134 seamanship secrets
Will that vessel off our starboard bow cross ahead or astern of us? How about
the large power vessel coming toward us down the channel? Will we pass safely,
port-side to port-side? Use the following techniques to determine if another
vessel will cross ahead or astern of you or if the threat of a collision exists.
To determine bearing drift and drift rate:
Stanchion bearings. Use a stanchion or other fi xed point to sight the other
vessel. Watch the way the vessel drift s relative to the stanchion. Does it
appear to drift to the left , to the right, or stay steady? If drift ing, is its rate
of drift fast or slow?
Compass bearings. Use your handbearing compass to shoot the bow of the
vessel. Wait 30 seconds and shoot it again. Repeat the procedure one more
time. Note whether the bearing drift s to the left or right.
In either of the above cases, if the bearing drift s toward our bow, the other
vessel will cross ahead of us. If the bearing drift s toward our stern, it will pass
astern of us. And if the bearing has little to no drift and remains constant, a
risk of collision exists.
DOES A RAPID DRIFT RATE EVER INDICATE DANGER?
Rule 7 in the Navigation Rules for International and Inland Waters off ers examples
of what you use to determine if a risk of collision exists. For instance, it cautions that
drift bearings could change rapidly in three cases and still result in a collision:
Q Extremely large vessels
Q Vessels close to you
Q When you approach a vessel that is towingTo track large or close vessels with drift bearings, pick a prominent point on
one end of the vessel. Shoot only this point each time you take a bearing. Do
not hesitate to take defensive action if needed (see more on this below). We will
discuss collision avoidance strategies for tugs with tows later in this chapter.
ACTION STEPS AND OPTIONS TO KEEP YOU SAFE
Mariners always have two action steps to avoid a collision:
Change course: Come right or come left
Change speed: Slow down (or stop) or speed up
Choose one or both action steps to control the situation. Take action
earlier than you think necessary. Th at way, if things don’t work out as
planned, you have time to try something else.
If you change course, alter your course 60 to 90 degrees or more. If you
increase or decrease speed, do so in a dramatic way. The goal is to make any