By the Light of the Silvery Moon
Vega
Hugh and Annie
Sun 8 May 2016 14:04
With the wind predominantly from the east, cruising up or down the Caribbean should be plain sailing. However, we soon discovered that no matter what direction we were heading we seemed to be going into the wind. Sailing down from Martinique to St Lucia we were close hauled to the south east wind but with 30 degrees of leeway we would have been in Panama before St Lucia without the engine. So, closer reading of the cruising guides and all the information on the back of the Imray charts has been required……………
The first thing learned is that sailing around the islands needs to be approached differently from sailing between the islands. Around the islands the wind will be particularly affected on the leeward side by the landform. It may be blanketed by the land and less strong than on the windward side. On the other hand it may be funnelled down the valleys between the peaks and blast out much more strongly. This was a feature of anchoring between the Pitons on St Lucia. At the ends of the islands the wind may bend around the land and come from a completely different direction. Being prepared for anything seems to be the rule and on a windy day a couple of reefs in the mainsail would be prudent.
South of Antigua the north east trade wind changes to blow predominantly from the south east. This means that if generally heading south, routes between the islands need to be planned to avoid sailing directly south east and into the wind. This can affect the best point of departure from one island to the next and also the order in which the islands are visited. However, another really important factor is the current that flows from east to west at around two knots. It is this that caused our leeway between Martinique and St Lucia and is where the tide becomes significant. We left Martinique from Pitite Anse d’Arlets but in fact would have been better leaving from St Anne (see map). The flood tide flows from west to east and can significantly reduce the effect of the general current (the ebb tide does the opposite of course). The tides are governed by the moon. As the moon rises the flood tide is pulled in until the moon passes its zenith (maximum height) over a period of about six hours. As it sets the ebb tide flows in a westerly direction as the effect of the moon declines. The same thing happens when the moon is below the horizon i.e. on the other side of the earth so that every day you have four six hour periods - two of flood tide and two of ebb. Inter island passages are therefore planned around the wind and the moon to ensure that, as far as possible, you are not sailing directly into the wind when the tide is ebbing.
Armed with our new appreciation of these conditions we planned a 4am departure from St Lucia to St Vincent to coincide with the rising moon. It was actually 5.20am by the time we had wilfully ignored the alarm and revived ourselves with tea but still early enough to ensure a blissful fetch (midway between a reach and a beat (close hauled)) until past the north end of St Vincent. Sailing down the east side of the island the prevailing current then swept us around the south side to our destination - the best sail over here so far.
Knowing when the moon is rising is easy with a full moon - it is in the dark just after sunset and very visible. At other times it may be during the day and less obvious and recourse to the internet or local tide tables is needed. Or, as we have remembered but yet to investigate, the electronic charts should also give tidal information that doesn’t require lunar input.
Ah, but
By the light,
Of the silvery moon………………….