Imagine, for example, if you are sailing on port tack when you spot another sailboat way up to windward. The only sail he has up is a spinnaker, and it’s obvious from your angles of approach that if you each hold your course you will be in a collision situation. In a situation like this, how do you tell who has right of way?
The rules say that If you're both on the same tack, the windward boat should keep clear of the leeward vessel. But if you're on opposite tacks, and he's on starboard, you have to keep clear of him. And the trouble is, you can't tell if he's on port or starboard.
So let's go back and start from the beginning. Here are my usual steps:
1. Try to ascertain if he's under power as well as sail. If he is, he should be exhibiting a black cone, point down, in the bow. Most amateur sailors ignore this rule, so check for exhaust smoke or engine cooling water instead.
Ø If he's under power (even if he has sails up) he must keep clear of you.
2. If it's another sailboat under sail only, check which tack he's on.
Ø If he's on the opposite tack to you it's simple: port tack gives way to starboard tack.
Ø If he's on the same tack, the windward boat must keep out of the way of the leeward boat.
3. But here's the interesting bit:
Ø If you're on port tack, and you see a sailing vessel to windward and cannot determine with certainty whether the windward vessel has the wind on the port side or the starboard side, you shall keep out of the way of the windward vessel.
The rule doesn't address what happens if the situation becomes clearer to you at the last minute, and you suddenly decide that he is the one who should be keeping clear. But common sense should tell you that if you've already made an obvious move to keep clear of him, he will expect you to follow through and not create a last-minute emergency.
But the question remains: How were you to know what tack he was on, when he was flying only a spinnaker?
Well, the rules define the windward side as the side opposite that on which the mainsail is carried, OR the side opposite that on which the largest fore-and-aft sail is carried.
But this situation is ambiguous, since no mainsail is being carried by the windward boat. If the spinnaker was boomed out to port, I would say that the mainsail, if it were being flown, would be deployed to starboard. That would put the windward boat on port tack and he'd have to keep out of your way.
If a boomless cruising spinnaker were being flown from the starboard side, I'd say the boat was on port tack and the same situation would apply.
Nevertheless, if there's any doubt in your mind about any of this, you must revert to the rule under 3 above. Play it safe. Presume he is the stand-on vessel and that you should keep out of his way. Then make an large and obvious course correction so that he, too, knows what's in your mind.
If a man will begin with certainties, he will end with doubts; but if he will be content to begin with doubts, he shall end in certainties.
— Bacon, Advancement of Learning
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"But I'm not experienced."
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