GPS failed while we were out in the big deep blue enroute to Tuamotus

2008-06-08 to 10  Sunday through Wednesday

Manihi Atoll, Tuamotus, French Polynesia

14.27.88S; 146.02.13W      Distance sailed 497 NM

It was a wild ride! 

We left Tahuata in the Marquesas at 0800 Sunday morning and arrived at Manihi Atoll in the Tuamotus at 0800 Wednesday morning.  That means we covered 497 nautical miles in 72 hours and sailed the entire way. Didn’t need the engine until it was time to enter Manihi.  Winds had been 20-25 knots for a full week before we left the Marquesas, so the seas were built pretty high and steep.  Winds were predicted to continue at 20-25 knots for Sunday, 20 knots on Monday and then moderate to 15 knots on Tuesday.  Winds and waves should have been on our port stern quarter so we figured we could handle it from that direction.  Unfortunately, the actuality was somewhat different than the prediction.  Winds stayed 20-35 knots until early Wednesday morning, when it finally gradually moderated down to about 18 knots.  Seas were 3 to 4 meters on 4 to 5 seconds– and those are really big waves when stacked so closely one upon another.   We have an inclinometer mounted at the helm and it indicated that we were heeled over at 45 degrees many times!  We have never heeled 45 degrees before!  Makes one really appreciate that 6500 pounds of cast iron keel bolted on the bottom of the boat so that the boat always turns back upright.  It was impossible to move around on or inside the boat unless we were holding on with both hands.  

The Tuamotus are a large group of atolls and comprise the middle section of French Polynesia.  Let me try to explain what an atoll is.  Imagine a volcano forming a mountainous island.  Then coral reef forms around the edges of the island.  Then the island sinks back into the ocean, leaving the coral reef encircling a large lagoon.  Over eons sand gradually fills some spots in the coral reef circle and forms scattered small islands around the lagoon.  That is an atoll.  Most atolls have a single pass through the reef which allows access in and out of the lagoon.  Current caused by tidal change often reaches up to 9 knots flowing in or out of these passes, so it is critical that one negotiates the pass during slack tide. 

Manihi Atoll has a lagoon that is 15 miles long and 6 miles wide.  There are at least a dozen tiny islands fringing the lagoon.  The lagoon is deep (we passed in areas of 132 feet depth on our way from the entrance/exit pass to the anchorage area), but it is also filled with coral heads.  Water can be 80 feet and then be 2 inches deep.  Luckily the water is clear and that makes it easy to find your way around the coral heads.  Manihi is famous for black pearl farming.  There are black pearl farming stations all over the lagoon and it really looks funny to see these houses built up on sticks (like beach houses in Bolivar but right out in the middle of the water).  There are also small floating balls marking where pearl strings are placed throughout the lagoon. 

As we began our entry through the coral reef encircling Manihi Atoll this morning so that we could reach the pass between 2 of the tiny islands, the wind suddenly jumped to 33 knots --- right on our beam!  This was somewhat nerve wracking to say the least.  We could not see the reef line because it started to rain and the high wind was blowing us toward crashing waves.  Thanks to our 100 hp Yanmar engine I was able to drive through the reef and through the pass without incident.  There is a shallow coral bar that one must pass over just inside the pass.  Our depth gauge indicated only 3.2 feet of water beneath our keel as we entered the lagoon.  Thank goodness we entered at slack high tide.  The depth quickly dropped to 80 feet and we managed to cross the lagoon without taking out any of the black pearl strings or stations or hitting any coral heads.

However, when we attempted to anchor in the 33 knots of wind we ran into problems.  The anchor chain somehow got wrapped around at least 2 coral heads which we could not see in the 60-foot depth where we had to anchor.  It was a challenge getting the anchor back up but we finally did it.  We then moved a short distance away and this time managed to anchor without incident.

On day 2 of our passage our GPS decided to stop working.  It could not get a fix.  Now that is a bad feeling being hundreds of miles out on the ocean and not being able to tell exactly where  you are or where you are going.  We remember how to do the vector triangles that we learned when getting our captains licenses, so it would have been possible to get where we wanted to land.  But not something we wanted to deal with.  Bill pulled out our primary GPS back-up – and the darn thing would not even power on!!!  So he pulled out our second GPS back-up and we were in business.   Reminded us of last fall when we went from 3 computers down to only 1 within one week.  We just went from 3 GPS units down to only 1 within a half hour.

We finished the passage using a Garmin hand held GPS connected to our laptop and it worked just fine with Maxsea.  Good thing we had lots of batteries in stock because the hand held GPS really eats batteries.  Once we were anchored Bill investigated the problem with the primary Furuno GPS.  It appears to be just the GPS antenna is malfunctioning.   Now we need to get someone to find a replacement for us and ship it to Tahiti.  Hope we have enough batteries to keep the Garmin hand held unit operating until we reach Tahiti.