Sunday, 9 March 2008

Windward Gates Rules Analysis | 1

There has been a lot of discussion on several forums and blogs about use of the windward gates at the Etchells Mid-Winters Regatta. I wrote about them in this post. You can find some new material by Jim Porter in Weather the Weather Gate and by Gretchen in Windward Gates? Pro or Con?

There are a number of factors to consider in choosing a path. Tactics, disturbed air, spinnaker setting etc. etc. But also the rules.

I've made a TSS-picture of all the rules involved, and made an analysis of different courses a boat can take at a windward gate, purely from that point of view:
In this first post all boats approach on opposite tacks.

Path A: When a boat chooses this path, it never looses right of way. All other boats have to keep clear. There is 16.1 limitation in position 3 if the other boat tacked inside the zone (but not if the other didn't tack) and a 16.1 limitation in position 4.
Only if you gybe after rounding the mark, you become keep clear boat (RRS 11) to boats approaching on the port lay line.

Path B: You start being the keep clear boat and only very shortly become right of way boat, all the way round the starboard gate mark. Briefly in position 3 the starboard boat is subject to rule 13, and then you are right of way boat. If you have to react in that period, for instance have to luff to avoid him, starboard is breaking rule 13. The only other change you have, is to get an inside overlap while starboard is subject to rule 13. Then you are entitled to room and are r.o.w. leeward boat.

Path C: Also not bad from a rules point of view, but with a nasty twist during the rounding. On starboard you are right of way boat and if you time it right, the port/windward boat has to keep clear. But, if you go trough head-to-wind, before port has to react, your are not keeping clear under rule 13. If port manages to get an inside overlap before you are back on close hauled course, you have to give him room and keep clear as windward boat. If you manage to keep port to windward and keep clear during the tack, you again become right of way leeward boat. Your only limitation is rule 16.1, giving port/windward room to keep clear while you bear away. You best bet is to slow down in position 2, or luff head-to-wind and wait for port to tack before you do. After the rounding, you have to keep clear of the starboard boats approaching on the lay line, whether you gybe or not.

Path D: Approaching on the lay line, you have right of way on boats who have gybed after rounding, but otherwise you are always keep clear boat. Because you completed your tack inside the two boat lengths zone you have to watch out that you don't force starboard boats above close hauled, to avoid you. You also have to keep clear of any starboard boat which manages to get an inside overlap.

In order of preference your best course is path A, then path C, then path B and finally path D.

Next week part 2, boats approaching on the same tack.


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