SAILING IN THE ITCZ FROM CHAGOS TO THE SEYCHELLES

SAILING IN THE ITCZ FROM CHAGOS TO THE SEYCHELLES

JUNE 4-18, 2016

We departed Saloman Atoll at 1330 hrs on June 4^th, 2016 bound for Port Victoria, Seychelles about 1000nm distant.  All of this voyage was going to take place in the Intertropical Convergence Zone (ITCZ) which lies on bothe sides of the equator and is known as the doldrums in the Atlantic Ocean.  This doldrums’ belt is not so distinctly defined as in the Atlantic and Pacific Ocean because it is influenced by the monsoons.

The winds and weather of the entire Indian Ocean are dominated by the monsoons which have a bearing on the South Indian Ocean.  The NE Monsoon prevails when the sun has a southern declination and the SW monsoon when the sun’s declination is north.  As the sun moves north, it becomes winter time south of the equator.  There is a transitional period which coincides with the movement of the ITCZ which separates the air masses of the northern and southern hemisphere.  This is an area which is inherently unstable with frequent squalls, gusty winds and calms.

Most vessels that intend to make this passage try to time it when the SE Trade Wind is starting to push north towards the equator.  This movement usually happens in the mid-May/June period but it’s difficult to time it and it varies from year to year.  That is what was happening with the five yachts moored in Chagos:  waiting for the SE Trade Wind to make itself felt.  It just wasn’t happening.  Several different government meteorological agencies publish GRIB’s which show the movement, speed, wave height, precipitation, etc. of air masses.  These can be downloaded onto a computer and analyzed.  Every yacht in Chagos and Addoo, Maldives was assiduously doing this but the SE Trades were still 8-10 degrees south. Saloman Atoll is at 05-21’ S.  One would have to sail south for over 200nm to find them which would necessitate departing from the rhumb line that distance and then making it up again.  Instead, there is a compromise where the modern yacht either carries enough fuel to motor sail a huge portion of the distance or is forced to lie ahull and wait for wind.  Phyllis  and I were in the latter category because we didn’t have enough diesel to motor sail any great length of time.  We had never been faced with the windless conditions we found on this passage.  This forced us to lie ahull in confused seas and wait for wind – any wind, whether it was coming from squalls or just lasted a few hours and died out.  It wasn’t comfortable and took quite a long time to make the voyage but it worked.  We arrived in Port Victoria, Seychelles with about a half tank of diesel.  I couldn’t judge this accurately in the confused seas and the electronic fuel gauge was acting strangely and couldn’t be trusted.

Here is a look at the log for the voyage:

June 4^th 1230 hrs to June 5^th 1200 hrs = 131 nm in SE wind 12-15 kts

June 5^th 1615 hrs – June 6^th 0300 hrs:  No wind/hove to (10h-45 min becalmed!)

June 5^th 1200 hrs:  we only made 36 nm in a 24 hr period.

June 6^th 1430 hrs to June 7^th 0800 hrs:  No wind/hove to.  At 1200 hrs we had only managed to make good 19 nm!  The current was actually setting us back in the direction we came from!  Depressing.

June 8^th 1200 hrs:  we had wind and made good 70 nm for the 24 hr period.  Slow

June 9^th 1200 hrs:  116nm made good.  We had very strong wind from the NNE at 25-30 kts.

June 10^th 1200 hrs:  80 nm made good.  Frequent calms and light wind mixed with squalls.

June 11^th 1200 hrs:  88 nm made good.  Same bag of calms, squalls and light NNE’ly wind.

June 12^th 1200 hrs: 18 nm made good.  There was not a breath of wind for over 14 hrs.  I thought it had gone away for good!

June 13^th 1200 hrs:  42 nm made good. A mixed bag of being becalmed and a light E’ly wind.

June 14^th 1200 hrs: 26 nm made good.  Mostly becalmed but, at times, a very light SE’ly wind at 5kts.  Big swells out of the south.

June 15^th 1200 hrs:  52 nm made good.  Wind was from the SW-SSW at about 10-15 kts and then slowly started to die out but never actually did which allowed us to continue sailing.

June 16^th 1200 hrs:  112 nm made good.  The SE’ly Trade Wind finally started to make itself felt and was blowing at about 15kts.

June 17^th 1200 hrs: 121 nm made good.  The SE Trade wind is blowing from 10-20 kts and gusty.

June 18^th 0936 hrs:  85 nm made good.  I shortened sail to arrive at the  designated Quarantine Anchorage in daylight (04-37.097’ S; 055-28.491’ E).  The SE Trade wind was starting to blow 15-20 kts.

1154 hrs:  “Free Practique” granted by Seychelles officials.

1215 hrs:  Weigh anchor and U/W to North Eden Is Marina.

1336 hrs:  All fast at North Eden Island Marina: (04-38.398’ S; 055-28.471’ E).

The total calculated distance made good on this voyage is 977 nm but it was over 1000 nm with set and drift while being becalmed.  It took us 333 hrs = 13 days 21 hrs with an average speed of 3.0kts.  This is about what a person can do on a fast walk!  The lack of wind combined with the confused seas and big swells coming from the south made this a particularly uncomfortable sail.  It is very difficult to keep wind in a battened mainsail if the wind is very light and the sea is big and confused.  The seas cause the wind to roll out of the sail and it begins to flog back and forth.  This can damage the sail so it has to be taken down.  The only way we have been able to sail in these light winds and confused seas is with a poled out Genoa.  This is a headsail on a special pole that is attached to the mast and adds control and stability to the sail so that it doesn’t collapse.  It doesn’t provide the best balance to the overall motion of the yacht and has a tendency to cause it to roll.  Nevertheless, we haven’t found a better solution yet.

What adds to the difficulty of this passage is that the Equatorial Counter Current is setting against you.  It meanders mostly to the East but has a North and Southerly component at times.  When we were becalmed, which was a lot, I was able to plot it out and could see the direction it was setting.  It’s strength, at 06 degrees south, was 0.75- 1.5 kts per hr:  That’s 18 – 36 nm a day!   This is not such an important consideration if the SE Trade wind is blowing as it is easily overcome but to be becalmed and drifting becomes crucial.  There were times when we were becalmed that we were set back 8nm to the East, North or South.  I thought the S’ly set was more favorable as it was sending me in the direction of the SE Trade winds.

“In days of old,

When ships were bold,

And engines were not invented.

They set their sails,

In Trade Wind vales,

So frequent calms were prevented.”

A limerick that came to me during all the calms we suffered through.  For any yacht that wishes to sail this route instead of motoring, it is well worth while to wait for the SE Trades to establish themselves or sail south to find them and the favorable west setting Equatorial Current.  It’s what the great wind ships of yore did.  Outside of that,  carry enough diesel to motor most of the distance on the rhumb line.