ANNEX I. Positioning and technical details of lights and shapes
(a) The masthead light of high speed craft may be placed at a height related to
the breadth of the craft lower than prescribed in paragraph 2(a) (i) of this annex,
provided that the base angle of the isosceles triangles formed by the sidelights
and masthead light, when seen in end elevation, is not less than 27°.(b) On high sped craft of 50m or more in length, the vertical separation between
foremast and minmast of 4.5m required in paragraph 2(a)(ii) of this annex may
be modified provided that such distance shall not be less than the value
determined by the following formula:
y = (a + 17T)C + 2
y is the height of the mainmast light above the foremast light in metres;
a is the height of the foremast light above the water surface in service condition
T is the trim in service condition in degrees.
C is the horizontal separation of the masthead lights in metres.