Collision Avoidance and Offset Marks

Many of you have probably already seen this video of a port-starboard collision at the recent E-Scow Nationals, but I haven't sen much discussion about it online. So here's my take on the situation and what we can learn from it and how such situations might be avoided in future.

As always, all opinions are my own and may be ill-informed, confused, or even downright wrong. So feel to disagree and abuse me in the comments if you are so inclined.



So what do we have here?

A large fleet.

A crowded windward mark rounding.

Boats on starboard bearing away on to a run and raising their spinnakers, while port tackers further down the fleet are still racing upwind towards the windward mark and are crossing the path of the starboard tack boats.

And one of the port tackers collides with a starboard tacker.

It's one of the most dangerous parts of the race course. Everyone knows that port should give way to starboard in this situation, but it's complicated by the facts that the starboard tackers are changing course and the the crew of the starboard tackers are probably busier than they are at any other time on the race course. It's bad enough on the Laser... sheeting out, pulling up the board, releasing the outhaul, maybe resetting the vang if you released it too much at the windward mark, catching the first wave… and I suspect it's even worse on a boat with a spinnaker. So sometimes the starboard tacker doesn't have their eyes out of the boat enough, and the port tacker may see the starboard tacker but isn't sure exactly when she is going to turn and how sharply. I've seen a similar incident in a Laser fleet which put the starboard tack sailor in the hospital.



So what can be done to avoid these collisions?



Options for the sailors

Under Rule 10, the obligation is clearly on the port tackers to keep clear. What options do they have? Slow down, head up, bear away, or tack I suppose.

Bearing way is certainly an option but you had better do it soon enough to be able to pass cleanly ahead of the starboard tacker. The port tack boat in the video tried to bear away but was too late. Tacking wouldn't usually be necessary or even advisable so close to the lay line. Slowing down or heading up are the best possibilities I suppose for avoiding one starboard tacker. But what if there is a whole parade of starboard tackers, as there is in this incident? Do you luff up and wait for them all to pass? You might wait for the whole fleet. Or do you choose a likely looking gap and go for it? It can be a tough choice.

The real lesson is that port tackers should really anticipate this situation and not put themselves in the situation of having to cross a crowd of starboard tackers bearing away to the downwind leg so close to the mark. It's a bit like the old joke about a tourist in Ireland who asks one of the locals for directions to Dublin. The Irishman replies, "Well sir, if I were you, I wouldn’t start from here."



And the starboard tack boats are not entirely immune from the responsibility to avoid a collision. Rule 16.1 says, "When a right-of-way boat changes course, she shall give the other boat room to keep clear." So if a starboard tack boat wishing to bear away sees a port tacker approaching, sailing in a straight line course that would cross to leeward of the starboard tacker if she maintained her course, the latter can't just bear away in front of the port tacker and immediately claim right of way under Rule 10. She has to give the port tacker room to keep clear.

Not that I'm saying that the starboard tacker in this incident changed course in such a way that she infringed Rule 16. But if the port tacker were so minded she could certainly argue a case under Rule 16 in the protest room.

It is interesting that the two starboard tack boats rounding the mark after the one involved in the collision chose to sail high to avoid another port tacker rather than bearing away in front of it. That may have been for strategic reasons (wanting to sail on that side of the downwind leg) but it was probably also smart tactics to avoid any risk of getting tangled up with the port tacker.



Options for the race committee

OK. So I hope we can all agree that having a bunch of port tack close-hauled boats sailing into a bunch of starboard tack boats trying to bear away and raise spinnakers is a situation fraught with risks of collision. The classic race management solution to avoid this problem is to lay an offset mark to define a short reaching leg for the boats after the rounding the windward mark. Then when they do round the offset mark and start to bear away they will be several boat lengths to windward of the port tack lay line and so when the the boats going downwind meet the port tackers they will be settled on their downwind course and not trying to make dramatic changes of course.

It's a good idea and it has its merits. But there is an offset mark in this incident. And still the port tackers are tangling with the starboard tackers as they are bearing away to start the downwind leg.

So what went wrong? Why are the port tackers so close to the offset mark?

Let's be generous and assume that the race committee placed the offset mark correctly (although that doesn't always happen.) Maybe the port tackers overstood the layline? Or perhaps there was a big left shift late in the race? Whatever the reason, this offset mark clearly isn't preventing the problem it was designed to solve.

I have heard talk this year of a different race management solution. Instead of the conventional offset mark defining a short reaching leg, place a mark a few boat lengths directly downwind from the windward mark with the idea that port tackers on the beat must pass it to leeward. (Not sure exactly what language you would use in the SIs to achieve this. No boat on the windward leg may cross the line between the windward mark and the offset mark?)

It sounds as if this variation of the offset mark would achieve the aim of keeping boats approaching on the port tack layline away from boats in the process of rounding the mark and bearing away, as the port tack layline would essentially be the layline to this new "offset" mark.

Has anybody heard of a race committee trying this option? Any experience or views on how well it would work?



And now over to you. Have you been involved in situations like this? Have you seen, or been involved in, similar collisions? What is your plan when you are the starboard tacker or the port tacker? Do we need any changes in the Rules to help make this part of the race course more safe? Are there other things race management can do?