It is easy to forget that the normal rules we apply when vessels interact within sight of one another do not apply in restricted visibility. In fact, we need to behave in a very different manner.
Part (b) of this Rule reminds us to apply Rule 6. This may seem obvious, but especially in a sailing vessel we should consider if the engine is ready for use.
If the engine is warmed up and easy to start, you are probably better off sailing, with the engine off, but prepared to start it if necessary. This will improve your ability to hear other vessels. However, if the engine is slow to start, a better option is to have the engine running.
Another point, is that, at night, the side lights mounted on the bow of a sailing vessel often obscure the view ahead because of the back scatter caused by the moisture in the air, you may be able to see better with the masthead tricolour light on, this light should only be used when sailing!
Part (c) of this Rule restates the Rules of Section I, and are worth re-reading now.
Rules 5 and 7 part (b), imply that if you have working radar fitted, you should be using it. Of course, you should also know how to use it effectively, learn this before you get into restricted visibility!
If you detect a vessel by radar alone it is very difficult to determine exactly how close you will pass. Part (d) tells us to avoid the following:
an alteration of course to port for a vessel forwards of the beam, unless you are overtaking it.
an alteration of course towards a vessel abeam or abaft the beam.
Try visualising all the positions two boats could be in, and you can see the reasoning behind these rules.
Part (e) is probably the most important part of this Rule. It is common sense to slow down if you hear another vessel ahead, but if you think you are going to be very close STOP! To let the other vessel know that you have stopped, the fog signal for a power-driven vessel underway but not making way is two prolonged blasts at not more than two minute intervals. On hearing this the other vessel should realise they need to go around your vessel.
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