Originally Posted by Polux
That makes not any sense saying that. I change always my course when there is a possibility of a close encounter and close for me regarding a big ship is at least 1 nm. I change the course very early and always to pass on the stern of the big ship and I alter it many miles away from that possible encounter, much sooner the big ship would be making any course alteration to avoid me.
I fail to understand how this is not common sense good seamanship practice and a very bad anti collision practice.
It is very bad, very dangerous practice specifically forbidden by the COLREGS, to do as you suggest, unless it's done (a) prior to "risk of collision arising", as defined in the Rules; and (b) done with a large, not small change of course and/or speed which will be evident to the other bridge. You should study collision avoidance some. Both the rules, and practical techniques.
"Prior to risk of collision arising" will be earlier than most recreational sailors can even detect a potential collision, so this condition is hard to fulfill. It will be no less than about 10 miles out, which is the usual decision point for well-run commercial
ships in open water
. If you do your small change of course at, say 6 miles out, and you were the stand-on vessel, what you most likely don't understand is that the ship has already changed course for a safe pass. Your small alteration of course has a 50% chance of screwing up his solution, and since the course change was small, there is significant risk that he will fail to notice it, at least for some time, and this creates a really serious risk of collision, which is why the Rules are written the way they are.
If you are not using AIS, then it takes serious work to determine a risk of collision from 10 miles out. It's pretty much impossible to do it with a HBC from this distance, but can be done with good compass
binoculars, or with radar.
If you are not able to determine risk of collision from this distance, then you must not do any course alterations during the "stand on" phase of the crossing. You are obligated to give the ship the chance to resolve the situation -- and he can't do it if you are jigging around changing course or speed. It is your obligation to hold course and speed for a certain amount of time to allow for this.
At a certain point, if you reasonably believe that he has not taken adequate measures, you get the right to maneuver yourself. Note that you CANNOT determine whether he has taken adequate measure with your bare eyes. You have to use AIS, radar with a decent plot, or very good technique with a HBC. What looks like a collision course with your bare eyes might well be a safe CPA, and you will screw up his maneuver.
If you do determine this, then your manuever MUST be a large, obvious one.