Radar Saved My Azz Yesterday

[weavis]

Originally Posted by Lodesman

You mean damn close to 600 ft?
If you happen to use American charts in any of your travels, you'll get to use fathoms, otherwise as you said, not used much. OTOH, the cable is used plenty - we still do distances in NM (and I assume your radar measures in NM), so whether you use it as such or not, every tenth is a cable.

Now that we've got all that squared away, how about a bit of trivia? Does anyone here know what a 'data mile' (aka 'radar mile') is?

1 Radar Mile = 2 · 1852 m = 12.35 µs
3 · 108 m/s

[DoubleWhisky]

Originally Posted by El Pinguino

I believe Whites(?) used to build warships there.

Yes, You are right. J. Samuel White & Co.
Between other they built in late thirties two destroyers for Polish Navy.
The were between the finest ships of this class in the world for the time.
One (Grom) was sunk by German bombers in Rombakkenfjord near Narvik.



The second one (Błyskawica) become the only ship fighting from the first to last day of WW II in Europe.
In the last part of war it formed the mixed division with another Polish destroyer (Piorun) and HMCS Haida and HMCS Huron from Canadian Navy.



Sorry for the thread drift, but the were so beautiful ships...
Błyskawica exist still as a museum in Gdynia, so if being in Poland, You can visit her.

[gamayun]

Originally Posted by sparau

One would guess that the tanker had AIS and radar and should have been aware of Dockhead in the little plastic floaty thing, also busy channel they would have had active watch and steering. If so is this a case of "I'm bigger, there are heaps of little plastic floaty things around, GTF outta my way"?

Just asking for an indication as to what behaviour to expect from shipping or what size of radar reflector to install

I heard from several friends who were way offshore that whether you show up as a blip on their screen or not, these big ships often just do NOT see you, and it's not uncommon to have to make these evasive maneuvers. Others have said on this forum (or maybe it was the other one...) that if you have an AIS transponder, your little plastic bucket will show up like a giant warning bell that does not go away from their screens and cannot be ignored. IMO, AIS transponder with radar (and a loud horn) would be the best of both worlds.

[s/v Beth]

Since others are telling their "why I got radar stories" I can share mine. September 2011, 2200 and I am crawling up the Columbia bank against an tide. Thick fog from 5 miles out all the way to Astoria (15 miles total). Being a minimalist, all I had was a 5 inch garmin gps. I had always told my friends " if there's fog I will just not sail"
Inching between markers and trying to say out of the way of any traffic that might be out there, I can hear the breakers just north of me. I finally loose my nerve and decide to cross the channel. I haven't heard any foghorns for a while and the channel is only about a quarter of a mile wide there. Half way across the current increases enough that it's hard to control the boat. A lighthouse a mile or so away is lighting up the clouds in an unearthly glow making it even harder to see the channel markers, but by the plotter it looks like I'm getting closer to the south edge of the channel.
Out of the fog not 100 yards from me appears 5 stories of steel travelling at a high rate of speed. "I'm dead" I think, but no his trajectory is off port by about 30 yards. As I watch it go by swear if I make it out of this alive I am never doing this channel again without a radar and a AIS. And I haven't.

[weavis]

Originally Posted by s/v Beth

Since others are telling their "why I got radar stories" I can share mine. September 2011, 2200 and I am crawling up the Columbia bank against an tide. Thick fog from 5 miles out all the way to Astoria (15 miles total). Being a minimalist, all I had was a 5 inch garmin gps. I had always told my friends " if there's fog I will just not sail"
Inching between markers and trying to say out of the way of any traffic that might be out there, I can hear the breakers just north of me. I finally loose my nerve and decide to cross the channel. I haven't heard any foghorns for a while and the channel is only about a quarter of a mile wide there. Half way across the current increases enough that it's hard to control the boat. A lighthouse a mile or so away is lighting up the clouds in an unearthly glow making it even harder to see the channel markers, but by the plotter it looks like I'm getting closer to the south edge of the channel.
Out of the fog not 100 yards from me appears 5 stories of steel travelling at a high rate of speed. "I'm dead" I think, but no his trajectory is off port by about 30 yards. As I watch it go by swear if I make it out of this alive I am never doing this channel again without a radar and a AIS. And I haven't.

Yep. The instant sweat will evaporate any pee you had to wet your pants. Been there, done that....... so very very frightening.

[Lodesman]

Originally Posted by weavis

1 Radar Mile = 2 · 1852 m = 12.35 µs
3 · 108 m/s

That's only part of it. Many radars measure in 'data miles' - that would be 6000 ft vice the 6080 ft in a nautical mile. Doesn't make much of a difference for normal use, but for those aspiring Vasco's who wish to plot long-range radar fixes, it's important to convert data(radar) miles to NM before plotting them on the chart, by subtracting one cable for every 7.5 miles of range.

[downunder]

Dockhead,

Great example of usefulness of radar and AIS. Thanks.

However I expect there will be still cruisers asking wether to install AIS ahead of radar.

The other save your arse use of radar is to check the accuracy of those electronic charts which whilst reliable in some areas need checking.

As the Colision regs say navigate by all means.

Cheers

[Dockhead]

Originally Posted by Viking Sailor

Dockhead, if you please a quick question, was any of the vessels using proper sound signals per COLREGS? I have sailed in foggy and rainy conditions using sound signals to avoid bumping into other vessels. Everybody, just needs to slow down and/or stop while using sound signals to communicate. Also, if it is available, using channel 13 for bridge-to-bridge communications. Don't get me wrong, I am all for technology, but the old ways can still be useful. Paul

Yes, many sound signals, to the point of confusion.

No time for VHF, even if I had not been single handed.

[Dockhead]

Originally Posted by Lodesman

You mean damn close to 600 ft?
If you happen to use American charts in any of your travels, you'll get to use fathoms, otherwise as you said, not used much. OTOH, the cable is used plenty - we still do distances in NM (and I assume your radar measures in NM), so whether you use it as such or not, every tenth is a cable.

Now that we've got all that squared away, how about a bit of trivia? Does anyone here know what a 'data mile' (aka 'radar mile') is?

I agree. Cables are entirely current usage; fathoms much less so, but still not quite obsolete. Every pilot book, I think, uses cables.

[Andrew Troup]

Originally Posted by El Pinguino

I don't think I have ever seen a fathom used to measure length in that way.....you wouldn't say 'we are 200 fathoms of the land'.. length of rope yes ( traditionaly 120 fathoms in a coil) but distance?
...

The strangest use of "fathoms" I have struck is in describing the speed of a sailing ship as "seven knots and three fathoms"

Here's my best guess at what this means.

A streaming hand log was a length of line, which ran out from a wooden spool held aloft by a ship's boy (typically 150 fathoms long, IIRC?)
provided with knots spaced at a whisker under 48 feet. This was so that a sandglass (which ran out in a couple of whiskers under 30 seconds) could be used to establish a time interval, during which the number of knots which had run out would represent the speed of the ship.

Fussy navigators presumably wanted fractions of a knot, and here's my guess at what "seven knots and three fathoms" represented:

When the sandglass ran out, somebody would 'nip' the logline to establish how many knots had run out. (Unless the ship was travelling too fast, giving rise to the expression "ten knots and a boy, sir")

I'm guessing they would then haul the line back to the last knot, measuring it with their arms (the armspan of a grown man being roughly a fathom).

So if it took three handspans to get back to the seventh knot, the speed was "seven knots and three fathoms"

As it happens, this would be near enough to seven and three eighths of a knot, given that the knots are spaced at roughly eight fathoms.

ON EDIT:

One of my least favourite land-lubberly usages (along with "Over and Out!") is

"a speed of eight knots per hour"

If people feel they absolutely *must* qualify the time period, (which does not serve any useful purpose) they should say "a speed of eight knots per twenty-eight seconds"

If they feel *impelled* to say "per hour", then they should say "Eight nautical miles per hour"

Knots per hour is not a unit of speed; it's a unit of acceleration (and a glacially slow one, at that)

Pedantic RANT mode \ OFF

[ElGatoGordo]

I don't have radar, and probably never will. Just doesn't fit my boats/budgets/methodology. But If I were you that day...I would have turned around. Even WITH radar. I don't think it prudent to enter a shipping area in fog regardless of the equipment. What would have been the result if your radar died seconds before the ship turned? You be dead...with radar

Sorta like running over a reef with a big old catamaran in bright sunshine and gin clear water because the electronics said it was a safe route. (not EXACTLY like it...just sorta )

I love my electronics that I have, and fully support having any and all...but I believe it's far more about the mariner than the gear.

I've been caught on Galveston Bay several times by sea fog, and once in the Gulf. I hightail it out of the shipping lanes, slow down, and use sound signals as appropriate.

Flame suit on!

[markpierce]

Originally Posted by carstenb

Fog is horrible - ...

It's coming to get you.

[ElGatoGordo]

THAT is an AWESOME pic!!!!

[weavis]

SO the logical next question is... what Radar does everyone have, or think is the minimum standard for a useful one?

[markpierce]

Busy