When I was refering to "ships", I meant commercial ships, usually well over
60 M. Most of the lamps are 120 Vac. The ships are under IEEE-45, USCG (Code
of Federal Regulations), and ABS (or other certification organization)
rules.

On ships and tugs ("ocean going tug/barge"), the port, starboard, stern,
masthead, and range lights are redundant, with two lights in a vertical
assembly. Both lights have the wiring and filement monitored, and if the
primary light fails, the spare can be switched on.

On smaller masts, 6" to10" pipe, the "upper red", "middle white", and "lower
red" NUC lights are usually sigle, and mounted off the mast to the side.
Anchor lights are also mounted off the side if there is not room on top.
Where the mast is large, mounting two lights is theusual method.

Most of the ("ocean going tug/barge") barge lights are powered from local
batteries with solar panels, and have six lamps with automatic lamp
changers. One light that is not in the rules, is a small directional blue
light, facing aft at the bow (usually behind the range light). The tug pilot
uses this light to locate the boy of the barge at night.

Whether Red over green is necessary, on a sailboat, is up to the master. I
had not though of doing it on my '77 Hunter 30, But I do have all Aqua
Signal series 40 lights, the brightest 12 volt light commonly available.

Pete Albright


"Jim Woodward" wrote in message
om...
Both Pete and otn are right. On the one hand, most large vessels have
spare lights, at least for the major functions (stern, masthead,
sidelights, towing), so what might appear to be a pair of lights are
actually not used at the same time.

But, the US rules, at least, (I can't find an International Rules
citation for this) permit two lights to be used for one all around
light where there's a mast in the way, see 84CFR17 Annex I, paragraph
9 http://www.access.gpo.gov/nara/cfr/w...3cfr84_99.html

Basically, you have to ensure that the two lights appear as if they
are one at a distance of one mile or more by using screens or mounting
them close together.

Jim Woodward
www.mvfintry.com

otnmbrd wrote in message
ink.net...
PeteAlbright wrote:
On ships with "all around" lights mounted close on the mast, it is
common to
have two lights mounted on each side of the mast. Two lights mounted
12"
apart should not be confusing, and while a sail may block a light, it
would
also be illuminated by it.

Pete Albright
Tampa, FL

I'd be careful on this. Although I won't disagree that on some ships,
this is true, due to considerations of construction, this requires
regulatory agreement and is not the norm.
Also, it is quite possible that some may see various signal light
"trees" on either side of a ship mast, which they may mistake for
duplication, wherein reality, they are separate signals for some
specific locale or function.

otn