In terms of the third situation of motor vessel with auxiliary sails (i.e. wind-assisted propul­ sion), King (1985) argues that the best possibility is to be found 'at the top end of a vessel's speed range1. This does not, however, preclude fuel sa­ vings at lower speeds through improved stability or use of sail propulsion alone under favourable condi­ tions. As King points out, the extent to which wind power can be relied upon must depend upon the para­ meters of acceptable performance. A small inter­ island trading vessel is likely to have more flexi­ bility in this regard than a large modern bulk car­ rier for which the profit margin on a charter de­ pends critically on elapsed voyage time.