Quote:
Originally Posted by CaptainRivet
. . .
I see 3 main use cases for bluewatercruisers:
Weather: range as far away as possible
Collision avoidance on passage: 10nm is there a ship out there that could collide with me and i could easly avoid eg by changing course 3 degrees. Sure i wanna see as small vessels or obsticals as possible
Collision avoidance dueing resuced visibility (fog/heavy rain...): here as near as possible and as small as possible obstacles are detected. Also is performance compromises through eg heavy rain. . . |
On cruising
boats, unlike on ships (which have much better radars than ours),
AIS is the primary method of collision avoidance, with radar as a (crucial) backup for vessels not transmitting AIS.
There are two very valuable use cases for radar you didn't mention:
1. Pilotage, especially in bad viz. There is nothing on earth you will value more than your radar when trying to enter a strange harbor at night in the rain. Also position fixing in case you
GPS is not working, or to verify what your
GPS tells you. Also verifying
charts. It's good seamanship to verify continuously with radar what you see on the chart plotter, which is super easy with radar overlay. There are many classical radar techniques like parallel indexing which are little practiced these days on recreational vessels, but which are very valuable, and can help you be less dependent on the chart plotter, which is good seamanship.
2. Watchkeeping enhancement -- using guard zones to sound
alarm offshore if an object appears within a certain distance. Very valuable if you don't have crew on watch scanning the horizon every second when far
offshore, or even if you do, because they don't always see everything, especially in the dark or poor viz.
I also use radar at
anchor to keep track of distances to other
boats and to hazards, sometimes using guard zones as an additional type of
anchor alarm. And for measuring distances to other boats when choosing an
anchoring spot -- extremely useful since the eyeballs are really deceptive in this.
In my opinion radar is the most valuable electronic device on board, far more valuable and versatile than the chart plotter.
I'm using a by now pretty old
B&G 4G radar so can't comment on the new ones. All the electronic trickery which has made small radars better in recent years does not solve the big disadvantage of small radars, which is bearing discrimination. It's often said that radar is very accurate for range, but not so much for bearing, and that is much more true, the smaller the radar
antenna. So, the bigger the
antenna (or dome), the better quality your bearings will be, which is very valuable.
A couple of other points about radar, and its desirable qualities:
1. You care very little about long ranges but very much about the ability of the radar at short and very short ranges. As has been said in this thread, you're not going to see much at ranges more than 10 miles anyway due to radar horizon. Also, you're not going to be doing much collision avoidance beyond 10 miles anyway. The first recreational CW radar was the
Simrad BRM (later developed into 3G and 4G), which was considered to suck at long ranges but to be brilliant at very short ranges, and in practice this was very little or no disadvantage at all. The very short range performance is extremely valuable; a great leap forward over older pulse radars. But the poor bearing discrimination from the very small scanner (18") creates disadvantages, and these radars have an extremely poor MARPA implementation. So always go for the biggest scanner you can fit. The new Simrad doppler radars are available with a 24" scanner.
2.
Furuno are considered to have the best MARPA (actually ARPA) implementation. Whether this is really valuable or not depends on how you
work. I've adapted to years of having radars with bad MARPA implementation by not using it, and just doing old fashioned manual radar plots, which I actually prefer. Or just put the EBL on the target and just eyeball whether it's walking down the EBL or not -- extremely quick, dirty, and useful analogue way to detect a collision course.
3. Doppler is surely good for seeing at a glance whether a target is moving, and whether it is moving towards or away from you. I spent some thousands of miles skippering a
boat with one of the new HALO radars and liked that.
4. Radar overlay on the plotter is extremely useful. But to make this
work right, you need to have very precisely aligned scanner and you need very good heading data on your
network (this will also improve MARPA/ARPA performance). It's worth investing in a
satellite compass to get this (which will also improve your
autopilot performance).
For my use case and way of working, the best radar would be a larger open array one. That won't fit on my
boat. But I do think about upgrading my 18" 4G scanner to a 24" HALO one, at least. Some day, because it means I would also have to upgrade the two
B&G plotters.
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