Navigation redundancy???

[fractalphreak]

We have a mix of redundancies, most a work in progress. The two most important, position and depth are complete and almost complete, respectively.

We carry guidebooks and digital copies of the coast pilot. We also carry a mix of paper charts and chart books, but thus far only have our local Washington waters, little in BC or AK - part of our intended long term cruising waters, yet. We have a southern BC trip in July so some are coming soon! I keep the chart book out and open to our current position when we're out, we have a nice big chart table as our dash next to the main help position, its something I've always done, and used to help show the Admiral and the kids where we are and where we are going (and to keep it straight in my head too.) I actually find its easier to look at for overall reference than the plotters sometimes - I don't have a plotter that big! The first thing we do when we think we're going to a place is review available guidebook info on it. Then the charts.

The trawler came with two Garmin 12" MFD's, each with its own independent electronic charts and GPS antennas. Then we added the AIS system and the NEMO onto the NMEA, so we have a third GPS source but only a single point AIS. That brings me to position source #3, the laptop. None of them will work if we have total electrical failure. The lower helm compass is professionally swung since the major electrical install (the inverter installed about three feet below) so in the event of no power to electronics its charts and flashlights and compass. .

For depth I am very short on redundancy right now. We have the Garmin sounder module that feeds both Garmins on their network and the NMEA network (to the Nemo and the laptop.) I have my homemade leadline - a 1 lb blue dive weight with a hook and a line with knots every foot out to 10 ft, then knots at 15 and 20. I think its 25 or so feet long, intended for the shallows only. I have a non-NEMA inside the hull sounder/depth digital depth gauge that I intend to install at the upper helm (if it will reach, not sure yet) to measure depth at the stern for anchoring in bays. Doesn't do any good until its installed and working though.

We're a work in progress!

 

[rgano]

An RDF and a Handheld VHF radio, both small battery operated. Both in/near a lifeboat. That is redundant.

Please explain how you would employ an RDF in a lifeboat. I am intrigued.

 

[diver dave]

Please explain how you would employ an RDF in a lifeboat. I am intrigued.

I would have the oarsmen make way to the strongest signal, lacking any other nav aids.
There is an interesting read on a lifeboat crossing the atlantic after a whale took out his sailboat keel. He used basically a protractor to determine his coarse latitude using polaris. He adjusted his sailing course to hit the leeward islands as i recall.

 

[rgano]

I have recently read two books detailing the escape of US military persons from Corrigedor/Bataan one by sail and another by 36-foot motorboat 3,000 miles to Australia with little more than a page of National Geographic showing the entire South Pacific Ocean. One had a homemade sextant to take horizontal bearings on island headlands.

 

[ksanders]

How about an old fashioned $80 Humminbird digital depth sounder, can also be run off a small battery. In an emergency in shallow water then having a weighted rope with knots every few feet is a great idea. Costs zero dollars.

It's been mentioned lightening possibly taking down the entire electrical system. Small chances??? When I was younger I lived/sailed on Tampa Bay. Lightening hit nearby and we got zapped in our boat just from the charge in the water. I was even hit by a waterspout once.

For local cruising this isn't a big concern really, but for remote passage making it's another story, and having backups of everything electronic, down to the "circuit breaker level" is not full redundancy.

Thank you! That is actual redundancy!