peter gibbs
Active member
The answer is clear. Whatever return your current rig shows, it will be enhanced by a reflector (Firdell type) in almost all conditions. Wet sails are said to enhance a return but this is of variable reliability.
PWG
Sailing yacht radar visibility
- Thread starter The Professional
- Start date
PWG
Robin
Well-known member
With a Firdell Blipper mast mounted on a W33 ketch we were visible to Ushant Traffic control at 20 miles when I called them to ask about current visibility in Chenal du Four as we were in thick thick fog, they asked our position and told us they had us clear on their radar and said if we had problems once in the four the St Matthieu signal station could talk us through on their radar. We had our own radar and a dGPS plotter with tried and trusted waypoints and routes so no problem once we decided not to divert elsewhere just in case. The fog vanished anyway half way through the four.
Topcat47
Well-known member
During a fraught channel crossing from Alderney, a few years ago, I was in touch with a container vessel "The City of New York". The deck officer had me on screen for three hours before passing me to a Condor Ferry. 3 hours @ 20 knots (his speed not mine) suggests to me he was still seeing my Nich'26 at 30 odd miles range. I do have a Cyclops 1 mounted on my masthead, which is unaffected by heel, but it's still reassuring to know. I have no AIS or transponder fitted so it's all down to the reflector. The Condor Ferry deck officer kept me aware of traffic until he handed me off to Solent Coast Guard when I got in VHF Range. It was still a great relief when the fog lifted, I can assure you.
Sandy
Well-known member
TomTom has probably lost the "stick to the marked road" function and the motorway is actually to the right of its mapped position.
At a Royal Institute of Navigation I raised the question about how up to date some charts were. Some struggled with the concept that we are still using surveys done over a century ago.
Daydream believer
Well-known member
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Daydream believer
Well-known member
Circa 7 years ago, but note the area-I understand that Roche Douvres are noted for compass anomalies.although i may be wrong on that as I have never noticed anything on my Sestral & that is my compass of choice . It has been helping me get lost for the past 53 years without fail
Not sure if that has an effect
Sandy
Well-known member
It would be interesting to know how high their radar is above sea level and the length of the antenna, I recall from my RYA course that the longer your antenna the better the picture.
TernVI
Well-known member
GPS can sometimes be wrong if signals are weak or there is interference.
A century isn't a big deal in geology.
grumpy_o_g
Well-known member
In a calm sea with not much swell and no fog or rain, assuming a fibreglass yacht with an aluminium mast with stainless steel rigging I'd guess at a 50% chance. In a rough sea with heavy swell and some fog and rain I'd give it a 5% chance at best.
There are so many variables (including whether or not someone's actually looking at the screen) that those could be out in either direction by a few orders of magnitude. I have probably been generous with the estimates, if anything I'd say the chances are lower. Unless it's an active transponder (which is technically not a radar reflector) a radar reflector will make little to no difference.
Factors:
Is anyone looking at the display?
Are you on a collision course (if you are you may trigger an alarm which will get noticed)
What size is the radar antenna?
What frequency is the radar?
What power is the radar (20 miles is a long way for a small "leisure class" radar).
What type of radar is it (FMCW,CHIRP, etc.)?
What is the height and position of the radar antenna?
Is the radar fully servicable?
Is the radar correctly set up and tuned?
How good is the operator?
What is the relative heading of your boat?
Is your boat heeled or upright?
Is your boat rolling and pitching or holding a reasonably consistent attitude?
What is your boat made of (how much steel, aluminium, etc.) and where is that material?
What shape is your boat?
How fast are you moving relative to the ground?
How fast are you moving relative to the radar antenna illuminating you?
How much other traffic around you?
How much stuff nearby that would give similar small returns?
What is behind you (a big cliff would possibly hide return)
What is between you and the antenna (obviously an oil tanker will hide you but you might suddenly from from behind the tanker the other vessel has altered course to pass behind).
I'm sure there's a load of others but that gives some idea...
TernVI
Well-known member
A ship's radar needs some vertical antenna beamwidth to allow for the ship rolling.
A shore station radar doesn't need that, unless it's looking for planes.
An antenna is a little bit like a lens, a narrow beam focuses more energy at the target and magnifies the return.
I'd expect the radar at a major shore station to seriously outperform the average ship radar.
TernVI
Well-known member
I think the main one:
is a skilled operator trying quite hard to decide if that little splodge on the screen is a boat or not?'
grumpy_o_g
Well-known member
I like the lens analogy. Another plus for a shore station is trained and experienced operators who know their kit and will be watching it.
grumpy_o_g
Well-known member
Gary Fox
N/A
Ships navigate by radar, so yes to the RTE, and no to the AIS.
Pye_End
Well-known member
YM did some tests on radar relectors a few years ago, and you may find their results interesting:
https://keyassets.timeincuk.net/ins...20/filebank/reflector_performance_ym_june.pdf
Also note SOLAS requirement: SOLAS V 19.2.1.7 requires vessels if less than 150 gross tonnage and if practicable, [shall have] a radar reflector or other means, to enable detection by ships navigating by radar at both 9 and 3 GHz.
Fitting one can only be a good thing, but make sure it is a decent one.
john_morris_uk
Well-known member
The OP seems to have disappeared.
The Professional
New member
In less than a day?
Anyway there's all kinds of things flying around. Some say less than 1km, some say 8-10 nm, some say 20 nm....
So all I can reasonably take away is a sailing vessel probably at most can be seen on radar from 20nm away
JonWA
Member
Lost the will to reflect
Robin
Well-known member
who could blame him.
James_Calvert
Well-known member
Had a night flight on a Nimrod once, nice invite for a civvy.
We had a tasking on the English S Coast, and were somewhere near the Isle of Wight. The radar operators weren't involved and happy to demonstrate what they could pick up across the channel and beyond. I remember being very impressed.
In some other context I recall being told that the echo from a plastic or wooden yacht is from its interface with the sea, that is the radar is getting its echo from the hole the boat makes in the water. Probably works better beam on...
We had a tasking on the English S Coast, and were somewhere near the Isle of Wight. The radar operators weren't involved and happy to demonstrate what they could pick up across the channel and beyond. I remember being very impressed.
In some other context I recall being told that the echo from a plastic or wooden yacht is from its interface with the sea, that is the radar is getting its echo from the hole the boat makes in the water. Probably works better beam on...
