These are the two experimental Vosper FF. No.80 was steel and the un-numbered one aluminium.

photos show the various types of FF as operated by the Marine Branch of the RAF. No type. 1 is a 37.5ft conversion., Nos 2&3 are 40ft conversions and No.4 is a 38ft

HI FIREBOAT reference the RAF FIRE FLOATS/TENDERS here goes. FIRE FLOATS/TENDERS/CRASH TENDERS etc.,were converted from SEAPLANE TENDERS thus.

37.5ft ST. designed by Fred Cooper and built by the British Power Boat Co., and trialled by 'Lawrence of Arabia'. They were the first dedicated high speed boats built for the RAF in 1931 and were dubbed 'narrow beams'.
ST.MK1 - RAF Nos. 200-291., powered by twin 'Power Meadows' 100HP petrol engines.
ST.MK.2 - RAF Nos. 292-303., 323&324. powered by twin Perkins S6M diesels.

Some were later converted to FIRE TENDERS -
37.5ft.MK.1 - RAF Nos.FT.1., 36 & 40.
37.5ft.MK.2 - RAF Nos. 37,43 & 44.

38ft. 'WALTON' type ST. built by the Walton Yacht Co. from 1940 and powered by twin Perkins S6M diesels with a top speed of 26 knots.
38ft. MK.1 - RAF Nos. 314-322., 325-356., 422-424.
Some were later converted to FIRE TENDERS as follows.
38ft. FT.MK.1 - RAF Nos. FT.66,72,77 and 78.
38ft. FT.MK.1A - RAF Nos. FT.65,67,69 and 70.

40ft. 'WHITE' type ST.(lead builder Samuel White but sub-contracted to other yards) all were powered by twin Perkins S6M diesels. Entered service in 1940 with a top speed of 23 knots.
40ft. MK.1 - RAF Nos. 304-313., 367-399., 402-421., 425-435., 446-486., 1520-1591., 1625-1627.
Later FIRE TENDER conversions were -
40ft. FT.MK.1 - RAF Nos. 38,39,41,42,45,46,51 and 55.
40ft. FT.MK1A -RAF Nos. 52,54,57,59,62,63,64,82,89,90,
91, and 901-910.

41.5ft B.P.C. ST. (broad beam) designed by George Selman and on entering service in 1941, proved to be a magnificient seaboat and by far the best type ever built for the wartime RAF. Powered by twin Perkins S6M diesels with a top speed of 23 knots.
41.5ft. ST.MK.1 - RAF Nos. 357-366., 436-445., 1500-1519., 1592-1605.
41.5ft.ST.MK.1A - RAF Nos.1606-1624., 1628-1635.
Only two of the class were converted to FIRE FLOATS, these were RAF Nos. FF.87 & FF.88.

To further confuse the issue VOSPERS built two 40ft. SEAPLANE TENDERS MK.2 in 1937 as yard Nos.1822 and 1823. They carried the RAF Nos. 400 and 401 but were never converted to FF.

Post war some of the above 41.5ft. craft were re-designated RANGE SAFETY LAUNCHES and numbered as RSL. 1636-1639.,1646 and 1647.

VOSPER, in 1950, also built two prototype FIRE FLOATS for the RAF. The first was a galvanised steel hulled craft. RAF.No. 80., 55ft long with a speed of 12 knots and powered by four Perkins S6Ms with self changing gearboxes and Anderton clutches, driving twin Rotol VP props.

The second was FF.81 a 60ft. Aluminium Alloy built craft. powered by twin General Motors 64-HN-5 diesels driving a
Voith Schnieder propulsion unit with a top speed of 12.5 knots.

Although given RAF numbers, They were not taken on charge by the RAF.

This only leaves 93 and 94.

Hope this clears things up (or just muddies the water)

HI guys. I can assure you that no Mk.1 version of the FIREFLOAT was ever built for the RAF and the only drawings that exist are those that you see on the research and plans page. What creates some confusion is the earlier S.T. conversions which were classified as FIREFLOAT Mk.1 and were 37.5., 40.0 & 41.5ft boats.