There has recently been some discussion on the suspected ‘sailing effect’ experienced by ships lying immobilized in a seaway. It was suspected that drift direction may not be truly down-wind, and that on VLCCs in the ballasted condition the sailing effect could be magnified. Few practical data were however available and could easily be spoiled by the effects of current, or become unreliable if established under the influence of light to moderate winds.

An unusual set of circumstances combined on the 3 August 1977 when I was Chief Officer of the Shell tanker SS Lima on her maiden voyage to the Persian Gulf. As can happen early in a ship's life, trouble developed in the engine room requiring the boiler to be shut down for about two days. The first signs of the problem were discovered a few days earlier but the stoppage was planned so that the ship would have plenty of sea room when undergoing repairs. A position off Maputo was chosen, and when within the selected area the ship was stopped and the repairs carried out. During this period the ship was allowed to drift freely and as usual daily positions were obtained at morning and evening twilight and at noon. Figure 1 is an outline chart of the area showing the observed positions. For these times the ship's head is also given, in addition to the associated wind direction and speed.