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Modern Wayfinding: Course Strategy and Departure Time
[Photo Below: A Voyage from Hawai'i to Tahiti Takes the Canoe Across the
Doldrums]
 Before
a voyage by sail begins, the wayfinder designs an ideal course for
reaching the destination from the starting point, given the
capabilities of the vessel and the winds, currents, and weather
conditions anticipated along the way. The course should represent the
most efficient way of getting to the destination, given all the factors
listed above. The wayfinder must also choose the right time to go (when
the wind and weather conditions are the most favorable), taking into
account the timing of the return voyage as well.
Hawai'i to Tahiti
A course strategy can be illustrated using a Hokule'a voyage to Tahiti
as an example. The best time to sail to Tahiti is in the late spring or
early summer-in between the storm seasons and the hurricane seasons
north and south of the equator in a typical year.
Sailing to Tahiti is a challenge because Tahiti lies to the south southeast of
Hawai'i, upwind and upcurrent, so the canoe must sail
east into the wind and current for most of the way. The canoe crosses the NE and SE tradewind zones as well as two great west-
flowing ocean currents-the north and south equatorial currents, which can carry the canoe 14-20 miles westward per day.
On the 1992 voyage to Tahiti, Hokule'a's reference course line ran SE
by S, sailing on a close reach, full and by the wind, until about 9
degrees N latitude or 700 miles from Hawai'i. This course line
represents the course the canoe would sail to get to Tahiti under
average wind conditions, given the sailing capabilities of the canoe.
However, wind conditions are never average, and the canoe deviates from
this reference course, sailing in whatever direction the winds allow it
to sail, and the wayfinder modifies his course accordingly. The
objective of the wayfinder is not to stay on his reference course, but
to get to his destination.
At about 9 degrees N, the canoe enters an area called the Intertropical
Convergence Zone
(ITCZ), which lies between the NE and SE trade wind systems (and the
west flowing north and south equatorial currents). This region, where
the NE and SE trade winds converge, is noted for its heavycloud cover,
squalls, light and variable winds, and dead calms, all of which make
sailing and navigating less than ideal. The windless weather, a
condition known as the doldrums, could stall the canoe for days. The
heavy cloud cover hides the stars, so navigating by the celestial
bodies is difficult. Under such conditions, the wayfinder uses the
ocean swells to orient the canoe. However, confused seas in the area,
without clear swell patterns, may make steering by the swells difficult
as well.
The days of calm and heavy cloud-cover test the patience and intuition
of the
wayfinder, but the doldrums have a unique beauty: on days when sunlight
is diffused in the heavy cloud cover, the sea mirrors the golden light;
on clear nights, the sea surface can be so smooth that the stars and
constellations are reflected in it; on nights of 100 percent cloud
cover, the ocean and sky are pitch black.
In the ITCZ, between the two west-flowing equatorial currents, is the
eastflowing equatorial countercurrent, which results from the water
pushed west by the tradewinds flowing back east parallel to the
equator. This countercurrent could help the canoe gain easting.
However, the countercurrent is sporadic and shifting. It is generally
weakest in MayJune and strongest in September-
November, when its speed can reach about 1 knot. Occasionally the
countercurrent becomes stronger, as it has in 1992, because of El Ni–o,
a weather condition which brings westerly winds to the Southern Pacific
and dangerous hurricanes. During the last major occurrence of El Nino,
in 1982-1983, Tahiti was hit by six hurricanes.
The canoe tries to get out of the ITCZ as quickly as possible, sailing SSE in the shifting winds.
Once the canoe is in the south east trade wind zone, at about 3 degrees
N, the strategy is to sail south against the E to ESE winds, without
losing any easting, until the canoe reaches one of the islands in the
target screen, which stretches 400 miles E to W from Manihi in the
Tuamotus to Maupiti in the Society Islands. If the canoe has enough
easting, it will make landfall east of Tahiti and it can head downwind
(SW) to to its destinatio (Adapted from Will Kyselka's Ocean in Mind.
Honolulu: UH Press, 1985.)
Rarotonga to Hawai'i-1992
Course Strategy Designer: Nainoa Thompson, Sailmaster of the Hokule'a
Starting Point: Rarotonga in the Cook Islands (21 degrees 14 minutes S latitude; 159 degrees 46 minutes W longitude)
Target Screen: The Hawaiian Islands, between 18 degrees 30 min. N latitude (25 miles south of Ka
Lae, or South Point) and 22
degrees 30 min. N latitude (16 miles north of Kaua'i), or 240 miles S to N; and between 154 degrees 40 min. W longitude (25
miles east of Cape Kumukahi) and 160 degrees 20 min. W longitude (Ni'ihau), or 340 miles E to W.
Destination: Hilo, Hawai'i
Estimated Length of Voyage: 2,749 miles; about 26 days.
Sailing Plan
1. NNE at 5 knots from Rarotonga to 3 degrees N latitude
2. N by W at 2.5 knots through the doldrums (3 degrees N to 9 degrees N) 3. N by W at 5 knots to 20.5 degrees N latitude,
arriving about 85 miles east of the Hawaiian Islands.
4. W at 5 knots until one of the Hawaiian Islands is sighted.
Based on the average wind and currents between Rarotonga and Hawai'i in
November, and the sailing capabilities of the canoe (5 knots or 120
miles per day in 10-20 knot winds,with a windward ability of 68 degrees
off the direction of the wind), the voyage is designed in four
segements:
Segment 1: In the Southeast Trades
Latitudes: 21 degrees S to 3 degrees N
Average Wind Conditions: Southeast trades, from E to ESE at 10 to 20
knots. Current: South Equatorial Current; west-flowing; 0.5 knots; 12
miles per day (0.5 knots x 24 hours)
Average Canoe Speed: 5 knots; 120 miles per day (5 knots x 24 hours); Heading: NNE; Actual heading with current factored in:
between NNE and N by E
Total Distance to be Travelled: 1,572 miles (Pre-voyage estimate); Total Time: 13.1 days (1572 miles Ö 120 miles per day)
Segment 2: In the Intertropical Convergence Zone (ITCZ)
Latitudes: 3 degrees N to 9 degrees N
Average Wind Conditions: Variable; generally out of the east; 0 to 10 knots
Current: Equatorial Countercurrent; east-flowing, but unpredictable
Average Canoe Performance: 2.5 knots; 60 miles per day (2.5 x 24
hours); Heading: NNE; Actual heading: NNE (No compensation for current
drift. While the Equatorial Countercurrent runs east in this area, it
is unpredictable and may or may not take the canoe eastward. However,
if the countercurrent is flowing, it will benefit the canoe by helping
it to get east of its target of
Hawai'i. And if the canoe is in the doldrums for a great length of
time, the wayfinder may have to take this east-flowing current into
account and reestablish the position of the canoe farther east of the
position estimated without compensating for the current.)
Total Distance to be Travelled: 390 miles (Pre-voyage estimate); Total Time: 6.5 days (390 miles - 60 miles per day)
Segment 3: In the Northeast Trades
Latitudes: 9 degrees N to 20.5 degrees N
Average Wind Conditions: NE Trades, generally from NE by E; 10 to 20 knots Current : North Equatorial Current; west-flowing;
0.5 knots; 12 miles per day (0.5 knots x 24 hours)
Average Canoe Performance: 5 knots; 120 miles per day (5 knots x 24 hours); Heading: N by W; Actual heading with current
factored in: between N by W and NNW
Total Distance to be Travelled: 702 miles (Pre-voyage estimate); Total Time: 5.85 days (702 - 120 miles per day)
Segment 4: Westward Home
Latitude: 20.5 degrees N
Average Wind Conditions: NE Trades, generally from Noio Ko'olau (NE by E); 10 to 20 knots
Current: North Equatorial Current; West-flowing; 0.5 knots; 12 miles per day (0.5 knots x 24 hours)
Average Canoe Performance: 5 knots; 120 miles per day; Heading: W; Actual performance with current factored in:132 miles per
day
Total Distance to be Travelled: 85 miles (Pre-voyage estimate); Total Time: 0.7 days
Departure
The departure date of October 20 from Rarotonga was determined by two
factors. First, to avoid the winter storm seasons in the southern and
northern hemispheres. October is ideal because it is in-between the
southern hemisphere winter (June-September) and the northern hemisphere
winter (December-March) when the probability of encountering storms is
greater than at other times of the year. October also falls between the
hurricane season in the northern hemisphere (June-September) and the
hurricane season in the southern hemisphere (December- February).
Another important factor in setting a departure date is the moon phases
during the voyage. The voyage is timed so that there is moonlight at
strategic points. A bright moon is desirable while the canoe is in
doldrum conditions (around 3 degrees N to 9 degrees N), so the
wayfinder can see the ocean swells at night when heavy cloud cover is
hiding the canoeguiding stars. An experienced wayfinder can steer by
maintaining a consistent pitch and roll in the movement of the canoe;
but seeing the
swells is an added clue in maintaining his direction.
Moonlight is also important as the canoe approaches Hawai'i because the
wayfinder will use the altitude of stars above the horizon to determine
his latitude; on cloudy nights with little or no moonlight, the horizon
line cannot be seen; moonlight renders the horirzon visible. The voyage
from 1992 voyage from Rarotonga to Hawai'i was planned so that the
canoe would have a waxing (increasing) quarter moon as it reached the
doldrums (approximately Nov. 3) and a waxing crescent moon as it
approached Hawai'i (around Nov. 24).
Two other factors need to be met for the canoe to depart on a voyage:
1. the canoe and crew have been properly prepared;
2. the weather is right, based on (a) meteorological reports (no major
storms are headed for the course) and (b) observations of wind
direction and speed, the shapes of clouds, and the color of the sky at
the horizon at sunrise to determine that good sailing weather would
hold for a couple of days.
Islands Along the Way
When the canoe sails out of Rarotonga on a NNE course, the wayfinder is
aware of islands along the way, on which he will want to avoid running
aground in the dark. Manuae (Hervey Island) is only 15 miles east of
the course at 19 degrees 21 minutes S and Aitutaki is 42 miles west of
the course at 18 degrees 54 minutes S. The canoe will leave early
enough in the day to pass these islands during daylight.
As the canoe continues NNE, it will pass on its port side:
Manahiki - 10 degrees 23 min. S
Rakahanga - 10 degrees S
Penrhyn - 9 degrees S
Starbuck - 5 degrees 37 min. S
Malden - 4 degrees 03 min. S
Kiritimati (Christmas) - 1 degree 52 min. N And on its starboard side:
Flint - 11 degrees 26 min. S
Vostok - 10 degrees 06 min. S
Filippo Reef - 5 degrees 31 min. S
These islands and reefs represent both a danger and a safety margin.
The danger is running aground on one of them in the dark; however, if
the wayfinder sights one of them and can identify it, he will know the
canoe's position, whether it is too far east or west of his intended
course. Even without sighting the islands, seabirds can be a clue that
an island or islands are nearby.The two most reliable indicators of
land are the manu-a-Ku (fairy tern) and the noio
(noddy tern), which often fly out at sunrise from their nesting islands
to fish in large groups and return at sunset. The general range of the
manu-a-Ku is around 120 miles from land, though it can fly farther out
and remain out at sea for days, or it can fly back to land in the dark
without being sighted. The range of the noio is about 40 miles from its
home island.
The Turn West
As Hokule'a approaches the latitude of Hawai'i upwind from the islands
(i.e., to the east of it, as his course strategy requires), the
wayfinder has to make a major course decision: when to turn the canoe
downwind, west toward
Hawai'i. Ideally, this turn should be made at 20.5 degrees N (the
latitude of the midpoint of the S to N target screen between the Big
Island and
Kaua'i). The wayfinder determines his latitude by the altitude of
Polaris and by the altitude of stars as they cross the
meridan. (See "How the Wayfinder Determines Latitude")
Landfall
The manu-a-Ku (fairy tern) and the noio (noddy tern) will help to
expand landfall, indicating the presence of the islands before any
island can actually be seen. When the canoe crew sights and identifies
any one of the Hawaiian islands, the wayfinder will know exactly where
the canoe is and head toward Hilo. Given clear atmospheric conditions,
the high dome of Mauna Kea, about 14,000 feet in elevation, can be seen
from over 100 miles away; when the dome is obscured by clouds or
volcanic haze, visibility is reduced to about 20 miles. If the canoe
approaches the Big Island from the SE at night, the first sign of land
may be the glow of volcanic activity in Puna.
The Reference Course.
The reference course represents the course the canoe would sail given
average wind and current conditions and the canoe's performance
capabilities. It is highly unlikely that the canoe will stay on the
reference course because wind direction will vary along the way, and
the canoe can only sail in the direction the wind allows it to sail.
The art of wayfinding involves adapting to variable and unexpected
conditions of wind and weather while maintaining progress towards the
windward side of the targeted islands.
The reference course is used as a local longitude line between the
starting point and destination. The wayfinder can plot his position
east or west of the line as the voyage progresses. If the wind pushes
the canoe off the reference course, the canoe will eventually try to
get back to it, or close to it, when the wind allows the canoe to do so.
The wayfinder's reports of his position east or west of the reference course are estimates based on his estimates of the
following:
1. the speed and direction of the canoe is traveling
2. the speed and direction of ocean currents
3. latitude (based on measurements of the altitudes of stars crossing the meridian)
These estimates are made without instruments, and can be hampered by
poor weather conditions which obscure the sky and confuse the seas. The
speed and direction of ocean currents cannot be measured or even
estimated without instruments, so the figures used are seasonal
averages rather than actual measurements. The accuracy of the estimates
can also be affected by mental fatigue. The wayfinder must track and
memorize the canoe's performance over 2,000 miles and three-and-a-half
weeks at sea, while getting as little as a couple of hours of sleep a
day.
But wayfinding doesn't require exact positions to be successful. The wayfinder will be successful if he is able to
-keep track of where he is in relationship to his reference course and destination
-guide the canoe to the general vicinity of his destination
-locate land in that vicinity and use known landmarks to get to his destination
Within the limitations of the wayfinder's estimates, these three things
are possible, as the success of Hokule'a in making landfalls in the
past has proven.
The 1992 Voyage
During the actual 1992 voyage, the wayfinders modified the sail plan
from the beginning. Instead of leaving October 20, they waited for
winds that would allow them to go east. Southerly winds came on October
26; instead of heading NNE, the canoe took advantage of the winds and
headed E to Tahiti, arriving in Pape'ete on November 1. The canoe again
waited for the right winds, and on November 5 left for Hawai'i, heading
N by E. Instead of taking just 26 days, the voyage took 35 days
(including the 4 day stop in Pape'ete). The crew saw the lights of Hilo
town and the beacon from the lighthouse at Kumukahi on the night of
November 29; they sighted the Hamakua coast of the Big Island on the
morning of November 30.
Nukuhiva to Hawai'i
Question: What course will Hokule'a sail from Nuku Hiva to Hawai'i?
Preliminary Considerations-What month, time of the month, and time of the day would you depart? Given the average winds and
currents,what course would you sail to Hawai'i? From which direction would you approach your destination? How far might the
currents carry you east or west as you head north?
How wide is the target screen (from Ni'ihau to Hawai'i)? Draw a box
around the target on a nautical chart or map and give the N-S, E-W
dimensions of the target. How far north or south of the islands could
you be and still see them? How far east or west could you be and still
see them?
Formula for the range for sighting land: Square root of h + square root
of H = the distance in miles from which an object can be seen; h =
height of observer in feet; H = height of object in feet. The deck of
Hokule'a is about 4 feet high.
Givens
-Position of islands (on Nautical Chart 526, if available)
-Size of Targeted Islands (North-South, East-West dimensions).
-Average Wind and Currents between Nuku Hiva and Hawai'i:
Southeast Tradewind Zone (Nukuhiva to 3 degrees N Latitude): Average Wind Speed: 15 knots (nautical miles per hour) from the
East; Average Current Speed: West-Flowing at 0.5 knots.
Intertropical Convergence Zone (3 degrees N Latitude to 9 degrees N Latitude): Average Winds: Doldrum conditions; light and
variable, averaging 7.5 knots from the East; Average Current: Unpredictable; cannot be factored into your course line.
Northeast Tradewind Zone (9 degrees N Latitude to the Latitude of
Hawai'i): Average Wind Speed: 15 knots from the ENE; Average Current
Speed: WestFlowing at 0.5 knots.
-Canoe Performance: windward ability = about 67.5 degrees or six houses
off the direction of the wind; speed of canoe = 1/3 speed of wind.
Supplementary Questions
Length of Trip: Using your course line and assuming average wind conditions, how many days will it take you to sail to
Hawai'i? How many miles would you travel?
Capacity: Given the carrying capacity of the canoe 5.5 tons (11,000 pounds), how many people would you take? How many
gallons of water? How much food?
Assume: The food supplies needed per day for each crew member will weigh 5 pounds; he or she will consume a gallon of water
a day; water weighs 8.6 pounds per gallon; each crew member will be allowed to take 20 pounds of personal gear. The equipment
on board the canoe will weigh about 2.5 tons. (Equipment includes electrical and communication equipment, safety gear,
anchors, various sizes of sails and extra ropes and lines, galley and cooking utensils, and tools.)
At the end of the exercise have the participants compare their course
lines, estimates of the time and distance of the trip, number of crew
members, and amount of food and water they plan to carry.
Questions for Open Discussion
1. What would you take for survival at sea and why?
2. Who would you take and why?
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