Right-of-way Rules for Racers:  Passing Another Boat
[Reprint] Several questions have been raised by sailors participating in the R.G.S.C. races as to the rights and rules in passing situations.  Therefore, a quick review of the Right-of-Way rules seems appropriate.
Actually, the Right-of-way rules are quite simple:
1) STARBOARD TACK HAS RIGHT-OF-WAY OVER PORT TACK
 if both are on the same tack
2) CLEAR AHEAD HAS RIGHT OF WAY OVER CLEAR ASTERN
 if both are on the same tack but neither is clear ahead
3) LEEWARD HAS RIGHT-OF-WAY OVER WINDWARD
The problem arises when a boat with right-of-way alters course and interferes with another boat.  Most of the time this is legal, but not always.  Let us consider what can and cannot be done to prevent another boat from passing you.
First of all, if he’s on Starboard tack and you’re on Port tack, stay out of his way. If you’re about to round a DOWNWIND mark and you have an inside overlap, he has to give you room, but that’s all.
Secondly, if you’re both on the same tack and he’s clear astern on a DOWNWIND leg, you cannot sail below your proper course to get in his way if he’s passing you to LEEWARD.
If he is on the same tack but not clear astern, however, the situation gets a bit more complicated.  If he is neither clear ahead or clear astern, then he must have an overlap.  This means that a line projected across either boat’s transom (or furthest aft piece of gear), intersects any part of the other boat.  [Mast Abeam has been removed from the rules].
There are two passing situations to consider in an overlap situation.  First, if you are being passed to leeward under the new rule 17.1a boat that establishes a leeward overlap from clear astern within two of her hull lengths of a windward boat shall not sail above her proper course during that overlap.  "At first glance, it appears that a leeward boat may now luff head-to-wind regardless of the weather boat's position because there is no longer any reference to 'mast abeam' in the new rules. However, Rule 11 is modified by other parts of the new rules. Rule 17.1 invokes a restriction of the old rules -- you can't luff above your proper course if you established your overlap from clear astern (within two lengths of the windward boat) (Dick Rose, Sailing World).].  Remember, however, that he is the leeward boat and has right-of-way.  You cannot steer down on top of him or get in his way.  If you’re on a beat and he can point higher than you can, tack away because the leeward boat determines proper course.
The second situation is if he is passing you to windward.  He is trying to steal your wind!  You can luff up as high as you wish.  You have right-of-way and he must stay out of your way no matter what you do or how fast you do it. However, under the new rule 16: When a right-of-way boat changes course, she shall give the other boat room to keep clear.  Again, Dick Rose:  "The old rule contained exceptions that allowed you to assume a proper course when starting or rounding a mark. These exceptions are not in the new rule. But, the old rule also said you couldn't "obstruct" another boat that was keeping clear. The new rule is more permissive. It allows a right-of-way boat to change course as long as she gives the give-way boat enough space to avoid her in "a seamanlike way." This means that a starboard-tack boat can luff up to "obstruct" a port-tack boat, provided the port tacker has room to keep clear without having to make a crash tack."
So, the basic rule is, if he’s trying to pass to leeward, don’t mess with him.  If he’s going to windward, you can do anything you want as long as you give him room to keep clear when you change course.
Modified from the November 1984 Foghorn