Assessing the risk of collision.

I'm pretty sure that most of us have little difficulty in dealing with potential collision situations where we assume that everybody is aware of everyone else. With novice crew, I'm sure they arent left alone for long enough to allow a situation to arise or, if they are, there is a strict instruction to call an experienced crew/skipper in particular circumstances, e.g. they see any other vessel.

The fact is that it has been brought home to us that big ships may not be aware of us for a variety of reasons... so we cant assume that they will all take the appropriate action when they should. Nor can we be sure that, even if they look like they are taking appropriate action, they are actually taking that action.

Another fact is that there is no way of knowing which big ship could be the rogue amongst the many that are well run with responsible lookouts and deck officers.

Further , if we follow the rules, and are the stand on vessel, once a collision risk is deemed to exist, we must stand on until the point at which the action of the give way vessel alone cannot avoid a collision.

I still think there is a significant case for looking at the global situation, and avoiding risk of collision situations where possible.

I am also beginning to think that there must be a way for something along these lines to be written into the rules.

Having said that, any such change in our actions, or change in the rules, should not exonerate sloppy, irresponsible and negligent watchkeeping on big ships.
 
Not too sure how it affects the perspective with which one views the PoB incident but the Maersk Dover incident, although without csualties, is perhaps even more alarming.

Briefly the OOW failed to notice a l100,000 ton tanker 1.9 miles away on his starboard bow, which was being overtaken by a 17,000 ton container ship.

Even more worryingly - neither ship appeared on the Maersk Dover's radar.

So much for radar reflectors!
 
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However what really annoys me is when we are sailing along at night and I am off watch and the crew feels that we need to alter course for an overtaking ferry (we're Med based). When I quiz them (having seen the plotter track) later I am told that we had to or we could have been run down. I ask what the ColRegs say about overtaking vessels, I ask about confusing the helmsman of the overtaking vessel. They argue that they felt unsafe. Do I change my crew or just give them a hundred lashes?


[/ QUOTE ]
There is a recent tradegy in UK that supports your crew's action. I much prefer to be in the position of being the giveway ship, cause it is much easier to know it is your responsibility to alter co/spd. I like AIS with Shipplotter software cause it enables me to alter before being in visual range, and thus when visual, I am in the give way, or have manoeuvred sufficiently that the eventual CPA is sufficient to not need any further alterations.
 
[ QUOTE ]
I'm pretty sure that most of us have little difficulty in dealing with potential collision situations where we assume that everybody is aware of everyone else. With novice crew, I'm sure they arent left alone for long enough to allow a situation to arise or, if they are, there is a strict instruction to call an experienced crew/skipper in particular circumstances, e.g. they see any other vessel. <span style="color:blue"> I am often in a position of having to sail with novice crew and I can't stay awake for 24 hours at a time, so the novices have to be left 'in charge' sometimes. It goes without saying that they have strict instructions as to when they should call me, and that is outwith this discussion. Just seeing another vessel isn't usually enough reason to call me, but they do get strict instructions to watch carefully and take bearings and call me under particular circumstances... </span>

The fact is that it has been brought home to us that big ships may not be aware of us for a variety of reasons... so we cant assume that they will all take the appropriate action when they should. Nor can we be sure that, even if they look like they are taking appropriate action, they are actually taking that action. <span style="color:blue"> Read my original post about standing on with cauion. </span>

Another fact is that there is no way of knowing which big ship could be the rogue amongst the many that are well run with responsible lookouts and deck officers. <span style="color:blue"> see previous remark </span>

Further , if we follow the rules, and are the stand on vessel, once a collision risk is deemed to exist, we must stand on until the point at which the action of the give way vessel alone cannot avoid a collision. <span style="color:blue"> That is NOT what the IRPCS says. In general terms you stand on until you BELIEVE that the other vessel is not complying. The rules are intentionally vague about what distance this means as it depends on the vessel, its ability to manoevre, the visibilty etc</span>

I still think there is a significant case for looking at the global situation, and avoiding risk of collision situations where possible. <span style="color:blue"> Look at the global situation and apply the IRPCS to each particular situation as they occur is my suggestion. </span>

I am also beginning to think that there must be a way for something along these lines to be written into the rules. <span style="color:blue"> I disagree profoundly. The IRPCS are pretty good and cover most every situation. </span>

Having said that, any such change in our actions, or change in the rules, should not exonerate sloppy, irresponsible and negligent watchkeeping on big ships. <span style="color:blue"> I finally agree with you on a point. </span>

[/ QUOTE ]
 
No one has mentioned the benefits of the digital hand-bearing compass (Autohelm Personal compass - not sure if it's available now, inexplicably) which I find a great help. Just aim at the problem vessel, fire off 3 "shots" fairly quickly, using the gunsights provided, and take an average. Repeat that 5 or 10 minutes later and if the result is different, even by 2 or 3 degrees, you can be pretty sure you are going to miss. Of course, if the result is close, you can repeat the exercise at will.

Glad to learn that basically we all think the same about not giving way prematurely.

Regards to all.
 
From my relatively limited experience of about 30 North sea crossings and a couple of Fastnets, it would appear to me, that it is the ships Hull down on the horizon, that are likely to cause a problem...Those that one can see, are invariably going to be long gone by the time you reach their track. Particularly, if you allow, say 6knots boatspeed for self and 20 knots for target vessel. I mile in 10 mins for self. 3.3 miles for target in same time. max vis from cockpit approx 6-7miles? Justifies the purchase and use of Radar to see the ones that you can,t see from the cockpit, and very often one can see the slight alteration in course made by target vessel to pass astern of you!.. Go with John & Robin on this!
 
1. First rule is never to assume anything about ships going in straight lines.

Non-constant bearing is not an indication of safety in heavy shipping areas. The ships are altering course for each due to the wide disparity in their speeds (overtaking). As with Ouzo the ships can change course on to your position at a late stage. You might not even be able to see the other ship and with DSC you will not have heard them negotiating.

If you want to practice: charter a boat in Singapore and you can play all day with the big boys. First look will assume they are all nicely arranges in lanes, then you realize they are turning in and out of the lanes for the docks. Add a few local tugs and crane movements and no amount of bearings will save you.

2. Second, is that they can only miss you if they know you exist.

If you choose to dress up in black and try to cross the M25 at night then you could make it by running quickly between the lines and stopping on the lane markings. It would work fine as long as you assumed all the cars did not change lanes. BUT sadly some one would change lane over you.

Splat. Same works with ships. If you assume taking bearings works you will end up in difficulty.

3. Third, using the distance between ships mast lights is not reliable in any way. There are some strange ships and tall tugs that will really throw you.

4. Hand bearing compasses are more accurate than 5 degrees! Using the above example of 15knots and 5knots at right angles. Consider the positions every 4 minutes. (Ship travels 1mile, yacht travels 1/3mile)
You can draw the triangles. Now say at about 1 miles from CPA they turn small 18 degree helm change towards your course. Now you have 4 minutes, and counting. AIS will not tell you it has happened for at least 1 minute. You then need to investigate 1 minute. Taking bearings will not tell you a constant bearing until after 2 more readings. 2 minutes left. Ships is approx 1/2 mile away. If you continue you hit the bows. If you stop the CPA will be 300meters. So you stop. But actually the ship was just half way through a big course change towards Southampton docks, which they planned to do later, but due to the head on ship traffic they have started early. You only saw the initial course change, not the final change they intended. Splat.

There is only one way to survive and that is if they know you exist. As fellow mariners it is your duty to make sure they know you are there. If a CPA will be less than a mile you must confirm they have seen you.

Little timid yachts, with no reflectors that will not use the Beamlight/VHF/Horns early enough are just like people crossing the M25 dressed in black. If you surprise a ship you are as guilty as any negligent ship lookout.
 
John,

didnt mean to be dissagreeable, just some musings:


[ QUOTE ]
[ QUOTE ]
I'm pretty sure that most of us have little difficulty in dealing with potential collision situations where we assume that everybody is aware of everyone else. With novice crew, I'm sure they arent left alone for long enough to allow a situation to arise or, if they are, there is a strict instruction to call an experienced crew/skipper in particular circumstances, e.g. they see any other vessel. <span style="color:blue"> I am often in a position of having to sail with novice crew and I can't stay awake for 24 hours at a time, so the novices have to be left 'in charge' sometimes. It goes without saying that they have strict instructions as to when they should call me, and that is outwith this discussion. Just seeing another vessel isn't usually enough reason to call me, but they do get strict instructions to watch carefully and take bearings and call me under particular circumstances... </span> <span style="color:red"> more or less what I said.... seeing a ship was just one example. </span>

The fact is that it has been brought home to us that big ships may not be aware of us for a variety of reasons... so we cant assume that they will all take the appropriate action when they should. Nor can we be sure that, even if they look like they are taking appropriate action, they are actually taking that action. <span style="color:blue"> Read my original post about standing on with cauion. </span> <span style="color:red"> wasnt there a suggestion in the report that the Ouzo may have been standing on, probably with caution </span>

Another fact is that there is no way of knowing which big ship could be the rogue amongst the many that are well run with responsible lookouts and deck officers. <span style="color:blue"> see previous remark </span>

Further , if we follow the rules, and are the stand on vessel, once a collision risk is deemed to exist, we must stand on until the point at which the action of the give way vessel alone cannot avoid a collision. <span style="color:blue"> That is NOT what the IRPCS says. In general terms you stand on until you BELIEVE that the other vessel is not complying. The rules are intentionally vague about what distance this means as it depends on the vessel, its ability to manoevre, the visibilty etc</span> <span style="color:red"> we are both right... Rule 17 mentions both situations. your situation allows an action before mine </span>

I still think there is a significant case for looking at the global situation, and avoiding risk of collision situations where possible. <span style="color:blue"> Look at the global situation and apply the IRPCS to each particular situation as they occur is my suggestion. </span> <span style="color:red"> I think we can agree to differ on this.... I think both are appropriate in various circumstances </span>

I am also beginning to think that there must be a way for something along these lines to be written into the rules. <span style="color:blue"> I disagree profoundly. The IRPCS are pretty good and cover most every situation. </span> <span style="color:red"> just a thought... it is often imposed by local port authorities </span>

Having said that, any such change in our actions, or change in the rules, should not exonerate sloppy, irresponsible and negligent watchkeeping on big ships. <span style="color:blue"> I finally agree with you on a point. </span> <span style="color:red"> thank goodness for that</span> /forums/images/graemlins/smile.gif

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What sort of CPA would I expect a big ship look for/set up when avoiding a yacht?

In common with other contributors to the thread I have experienced ships make course changes routinly to avoid us - well before we need to do anything. I am never quite sure what number they have in mind for the CPA though. Does "I am going to miss you by bloody miles" mean 1/4 mile, 1/2 mile, 1 mile? Does anyone have any first hand experience of this? (don't worry I am not going to write it down and rely on it)
 
[ QUOTE ]
What sort of CPA would I expect a big ship look for/set up when avoiding a yacht?

In common with other contributors to the thread I have experienced ships make course changes routinly to avoid us - well before we need to do anything. I am never quite sure what number they have in mind for the CPA though. Does "I am going to miss you by bloody miles" mean 1/4 mile, 1/2 mile, 1 mile? Does anyone have any first hand experience of this? (don't worry I am not going to write it down and rely on it)

[/ QUOTE ]I seem to remember a court finding that the ship that ran down the moody that was lost in mid channel a couple of years ago was 'ticked off' for suggesting that a couple of cables was adequate.

Depending on visibility and circumstances I have seen anything from half a mile to a mile or so used as CPA.

If I have been the give way vessel (in a yacht) and altered to pass the stern of a ship, I can often end up passing a couple of cables behind him. This would be daylight and good visibility. In heavy weather it is usually more.
 
Little timid yachts, with no reflectors that will not use the Beamlight/VHF/Horns early enough are just like people crossing the M25 dressed in black. If you surprise a ship you are as guilty as any negligent ship lookout.
...........................................................................

My thoughts exactly and I am surprised so little mention was made in the Ouzo report of VHF and DSC. which apparently was not used right through the incident!!!

Yes you can hear the negotiating between the big ships on ALL modern radios wether fitted with DSC or not....The chat takes place on normal port control ot ship to ship channels. You just have to make sure you scan them.



John
 
CPA = closest point of approach

Very useful discussion - I've nothing to add except a note for those who might be trying to work out what CPA means. (Must be hundreds of them, from Clinical Pathology Accreditation to Certified Public Accountant).

In this thread it means Closest Point of Approach.
 
It is impractical to scan the ship-to-ship channels as some boats chatter for ages.

The only way to follow them is to know who is calling who and without the position, name information on channel 16 you can not follow the conversations. The technology should have been design differently to allow everyone to follow the calls with ease.

But the biggest nutty idea is to only tell people what you have done as opposed to what you will do. Technology Stupidity.
 
I know it sounds like I keep banging on about AIS (and I don't think its a substitute for looking so don't go there) but a yacht really can actively participate in the traffic situation if it knows the names and call signs of all the local participants.

We do call give way vessels which appear not to be giving way so as to avoid last minute chaos and they do respond. And we offer to give way. This works because we know which one is which and we know their name and keep the vhf proceedure tight and professional. <u>But mostly, I think, its becuase we know their name, and they know we do.</u>
 
[ QUOTE ]
My thoughts exactly and I am surprised so little mention was made in the Ouzo report of VHF and DSC. which apparently was not used right through the incident!!!

[/ QUOTE ] In the court of inquiry following many collisions, the use of VHF radio has been found to be a distraction or a contributing factor to the collision. It will be interesting to see whether AIS changes this. I suspect that a yacht calling a ship to establish the ships intentions will need more than the ships name and details from AIS. You would need to give an accurate distance and bearing from the ship which can only be given with any reliability from a good radar set on the yacht.

In short I am NOT convinced that frequent use of the VHF is to be resorted to as some sort of panacea for collision avoidance. In general, (despite the frequent use of VHF by big ships alluded to) I believe VHF radio can be a dangerous distraction in collision avoidance.
 
There are 2 ways to use a VHF:

"Help help I'm the yacht under your bows..."

"Good morning this is the yacht 2.5 miles on your starboard bow, heading south. My position is ... Have you seen me?"

I only support the later. And only for a ship that will make it inside the approximate 1 mile safety ring. Assuming also you are in open waters. If you have to surprise a ship with a "help" type message you are not helping at all as they have many more worries.

Yes, I have had to do "help help" type calls. Sadly one of the worst was to a British Navy support ship that suddenly did a U turn after passing me. Even the best radars need observant operators! They called afterwards and said they were surprised to see an English yacht. I informed them that there was actually 4 of us in the area!
 
[ QUOTE ]
There are 2 ways to use a VHF:"Good morning this is the yacht 2.5 miles on your starboard bow, heading south. My position is ... Have you seen me?"

I only support the later.

[/ QUOTE ]
How do you know that the ship that is answering is the one that you've seen, and that the yacht that they've seen is you and not someone else?
 
[ QUOTE ]
I suspect that a yacht calling a ship to establish the ships intentions will need more than the ships name and details from AIS. You would need to give an accurate distance and bearing from the ship which can only be given with any reliability from a good radar set on the yacht.


[/ QUOTE ]

Unless I am missing something here: I select "measure"; put the cursor on icon for MV Nonsuch on the chart display; drag it to the boat icon in the middle of the screen (me) and read off the distance and bearing. I don't need radar to do that (I may need it for lots of other things but that is a different issue)
 
[ QUOTE ]

How do you know that the ship that is answering is the one that you've seen,


[/ QUOTE ]
Becuase you call it by name.
Below is a shot of a plotter screen showing AIS information, since it seems like folks don't realise quite what you get. The poor quality of the screen shot is to do with it going from bmp to pdf to jpg, in reality its of usual pc quality. We are the purple boat bottom right. The line from each boat its 10min projected track. If I felt I needed to call any of those boats I could do so with reasonable confidence I was calling the right one.

http://www.woodbridgecruisingclub.co.uk/ais.jpg

Image was too big so edited it to a link. (Just using wcc to host image - opinions should not be taken to be those of the club)
 
That's if you have AIS. Solarneil was just discussing using VHF and didn't mention having AIS.
 
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