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Old 15-01-2015, 01:14   #1
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"Safe passing distance"

The IMO COLREGs, in Rule 8, state that "Action taken to avoid collision with another vessel shall be such as to result in passing at a safe distance."

That's just plain common sense. But, are there any rules of thumb about what constitutes a "safe passing distance"? (Say I'm in a <15 m sailboat on the open seas, so I'm probably mostly concerned with larger ships, if anything.) I realize that there is a largely subjective component to this, but I was wondering if there is any general consensus. What about avoiding visible sea ice/icebergs?
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Old 15-01-2015, 02:40   #2
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Re: "Safe passing distance"

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Originally Posted by ecamphunk View Post
The IMO COLREGs, in Rule 8, state that "Action taken to avoid collision with another vessel shall be such as to result in passing at a safe distance."

That's just plain common sense. But, are there any rules of thumb about what constitutes a "safe passing distance"? (Say I'm in a <15 m sailboat on the open seas, so I'm probably mostly concerned with larger ships, if anything.) I realize that there is a largely subjective component to this, but I was wondering if there is any general consensus. What about avoiding visible sea ice/icebergs?
I'm not completely sure what you mean regarding icebergs, but in realtion to ships this is a judgement call.

Traversing in front of a large ship really should be done at a long distance, if at all possible. The reason being that those folks on the bridge of hte large ship simply can see your boat if you're, say, 200 meters in front of them. You'll simply disappear under their bow (well it will get their blood pressure up, that's for certain).

Assuming it is possible, "safe distance" means the other ship will see, and realize, that you have taken evasive action and therefore they are completely aware of your intentions - that way they won't also take action, potentially getting you back into a collision situation

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Old 15-01-2015, 03:24   #3
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Re: "Safe passing distance"

This is a really good question. A lot of sailors have no idea at all what safe passing distances look like to ships, which results in a lot of dangerous confusion.

In general, ships consider that in open water if another vessel is predicted to come within less than one mile, that is a close quarters situation, which you would usually avoid. They usually try to detect the presence of another vessel at no less than 10 miles and be aware of what the CPA with that vessel will be (Closest Point of Approch -- calculated with AIS or ARPA). They will usually manuever to correct a CPA which is too close at 10 to no less than about 5 or 6 miles.

If they haven't maneuvered by 4 or 5 miles, then you can feel free to maneuver yourself, if you're the stand-on vessel and were waiting for the ship to make the first move.

You should never, under any but the most extraordinary circumstances, pass ahead of a ship less than one mile (better two or three). Passing behind is much less critical -- a couple of cables can be enough if both vessels are on steady course and speed (not blown around in weather, for example, or you are hard on the wind so with varying course) AND you have a good means of calculating CPA (that is, AIS).

There are a lot of good threads on here about collision avoidance procedures.
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Old 15-01-2015, 03:50   #4
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Re: "Safe passing distance"

(Hi all - first post)

Yes I agree with that. NEVER pass close ahead of a stand on vessel. Always take action early (it says that in the Rules too).

Having said that I've only twice been given way to by a commercial vessel: once by the Portsmouth to Wooton ferry in a gale when he thought we were having trouble (we weren't!) and once in mid-Channel by a bulk freighter. It depends what they consider to be a 'narrow channel.

Do bear in mind that many large ships, particulalry car carriers and container ships, have their bridge aft and a lot of metal in between the lookout (if any) and the bows. They therefore have a blind area extending up to two or three cables ahead of them. If you're in that they won't know you're there - and they won't feel the bump.
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Old 15-01-2015, 03:57   #5
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Re: "Safe passing distance"

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Originally Posted by Seasick Steve View Post
(Hi all - first post)

Yes I agree with that. NEVER pass close ahead of a stand on vessel. Always take action early (it says that in the Rules too).

Having said that I've only twice been given way to by a commercial vessel: once by the Portsmouth to Wooton ferry in a gale when he thought we were having trouble (we weren't!) and once in mid-Channel by a bulk freighter. It depends what they consider to be a 'narrow channel.

Do bear in mind that many large ships, particulalry car carriers and container ships, have their bridge aft and a lot of metal in between the lookout (if any) and the bows. They therefore have a blind area extending up to two or three cables ahead of them. If you're in that they won't know you're there - and they won't feel the bump.
Never pass close ahead of any ship -- safe passing distance doesn't vary according to who is give-way and who is stand-on!


As to ships giving way to you -- there's been a lot of discussion about this. They actually give way to you all the time, you are just not aware of it. That is because their decision-making horizon is much longer than yours. They typically alter course about 10 miles out, often before you've noticed them (especially if you don't have AIS).

They almost always give way when they are supposed to -- our ability to perceive this is a different question.


Your point about visibility from a ship's bridge is correct and is very important.
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Old 15-01-2015, 04:11   #6
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Re: "Safe passing distance"

Greetings and welcome aboard the CF, ECP & Steve.
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Old 15-01-2015, 05:14   #7
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Re: "Safe passing distance"

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Greetings and welcome aboard the CF, ECP & Steve.
Ditto on the welcome to CF you guys!!!

ecamp- I give ice a passing margin of no less than 20 deg lat...

Steve - Can't wait to see more of your posts...
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Old 15-01-2015, 05:21   #8
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Re: "Safe passing distance"

If you're racing, of course, all bets are off and you go as close as you think you can get away with. Which is why the insurance premiums are higher.

Thanks for the welcomes.
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Old 15-01-2015, 06:09   #9
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Re: "Safe passing distance"

It's all relative and based on the circumstances that you're in, unfortunately. At sea, as Dockhead pointed out, it's best to err significantly on the side of caution, particularly when encountering commercial traffic.

In coastal areas, outside of designated channels and shipping lanes, it really comes down to COLREG and how close it gets cut is a matter of specifics and judgement.

In that situation if I'm the stand-off vessel and am crossing paths with another boat under sail and have an adequate degree of confidence that they will behave as the stand-on vessel, I'll pass within a boat length of their stern. Would I do that at sea? Absolutely not unless I was racing.

In the Chesapeake, where there is a significant amount of commercial traffic headed to Baltimore, it's shocking how often you see people doing stupid things, cutting in front of massive ships. It's not uncommon to hear a horn, or see a ship suddenly belching huge quantities of smoke as it does what little it can to try and avoid a collision with some idiot sailor who decides to tempt fate.

This is a bit off-topic, but what irks me more than anything when driving is when someone, deciding to be "polite", elects to give you the right of way when you don't have it. They are creating a dangerous situation where no one around them can predict what anyone else is going to do. Drives me nuts.
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Old 15-01-2015, 06:35   #10
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Re: &quot;Safe passing distance&quot;

Quote:
Originally Posted by Seasick Steve View Post
(Hi all - first post)


Having said that I've only twice been given way to by a commercial vessel: once by the Portsmouth to Wooton ferry in a gale when he thought we were having trouble (we weren't!) and once in mid-Channel by a bulk freighter. It depends what they consider to be a 'narrow
My tendency when operating a commercial vessel is to always or almost always alter to pass safely astern of any kind of close cpa (as determined by sea room) with a pleasure craft.

I make the decision well out before the yacht is even thinking about me so it's not in contravention to the ColRegs.
I do this for my own peace of mind. I find even rudimentary knowledge of ColRegs is so spotty amongst yachtsmen that they're best avoided if possible (spotty as in unpredictable- some of course are very good).

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Old 15-01-2015, 06:46   #11
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Re: "Safe passing distance"

Use your radio. Better yet, use your radio after looking at your AIS (receiver only, not transponder - that's another topic) to determine the name of the vessel you are hailing. Offshore, if the AIS says our CPA is less than a mile in the day or 4 or 5 miles at night, I get on the VHF, hail the vessel, politely say I'm a sailing vessel and ask if they have me visually or on radar or both, and then if it appears our CPA is closer than I prefer, I suggest a minor course correction, that I have figured out in advance, that will open up our CPA. For example, I will propose to fall off 10 degrees to port and ask them to adjust their course 10 degrees to starboard, to open up to a mile or so. At night, if I have made affirmative contact, I am comfortable with a one mile CPA, in the daytime, with contact, a quarter mile or so (although I prefer wider CPAs if possible). I have almost never had a vessel with which I have made radio contact refuse to adjust course for me. Down island, there have been smaller inter-island freighters who have not responded, of course, then I just keep things as wide as I can. But with larger vessels, cruise ships, etc., I've made many, many contacts by VHF and requested and received many course corrections and many more "yes we see you, and will keep an eye on you". This whole business of trying to figure it out, without just getting on the VHF, is baffling to me. If you are at sea you have no business having fewer than two or more operation VHF radios on board, and if you don't have the confidence and presence to use them, you shouldn't be at sea. OK, that's a little judgmental, but its a pet peeve. Also, the vessel being hailed is the name that goes first, the calling vessel second. "Big Ship, Big Ship, this is the Sailing Vessel Liberty". Not "Liberty calling the Big Ship". But I digress, and sound petty. Anyway, any discussion of "how close should I be to a big ship" should include the term VHF.
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Old 15-01-2015, 06:51   #12
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Quote:
Originally Posted by FamilyVan View Post

My tendency when operating a commercial vessel is to always or almost always alter to pass safely astern of any kind of close cpa (as determined by sea room) with a pleasure craft.

I make the decision well out before the yacht is even thinking about me so it's not in contravention to the ColRegs.
I do this for my own peace of mind. I find even rudimentary knowledge of ColRegs is so spotty amongst yachtsmen that they're best avoided if possible (spotty as in unpredictable- some of course are very good).

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This is consistent with what dozens of commercial mariners have told me in various conversations over the years. The big gulf between pleasure sailors and pros is that we think in much shorter distances and have very poor ability to perceive what the ship is doing. This is dangerous.

I have only one question about your post - why would you pass astern? That means I'm passing ahead, which makes me nervous even with a CPA of a couple miles. And makes you more vulnerable to an unpredictable panic maneuver by the WAFI. Wouldn't it be better to pass ahead? Then you have the "weather gauge", so to speak, and when you approach CPA, the WAFI cannot do anything to create a dangerous situation.

If the WAFI is passing ahead, he might wake up and see you only when you're very close, and heave-to, stop, or change course, thinking he is letting you go ahead - unable to perceive that he is actually passing safely ahead if he would only hold course and speed. That can cause a collision which you will already be unable to avoid.

If it's you who are passing ahead, however, no last minute stupidity on the WAFI's part can cause any problem for you.
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Old 15-01-2015, 07:05   #13
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Re: &quot;Safe passing distance&quot;

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Originally Posted by FamilyVan View Post
My tendency when operating a commercial vessel is to always or almost always alter to pass safely astern of any kind of close cpa (as determined by sea room) with a pleasure craft.

I make the decision well out before the yacht is even thinking about me so it's not in contravention to the ColRegs.
I do this for my own peace of mind. I find even rudimentary knowledge of ColRegs is so spotty amongst yachtsmen that they're best avoided if possible (spotty as in unpredictable- some of course are very good).
Since you're here and reading this thread, perhaps you can answer a question for me. Why do so few commercial vessels respond to hails when at sea when there is a CPA issue? Even when you hail them with specific coordinates, with not another ship for 100 miles, they usually don't respond unless you hail them by name. What's up with that?
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Old 15-01-2015, 07:16   #14
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Re: "Safe passing distance"

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This is consistent with what dozens of commercial mariners have told me in various conversations over the years. The big gulf between pleasure sailors and pros is that we think in much shorter distances and have very poor ability to perceive what the ship is doing. This is dangerous.

I have only one question about your post - why would you pass astern? That means I'm passing ahead, which makes me nervous even with a CPA of a couple miles. And makes you more vulnerable to an unpredictable panic maneuver by the WAFI. Wouldn't it be better to pass ahead? Then you have the "weather gauge", so to speak, and when you approach CPA, the WAFI cannot do anything to create a dangerous situation.

If the WAFI is passing ahead, he might wake up and see you only when you're very close, and heave-to, stop, or change course, thinking he is letting you go ahead - unable to perceive that he is actually passing safely ahead if he would only hold course and speed. That can cause a collision which you will already be unable to avoid.

If it's you who are passing ahead, however, no last minute stupidity on the WAFI's part can cause any problem for you.
Very good point. I would try not to be close enough to him to cause panic. I aim to pass astern of him so he doesn't have any trouble interpreting my intentions. I want him to take a quick look and see I'm no risk because I'm passing astern.
It's about non verbal communication.
I won't do anything if I can pass ahead and I know he's not fast enough to catch me.

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Old 15-01-2015, 07:26   #15
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Re: &quot;Safe passing distance&quot;

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Originally Posted by Suijin View Post
Since you're here and reading this thread, perhaps you can answer a question for me. Why do so few commercial vessels respond to hails when at sea when there is a CPA issue? Even when you hail them with specific coordinates, with not another ship for 100 miles, they usually don't respond unless you hail them by name. What's up with that?
I've discussed this on another thread but don't recall the details.
The answer is often complicated. I'll try to answer but my answer will not be comprehensive.
-there is frequently a language barrier. The oow (probably not the Captain or even the chief mate). He may not feel comfortable speaking English.
- a Junior Officer in general may not be comfortable speaking on the radio. Especially if there's a very top down command structure.
-rules. The use of VHF as a method of collision avoidance isn't identified in the international ColRegs (it is however in Canadian and American modifications).
-they may not identify you as a threat as they have much better tracking capabilities (this is a little rude of them in this case- but thats life).
-Some may not like yachtsman very much due to past encounters. Yes- stereo typing isn't very nice, but many sailors are comfortable with not being very nice.

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