Excerpt from Understanding the Racing Rules of Sailing
by Dave Perry,

Rule 18.2(b) - Overlapped at the zone
If boats were overlapped before either of them reached the two-length zone and the overlap is broken after one of them has reached it, the boat that was on the outside shall continue to give the other boat room. If the outside boat becomes clear astern or overlapped inside the other boat, she is not entitled to room and shall keep clear.

“I understand now about the significance of the ‘two-length zone;’ but how do I know where the ‘two-length zone’ actually is on the water?”

Well, at first it’s difficult, and then after you’ve raced more and more it becomes easier to judge. Let’s say you race a 30-foot boat. Two boat-lengths is 60 feet. That’s the length of a bowling lane, or about the distance from the pitcher’s mound to home plate on a baseball diamond. Doing 6 knots (about 10 feet per second) you’ll cover two boat-lengths in 6 seconds. Measure it out and mark it with two orange poles or something at your club so everyone will learn to “guesstimate” it better.

“Okay, but what if two boats simply can’t agree on whether an overlap was obtained or broken before reaching the two-length zone?”

Competitors and protest committees should try their hardest to remember and determine the facts. However, realizing that there will be disputes, the rule writers built in some “guidance” to help resolve such disputes. Rule 18.2(e) (Overlap Rights) reads, “If there is reasonable doubt that a boat obtained or broke an overlap in time, it shall be presumed that she did not.”

In other words, if you come up from behind and claim that you got the inside overlap before the outside boat reached the two-length zone, but the outside boat disagrees saying that you were still clear astern when she arrived at the two-length zone and that you subsequently obtained the overlap, rule 18.2(e) states that if there is “reasonable doubt,” it shall be presumed by the sailors that the overlap was not obtained in time. Similarly, if it goes to a protest hearing and the protest committee has “reasonable doubt,” they shall presume that the overlap was not obtained in time. In other words, in a protest you will have to satisfy the protest committee that there is no doubt that you obtained the overlap in time.

By the same token, if you have an overlap on an outside boat at say five and then four boat-lengths away, she will be required to give you room under rule 18.2(a) unless she pulls clear ahead before reaching the two-length zone. If she claims to have “broken” the overlap just before she reached the two-length zone, but you disagree saying that you were still overlapped when she reached the two-length zone, then it is her who must satisfy the protest committee that there is no doubt that the overlap was broken in time.

Satisfying the protest committee is generally very tough to do as it is usually one word against the other. Hails to each other regarding the overlap situation as the boats near the two-length zone are very helpful to the point that they are almost expected by good protest committees. Also, witnesses can be very useful, particularly independent witnesses who were positioned exactly at the two-length zone and in a position to determine overlaps.

“Does the inside boat have to call for room?”

No. When you are on the inside while rounding or passing a mark or obstruction, you are not required to call for room. ISAF Case 41 reads, “QUESTION 2: Does BW have to claim room to pass to leeward of A, or would BL risk disqualification by not automatically giving room? ANSWER 2: BW is not required to hail for room, although that is a prudent thing to do to avoid misunderstandings. Rule 18.2(a) requires BL to give room to BW when they both pass to leeward of the obstruction.” In US SAILING Appeal 7, SL and SW were passing astern of another starboard-tacker that had been clear ahead. In this case SW didn’t know SL was there or that she was even entitled to room at the obstruction. She bore off inadvertently and hit SL. The Appeals Committee stated, “The fact that [SW] was unaware of [SL’s] presence in no way changed [SL’s] requirement under the rules or justified her in not giving [SW] room to clear the obstruction.” Clearly, outside boats must be aware at all times to be sure they give each inside boat enough room and they keep clear when required to.

“What should I do in the situation where I’m entitled to room but when I’m about a boat-length away from the mark it becomes obvious that the outside boat isn’t leaving me enough space to fit between her and the mark?”

At the moment it becomes clear that the outside boat is not going to give you room, rule 14 (Avoiding Contact) requires you to avoid hitting her if reasonably possible. This may result in you not being able to round or pass the mark on that approach. Though the outside boat’s rule breach caused you to sail on the wrong side of the mark on that approach, it hasn’t prevented you from ultimately rounding the mark correctly as required by rule 28.1 (Sailing the Course), i.e. she didn’t compel you to break rule 28.1; therefore, unfortunately, you are not entitled to exoneration under rule 64.1(b) (Penalties and Exoneration). You must circle around and try again. You should certainly win your protest against the outside boat, but there is nothing the protest committee can do to compensate you for the distance/places lost while making a second try to round or pass the mark.

Of course, if you do choose to hit the outside boat and force your way in between the outside boat and the mark, you can be penalized under rule 14 (Avoiding Contact) only if the contact causes damage or injury. Remember, that if you hit the mark you have broken rule 31.1 (Touching a Mark). But you can be exonerated under rule 64.1(b) (Penalties and Exoneration) if the protest committee finds that the outside boat compelled you to touch the mark by failing to give you enough room.