What would you do if...

[Babylon]

mid-ocean an event of some description caused you to lose all use of GPS, sextant and comms? Assume you still have your almanac, tables, main passage chart and a watch or clock of some description.

An academic question perhaps, and from someone who's far from being an ocean sailor let alone a participant, but I'd be interested to hear the responses.

 

[Slothinabox]

How you lost electronics and the sextant at the same tie would make a good story, The lightning strike gave you such a start you threw the thing over the side?

If you still had a compass and a mechanical log, then your dead reckoning position would get you to landfall. If you managed to keep hold of the sextant but lost your clock, you can still do a noon sight to get a position.

Not sure how you would cope if you only had an electronic log, if you knew the boat well enough that you could give approximate boat speeds for certain conditions, it would be a start, if sketchy.

A knotted rope for speed perhaps?

 

[Gitane]

For speed, their are two options I can thing of:-

1) throw a fender and some kind of drogue tied to the boat from the bow and time how long it takes to travel to the stern. Knowing the boat length, the speed can be calculated. Not very accurate, especially when going fast or in rough weather.

2) Tie fender with drogue to the longest line on board and throw fender overboard. Time how long it takes for the fender to travel away from boat until the line goes taught. Knowing the length of the line, the speed can be calculated. Still not very accurate, but better than 1 above.

For latitude, a star chart can be used to find stars directly overhead. If the star can be identified, then latitude would equate to latitude of star. Again, not very accurate, but better than nothing.

If you have access to trig tables, then a marked stick and a piece of line about arm's length, one end of which is held in the mouth the other end tied to the stick, can be used to make a very rudimentary angle measuring device. It is then a question of waiting for the sun to reach its zenith and judging the angle from the stick and using the sun's declination to work out the latitude. For longitude, the clock's time halfway between the times the sun passed the same angle each side of noon to get local noon and the equation of time could be used to get a rough idea longitude. Very good sunglasses, possibly with the lens darkened further using a flame and a cork, will need to be used to prevent sun blindness. If the clock is not set to Greenwich time, then this is not a problem as this technique can be used to measure distance east/ west from last known position assuming that the clock's time has not been adjusted since then, which would also give a rough indication of longitude.



Jack Lagan's book The Barefoot Navigator covers these and other techniques very well.

Emergency Navigation by David Burch includes a section on navigation with crucial pieces of equipment missing, similar to what's described.

Gitane

 

[CarlBarnett]

Is there any other way to do that?

 

[Poignard]

I suppose I would try and do what navigators did before any means of determining longitude existed; ie, get on the desired latitude and stay on it until I arrived near the desired landfall, by dead reckoning. Then I'd keep a good lookout (maybe heaving to at night).

I could make up some kind of protractor to measure the sun's elevation at noon each day.

The thing is, if it was mid-ocean I'd have plenty of time to think of a solution, and plenty of incentive to think hard!

 

[PacketRat]

Fun question. I'm with gitane and parsifal on this one - clock, string and stick, noon sights and times.

Also on the approach: sea temperature changes due to the Gulf Stream, and the appearance of coastal sea birds.

My big real life experience with GPS failure occurred when (boldly) deciding to approach Caernarvon Bar for the first time, and at night, on the way back from Baltimore earlier this year. I was pretty knackered and really fancied the idea of being tied to a pontoon. Everything went nuts. I couldn't make any headway to the buoy I'd identified at the entrance. The tides were dragging me one way then another. Then I was getting swept up over the bar and sandbanks, up the channel and frighteningly close to some enormous girder structure not shown on the chart. Instead of being able to rely on the GPS to keep me on track, it was miles out. My backup GPS was similarly affected so I realised the unthinkable had happened and the satellites had gone wrong. The weather was great, so I let out my anchor at full scope.
Well, the anchor never touched bottom. When eventually I discovered that the buoy I was aiming for had the same light characteristics as a lighthouse miles up the coast, I took a couple of bearings. I wasn't half way up the beach, I was, indeed, miles offshore. I'd made a right idiot of myself.

I may or may not make it to JC14, but from the comfort of my armchair I can imagine how well I'd cope with the scenario you pose. It'll be a doddle.

 

[helixkimara]

Re Pete Goss sailing to America and not getting the hang of celestial navigation from a book. " Head West,(You know, where the sun sets) when close to land ask a fishing boat where you are."
Mal

 

[alant]

I suppose I would try and do what navigators did before any means of determining longitude existed; ie, get on the desired latitude and stay on it until I arrived near the desired landfall, by dead reckoning. Then I'd keep a good lookout (maybe heaving to at night).

I could make up some kind of protractor to measure the sun's elevation at noon each day.

The thing is, if it was mid-ocean I'd have plenty of time to think of a solution, and plenty of incentive to think hard!

Not sure what "dead reckoning" has to do with it, unless you want to be awake, when you 'hit' land.

 

[theguerns]

Find the time of sunrise on a latitude which is the same as any land mass. then sail along said line till you reach the land mass. Sailors have been using this system for many years

 

[rptb1]

(I'm writing this before I read the rest of the thread, to compare my answers!)

mid-ocean an event of some description caused you to lose all use of GPS, sextant and comms? Assume you still have your almanac, tables, main passage chart and a watch or clock of some description.

Make a sextant. Steve Callahan made a sextant out of pencils, elastic bands, and a protractor in his liferaft. This is described in his book “Adrift”. A Portland plotter has a protractor, but even without it's probably possible to get some reasonable graduations by bisecting.

Or use the pumb-bob technique (when a star is directly overhead you're on its latitude). Alberto Torroba used this technique without even a compass.

I also recommend looking up Marvin Creamer who circumnavigated without any instruments, not even a compass or clock. There's an excellent two-part interview with him on the Furled Sails podcast http://furledsails.com/article.php3?article=774 He used multiple techniques to confirm each other, including the plumb-bob method by eye.

 

[SteveSarabande]

Head west till you meet a fisherman, ask him where you are. Assuming your in the atlantic

 

[elton]

Quite simple: I would starve to death, drown, or die of exposure.

 

[Porthandbuoy]

Have a look at the sky and watch for aircraft contrails. Whatever ocean you're on (except perhaps the frozen Arctic) they will be heading to or from somewhere you should be able to identify on a chart or even an atlas. When they start to lose altitude you know you're a couple of hundred miles from their destination, not necessarily land.

IIRC someone sailed from San Francisco to Hawaii using just this method.

 

[ghostlymoron]

Assuming you had noted your position recently, you would have to continue with dead reckoning. You don't say if your charts have also been destroyed so I'm assuming they haven't. If they had, you'd have to continue on your 'most likely to reach land' course until land was sighted, possibly heaving to at night although I've noticed that you can usually detect land from far off by the presence of clouds etc. If you were lucky enough to get within contacting distance of another vessel, you could attract their attention by firing a cannon, setting fire to a tar barrel or one of the other methods (flags?) and enquire as to your position.

Edit - just noticed you still have your passage chart so some of above irrelevant.

mid-ocean an event of some description caused you to lose all use of GPS, sextant and comms? Assume you still have your almanac, tables, main passage chart and a watch or clock of some description.

An academic question perhaps, and from someone who's far from being an ocean sailor let alone a participant, but I'd be interested to hear the responses.