collision avoidance

[Uricanejack]

An HBC accurate to 2 deg “every time”

Damn, I wish I was that good.

I might make a claim for 2 degree accuracy in good conditions, certainly not every time.

[Pizzazz]

Originally Posted by StuM

A compass "measures the bearing" relative to magnetic north*

With a decent HBC or binoculars with built in compass, you should be able to get a consistent bearing to less that 2° every time even if your heading is bouncing around.

You guys are correct that a HBC points to magnetic North. However, if you think about the procedure of taking a bearing, you take a reading of the relative angle between the current heading and magnetic North, which varies significantly if you have a moderate sea. Now, you may think that you are are accurate to 2 degrees by doing some averaging in your head but that is not accurate. You need a computer to do that averaging for you. Most people accept +/-5 degrees measuring accuracy in any sort of decent sea.

I have done this exercise many times, a HBC, a radar, a GPS and an autopilot, comparing and calibrating. If you do not plot it on the radar screen, you need to budget for a big error, specially when crossing shipping lanes. May be bigger boats are more stable.

[Lodesman]

Originally Posted by Pizzazz

You guys are correct that a HBC points to magnetic North. However, if you think about the procedure of taking a bearing, you take a reading of the relative angle between the current heading and magnetic North, which varies significantly if you have a moderate sea. Now, you may think that you are are accurate to 2 degrees by doing some averaging in your head but that is not accurate. You need a computer to do that averaging for you. Most people accept +/-5 degrees measuring accuracy in any sort of decent sea.

I don't know what the heck you're talking about - I look down the bearing and it's steady; with the tiny little card in the HBC, I'm able to interpolate to within a couple degrees accuracy for an absolute bearing, but it's quite easy from a repeatability standpoint to judge if the bearing is steady or not. In that respect the handheld is better than the binos - that compass is prone to tilt error, so tends to be a bit twitchier.

[Thumbs Up]

Originally Posted by Pizzazz

...However, if you think about the procedure of taking a bearing, you take a reading of the relative angle between the current heading and magnetic North....

This is incorrect. You are describing the compass mounted to the boat. With a hand bearing compass you are taking bearings of a distant object and compare them to each other over time. Your heading has nothing to do with the accuracy of the bearing. If the distant object is a ship moving at 20 knots and the bearings are not changing, then you do not have much time! There is no better method! Other than AIS or Radar. You need to change course. You do not want to pass in front of a ship (even though you might have right of way). If something goes wrong they can not stop quickly.

[StuM]

Originally Posted by Pizzazz

You guys are correct that a HBC points to magnetic North. However, if you think about the procedure of taking a bearing, you take a reading of the relative angle between the current heading and magnetic North, which varies significantly if you have a moderate sea.

NO! You clearly have never used a HBC to get a bearing from your boat to another object. You take a reading of the the angle between the line from you to the other boat and magnetic north.


Your current heading is irrelevant.


If the HBC shows 312° Magnetic when you aim it at the other boat, that is the bearing from you to it. If doesn't matter whether you are looking over your bow, beam or stern - that is still the bearing to the other boat.

If you take another bearing to the other boat two minutes later and the bearing is still 312°, then you are on a collision course unless it is paralleling you or moving away.



The beauty of this is that it doesn't matter how much your heading is changing moment to moment. You could be zig-zagging wildly but your overall movement during that two minutes puts you on a collision course.

[KayZee]

Originally Posted by Manateeman

Pick up the radio.
State your vessel type, speed, course and current position.
Wait.

I have frequently received no answer when calling on 16 and 9.



Otherwise, thank you for your thoughtful post.


Kurt

[goboatingnow]

Originally Posted by Manateeman

Radar, AIS, night vision, expensive binoculars...all nice to have.

Everybody at some point will find themselves in a confusing situation.

Pick up the radio.

State your vessel type, speed, course and current position.

Wait.

Believe me. No one who is a licensed professional Merchant Mariner wants to run you over. We have more equipment and experience. You have probably been plotted or observed long before a bad situation is at hand.

I can’t tell you the times I’ve wished a small vessel would just tell me their intentions on the radio.

It’s just this simple.

It’s why professionals radio each other to form an agreement on meeting, crossing or overtaking each other.

You might be asked to show a light on your sails or flick on and off your lights so we know for sure which vessel we are talking to.

Most professional captains will give you information on local issues or weather if they have time. Be courteous. Learn the rules and be willing to give way because they might have some issue on board their vessel.

Communication is the most important factor in avoiding collisions.

Please don’t be embarrassed to ask for help or to say you are confused.

The radio is the most important anti collision tool you have.

Please answer if you are called. Please call if you see me.

We can then confirm who is who and who is going where.

It’s just that simple.

Happy trails to you.

Captain Mark and his Merchant Mariner Manatees

These days many yachts have better equipment then most freighters

At sea they do not watch for sailboats especially at night you’re invisible

They don’t “ plot “ or monitor you

They will in most cases not respond to vhf , in particular you’ll either have to have the vessel name or mmsi or make a dsc call to get comms , the English of some bridge staff is often non existent especially if it’s some late night bridge watchkeeper

If you have the name you most likely have AIS anyway

“Merchant vessel at pos X , Y “ will generally just bring silence

Best thing to avoid collisions , AIS class B

This is based on 30 years of meeting ships at sea in international waters

I use the stanchion method , almost as a second nature , if it looks at all like a contact bearing I use the hand bearing compass

If I have any sea room I make my course change as early as possible irrespective of stand on. My golden rule is “never sail into danger “ the only place I observe stand on is crossing the traffic separation zone in “ La Manche “ ( cause that’s what it is ) and that’s like crossing a motorway sitting on a tortoise !

[chris mac]

Originally Posted by Manateeman

Radar, AIS, night vision, expensive binoculars...all nice to have.
Everybody at some point will find themselves in a confusing situation.
Pick up the radio.
State your vessel type, speed, course and current position.
Wait.
Believe me. No one who is a licensed professional Merchant Mariner wants to run you over. We have more equipment and experience. You have probably been plotted or observed long before a bad situation is at hand.
I can’t tell you the times I’ve wished a small vessel would just tell me their intentions on the radio.
It’s just this simple.
It’s why professionals radio each other to form an agreement on meeting, crossing or overtaking each other.
You might be asked to show a light on your sails or flick on and off your lights so we know for sure which vessel we are talking to.
Most professional captains will give you information on local issues or weather if they have time. Be courteous. Learn the rules and be willing to give way because they might have some issue on board their vessel.
Communication is the most important factor in avoiding collisions.
Please don’t be embarrassed to ask for help or to say you are confused.
The radio is the most important anti collision tool you have.
Please answer if you are called. Please call if you see me.
We can then confirm who is who and who is going where.
It’s just that simple.
Happy trails to you.
Captain Mark and his Merchant Mariner Manatees

Just last week I had a freighter crossing us. I was tracking it as it was the stand on vessel. We would pass .3 of a mile in front of it. Closer than I like so I increased speed to put it at .5 miles.
He then altered course up 25 degrees which put our CPA at 250 feet!!
I hailed on 16 and 13 multiple times, no response (by name)
I altered 40 degrees and slowed to allow him to pass.
After he passed he corrected back, plus 10 degrees. That new heading would have put close to a mile between us if he had done it in the first place.
So no, the commercial boats don't always answer, and can be in fact dangerous

[Dockhead]

Originally Posted by goboatingnow

These days many yachts have better equipment then most freighters

At sea they do not watch for sailboats especially at night you’re invisible

They don’t “ plot “ or monitor you

With respect, this is absolutely untrue. Ask any professional mariner; read the forums on GCaptain. It would be totally unprofessional for them to not "plot" and "monitor" you as carefully as any other traffic -- their job is to get to the next port safely and without accident, and running down a yacht would cause horrible problems, months or years of inquiries, career damage -- believe me, they don't want that.

This is one reason why it is important to follow the Rules and stand on when required -- they WILL be maneuvering as required, in almost all cases, and you can screw up their manuever if you maneuver unpredictably and not in accordance with the Rules yourself. Preventing unpredictable chaotic maneuvering is one of the primary purposes of the Rules.


Talk to any professional mariner -- they do want you to stay out of their way, but only when you can do that in compliance with the Rules. Otherwise, the main thing they want from us is to FOLLOW THE BLOODY RULES! They HATE our improvised, erratic deviations from the Rules based on our own made up ideas -- that is exactly why they call us WAFIs.

Originally Posted by goboatingnow

. . . Best thing to avoid collisions , AIS class B

Agreed.

Originally Posted by goboatingnow

. . . My golden rule is “never sail into danger “ the only place I observe stand on is crossing the traffic separation zone in “ La Manche “ ( cause that’s what it is ) and that’s like crossing a motorway sitting on a tortoise !

You should NOT be standing on whilst crossing a TSS. If you find yourself doing that, you have violated Rule 10!

You SHOULD be standing on in all other cases where you are the stand-on vessel. So you're doing it exactly backwards. The only time you are free of the obligation to stand on is when you are able to maneuver so early that you can do so before the risk of collision arises.

This rule is not optional!

[Dockhead]

Originally Posted by chris mac

Just last week I had a freighter crossing us. I was tracking it as it was the stand on vessel. We would pass .3 of a mile in front of it. Closer than I like so I increased speed to put it at .5 miles.
He then altered course up 25 degrees which put our CPA at 250 feet!!
I hailed on 16 and 13 multiple times, no response (by name)
I altered 40 degrees and slowed to allow him to pass.
After he passed he corrected back, plus 10 degrees. That new heading would have put close to a mile between us if he had done it in the first place.
So no, the commercial boats don't always answer, and can be in fact dangerous

Although they are professionals, they are human, and do screw up sometimes.

But what you encountered might not have been a screwup. Remember you are not necessarily the only other vessel nearby. He might have been maneuvering to avoid a different vessel. Sometimes it is not possible to simultaneously give way to two or more different vessels, which is one more reason why the stand-on vessel must always be prepared to maneuver itself. You have the RIGHT to maneuver yourself once you have a reasonable doubt about his intention to do so. But you are obligated to first give the stand-on vessel a proper chance to resolve the situation himself.


The situation you describe does not sound "dangerous". You had a good maneuver, and you executed it as you were required to do under the Rules, and you passed safely. It does not matter who executes the maneuver -- what is important is that maneuvers are done at the right time and in accordance with the Rules. If even only one vessel is following the Rules, there will be no collision. That is the genius of the Rules.

[goboatingnow]

Originally Posted by chris mac

Just last week I had a freighter crossing us. I was tracking it as it was the stand on vessel. We would pass .3 of a mile in front of it. Closer than I like so I increased speed to put it at .5 miles.
He then altered course up 25 degrees which put our CPA at 250 feet!!
I hailed on 16 and 13 multiple times, no response (by name)
I altered 40 degrees and slowed to allow him to pass.
After he passed he corrected back, plus 10 degrees. That new heading would have put close to a mile between us if he had done it in the first place.
So no, the commercial boats don't always answer, and can be in fact dangerous

Correct , never ever trust merchant shipping to see you or respond correctly , the only way to trust commercial shipping is after you confirm passing arrangements by radio , if you cant never “stand on into danger “

My experience is most international commercial shipping ignores yachts and will plow on regardless


Here’s a recent one

Of the cost of Atlantic France in Biscay in November , over the horizon , a big bulk car carrier , the quick stanchion bearing confirmed the potential for close quarters , a quick glance at the chart showed his likely heading was Bilbao .

Out with the hand compass , yep , close quarters

I’m sailing , but hey no biggie , adjust course to clearly pass under his stern

5 mins later VHF burst into life

“ sailboat at xxxx” , thank you capt for changing course , we were just about to bring the second steering motor online and reprogram the autopilot , saved us a bit of work , have a good watch “

“ no problem , It’s a sailboat , I’m not in a hurry , good watch , out “

[Off Trail]

A question that sort of fits in this thread: I've been using a lensmatic style hand compass for quite some time. (It's what I had when getting started cruising).

It works well, a bit fiddly but plenty accurate. Any advantage to the marine style "puck" compass that you think might make it worth picking one up?

[Lodesman]

Originally Posted by chris mac

Just last week I had a freighter crossing us. I was tracking it as it was the stand on vessel. We would pass .3 of a mile in front of it. Closer than I like so I increased speed to put it at .5 miles.
He then altered course up 25 degrees which put our CPA at 250 feet!!
I hailed on 16 and 13 multiple times, no response (by name)
I altered 40 degrees and slowed to allow him to pass.
After he passed he corrected back, plus 10 degrees. That new heading would have put close to a mile between us if he had done it in the first place.
So no, the commercial boats don't always answer, and can be in fact dangerous

Um, 3 cables ahead equals a CPA of half of that on the bow, so your speed change, which would probably not show quickly on ARPA and regardless would have been within his comfort zone on the bow. Why would you not take his stern? The rule is quite clear in this:

15(a)
When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her own starboard side shall keep out of the way and shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel.

[Lodesman]

Originally Posted by goboatingnow

My experience is most international commercial shipping ignores yachts and will plow on regardless


Here’s a recent one
“

Your anecdote completely contradicts this statement.

[Lodesman]

Originally Posted by Dockhead

Although they are professionals, they are human, and do screw up sometimes.

But what you encountered might not have been a screwup. Remember you are not necessarily the only other vessel nearby. He might have been maneuvering to avoid a different vessel.

The situation you describe does not sound "dangerous". You had a good maneuver, and you executed it as you were required to do under the Rules, and you passed safely.

It wasn't a screw-up; they were clearly acting in accordance with rule 17(a)(ii). Chris mac wasn't acting in accordance with the rules, see above.