Seamanship_Secrets_185_Tips_-_Techniques_for_Better_Navigation-_Cruise_Planning-_and_Boat_Handling_Under_Power_or_Sail_(Re)_e..

avoiding collision by eye or radar 153

“Your Call, Skipper”

You’re the skipper or most knowledgeable crewmember in each

of the following situations. What actions would you take?

1. You sight a large vessel off your port bow. With binoculars, you are
   able to see the vessel’s green sidelight. You take drift bearings on the
   sidelight and notice a slow drift rate to the right of about 1 degree every
   2 minutes. What action should you take?


2. You are eastbound at 10 knots. You pick up the bow of a westbound
   tanker at 5 miles. Bearing drift is steady. Assuming the tanker is moving
   at 20 knots, how many minutes do you have to maneuver?


3. A tug lies dead ahead in your path, showing three white lights in a vertical
   line. You stop the boat and scan astern for the tow. Even with good visibility,
   you see nothing astern. What do you tell your crew to watch for?


4. Approaching San Francisco Bay in fog, you study the radar to fi nd the
   sea buoy. You see eight contacts within a half mile of where the buoy should
   be. What two steps would you take to identify which contact is the buoy?


5. When plotting a contact on the radar scope, what four questions
   must you answer to determine the risk of collision?
   Answers


6. You are the stand-on vessel, but you must take action because of the
   approaching vessel’s slow bearing drift. Slow down to accelerate the drift
   rate. Allow the vessel to cross ahead of you. Continue to take drift bearings
   to make sure it drifts to the right. Proceed only after risk of collision no
   longer exists.


7. You have 10 minutes. The relative speed is 30 knots (10 knots + 20
   knots = 30 knots).
   60 minutes ÷ 30 knots = 2 minutes per mile
   5 miles (range) x 2 minutes = 10 minutes


8. Sidelights and stern light. Barges carry navlights low to the water
   because they lack superstructure. The range of these low lights is only
   2 to 3 miles. Raise your height of eye and scan with the binoculars
   just above the horizon.


9. Look for a contact that shows a heading parallel to your heading
   but in the opposite direction. The relative speed of a stationary contact
   must match your actual speed.


10. The four questions you must answer are:
    Q How close will the contact come to your boat (CPA)?
    Q Is this a meeting, a crossing, or an overtaking situation?
    Q How much time do you have to maneuver?
    Q What action should you take to avoid collision?