Thanks to Dirk for finding my deliberate
mistake and to JK for clarifying the difference between combined sidelights and combined tricolour. Aplogies to Tue also.
However, this prompted me to refresh my knowlege of vessel lighting. Here is part of Rule 23 of the International Regs. for Preventing Collisions at Sea. The omitted bit it for vessels over 12mts. See what you make of this.
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Rule 23
Power-driven vessels underway
(a) A power-driven vessel underway shall exhibit:
...... for vessels over 12mts....
(c)
(i) A power-driven vessel of less than 12 metres in length may in lieu of the lights prescribed in paragraph (a) of this Rule exhibit an all-round white light and sidelights;
(ii) a power-driven vessel of less than 7 metres in length whose maximum speed does not exceed 7 knots may in lieu of the lights prescribed in paragraph (a) of this Rule exhibit an all-round white light and shall, if practicable, also exhibit sidelights;
(iii) the masthead light or all-round white light on a power-driven vessel of less than 12 metres in length may be displaced from the fore and aft centreline of the vessel if centreline fitting is not practicable, provided that the sidelights are combined in one lantern which shall be carried on the fore and aft centreline of the vessel or located as nearly as practicable in the same fore and aft line as the masthead light or the all-round white light.
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Now, check out (iii) again. It seems to me that, if you displace the all-round white off the centreline and, say, put it on the A-frame you then can ONLY use a combined side light. Further, this combined light must either be at the centre of the vessel or, as near as possible, directly below the white.
That's going to make the 1mtr. vertical separation a bit tricky too.