COLREGS and DPS

[IslandHopper]

Originally Posted by Dsanduril

Seems that the easiest thing would be to include a definition of "at anchor" in the rules. Then the rule makers can debate whether or not to include DPS and similar technologies when they are used for station keeping.

This is been debated and has been for a number of years, and will be for a few more yet, there is nothing easy or quick about changing or adding to the COLREGS....

When i did my DP tickets the subject of displaying the vessel status always came up, the instructors even state it's a popular subject, one of the more popular suggestions is AIS navigation status stating vessel Underway on DP, but until it goes through the IMO and all it's mechanisms of recommendations, trails acceptance and implementation, the status of been underway (unless encumbered by RAM) will remain...

Now to be a little pedantic, it's referred to as a DP vessel, not DPS.....

[Dsanduril]

Originally Posted by IslandHopper

Now to be a little pedantic, it's referred to as a DP vessel, not DPS.....

I'll accept that, show's my unfamiliarity. Love these topics that call for more research and learning.

As i think back to other encounters I've had with DP I've passed several cruise ships using DP to hold station while running tenders to shore. All showing normal "underway" status and not NUC or RAM. Again, have treated them as anchored. Seems the rules need to catch up (that's not unusual with newish technology).

[IslandHopper]

DP systems have a whole bunch of excellent features and abilities and a few of them we can and do use in anchorages or just on standby out at sea.

Two of the most useful in an anchorage are the ‘Centre of Rotation’ (COR) and ‘Minimum Power’ functions. When using dynamic positioning, the operator has the ability to alter the point at which the vessel rotates around. Normally this point is located at the Centre of Gravity (somewhere around midships). When a heading change is carried out the vessel will spin “on a dime”, staying relatively in the same position.

When in an anchorage we can offset the COR to the Bow (we can offset it to anywhere we want the vessel to rotate around, even outside of the vessel) we will then approach the anchorage as you normally would, bring the vessel to a stop on the best heading for wind and current, then put the vessel in DP and let it settle down for a while while the operator fine tunes position/heading, once happy that everything is fine and the system is working as required we can then select Minimum Power.

What Minimum Power does is basically allow the vessel to weather vane (rotate) around the COR, the DP system will maintain the position of the COR on the Bow but been in Minimum Power allows the vessel to change heading in relation to the environmental conditions, much like a normally anchored vessel.

So, in normal DP Mode the vessel maintains Position and Heading, which when wind and current changes will make thrusters/main propulsion work harder to maintain position, we have to do this quite often when due to the work been performed the vessel cannot change position and/or heading, in Minimum Power the vessel is free to rotate around it’s COR which means the thrusters/main propulsion are not working as hard, hence the term Minimum Power 😊

So in conclusion, a DP vessel in Minimum Power, in an anchorage, should have roughly the same heading as the rest of the anchored vessels, he just won’t swing around his anchor and instead swing around his COR on his bow……..all assuming there is enough room to swing……but they will still be underway

As for your mention of Cruise ships on DP, one of the main reasons for Cruise ships to be fitted with DP is to prevent damage to the sea bed from ground tackle, after all they usually visit some of the more pristine places on the planet...

[Montanan]

Well one way to find out if she is really underway [or willing to get underway] and a give way vessel is to get within her visual range and set a course directly at her from a stand on bearing [so that you are on her starboard side] and see if she fires up her propulsion system and moves.

A dynamic positioning system should be able to dynamically move a vessel out of the way, not just hold position.

If she is the stand on vessel then by holding her position she is in essence maintaining course and speed albeit with a speed of zero.

She is showing lights that she is underway and not restricted in maneuvering so she should act as such status.

Obviously don't push your stand on status to anything nearing a collision. But what the heck sound your horn with five rapid blasts to make sure they are awake on deck watch.

If there is a kid with a sailing dinghy or a PWC around pay them five bucks to do as I discussed above and see how the mega yacht responds. Give them a hand held horn. Be sure to have your popcorn ready it could be quite the show - a 116 meter yacht giving way to a sailing dinghy. Reminds me of tipping sleeping cows.

[Dsanduril]

Thanks for that, quite interesting. I can say with certainty in this case that minimum power mode wasn't be used, he didn't change heading or position for more than 30 hours. It wasn't much of a problem, except to one other large vessel as all the rest of us peons were anchored in much shallower water.

Very cool technology. There are times I wish I had it. I see several vendors are starting to sell it into smaller and smaller yachts, but I doubt I'll ever want to spend the $ or have the power required.

Along the vein of the original question, I watched him maneuver out of the bay as well. No whistle signals or anything else, he just started rotating in position and then steamed away. It was beautiful to watch. As another vessel, who was treating him as "anchored" because that made the most sense, how am I supposed to know that the vessel that had been staying in one place for 30 hours even though "underway" had suddenly decided to actually be underway?

[deblen]

Originally Posted by Dsanduril

Thanks for that, quite interesting. I can say with certainty in this case that minimum power mode wasn't be used, he didn't change heading or position for more than 30 hours. It wasn't much of a problem, except to one other large vessel as all the rest of us peons were anchored in much shallower water.

Very cool technology. There are times I wish I had it. I see several vendors are starting to sell it into smaller and smaller yachts, but I doubt I'll ever want to spend the $ or have the power required.

Along the vein of the original question, I watched him maneuver out of the bay as well. No whistle signals or anything else, he just started rotating in position and then steamed away. It was beautiful to watch. As another vessel, who was treating him as "anchored" because that made the most sense, how am I supposed to know that the vessel that had been staying in one place for 30 hours even though "underway" had suddenly decided to actually be underway?

He was underway,but not making way for 30hrs. He decided to make way(or change speed) so no signal was required on his part.
You observed all this because you were keeping a proper watch.


Interesting discussion. Len

[Dsanduril]

Originally Posted by deblen

He was underway,but not making way for 30hrs. He decided to make way(or change speed) so no signal was required on his part.
You observed all this because you were keeping a proper watch.


Interesting discussion. Len

Not sure I agree with this. In order to leave the bay he had to complete a 180 degree turn (which he did essentially in place). Regardless of being in place, that means that he was altering course (to starboard in this case). There were other boats underway in the anchorage at the time (including his own 21m tender). By starting to make way he put himself in at least a potential crossing situation with them. While I appreciate the peace and quiet of not having to hear his whistle, at the same time I'm not sure it is the rules-correct action.

If it is the rules correct action then it makes me even more confused by DP. One moment a ship is "underway" but for all intents and purposes is behaving as if anchored or aground, the next, with no announcement or notice he is truly underway. If I was the stand-on vessel, but had politely (or using Rule 2 been required) decided to avoid the vessel and he suddenly decided to change the game, well let's just say my underwear might need changing.

[deblen]

Modify the situation a bit:


The other vessel does not have DP. He is just stopped. There is no wind or tide. He is not moving position. He is displaying normal underway lights/signals. Visibility is unlimited. He is not fishing,NUC,or otherwise encumbered.
You come over the horizon from his starboard side making you the stand on vessel. You obviously have several miles in which to observe & make decisions.
He doesn't move.
What to do?

[deblen]

Originally Posted by Dsanduril

Not sure I agree with this. In order to leave the bay he had to complete a 180 degree turn (which he did essentially in place). Regardless of being in place, that means that he was altering course (to starboard in this case). There were other boats underway in the anchorage at the time (including his own 21m tender). By starting to make way he put himself in at least a potential crossing situation with them. While I appreciate the peace and quiet of not having to hear his whistle, at the same time I'm not sure it is the rules-correct action.

If it is the rules correct action then it makes me even more confused by DP. One moment a ship is "underway" but for all intents and purposes is behaving as if anchored or aground, the next, with no announcement or notice he is truly underway. If I was the stand-on vessel, but had politely (or using Rule 2 been required) decided to avoid the vessel and he suddenly decided to change the game, well let's just say my underwear might need changing.

Good points.

[Dsanduril]

Pretty much the same thing. Treat him as the give-way vessel until such time as it is clear he can't or won't give way, then avoid. If he then suddenly decides to get underway after I've made the decision to stand clear then he's changing course and speed in an unannounced manner.

[deblen]

Originally Posted by Dsanduril

Pretty much the same thing. Treat him as the give-way vessel until such time as it is clear he can't or won't give way, then avoid. If he then suddenly decides to get underway after I've made the decision to stand clear then he's changing course and speed in an unannounced manner.

Yup. I can't see any other safe option in either case-DP or Stopped.
I can't find anything in the Rules that specifically cover this situation of requiring a Stopped vessel to move out of the way of an approaching vessel in open waters. Perhaps someone could show me.


I'm not totally convinced that he is breaking any Rule,just because he is Stopped (but Underway),with his Stbd side facing me.


Probably I'm wrong. Would like to have the appropriate Rule(s) pointed out.


Is it possible the COLREGS do not have a Rule for every possible scenario? / Len

[IslandHopper]

Originally Posted by deblen

Yup. I can't see any other safe option in either case-DP or Stopped.
I can't find anything in the Rules that specifically cover this situation of requiring a Stopped vessel to move out of the way of an approaching vessel in open waters. Perhaps someone could show me.


I'm not totally convinced that he is breaking any Rule,just because he is Stopped (but Underway),with his Stbd side facing me.


Probably I'm wrong. Would like to have the appropriate Rule(s) pointed out.


Is it possible the COLREGS do not have a Rule for every possible scenario? / Len

1. No there is nothing in the rules covering this.

2. As above, so no he is not breaking any rules.

3. Can't point them out as there is none.

4. Correct they don't have rules for every scenario, the powers that be are a lumbering giant with no hope of keeping up with technological changes.

DP has been around for years, i've had my ticket for 15 or 16 now, it's always been the same as far as the COLREGS go and i don't see it changing any time soon, any changes that do come will be more to do with autonomous vessels than DP....

As for....

Originally Posted by Dsanduril

Not sure I agree with this. In order to leave the bay he had to complete a 180 degree turn (which he did essentially in place). Regardless of being in place, that means that he was altering course (to starboard in this case).

He was rotating around his COR so he wasn't changing course, he was changing his heading......and the sound signal for changing your heading is ?