The +/- 25 degree requirement is in Annex I of the COLREGs:Originally Posted by Lucky Dawg
10. Vertical sectorsWhy? Sailboats heel. The side lights shouldn't vanish as seen by another vessel at reasonable degrees of heel.
(a) The vertical sectors of electric lights as fitted, with the exception of lights
on sailing vessels underway shall ensure that:
(i) at least the required minimum intensity is maintained at all angles
from 5 degrees above to 5 degrees below the horizontal;
(ii) at least 60 percent of the required minimum intensity is maintained
from 7.5 degrees above to 7.5 degrees below the horizontal.
(b) In the case of sailing vessels underway the vertical sectors of electric
lights as fitted shall ensure that:
(i) at least the required minimum intensity is maintained at all angles
from 5 degrees above to 5 degrees below the horizontal;
(ii) at least 50 percent of the required minimum intensity is maintained
from 25 degrees above to 25 degrees below the horizontal.
(Note that when the light intensity is reduced to 50%, it's visibility is reduced to 25%, i.e., if the light is visible at 2 miles when viewed straight on, it is visible for only 1/2 mile at 50% intensity.)
It requires brighter lights (or more LED lamps) to project the same amount of light over the less concentrated +/- 25 degree vertical arc. So the lights meeting the standards for sailboats are more expensive to manufacture. If the manufacturer can pawn off motorboat lights onto the sailing community, they make a bigger profit. But if you ever have a collision, you can expect the USCG to go over your lights with a fine toothed comb, and YOU are responsible for installing the correct lights. The manufacturer will shrug off responsibility for the accident saying: "we didn't claim those lights could be used on a sailboat".
If the lights aren't specifically labelled for sailboats and made by a reputable firm that specializes in navigation lights (unlike Dr. LED), expect them to be inappropriate for sailboats.
Reply With Quote