st599
Well-known member
Couldn't you just take the time off the GPS?
No, you need UTC not GPS time.
Watch-chronometers
- Thread starter oldbilbo
- Start date
No, you need UTC not GPS time.
jwilson
Well-known member
I absolutely LOVE plotters and GPS, but if seriously offshore still carry a sextant and tables and paper, pencils and a chart. And whilst Casio digital watches do contain phenomenally complicated electronics, they are possibly the most reliable examples of such complex electronics ever made, as long as you do not open them up to change the battery.
Also, even if both your Casios do die, you can still find your latitude, which is much, much better than being completely unaware of where you are in relation to the rocky bits.
The cloudy sky bit is true, and before GPS existed I have been several very horrible very lumpy days without a sight and with a circle of uncertainty of position of 50-100 miles.
Also, like many others, I actually enjoy using the skills occasionally, to keep my hand in. My own boat has two independent GPS/plotters, plus a "waterproof" handheld GPS in the "waterproof" flares box.
Long experience has shown that with the honourable exception of Casio digital watches, not much is really "waterproof" in extreme conditions.
JayBee
Member
J Wilson says it well.
At the last count I had six GPS receivers on board.
One for each of the following:
Radar/Chartplotter
DSC VHF plus AIS Watchmate
Backup Chartplotter
Laptop dongle
PDA
Emergency spare.
They are great to have and I love them all, but it's also good to think that I don't really need any of them.
At the last count I had six GPS receivers on board.
One for each of the following:
Radar/Chartplotter
DSC VHF plus AIS Watchmate
Backup Chartplotter
Laptop dongle
PDA
Emergency spare.
They are great to have and I love them all, but it's also good to think that I don't really need any of them.
oldbilbo
...
Pete, m'dear, while commending your competitive spirit, may I encourage an comparative approach that is rather less likely to result in the destruction of one or more perfectly innocent navaids?
Instead, you could take the two disputatious navigators, drop them ten feet onto a concrete floor, then stir them around in a large bucker of seawater for a couple of days.
'Most accurate position obtained afterwards wins.'
Akshully, while this slow and uncertain pilgrim has accumulated, over the years, a bookshelf or three of printed seamanship and navigation lore, the most valuable by far for us yotties - in the sense of 'best bang for buck' and instant understanding - is IMHO the 'Complete Works of Mike Peyton', and I commend his several publications to all students of the 'Haven Finding Arts'.
Here's an example....
jwilson
Well-known member
I have twice been on boats deep-sea when EVERYTHING electronic and much of the electrics was dead due to far too much salt water sloshing around below. On the first occasion pre-GPS the electronics were just speed/log/depth and a radio, on the second much more recent occasion we had fixed GPS and "waterproof" handheld GPS both dead, though the handheld GPS did eventually resume working after its insides were washed out in fresh water and dried in a low oven. In the meantime I was pleased to have a sextant and tables.
On my current boat the spare waterproof handheld is normally in the waterproof flares box.....
Kukri
Well-known member
Thinking along those lines, I have decided to re-fit the ancient grey box B&G echosounder, on the grounds that the event that made B&G's name, when they were still working out of garden sheds, in the fifties, was the sinking of a yacht which, when raised three weeks later, had her B&G echosounder still working.
AntarcticPilot
Well-known member
Nice try
My sextant is as good as the day it left Carl Plath's works in Hamburg, 50 years ago. How do you think your GPS receiver will be functioning in 2062?
Let's get real. There is no concrete floor in my boat with a ten foot drop.
I can keep my almanac, tables and plotting sheets (don't actually need the latter) in your hypothetical tin box.
Even without a sextant, almanac and tables, my interest in astro-nav has given me some tools to cope with emergency navigation, in a way probably not available to those spoon fed by a mysterious little black box.
There are also (somewhat approximate) techniques using a sextant that do not need tables or time. You can get your latitude to better than a degree with a sight on Polaris, for example. And graphical averaging of successive latitudes might well allow you to do better. You don't need tables to determine longitude from a noon sight either - just a source of UTC. And the watch on my wrist is MUCH more robust than any GPS. So, without tables or UTC you can get latitude; without tables but with UTC you can get a latitude and longitude. Crude, but good enough to make a land-fall.
Of course, Captain Cook sailed with only an ephemeris for the first two years of his third voyage - they computed the ephemeris for later years on board, including the lunar ephemeris which is decidedly difficult to do. I'm not saying that we should do the same - just pointing out that the tables and so on are an aid, not ABSOLUTELY essential. Not that I am astronomer enough to compute an ephemeris!
BruceDanforth
Well-known member
Well I took a set of sights with my trusty plastic lifeboat sextant from Panama down to Oz with a casio watch checked against the sw radio and the biggest source of errors seemed to be in judging the horizon and the verticalness of the sextant accurately on a boat in motion rather than the actual instruments. Having a reasonable DR and not getting lost in the first place seemed to help and I was rarely too far out from the GPS. Certainly not far out enough to miss a continent though I'm not sure I'd have liked to try and find the Galapagos etc.
oldbilbo
...
Aye, that....
There's a whole lot of verbiage to wade through before any 'nuggets' are disclosed - unless one has a passion for lyric poesy.
I didn't manage Canto III....
Further, and to amuse the moboistas among us, I have neither shot for Lower Mer Pass, not squatted in the ordure of a dinghy towed alongside in a murky Red Sea, chasing a single LOP as a Clearing Line for a bunch of ill-surveyed coral reefs one had no business being anywhere near.
On t'other hand, I have oft times colluded in a series of simultaneous two-star fixes ( ABABABABA ), which were once the staple diet of a Nav Plotter on a V-force 'Vulcan', where the fixing routine required a frequent input to the DR Computer of a) Tracking Error 'P/S' and b) Run Error 'Along'.
A reliable two-star fix 'along and across' provided this, and one used the Precomputed Stars Tables to select suitably-positioned candidate stars.
As for horizon, one plied one's trade above the Tropopause and the weather, so fog was a rarely-encountered inconvenience. The horizon was provided by a Pendulous Reference device within the periscopic sextant - an advance on the bowl of oil beloved of our maritime cousins 7 or 8 miles below.
The fixing routine was directed by Staff Navs working ( if that is an appropriate description ) in some comfort at Group Headquarters. They tended to require 4 astro fixes per hour, shot, reduced, plotted and used. Day and night. It was a 'stand up interview' event to produce less.
For the various NATO and InterSquadron Bombing Competitions, the pace was increased, and all the instruments 'tweaked until they squeaked'. The results gave our Command Select crews frequent wins against the very best that SAC could muster - and a lot of tax$$$$ were spent in seeking to outgun us - in an era when the average RAF squadron bomber crew would routinely fly a 1500 nm leg out over the Atlantic, at over 40,000 feet and using only astro, returning down an 'alley in the sky' a quarter mile wide, to 'release' a notional bomb over Lincolnshire within 20 seconds of pre-planned time.
The best could regularly demonstrate a 'alley' half that wide, and a time error of better than 10 seconds, on what was called the 'DR Bomb' profile.
Teamwork was at the core of this. The Vulcan was fitted with TWO periscopic sextants, and it was far from unknown for them to be employed simultaneously - the NavRad shooting precomputed stars from the starboard one, with the AEO shooting the same from the port hole, while the Nav Plotter pre-computed, recorded the results, applied the 'corrections'. and fed in the results. That's effectively a 14-shot 2-star simultaneous sandwich fix, sustained during the final leg of such a competition navex for more than an hour. The Pilots 1 & 2 busied themselves with the sandwiches and Twix bars during all this. .....Oh, and a fixing cycle of 12 minutes. Busy bees....
I cannot mention the calculated CEP that such 'aces' could reliably achieve, but it was of the order of 'which end of the tennis court do you want'......
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JayBee
Member
"For he who strives the tempest to disarm Will never first embrail the lee yard-arm,"
Maybe the bosun was not up to speed on this evolution.
Intrigued by Minn's Falconer quote, I found this:
Title: The Lieutenant and Commander
Being Autobigraphical Sketches of His Own Career, from
Fragments of Voyages and Travels
Author: Basil Hall
“The mainsail is now to be taken in; and as the method of performing
this evolution has long been a subject of hot controversy at sea, I
take the opportunity of saying, that Falconer's couplet,--
"For he who strives the tempest to disarm
Will never first embrail the lee yard-arm"
has, in my opinion, done a world of mischief, and split many thousands
of sails.
I, at least, plead guilty to having been sadly misled by this
authority for many years, since it was only in the last ship I
commanded that I learned the true way to take in the mainsail when it
blows hard. The best practice certainly is, to man both buntlines and
the lee leechline well, and then to haul the LEE clew-garnet close up,
before starting the tack or slacking the bowline. By attending to
these directions, the spar is not only instantaneously relieved, but
the leeward half of the sail walks sweetly and quietly up to the yard,
without giving a single flap. After which the weather-clew comes up
almost of itself, and without risk or trouble.”
And indeed years ago I got shouted at by a bosun for doing exactly that!
Pete
Maybe the bosun was not up to speed on this evolution.
Intrigued by Minn's Falconer quote, I found this:
Title: The Lieutenant and Commander
Being Autobigraphical Sketches of His Own Career, from
Fragments of Voyages and Travels
Author: Basil Hall
“The mainsail is now to be taken in; and as the method of performing
this evolution has long been a subject of hot controversy at sea, I
take the opportunity of saying, that Falconer's couplet,--
"For he who strives the tempest to disarm
Will never first embrail the lee yard-arm"
has, in my opinion, done a world of mischief, and split many thousands
of sails.
I, at least, plead guilty to having been sadly misled by this
authority for many years, since it was only in the last ship I
commanded that I learned the true way to take in the mainsail when it
blows hard. The best practice certainly is, to man both buntlines and
the lee leechline well, and then to haul the LEE clew-garnet close up,
before starting the tack or slacking the bowline. By attending to
these directions, the spar is not only instantaneously relieved, but
the leeward half of the sail walks sweetly and quietly up to the yard,
without giving a single flap. After which the weather-clew comes up
almost of itself, and without risk or trouble.”
oldbilbo
...
Good stuff being squeezed out, now. Takes a while, but well worth it....
JayBee
Member
oldbilbo
You and Lady Campanula should get together, if you don't know one another already, which somehow seems unlikely.......
Hang on - maybe you ARE Lady Campanula
You and Lady Campanula should get together, if you don't know one another already, which somehow seems unlikely.......
Hang on - maybe you ARE Lady Campanula
prv
Well-known member
Ah, well, not knowing the context, I assumed the couplet referred to stowing rather than handing. Also, I was thinking of topsails rather than the mainsail, as in a "tempest" the courses on Stavros or William would have been long-since stowed.
On those ships we would generally hand both sides of the sail together; which one came up first would depend only on the relative enthusiasm, skill, and, muscle-power of the two teams hauling on the buntlines and clewlines.
What I was loudly advised by the bosun not to do, was to start the sea-stow with the clew gasket as we would do for a harbour stow or in less wind. Instead, by working outwards along the yard with the ordinary gaskets, you progressively snuff the wind out of the sail and prevent it trying to throw you off the yard. When you reach the clew you do the clew gasket, now lifting only a small corner of sail instead of catching the wind in all of it.
Unfortunately, you will probably need to re-do most of the normal gaskets on your way back in, as lifting the clew will have allowed the sail to stow tighter (why you do it first under calmer circumstances). At least the gasket is already fed where it should be, so it's just a matter of untying and re-tying the knot, and if it's that rough then hopefully your stowing crew are people who can tie a slippery hitch one-handed without having to think too hard.
Pete
Cruiser2B
Active member
I'm sure I could look this up, but I want to read your take on this. I thought GPS sets took their time updates from the GPS satellites, that have on board ultra-accurate cesium clocks, that are in turn confirmed against ground stations that take their time from the 'official' atomic clocks, so they show UTC. Am I mistaken?
AntarcticPilot
Well-known member
GPS clocks don't necessarily show UTC; the satellites don't always take account of leap seconds. Also, a navigational GPS always has a delay in it; the time display is not necessarily in sync with the GPS time. The delay can be up to 2 seconds. GPS can be a very precise source of time, but only if the receiver is optimized for time processing; it is used in this way for network time servers, for example. But the GPS on your boat isn't optimized in that way, so it can be seconds off.
JayBee
Member
Unfortunately, I have never been at sea on a square rigger under sail, but out of curiosity have done a bit of reading and got an idea of the normal rigging of a square sail, so hopefully I can see fairly clearly what is going on from your interesting description.
I have piloted a few largish sail training square riggers, (under power and with tug assistance) between the sea and their berths, via a sea lock - interesting enough with half a gale of wind and some tide on the beam. One of the last ones was the barque USCG Eagle (ex-Horst Wessel) which had arrived on this side of the Atlantic from New England, motoring almost all the way for lack of wind!
One priority for the Captain was to land a steel topsail yard for repairs, which had been kinked by the cadets, simultaneously hauling on the braces on both sides. They were big, well fed boys and girls!
Bosun Higgs
N/A
Dont understand all this. There are no end of gaskets on my boat but they are all where they should be inside the two engines.
I vaguely remember something about noon sights from when I did astro - is that the right answer?
You can control the sun, the stars and the weather can you?
Oh, and for Bosun Higgs, can you not conceive of any practical astro procedure(s) where time, even electronic time, is not required? Let me then introduce you to Dr David Lewis and his 'Daughters of the Wind'.....
I vaguely remember something about noon sights from when I did astro - is that the right answer?
You can control the sun, the stars and the weather can you?
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JayBee
Member
I am happy to leave all that to a higher authority than the US Department of Defence.
prv
Well-known member
I bet! Stavros's yards on their own create so much windage that it's not uncommon to have to brace them around during an approach under power as the ship starts sailing under bare poles, even in fairly ordinary weather.
Heh. Not sure I fancy our chances of kinking one of Stavros's topsail yards - that's 1.5 tons of steel tube and the most bodies I ever see on a brace is about half a dozen. Although I do mostly do adult voyages which tend to be shorthanded, so perhaps they might sometimes end up with 12 strapping teenagers on a lower topsail brace.
I guess if we tried hard enough we might be able to spring a royal yard. Climbing on those always feels like hugging a broomhandle
Pete
oldbilbo
...
Far be it for me to talk you out of the many pleasures of 'promiscuous reading', but I can recommend with some confidence 'The Barefoot Navigator' by Lagan and 'The Lo-Tech Navigator' by Crowley. In this latter may I suggest the wrinkle of 'A Trick With Kochab', p.124 as probably worthy of a moment of your time, and possibly 'A Handy Sun Compass', p.35.
If neither of these provokes even a passing flicker of interest, then I am at a loss to know how to entertain you further.