Sailing retro low tech - legal risk?

[dunedin]

is it that more recent plotters have better inbuilt fluxgate compasses perhaps? I know from sat nav on my phone you don't get a good indication of the direction you're looking until you've move a bit from one point to another, the faster the better.

But still why do something with a complicated piece of electrical equipment when you can do it with something simple that can't run out of power. That said magnetic compasses can be messed up with something placed near it so its not infallible.

But who said that the chart plotter is a replacement for a compass heading? You have invented that. Most people use a mix of inputs - eyeball, compass, plotter. And in some situations Radar and/or AIS.
Incidentally I do a lot of navigating aided by plotter and/or iPad at very slow speeds, 2kts or less, going into rocky channels. Using very detailed Antares charts on the iPad, I have noticed it detects when I swap between the two steering wheels, about 2m apart.

 

[geem]

You raise a good point. Relying on a depth guage for depth is arguably more of a concern than other electronics. At least a lead line could be used at the bow ?

We regularly calibrate and check our depth guage with a traditional lead line. It amazes me how often I have to recalibrate it.
The depth guage is pretty useless anyway when navigating reefs as often they are simply a coral wall. You would have hit it before the depth guage even registers the change in depth

 

[dunedin]

Hmmmmm, to turn it all upside down. This week I took friends on a Prep week for Day Skipper course, to convince the wife she knew enough (had the theory and mileage / understanding) and shouldn't waste money on comp crew.

She completed a 4 mile upriver night pilotage into port using her 'plan' and the flashing red and green lights.

In the morning, Hubby brought us down in daylight using Mk 1 eyeball - all was well. However, the plotter showed us going straight through a port hand mark.

Had we sailed on the plotter we would have gone aground out of the channel, so question to electronic devotees - would we have been negligent and prosecuted following the chart plotter???

As ever, it depends, and where sailing is a key factor. But even then there could be more than one reason:
* if in English SE coast entering a winding channel in the sand, one would expect buoys to be moved regularly depending on storms and channel shifting - so would not be relying on any chart (perhaps other than a very recent local survey known to remain current)
* in some remote cruising grounds charts are known to be regularly well out of alignment, perhaps a mile in some cases - so would also be looking at satellite images and similar to aid navigation
* in all waters, buoys will move position slightly based upon height of tide etc, and may even be pushed onto the shore at low tide. And in some waters, eg after ice melt, buoys may have broken free or moved substantially
* whilst less of an issue recently, differences in chart datum can create a shift - either an error on the ships chart datum, or an error with the chart production
But without knowing the location and circumstances, it is just as likely that the buoy was off station as the chart being off location. Hence using multiple sources, including depths.

 

[lustyd]

We regularly calibrate and check our depth guage with a traditional lead line

I'm presently unable to calibrate my depth due to mixing old Raymarine with new B&G. This will be fixed at next lift out when I swap out the transducer. As a diver though, I figure anything within a metre is good enough, even small rocks can be half a metre high. Precision is often misleading with electronics. The display can show you depth to 0.1m or 10cm but that's the height of a bean tin on the bottom!

 

[MisterBaxter]

The late Phil Bolger designed a boat called Ataraxia, which was meant to have as much reliability and ease if maintenance as possible designed in from the start. The boat was to have 'the most modern electronic navigation equipment, backed up by leadline, compass and Walker log'. That's the approach I like - if you put your position on a paper chart from time to time and have non-electronic equipment on hand, even a total power failure is only a minor inconvenience.

 

[srm]

We regularly calibrate and check our depth guage with a traditional lead line. It amazes me how often I have to recalibrate it.

Speed of sound in water varies with salinity, temperature, and density (though the latter is also partly a function of the first two). During survey work its standard procedure to calibrate the echosounder at the start of a day's sounding and check the calibration at the end of the day.

 

[TSB240]

But who said that the chart plotter is a replacement for a compass heading? You have invented that. Most people use a mix of inputs - eyeball, compass, plotter. And in some situations Radar and/or AIS.
Incidentally I do a lot of navigating aided by plotter and/or iPad at very slow speeds, 2kts or less, going into rocky channels. Using very detailed Antares charts on the iPad, I have noticed it detects when I swap between the two steering wheels, about 2m apart.

Do you do your rock dodging in zero visibility? Probably not.

My experience of just relying on a charplotter was coming out of Kilmore Quay. It was very very foggy and we had no reference from shore. lights, moon or wind.soon after leaving.
We were called by a large fishing boat who had seen our ais and asked to hold station just North of the entrance in shallow water.
You have to have a compass and or radar image of land to give you a guide as to which direction to set off.
A gps will take quite a few seconds even at a reasonable speed before they actual report and update on your COG. They default to North irrespective of which way your boat or chartplotter or tablet is pointing if you are static or near static.

Try setting your chartplotter to course up and you will see the effect at slow speeds.

I survived with the back up of a reliable compass heading and estimation of tidal drift until my wife announced that my track on the chartplotter was dead on the lay line out to the gap in Paddy's Causeway without reference to the chartplotter!

 

[geem]

I'm presently unable to calibrate my depth due to mixing old Raymarine with new B&G. This will be fixed at next lift out when I swap out the transducer. As a diver though, I figure anything within a metre is good enough, even small rocks can be half a metre high. Precision is often misleading with electronics. The display can show you depth to 0.1m or 10cm but that's the height of a bean tin on the bottom!

I always leave a 1ft extra. Not such an issue with a lead keel on a battleship?
And we can normally see through the water if it's shallow

 

[dunedin]

Do you do your rock dodging in zero visibility? Probably not.
…………
A gps will take quite a few seconds even at a reasonable speed before they actual report and update on your COG.
……..

That’s precisely why I said most people use a compass as well as a plotter. Heading is clearly not the same as COG.
Try crossing the edge of Corryvreckan in 100m visibility, as we have done. Yes need to know heading as boat is caught in tide spirals going sideways at speeds varying from nil up to 9kts.
Certainly would not have been happy doing even the short and familiar journey from NE tip of Jura to Crinan without all of plotter, compass and radar. Paper chart navigation impossible as unable to predict ground track due to huge variability of tide swirls - at times Heading and COG 70 degrees out, then suddenly almost align again..

 

[Adios]

That’s precisely why I said most people use a compass as well as a plotter. Heading is clearly not the same as COG.

So don't any plotters have an internal electronic compass? Heading is always just COG with GPS? When they have so much integrated tech i'm surprised.

 

[lustyd]

So don't any plotters have an internal electronic compass? Heading is always just COG with GPS? When they have so much integrated tech i'm surprised.

Why are you requiring it to be internal? Seems to me like creating rules to prove your viewpoint. Does your paper chart have an internal compass in the rose?

 

[lustyd]

Try setting your chartplotter to course up and you will see the effect at slow speeds.

Or how about try setting up modern electronics properly with a 9 axis compass and using the heading rather than the COG to steer. Even in my berth in the marina the heading is absolutely stable and updates faster than the ship compass if I set it to do so because it's not floating in liquid waiting to spin. I don't have it set like that because it's useless at sea, so some damping is added to make it stable like the old stick in a jar compass design. Stick in a jar wasn't the first design either...

 

[TSB240]

So don't any plotters have an internal electronic compass? Heading is always just COG with GPS? When they have so much integrated tech i'm surprised.

Majority of GPS Chartplotters use speed and doppler effect to caculate heading . Totally useless without the addition of a magnetic heading compass digital or analogue at slow speeds.
Just get your tablet or phone out and see If you can get a stable heading out of it without walking briskly.

 

[Chiara’s slave]

You raise a good point. Relying on a depth guage for depth is arguably more of a concern than other electronics. At least a lead line could be used at the bow ?

My sounder is aft of 5he centreboard. Fortunately that has a trip mechanism. My sounder is more use as a confirmation of the plotter accuracy though. You can get out and push in our boat if it’s too shallow to sail.

 

[Buck Turgidson]

Majority of GPS Chartplotters use speed and doppler effect to caculate heading . Totally useless without the addition of a magnetic heading compass digital or analogue at slow speeds.
Just get your tablet or phone out and see If you can get a stable heading out of it without walking briskly.

a) You are confusing two different things. COG and Heading.
b) My phone has magnetic flux sensor and has a compass app to display it. I don't need to move for it to be perfectly accurate.

 

[zoidberg]

"Lead, log and lookout, son. That's all you need. It was good enough for your grandfather. It's good enough for you......"

 

[capnsensible]

"Lead, log and lookout, son. That's all you need. It was good enough for your grandfather. It's good enough for you......"

Indeed. But some computer nerks enjoy faffing around with electrons. And why not? I'm all for that. As long as its realised that there are others that don't!

 

[Chiara’s slave]

Indeed. But some computer nerks enjoy faffing around with electrons. And why not? I'm all for that. As long as its realised that there are others that don't!

Do you think mariners of old had similar conversations in waterside taverns about compasses, chronometers, sextants and the like? Some of them doubtless thought that a lead line and the taste of the sea bottom was all they would ever need.

 

[capnsensible]

Do you think mariners of old had similar conversations in waterside taverns about compasses, chronometers, sextants and the like? Some of them doubtless thought that a lead line and the taste of the sea bottom was all they would ever need.

I reckon that with the high attrition of sailors and ships, the sextant, chronometer and lime juice was met with relief by most. Pushed on by owners wanting their cargos to be safe.

However I'm sure that for ever, sailors have moaned about the weather, the competence of the command, the disrespect of youth and the spiraling costs of women and grog.

 

[Chiara’s slave]

For sure we don’t have such an attrition rate. But whilst I can, and have, pre GPS, navigated the English channel, for me, finding and accurately avoiding the outlying hazards of Beaucette marina is a damn sight less nerve wracking with every aid at my disposal. When I am safely moored, I will, for sure, start moaning about the weather, the disrespect of youth and the cost of women and grog. Being the skipper, I don’t tend to moan about my own inadequacies.