trade winds are winds that blow from an Easterly direction on the oceans between 15N and 15S, there you are normally going with the wind, as only a fool (or the British Steel regatta or another record breaking fanatic) would go against them. They are not tail winds as such.....
When sailing you talk about running (going with the wind) or reaching.


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Note added at 25 mins (2003-11-10 17:37:50 GMT)
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or: sailing downwind (standard term) or: in following winds
tail winds are only used for aircraft as a boat has not gor a tail, but only a stern.
(reaching is when you are going against the wind)

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Note added at 44 mins (2003-11-10 17:56:40 GMT)
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following winds:
http://www.weather-wise.com/sail/vendee/Jan3.htm
catamarans:(a type of multiscafo) in following winds:
http://www.weather-wise.com/sail/therace/jan7.htm

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Note added at 48 mins (2003-11-10 18:01:10 GMT)
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alisei are trade winds and depending on the direction you are going in they are venti portanti. They are definitely venti dominanti (prevailing winds) as they only change direction in the hurricane season. Dramatically sometimes....