by Chris Chesley » Thu Jan 10, 2013 4:47 pm
Cap10
Offshore it's a different ballgame. If I see them, I go around them. It's the see them that is difficult. Normally, at sea, it was (is?) customary to run on a 24 mile radar range. Works good for big ships. Quiet night and sea, you can pick 'em up at 24 miles, certainly by 16 or 17 miles. At a closing speed of 30 plus, you still have plenty of time to maneuver if required. Small boats on the other hand....
Small boats are lucky to be picked up at 7-8 miles by radar. Even then, it's likely a small intermittent return. Running lights seldom show up that far although it's possible, especially on a dark night. (moonlit nights are the worst for visual acquisition since the brightness of the moonlight makes all but the strongest lights hard to see). The problem comes when the radar has to use the sea clutter adjustment to dial down all the sea return. You either dial it out or it overwhelms the first 3-4 miles from the ship. This gives the watch officer a 'window' of 3 or 4 miles to catch sight of the intermittent return on the screen. Again, at 15-16 knots, that's a 15 minute maximum window of opportunity to be seen by the watchstander--who also has to make the coffee, fill out the logbook, answer the engineroom phone, pick his nose and, oh, yeah, look out the window and into the radar hood. The odds grow long that you'll be seen.
The advent of AIS is a lifesaver--for the yacht. Assuming the bridge radio volume didn't get turned down, you can now call the specific ship and alert them to your presence. It's a dramatic improvement.
One other thing for the small boat guy--learn about ranges and ship's range lights. They'll tell you a ton about whether or not you're at risk as will a constant bearing. Don't count on the big guy to avoid you. Be proactive, alert and savvy, stay out of their way. Death really can't be appealed even if you're right!