Don't think there was any question that the sailboat was 'seen'.

''Both the submarine and the Coronado issued warning signals to the
sailboat, the Navy said, and the Coronado took evasive action in order to
avoid a collision.''


BTW, why does bob**** think this story is funny?

Scotty


"Shen44" wrote in message
...

The sailboat was small yes... but it still should have been
picked up
on radar. Somebody did a major F-up.

Having spent a few years on the bridge of a naval vessel I can tell you
that
sailboats often don't show up on radar. 'Course it's been a few years
for
me, and maybe the Navy's radar has improved since my time.


If that sailboat didn't show up on radar, it wasn't turned on. However,
the
"Mark I" eyeball should have been working well, considering all the people
on
"lookout" aboard a USN ship running the channel.

I've never used "big ship" radar and I don't now the specs for them, so I'm curious if
they have the same beam width issue as recreational radar.

The Beam Width on the small Raymarine units is 25 degrees, which means there is a blind
spot with a radius roughly 5 times the height of the antenna. From that picture, assuming
a 50 foot mast, the radar looks about 150 off the water, which could imply the boat is
"below the radar" when its several hundred yards away.

In addition, radar usually "blanks out" the processing for very short range - I forget the
distance but I think it was around 50 to 100 feet for small radars.

So I'm curious: is it possible that a small sailboat could be "invisible" to radar once it
get close to a large ship?

jeff

"Shen44" wrote in message
...
Subject: Radar
From: "NH_/\)_"
Date: 08/28/2003 20:08 Pacific Standard Time
Message-id:


Thanks a reply I was waiting for

NH_/)_


"anonymous" wrote in message
.. .
On Thu, 28 Aug 2003 14:04:13 GMT, "NH_/\)_"
said:

The sailboat was small yes... but it still should have been
picked up
on radar. Somebody did a major F-up.

Having spent a few years on the bridge of a naval vessel I can tell you
that
sailboats often don't show up on radar. 'Course it's been a few years for
me, and maybe the Navy's radar has improved since my time.


If that sailboat didn't show up on radar, it wasn't turned on. However, the
"Mark I" eyeball should have been working well, considering all the people on
"lookout" aboard a USN ship running the channel.

So I'm curious: is it possible that a small sailboat could be "invisible" to
radar once it
get close to a large ship?

jeff

Absolutely.
You will need one of the "techies" to spell out the numbers, but, one factor
which may help, is the size of the "scanner" used on ships (techies?).
I read where a minimum of 25' was possible, but not practical, so that the
number in reality is somewhat higher.
However, there are other factors which play an important part, and these
include shipboard structures causing blind spots.
If you look at the positioning of scanners on many ships, you will note things
such as containers, stacks, cargo gear, which are in the way.
On most ships, there is a diagram on the bridge, which shows potential blind
spots, and on most ships, you will find one astern.
In many cases, an additional scanner has been installed, close to the bow (and
in some cases, close to the stern) where there is a known and serious blind
spot.
When passing between 2 buoys (300' spacing) on 1/4 mi range (I rarely drop that
low) from a ship, I will normally (not always) lose radar sight, after I start
passing through them ... in many cases they may still be there, but they blend
in and are not overly useful.

lotsa variables

Shen

C'mon, you're supposed to be a professional?

It's Furuno not Furano!

http://www.furuno.co.jp/english/index.html

S.Simon
(a Master who takes sailing seriously)


"Shen44" wrote in message ...
Since Jeff had asked, this morning on an inbound I paid close attention to the
radar, using the 3cm set, rather than the 10cm.
Ship was about 560' with a 90' beam, radar, somewhat aft.
Going down the entrance channel, I at no time lost sight of the buoys as I
passed them (on radar ... lost them visually from centerline, G) and was also
able to watch a tug come alongside forward and still see him when he was
alongside (although his target was a blended hump on the side of own ship).
BTW, you do get a picture of your own ship, fwd of the scanner, especially when
the radar is aft.
So, in this case, I would have to say that the small boat could be seen until
it was hit, but this particular radar setup I know, was, above average in it's
picture (a Furano) and is not always the case.


Shen

Subject: Radar
From: "Simple Simon"
Date: 08/31/2003 11:07 Pacific Standard Time
Message-id:

C'mon, you're supposed to be a professional?

It's Furuno not Furano!

ROFL For all YOU know, Furano is the "big ship" version of Furuno.
BTW, brought in another, this afternoon ...... DECCA's .... not as good a
picture, but the "Old Man" was hogging the 3CM, and I was watching the 10 cm.

Shen

"Shen44" wrote in message

C'mon, you're supposed to be a professional?

It's Furuno not Furano!

ROFL For all YOU know, Furano is the "big ship" version of Furuno.

Google...

"furano radar ship" - 18 hits.

"furuno radar ship" - about 6250 hits.

Care to point us at the "furano" web site?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.