radar reflectors and rules

[sleddog]

Dear Skip,

In answer to your question, radar reflectors are incoherent reflectors and so they do add.

Some folks argue that two small reflectors are better than one big one,
because two reflectors will tend to fill in each-other's nulls. That is the
theory behind the Firdell Blipper that has multiple small corner cube reflectors inside.

Others argue that you are better off with one big octahedral-type reflector
because the peaks are large and an operator on a ship is more likely to
notice one of the peaks. Unfortunately the ARPA (Advanced Radar Plotting Aids) loses track of small boats in the nulls.

Sea-Me active radar target enhancers are not available in the US, but are
available from the UK via the web, and work great at X-band. No reflector
helps much with those ships that only use S-band radar. No reasonably-sized
reflector is large enough to make much difference at S-band.

As a practical matter, it is fine to use a radar reflector, and the Sea-Me
is a good choice, but the sailor on a small boat should assume that he/she
is invisible and take the responsibility to detect and avoid ships. The
small boat sailor is far more able (and motivated) to detect ships than vice
versa.

Stan Honey

 

[Adrian]

Sea-Me availability

Hi All,

A small correction to Stan's post about the availability of the Sea-Me. North American Mini Transat Ltd does carry the Sea-Me & can deliver to the US by mail or courier from Victoria, BC.

We are currently offering a discount on the first shipment we have in stock to promote the "visibility" of the Sea-Me. Please take a look at the website for details: www.northamericanminitransat.com

Adrian

 

[BobJ]

Dear Skip,

As a practical matter, it is fine to use a radar reflector, and the Sea-Me
is a good choice, but the sailor on a small boat should assume that he/she
is invisible and take the responsibility to detect and avoid ships. The
small boat sailor is far more able (and motivated) to detect ships than vice
versa.

Stan Honey

This reminded me that when I sailed my qualifier a couple of years ago, I had a C.A.R.D. radar detector running the whole time (I hadn't bought an AIS receiver yet). During the day, 3 container ships passed me and none of them set off the CARD, apparently because their radar was turned off. One of them set it off after he was nearly past me, I assume because he turned on his radar when he saw me. It made me wonder if any ships passed by at night which I never saw.

A radar detector or reflector, no matter how effective, is only good if ships' radar is running and apparently that is not always the case. Larger commercial ships are required to run their AIS however. My approach has been to use the CARD to pick up any smaller boats running radar, and the AIS for the larger ships.

 

[AlanH]

OK, so what do we (the SHTP RC) do about the existing radar reflector rule, now that we know that nothing generally available on the market even comes close to our written rule?

 

[BobJ]

Make the minimum return match what most of us have, as accepted for prior races. See page 2:

Davis Echomaster

 

[Adrian]

Radar Reflector Recommendation

Hi Bob,

The independent British study makes the following statement about the Davis Echomaster Reflector - I have cut & pasted the report's recommendations too:

"· The Davis Echomaster failed to get close to ISO8729 during this testing. Its peak
RCS is too low at 7.5m2 and its average performance is only 1.75m2. This
reflector is priced at 60 [pounds sterling] and is lightweight; it can be mounted on a rod as well
as by suspension (in the correct catch-rain position).
· The 4” tube reflector performed very poorly.
· It is concluded that either the active Sea-Me, POLARef and the Standard or
Large Tri-Lens radar reflectors are the best reflectors at heel and elevation
angles of over 10˚.
QINETIQ/D&TS/SEA/CR0704527/2.0 Page 31

6 Recommendations
· Based on the results of this report it is recommended that yachtsmen always
fit a radar reflector that offers the largest RCS practicable for their vessel.
· The RCS of the radar reflector should have a minimum consistent RCS of 2m2.
· The Sea-Me is the recommended product if power is available
· If power is not available then the passive Large Tri-Lens reflector is
recommended
· The 4” tube reflector is not considered suitable due to its poor performance. It
is also recommended that the 2” tube reflector is not suitable since the
performance of this target will be even lower.
· It is recommended that poorly performing radar reflectors are not fitted as it
is possible that the user could be lulled into a false sense of security believing
that their chances of detection has been enhanced.
QINETIQ/D&TS/SEA/CR0704527/2.0 Page 32"

In our highly litigious world RCs need to be careful about safety recommendations and not recommend something that independant safety authorities say do not work.

Adrian

 

[BobJ]

In our highly litigious world RCs need to be careful about safety recommendations and not recommend something that independant safety authorities say do not work.

1) The SHTP R/C's have never been in the business of making "safety recommendations." As always, each skipper is solely responsible for the safety of his vessel and crew, including the selection of equipment adequate for that safety. The SHTP08 Rules and Conditions are intended to be a minimum list of items required to participate in the race, not a list of "safety recommendations."

While your quoting of the study is helpful, your comment at the end of your post appears to be worded to put pressure on the R/C. This is what you attempted to do in the SSB thread on the old board. Moving on,

2) "Independent safety authorities" did not say the Davis Echomaster doesn't work, they said it didn't "get close to ISO8729 during this testing."

3) The Davis Echomaster isn't a 4" tube, just to clarify your incomplete cut/paste.

4) Would you put the Large Tri-Lens reflector on the mast of a Mini? (It's too big for my boat, which is 30'.) If not then (surprise) the only thing left, according to the particular study you quote, is your "Sea-Me."

5) Am I right that your "Sea-Me" is over $900 USD, even after the discounts?

I'm happy with my $55 Davis Echomaster. During the '06 race, two Matson ships said their radar picked me up fine - one even asked what kind of reflector I had because the return was so good.

 

[sleddog]

This group is well aware of the fallability of radar and radar reflectors. Nevertheless, it is a good reminder to re-read the below note from the 60 foot HUGO BOSS, mid-South Atlantic in the Barcelona World Race. Even an active reflector didn't prevent their almost being run over. I will say that between the West Coast and Hono, Matson does a good job on keeping bridge lookout. Other shipping you take your chances.

Updated : 3/12/2007 15:05 GMT
"Last night Capey noticed a ship on the horizon that was coming towards us. I made sure the active echo was on and switched on the AIS so he could see us clearly, but the ship kept coming on a collision course. About five miles away I went below and called them on the VHF. I kept calling and calling but no joy, so I grabbed the search light to grab their attention and light up the sails.

We had our big furling gennaker up called the 'big fella' and Capey had tried sailing high and low but the ship seemed to alter course to keep us in their sights. At this stage it was getting critical so I grabbed a white hand flare and set it off but still it kept on coming. We had no choice but to put HUGO BOSS head to wind and over we went, sails flogging and mast nearly in the water. The ship passed by so close I could nearly read its name on the transom. Once upright and on our way again I went below and called again – finally an answer. I asked his name and that was the last I heard. Bloody rude and dangerous and very obvious that a proper look out was not being maintained."

 

[moonduster]

Radar reflectors

The full text of the British Inquiry can be found here - http://www.maib.gov.uk/publications/invest...s/2007/ouzo.cfm

It's well worth the read for a number of reasons, all of them alarming.

I have a Davis Echomaster that is assembled directly on my backstay about 1/2 way up. It used to be higher, but would foul the main halyard when attaching or removing it from the sail in a stiff breeze if too much slack was in the halyard. Commercial ships see me just fine at 10-12 nm in a variety of conditions. That is, if they have their radars running, which is rare.

Regarding the Hugo Boss report, it just doesn't add up. Did the commercial vessel not have a watch, or did they keep altering course? It can't be both. Bottom line, HB should have changed course 10 degrees behind the vessel and there wouldn't have been a story.

 

[Warriors Wish]

Radar Reflectors

I apologize for revisiting this subject however I am struggling for a good solution and hope perhaps one of you has a suggestion.

I believe that unless I go to an active system my alternative is a Davis Reflector mounted 13' off the water.

I have looked a couple of different solutions for mounting with my biggest concern being chafe (sail primarily). I am leaning to mounting a unit on a pole from the transom. Has anyone done this? what type of pole did you use? Did you have to support the pole with guy wires? Have you had any problems?

I have read that someone has mounted this unit to the backstay. My mainsail would not clear a unit mounted this way however if the unit was mounted so that it rolled when the mainsail passed by it might be work. I would also need to include a chafe patch on the main. Would anyone care to comment about a unit mounted this way.

Thanks,

Don
Warriors Wish

 

[Alchera]

I have looked a couple of different solutions for mounting with my biggest concern being chafe (sail primarily). I am leaning to mounting a unit on a pole from the transom.

Why can't you hang it from a spreader using a flag halyard? That's a pretty simple approach, and there are ways to rig it up so that it doesn't flop around.

- Mark

 

[Warriors Wish]

Flag halyard

Simple approach however when eased the mainsail chafes against it. I thought about keeping the reflector on the windward side and simply gybing when neccessary. Am I over reacting to the chafe?

 

[BobJ]

Don, my reflector is on a flag halyard as Mark suggests. I was worried about chafe too - the edges of the Davis Echomaster are bare aluminum. My first attempt was to toss a light line over the spreader and hoist the reflector up. Sure enough, before long the reflector cut through the line.

Then we screwed two small eye straps to the underside of the spreader, spaced well apart. The reflector goes up on the outboard end and clears the return (down) end of the halyard. On my boat, the main doesn't quite reach the reflector so it doesn't chafe on that either. This is a function of vang tension and how far you ease the main down wind - mine's a sprit boat so the main never gets eased that far. (But it's close - if the reflector went up on the inboard end of the halyard it would chafe the main.)

So I would try it and see if with the right spacing you can avoid the chafe.

The other benefit of the flag halyard is that you can fly the SHTP battle flag! (R/C, we ARE getting battle flags again, right?)

 

[Alchera]

Another way I deal with chafe prevention - I wrap all the edges of the Davis with a couple of layers of electrical tape. If you stretch the tape as you apply it, it conforms and shapes itself to the edge of the reflector. Uses up a bit of electrical tape, but it really stops the chafe. Also, you need to redo the tape every couple of years because it gets brittle and starts coming off.

- Mark