Collision Avoidance

[thinwater]

Obviously, if we follow COLREGS there should be no close calls. Setting that aside, ships do get too close and they do collide, for a variety of reasons.


Rule 17 says:
(a) (i) Where one of two vessels is to keep out of the way, the other shall keep her course and speed.
(ii) The latter vessel may, however, take action to avoid collision by her maneuver alone, as soon as it becomes apparent to her that the vessel required to keep out of the way is not taking appropriate action in compliance with these Rules.
(b) When, from any cause, the vessel required to keep her course and speed finds herself so close that collision cannot be avoided by the action of the give-way vessel alone, she shall take such action as will best aid to avoid collision. [Note: this includes inaction by the give-way vessel.]
(c) A power-driven vessel which takes action in a crossing situation in accordance with paragraph (a)(ii) of this Rule to avoid collision with another power-driven vessel shall, if the circumstances of the case admit, not alter course to port for a vessel on her own port side.
(d) This Rule does not relieve the give-way vessel of her obligation to keep out of the way.



The most common course alteration diagram for what to do, in extremis, when things get close, is this (Lott, USN, 1947).




The primary principles are:

1. Continue to follow COLREGS if possible. This means most turns are to starboard.
2. Don't turn into danger.
3. Don't turn broadside.
4. Don't increase closing speed (related to 4)

Simple enough. This dates back to WW II and before rule 17.


But is it different under sail? Let's assume that action must be taken in moments, even seconds, and only the helmsman is on deck. Let's assume it is blowing a bit and that the boat is not prepared to jibe or tack.


Do any of the angles change? Tacking or jibing unprepared could leave the boat dead in the water, which is not good, but changing the maneuver, in every case, increases the risk, if only a little. Either you are in a worse position or you are doing something unpredictable.


Also, different source quote slightly different angles, no doubt, for simplicity.





Discuss.

[Kettlewell]

There are so many variables in the real world it is hard to develop hard and fast rules to be followed. In my experience the majority of close calls have been in the fog because we always keep a good watch. That means we are usually under power, because thick fog usually blows away if the wind picks up. Yes, we have altered course many times for vessels that appeared like they might be on a collision course, but most of the time there was no rush. A few times fast powerboats have come too close, but because their approach speed was so great compared to our speed maneuvering was basically out of the question. Never had a collision in almost 50 years of cruising.

[thinwater]

^^ Of course, this is why Rule 17 is flexible. Nope, never had a seriously close call.


The question is how does having sail up change your reactions. For example, you have a chute up on port tack, and the required course change is to starboard. Very like this will result in an unplanned jibe. How does that change you thinking?


For example, you are on port tack with the chute up, and suddenly there is a boat closing from two points to starboard. It doesn't much matter whether it is power or sail, because if the rules were being followed you wouldn't be this close. COLREGS says turn to starboard (if you were both power or both sail), but that means an accidental jibe and maybe a broach. But a turn to port will put you right in the dodge path of the other boat, if he does what he should, and now you will be broadside.


Yes, obviously, you should not be in the situation. With enough space you could have altered either port or starboard and avoided the whole kerfuffle. With crew you would jibe away. But that is not the question.

[Kettlewell]

For example, you are on port tack with the chute up, and suddenly there is a boat closing from two points to starboard. It doesn't much matter whether it is power or sail, because if the rules were being followed you wouldn't be this close. COLREGS says turn to starboard (if you were both power or both sail), but that means an accidental jibe and maybe a broach. But a turn to port will put you right in the dodge path of the other boat, if he does what he should, and now you will be broadside.

Depends on a lot of things. I don't cruise with a chute, so a lot easier to jibe for me, but in this situation described I would take a look at the boat approaching--small and nimble I would have to assume they will alter course. Big and not nimble I might try to call on the VHF first. In an emergency, I would probably crash jibe to starboard rather than go to port, but again it depends on the speed, what's to port and starboard, and lots of things. Again, in my experience these situations are very rare. Usually we see each other miles away and take appropriate action.

[sailorboy1]

you turn to put your boat in a safe position. If you have time to be thinking other "stuff" consider yourself lucky!!!!

[ChrisJHC]

Changing course is only one of the response actions available.
You can also change speed (which in a yacht usually means slow down).

And, of course, the requirement to generally turn to starboard only applies to two power vessels.

[fxykty]

I’m not sure I understand the need to discuss sailing vs motoring - the same collision avoidance rules and techniques apply. A sailing vessel will want to be more proactive (and early) as big changes of course can mean tacking or gybing or significant trimming changes to maintain control and/or speed. Slowing down is also a good technique if that’s enough to avoid the collision situation - downwind depowering is more difficult though. Maintain situational awareness and be proactive, not much else to say.

[thinwater]

Originally Posted by ChrisJHC

Changing course is only one of the response actions available.
You can also change speed (which in a yacht usually means slow down).

And, of course, the requirement to generally turn to starboard only applies to two power vessels.

Remember, this discussion is AFTER you have time to do standard COLREGS stuff. Bad viability or stupid stuff has already happened. Done. Rule 17 only applies when action by stand-on vessel is required because either the give-way vessel is not responding or their actions will not be enough. The very last moments.

Changing speed has been discussed. In most cases slowing reduces maneuverability more than it helps. With power boats they typically cannot turn and reverse effectively at the same time, because turning depends on prop wash over the rudder. This is also true to some extent with most sailboats. However, I agree that is some circumstances (narrow channels) it my be the best choice. I recall one emergency stop (boat cut across channel for no reason).

In fact, the sail/power thing barely matters, because the power boat did not give way. Perhaps there was fog. But PLEASE make arguments regarding when you would be better off doing something DIFFERENT than the graphic shows and explain why. If it is truly last moment, Sailor Boy nailed with with "turn to put your boat in a safe position." That is all there is time for.

Imagine that your are with a boat length or a few and it does not seem the other boat is going to turn. There are very few situations where even the ugliest crash jibe isn't better than finding yourself broadside.

The other take-away should be that you should ALWAYS be ready to tack or jibe. Working sheets and guys should always be flaked, ready to run.

[thinwater]

Let me give a real world example. This has happened to me both up and downwind. Imagine a popular sailing area (Annapolis, MD in summer) where all of the talk about avoiding miles away is just silly; you don't make serious adjustments until 200-300 yards at best. Because of this, COLREGS really matters, as does standing-on when you are supposed to. If everyone gave-way the result would be a sidewalk shuffle and more collisions. I'm sure most harbors are like this for ships.


This was about 35 years ago. I try to avoid good stories.


I was sailing to weather on starboard tack. 10 knots in a fast, light catamaran. I saw a port tack boat 200-300 yards away (about 80-90 seconds if you are both sailing fast). Both boats had laminate sails, were well trimmed, and looked "racy". I could have tacked away, but there was another starboard tack boat to windward, parallel to me. I passed him a while ago, but if I tacked and crossed I will be give-way and it will be relativity close. At this moment, standing-on felt safer. The port tack boat appeared to be turning to starboard and the bearing was drawing aft. It looks liked he would duck under my transom by 100 feet or more. This is normal in these "racy" water. I guessed he would pass behind the other starboard tack boat too, but that was not my concern.

When the boat was quite close (20 seconds) I realized that the wind shifted and that we were again on a collision course. In fact, the port tack boat did not change course for me, it was only headed. A few seconds later I realized that they had a deck sweeping genoa, no bow watch, and they didn't know (never knew) I was there. At this point the closing speed was about 20 knots, or a boat length per second.

I tacked away FAST, passing with 15 feet. I yelled something loud about "if you can't keep a bow watch, go home, you d__ s___," his girl friend fell off her lounging spot into the cockpit (that was almost worth it), and the helmsman started leaning low looking all around, suddenly realizing what a d___ s___ he'd been.

My lesson was to ALWAYS make sure I can see the helmsman and that I have his attention when it will be close (not that close!). I also keep an air horn at the helm. It has been useful a few times.

Note that my action was in accordance with rule 17 and the graphic. It was not accordance with "standard" COLREGS maneuvers and could only properly be made "in extremis." If I did not believe it was in extremis, the port tack boat could argue that a possible collision was my fault, because I tacked in front of him instead of standing on. But if I had stood on, a 50-foot mono would have cleaved my 1200-pound cat in half and possibly killed someone.

The safest maneuver was to tack away, because it reduced the closing speed and angle. If I had turned to port (easier for me), the closing speed would have increased to over 20 knots, and if he had ducked my transom at the last moment (not unlikely with racers) I would have been dead and nearly 100% at fault. The collision would have been head-on with a 30 mph closing speed (both boats were fast on a reach).

I was ready to tack away. That is what saved the day. Sailing in a crowded harbor was a risk factor.

[Kettlewell]

Your examples are perfect reasons why there can be no hard and fast rules when in imminent danger. If you were to hesitate for a second thinking about what the prescribed thing to do was vs. the safest thing to do you might very well be in a collision. I've sailed into and out of Annapolis enough times to know what you are talking about, and I kept my boat in Newport, RI, for many years. In Newport these situations are exacerbated by the presence of the shipping channel often occupied by a freighter or Navy ship, and/or a cruise ship anchored in the outer harbor. But, as a cruiser, I still can usually avoid close encounters by taking action well before I encounter the racers. Sometimes it has meant traveling a fair bit out of my way. I was almost involved in a slow-motion collision with Australia II shortly before she won the America's Cup. We were short tacking out of Narragansett Bay in our old Phil Rhodes 26-footer, which was pretty quick in light airs. Australia II was slowly gaining on us mainly because she could point higher. We went tack for tack out of the bay until she was right on our stern. We were both on starboard but she suddenly decided to tack below us. The bow man yelled to me to "hold course" but as her bow came across my stern I could see she was going to hit us so I bore off and just barely pulled away. She missed us by 6 inches or so. Pretty exciting for us cruisers! So typically, in that situation you would assume that the overtaking boat would stay clear, but being racers they thought they knew better. If I had tried to tack we might have been OK, but with them pointing higher than us and going faster I think we would have collided. Just a small example of how many different situations there are requiring many different reactions.

[thinwater]

Originally Posted by Kettlewell

Your examples are perfect reasons why there can be no hard and fast rules when in imminent danger. If you were to hesitate for a second thinking about what the prescribed thing to do was vs. the safest thing to do you might very well be in a collision. I've sailed into and out of Annapolis enough times to know what you are talking about, and I kept my boat in Newport, RI, for many years. In Newport these situations are exacerbated by the presence of the shipping channel often occupied by a freighter or Navy ship, and/or a cruise ship anchored in the outer harbor. But, as a cruiser, I still can usually avoid close encounters by taking action well before I encounter the racers. Sometimes it has meant traveling a fair bit out of my way. I was almost involved in a slow-motion collision with Australia II shortly before she won the America's Cup. We were short tacking out of Narragansett Bay in our old Phil Rhodes 26-footer, which was pretty quick in light airs. Australia II was slowly gaining on us mainly because she could point higher. We went tack for tack out of the bay until she was right on our stern. We were both on starboard but she suddenly decided to tack below us. The bow man yelled to me to "hold course" but as her bow came across my stern I could see she was going to hit us so I bore off and just barely pulled away. She missed us by 6 inches or so. Pretty exciting for us cruisers! So typically, in that situation you would assume that the overtaking boat would stay clear, but being racers they thought they knew better. If I had tried to tack we might have been OK, but with them pointing higher than us and going faster I think we would have collided. Just a small example of how many different situations there are requiring many different reactions.

What you did (if I understood you correctly) was a good example of an exception to the graphic. The reason it was a logical exception was several -fold (The graphic says turn to port, because the overtaking boat should turn to starboard, and if you both turn to starboard, you will hit).

• They were actively turning to port, which is the opposite of what COLREGS requires. At that moment you were certain they were turning to port, not starboard as they should.
• You knew that heading up would slow your boat, and that tacking away would put you right on them.
• They had asked you to hold course, further evidence that they were going through with the tack.

Just the kind of discussion I was hoping for. A good logical exception based primarily on the fact that both boats were under sail.

Thanks!

[sailorboy1]

Originally Posted by thinwater

Let me give a real world example.

Let me give you a real example.

It is night and you are sailing on a starboard tack on a reefed main sail.

Suddenly there is a 76' fishing vessel dead ahead of you on a collision course. Boat is on autopilot and you aren't directly behind the helm.

Decide what to do.

You have 10 seconds max!

[Jammer]

Interesting question.

In my experience, the greatest source of frustration while sailing is dealing with vessels that are not, "COLREGs compliant." These may be smaller vessels operated by someone who is simply ignorant of the rules of the road. Or they may be recreational fishing boats or commercial vessels with a sense of entitlement even though they ought to know better.

The difficulty is that there's no way to predict what they're going to do or when they're going to do it. The situation is exacerbated in rivers, narrow channels, around points.

There is no effective way for a vessel under sail to evade a faster power boat that is being operated unpredictably.

[Kijit]

Originally Posted by Jammer

Interesting question.

The difficulty is that there's no way to predict what they're going to do or when they're going to do it. The situation is exacerbated in rivers, narrow channels, around points.

Exactly! This is where being "courteous" can also be a problem. The stand on vessel needs to maintain their course and speed so that the give way vessel can figure out what to do. If the stand on vessel starts turning this way and that, or speeding up or slowing down, there is no way to figure out what is going on and the best action to take. People may think they are being courteous by changing what they are doing, but it just mucks up the works unless there is some advance agreement or it is done way, way in advance so that the action is clear.

[thinwater]

Originally Posted by sailorboy1

Let me give you a real example.

It is night and you are sailing on a starboard tack on a reefed main sail.

Suddenly there is a 76' fishing vessel dead ahead of you on a collision course. Boat is on autopilot and you aren't directly behind the helm.

Decide what to do.

You have 10 seconds max!

Yup, heard your story. As I recall the boat was not lit.

If you are at the helm, turn starboard. If you are not at the helm you collide. I consider sailing at night "restricted visibility", even more so in coastal waters, and thus the helm is always manned. I've encountered unlit vessels numerous times and had to alter course a few times. It's shocking.