[In
an earlier life our Technical Director, Chris Price, was something of
an adventurous soul. As well as being a confirmed real-world hard tech
enthusiast who disbelieves anything spoken or written that accords with
conventional wisdom, in many areas, as in his words "Why listen to
people who are only repeating what someone who was wrong told them?",
he's been a technical author, the UK's senior English coach of Thai
Boxing, a long-distance singlehanded ocean cruising sailor, and of
course a lifetime engineer in everything from gunmaking through radio
transmission to marine engineering, before the Internet evolved. One or
two of those facets are combined here.]
Articles
Photos
Saiboat Radar - 3 [this page]
Tales From The Atlantic - Dorado Talk
I
include this article on the technical issues affecting long-range
shorthanded small boat sailors as an example of our copywriting. It's
relevant because many of our clients do not wish to admit either the
extent of our involvement in their projects or the fact their site
material is not all of in-house origin - so we can't advertise it.
That's fair enough, naturally, as discretion often has to be employed,
especially where we sub-contract for others. But you can at least see
that we are not semi-literate, and have a life outside the virtual one.
This
tale of course is from real life - and what a great life it was too,
out there on the distant briny. I knocked up one or two of these
articles after a long-term cruising break that involved the
investigation of various maritime facilities around the North and South
Atlantic and the Indian Ocean. Though I'm only putting it that way in
case I can give it a tax spin somehow...
Mostly,
the articles proved too long and too hard-tech to be of interest to
magazine editors, with a couple of exceptions. Perhaps I'll put some of
them up here on this site, and you can see who you're dealing with,
since contracting with pimply young computerists or other faceless
operators may be unattractive to some. And if you want to publish 'em
it's first come, first-served.
Parts 1
and 2 in this series, Real-World Radar, detailed the best ways to
install and use a radar on a small boat for best effect. In the sailing
world, the term 'small boat' is relative, and means anything under 60
feet or so. This article details the practical use of modern radar on a
sailboat, and what you can expect in use offshore.
Chris
Real-World Radar Part 3 - A Tale Of Two Ships
Earlier, we looked at how to set up your Guard Zone, and various other topics of interest.
Here is an 'on-the-water' example of radars in actual use. It is always best to assume
that you can't be seen, in a small vessel, and here's a tale to illustrate the point.
Heading home
En route from the Azores back to England, I was in mid-ocean and more
than halfway to the Western Approaches, taking a slight curve up and
out to the north-west to stay away from Biscay, traffic, and land.
About eight hundred miles behind, and four hundred or so to go.
Falmouth, that snug and welcoming port on the southwest tip of the
country, was the intended landfall. June in the North Atlantic had been
a little windless, and certainly warm enough, out in the Portuguese
islands so far from the mainland; now with the Channel up ahead, the
wind was filling in nicely. My radar was running 24/7 on guard
zone / sleep timer, on the 12 mile range setting, as it often is while
singlehanding and off-soundings. The weather was perfect for a quick
and comfortable passage: a fine and breezy day with a Force 5
south-westerly right up the transom, and the boat was flying downwind
in perfect ease with maybe two-metre waves or so helping us along. It
wouldn't have been half so pleasant going the other way, though.
The genny was poled out on one side, triangulated and bowsed down with
a foreguy on the pole end; the main winged out on the other, boom
preventer locking it solid just off the spreaders. The towed turbine
generator pumped so many amps into the battery that the regulator
regularly cut in to dump the power. From my point of view
there was hardly any sea, and the radar's Sea Clutter control was on
its standard Auto setting. In fact that setting was probably a little
advanced by the radar itself to cut out the occasional small and
fast-disappearing wave reflections, from the wave faces behind me
upwind. Usually, a small wave won't set the alarm off with the Sea
Clutter set to Auto because the radar needs to see the target on more
than one pass to trigger it. Once things get choppy, though, you have
to go onto manual and advance the filter a bit, since the larger waves
last longer in the radar's vision. The centre circle of 'blindness' is
also expanded. With the radome on a pole mount at the stern, sea
clutter is less of a problem anyway than with a mast mounting, which is
normally several metres higher. Guard zone alarm
In mid afternoon the radar alarm went off, and I switched to full-time
transmit. A target showed up right on the nose at seven miles range.
After a minute or so he was still on the same rough bearing, so I
switched Long Wakes on, put a VRM on him, and also an EBL. After a
while, I could see he was coming right down the line. Time
passed – not that much of it, though – and he rose steadily over the
horizon on the bow. At two miles distant, he proved to be a fair-sized
white cargo ship of indeterminate type, since with a bow-on view it
wasn't possible to see. Probably about three or four thousand tons, and
with a fairly low bridge structure. Nothing much to a VLCC, but big
enough compared to a little rock-dodger like me. By this time it looked
as if I would hit him on the port bow, as his target echo was just a
whisker off to the side of the EBL. A quick tweak of the direction
control line on the windvane, taking me over a little to starboard, and
we'd avoid an embarrassing coming-together. It would still be close;
but I hadn't seen anyone in a while, and fancied giving him a wave as
we passed. Human contact. I called him up on the radio with
"White ship at xxx North, xxx West, heading southwest, this is the
small white yacht fine on your port bow, s/y Consort, over". No reply,
which is normal on the first shout. By now close enough at a
mile and a half, I can see the spray smashing into his bow and up into
the air. I call again, and back comes a reply this time. "Station calling, this m/v 'shiftyrx' (or something), over". It's not unusual for a ship replying to these calls to give an unreadable name – or no name – for various reasons. No problem. "Good day to you Sir, just calling you up to say please stand on, stand on, I will take avoiding action, I will move. Over." He comes back with "Sorry, what you say, I can't see you."
Foreign accent of some kind, not north European. So, I repeat the bit
about how I'm in front of him, but please keep going, I'll move over if
necessary. He has now realised I must be speaking to him – this is the
open ocean, hundreds of miles from anywhere, we're on short range VHF
(I'm using my handheld in the cockpit at 1 watt), and there's no one
else about; again, this is a common reaction from ships in mid-ocean. "OK, understand you, but I can't see you."
At one mile now, the waves are smashing into his bow and the spray
flies high up and back. I hadn't realised the sea state, at least the
sea state if you were going upwind under power as he was. No doubt the
wave faces were steep, and would seem higher than they were to me,
running downhill easily with the windvane holding us rock-solid on
course. I imagine him searching for me with his binoculars, twiddling
dials on the radar, running around trying to find the phantom VHF
voice. Or maybe just putting his coffee down slowly, stretching in a
leisurely fashion, getting off his chair, and cursing yotters to his
mate with a laugh. Seen at last Now I'm close under his bow, or so it feels after a week out in the open ocean. Is he blind? At half a mile he comes on: "OK, OK I can just see you now. Yes, I have you. It is rough for you today, yes? Very rough?"
I am surprised, but refrain from suggesting that he get himself a
decent boat. I agree with him and we chat as I pass, a cable off, down
his port side. I tell him it's not so bad for me, going downwind. He
comes out on the bridge wing and we wave. When he goes back in to the
radio, I wish him a good watch and sign off. I sense his disbelief that
anyone would go out so far away from anywhere, in such a small boat, in
'rough weather' like this. Man, he should see the Agulhas current on a
bad day... All round, a pleasant interlude and an interesting
meeting, head on in the middle of nowhere. Food for thought, indeed.
Though perhaps with me heading for the Channel, and him leaving it and
maybe making for the US east coast, it's not so unlikely. But I can
tell you right now that he would never have seen me at all if I hadn't
told him I was there. And I doubt very much if they would even have
felt the bump. My expensive radar reflector didn't help much - as
anyone who has tried to pull small radar targets out of a rough sea
will tell you. Why did his radar not work?
There are three very good reasons for this. Firstly, with the high
scanner position on a ship, sea clutter is always a problem when the
sea gets up. It is a fallacy to state that a high position for a radar
scanner is a good idea. It certainly is, in a flat calm. In an F4 and
above the opposite holds true. Since I feel that the risks are higher
in brisk weather, I always install radar scanners as low as possible
commensurate with safety (ie above head height). If you have two
radars, then the obvious course is to install one high, one low; but
with one set only, if you're betting your life on it - install the
scanner low. Secondly, heading upwind as he was, the worst
place to pick out a small target would be dead ahead, where the
reflections off the wave faces would black out a large portion of the
screen. The Sea Clutter filter solves that, but it removes a small
target as well. Thirdly, don't forget that with a white hull,
white deck, white sails, and a white sea, you're about as visible as a
polar bear on a glacier. You have deliberately camouflaged yourself in
the most effective way possible. The most common thing watchkeepers
always say, when the sea gets up, is that they can't see you. And the
same thing's going to apply on radar if you're upwind of them. So if they're bigger than you, stay out of their way…
Points worth noting:
- It cannot be a common event to meet head on in mid-ocean, in the middle of nowhere. It had certainly never happened to me before; in fact I doubted whether it was possible. Although it's a commonly-quoted situation in those minimum visual time-to-impact scenarios, of course you always think "Yeah, right". Nevertheless, it just shows that it can happen.
- However, this happens frequently in coastal navigation now, with everyone using waypoint navigation: buoy-hopping brings up this sort of meeting regularly. I have lost count of the number of vessels met virtually head-on either at waypoints or even halfway between. A good reason never to set your waypoints right on a buoy, but at least a quarter-mile or so off, if you have the water to do so.
- Bow-to-bow gives the worst possible radar aspect – you're in Stealth mode. In one sense it reassures, in that the yacht radar clearly outperformed the ship radar by a huge margin; in another way, it is of course a little disconcerting.
- Without an efficient radar running on Guard Zone / Sleep Timer, the event might have had a rather different conclusion. This particular situation would have tested watchkeeping without radar to the limit: singlehanded, running downwind at a good speed, and therefore a very short time from the other vessel appearing over the horizon to impact; the sails poled out wing-and-wing, and partly obscuring the view ahead.
- Make sure your radar reflector is efficient; also give some thought to eliminating Fresnel zones (blind areas where you are invisible). See earlier articles for this.
- Finally - finally - after deliberating over this point for so long, and evading the increased cost while worrying pointlessly about other people's comments (even the sailmaker queried it and was reluctant), my new genoa has the top third in HVO (hi-vis orange), and my next mainsail will be the same, to match.
|
(This article came out around 1,800 words - which is short by my terms but still miles too long for most magazine work.) |
|
