POSITION REPORT ON THURSDAY 22nd MAY 2014
POSITION REPORT ON THURSDAY 22nd MAY 2014 AT 0800
We’re now hove-to in 6 foot seas, just outside the pass into the Kauehi atoll in the Tuamotus. We’re having a nice cup of tea and should be at anchor by lunch time. Here's what we did yesterday and overnight.
21 May 2014 Daniel’s Bay to Tuamotus (Day 4)
It was a tough morning with 20-25 knot winds at 60 degrees off our port bow. We beat upwind with a heavily reefed main and just the stay sail, but at least it was sunny most of the time. The GRIB file that I downloaded showed that this wind will continue for the next 48 hours and then there'll be a patch of very squally weather for a few days, so we need to find somewhere nice and sheltered to anchor.
Kauehi is an oval shaped atoll approximately 12 miles long with a fringing reef enclosing a huge, deep lagoon. There's only one entrance through the reef, which is on the south-west side, so it should be okay to enter in these strong south-east winds. Tearavero, the main settlement, is on a small, low-lying island (called a motu) in the north- east corner of the lagoon, but only has good protection from the east, so we're planning to go to an anchorage in the south-east corner behind a few small motus where there should be good protection from the south-east.
I had another look at the tides for the entrance into the lagoon. The fringing reef around the atoll is only a maximum of a couple of metres, so the prevailing swell that crashes on the reef forces water into the lagoon. Since there's only one pass out of the reef, all this extra water flows out of the lagoon through the pass causing a significant change in the tidal flow of water - if the wind and waves are stronger, the bigger the effect.
The normal maximum tidal current in and out of the 200 metre wide pass at Kauehi is 4 knots, but since the wind will have been blowing at 20 knots from the south-east for a few days, I think that the current will be increased by one knot when it's coming out and decreased by one knot when it's going in. In addition, the time for slack water at high tide will be one hour earlier and slack water at low tide will be one hour later.
To make matters a even more complicated, I have conflicting information about the times of high and low tide - four different sources give me a total discrepancy of 90 minutes. So, my best guestimate is that the maximum current on the inflowing tide will be 3 knots and the time of the slack current at high tide will be somewhere between 10 and 12 o'clock in the morning. My brain hurts.
The three knot current is not a problem in itself because we could motor at seven knots if we needed to. However, the strong current rushing in through the narrow pass causes swirling eddies and a strong wind against the current can cause large standing waves which can be a major problem. Our master plan was to sail past Kauehi during the night and heave-to until seven in the morning, then make a slow approach to the entrance at nine o'clock and look at the actual conditions of the water going in through the pass, before committing ourselves.
After lunch, the wind abated a little and thankfully backed, so that we were on a beam reach making the afternoon very pleasant. At sunset, we only had 35 miles to go, so I put another heavy reef in the main and rolled away some of the stay sail in an attempt to slow down, but with 18-22 knots on our beam, we were still going along at 4-5 knots over the ground.
It was a nice sail for the first half of the night, if a little worrying sailing between two very low lying atolls, which have no lights. The channel between them was over eight miles wide, but it was still very unnerving to know that there were dangerous reefs only a few miles away in the pitch blackness of the night. I shudder to think how anyone managed to navigate around here before the invention of GPS.
We hove-to at around four o'clock and dawn found us two miles off the pass waiting for the tide and better light to head across the lagoon - we'll be heading directly into the sun, so it will be nigh on impossible to see any reefs until later in the morning.