The
Tjeld class was based on a prototype fast patrol boat, the
Nasty, developed and introduced as a private venture by Boat Services Ltd. A/S,
Oslo, in close cooperation with
Royal Norwegian Navy officers with
World War II experience in fast patrol boats; the chief designer being naval architect
Jan Herman Linge. The Norwegian
Tjeld-class vessels were constructed at
Westermoen Båtbyggeri in
Mandal. The first group of twelve vessels was ordered in 1957, launched between 1959 and 1960, and commissioned in 1960-1962. A second group of eight vessels was ordered in 1962, launched 1962-63, and commissioned 1963-66. The design was also marketed abroad, to the then-
West German Navy and the
U.S. Navy, where they were known as the
Nasty class, and to the
Hellenic Navy as the
Tjeld, or Improved
Nasty type. The U.S. Navy operated twenty of the
United States Nasty-class patrol boats, with pennant numbers PTF-3 through PTF-22, primarily in the conduct of riverine warfare during the
Vietnam War. A subsequent improved version, the
Osprey class, was larger with aluminum instead of wooden hulls, of which four were operated by the U.S.Navy, PTF-23 through PTF-26. Many examples were later transferred to and operated by
Naval Reserve units in the 1970s and 1980s, until phased out of service. A handful survive as museum articles, either restored or currently undergoing restoration. ==Service history==