How good is your radar reflector?

[TheBoatman]

On a recent trip to the Emerald Isle I decided to cross via Holyhead on one of the "fast ferries" I won't say which one it was, only that it was fast.

The day I crossed it was sunny with a very light intermitant breeze from the South and the sea state was smooth. We had cleared the head and was running at full cruising speed [I guess about 35 knts] I had already noticed a couple of cruising yachts making the same crossing, judging by their headings.

After about 30 minutes we ran into some sea mist which reduced the vis to less than a mile. The skipper started the fog horn and carried on at the same speed, I noted that he had both near and far radar's working but still no reduction in speed.

It crossed my mind that whilst he thought he was doing the right thing, I did wonder what if a yacht was out here with either no radar reflector or a poor one. By the time either boat had seen each other what would the result be?

I also thought that I was glad to be on board the ferry rather than on a yacht despite it being a wonderful day to cross to Ireland.

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[Jools_of_Top_Cat]

there was a maritime incident report very similar to this attached to the PBO this month.

The reply from the company was something like the fast ferry can stop in her own length or near abouts from full speed. So with Radar ruining and fog horns the captain was considered to be running at a safe speed in the conditions.

Personally I think that was crap, it is not just the ferry's speed and manoeuvrability that comes into question, if I see a target appear on my radar on collision and he is doing 35kts I am going to be wetting myself trying to get out of the way of him and his wash in the 5 minutes prolly 3 after taking some plots and deciding we really do need to move.

It is very un-seaman like not to slow down, being on the water is not a big computer game, where have the old skills gone?

<hr width=100% size=1>Julian

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[bruce]

radar is just another tool, regs req visual lookout, and he would have about one minute to make adjustments.

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[ChrisE]

One less thing to worry about?

Before 9/11, I was on one of the fast cats between Poole and the Channel Islands and asked to go on the bridge and spent a couple of hours watching how these things go about avoiding us. They too were travelling at about 40 knots in low viz.

I was extremely impressed by both the care that the bridge deck crew took in identifying targets and of the sensitivity of their radar. They were spotting dingies, without radar reflectors incidently, at 3 miles (when the viz was about 2 miles) and making decisions about altering course. Sure enough the dingy would loom up out of the murk out of the way of the vessel's course.

As the cats stop running when there is wind forecast over F6, when I'd start to worry about clutter obscuring the view, I no longer worry about these particular crafts abilities to see and avoid me.

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[DogStar]

Re: One less thing to worry about?

I had similar worries bringin my boat from IOW - London. We ran into thick fog (1 cable vis) in a wooden boat with 1 tetrahedral reflector. Whilst we were running in the fog, we weren't sure about the return, but it turned out that we were making a very good return on most commercial radar.

We definitely found in the following days, esp. coming up the Thames estuary, that most of the big ships were reacting to our presence when we could just about spot them. We must still have been li8ttle more than a speck to them at that distance, so they must have been reacting to our return.

Apparently, it is very hard to make even a wooden boat invisible to modern radar.

<hr width=100% size=1>I'd rather have a bottle in front of me than a frontal lobotomy!

 

[MainlySteam]

I think that many judge the performance of radar and the management of plots on larger vessels on the small low capability radars and the usually limited navigation experience held on their own yachts. It is generally regarded that while a smaller radar on a yacht is useful for large target identification, it is only when the antenna is 3' 6" or more (for a 3 cm radar) that the radar is more generally useful for navigation. Obviously sea state has a bearing on identifying small targets, especially if not metallic, but that usually is not an issue in case of fog or mist (and of course the pleasure vessels around in bigger seas tend to be bigger and therefore bigger targets).

The speed of ferries (and other vessels) and maintaining separation has come up quite alot recently and out of interest I, for my own purposes, did some checks and asked some questions. As it has come up again, maybe I can bore the forum with those.

I have recently spent many hours in the wheelhouses of some small commercial vessels (service speed 35 knots) with 3' 6" radar antennas (ie the bottom end of what is regarded as useful for navigation) and some (service speed 23 knots) with 24" antennas (ie probably the largest size found on non superyachts). Some of the hours spent were in poor visibility from mist and all were outside of NZ. Both radars were current models and from the same manufacturer.

The 3' 6" radar could be relied upon implicitly picking up very small non metallic targets from quite far away - certainly anything of the smallest non metallic boat size (Optimist dinghies, for example) - and had the advantage of a larger display size. However, the performance of the 24 " radar was not such that it could be relied upon for plotting and it suffered also from having a smaller display (a larger display may not have added anything except a false sense of confidence) - from that I do not believe that a 24" or smaller radar should be relied upon for plotting separation from other vessels except from maintaining a rough plot by simple watching for vessels that come down the bearing line or close to it. Rather, I would rely on the big vessel to plot me with me taking what I believed was a firm non confusing course maintaining good separation and leave the ship to manage the situation itself. Despite the tracking and collision avoidance aids appearing on small radars, I do not think I would place anything other than use as a broadbrush indication tool on them rather than dependance on them for maintaining separation.

In one instance in very poor visibility from rain mist, with a 3' 6" antenna boat, we were doing around 38 knots and the radar identified a target ahead, and the skipper plotted to pass it to one side. Although there were around 6 of us in the wheelhouse, none of us could see any sign of the other vessel (a small keelboat) until we were close enough for its mast to rise into the slightly lighter background above the horizon. We saw the vessel itself for about 5 seconds as we passed it as plotted.

I also questioned a very experienced ships master friend of mine (is 60 years old and been at sea all of his life) who has skippered container (and other vessels) through the English Channel. He also sails his own yacht and has skippered large sailing vessels to around 120 ft for others. His comments were:

- he would not worry about the fast ferries, they are crewed and equipped for their service
- maintain a course showing clear intentions with any course or speed changes being of obvious and firm intent (ie do not dodder confusing the ships own plot of you, which was probably the final straw that caused the recent running down in the Channel).

Trust that is of some use

John

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