Is it safe to cross astern of a fast ship in open water with a 180 feet CPA

[Uricanejack]

Originally Posted by Pete7

I disagree, I don't think you will have the opportunity to do this in Stu's example, which I have copied into this post.

You as the stand on vessel and therefore have an obligation, if you attempt to do something else it is likely to cause absolute confusion on board the ships bridge. After all at 4 miles the Ships Captain has probably already decided what he is going to do about the little yacht he can see in the distance. Assuming no other traffic or restrictions you describe in your later post No 71, then the Captain has probably ordered a turn to Starboard to pass astern of you, which is in the process of being carried out. Its just you haven't seen it yet. The Captain will assume you will continue towards the top of the image as the stand on vessel.

Should you alter course half way you could easily end up right in the new track of the ship and give the Captain no alternative. You could end up 180 ft in front on the bows never mind astern of the ship.

Pete

I would tend to agree with Mark.
He has stood on as rqd. The distance is now down to 2 miles. 6 minutes from a collision.

Open water nothing else around on a steady bearing only 2 miles away. I would be wondering if the Captain was down bellow well into a bottle of gin. The greenhorn OOW is on his cellphone to his girlfriend while the quartermaster is chipping paint on the focsle.

Time to start to plan an alternative and time to signal my doubt about the approaching ships intentions. 5 short on my little air horn. supplemented by a light. I might even turn on my radio and give him a call.

Mark turned 90 deg to starboard. Parallel to the ship. until it passes. I cant fault this. If the greenhorn on the Bridge suddenly wakes up and alters. He will still alter to pass astern of the boat.

Other good option would be to stop.

2 bad ideas. Keep on standing on regardless. or Altering to Port.
Is 2 miles the right distance? It is up to Mark.
I might wait a bit longer. Even a ships whistle might not be heard at 2 miles. My air horn? Even so. Not a lot longer.

If you change the situation from open water to confined water or increase traffic I might wait longer than I would in open water. This whole thread is about open water.

The ship will cover
2 miles in 6 minutes.
1 mile in 3 minutes.
0.5 miles in 1.5 minutes.

In many ways the topic of this thread should be how close would you let a ship approach before you would take action?

If you do nothing other than stand on you might find consider yourself lucky if it passes 180 ft away.

[markpierce]

Originally Posted by Pete7

I disagree, I don't think you will have the opportunity to do this in Stu's example, which I have copied into this post.

You as the stand on vessel and therefore have an obligation, if you attempt to do something else it is likely to cause absolute confusion on board the ships bridge. After all at 4 miles the Ships Captain has probably already decided what he is going to do about the little yacht he can see in the distance....

Nah, if the ship hasn't indicated a change of course within several minutes (two miles) from potential collision, it is my "stand-on" duty to alter course/speed to avoid collision.

[evm1024]

Originally Posted by Don C L

Yes, I see, the triangle is shrinking... but remind me again, unless I am a really neurotic racer and there is no one at the helm of said ship, why have I set such a course? When I was very much younger and a lot more stupid I used to see how close I could get to the stern of a passing ship, such as this scenario implies... I probably really pissed off a couple of captains... I still never got near 180'.

probably shouldn't admit that

Well, I have no idea why anyone would try this..... I'm just asking the questions and trying not to taint the thread....

[DavidSaunders]

Six or Seven seconds from collision is not a very large margin of error for safety....
Possible-yes. Legal...maybe. Smart- no.
As has been said, I'd slow way down or alter course to make my intent very clear. Probably radio over if I had any doubt they would observe my intent. Better safe than sorry.
YMMV.
David

[billknny]

Originally Posted by StuM

I find it amazing that 8 people (at this stage) think they can "make it be safe"

Based on what I see happening out on the water, I am not at all surprised that 12 out of 41 people think this can be a safe thing to do.

25% stupid seems about right. But, in their defense, most of the people answering "safe" really do not understand what the situation will look like as it develops. And they have all chosen to ignore the ColRegs.

[Jim Cate]

25% stupid seems about right.

I've met some folks who claimed to have IQs around 100. They didn't seem very bright to me, yet one half of all people (statistically speaking) are less bright than they. Kinda scary,and it doesn't take a tiny CPA approach to get that feeling!

But I do think your final statement about many respondents not visualizing what the stipulated interaction would really look like from either vessel's POV gets down to the basis for some pretty silly claims that have been made in the relevant threads. I think even the boldest of the "big balls" crowd would quail, seeing the behemoth bearing down at them without the bearing changing perceptibly, finally being within stones throw of the bows... gaahhhh!

Jim

[Don C L]

No kidding. At even a mile away a freighter coming at you at 20 knots, and you know it'll be there in a couple minutes, and you know your measly 5 or 6 knots knots ain't gonna get you far (out of the way) in 3 minutes, you will definitely start huffing and puffing into your sails well guess it's like pilots, there are old ones and bold ones, but no old bold ones....

[newhaul]

Vhf to discuss passing .

[evm1024]

Originally Posted by billknny

Based on what I see happening out on the water, I am not at all surprised that 12 out of 41 people think this can be a safe thing to do.

25% stupid seems about right. But, in their defense, most of the people answering "safe" really do not understand what the situation will look like as it develops. And they have all chosen to ignore the ColRegs.

I hear what you say.

Likely One or 2 of the "sure" votes were done in a non-serious way (is that how to say it?).

The rest have not actually internalized just how close to a collision you have to get to make this work. They have extrapolated slow speed close encounters and close encounters in restricted spaces (harbors etc) to a crossing in the open ocean. This projection of experience into an area where they have no experience is what gets them in trouble and what the real message of this thread is.

Question: How many of us thought this was an easy thing to do then on further thought realized just how difficult and risky is in in the real world?

[valhalla360]

Originally Posted by evm1024

Actually:

You are in a boat doing 5kts and there is a ship doing 20 kts about 4 miles away.

We do not know if the boat is under sail or under power.

The question is designed to get us to think about what it actually takes to get close to a ship going 4 time faster than we are.

Not many power boats (even slow trawlers) cruise at 5kts, so the assumption is a sailboat.

If under power or not, it's still a stupid thing to do intentionally...even worse in a sailboat where fickle winds or the ship blocking the wind, could suddenly leave you without power.

I still don't get what useful scenario would have you try this.

[valhalla360]

Originally Posted by StuM

I find it amazing that 8 people (at this stage) think they can "make it be safe"

I suspect those answers were responding directly to the poll question suggesting if you found yourself 180' off the stern, would you survive and or take any damage/injury...

Odds are if you are on a well found boat and are prepared for the wake, you might need a fresh pair of shorts but otherwise, good chance you will be fine.

Others read the OP's follow up comment about intentionally putting yourself in that position. The answer to that correctly assumes, you can't reliably put yourself 180' off the stern and so far the OP hasn't come up with a good scenario for why you do so. It would be very easy to miscalculate and wind up negative 180' off the stern and then I have visions of the boat scene from Indian Jones.

This is a classic case of a poorly written poll. Nothing against the OP but poorly written polls often get strange answers...or worse (and not suggesting the OP is doing so) they can be intentionally written to get a specific answer that is not representative of the populations intent.

[valhalla360]

Originally Posted by evm1024

Actually I think that the poll is quite clear....

Regards

Except it's not:

The actual poll question:
Is it safe to pass astern of a fast ship with a 180' CPA in open water

Your first clarification in the comments section:

I just thought I would take this poll on crossing a fast moving ship in open water.

The question is:

You are in a boat doing 5kts and there is a ship doing 20 kts about 4 miles away.

Your crossing angle is 90 degrees and the boat is about 1 nm from the path of the ship. The ship is 4 nm from the boats path.

Do you think it is safe to attempt to pass astern of the ship with a 180' CPA?

Those are two very different questions and you follow up with several clarifications and modifications without ever providing a scenario where you would want to purposely go so close in open water.
- The actual poll question taken at face value with no indication of why you would be there and you actually did wind up 180' off the stern, odds are you would survive and likely take no injury or damage on a seaworthy boat, so it could be argued you would be safe.
- The second is a simple NO unless you can provide mitigating reasons why you would purposely do this as it would be near impossible to set a speed and course from that distance and predictably arrive 180' off the stern.

The results are fairly predictable. Several people answered the literal question before reading the comments section. Others read the comments section and as a result you got a few saying yes, you would probably safely survive the mistake that put you in the situation while most jumped to the assumption that it's stupid to put yourself in the position in the first place.

[hiebert]

Do you want an answer based on strict compliance with COLREGS or totally from a safety point? A prudent boater needs to look at both angles.

The Query is also not clear. Is you boat a sailboat or a motor boat? If it is a motor boat are you approaching the ship on its starboard side or port side? Remember the ship may also be taking some actions eg. altering course to port or starboard that will affect you. If you can also provide a little drawing of the both vessels approaching it will be easier for the experienced boaters to visualize and comment. Thanks

[Dockhead]

Originally Posted by hiebert

Do you want an answer based on strict compliance with COLREGS or totally from a safety point? A prudent boater needs to look at both angles.

The Query is also not clear. Is you boat a sailboat or a motor boat? If it is a motor boat are you approaching the ship on its starboard side or port side? Remember the ship may also be taking some actions eg. altering course to port or starboard that will affect you. If you can also provide a little drawing of the both vessels approaching it will be easier for the experienced boaters to visualize and comment. Thanks

It looks like this:




The relative speeds determine the geometry of the crossing, and you can see that by 4:1, the ship is approaching from something like 14 degrees ahead of your beam.

[evm1024]

One other way to look at this is to ask:

In what conditions would it BE SAFE to attempt crossing aft of a ship going 20 kts with a CPA of 180' in a boat going 5 kts at right angles to each other in open waters?

I did not specify if it was a sailboat or power boat because it does not change the safety of the crossing.

I did not specify who was stand on because it does not change the safety of the crossing.

I did not specify the sea state, weather, fog etc because it does not change whether the crossing is safe or not (if it is unsafe in ideal conditions). If it is unsafe in clear weather, calm seas then adding in bad weather only increases the risk. Safety is the absence of risk by definition.

I did not specify why anyone would attempt the crossing because it does not change the safety of the crossing.

I did not specify the color of the boat.....

All of my did not's above were written with a light hand with no intent to harm or chastise anyone.