Tuesday, May 10, 2016

Moonshadow on Passage (again)

Goodbye Marquesas!

Today, Moonshadow began what will be a passage of exactly three days. And this is a passage with a unique challenge for her crew: Keep the speed down! That's because our goal is not just a daylight arrival, but an arrival at the pass on the island of Kauehi at slack tide.

Kauehi is one of 78 islands in the Tuamotu group of French Polynesia, all of them are atolls. They're called that because you can't see them at all. These islands are nothing more than a ring of coral with a lagoon in the middle. Usually there are sand islands on the coral, but they seldom extend all the way round the atoll, so there are patches which are just at or below the surface, virtually impossible to see. Many, many ships and yachts have found their way onto these coral reefs, including a boat named Morning Dove, which was among the group of boats that sailed here from Mexico with Moonshadow. Her crew was rescued by helicopter from Papeete, but the boat may be a total loss.

Some of the atolls have a break in the coral ring called a pass, which provides entrance to the lagoon within. The passes are notorious for having very strong currents because, although the tide only rises and falls a few feet in this part of the world, all of the water in the lagoon must flow through the pass. Currents can be in excess of 6 knots, and make standing waves, small whirl pools and look really scary. Well that's what we're reading, anyway. So the strategy is to arrive exactly at the time for "slack tide", a period as short as a half hour when the current is minimal, so safe navigation through the pass is possible. Some islands, like Kauehi have wide deep passes, and some are narrow and shallow, even twisty, making them "tricky". We'll take on Kauehi first and see how we go.

But there are two critical parts of this passage that we need to pull off: We will have to slow Moonshadow down so we don't arrive before daylight, and then arrive at the pass on the southwest side of the island a bit before slack tide (10:30 AM local) so we can wait for the perfect opportunity to navigate through and into the lagoon. Then, the only challenge will be avoiding the bommies. Bommies are coral heads that reach up to the surface or just below. They are most visible with the sun overhead and behind. This is why we put steps up the mast to the first spreader where one of us will perch as lookout.

The wind and sea conditions are perfect. In fact, too good. Moonshadow is sailing at 8-9 knots which is great, but that speed will bring us to the atolls before daylight on Friday morning. That's Friday the thirteenth by the way. So at some point we'll need to throttle Moonshadow back a bit, but not now, this is too fun.

At 0330 zulu (5:30 PM local time)
10 degrees, 3.6 min South
140 degrees, 41.6 minutes West

Distance travelled 55 miles
Distance to go 449 miles

All is well aboard Moonshadow

Cheers,

John and Deb Rogers
SV Moonshadow
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3 comments:

Aidan Barrett said...

Hi Guys
Great excitement - very best wishes entering those atolls. We will be thinking of you both and look forward to the next blog confirming that all went well. You have a great boat a great skipper and crew so I feel confident that all will go well for you.
Continued bon voyage.
Aidan and Robin

Robert Gentry said...

ummmm, super challenging, reefs, currents, hidden bommies and Friday the 13th....now all you need is a black cat! High risk means high adventure. Safe passage and enjoy!
Bob

Cindy said...

Be safe, have fun and give 'er... or not depending on all you stated! That sailing isn't for the faint of heart. I want to get an update pronto when you are enjoying a drink with an umbrella in it!! xoxox

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