My previous work in this thread apparently didn't found anyone's favour. Maybe this one will fare better.
was a mid-1930s attempt of Regia Marina to build a large (in the 50-ton range, instead of hitherto typical 15-20-ton range) motor torpedo boat (capable of being also used as minelayer and submarine chaser). Differently from these smaller boats, which were classed as "motoscafo armato silurante", new vessel was classed as "mototorpediniera" ("torpediniera" was a designation of large torpedo boats). Ship was laid down in May 1935 at CMA shipyard in Marina-di-Pisa and launched on 9 of May 1936 r.
It's standard displacement was 51,5 t, normal 61,68 t, total length 32 m. It was powered by 4 FIAT V-1616 diesel engines with total power 3000 hp and was armed with 4 450 mm torpedo launchers, 2 Breda 13,2 mm machine guns, 1 FIAT 6,5 mm machnie gun and 2 depth charge launchers.
Although modern-looking, due to large amount of new technologies applied in its construction, it failed to met it's promise. Although it was hoped that it would achieve speeds in range of 40 knots, during trials it never exceeded 34,62 knots, and when fully laden only 32 knots. Main reason for that were engines, as FIAT had no previous experience with making diesels of that size and with such performance envelope. Modified engines were installed in April of 1937, but then, in turn, it suffered from a string of crankshaft breaks, which led to its new modification, which lasted for another year (and next series of trials for several further months).
Only on 9 January 1939 Stefano Türr was officially commissioned into operational service in Regia Marina, as part of 1ª Flottiglia MAS in La Spezia. Unfortunately, it was plagued by further malfunctions of engines, plus the corrosion of the underwater hull made of supposedly-corrosion-resistant alloy. As the vessel was spending more time in repairs than in service, it was finally decided to decommission it, which formally took place on 27 July 1941. By then Regia Marina has already obtained several (captured from Yugoslavia) Lürssen-type large MTB's, which confirmed that basic concept behind such category of vessels was perfectly sound (in fact, was the
way to go), but it's execution in form of Stefano Türr was too flawed to bother. Empty hull, with all valuable equipment removed, remained on shore at Spezia arsenal until it was finally scrapped in 1947-1948.
Italy, Stefano Türr