As judge in some of the competitions in VSK, I have observe some different opinion about how to use rights to tack (RTT) when both boats reaching a mark with overlap, sailing on port: (A) windward, (B) leeward.
I have observed that the RTT-call is used in tactical purpose. (A) Have to follow rule 18.2 (b), and definition on mark-room when the first of them reaching the mark-zone. Normally RTT-call is done outside of the mark-zone, with intention to enter it, and long time before the point where tacking (in, or in to, zone) is the “only possible solution”.
In normally situation when the boats sailing on port, a leeward boat (B) has two choices to pass a obstruction on either side by rule 19.2(a), one is by rule 20.1 who also overcome all other rules in section (A) and rule 15 and 16. No other rule can prevent 20.1. Boat (B) can choose to:
a). Tack by a RTT–call, OR
b). Go behind, starboard boats coming in his way who become an obstruction and if (A) follow, to give here room by rule 19.
There is also room for misunderstanding when reading the exception about rule 20 who is in section C . Citation: “When rule 20 applies, rules 18 and 19 do not.
Let us dig deeper on this, what doe´s it say and what does this means?
Rule 20 is a safety rule, in purpose to overcome all other rules. Let us call it a rule with absolute preference with the meaning that no other rule can prevent the use of rule and all boats must follow 20.1(b) when receiving a call.
When we come to rule 20.2 we also getting right´s added to the use of rule 20. Rule 20.2 regulates a legal right´s for rule 20.
Here we have our two terms - with distinct differences:
a). absolute preference = obligations
b). legal precedence = right's
Now to the point
To use a rule against another rule, requires that the rule have a legal precedence ower the other rule, and if only use of a absolute preference the other rule is broken, in legally terms.
Rule 18 has a legal precedence over rule 20, and Rule 20 has absolute preference over rule 18 with the meaning that rule 18 newer can prevent to take action by Rule 20.1 (b) when recive a call from Rule 20.1(a), but at same time the caller has no legal precedence to make the call.
Rule 20 is completely change in ISAF 2013, who makes the grund of legal in new way. The biggest difference is that the old obligantion in rule 20.3 now is a obligation part to get the right's to call by the rule 20.1 a),. You could say that rule 20.1a) demands a obligation to be possessed - before it will give you any right's.
The conlusion of 20.1 a). is that Boat (B)-leward must go behind all stb-boats who fetching a mark, and only if (B) has to make a substantial course change or getting hi risk he will get the right to make a call to tack instead. And 18.2b is valid , until the moment the call is done, and able to forbid a call, if not obligation in rule 20.1 (a) accept it - but rule 18.2 is not able to forbid the action a call demands.
Rule 18 is not valid after a call is done, until the tack is finished - rule 20.1 e).
But the major question is, the point where a course change become to bee a "substantial course change"? - Here is no answer in the definitions! My opinion is that "substantial course change" begins at the point of course change where the a tack is a "less" course change as about 90 degr, or more, and also requires a big rudder change when done .
However, this is just a opinion, but in judge-book 39.21f the example of ca 30 degr course change because of a boat pier, was not enought to be definated as a "substantial course change" with righ to make the call by rule 20.1 a). So the keyword is "substantial" who must be quite more then "a big course change" would be.
The major conclusion of the new rule 20 in ISAF 2013-2016 is that more course change is required to get the right's to make a call and leward boat is normally required to go behind a stb boat who is fetching. And if rule 18.2 is applied there is no possibility to use rule 19.2 (a) and make the choice to tack.
CONCLUTION ISAF 2009-20012 and 2013-2016
At zone rule 18.2 (b) are valid. The (B)-leward boat must pass behind boats who fetching if no substatial course change is needed, or risk, else he will brake rule 18.2b at the second he hail, and if he tack in to zone and fetching he will also use rule 20 in aunsportsmanlike manner and by that is a risk to break rule 2. And under ISAF 2013-2016 he will off course break rule 20.1 a) if the situation not did required a "substantial course change" or "if it was a risk" to go behind STB-boats. The choice in Rule 19.2(a) can not "overrule" rule 18.2 (b) who else give the leward boat the two choices if both of the boats are outside the mark-zone.
Rule 19.2(a) normally give (B)-leward choices to pass an obstrucion on either side, but when 18.2 (b) apply the one of choices - to tack - is gone. And then the right's to tack will be given by rule 20.1(a) instead. Thats why it require a "substantial course change" or a "risk" to get right's to hail when one of the boats is in the mark-zone.
Here is a big need of guide-line to definition: Where is the point where a big course change becomes a subtantial course change, because that's, what all is about.
2 FAIR SAILING
A boat and her owner shall compete in compliance with recognized
principles of sportsmanship and fair play. A boat may be penalized
under this rule only if it is clearly established that these principles
have been violated. A disqualification under this rule shall not be
excluded from the boat’s series score.
20 ROOM TO TACK AT AN OBSTRUCTION - ISAF 2013-2016
When approaching an obstruction, a boat may hail for room to tack and avoid a boat on the same tack. However, she shall not hail if
(a) she can avoid the obstruction safely without making a substantial course change,
(b) she is sailing below close-hauled, or
(c) the obstruction is a mark and a boat that is fetching it would be required to respond and change course.
(a) After a boat hails, she shall give the hailed boat time to respond.
(b) The hailed boat shall respond even if the hail breaks rule 20.1.
(c) The hailed boat shall respond either by tacking as soon as
possible, or by immediately replying ‘You tack’ and then
giving the hailing boat room to tack and avoid her.
(d) When the hailed boat responds, the hailing boat shall tack as
soon as possible.
(e) From the time a boat hails until she has tacked and avoided the
hailed boat, rule 18.2 does not apply between them.
20.3 Passing On a Hail to an Additional Boat
When a boat has been hailed for room to tack and she intends to
respond by tacking, she may hail another boat on the same tack for
room to tack and avoid her. She may hail even if her hail does not
meet the conditions of rule 20.1. Rule 20.2 applies between her and
the boat she hails.
20 ROOM TO TACK AT AN OBSTRUCTION / ISAF 2009-2012
20.1 Hailing and Responding
When approaching an obstruction, a boat sailing close-hauled or
above may hail for room to tack and avoid another boat on the same
tack. After a boat hails,
(a) she shall give the hailed boat time to respond;
(b) the hailed boat shall respond either by tacking as soon as possible,
or by immediately replying ‘You tack’ and then giving the hailing boat
room to tack and avoid her; and
(c) when the hailed boat responds, the hailing boat shall tack as soon as possible.
When a boat is taking room to which she is entitled under rule
20.1(b), she shall be exonerated if she breaks a rule of Section A* or
rule 15 or 16.
*= Rule 18 is in section C, who not give exoneration by rule 20.2.
20.3 When Not to Hail
A boat shall not hail unless safety requires her to make a substantial
course change to avoid the obstruction. Also, she shall not hail if the
obstruction is a mark that the hailed boat is fetching.
A boat is fetching a mark when she is in a position to pass to
windward of it and leave it on the required side without changing tack.
Room for a boat to sail to the mark, and then room to sail her
proper course while at the mark. However, mark-room does not include
room to tack unless the boat is overlapped to windward and on the inside of
the boat required to give mark-room.
When a boat approaching an obstruction hails for room to tack before safety
requires her to do so, she breaks rule 20.1(a). However, even if the hail
breaks rule 20.1(a), the hailed boat must respond. An inside overlapped boat
is entitled to room between the outside boat and an obstruction under rule
19.2(b) even though she has tacked into the inside overlapping position.