On Wed, 13 Sep 2006 00:49:02 +0100, "Capt. Scumbalino"
wrote:

Goofball_star_dot_etal wrote:

"The one catching up is going on a course of 180 degrees" If they are
to converge "the direction from the beam of the vessel being
overtaken" must be less than 28 degrees.

Whether or not they converge is a function of their current positions, their
courses and their speeds. Have a look at my diagram linked to elsewhere. If
the red boat is doing 1kt, and the green one 100kts, then the green one will
be past the red one - will pass over the red boat's projected course - long
before the red boat gets to the same point.

The direction from the beam has nothing to do with convergence, but is a
means of defining whether the situation is an overtaking one.

Yes, I had a bad brain fart.
It was specified in the question that the situation to be considered
was that they would collide if both boats maintained course and speed.
("if it looks like they're going to hit each other"). Drawing vectors
back from the projected collision point you can say that the faster
("catching up"), 180 degree, boat has to be doing more than 1.45 times
the speed of the other, for it to be within the being overtaken
(white) sector of the 208 degree boat.