On Mon, 14 Feb 2005 09:43:06 -0500, rhys wrote:

On Mon, 14 Feb 2005 04:22:24 GMT, otnmbrd
wrote:

rhys wrote:

Sidebar question: Am I woefully ignorant on radar implementation or am
I correct in assuming that a target heading directly for one's bow
would be invisible to a mizzen mounted radar due to the three-to-four
degree "screen" of the main mast directly ahead?


R.

Quite possibly, IF you where an expert helmsman at all times.

Agreed, and I know what you are getting at. But if seas are flat, wind
is calm, and you are on a misty seaway at dusk/dawn motoring at five
knots under autopilot, I can see where a trawler or small frieghter
doing the same on a reciprocal course would be nearly invisible to you
simply due to the fact that your radar's proximity alarm or "range
guard" or whatever they call it would not go off until the ship on the
collision course was on top of you...solely due to the mizzen
placement.

A person on watch on a calm, foggy night (say a 75 foot high bank of
fog, giving the impression it's clear "enough" overhead, but miserable
all around) *might( hear engine noise or see a dim glow. But with the
terrible watch-keeping on commercial traffic these days, I wouldn't
count on being seen, either.

I suppose the other side of the equation is that a mainmast mounted
radome on a ketch has poor coverage aft, meaning that a ship
overtaking you from dead astern would also be hard to notice in such
conditions, particularly over your own exhaust note.

But such conditions are exactly when one would use radar, no?

R.

The mast is not nearly wide enough to block the smallest radar
antenna. I had a Furuno 1720 mounted on a stern tower for 11 years
without seeing a blind spot, and a Ray SR70 for the last 3 seasons.

The Raytheon is much better than the old Furuno, but mainly because it
is a 20-year later design, making use of digital computer techology. I
expect a new Furuno would be fine also.

My only complaint with the Ray is that its dimmest back-light setting
is too bright. The garmin GPS maounted beside the display at the helm
dims down much lower.

I have bought red gel filters from a theater lighting place which keep
the display from swamping my eyesight on watch.

HTH





Rodney Myrvaagnes J36 Gjo/a


"We have achieved the inversion of the single note."
__ Peter Ustinov as Karlheinz Stckhausen