Radar reflectors
 

What works? What doesn't? What to buy?
Thanks
Gordon

Someone at our local boat show was bragging up this model
http://ca.binnacle.com/online/produc...dept%5Fid=5120

For a smaller sailboat like mine, I'd buy...
http://ca.binnacle.com/online/produc...dept%5Fid=5120

Don White wrote:
Someone at our local boat show was bragging up this model
http://ca.binnacle.com/online/produc...dept%5Fid=5120

For a smaller sailboat like mine, I'd buy...
http://ca.binnacle.com/online/produc...dept%5Fid=5120



The first item, a Davis Radar reflector, is a good item. I keep one
folding up as a reserve to the Firdell mounted high on the mast. The
second, a Mobri, is considered by many to be useless. "Essential
invisible" according to the US Sailing test.

http://www.ussailing.org/safety/Stud...ector_test.htm

"Jeff Morris" wrote in message
news:KMWdnVfP3-WqMorfRVn-

The first item, a Davis Radar reflector, is a good item. I keep one
folding up as a reserve to the Firdell mounted high on the mast. The
second, a Mobri, is considered by many to be useless. "Essential
invisible" according to the US Sailing test.

http://www.ussailing.org/safety/Stud...ector_test.htm

Thanks for that link.....We get lots of fog around here...(some summers..a
full month's worth).
I didn't realize how useless the common cylinder type reflectors were. We
had one high up on the backstay of the Mirage 33 I crewed on and had a false
sense of security. I'll think twice before I buy a unit for my much smaller
Sandpiper 565.

"Jeff Morris" wrote ...
Don White wrote:
Someone at our local boat show was bragging up this model
http://ca.binnacle.com/online/produc...dept%5Fid=5120

For a smaller sailboat like mine, I'd buy...
http://ca.binnacle.com/online/produc...dept%5Fid=5120



The first item, a Davis Radar reflector, is a good item. I keep one
folding up as a reserve to the Firdell mounted high on the mast. The
second, a Mobri, is considered by many to be useless. "Essential
invisible" according to the US Sailing test.

http://www.ussailing.org/safety/Stud...ector_test.htm

US Sailing and West Marine have given the Mobri bad press. So if the Mobri
reflectors are 'essentially invisible', why does the USCG specify them
(since 1998) as the internal radar reflectors for unlighted buoys?

See http://www.uscg.mil/systems/gse/gse2...ions/450-D.pdf and note
Section 3.3.1:

3.3.1 Internal radar reflectors. The radar reflectors for unlighted buoys
shall be Mobri Marine M3 or M4, or equivalent, as specified in the drawings.
Radar reflectors shall be installed in the buoys by inserting them into
preformed slots of the appropriate size. The slots may be either cut or
melted into the can or nun upper body, as shown on the drawings. A plug of
foam shall be inserted to completely and snugly fill the gap between the
bottom of the radar reflector and the outer surface of the buoy body.

The USCG Ocean Engineering Division didn't specify the less expensive Davis
reflector. Funny that, eh?

Cheers

Bil

Bil Hansen wrote:
"Jeff Morris" wrote ...

Don White wrote:

Someone at our local boat show was bragging up this model
http://ca.binnacle.com/online/produc...dept%5Fid=5120

For a smaller sailboat like mine, I'd buy...
http://ca.binnacle.com/online/produc...dept%5Fid=5120



The first item, a Davis Radar reflector, is a good item. I keep one
folding up as a reserve to the Firdell mounted high on the mast. The
second, a Mobri, is considered by many to be useless. "Essential
invisible" according to the US Sailing test.

http://www.ussailing.org/safety/Stud...ector_test.htm


US Sailing and West Marine have given the Mobri bad press.

Don't forget Practical Sailor and Practical Boat Owner. And you'll find
dealer sites that advise "best suited for powerboats," presumably
because they don't work well when heeled.

So if the Mobri
reflectors are 'essentially invisible', why does the USCG specify them
(since 1998) as the internal radar reflectors for unlighted buoys?

See http://www.uscg.mil/systems/gse/gse2...ions/450-D.pdf and note

Interesting reading. However, the M3 and M4 are considerably larger
than the S2 commonly seen on small boats, and the buoys use three of
them. Also, I found no other mention of Mobri on the CG site, including
in the detailed specs for the buoys. I wonder if they are actually
used, since there are other vendors of reflectors for this purpose?

And remember, these are small, foam buoys used in inland waters. Even
the largest size only cost $5000, the smaller sizes are under $500.
These are not the steel buoys found in the ocean.

....


The USCG Ocean Engineering Division didn't specify the less expensive Davis
reflector. Funny that, eh?

Hilarious. However, I'm guessing you've never actually sailed on the
ocean, because if you had, you'd appreciated that most ocean buoys
incorporate the same design as the Davis into their fabrication. And
several sizes of the foam buoys you mention incorporate aluminum corner
reflectors instead of the cylindrical type.

"Jeff Morris" wrote in message
...
Bil Hansen wrote:
"Jeff Morris" wrote ...

Don White wrote:

For a smaller sailboat like mine, I'd buy...
http://ca.binnacle.com/online/produc...dept%5Fid=5120

The first item, a Davis Radar reflector, is a good item. I keep one
folding up as a reserve to the Firdell mounted high on the mast. The
second, a Mobri, is considered by many to be useless. "Essential
invisible" according to the US Sailing test.

http://www.ussailing.org/safety/Stud...ector_test.htm

US Sailing and West Marine have given the Mobri bad press.

Don't forget Practical Sailor and Practical Boat Owner. And you'll find
dealer sites that advise "best suited for powerboats," presumably
because they don't work well when heeled.

So if the Mobri
reflectors are 'essentially invisible', why does the USCG specify them
(since 1998) as the internal radar reflectors for unlighted buoys?

See http://www.uscg.mil/systems/gse/gse2...ions/450-D.pdf and
note

Interesting reading. However, the M3 and M4 are considerably larger
than the S2 commonly seen on small boats, and the buoys use three of
them. Also, I found no other mention of Mobri on the CG site, including
in the detailed specs for the buoys. I wonder if they are actually
used, since there are other vendors of reflectors for this purpose?

And remember, these are small, foam buoys used in inland waters. Even
the largest size only cost $5000, the smaller sizes are under $500.
These are not the steel buoys found in the ocean.

The USCG Ocean Engineering Division didn't specify the less expensive
Davis
reflector. Funny that, eh?

Hilarious. However, I'm guessing you've never actually sailed on the
ocean, because if you had, you'd appreciated that most ocean buoys
incorporate the same design as the Davis into their fabrication. And
several sizes of the foam buoys you mention incorporate aluminum corner
reflectors instead of the cylindrical type.

Thanks for the gratuitous swipe at my ocean experience! Nicest thing anyone
has said to me all day!

As it turns out, I have a Mobri near my masthead (you're right: I've only
sailed from California to Malaysia, from where I now reply to you, on my
current voyage. I've heaps more ocean to cross and things to learn from more
experience sailors) and I do more or less agree with PBO etc that Mobri
reflectors do not return much of a signal at any angle of heel (I base that
on talking to cargo ships that could not locate me by radar). Because of
that, I don't rely on other ships seeing me: I watch out for them and use a
radar detector when I'm not running my radar.

I thought that the PBO tests were more meaningful than the West Marine
tests; PBO also noted that adding extra radar reflectors was not necessarily
the best thing to do, because of possible cancellation effects due to phase
differences. I note also that Nova Marine (www.novamarine.ca) concluded
Davis Echo Master radar reflectors were not that good (compared to the ISO
standard) either. But I've not heard of the Big Dot reflector ever going
into production.

Bil

Bil Hansen wrote:
"Jeff Morris" wrote in message

Hilarious. However, I'm guessing you've never actually sailed on the
ocean, because if you had, you'd appreciated that most ocean buoys
incorporate the same design as the Davis into their fabrication. And
several sizes of the foam buoys you mention incorporate aluminum corner
reflectors instead of the cylindrical type.


Thanks for the gratuitous swipe at my ocean experience! Nicest thing anyone
has said to me all day!

Well, gee, Bil. Al the buoys around here look like giant Davis
reflectors. Do they make them differently in Malaysia? I'm not the one
who brought this up, it was you, remember?



As it turns out, I have a Mobri near my masthead (you're right: I've only
sailed from California to Malaysia, from where I now reply to you, on my
current voyage. I've heaps more ocean to cross and things to learn from more
experience sailors) and I do more or less agree with PBO etc that Mobri
reflectors do not return much of a signal at any angle of heel (I base that
on talking to cargo ships that could not locate me by radar). Because of
that, I don't rely on other ships seeing me: I watch out for them and use a
radar detector when I'm not running my radar.

So, you're saying that you use and recommend a radar reflector that in
you experience doesn't actually work? Yea, that makes sense.




I thought that the PBO tests were more meaningful than the West Marine
tests; PBO also noted that adding extra radar reflectors was not necessarily
the best thing to do, because of possible cancellation effects due to phase
differences. I note also that Nova Marine (www.novamarine.ca) concluded
Davis Echo Master radar reflectors were not that good (compared to the ISO
standard) either. But I've not heard of the Big Dot reflector ever going
into production.

The site essentially says everything is bad, except for theirs which is
not in production. But they say the Mobri is especially bad. One of
the flaws in their Davis test is that they are often hoisted on a
halyard and stay level when the boat is heeled. They one that I used
spun around a lot, which should minimize the problem with nulls.

So, I'm having trouble getting a handle on your position, Bil. Just
which reflector do you recommend?

"Jeff Morris" wrote ...
Bil Hansen wrote:
"Jeff Morris" wrote

Hilarious. However, I'm guessing you've never actually sailed on the
ocean, because if you had, you'd appreciated that most ocean buoys
incorporate the same design as the Davis into their fabrication. And
several sizes of the foam buoys you mention incorporate aluminum corner
reflectors instead of the cylindrical type.


Thanks for the gratuitous swipe at my ocean experience! Nicest thing
anyone
has said to me all day!

Well, gee, Bil. Al the buoys around here look like giant Davis
reflectors. Do they make them differently in Malaysia? I'm not the one
who brought this up, it was you, remember?

As it turns out, I have a Mobri near my masthead (you're right: I've
only
sailed from California to Malaysia, from where I now reply to you, on my
current voyage. I've heaps more ocean to cross and things to learn from
more
experience sailors) and I do more or less agree with PBO etc that Mobri
reflectors do not return much of a signal at any angle of heel (I base
that
on talking to cargo ships that could not locate me by radar). Because of
that, I don't rely on other ships seeing me: I watch out for them and
use a
radar detector when I'm not running my radar.

So, you're saying that you use and recommend a radar reflector that in
you experience doesn't actually work? Yea, that makes sense.

I must have erred in my writing! Or perhaps you misread me?

I don't recommend any radar reflector. I pointed out that (1) West Marine
has given Mobri bad press but (2) the USCG has seen fit to specify Mobri
reflectors as internal reflectors in some of its buoys (and I assume that
the USCG did tests of reflectors). I think the USCG specification is
curious. And tried to say as much.

If you read me as recommending any reflector by brand name, let me be clear
that I do not: I instead recommend that a skipper keep a good watch and not
rely on having a radar reflector.

My experience is that, in a seaway, cargo ships that I've called on VHF have
had trouble locating me (with a Mobri reflector) by radar. But the USCG and
the USN has never had a problem locating and, when it served them,
interdicting me. My experience is that at 3 nm most all sailboats, including
those with bigger reflectors than mine, show on radar as tiny dots (in
contrast to the Big Dot promised by the reflector that seems never to have
gone into production) that fluctuate in reflectance, because of heel etc.

I have no dispute with you about the external reflectors on buoys: but
they're bigger and more solid than a Davis Echomaster.

So what about you and your ocean experience: I'm guessing that you have done
more than three
circumnavigations?

Bil

Here's a test from 1995:
http://www.ussailing.org/safety/Stud...ector_test.htm


Here are some interesting types:
http://www.rozendalassociates.com/reflectors/

Then finally, how about an active reflector, instead of passive?
http://www.sea-me.co.uk/

--


Keith
__
Leaving the dock is optional. Returning is mandatory.
"Gordon" wrote in message
...
What works? What doesn't? What to buy?
Thanks
Gordon

Bil Hansen wrote:
"Jeff Morris" wrote ...

....

So, you're saying that you use and recommend a radar reflector that in
you experience doesn't actually work? Yea, that makes sense.


I must have erred in my writing! Or perhaps you misread me?

I don't recommend any radar reflector. I pointed out that (1) West Marine
has given Mobri bad press but (2) the USCG has seen fit to specify Mobri
reflectors as internal reflectors in some of its buoys (and I assume that
the USCG did tests of reflectors). I think the USCG specification is
curious. And tried to say as much.


I apologize - I inferred from your comments about the USCG, and the
fact that you have a Mobri, that you felt the bad press was
unjustified. I should not have presumed that.

My take on the CG requirement is that they wanted something that would
fit in a cylinder built into small inland buoys that are constructed of
rolled foam and have very little metal. At the time, 1995, Mobri may
have been the only candidate. There are other companies that make this
style of reflector now so I can't say if Mobris are in use. At any
rate, these are not buoys that ships use to find harbor entrances in a
storm, they are used to find the next bend in the ICW.



If you read me as recommending any reflector by brand name, let me be clear
that I do not: I instead recommend that a skipper keep a good watch and not
rely on having a radar reflector.

Relying on a reflector is silly - it requires that someone else actually
is watching. However, if you're going to carry one on the top of your
mast all the time, doesn't it make sense to use one that actually reflects?


My experience is that, in a seaway, cargo ships that I've called on VHF have
had trouble locating me (with a Mobri reflector) by radar. But the USCG and
the USN has never had a problem locating and, when it served them,
interdicting me. My experience is that at 3 nm most all sailboats, including
those with bigger reflectors than mine, show on radar as tiny dots (in
contrast to the Big Dot promised by the reflector that seems never to have
gone into production) that fluctuate in reflectance, because of heel etc.

I'd be curious to see what the are. I'm guessing that the "12" model is
12 inches in diameter, making it rather large for masthead use. And it
would be fair to compare to the large commercial Blipper (300-5) rather
than the smaller version. Still, an active unit would be even better.



I have no dispute with you about the external reflectors on buoys: but
they're bigger and more solid than a Davis Echomaster.

Actually, the 6NFR and 6CFR buoys from the spec you referenced use,
instead of the cylinder style, a Davis style square corner aluminum
reflector that's smaller than the folding units many boats (myself
included) carry as a spare.



So what about you and your ocean experience: I'm guessing that you have done
more than three circumnavigations?

Only in my dreams. However, I've been cruising the New England coast
for about 25 years. Much of the Maine coast has fog on a daily basis
all summer - I don't see the sense of carrying a reflector that
disappears when you heel 20 degrees.

How about a C.A.R.D. detector? http://www.survivalsafety.com/

Gordon

"Keith" wrote in message
...
Here's a test from 1995:
http://www.ussailing.org/safety/Stud...ector_test.htm


Here are some interesting types:
http://www.rozendalassociates.com/reflectors/

Then finally, how about an active reflector, instead of passive?
http://www.sea-me.co.uk/

--


Keith
__
Leaving the dock is optional. Returning is mandatory.
"Gordon" wrote in message
...
What works? What doesn't? What to buy?
Thanks
Gordon

I've never used one of these, but the idea is interesting:

http://www.speedseal.com/seame/welcome.htm

.... it apparently works along the same lines as a SART, enhancing your
radar "blip" by using an active transponder.

Two other points I'd add:

We used the "el cheapo" Davis reflectors on drift buoys on the research
ships I've been on. With the reflector, the buoys were usually visible
on radar at 10-12 nm out, without the reflector they were almost
entirely invisible to the radar no matter how close we were. Not very
scientific, but pretty good evidence that they work IMHO.

No matter how "good" your radar reflector, it by no means replaces your
need to stand an alert and vigilent watch.

--

=-------------------------------------------------=
Renewontime
A FREE email reminder service for licensed mariners
http://www.renewontime.com
=-------------------------------------------------=

My take on the CG requirement . . .

NavAid bouys suffer from bird splat and damage problems, so for a small
device the enclosed feature of the Mobri makes sense. The big'uns have
retroreflection built right in to the structure, or an actual racon.

My take on the issue is unless you have a large (or sluglike) boat that
doesn't mind the windage of an effective (read expensive) permanent
mount reflector, a Davis EchoMaster raised high on a burgee halyard in
the catch rain position is reasonable. It's light weight, unaffected
by heel and moves around enough to mask null return problems. Fix a
few strands of yarn on a corner so it doesn't spin like a banshee in
high winds and snarl its halyard.

On Mon, 21 Feb 2005 08:06:54 -1000, renewontime dot com
wrote:

We used the "el cheapo" Davis reflectors on drift buoys on the research
ships I've been on.

===================================

Offshore commercial fishing boats also use them to mark their buoys
which is a pretty good recommendation. I have carried a small folding
Davis for years which I assemble and display in foggy conditions,
usually elevated on the end of a boat hook. I've been told that it
shows up well. On the other hand my new 4KW Furuno radar has no
problem picking up small boats of all types at 2 to 4 miles, at least
in flat water conditions.