Jan. 29 and 30, 2000--Navigation Preparations; Watching the Weather

Source: Sam Low

Saturday, January 29

The ocean remains unsullied and parapets of cumulus clouds are stalled around the horizon. There is a breath, and no more than that of wind. But it is out of the north which is definetly not what we want.

The weather system over us is dominated by a ridge of high pressure containing light unstable winds. We want the ridge to move but it is blocked by a zone of low pressure which pulls the wind south toward it, creating northerlies. This morning Nainoa speaks with Bernie Kilonsky at the University of Hawai`i and learns that the low may be finally moving south which will allow the high pressure ridge to move with it. So our zone of light and variable northerlies should, over time, be replaced by easterly trades. We may see some change on Sunday and certainly by Monday. If Bernie is right, the trades should fill back in clearly by Tuesday. "Ok," says Nainoa, "we should remain on alert to go within 3 hours notice -- but if Bernie is correct we will probably not leave until Tuesday."

In the meantime, the navigators for this leg of the voyage meet to plan their strategy. Nainoa and Shantell Ching (the principal navigators) join with student navigators Kahualaulani Mick an Ka`iulani Murphy to lay out their course line to Hawai`i and discuss alternative routes depending on changeable wind and weather conditions. "You guys are going to learn a lot on this trip," Nainoa tells them. "At times there's going to be so much going on it will be like drinking out of a fire hose."

Bending over the kitchen table in Nainoa's house, they first consider the effect of the current. "The longer you're in the current the more its effect will be," Nainoa explains, reviewing basic knowledge, "so the amount of offset will depend on your speed. The slower you go -- the more the offset."

The angle that the canoe makes to the current also affects its course over the ground. Assuming the canoe's speed to be five knots, for example, with an easterly current of half a knot, a heading of Manu (NE) will produce an offset to the west of four degrees. Increasing the canoe's angle to the current increases the offfset. If she heads Nalani (NE by N) the offset is five degrees while a course to the north (Akau) means an offset of six degrees. This kind of effect can become great over long distances. Consider the passage from Rangiroa to the doldrums, about 1100 miles. At a speed of 5 knots in a half knot easterly current the effect will be to set the canoe to the west 12 miles a day or 108 miles during the nine day voyage.

Current effects like these are memorized as a set of general principles which can be easily modified mentally as conditions change. If the course is north at 5 knots and the current from the east is half a knot the westerly offset is 12 miles each day. Change the canoes speed by 50% to 2.5 knots and the daily offset will be twice as much of 24 miles. "We always try to eliminate having to do math in our heads," Nainoa explains, "it can cause serious brain damage."

For now, the navigation team concentrates on what Nainoa calls the "first stage" of the voyage home from Tahiti to just north of Rangiroa when the canoe will enter the open ocean and bgin "stage two" to the doldrums. Makatea, about 124 miles to the north, will be a stepping stone -- a echance for Shantell and her colleagues to test themselves. They consider when they should depart Tautira in order to arrive with sufficient time to explore the island.

They decide to leave at 11 am which means they will have no celestial bodies to steer by so they will have to guide the canoe by "back sighting" on Tautira's mountain peaks. Shantell figures they will be able to use the 4,500' high peak about 60 miles away on a clear day and maybe 30 on a humid day like today. "That means we can use our back sight for about 6 hours," she says, "or until 5 p.m. By 3 p.m. the sun will be low enough on the horizon to provide us good clues for steering so we can check out course to Makatea and modify it if necessary."

Once having arrived at Makatea, the next decision will be when to set out for the difficult pass between the low coral atoll of Tikehau and Rangiroa which leads out into the open ocean. Kahualaulani runs his finger over the eastern side of Tikihau's fringing reef. "These black marks are coconut trees," he says "and we should be able to see them maybe ten miles at sea -- during the day. At night, forget about it. We might be right on top of the reef before we see it."

"The distance from Makatea to Tikehau is 40 miles," says Shantell "and we want to be no closer than 10 miles at sunrise, so when should we leave?"

"If we can average five knots then we should leave about midnight," says Ka`iulani, "which should get us to a point about ten miles off the reef at about 6 a.m."

And so it goes -- the three navigators bend over their charts, discuss strategy, and make notes in their logbooks. From time to time, Nainoa joins them, asking questions and probing their readiness.

"I may be asking a lot of questions of you guys now," he says, "but at sea I'm going to back off. We'll meet at sunrise and sunset and talk about where you think you are and what course we should steer, but I will only step in if you are about to make a mistake that will jeopardize our safety."

The navigators meeting breaks up at about noon. Shantell, Kahualaulani, and Ka`iulani separate to tend to personal chores, but they will meet again at sunset to watch the stars rise over Tautira's peaks and establish their "back sight" to set direction when we depart. The rest of us wait impatiently to board the canoe and leave -- but for them the voyage has already begun.

Sunday, January 30, 2000

The weather continues largely unchanged -- hot, humid with little wind, although it was cooler last night. At 4 a.m. this morning Ota, Sabu, Papa Vaihiroa and Tepea began preparing the imu for what will probably be our last big feast in Tautira before departing. For the crews of Kamahele and Hokule`a, including new arrival Nalani Wilson, today was mainly one of rest. At one p.m., when this report was filed -- we all gathered at Sane's for a prayer prior to digging into roast pork, fish, taro, breadfruit and all the other traditional dressings and condiments associated with a Tahitian feast.