Photo courtesy of the UK Imperial War Museum https://www.iwm.org.uk
I have all but finished the 20th scale model of the British Vosper 73' version II boat, this is based on drawings of MTB 523 obtained for me by one of my cousins who worked at Vosper in Portsmouth.
The Vosper boats were built in the Vospers Yard in Portchester in my home town of Portsmouth England.
MTB523 was a late war production and I don't believe it saw any action. The type II was an upgraded 73 footer fitted with an Oerlikon 20mm astern, a British 6 pounder canon replaced it on the bow, two twin .303 Vickers machine guns, one to port and one to stbd and two 18" torpedo tubes mounted further aft towards the stern than the type 1 boats.
These boats were powered by three USA built V12 Packard engines.
The Vosper 73' boat hull, type 1 and type II were both very similar, with the type II fitting a 6 pounder gun on the bow, losing two torpedo tubes and moving the Oerlikon cannon to the stern. These hull's were a relatively flat planing hull but with a rounded keel from about rib 10 onwards, widening out to a larger and larger radii and then tapering off to an absolutely flat bottom at the transom (stern). Other than the rounded keel the bottom tunnel shape is quite similar, in some ways, to the U.S. Higgins hulls, in fact the later Higgins hull removed the slight tunnel effect at the transom, later in the war, and also ended up with an absolutely flat bottom at the transom, the same as the Vosper to apparently improve it's handling.
The photo above shows MTB 523 on builders trials, the first of the Vosper type II's which were very similar in design to the type I boats.
The type I was the slightly longer follow-on from the previous 70ft boats, which had gained gun armament and electronic aids during refits as the war carried on.
The type I boats were quite well armed as built, with 4 x 18" torpedos (as opposed to the far larger and heavier pair of 21" used by the 70-footers), they had a powerful twin 20mm Oerlikon on a MKIX mounting with a "bandstand" forward and two twin gas operated (G.O.) .303 Vickers MGs on each aft tube. The boats of this design were MTBs 379 (the prototype) and MTBs 380-395. The contract for the type II boats was awarded at a time when there were fewer worthy torpedo targets and so the forward tubes were dispensed with in order to save weight so that the mighty 6-pounder quick-firing MKIIA gun on a power operated MKVII mount could be fitted forward and the twin 20mm Oerlikon was moved aft, on a MKXII mounting. Unfortunately none of these boats saw WWII service, as they would certainly have been the most effective Vosper boats of the war. They did however continue to serve in the RN for a number of years after WWII in a number of roles.
For a much larger version click on the picture above or here.
For a much larger version click on the picture above or here.
I have re-drawn the above drawings in AutoCAD to try to match the poor quality printed copies that were from Vospers, some of the text was near impossible to read so I apologise in advance for any errors and in some cases there are xxxx's where the text cannot be made out. I have also replaced the engine box like drawings with my previously drawn Packard images, the remainder is drawn as faithfully as I can.
From these re-drawn drawings I have developed the "lines", which are slices through the hull at set intervals from the centerline and the bottom of the keel.
The "lines" - this is my interpretation at 20th scale.
If you click on the picture above you can get a much larger image or click here.
P.1023 - Notice the 6 pounder cannon has been removed.
For a much larger version click on the picture above or here.
P.1023 was originally built as MTB 523 and was a vosper 73 ft MTB, completed in july 1945, the first contract type II boat.
She displaced 49 tons and was powered by three Packard engines, giving her a top speed of 40 knots, originally armed with a 6 pounder forward, twin gas operated (G.O.) Vickers machine guns, twin 20mm oerlikon cannon and two 18 inch torpedo tubes. She had type 268 radar (ppi type) on her mast. She was renumbered MTB1023 post wwII but was lost in an explosion at Aarhus, Denmark, on 17 May 1953 (https://en.wikipedia.org/wiki/List_of_shipwrecks_in_1953).
P.1032 - Notice the torpedo tubes have been removed but the base is still present, as is the 6 pounder cannon forward. (I am told that P.1032 may have been a 75' boat but the similarities with P.1023 make that seem unlikely).
For a much larger version click on the picture above or here.