Friday, September 12, 2014

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?


Litoralis said...

Both the starboard tack boat and the port tack boat in the E-scow incident violate Rule 14. The port tack boat clearly violates Rule 10 and the starboard tack boat may have violated Rule 16.1. The correct course of action for the starboard boat would have been to head up to avoid the port tack boats and then protest them for violating Rule 10, relying on the holding in ISAF Case 50.

The port tack boats seem to have overstood the layline and have to bear off to get to the mark. They're in an even worse situation than approaching a line of boats on the upwind starboard tack layline. The real solution would seem to be for them not to have put themselves in this situation in the first place.

Tillerman said...

Yeah. To keep the post from getting even more long and rambling I chose to omit a discussion of Rule 14, which does apply of course and under which the starboard tacker could be penalized if there was damage or injury.

Doc Häagen-Dazs said...

Sailing in a large fleet:

In the first place, whenever (almost always I hope!) I approach the weather mark on port, I have tacked so as to a fetch a point where my eventual tack on to starboard will put me a smidgen more than three boat lengths from the mark. That's the only safe, smart, and responsible approach. Not the approach used by this offending port-tacker.

A rounding reaching mark after the weather mark is a smart race-management step to make. But it shouldn't be necessary in club racing.

In large fleet this year, I had rounded the weather mark, set my chute, and then was fouled by a port tacker beating his way up to lay the mark. I waved him on. My mistake. Later, in the same race he was again on port and he brazenly fouled me (on starboard). This time I flashed him the red flag and protested his fooking ass out of the race.

Tillerman said...

Fooking ass!

I must admit that when I am going downwind on starboard in the middle of the run I usually steer a course to avoid a port tacker sailing upwind rather than risk a collision. It seems to me that changing my downwind course by a few degrees to take the stern of a port tacker is no big deal. Certainly less of a deal for me than forcing the port tacker to tack would be for him. And a lot less of a big deal for both of us than having some idiot collide with me.

But sometimes when I have rounded the windward mark only to face a swarm of port tackers on the beat, I do confess I resort to shouting STAAAAARBOOOOAAAAAARD and praying that they will all see me and avoid me.

Bursledon Blogger said...

This isn't confined to racing we've been in this situation many times while cruising, port tacker's who leave things too late or just don't know what they should do or hard on the wind on port tack when a load pf racers come screaming down on starboard, the trick is to see it early and get the hell out of the way when we ain't racing

torrid said...

In my mind, it's pretty simple case of port/starboard. I really, really try to avoid coming in on the port layline like that. If I do and can't find a hole, I'd lather take my lumps (figuratively speaking) let a bunch of boats clear before I try to cross. I don't want to screw up someone else's race because of my poor judgement.

On an aside, have you ever raced your Laser on the same racecourse as an E-Scow? Not fun!

Tillerman said...

I don't think I've had that pleasure torrid. Although E-Scows are raced on Barnegat Bay and Lake Hopatcong where I have sailed Lasers.

One scary boat to sail in the company of is the A-Cat (the catamaran not the Barnegat Bay cat boat.) They are so fast and so quiet (and apparently always on the verge of being out of control) that they are on top of you before you know it.

torrid said...

E-scows are large, fast, point high upwind, and sail hot angles downwind. A Laser is just a speed bump for them. Can make for some very hairy mark roundings. In my experience boats that are radically different, such as dinghy/keelboat or dinghy/catamaran, just don't mix well on a race course.

Tillerman said...

Right torrid. And I have been looking in the Rules book but I still can't find the Rule that some of these bigger boat sailors use - the one about how a big boat ALWAYS has right of way over smaller boats at a mark rounding.

Jeremiah Blatz said...

I was in a similar situation in a J24 race. We had just rounded the mark (no offset) and were about to hoist the kite when a boat tacked onto port just a couple boat lengths away, then ploughed right into us. Pit a nice hole in the boat, but fortunately nobody was injured.

My solution is: don't be on the port tack layline! Especially if there's no offset, you don't have any time to prep for the spinnaker host. And, furthermore, you're going to have to weave your way around all the boats coming downwind. It's the same reason you don't immediately gybe after rounding the mark, you suddenly find yourself on port and windward of everyone.

Not sure what the guys in the video were doing overdid on port, but they shouldn't have been there.

Tillerman said...

Quite right Jeremiah. My guess is that there was a left shift after those guys were already on the laying and they carried on sailing high. Look at the boats sailing from the windward mark to the offset mark, they are almost close-hauled, another sign of a late left shift.

R1 said...

It looks a little like both Starboard-tacker and Port-tacker luffed a little at the same time and then, having seen the other luff, both bear away into the collision. Classic. Star-board tacker ceratinly luffed which lulled port-tacker into false sense of security.

In my opinion, Port-tacker should never have driven into that "gap" in the first place. He should have luffed earlier and gone behind, or tacked off. It was up to Port-tacker to find a safe way through.

I'm not sure about Starboard-tacker's responsibility. He was "changing course" by bearing away (which was his proper course) but to luff and then bear away again into the collision? I think he only bore away because he thought Port-tacker was luffing.

Is there an outcome published?

Tillerman said...

No. Haven't seen anything posted about a protest. My guess is that the port tacker did her turns or retired from the race.

Gordon S said...

I like the idea of a offset mark three lengths below the windward mark would hopefully put a damper on the wild optimism of some aggressive port-tackers. It could just be tethered to the mark by a floating nylon cord so it floats down wind (may not work if you have currents or random 120 degree wind-shifts like we had yesterday). The tether should discourage anyone from sailing between the marks.

Tillerman said...

Hmmm. A tether. I like that idea. Maybe you could attach a small floating mark every foot on the tether so it would be more clearly visible? Maybe they could have small explosive charges which would detonate on impact?

/Pam said...

This came through on Facebook from a sailor who was there: Nice puffs were coming in from the left and you had to get up high above lay line to get clear air. Unfortunately that often meant getting up above the offset market and having to come in and find a hole on port tack. I found myself in the same position several times. You just had to hope and pray that the starboard tack boat bearing away at the off-set would cut you a little slack and not bear off into you as they were setting the kite. It was a lot harder than it looks from the drone!

Tillerman said...

Thanks /Pam. That certainly explains how the situation occurred.

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