Closing the Triangle

Introduction

The Challenge

Readings

Rapa Nui Settlement

Rapa Nui Prehistory

Wind, Weather, Ocean Currents of the Pacific

Sailing Strategies

Geography, History, & Culture in the Eastern Pacific

Educational Curriculum for
Rapa Nui

Letter to Educators

History & Heritage

Virtual Voyage

Introduction
I - Getting to know your Vessel
II - Sail Planning
III - Becoming a crewmember
IV - Provisioning the Vessel
V - Preparing for the Voyage

Research & Action Projects

Introduction
I - Why We Explore
II - Meterology of the Pacific
III - Naked-eye Astronomy
IV - Sealife
V - Geography, History, Culture

How to Track Hokulea

Vision & Exploration

Exploring the Night Sky

Star Charts for Hawaii

Our Sacred Earth

Malama Hawaii Projects

Northwestern Islands

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Education

Closing the Triangle: 
The Challenge

To get from Hawai'i to Rapa Nui, Hokule'a must travel 2820 nautical miles south (from 20 degrees N to 27 degrees S) and 2760 nautical miles east (from 155 degrees W to 109 degrees). The first three destinations (Nukuhiva, Mangareva, and Rapa Nui) lie upwind of the departure points, so the canoe will have to struggle to get east against the prevailing winds.

The sail from Mangareva to Rapa Nui will be the most difficult, as Rapa Nui lies 1450 miles to the east of Mangareva. (See Sailing Strategies.) On this leg, Hokule'a will be navigated without instruments by a team of Hawai'i's best navigators, headed by Nainoa Thompson. They will guide the canoe by celestial bodies (sun, moon, planets, and stars), ocean swells, and land-based sea birds.

Rapa Nui is a small, isolated island, making it a difficult target for the non-instrument navigator. Traditional non-instrument navigation, or wayfinding, cannot achieve the pinpoint accuracy of satellite navigation. The wayfinder sails into the vicinity of his destination and begins looking for the island. He may find an island close by and re-orient the canoe to his destination. The fact that many islands in the Pacific are part of island chains, with relatively closely-spaced islands made this sort of navigation practical in ancient times. However, there are no islands close to Rapa Nui. Pitcairn, the nearest inhabited island, is 1150 miles to the west.

Furthermore, Rapa Nui is a small, low island, a triangle 13 x 11 x 10 miles, whose highest point is the 1674-foot Terevaka. To find this island, the wayfinders will have to sail within 46 miles of it, in clear weather, during daylight hours. (Formula for seeing objects at sea: Distance in Nautical Miles = Square Root of the Object's Height (in feet) + Square Root of Observer's Height (in feet; the height of the observer on the canoe, when the observer climbs the mast, is approximately 25 feet high).

The wayfinders plan to use dead reckoning (estimating distance sailed, based on estimates of direction, speed, and time) and latitude stars (see below) to get within a couple hundred miles of Rapa Nui, then employ a zigzagging search pattern along the latitude of Rapa Nui (27 degrees S) to find the island. The zigzags in the pattern must be close enough together, so that the canoe will not sail past the island unseen just over the horizon.

Wayfinders in the Pacific Ocean have traditionally used land-based seabirds flying home in the evening or flying from home in the mornings to fish. This clue to the direction of land expanded the target island, by a radius of up to 150 miles around the island. Once Rapa Nui had a thriving population of seabirds. In 1934-35, while conducting research on the island, Alfred Metraux reported gray, white, noddy, and gray-backed terns, as well as boobies, tropic birds, and frigates. Today Rapa Nui has few seabirds. A hawk introduced to the island to control the rat population has reduced the bird population. Thus, this landfinding technique is no longer available to the Hawaiian wayfinders.

The quest to reach Rapa Nui will be made in the early spring of the Southern Hemisphere (September-October), when storms around Antarctica may break down the easterly trade winds and bring westerly winds. The wayfinders will observe the weather patterns that set up to figure out the best strategy for reaching the island. Starting on September 15, the crew on Mangareva will wait for favorable winds to launch.

The voyage to Rapa Nui is the most challenging voyage undertaken by the Polynesian Voyaging Society; the results are uncertain. The probability that the wayfinders will find the island is not high. The highest priority is the safety of the crew. In searching for Rapa Nui, PVS will place a time limit on how long the crew will search for the island-around 40 days, after which limited food and water and fatigue may become safety issues. But whether the Hokule'a reaches Rapa Nui or not, we know that the early Polynesians did so.

Beyond reaching the destination, what is important for the Polynesian Voyaging Society is to honor the great achievements of our Polynesian ancestors, to learn what we can about how they accomplished what they did, and pass on what we learn to future generations.