Does your boat have a radar reflector? What type is it? How well does it work?
- Thread starter dserrell
- Start date
- Status
Re: Does your sailboat have a radar reflector? What type is it? How well does it work?
I have been carefully watching my new radar in clear weather and looking at reflectors this summer. Reflectors are absolutely essential. A 45 foot wooden ketch with wood masts and no reflector is absolutely invisible. Many plastic and wooden lobsterboats with little metal top hamper are also stealth.
I haven't encountered enough boats with the cylindrical reflectors to form an opinion. The ones fastened directly to the mast can't be putting out much more return from astern than the mast alone though.
I have two of the Plastimo collapsible aluminum reflectors. I was converting a second one to the more reflective "raincatcher" mode and decided at the last moment to just add the original on the bottom. I thus have multiple reflective directions.
I have been carefully watching my new radar in clear weather and looking at reflectors this summer. Reflectors are absolutely essential. A 45 foot wooden ketch with wood masts and no reflector is absolutely invisible. Many plastic and wooden lobsterboats with little metal top hamper are also stealth.
I haven't encountered enough boats with the cylindrical reflectors to form an opinion. The ones fastened directly to the mast can't be putting out much more return from astern than the mast alone though.
I have two of the Plastimo collapsible aluminum reflectors. I was converting a second one to the more reflective "raincatcher" mode and decided at the last moment to just add the original on the bottom. I thus have multiple reflective directions.
I have two
I have two, a Plastimo (tube style) and a Davis Echomaster. The Plastimo admittedly does not work as well but I leave it up 24/7. The Echomaster works quite well but must be raised in the rain catcher position to be the most effective.
Nothing works as well as an active radar reflector but those are expensive..
If you don't sail in fog, or at night, it is not a critical item but here in Maine it is..
I have two, a Plastimo (tube style) and a Davis Echomaster. The Plastimo admittedly does not work as well but I leave it up 24/7. The Echomaster works quite well but must be raised in the rain catcher position to be the most effective.
Nothing works as well as an active radar reflector but those are expensive..
If you don't sail in fog, or at night, it is not a critical item but here in Maine it is..
Take a look at this URL: http://www.ussailing.org/safety/Studies/radar_reflector_test.htm
(I think the study might originally be from West Marine)
this is a pretty exhaustive test of a variety of reflectors. The quote about the cylindrical ones (Mobri) is pretty harsh:
"The smaller Mobri is invisible under all conditions, and, with its minimal windage, might make a nice addition for the Stealth Bomber"
they be funny guys!
Chris
(I think the study might originally be from West Marine)
this is a pretty exhaustive test of a variety of reflectors. The quote about the cylindrical ones (Mobri) is pretty harsh:
"The smaller Mobri is invisible under all conditions, and, with its minimal windage, might make a nice addition for the Stealth Bomber"
they be funny guys!
Chris
Over on the woodenboat forum there is an EE, user name Paladin. He has been involved in all manner of electronics work and states absolutely that the most effective radar reflectors can be made by filling a gallon jug with strips of aluminum foil 3/8 inches wide and varying from 2-6 inches long. tTese are the wave length or half wave length of the radar emissions. He has sailed three times around the world using this on his own boats. It might be good to put this to the test.
I think they should be mandatory for night sailing as well as fog and rain. Our dinky little lights are pretty invisible in a storm at sea at night. Frankly better to put on the steaming light with a headsail up so it illuminate the entire sail. I use a Davis Echomaster but wasn't thrilled with the quality of the little clamps that hold the pieces together. Also use the rain catcher position. Interesting to note, I don't have a clue whether it works or not, but I have never been run into by another ship or boat while using it.
Reflector Types and Specs
By "cylindrical type" I hope you are not including the Blipper and the Echomax as these are the mainstay of reflectors used on small craft to date and are known to work well until heeled too far. As 'walmsleyc' states the Mobri ones have no measurable response.
I participated in some radar reflector tests done by 'Practical Boat Owner' Mag here in the UK and, just for a laugh, we included items such as a plastic bag full of crumpled aluminium cooking foil - no response at all.
I do quite like the idea of a container full of chaff - as used in anti-missile missiles. However I do think this would need to be scattered over a wide area to make a worthwhile response.
The definitive work on small craft reflectors, and easiest to read, is that in 1995 by Jim Corenman, Chuck Hawley, Dick Honey and Stan Honey and may be downloaded on the link kindly provided by 'walmsleyc'.
The International Standards Organisation (IMO) have been many years in the process of updating ISO 8729-1999 and next year (one hopes) they will publish a revised performance spec for the passive types of small craft reflectors.
I am confident that none of the existing yacht sized reflectors will comply because it will require a three times larger crossectional reflecting area than at present and also 360° coverage with only small nulls. And all this at the high angles of heel which yachts normally experience. The overall sizes and weights of the reflector are also to be specified.
However, do not delay buying a reflector right now if you don't have one because the physics of reflectors do not change and it is my contention that nobody can come up with a design which complies in all respects.
ISO 8729 part 2:2009 has just been published for active reflectors of the 'Sea-Me' type and both Sea-Me and the Echomax do comply.
See:- http://www.iso.org/iso/catalogue_detail.htm?csnumber=51332
In fact, though they have no response at all to 'S' band radars, active reflectors (transponders) massively outperform passive reflectors on 'X' band.
The result being that it is recommended to carry both types.
By "cylindrical type" I hope you are not including the Blipper and the Echomax as these are the mainstay of reflectors used on small craft to date and are known to work well until heeled too far. As 'walmsleyc' states the Mobri ones have no measurable response.
I participated in some radar reflector tests done by 'Practical Boat Owner' Mag here in the UK and, just for a laugh, we included items such as a plastic bag full of crumpled aluminium cooking foil - no response at all.
I do quite like the idea of a container full of chaff - as used in anti-missile missiles. However I do think this would need to be scattered over a wide area to make a worthwhile response.
The definitive work on small craft reflectors, and easiest to read, is that in 1995 by Jim Corenman, Chuck Hawley, Dick Honey and Stan Honey and may be downloaded on the link kindly provided by 'walmsleyc'.
The International Standards Organisation (IMO) have been many years in the process of updating ISO 8729-1999 and next year (one hopes) they will publish a revised performance spec for the passive types of small craft reflectors.
I am confident that none of the existing yacht sized reflectors will comply because it will require a three times larger crossectional reflecting area than at present and also 360° coverage with only small nulls. And all this at the high angles of heel which yachts normally experience. The overall sizes and weights of the reflector are also to be specified.
However, do not delay buying a reflector right now if you don't have one because the physics of reflectors do not change and it is my contention that nobody can come up with a design which complies in all respects.
ISO 8729 part 2:2009 has just been published for active reflectors of the 'Sea-Me' type and both Sea-Me and the Echomax do comply.
See:- http://www.iso.org/iso/catalogue_detail.htm?csnumber=51332
In fact, though they have no response at all to 'S' band radars, active reflectors (transponders) massively outperform passive reflectors on 'X' band.
The result being that it is recommended to carry both types.
I have one of those cylinders on the forward side of the mast, looks like a fender. I've been told it works very well.
Davis on Backstay
On my Mirage I had a Davis radar reflector that is permanently assembled around the backstay, about 1/3rd of the way up. I asked a tug how visible I was and he said I had a strong signal.
On a recent trip I used my radar during the day and compared what I was seeing to the screen. At a range of 1-5 miles, I had strong returns from every sail boat I could see. The weakest returns were from Lobster boats. Some were near invisible.
On my Mirage I had a Davis radar reflector that is permanently assembled around the backstay, about 1/3rd of the way up. I asked a tug how visible I was and he said I had a strong signal.
On a recent trip I used my radar during the day and compared what I was seeing to the screen. At a range of 1-5 miles, I had strong returns from every sail boat I could see. The weakest returns were from Lobster boats. Some were near invisible.
Yes, I think the cylindrical ones talked about in the study are the Mobri style ones (don't work) and not the larger fender shaped ones people often install on their masts. I've also see the triple ball shaped ones. Both of these look like they contain smaller spheres within them. Anyone know what's inside?
Chris
Chris
Interesting read. Why hasn't anyone gimbaled the Davis Echomaster? It seams that would really improve it’s performance. I’ve seen radar domes that are gimbaled. Couldn’t it be rigid mounted either above or below it?
Unfortunately, I bought a Morbi 2" on sale @ Defender last year before doing any research. I mounted it on a stay just under the spreader. Better than nothing at all I guess.
Unfortunately, I bought a Morbi 2" on sale @ Defender last year before doing any research. I mounted it on a stay just under the spreader. Better than nothing at all I guess.
I don't have radar but have been aboard other boats that do. The signal received from sailboats without any form of reflector save their mast was almost as good as those carrying one. The mast alone produces a fairly large surface for radar and unless made of wood or carbon fiber is highly visible. I do have on board a Davis emergency reflector but have never used it.
- Status