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Gordon

wrote:
On Sep 18, 10:01 pm, wrote:
On Thu, 18 Sep 2008 16:27:23 -0700 (PDT),
wrote:

If someone has unlimited electrical power, is he likely to keep his
Radar on all the time when he is far offshore? Offshore, far from
anything else with a functioning radar system, what would prevent
someone from detecting a sailboat before a collision. Assume clear
weather.
Sailboats are notoriously poor reflectors. Even with RADAR reflectors
mounted on the mast, they don't always give much of a return.

Far offshore and away from known routes, it's usual to put the RADAR
on the "Watch" setting, which cycles it between standby and transmit
modes. You can set it to wake up and take a look around every 10
minutes, 20 minutes, whatever you want. This is a pretty standard
feature on most RADARS that you find on recreational vessels.

RADAR doesn't use nearly as much power as you seem to think. I sure
don't have unlimited electrical power on my sailboat with a 9.9 hp
outboard alternator as my only battery charger. I still use my RADAR
a lot. I just don't leave it in transmit mode when I'm not looking at
it.

Surely the sailboat would give some radar return before the collision
(assuming it is on). In clear conditions, what might cause somebody
to disregard a radar alarm? How often do radars return false echoes
in calm conditions? Just how "invisible" are most sailboats, say 30'
to radar without a reflector? Would objects such as downriggers or
other things aloft on the boat with radar cause false returns?
I see that some radars can be set to look only in a specified arc and
ignore things elsewhere. I assume that is to avoid looking behind and
concentrate on looking ahead. Why does this matter? Are false
returns enough of an issue to cause someone to only look ahead?

How far offshore and how far from known routes? Far enough and many
don't even turn on lights at night let alone radar!
G