Hōkūleʻa Update | Navigation Basics – Part 2
Aloha nui kākou,
Prior to leaving the Galapagos, our navigation team worked with Nainoa and our Captain Uncle Archie to develop a sail plan and a course line that we would reference to keep track of our direction and distance traveled as we sail to Rapa Nui. Our reference course started at Isla Espanola and takes us on the southwesterly course of Nalani Kona (213°, or 33.75° west of south), which leads to a point 90 miles east of Rapa Nui. Then, at Rapa Nuiʻs latitude (27° south), we will make a right turn and sail Komohana (west) towards the island. The primary job of the navigator is to keep a running tally of how many miles east or west the waʻa is of our reference course; this daily total is calculated based on what we have determined about speed, direction, winds, swells, etc. The winds slowly transition from light southerly or variable doldrum conditions near the Galapagos, to a more southeasterly or tradewind flow further south. Every day, we have been sending in our navigation update with this information, for those who are following our navigation route.
We are concerned that if we are not precise with our steering that we may fall west of our reference course, and miss our remote target. Because of this, we have spent the past four days sailing slightly east of our reference line to account for drift and current, and to give us an additional 150 mile buffer – buying us an extra day on our westerly, downhill run as we search for the island.
The way in which we account for how much east or west we have sailed over the course of a day in relation to our reference line is by using a deviation table. Nainoa constructed this deviation table to assist him during the 1980 sail, when he successfully navigated round trip from Hawaiʻi to Tahiti and back. The deviation table is derived off of the average sailing day, where the canoe travels 120 nautical miles in a day at 5 knots.
We memorize this table to know just how far east or west of our reference course we have traveled for every star compass house that we deviate from our reference course. For example, if our reference course is Nālani Kona but we actually travel Nā Leo Kona (one house east of Nālani), then over the course of one day we would be 24 miles east of our reference course. Expanding on this 5 knots table, we also calculated deviation tables for varying speeds to keep a more accurate account of our variance between 2 and 10 knots.
Over the last few days, we have broken up into two navigation teams and taken 24 hour shifts. Our job while on the watch is to trim the canoe’s sails and adjust weight so that we sail a straight course without the use of the hoe (steering paddle). We are using the sun, swell and wind in the daytime, and the stars at night when they are available. The large moon has been both a blessing and a challenge as it dims the light of faint stars.
This morning our navigation team determined that we are about 949 nautical miles south of our starting point and 303 east of the Nālani Kona reference line. Our estimated latitude is about 17 degrees south – in our next navigation basics blog, we will discuss how we can use stars to help determine our latitude.
Stay tuned, and don’t forget to check out hokulea.com for all the latest info on our voyage.
Haunani and Jason
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