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Fig 5

Text from SCOTSMAN 1948 trials document

H.M. Submarine SCOTSMAN is a 1940 'S' class submarine converted for high underwater speed, approval being given on Admiralty Docket D.T.A/S.W.496/45 and dated 4th December 1946.

Several proposals were considered, the first scheme being as follows:-

Submerged Resistance.

Reduced by (a) surrendering all armament.
(b) replacing "saddle" tanks by "underslung" main ballast tanks of reduced capacity.
(c) streamlining the superstructure and drastically reducing the size of the bridge.

Propulsion.

Battery capacity doubled by fitting two extra battery sections S.H.P. increased by replacing existing 'S' class main motors by 'A' class motors. The maximum S.H.P. is thereby increased to 3600.

'S' class propellers replaced by 'T' class.

Main engines removed and one Paxman high speed diesel generating set (ex 'U' class) fitted. This, while not sufficient to charge the batteries except at very low rate, is able to assist in this direction and gives the submarine a surface speed of about 6 knots.

'A' class thrust blocks fitted, but existing shafts retained as being suitable for the increased power at 520 r.p.m

General.

Only one periscope fitted. This was a German type approx. 7" diameter. This is only 21½ feet long and. periscope depth in calm water is about 17 feet.

The 7½" periscope gland is used to house an induction tube of this diameter. It is not a snort but will enable the engine to be run on the surface in bad weather when the conning tower hatch is shut.

Fore and after hydroplanes were modified both in size and balance, the fore planes being fixed out.

Principle Particulars.

Length overall 217' 0".
Length between perpendiculars     185' 0".
Breadth moulded 14' 11"
  extreme 15' 0".
Depth, U.S.K. to top of bridge 23' 11½".
Displacement (Surface 794 tons
  (Submerged 875 tons.
Main tank capacity = 81 tons = 10.2% of surface displacement
Draughts in surface condition     (Fwd. 13' 10"
  (Aft. 15' 1½"

These modifications were excepted to enable a speed of 17 knots (deep) to be maintained for 40 minutes.


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Fig 6