Sailing vessel and RORO ship on collision courses - what do you think of the outcome?

[Chotu]

EXACTLY what my post was saying. Agree 100%

Originally Posted by jtsailjt

Au contraire. All those questions you pose regarding a crossing at close quarters are best discerned via the Mark 1 eyeball. You don’t need to see a channel marker or have a hand bearing compass or anything else besides seeing the drift (or lack of) of the other vessel relative to a reference point on your vessel. It’s as simple as determining that the other vessel is getting bigger and it’s not changing its position relative to a shroud or bow roller or some other reference aboard your boat and even an untrained person can discern that in just a few seconds. At longer distances or in restricted visibility, our electronic gadgets almost work miracles but once you’re up close, and need to decide which way to turn right NOW, there’s nothing like the naked eye. Another advantage of the naked eye in close quarters is that you might be able to see subtle clues such as that ship just put its rudder hard over, long before that hard over input results in changing angles that can be detected on any instruments.

If you have EITHER 10 seconds OR a minute to impact that means you’re WAY too close and you really don’t care which it is, you just don’t want to hit him and the best way to do that is by maintaining visual contact, and if you can clearly see the other vessel and are less than a minute to impact, the last place you should be looking is inside at your instruments. I find it frightening that you’d suggest such a thing and some inexperienced sailor might believe you.

Long ago I used to run intercepts from the back seat of an F4 Phantom and we had an often repeated saying that “one peek is worth a thousand cross checks”. which meant that once you were close enough to “peek” outside to see the target, you were much better off doing that than watching the drift on the radar and your instruments and depending on them to set up the intercept. But at longer distances when the target wasn’t yet visible or looked like just a speck to the naked eye, the radar and radar intercept officer were invaluable. The same holds true for “running intercepts” on ships at a much slower pace.

[fxykty]

Originally Posted by boatman61

My argument was based on the evidence supplied by the OP and that was given in ranges via AIS so that's what I worked on initially and decided he made a bad call..
Further on in the thread got into stand on and Colregs so I tried teasing more info out and he kindly posted a chart showing his course and the CPA marked by a cross.
The argument made by the Colregs group was as the ship was 5nm away the primary fault lay with the RoRo..
However I measured the distance from course change to CPA 0.00 at under 3nm so although the ship was as stated 5nm away the OP had chosen to alter his course to pass ahead of a ship less than 3nm from point of theoretical impact.. bad call to my mind.
To the skipper of the RoRo this could be just a temporary change of course to gain a better approach or simply a Yottie out for a joy ride.. if a ship responded to every yachts course change like this and turned to port some may never leave harbour.
So to my mind the OP laid excessive burden on the ships master and should have pointed higher by a few degrees to avoid the situation he found himself in..
In Colregs it says one should avoid creating situations.. loosely interpreted.. not create them.
Also, much is being made about radar here however this happened in waters where many boats will not have radar.. and few having AIS so maybe less emphasis on these luxury items for the priviliged and more on the reality of bearings using a static point on the boat like a stanchion or a compass.

Small correction: I didn’t change course (gybe) so as to cross the bow of the ship. In fact, when I gybed I wasn’t even considering their CPA/TCPA as the ship was still far distant (5 miles, which in a near shore context is a long way away) and we had two nearer ships (that had already altered courses).

Shortly after our gybe to starboard I checked and realised that our CPA with the third ship was now 0.0. OK, not so good - should have checked before making the course change - but it was still a long way away (3 miles and just under 20 minutes TCPA).

With clear, full visibility, settled and relatively quiet conditions, standing on and watching the RORO was perfectly fine, particularly since I expected he would do as the previous two ships did.

Regarding our course, we were near the limit of the gennaker - heading up 10-20 degrees was not a simple thing - we were effectively gybing downwind. As it turned out, we headed up 30 degrees to comfortably cross behind and left the gennaker luffing to avoid excess wind load. Our TWA went up to 115 degrees, now a reach rather than a broad reach.

In retrospect, and thanks to the further analysis afforded by this thread, we should have continued on our 210 course on port gybe until the RORO crossed in front. This would have placed us to leeward of the island and pretty much with the same angle on the final starboard gybe towards our berth.

So thanks all. Just leave off with the personal attacks please.

[sailingharry]

I think it is worth repeating, since many of the posts have seriously misrepresented this.


* OP did NOT "push the issue"
* OP was NOT "reckless"
* OP was NOT in "extremis"
* OP was NOT "unaware"





* OP DID monitor the situation
* OP DID have a plan to resolve the situation
* OP DID take evasive action in a (reasonably) timely fashion. The mere fact that the course change was only 30 degrees, in an easy to turn direction, to completely avoid the crisis, is conclusive proof of this! On the Chesapeake, with ships going 3-5 times as fast as this one was going, it is hard to avoid passing within 1/2 mile!



If he had not seen the situation developing, if a 180 degree course change was required, if an engine was required, then it might have been an issue.


I will say that, for all those anti-electronics folks, determining a proper course of action (as opposed to determining if a risk of collision exists) is significantly easier with electronics to feed the data stream.


I will also say that I have heard repeatedly from ocean cruisers that once they turned on AIS trasnmitters, they have had far fewer interactions from freighters -- when a freighter moving at 25 kts is meeting a sailboat doing 4 kts, it is FAR easier for the freighter to dial in 10 degrees of course change for 20 minutes, and so they do. And with AIS, they can actually "see" the little sailboat 20 miles out.

[chrisr]

Originally Posted by Dockhead

But there is yet another reason, which we haven't discussed -- a ship is not a dimensionless point in space -- it has length and beam. AIS, however, calculates CPA based on a dimensionless point in space -- the location of the AIS antenna. Some ships are several cables long -- and where is the antenna? AIS does transmit that data, but few recreational AIS receivers make this data easily available (Open CPN however does). So the CPA indicated on your instruments is NOT indeed CPA to whatever part of the ship might be slicing your hull open in a few seconds, but CPA to the AIS antenna. So you might think you are passing several cables ahead, but if the AIS antenna is aft (as it often is!), you might be on a collision course.

i'm not sure if this is correct ??

when setting up an AIS unit, one of the things to do is enter the antenna position relative to the ship ie dist fm bow to antenna / stern to antenna / port side / stb side.

i have always been under the impression that the CPA etc is then compensated for this...but is it ?

cheers,

[requiem]

Originally Posted by chrisr

when setting up an AIS unit, one of the things to do is enter the antenna position relative to the ship ie dist fm bow to antenna / stern to antenna / port side / stb side.

i have always been under the impression that the CPA etc is then compensated for this...but is it ?

So, a few items to consider: is the other ship calculating CPA based on radar, or based on AIS? Only the latter would have the potential of realistically calculating things so precisely, but a "proper" plot would be done by radar.

The manual for the software I have states "CPA gives distances based on center of Own-Ship and target. This assumes vessels maintain course (COG & SOG), regardless of current ROT", and similar for the bow crossing range calculations.

----

Let me now rant for a bit about electronics. I like electronics, I think they add incredible functionality. Unfortunately many people don't understand how to safely use them. You may have known people a few decades ago who were against using credit cards: "it's unsafe, there's no need to take on debt, balancing your checkbook is an important skill, etc etc". I see the use of, and reaction to, electronics as a similar thing. You can be far safer using electronics so long as you continue to use your brain.

GPS positions contain error. Bearing measurements contain error. When you do a visual plot, how often do you plot lines a few degrees to either side as a reminder of just how much error your plot might contain? How do you know that the AIS transmission from the sailboat didn't use a heading number taken just as it tried to round up? Just because the computer gives a number precise to three decimal places doesn't mean it's accurate to the nearest whole number.

Your eye can also deceive you; human wetware has its own set of bugs. There's another long thread on this sight about the dangers of using a fixed reference (e.g. a stanchion) on your own boat. Make sure the electronics and the mammals agree, and if they don't, figure out why.

[jmh2002]

Most of us who have had formalised training and certification have had the following drummed into us in the classroom, and tested for over and over again during written and oral examantions:

"NEVER rely solely on one source of information when making navigation decisions".

And the reality of this being true readily becomes apparent during time at sea.

[KetchJohnB]

Generally, ships just don't see you on radar or AIS.
Call them up at 5 miles and have a nice chat, as that is when you may show up. Let them know how you bear from their point of view.

My wife is best at that at about 2 a.m. on watch. She has moved all sorts of shipping out of our path or visa versa as needed. We have had long talks about this with shipping & also gets great tips on local services, usually a long way from where we are headed. E.Z. no hassle.

[El Pinguino]

Originally Posted by chrisr

i'm not sure if this is correct ??

when setting up an AIS unit, one of the things to do is enter the antenna position relative to the ship ie dist fm bow to antenna / stern to antenna / port side / stb side.

i have always been under the impression that the CPA etc is then compensated for this...but is it ?

cheers,

But is it?.... Probably not as that would depend on aspect amongst other things and I doubt any AIS have such refined software ... esp Class B.
I think it is probably best to assume that it does not.

One thing that I don't think has been mentioned is that the 'I' in AIS stands for identification... it was never designed for collision avoidance... that facility is simply a byproduct that undue reliance is placed on by many.

I would lay good money on the watchkeeper on the PCC mention in the OP looked at the AIS... saw that the CPA was half a cable astern without realising that was half a cable behind the AIS/GPS ant and that there was 180 odd metres of ship trailing along behind that... and that was all fine and good.

Random grab from MarineTraffic below.... the two PCCs on the left have about 180 metres hanging out the back.... the standard issue boxboat on the right has over 200 metres sticking out the front. Those 20k TEU jobs now coming into service probably have 300 metres trailing along aft of the AIS.

In my PO AIS is a very handy tool for coarse collision avoidance.... close in work use the eyeball with or without a hand bearing compass.

And lets not hear about radar.... many yachts don't have it, of those that do few will be stabilised and few operators will understand the concept of 'target trails' in establishing risk of collision.

Another bet I am up for.... I bet the watchkeeper on the PCC in the original post did not eyeball the yacht....

[boatman61]

Originally Posted by fxykty

Small correction: I didn’t change course (gybe) so as to cross the bow of the ship. In fact, when I gybed I wasn’t even considering their CPA/TCPA as the ship was still far distant (5 miles, which in a near shore context is a long way away) and we had two nearer ships (that had already altered courses).

Shortly after our gybe to starboard I checked and realised that our CPA with the third ship was now 0.0. OK, not so good - should have checked before making the course change - but it was still a long way away (3 miles and just under 20 minutes TCPA).

With clear, full visibility, settled and relatively quiet conditions, standing on and watching the RORO was perfectly fine, particularly since I expected he would do as the previous two ships did.

Regarding our course, we were near the limit of the gennaker - heading up 10-20 degrees was not a simple thing - we were effectively gybing downwind. As it turned out, we headed up 30 degrees to comfortably cross behind and left the gennaker luffing to avoid excess wind load. Our TWA went up to 115 degrees, now a reach rather than a broad reach.

In retrospect, and thanks to the further analysis afforded by this thread, we should have continued on our 210 course on port gybe until the RORO crossed in front. This would have placed us to leeward of the island and pretty much with the same angle on the final starboard gybe towards our berth.

So thanks all. Just leave off with the personal attacks please.

Apologies if you feel my post was a personal attack.. it was not intended as such.
The thread was started for opinions, or so I thought, I was defending my position and reasoning against those of others.. you personally had just become shall we say a statistic in an equation.
To all intents and purposes him altering course would have had you passing ahead.
That's the thing with these threads..
Learnt this myself a few times over the years...

[Pelagic]

Quote El Pinguio
And lets not hear about radar.... many yachts don't have it, of those that do few will be stabilised and few operators will understand the concept of 'target trails' in establishing risk of collision. unquote

I think there are a larger number of cruising boats from 38ft up that have Radar than you think

You can add a Radar scanner to most MFDs for about $1000. So not a huge outlay.

Learning to use in different conditions takes time and practice in good visibility

Especially if you are bouncing around heading into a seaway where MARPA is unreliable.

By using either your EBL offset or parallel index lines to monitor relative bearing, allows you to focus on sailing as the ship approaches the action zone .

Also priceless if you want to move in heavy fog

[Pelagic]

Originally Posted by boatman61

Apologies if you feel my post was a personal attack.. it was not intended as such.
The thread was started for opinions, or so I thought, I was defending my position and reasoning against those of others.. you personally had just become shall we say a statistic in an equation.
That's the thing with these threads..
Learnt this myself a few times over the years... [emoji3]

Thats why I tend to just generalise in these discussions boattie, as it is so hard to get a clear picture unless you were there.[emoji1303]

[Pelagic]

Originally Posted by KetchJohnB

Generally, ships just don't see you on radar or AIS.
Call them up at 5 miles and have a nice chat, as that is when you may show up. Let them know how you bear from their point of view.

My wife is best at that at about 2 a.m. on watch. She has moved all sorts of shipping out of our path or visa versa as needed. We have had long talks about this with shipping & also gets great tips on local services, usually a long way from where we are headed. E.Z. no hassle.

Sounds like you have a great partner on board[emoji1303]

Curious, do you have Radar on board?

The reason I promote getting one has been because of the times when yachts have panicked due to lack of situational awareness where Radar would have helped.

I remember one winter heading south as first officer on a cruise ship north of Cedros Is Baja with moderate wind and seas running

Had been monitoring this small intermittent target starting around 8nm range tracking slowly from my starboard to port as I was overtaking them.

We were running slow at 14 knots, they were running at about 6-7kn

At about 5nm, I altered about 30 to starboard to show them Red only and within a minute all their deck lights came on and I could see that they had dramatically altered to starboard and negated my avoidance plan.

Then a flustered skipper called to say that they were motoring due west to stay clear.

I explained that they could resume thier original southbound course and that I would overtake them on thier starboard side, no closer than 1.5 miles.

Things settled down and we chatted for a while.
He explained that his wife panicked woke him up saying we were almost on top of them, he panicked without being fully awake or aware and did exactly the wrong thing.

A radar range at least would have helped the wife to not panic and given the husband time to relax

[KetchJohnB]

Originally Posted by Pelagic

Sounds like you have a great partner on board[emoji1303]

Curious, do you have Radar on board?

The reason I promote getting one has been because of the times when yachts have panicked due to lack of situational awareness where Radar would have helped.

I remember one winter heading south as first officer on a cruise ship north of Cedros Is Baja with moderate wind and seas running

Had been monitoring this small intermittent target starting around 8nm range tracking slowly from my starboard to port as I was overtaking them.

We were running slow at 14 knots, they were running at about 6-7kn

At about 5nm, I altered about 30 to starboard to show them Red only and within a minute all their deck lights came on and I could see that they had dramatically altered to starboard and negated my avoidance plan.

Then a flustered skipper called to say that they were motoring due west to stay clear.

I explained that they could resume thier original southbound course and that I would overtake them on thier starboard side, no closer than 1.5 miles.

Things settled down and we chatted for a while.
He explained that his wife panicked woke him up saying we were almost on top of them, he panicked without being fully awake or aware and did exactly the wrong thing.

A radar range at least would have helped the wife to not panic and given the husband time to relax

Yes, I am lucky! First a Furuno, then lately, a B&G 4G. Radars are great for big stuff like ships for small sailboats. Not all that expensive.

I put on a few warning rings when we are offshore, but looking every 15 minutes is what we do.

The two times we have passed down the Baja (in Key West now), I do know Cedros Is. Pretty nice weather on the Pacific side too.

Best, John

[Dockhead]

Originally Posted by chrisr

i'm not sure if this is correct ??

when setting up an AIS unit, one of the things to do is enter the antenna position relative to the ship ie dist fm bow to antenna / stern to antenna / port side / stb side.

i have always been under the impression that the CPA etc is then compensated for this...but is it ?

cheers,

Good that you're asking this question, so that there is no doubt in anyone's mind -- NO, AIS systems (at least recreational ones) calculate CPA between two dimensionless points -- the antenna locations of the two systems. Discussed here: https://forums.ybw.com/index.php?thr...ntenna.472710/

AIS DOES also broadcast as part of static data information about the location of the antenna. Calculating CPA between the closest parts of each vessel would be theoretically possible, but would be a very complicated calculation. OpenCPN, which has the best AIS implementation I've ever seen, will DISPLAY the dimensions of the vessel to scale based on the static data, which is very helpful. But CPA calculation itself is based on antenna location (incidentially, the GNSS antennae, not the rx/tx anntennae) -- discussed here: https://opencpn.org/flyspray/index.p...desc&pagenum=2

Beware false precision. For a host of other reasons, you cannot safely navigate to pass so close to a ship that this will matter. The dimensions of the ship are not really important. A safe CPA is a much greater dimension than +/- the length of the ship will matter.

[Dockhead]

Originally Posted by Pelagic

. . .
By using either your EBL offset or parallel index lines to monitor relative bearing, allows you to focus on sailing as the ship approaches the action zone .

Also priceless if you want to move in heavy fog

Yes, maybe where Ping is few yachts have radar, but virtually all ocean-going yachts in this part of the world have radar.

Now whether the owners know how to operate the radars or not may be a different question. . .

To my mind radar is the most useful instrument on board after only depth sounder and compass, far more useful than chart plotter, AIS, etc.

Target trails are great, but to run stabilized mode usefully you need a better compass than most yachts have. I'm giving my boat a Furuno satellite compass this year for her birthday, specifically for this (and radar overlay).

EBL and index lines work a treat for the task we are discussing now. Immediate visul representation of the evolution of the relative bearing -- supremely useful.

As to fog, I'm sure any one of us could tell multiple stories on this subject, but my favorite one was from year before last, as we were on passage from Helsinki to Kalmar, on the SE coast of Sweden, couple of days and nights. Anyone who has been in these waters knows the treacherous winding channel between the rocks in Kalmarsund leading down to the bridge. Well, luck would have it -- night fell as we sailed down Kalmarsund towards the entrance to the channel. Then torrential rain. Then fog so thick I couldn't see my own forestay. What would we have done without radar? In the event we picked our way through, identifying each channel marker on the radar, threading our way through. We had a scare when a strong return appeared right in front of us like 100 meters ahead -- crash stop, then the return dissolved into a bunch of small dots, and then we heard the birds.

I don't really like my 4G radar all that much (particularly the useless MARPA), but it does have a couple of strong points, and one of those is the lack of main bang which allows you to see objects practically up under your bows. That is really really useful in pea soup fog like that.

And so we tied up safely in Kalmar harbour with an extra ration of grog.