision associated with.

A change of course when there is risk of collision must be positive (apparent to the other vessel) and made in good time. I like to make it clear to another vessel what I'm doing, so at least 10-15 degrees.

I think using distance to judge when to maneuver is not a good way to go. Ships travel at different speeds and a cruise ship doing 24 knots is closing on you much quicker than a tug 'n tow. TCPA is key as far as I'm concerned. Especially when you have to deal with multiple targets. Prioritize by TCPA. I'll watch a boat till about 30min then make my move.

If you don't have ARPA..no biggie. Set a VRM (centered on you) to 0.5nm (or whatever you want for your CPA with the other vessel). Drop an off-center EBL on the target and wait 3-6min. Rotate the EBL along the track of the target. If they are steady, this should work fine to determine how much you need to come over. If the EBL is inside the VRM, change course until it's tangent.


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[nigel1]

Originally Posted by Sssssailor

If you don't have ARPA..no biggie. Set a VRM (centered on you) to 0.5nm (or whatever you want for your CPA with the other vessel). Drop an off-center EBL on the target and wait 3-6min. Rotate the EBL along the track of the target. If they are steady, this should work fine to determine how much you need to come over. If the EBL is inside the VRM, change course until it's tangent.

Excellent reminder on a little used tool. (all depending on if you have radar and can offset the EBL)

[Dockhead]

Originally Posted by nigel1

Excellent reminder on a little used tool. (all depending on if you have radar and can offset the EBL)

Yes, radar is good for this and furthermore, really helps visualize the geometry of a crossing. In hairy situations with multiple vessels I always switch to the radar screen of my system, where AIS targets as well as radar targets are displayed.

Before AIS, I used to use the EBL this way -- if you're dealing with just one target, it's much less work than a hand bearing compass -- just set the EBL on the target and watch -- does the target march up the EBL towards you? One thing this does which even most AIS sets don't do (a pet peeve of mine) is to instantly show you whether the target is passing ahead or behind -- great visualization.

Just keep in mind that radar, while very accurate for range, is fairly poor for bearing, especially small boat radars. In my experience radar bearings are less accurate than what you can do with a hand bearing compass using decent technique.

[Dockhead]

Originally Posted by rwidman

You go ahead and challenge that giant freighter or cruise ship. Me, I'll just stay out of danger.

With respect, what many on here are trying to tell you is that what you think is "just staying out of danger" often is actually putting you into danger.

And that no one is suggesting that anyone should "challenge" a giant freighter.

Might be worth thinking about with an open mind.

I'm sorry if I or others have been less polite than was called for, in saying this. Regards.

[poiu]

Originally Posted by Sssssailor

If you don't have ARPA..no biggie. Set a VRM (centered on you) to 0.5nm (or whatever you want for your CPA with the other vessel). Drop an off-center EBL on the target and wait 3-6min. Rotate the EBL along the track of the target. If they are steady, this should work fine to determine how much you need to come over. If the EBL is inside the VRM, change course until it's tangent.

I like that suggestion. I will get out the manual and try it.

[Sssssailor]

Originally Posted by nigel1

Excellent reminder on a little used tool. (all depending on if you have radar and can offset the EBL)

Ya a little trick I learned in the Coast Guard. Found it was more accurate at close range than the arpa radars. Trails are good too if your radar has it.

Cheers!


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[Richard_W]

Originally Posted by Dockhead

Yes, correct and important.

I think I mentioned it myself somewhere above.

If you're not in sight of one another, then collision avoidance procedures don't kick in yet.

How far that is depends on the height of the superstructure of the ship, and obviously on conditions, and also on your own eye height, but for my boat in good conditions and good size ships that's usually 12 miles or so.

To continue … assuming the vessels are in sight as defined by Rule 11, which is 12 miles in your case and let's take it as a fact for this discussion, and get us back to the questions posed by the OP in his first post.

Now, the Colregs define nowhere any distances where the collision rules are applicable or not … just that the vessels are in sight. My question is where the 10 and 5 miles distances and relevant changes in responsibilities you relay on come from?

There is another set of guiding distances quoted by Pelagic based on mariner training guide …

12 to 10 nm ... Detection
10 to 6 nm ... Assessment
6 to 3 nm ... Action

I understand that these guidelines are based on the best practices developed by mariners over the years for the (big) ships they operate. The turning circle, the stopping distance, and practicality of the maneuvers was taken into account. Are you saying that the same/similar guidelines should be followed by the small vessels, sailboats and trawlers, that can turn or stop within a few hundred feet and do not require miles to complete an emergency maneuver?

If the answer is yes, then what is expected of me (the small vessel) in each zone (detection/assessment/action) in terms of applying the rules 11-18?

Specifically, when/where in these zones the small stand-on vessel should remain stand-on vs taking action to either avoid "Colregs situation", or avoid collision?

[nigel1]

Originally Posted by Dockhead

Before AIS, I used to use the EBL this way -- if you're dealing with just one target, it's much less work than a hand bearing compass -- just set the EBL on the target and watch -- does the target march up the EBL towards you? One thing this does which even most AIS sets don't do (a pet peeve of mine) is to instantly show you whether the target is passing ahead or behind -- great visualization.

Nice touch with the Vesper Marine AIS, you get an on screen depiction of where the CPA will take place, all other things being equal.

[nigel1]

Richard,

There are no hard and fast rules. The distances quoted by Pelagic generally refer to open waters situations, and not a busy shipping lane.
So, if you are out on the ocean and detect a ship 10 miles away and can determine if risk of collision could exist, then by all means, make an alteration to such that the risk cannot develope.
On the other hand, if you are standing on, and the ship has not mad any alteration at 3 to 4 miles out, I'd be looking to bail out the best way I could.

Inshore, you may be obligated by Rule 9 or 10, but in any case those distances quoted will be reduced, by how much, that again will depend on conditions and circumstances, which is why no distances are mention in the Colregs.
If I was following a TSS and had a large ship overtaking with a small to zero CPA I'd be getting jittery when they were about a mile out.

Most of these commercial ships can alter course with no problem, no need for miles to complete a maneuver. For the past few years I've worked tugs of about 5000 to 6000 tonnes displacement which can be stopped within a couple of boat lengths and will turn on a dime. A lot of cargo ships are fitted with CPP and high lift rudders which allow reduced stopping time and give excellent rate of turn.

[donradcliffe]

I am not inclined to trust my life to the Colregs and professional mariners and I am a firm believer in the tonnage rule. As near as I can tell, there is a ship-to ship collision every three days under the current system, and the consequences of a collision with my sailboat would be extreme.

The introduction of AIS has been a game changer, and after more than 30,000 miles of sailing around with a Class B transponder with displays on OpenCPN and the Vesper watchmate, I have developed my own tweaks to the Colregs for the open ocean.

Regardless of what Dockhead thinks, I will typically notice a ship in the open ocean considerably before he notices me. He has brighter lights, a much bigger radar cross-section, and a more powerful AIS signal. If the AIS says the CPA is less than a mile (2 miles if I am crossing in front of the ship), if practical I will adjust course and/or speed BEFORE HE NOTICES ME to ensure that there is no Colregs burden on him when I do appear on his screens. Most of the time when he notices me he then holds course and speed and there are no problems. This works whether he is really watching or playing video games. At the 15-20 mile range I make my course change, it doesn't take more than 10 degrees to open up the CPA.

I did say most of the time--I was approaching one ship nearly head-on, and I wanted to pass green to green so I altered course to give him a CPA of 1.5 miles. When he noticed me, he gave the reflex turn to starboard and turned into me, so I had gybe and make a 30 degree change to starboard.

I am far more comfortable passing close behind a ship than close ahead. If the CPA is less than 2 miles I will turn to go behind. On occasion I have gone ahead, but will turn on the engine to give me more maneuverability and the added stress is generally not worth it.

[Pelagic]

Originally Posted by Richard_W

......Specifically, when/where in these zones the small stand-on vessel should remain stand-on vs taking action to either avoid "Colregs situation", or avoid collision?

Hi Richard
These kind of questions are discussed passionately in Marine Colleges around the world and like Philosophy studies, often give some students an unsatisfactory answer.

The Rules can be affected by Company or Master's standing orders and of course your assessment of your own comfort level with the aspect of the give way vessel or any other danger.

For example you can round a rocky point at 2nm or 8nm ....it all depends on your confidence with the circumstances and your desired ETA.
(I think it is fair to say that practice and training with using your radar in avoidance monitoring, will inspire confidence)

One clarifying point.... Risk of Collision can be determined by radar alone... So remember that ships will apply the avoidance rule in the fog and specifically will avoid altering to Port in a near head on situation. (As Don pointed out)

To give a guideline to your question.... Except in a low relative speed overtaking situation..... At 3nm, if I am not satisfied that the give way vessel has opened up a comfortable CPA, I will make a dramatic course change to indicate my intentions (+30°) that will exceed my safety CPA and closely monitor the other passing vl.... coming back on to my original course and my preferred CPA, once intentions are clear to all.