Sailing yacht radar visibility

[The Professional]

I am aware of the variables of when it comes to radar range, such as the height of the radar, height of the target, power of the radar, sea conditions, etc.

Someone was telling me recently that a sailing yacht, even with the sails up, has very poor radar reflective capabilities. According to him a large ship with a radar mounted high up, in most cases could only see a 30 foot sailing vessel from only 3 nautical miles away!

Is this true?

I'm sure we have some recreational users with radars fitted, is a small sailing vessel without any radar reflectors really only visible from within a few miles?

 

[john_morris_uk]

There’s no simple or easy answer.
Irrespective of size of yacht, has it got a radar reflector and is the radar reflector any good?
We have a radar reflector riveted to the mast. I’ve yet to find a ship that hasn’t picked us up on radar at 8-10 miles. However we have a Class B AIS transponder now so in open water we’re very visible.

 

[Neeves]

The Spirit of Tasmania, a car ferry, used to run from Sydney to Devenport in Tasmania, the standard route is Melbourne to Tasmania. They were following us down the coast (and passed us ) and picked us up at 16nm. We knew they were behind us and had spoken to them on VHF as we were on the same passage - so they were specifically looking for us. We had a long chat with them about radar. Cruise ships are very attentive to small craft - but usually have a much larger ships crew than other large commercial vessels.

I think a lot depends on how much attention is being paid by the crew on watch and location. I suspect more attention is paid in the English Channel or Singapore Straits than crossing the Pacific.

On the east coast of Australia we have the East Australian Current running from north to south. Any ships or yachts transmitting the coast try to piggyback on the current, so all going south follow the same passage plan and all going north are closer in shore. So - going south we watch our backs . Going north is not such a big issue as yachts can get much closer inshore than a commercial ship would risk.

Jonathan

 

[The Professional]

There’s no simple or easy answer.
Irrespective of size of yacht, has it got a radar reflector and is the radar reflector any good?
We have a radar reflector riveted to the mast. I’ve yet to find a ship that hasn’t picked us up on radar at 8-10 miles. However we have a Class B AIS transponder now so in open water we’re very visible.

My question is WITHOUT radar reflector.

The guy is trying to convince me to fit radar reflectors. So I'm interested in knowing APPROXIMATE visibility without radar reflector compared to with. And is his line about a yacht with the sails up and no radar reflector only being visible from 3 nm away true?

 

[TernVI]

A lot depends on the sea state.
In simple terms, if the water is rough, the radar might be seeing reflections from waves which are similar to the reflection from your boat.
Another effect to be aware of, is that a radar looking down from a high position on a ship, sees a lot of wave reflections and the reflection from a small boat may be lost among those.

If a yacht is upright, the mast can have a pretty good return. When it's well heeled, less so.
Carbon mast? get a reflector!

 

[Uricanejack]

My question is WITHOUT radar reflector.

The guy is trying to convince me to fit radar reflectors. So I'm interested in knowing APPROXIMATE visibility without radar reflector compared to with. And is his line about a yacht with the sails up and no radar reflector only being visible from 3 nm away true?

the average yacht is probably better equipped with stealth technology than a average fighter jet. Basically made of plastic and most of the metal bits are round

even so.

On a nice day radar can pick up a shit hawk on a log.
Or a paddler in a kayak.

On a bad day radar has trouble picking up steel ships,

Most average yachts probably have an average radar reflector, which may or may not be hung correctly.

JM’s esitimate is a good ball park for a properly set up radar detecting an average yacht in average conditions.

Add rough seas or rain particularly heavy rain then all bets off.

Most if not all of the time. I have no idea if they have a radar reflector. Or not.
So take your pick.
Do you want the better chance to be seen or not.

 

[grumpy_o_g]

My question is WITHOUT radar reflector.

The guy is trying to convince me to fit radar reflectors. So I'm interested in knowing APPROXIMATE visibility without radar reflector compared to with. And is his line about a yacht with the sails up and no radar reflector only being visible from 3 nm away true?

Tern's summed it up but I would never rely on being visible on radar if I could avoid it and if I had to I'd definitely not really on the yacht's signature nor a passive radar reflector. They won't increase the signature of your boat by any significant amount and it's certainly not (edited) an exaggeration to say to say that a 30 ft yacht may not be visible at 3 miles, even with a radar reflector. If you think giving a good radar return is important then fit an active transponder such as an Echomax. Aside from really lighting up the display this can also be got in dual-band model which could be useful if you are spending a lot of time in open water where ships tend to switch from X -band to S-band. In simple terms S-band has a longer range and is less susceptible to weather conditions weakening the signal - exactly what a large ship on passage wants. X-band is better at shorter ranges and gives a more detailed picture, great for smaller boats and pilotage or busy waters. All small boat radars are X-band but a larger vessel will usually carry an S-band radar too.

 

[Neeves]

My question is WITHOUT radar reflector.

The guy is trying to convince me to fit radar reflectors. So I'm interested in knowing APPROXIMATE visibility without radar reflector compared to with. And is his line about a yacht with the sails up and no radar reflector only being visible from 3 nm away true?

See post 3

We have no radar reflector, apart from a mast, boom and 2 engines and O/B

Being a catamaran our mast is usually vertical

Jonathan

 

[The Professional]

All sorts of answers coming in.

Let me phrase this another way. If you were in a 30 sailing yacht with the sails up, with or without radar reflector, do you think any radar could reasonably pick it up from 20 nm away?

 

[sarabande]

Someone is feeding you radar fear.

Multiple radar reflectors on a yacht CAN under some conditions cause an incoming search pulse to miss you by cancelling the return signal in some way. Stick with one and please dont buy the tube type Mobri. John_Morris is very clued on the technological answers: harken to him.


And your last question about distance. I would hope our RN and Border Force vessels would pick you up at a much longer distance than 20 nm. They track smugglers and traffickers from well over the horizon., plus CG and Marine Traffic radar stations are mounted on top of cliffs. Range from a 100m cliff is 21 miles.

 

[Neeves]

I think it unrealistic to depend on a large commercial vessel picking you up on radar at 20nm. I f they do pick you up they may record the target, mentally, but they are unlikely to do much about it till you are a bit closer as at 20nm they will be totally unsure of what you are and your intentions.

Your possible concerns maybe alleviated if you have AIS and you transmit who/what you are. This will, or should, be picked up well beyond 20nm.

Might I suggest you go back a step and tell us what you are trying to achieve. If you want to be 'seen' as a target and something to be avoided (by a large commercial vessel) there they are more answers than a 'simple' radar reflector. You seem to be suggesting that you want to be 'seen' but it might be a better strategy (as well as being seen) to be proactive and not be in close proximity to large commercial vessels - by your seeing them and you keeping out of their way.

AIS also answers this need, as does you having radar (less convenient on a 30' yacht) (and obviously maintaining good watch keeping)

Jonathan

 

[The Professional]

Someone is feeding you radar fear.

Multiple radar reflectors on a yacht CAN under some conditions cause an incoming search pulse to miss you by cancelling the return signal in some way. Stick with one and please dont buy the tube type Mobri. John_Morris is very clued on the technological answers: harken to him.

And your last question about distance. I would hope our RN and Border Force vessels would pick you up at a much longer distance than 20 nm. They track smugglers and traffickers from well over the horizon., plus CG and Marine Traffic radar stations are mounted on top of cliffs. Range from a 100m cliff is 21 miles.

How could RN and Border Force see much further than 20 nm, if as you say radar mounted on top of a 100m cliff is 21 miles? I've yet to see a naval vessel with a mast for a radar 100m in the air!

 

[Uricanejack]

To post 24

No.

 

[Neeves]

To post 24

No.

Jack - makes little sense to me

J

 

[Uricanejack]

Jack - makes little sense to me

J

Sorry I screwed up the quote bit.
Direct answer to the question, about picking up a 30 sailing yacht at 20 nm

No,

At least, none I ever used. Military stuff I wouldn’t know. Maybe a Nimrod could.

 

[SimonKNZ]

So many variables, but if you're worried, fit a reflector
I've done 20mm gun firings from a ship and seen the radar form tracks (complete with labels and track numbers) on the outbound shells. But that wasn't an average ship's radar

 

[john_morris_uk]

How could RN and Border Force see much further than 20 nm, if as you say radar mounted on top of a 100m cliff is 21 miles? I've yet to see a naval vessel with a mast for a radar 100m in the air!

You need to take into account the height of the object you’re looking at.
See:http://www.tscm.com/rdr-hori.pdf
Even our yacht radar can see ships that are hull down over the horizon. (But what’s the point!!!)

What is it you actually want to know? What are you trying to achieve?

Your mate who suggested a yacht with no radar reflector is only visible at 3 miles or less is wrong as a general rule. In adverse conditions and ancient radars it might be true but modern radars look for repeat patterns in the clutter so identify targets that a human eye staring at the screen would miss. However it still depends on the operator and given enough clutter and rain you might be missed but not as a general rule.

Personally, my feeling is that anyone sailing around in adverse weather without a decent radar reflector is a fool.

 

[Daedelus]

Under SOLAS V you are required to fit a radar reflector if practicable, which more or less means fit one.

 

[JonWA]

Under SOLAS V you are required to fit a radar reflector if practicable, which more or less means fit one.

Interesting, I’m considering same issue MG 599 has similar advice and quotes some figures for visibility (7.4). I might look at active reflector as the figures for passive aren’t that great unless a bulky version is used. I had a bulky mast mounted reflector on the previous boat, but that had self tacking jib so the sail didn’t catch on fittings, new boat has overlapping jib, plus I don't want any weight at height if I can avoid it.

 

[lask]

I am aware of the variables of when it comes to radar range, such as the height of the radar, height of the target, power of the radar, sea conditions, etc.

Someone was telling me recently that a sailing yacht, even with the sails up, has very poor radar reflective capabilities. According to him a large ship with a radar mounted high up, in most cases could only see a 30 foot sailing vessel from only 3 nautical miles away!

Is this true?

I'm sure we have some recreational users with radars fitted, is a small sailing vessel without any radar reflectors really only visible from within a few miles?

To find the visibility distance of the radar you must do the following a) square root of the height of the radar reflector X 2.04 = Ν.Μ
B) square root of the height (in meters) of the radar antenna X 2.04 = N.M
C) N.M + N.M = visibility distance