Radar

[benjenbav]

Serious question for a Friday; sorry if this sounds a bit PBO. I am thinking about getting radar. Having read quite a bit about the various advantages, I would appreciate any thoughts about what kit to buy. For the time being I am unlikely to do much more than daytime coastal hops in the Solent area and, in reality, it's probably about as much use to me as a defibrillator. Nevertheless I thought it would be handy to get familiar with the basics in case the opportunity arises to do some more serious passage making. I was considering the JRC 1000.

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[jimi]

Went through a similar process a couple of years ago and got the SL72, I now wish I had Marpa. I am considering upgrading to a C70 which has a combined Radar(with Marpa)/Chartplotter. Something like the Wahkunha(sp?) highlights to me the importance of being able to estimate the CPA,course & speed of large vessels and I feel that it is unlikely that I'll do full manual radar plots of targets.

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[tome]

The Wahkunha(sp?) was fitted with MARPA, appears that nobody knew how to use it!

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[jamesjermain]

Ultimately I would say you should get a MARPA capable set if you can possibly afford it. But if you just want to get the feel of radar while messing about in the Solent, then a J100 or any other cheap and basic set will do the job. Remember that, by and large, the cheaper the set the poorer the resolution. Bearing accuracy will be considerable degraded but range information should still be reasonably good.

The cheaper sets will be better than nothing in shipping lanes in poor visibility. You will know something is out there and should be able to do a rough plot. But don't aim to get closer than two miles from anything for safety's sake.

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[jimi]

Absolutely .. no point in having the tools if you can't use them ... bet you that when they were dithering in the path that the skipper wished he'd learnt to use it!!

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[Sans Bateau]

The C series kit is realy nice, I had the pleasure of sailing on a friends yacht that has a C70 system, very impressed.

Did you also know that every 8th radar scanner that Raymarine produce is hoisted to the roof and given a 'live' test?

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[jamesjermain]

This was a bit of a puzzle when the report was published becasue MARPA is so incredibly easy to use. Of course it's useless if it's not switched on.

But even with MARPA, sensible margins for error have to be allowed. In poor visibility mid-Channel I would want two miles between me and big ships - I might tolerate a mile in the shipping lanes, otherwise I would never get through.

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[zefender]

MARPA units are likely to fall in price eventually but for now, I'd be inclined to get a basic set. I bought a JRC2000 (CRT, clearer display than the TFT equivilent IMHO) from the US at less than the cost of a 1000 in UK. In admittedly very calm weather it picked up a paint can lid from about 2 miles away and is thus perfectly good for picking up big (and small) ships in channel etc. Personally, I find the plotter/radar overlay displays less clear and they're certainly expensive by comparison.

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[benjenbav]

Thanks all for these comments. I think the choice for me boils down to a cheap set to get the feel of radar or full bells and whistles MARPA capable, head-up, gyro stabilised etc which I can't really justify for my current sailing.

James - have enjoyed your articles on radar in YM.

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[jimi]

One thing that may be worth thinking about is to get the cheapest available that is upgradeable to MArpa in the future. I've been led to believe that my autopilot fluxgate compass is going to be adequate for Marpa because I'm unlikely to be fast enough to make it difficult to acquire targets.

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[JeremyF]

Given the cost in your time, or someone else's labour, I would strech to a JRC 1500. Its a bit more expensive, but the larger radome means better discrimination.

A radar (plus a day's RYA training, and own-boat practise) does not do much for reduced viz in the Solent, but once out makes reduced viz no longer 'Oh Hell' issue.

Last year I had a very chilled trip from Weymouth to Poole despite visibility closing to 1/2 mile.

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[tome]

JJ

If you look at the IMO specifications for ARPA, then even the figures you state look optimistic! This is with large open-array radars with much better bearing discrimination than our leisure sets, generally stabilised with full blown gyros. They state for crossing situations (which is when we'd be most likely to make use of it) a CPA accuracy of 1.8 miles for a 1 minute plot and 0.7 miles for a 3 minute plot.

Agree that ARPA is very easy to use, but there can be problems with maintaining lock in a seaway and target swapping etc in high density areas. Despite these limitations, agree that it would be my first choice and a great help to most crews who cannot spare a dedicated operator.

Tom

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[jimi]

I know there are exceptions and you've had personal experience of thick fog in F8 but generally fog in shipping lanes is more likely in calm conditions .... certainly the Wahkhuna was in an absolutely flat sea.

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[tome]

It's not your speed but your erratic heading which is the factor. In a lively seaway, your course can alter at >20 deg/sec and a slow autopilot compass with probably an update per second won't provide the MARPA processor with a fast enough heading response to maintain lock. Result is that it fails to track - I think some people have experienced this. A fast compass will output heading at least 10x per sec and is essential, gyros on big ships will often be 20/sec plus.

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[Talbot]

A cheap radar that displays so that you can see it from the helm position is worth considerably more than an expensive all knobs and whistles job that only gets looked at occasionally. Furthermore it is easier to get used to what you see on the display if you can also see the reality. Most people with a radar are not really conversant with their equipment, and thus can be led astray - this can be more dangerous than not having a radar.

A display that shares radar and plotting information is much more confusing than individual displays.

I had planned to import a JRC 1500 from the states, but was lucky enough to buy a Furuno 1632 from ebay for about the same sort of money

(I have 30 + years of experience with radar)

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[Jools_of_Top_Cat]

But the scanner rotates once every three seconds, so surely keeping up with that is all that is required, or there abouts. A ships movement can only be noted when she is being painted.

I have been playing with my system this summer in good conditions with only a gps input. I have had favourable results from MARPA that correspond with what I see with my eyes. I will get a compass, but this has led me to believe on a stable cruising yacht spending £600 + would not be worth it. A standard 10Hz fluxgate would be adequate for my use.

I have discovered a few things about marpa that can be a tad annoying.

Trawlers turning into my path will set off the alarm, which seems to keep beeping until I reset, even though they have turned off and no longer pose a threat.

Fixing a marpa target onto a transit van on the coast road can be very confusing.

All in, this is a great tool and if I sell the boat I am taking the radar with me!

<hr width=100% size=1>Julian

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[IanR]

I agree with the post on experience and a reasonable set being of potentianllt greater value than just MARPA and hope

I have just come back from the Channel islands where after a couple of weeks of sailing and using the radar on watch to check collision risks in fine vis and foul. I can say that having a JRC 1500 on board to navigate through the rocks around Herm, combined with a good GPS plotter, made an otherwise impossible trip in limited visibility a viable challenge and after a drink (on arrival) an enormously valuable learning experience for both my helm (SWMBO) and myself

Go for it, but I really recommend the practice and the RYA course on a simulator for a fast take up!

I agree that with the directional swinging of a yacht on a non dampened display can make it more difficult but it is very possible to do your own MARPA if you know how to plot from the display to paper(RYA course benefit again)

Cheers
Ian

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[Jools_of_Top_Cat]

Sorry Mark but I disagree. MARPA is the way forward for small RADAR, especially for short crews. I am also more convinced SWMBO will be able to use MARPA far more easily than plotting.

MARPA or ARPA is not bells and whistles, it is what a GPS is to a sextant, MARPA is to a plotting sheet. Squillions faster and more accurate.

<hr width=100% size=1>Julian

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[AlexL]

I've got a JRC1000 which is perfectly adequate, the screen is easily visible even in the brightest sun - cost about 700 odd quid and I fitted it myself. For my new boat (which is another story - new boat arrives in early new year) I am probably going for a C80, attached to a raymarine S1G autopilot computer which will give the gyro stabalised MARPA heading inputs, however the price is alot more. The C80 with a radome is about 2 grand, plus you need a gyro compass, however if you have a raymarine inboard pilot this will do the job, and it probably needs to be professionally installed and comissioned. IMHO go for either a cheap JRC1000 or a full MARPA set, I can't really see the point of going in-between.

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[Talbot]

I think we will have to disagree Julian. Marpa is very nice, but does require additional electronics, and is definitely better on a 24" 4kw radar. All of which adds a power overhead that a lot of yachts would find dificulty in maintaining.
But the main reason I do not like it is, that the human eye is still a better detector of poor radar returns than the best automated systems.
I think that the eventual way ahead will be by use of the AIS, but I still think the best and quickest method will remain looking at a stabilised raw display. Provided you are using ghost trails (afterglow of previous contact positions), an experienced operator can almost instantly recognise the threat tracks.

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