Lights and shapes of vessels — When you can't see her
Reading notes · Lights and shapes of vessels
The sound signals. Short and prolonged, what she carries by length, and the fog signal of every vessel in part 2 — seven signals for ten vessels, because seven share one.
Open the interactive chapter →The same material with the chart, the drawings and the exercises.
When you can't see her · topic 1
Two blasts, and everything is built from them
Sound is the half of the rules that people skip, and it is the half that works when nothing else does. In fog you have no lights, no shapes and no aspect. You have a noise and a bearing.
And the vocabulary is two words long. A short blast is about a second. A prolonged blast is four to six — call it five. There is no third length, and nothing in the rules asks you to judge anything finer.
Look at the strips rather than the numbers. A prolonged blast is five times a short one, and at sea that difference is unmistakable even when you cannot tell where it is coming from. Written down they are two phrases; drawn to scale they are two different things.
Press a strip and you will hear it. The sound is generated from the same numbers the strip is drawn from — so it cannot drift away from the picture. It plays the pattern only, never the two-minute wait.
But reading it is still the skill. An examiner will ask you «what does one prolonged and two short mean?» in words, and a lookout reports it in words. The sound is here to fix the length of a prolonged blast in your ear, not to answer anything for you.
And then two minutes of nothing
Every other strip in this part is drawn eighteen seconds wide, because that is what it takes to see the pattern. This one is drawn two minutes wide, and it is the only one.
The reason is that the pattern and the interval are different lessons. The pattern is a shape; the interval is a number. A shape you draw; a number you say — except once, when the number is so extreme that seeing it is the point.
An ordinary vessel making way is audible for four per cent of her cycle. The longest signal in the book — a vessel aground — manages twenty-eight, and only because she rings every minute instead of every two. For the rest of the time there is nothing at all, and the ship is still there.
And the silence is not slack time — it is what the interval is for. In restricted visibility you keep your lookout by sight and by hearing , and you can hear nothing at all while your own whistle is going. That gap is where the others are, tapping away in the fog. Two minutes is not a limit on how often she may sound. It is how long everybody agrees to be quiet so that everybody can listen.
That is what fog is: a very small amount of information, arriving late, and then a long silence in which nothing has changed except the range.
When you can't see her · topic 2
One prolonged, or two
Two prolonged blasts instead of one, and she has stopped. That is the whole difference, and it is missed constantly — because both vessels are under way, and only one of them is moving.
You met this distinction in part 1, drawn in lights: sidelights and a sternlight come on when she moves through the water and go out when she stops. In fog you cannot see any of that. What you get instead is one blast or two.
And the third strip is there to stop the obvious mistake. One prolonged and two short is not «two blasts» — the two after it are short , and that changes the rule and the vessel. Count the prolonged ones first, and only then count what follows.
When you can't see her · topic 3
The ones you give in sight of each other
These are not fog signals. They are given in sight of one another, and they say what you are doing as you do it — not what you intend and not what you would like.
One, two, three: starboard, port, astern. They are the whole of Rule 34(a) and they take ten seconds to learn.
And here is where the two halves of this part collide. Three short blasts is Rule 34: she is going astern, and you can see her. One prolonged and three short is Rule 35(e): a vessel under tow, in fog, and you can see nothing at all. Both are «three short» to anyone counting carelessly, and they are different rules in different weather. Count the prolonged one first — it is the thing that tells you which world you are in. A prolonged blast in front of them and you are in fog, reading Rule 35. None, and you can see her, and this is Rule 34.
Five is not more of the same. Rule 34(d) is the only signal in the book that is about the other vessel : it means I cannot read what you are doing, or I do not believe it is enough. If you hear it in a crossing situation, it is meant for you and you are the one who has to act.
And here this module stops. What a blast means is this module's job and you now have all of it. When you are obliged to give one — and who gives way to whom — is Rule 34's other half, and that lives in «The vessel, all round».
What the whole module gave you
That is the whole of Rules 20 to 37, in four parts. You can name any vessel in the collision rules from her lights, from her shapes, from any bearing, and from a noise in fog.
It is worth saying what that is not. It is not seamanship yet. Knowing that one prolonged and two short means a vessel who cannot get out of your way is the easy half; deciding what you are going to do about her, at night, with a tide under you , is the other one.
That is «The vessel, all round» — the steering and sailing rules, who gives way, and when. Every signal you have learned here has a moment attached to it, and the moments live there.
You now know what she is saying. The next module is about answering her.
Open the interactive chapter →The same material with the chart, the drawings and the exercises.