Thorny subject: Sextant and GPS era

[Jammer]

Originally Posted by ArmyDaveNY

I think that he was referring to a loss of electricity due to something like a lightening strike or an electrical system failure such as wiring, short, etc.

If your entire electrical system is toast, the experience of others would show that the GPS is the least of your problems. Besides, on passage, everyone carries handheld battery GPSs, and spare batteries, or has those things in the lifeboat.

[Flagman101]

Originally Posted by roverhi

GPS does screw up!!!!!!! On a recent delivery from SF to Oceanside had to duck into Monterey because of rigging issues. GPS plotter showed me 15 miles offshore. Turned inshore and motored for 2 hours but no land on the overcast horizon. Weird, so I got out the back up GPS which only gave lat/long position. We weren't 15 miles offshore but more like 50 miles. DR'd into Monterey from the back up GPS position. The original GPS plotter was locked on a position just off Monterey.

Bought a new GPS plotter in Monterey and finished the delivery without incident. When I got to Oceanside fired up the old Plotter and it was once again functioning properly. No idea why it had gone whacko off Monterey.

We did SoPac prior to GPS. Keeping a running DR and the sextant got us everywhere but it was time consuming and not all that accurate. Definitely not accurate enough to sail onto a shore in fog or limited visibility. The sextant wouldn't have been useful at all in the above situation because of overcast. Navigating with the Magenta line of the GPS has made me a bit lazy. Kind of taught me a lesson on the need to keep a DR plot going.

This confirms that good seamanship would dictate backup units in case main unit fails.
I cary my little Etrex20 everywhere i go.
DR on charts is still very important en relevant.

[roland stockham]

Yes I have direct experience of GPS (and other electronic nav) failure. I fact when I started there was no GPS. There was a system called Decca that used land based nav beacons but half the time it was so inaccurate it was next to useless. I have had total electronics failure after a very rough Atlantic crossing when water got into primary and backup devices and took them all down so we had no charts!! We had also been forced 600miles off course, hence no large scale paper charts. Fortunately I also had a Garmin GPS that is as near bomb proof as it comes so we did have a GPS position (and a chart of the windward islands). We also used the SSB to get some GPS way points.

Second hand I have also met people who have lost all electronics due to lightening. A close strike will do it, you don't have to get hit.

Lessons? Multiple redundancy of critical systems is a good idea on long trips or where there are special hazards such as lightening. Non marine devices such as laptops need water tight cases, in prolonged bad weather the level of moisture even below decks can destroy them. Never totally rely on electrical stuff, it is the most vulnerable system on the boat. How may people have any redundancy in the battery/charging system, do you have a spare house bank? How long would you backup nav system run from its own batteries? (actually these days a tablet with a power pack can be surprisingly good).

Getting out of trouble. Pre GPS I had a trip across the N Sea in very nasty sea and a dead head wind. When I came on deck I found the skipper had spent several hours of a very seasick night as he said "sailing by the wind" no courses logged and he did not have a clue where we where. Solution? We noted a large stretch of coast with no off Laying dangers to the south and set a course at right angles to it. At about 200m off where where able to fix a position from the name on the fish & chip shop... Navigation remains a creative art!
The main issue is I think not whether to carry a sextant but if, in these days of electronic everything, you have enough experience to cope if it fails. Try turning it all off for a day and see how you do? Then do that regularly as training, maybe include MOB and fire drills. It will make you a better and safer sailor.
I do carry a sextant. Never needed to use it seriously for nav, yet! but they are fun to play with and one day I may be very glad of it.

[Flagman101]

Originally Posted by Adelie

C
My thoughts on best practices here is to get a metal ammo box ($30 for 2 @ Costco). Keep the mechanical watch & 5 cheap waterproof quartz watches in it.
Daily wind the mechanical watch.

You do know that the cheapest quartz watch will be more precise then your most expensive mechanical watch?
I'd rather rely on quartz then mechanical watches.

And I do own a nice Citizen Skyhawk eco drive that is radio controlled.
I have owned it for 9 years now and it never needs batteries as it's solar powered and always very precise because overnight it tunes to an antenna and just accordingly. I have never had to just time on it.
I think it would probably get the signal very very far from shore. I live in Montreal Canada and the nearest antenna is in Denver Colorado. There is on in Japan and one in Europe.
IT's titanium and 200mt water resistant.

[stewie]

I posted this a little while ago and someone took it down. I wonder why.


In 82 we made our first Atlantic crossing and our satnav antenna amplifier was taken out by lightening a few day south of the Canaries. Fortunately we had bought a Davis plastic sextant and navigation tables before departing from Gibraltar. True our fixes on a small yacht we a bit zig zaggy on the way over but we picked up Barbados MW radio station a couple of hundred miles offshore with a transistor radio and homed in on the direction of the null. I have heard that trainee merchant officers are once again learning how to use a sextant as part of their training as the sun never fails. On the next crossing we had bought a good sextant.....

[Flagman101]

Originally Posted by stewie

I posted this a little while ago and someone took it down. I wonder why.


In 82 we made our first Atlantic crossing and our satnav antenna amplifier was taken out by lightening a few day south of the Canaries. Fortunately we had bought a Davis plastic sextant and navigation tables before departing from Gibraltar. True our fixes on a small yacht we a bit zig zaggy on the way over but we picked up Barbados MW radio station a couple of hundred miles offshore with a transistor radio and homed in on the direction of the null. I have heard that trainee merchant officers are once again learning how to use a sextant as part of their training as the sun never fails. On the next crossing we had bought a good sextant.....

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[boatman61]

Always carry my ocean boat charts so never worry overmuch about gps dying on me.. DR has served fairly well in the past from 1000nm out and if in doubt wave down a fishing boat to check..

[Dockhead]

Originally Posted by Adelie

If you want I’ll post to the NavList. That’s the CelNav folks.

Sure; thanks.

[Cu Mor Glas]

Originally Posted by tmccaffery

You can also take bearings using horizontal sextant angles between two landmarks. With three landmarks you have two lines of position to make a fix.

This is my point. gps and dead reckoning for the long passages no matter. this is the most useful thing a sextant can do for most people. not everybody makes transoceanic passages, but pretty much everyone has to do coastal piloting. a three arm protractor, a paper chart and a sextant tipped on it's side are SUPER easy to use and give you very good LOPs fast. and you don't have to do math on a boat tossing you around in a cross swell.

[captmikem]

Originally Posted by roland stockham

I do carry a sextant. Never needed to use it seriously for nav, yet! but they are fun to play with and one day I may be very glad of it.

It appears many people believe one can just unbox a sextant and get a position.

That is possible for a noon site, which will only give you latitude, not a position.

Dutton says one needs at least 1000 sights before one can count on accuracy.

I have taken thousands of sights, literally. I was second officer on a RO/RO and probably took 100 a day. (I always take 3 sights of a body and average the time and sight to reduce errors). I haven't taken a sight in over two years, and if I needed to, would be rusty and it would take time to work one out, and double check for errors. which would not give me a position, but an LOP. Now if I were doing a round of stars, I could shoot them all in about 10 minutes or so, (If I happened to have 249 "Selected Stars) aboard, but it would probably take me a good while to work them out. I can not imagine someone who has not been proficient with a sextant getting anywhere near their position with a sextant. It is just not a skill one learns in an hour, or two hours.

If you happened to have say.. Mary Blewitt's or another book aboard as a refresher, along with the tables, an almanac, and accurate time. and you knew and had practiced the basics of taking and working out a sight, then you could (on a sunny day) theoretically fix your position probably within a day or maybe a 12 hours if you were lucky.

Folks nowadays do not know how lucky they are to have an accurate fix whenever they demand it. Having a sextant aboard is of little use unless one has the skills, knowledge and associated texts, along with accurate time, to use it.

M

[Dockhead]

Originally Posted by roland stockham

. . . . At about 200m off where where able to fix a position from the name on the fish & chip shop... Navigation remains a creative art! . . ..

Classical pilotage!

As Boatie mentioned, once you see any traffic, you can also ask for a position by radio, if you have a working radio.

[ZULU40]

Originally Posted by Flagman101

Hello, last week-end I got unwillingly into a thorny discussion with an other boater about Sextant and GPS.

So anyways this post is not to argue the necessity or not of knowing how to use a Sextant.

What I'm looking for is actual accounts of sailors, getting lost or in trouble because they're GPSs broke down and did not know how to navigate without a sextant.
Actual bleue water sailors.
I have never heard a single story about that.

you dont have to know much

As long as you can approximate your latitude and can determine local noon, that is the highest acent of the sun, and you have a chrono that is accurate to the second, that time will give you your longitude

I would suggest if you are very inexperienced, leave the sextant to do just that. Dead reckoning will give you a fair approximation of your position, in this case noon sights are an assistance to dead reckoning.

No you wont be able to approach hazards at night or in fog, but it will help you make a position determination that would keep you out of trouble. If you approach coasts in daytime, and have used a healthy dose of either easting or westing, most likely you can work out where you are from there with some safety.

So why use easting or westing and what is it?
You make a deliberate plan to approach your destination with the certainty that you will arrive to one side of it. In this way once you have made your distance, you only have to turn one way and be on the way to your target.

Plan B? Put the batteries in your back up GPS

[sailorboy1]

I’ve been on a boat that lost all electrical navigation and got lost. It then took a star position fix and headed North at max speed. 6 hours later it was discovered that the boat was really heading South.

This was about 1984 and I was on a US Navy Nuclear Submarine. If the same events happened today the boat wouldn’t have gone the wrong direction. But if it happened exactly the same AND the boat didn’t get the electronics back up it would and they it would have continued till maybe someone questioned why the Sun was in the wrong place (through a periscope)

[Siberian Sea]

In truth I believe many if not most of these sailors are indeed lost. Let’s just face the facts....... the GPS system has allowed way to many incompetent people to buy a boat and with little or no navigational skills at all just look at a laptop screen and watch the marker move across the digital chart. Backup paper charts?, understanding of meteorology?, even the proper calibration check (swing) the compass is beyond so many. The understanding and skilled use of a sextant sadly has gone the way of real shipwrights whom could spiral a Douglas fir plank in a wonderful wooden schooner.

[Flagman101]

Originally Posted by sailorboy1

I’ve been on a boat that lost all electrical navigation and got lost. It then took a star position fix and headed North at max speed. 6 hours later it was discovered that the boat was really heading South.

This was about 1984 and I was on a US Navy Nuclear Submarine. If the same events happened today the boat wouldn’t have gone the wrong direction. But if it happened exactly the same AND the boat didn’t get the electronics back up it would and they it would have continued till maybe someone questioned why the Sun was in the wrong place (through a periscope)

Wow scary that such a weapon does not even have a simple compass.
Also confusing north from south..suprising, NW to NE maybe.
But I don't know much about nuclear subs.