Clause 13 High Speed Vessel

The masthead light of a high speed vessel may be placed at a height lower than that prescribed in Appendix 1.2(1)(a) if the base angle of the isosceles triangle formed by the sidelights and masthead light, when seen in end elevation, is not less than 27 degrees. In the case of a high speed vessel of 50 metres or more in length, the vertical separation between the foremost and mainmast lights, required by Appendix 1.2(1)(b), may be modified if that distance is not less than the value determined by the following formula: y = (a + 17ψ) C / 1000 + 2 where: 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 in metres;