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Old 15-04-2015, 10:58   #211
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Re: Phuket! I have "Right of Way"

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Originally Posted by Polux View Post
I have no doubt Monte is an experienced sailor and knows what is doing but sometime all of us say things that are not actually exactly what we want to say.

Assuming a distance of 5NM, perpendicular courses, considering a ship speed of 18K and a sailboat speed of 6k, if you point to the stern of an incoming ship that was previously on a collision course and maintain that course/speed (that is what one should do when changing course to avoid a possible collision) he would pass at about 4NM on the stern of the ship. That is way too much and a not necessary big loss of time and distance. The change of course would be of about 55º.

When on a collision course if we want to give way to the ship what is normal is to change our course in 25º/30º towards the ship. That would clearly indicate to the ship that we have changed course and are giving him way.

Even if the ship had already altered course to avoid a collision, this change of course will be much bigger then the one on the ship and will not create the danger of a collision on another CPA (on the case the ship deviated towards the sailing boat). Anyway provably the Ship would return to the previous course but we should never assume.

With this new course the sailing boat will be pointing initially way ahead of the ship and would pass about one and a half, one mile behind his stern. Off course the sailing boat can always open the course to pass more astern if needed.

Pointing to the ship at 5NM will implicate a change of course of about 55º and with the continuous course alteration needed the sailingboat would be making about a 1/4 of a circle. It is not only the distance lost but the continuous sail trim that would implicate.

I think I had understood what Monte was saying (and in fact I do it even if in fact I do not point to the stern, except on the last phase) but that is a maneuver that one do but not at a distance of 5NM (as he mentioned) but at a much shorter distance.
If you point the bow at the stern of the ship, even at 5 miles, this is good. As he goes by, you keep altering course to keep your bow pointed at his stern, until you are back on your course. At that distance, you will make a big alteration to start with, but you will get back onto your course fairly soon. The big alteration accelerates unwinding of the situation. The big alteration is also good in terms of the ship's seeing and recognizing what you're doing. So it's inefficient, but not grossly so, and has all kinds of pluses. Might cause problems with point of sail, if you're under sail.

The ideally efficient way to make an alteration to pass behind would be to
make one single alteration as you watch the AIS, until you see the CPA you want, and then keep that one course until you're clear. That's what I do, when possible. But sometimes you can't, because it involves a forbidden small alteration. Especially if it involves an alteration to port.

But that method requires electronics, or without electronics, calculations and observations. Also, it requires the other vessel to hold course and speed. In cases like this, ideal efficiency is not always the most important thing, not at all.

The point of the "stern-pointing" method is that without any electronics, calculations, or observations whatsoever, without the need for any hesitation or reflection at all, you get a guaranteed safe crossing, instantly. And it will work no less well if the other vessel alters course and speed, since you are constantly turning to keep his stern in view. Methods like this which are extremely simple, which require no equipment, and which are easy to remember, and which can reliably resolve dangerous situations, are just extremely valuable, in my opinion.

It was taught to me decades ago by an old merchant marine officer. At the time I had a boat without a single electronic device, not even a depth sounder, nothing but a compass.
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Old 15-04-2015, 11:09   #212
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Re: Phuket! I have "Right of Way"

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Are you not an apologist of the no need of any licence for Captains of recreational boats? (sorry if I am mistaken). If so how can you have the opinion that most boaters don't know the "COLREGS let alone understand them" and oppose a mandatory licence that implicates an examination that assures that to pass it one has to knows COLREGS?
If we do go to mandatory licensing -- and I'm not expressing any opinion about that here -- it's essential, in my opinion, to make sure that it actually tests real knowledge of the Rules. If it's like a driver's license in the US, then definitely not worth bothering with it. That's because you can't sum up the Rules in a 10-page "boating safety" pamphlet, and I think it even adds to the danger on the water, if people are encouraged to think that they can read a simplified "boater's safety" pamphlet and think they don't need to know anything else about collision avoidance. To really understand the Rules, you also have to understand something about techniques of collision avoidance. This is not at all trivial knowledge, not at all comparable to traffic rules for cars.
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Old 15-04-2015, 12:01   #213
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Re: Phuket! I have "Right of Way"

Another use for accurate estimation of angle on the bow is estimation of the perpendicular distance to the track of another vessel. Use the thumb rule sine = angle/60 which is useful for narrow angles, and allowing the range to approximate the hypotenuse of the triangle which is a good estimate for small angles, the distance to the vessel's track is

Distance to track = Range x bow angle/60

For example, the track of a vessel at 4 nm with a 15 degree bow angle lies 1 nm from you.
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Old 15-04-2015, 12:05   #214
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Re: Phuket! I have "Right of Way"

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Another use for accurate estimation of angle on the bow is estimation of the perpendicular distance to the track of another vessel. Use the thumb rule sine = angle/60 which is useful for narrow angles, and allowing the range to approximate the hypotenuse of the triangle which is a good estimate for small angles, the distance to the vessel's track is

Distance to track = Range x bow angle/60

For example, the track of a vessel at 4 nm with a 15 degree bow angle lies 1 nm from you.
Fantastic, very advanced techniques, wow.

But how do you distinguish 15 degrees from 10 or from 20? It's not my experience that it's possible to eyeball aspect with even rough accuracy. Or maybe you have some technique for that?
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Old 15-04-2015, 12:14   #215
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Fantastic, very advanced techniques, wow.

But how do you distinguish 15 degrees from 10 or from 20? It's not my experience that it's possible to eyeball aspect with even rough accuracy. Or maybe you have some technique for that?
If your standing in your cockpit and the centre of the other boat lines up with your stbd masthead stay (roughly 15degrees on a 30ftr.. decreases as the boat gets longer) and stays there.. your gonna hit him.. or him you.. depending on ones opinion..
215 posts about a dickhead on a boat.. with velcrose arse fittings..
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Old 15-04-2015, 12:21   #216
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Re: Phuket! I have "Right of Way"

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Fantastic, very advanced techniques, wow.

But how do you distinguish 15 degrees from 10 or from 20? It's not my experience that it's possible to eyeball aspect with even rough accuracy. Or maybe you have some technique for that?
The only way to gain skill is practice.

These techniques are actually quite old, and were refined for submarine warfare in WWII. With a short look at a target through a periscope, rapid and accurate course/speed/range was necessary to allow intercept of the target at close range to allow effective torpedo placement.

The quick look gave an accurate bearing and telemeter range, but there was no instrument for bow angle, so a refined eye through practice was required. With bearing, range, and bow angle, the target's parameters could be known based on a six second look.

That's why "zigging" (randomly and frequently changing course and/or speed, including sinuous electrical steering devices) was so important for ships alone or in company in a convoy.
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Old 15-04-2015, 12:35   #217
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Re: Phuket! I have "Right of Way"

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If we do go to mandatory licensing -- and I'm not expressing any opinion about that here -- it's essential, in my opinion, to make sure that it actually tests real knowledge of the Rules. If it's like a driver's license in the US, then definitely not worth bothering with it. That's because you can't sum up the Rules in a 10-page "boating safety" pamphlet, and I think it even adds to the danger on the water, if people are encouraged to think that they can read a simplified "boater's safety" pamphlet and think they don't need to know anything else about collision avoidance. To really understand the Rules, you also have to understand something about techniques of collision avoidance. This is not at all trivial knowledge, not at all comparable to traffic rules for cars.
I agree even if a rudimentary knowledge is better than no knowledge at all.
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Old 15-04-2015, 12:45   #218
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Re: Phuket! I have "Right of Way"

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Rule 7 has something to say about making assumptions
Do you know what is required to hold a licence to be captain of a ship of considerable size? Besides the theoretical knowledge do you know how many hours and miles of practice on lesser positions they have to have before making the tests for captain?

I believe we can say that we can assume that a ship captain knows more about the Colregs and collision avoidance then the typical yacht Captain.
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Old 15-04-2015, 13:22   #219
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Re: Phuket! I have "Right of Way"

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Originally Posted by fryewe View Post
The only way to gain skill is practice.

These techniques are actually quite old, and were refined for submarine warfare in WWII. With a short look at a target through a periscope, rapid and accurate course/speed/range was necessary to allow intercept of the target at close range to allow effective torpedo placement.

The quick look gave an accurate bearing and telemeter range, but there was no instrument for bow angle, so a refined eye through practice was required. With bearing, range, and bow angle, the target's parameters could be known based on a six second look.

That's why "zigging" (randomly and frequently changing course and/or speed, including sinuous electrical steering devices) was so important for ships alone or in company in a convoy.
Really interesting; thanks for sharing this.

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Old 15-04-2015, 13:24   #220
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Re: Phuket! I have "Right of Way"

It depends on the region of the world. Indonesian waters have large commercial vessels with no watch at all on passages. My friend was nearly run down from behind by a cargo ship that he managed to avoid by only meters. He never saw anyone on watch or at the helm. They had no AIS and did not answer VHF hails. So not all large ships are blessed with competent masters in some parts of the world.

In past months refugees were rescued by Italian authorities from a vessel not under command. Crew had apparently set the AP for collision course with an island and abandoned ship. There was some publicity on this event at the time.
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Old 15-04-2015, 13:26   #221
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Re: Phuket! I have "Right of Way"

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Originally Posted by Polux View Post
Do you know what is required to hold a licence to be captain of a ship of considerable size? Besides the theoretical knowledge do you know how many hours and miles of practice on lesser positions they have to have before making the tests for captain?

I believe we can say that we can assume that a ship captain knows more about the Colregs and collision avoidance then the typical yacht Captain.
Err, Polux, I hate to tell you this. But Nigel is a professional mariner and ship's master. He's the captain of a ship. I'll send you a "red-faced" smiley to use in your next post
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Old 15-04-2015, 15:22   #222
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Re: Phuket! I have "Right of Way"

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Err, Polux, I hate to tell you this. But Nigel is a professional mariner and ship's master. He's the captain of a ship. I'll send you a "red-faced" smiley to use in your next post
And what has that to do with him not finding that we can assume that the typical Ship Captain is more knowledgeable than the typical yacht captain?

I continue to say that we can assume that.

Someone here had the opinion that most yacht captains don't know nothing about COLREG rules, I would not say so much but I am quite sure that the typical ship captain knows a lot more than the typical Yacht captain not only about COLREG but about avoiding collisions on the sea.

Probably he was joking when he said that we cannot assume that.
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Old 15-04-2015, 15:29   #223
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And what has that to do with him not finding that we can assume that the typical Ship Captain is more knowledgeable than the typical yacht captain?

I continue to say that we can assume that.

Someone here had the opinion that most yacht captains don't know nothing about COLREG rules, I would not say so much but I am quite sure that the typical ship captain knows a lot more than the typical Yacht captain not only about COLREG but about avoiding collisions on the sea.

Probably he was joking when he said that we cannot assume that.
ROFLMAO... you should spend more time in the English Channel.. or the Straits of Gibraltar..
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Old 15-04-2015, 15:41   #224
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Re: Phuket! I have "Right of Way"

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And what has that to do with him not finding that we can assume that the typical Ship Captain is more knowledgeable than the typical yacht captain?

I continue to say that we can assume that.

Someone here had the opinion that most yacht captains don't know nothing about COLREG rules, I would not say so much but I am quite sure that the typical ship captain knows a lot more than the typical Yacht captain not only about COLREG but about avoiding collisions on the sea.

Probably he was joking when he said that we cannot assume that.
He was not joking. Ship's bridges vary in quality, just like yacht skippers. The average level of knowledge of course is 1000x more, so to that extent, you are right. But you can't assume anything -- it's not rare to find a ship being run in an unprofessional way. Which I think was Nigel's point.
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Old 15-04-2015, 15:57   #225
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Re: Phuket! I have "Right of Way"

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?..Ship's bridges vary in quality...you can't assume anything -- it's not rare to find a ship being run in an unprofessional way...
...Costa Concordia...
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