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HMS Scotsman - 1948 Trials and Experimental Submarine

compiled by Peter D Hulme


The converted Scotsman appeared as I joined the Royal Navy and was in the background during my service in submarines but despite apparently crossing paths I do not recall seeing her in any of her guises. She had a reputation amongst electrical and engine room ratings because of her need for a companion charging submarine throughout her long service.

Moving on over half a century living in retirement in New Zealand, I became intrigued by the odd mention in books and on submarine forums. The high speeds often attributed to this funny little submarine were really not credible and I started research that spanned several years and involved many different sources. This article is a compilation of the information I have gathered with the gaps filled in a hopefully informed manner, using my own electrical background and the design philosophy of the converted T Class that was contemporary with the Scotsman.

The 'Holy Grail' event in my journey, was the fortuitous finding of a copy of the official trials document addressed to Flag Officer Submarines in 1949, by George Malcolmson, Archivist RNSM, who recalled my interest and kindly sent me a copy. He had previously sent me copies of FOSM letters concerning the Scotsman and her programme from 1948 to 1953.

Ian Buxton sent me a useful speed/power table, together with pages from the official 'Particulars of Vessels 1959' in regards to the Astute and Amphion motor performance.

Jeremy Michell, Curator, Historic Photographs and Ship Plans at the NMM kindly provided the critical battery cell data.

Bob Todd, Head, Historic Photographs & Ship Plans Section, NMM and Roger Fry, submarine researcher and photographer, confirmed the dates of the photographs of the different shapes given to the Scotsman over her service.

Others provided memories of their days on the Scotsman and these are reproduced as part of the article, mainly as attributed anecdotes

John Lambert supplied me with a copy of the 1944 official trials document of the streamlined Seraph addressed to FOSM and the same for the converted 'Taciturn' 1952, together with reduced copies of official drawings showing the detail of various S Class submarines. Invaluable primary sources

Keith Allen supplied me with a copy of BR1965 (a description of the electrical propulsion system of the converted T Class) lodged in the Washington Archives, another valuable primary source.

Thanks to John Eade for an anecdote and reading the draft to check if it all made sense.

Not the least Merlin (Ian Hillbeck) for putting the article on his website and the effort involved in doing this.


Certain specific details are lacking about the electrical conversion of the Scotsman but every endeavour has been made to present a sensible picture using the known facts and the techniques used in the Royal Navy T Class Conversion of eight submarines that commenced in 1948 as the converted Scotsman was being commissioned.

The reputable submarine books usually associate the conversion with the streamlining of the Seraph and her sisters but I believe this gives an misleading emphasis While the Scotsman was occasionally used in the ASW target role, this does not appear to have been her main purpose. She was a Trials and Experimental submarine, in practice unable to operate without a companion submarine, largely in the Lochs of Scotland where the Royal Navy had various submarine testing facilities.

The eminent naval author Norman Friedman states on page 58 of his book 'Submarine Design and Development' in regard to Scotsman,

but she demonstrated that a high-speed conversion was practical, and inspired the T Class reconstruction programme.

This has to be qualified by pointing out that the converted Scotsman was re-commissioned about July 1948 with a lengthy trials programmed yet to be completed, while FOSM had presented a Staff Requirement in a letter dated 20th May 1948, seeking permission to proceed with the first of the T Class Conversion that were structurally quite different to the conversion of the Scotsman.

Remote here in New Zealand, it has been not possible find any references to the scientific data accumulated by the 'boffins' over the years of testing aboard Scotsman, but this was not considered a major disadvantage; it was always intended that this was to be the story of the conversion of the submarine and her later activities, manned by the men of the Royal Navy's Submarine Service.

Much of the Royal Navy submarine branch historical background in the early years of the Scotsman's service is detailed in the article on the Five Streamlined Submarines

This article on the Scotsman is part of a self-imposed task of determining and recording the electrical propulsion detail and background of the various Western submarine conversions to increase submerged speed carried out in the decade following the Second World War. The articles, all published on this web site, taken together, will provide the interested reader with a reasonably complete description of the electrical propulsion techniques and performances of diesel -electrical submarines of the Royal Navy and US Navy in this era.



The aim stated in the trial document was straightforward, a streamlined trials and experimental submarine that could achieve a speed of 17 knots (deep) to be maintained for 40 minutes. Fig 5.

The conversion of the Scotsman, a WWII Group III S Class submarine, was carried out at Chatham Dockyard commencing 8th April 1947, completing 8th July 1948. Presumably the design was the work of the office of the Director of Naval Construction, however it is notable that 1948 FOSM letters about Trials were minuted to Scotts Ltd, the original builder and a Scotts representative was to be present at the post conversion acceptance trials.

The main components involved in the conversion are shown in the attached text from the document recording the 1948 trials Fig 3. along with the hull dimensions and displacement of the conversion.


1/ The various modifications to the external hull, in particular the replacement of the saddle type ballast tanks with 'Under Slung' tanks. Figs 1a and 1b

2/ The drastic internal modifications, in particular the removal of the forward torpedo tubes and the two main diesel engines, Fig 1c that allowed :-

a/ The addition of two more batteries. There is no mention in the conversion trial documents of additional switching apparatus enabling the batteries to be connected in parallel for slower speeds or in series for higher speeds submerged. Fig 1a. However the trial results leave no doubt suitable switchgear was fitted.

b/ The replacement of the electric motors with more robust Amphion Class units to cope with the increased power.

c/ The installation of a diesel-generator set of the type normally fitted in pairs on the small Royal Navy U Class submarine.


The Batteries

There have been suggestions that the battery cells in the Scotsman were US sourced-this only has credibility if Exide USA was a major battery cell source for Royal Navy submarines during WWII and continued to be so post war?. The Trials Report to the Flag Officer Submarines in 1944 regarding the streamlined Seraph, Fig 6, tell us that the original DP cells of 4750 Ampere Hours (at the 5 hour rate) were replaced with Exide extra high capacity cells of 5350 Ampere Hours. A similar report for the Scotsman in 1948, Fig 5, makes no mention of a cell type and 5350 Ampere Hours assumed in this article supported by the following background.

It almost certain that the T Class submarine of the period used the same cell as the S Class but with three batteries of 112 cells instead of the two batteries of the S Class. In the immediate post war period T Class were reported as using 5350 Ampere Hour cells. The later Amphion Class had quite a different cell with four terminals per pole instead of the three per pole of the S Class and T Class.

All these S Class and T Class cells were of necessity, the same physical size to fit in the existing battery tanks. The same would apply to the Scotsman.

The drawing held in the NMM, clearly shows that the 5350 Ampere Hour cell was fitted in Scotsman in 1954, but raises the minor question as to why a cell drawing dated 1954 was required -had the cell type had been changed at that time ? Unlikely !

Overall, the probability is that the 5350 Ampere Hour cell, available in 1944 for the Seraph, was used in the Scotsman in 1948.

Information from the National Maritime Museum confirmed the following detail in a Scotsman drawing - General Arrangement. Of cell. Type D5350, dated 1954

There are three sets of connecting terminals at the top of the cell.


ACID 1.270/80 Sp.G. 60 degrees F

Rate Amp Hrs F.V
1 hr32001.60
5 hr53501.71
10 hr61701.75
20 hr68401.77
60 hr72601.80

At the highest speeds the maximum discharge current was in excess of the 3200 amps at the 1 hr rate stated above but as a rough guide, cells of this era could usually deliver current at the ½ Hr rate equal to the numerical value of the Ampere Hours at the five hour rate - in this case something approaching 5350 amps. Another rough rule is that the current at the ½ Hr rate is 50% more than the current at the 1 hr rate.

It should be noted that at this time, cell technology was available to increase the 5350 Ampere Hour capacity by 20 to 30% using the same cell casing albeit with a shorter life, though all the indications are that this was not the case with the Scotsman's batteries. Such cells were available to meet the basic design needs of the Taciturn conversion, 6560 Ampere Hour.

To summarize - there would no difficulty in finding cells of the same physical dimensions that could meet the short term demands of the Scotsman at high speed. But regardless the any cells would be near the maximum short term state of discharge, regularly being recycled from the fully charged to near fully discharged state See later charging comments on the rate of usage of distilled water and gassing at these heavy currents.

The Amphion Class Motors

The selection of Amphion Class motors

At first glance the replacement of the original S Class motors with Amphion Class seems to be something of a mystery when the nominal ratings are compared - 650 shp as opposed to 625 shp. However a closer look reveals that the Amphion Class motor was more mechanically robust having to directly transmit the mechanical power of the Amphion Class engines rated at 2150 bhp, through the thrust blocks, to the tail shafts.. Physically bigger and weighing 40% more than the original S Class motors. The engine power to be directly transmitted through the S Class motors to the thrust blocks in the S Class was quite modest at 850 bhp per shaft.

That the Amphion Class motor was capable of having its nominal supply voltage doubled in this conversion, is not surprising when it is considered that these motors in Amphion Class submarines used as battery charging generators, reached voltages in the order of 325 volts in the final stages of a charge.

The original T Class motors used in the T Class Conversion were strengthened for the higher speeds (BR1965).

It is reasonable to assume the Scotsman's Amphion Class motors were strengthened in a similar manner. A relatively modest treatment of the armatures.

No specification detail is readily available for the Amphion Class motor but a rather blurred Royal Navy Submarine Museum brochure picture shows the main motor armature ammeters go into the red at 1400 amps, a conservative observation. Thus a total tandem motor amps of 2800 amps (per shaft).

Taking 625 shp as the rated shp for a tandem motor (per shaft) from various published secondary sources and making some simple calculations gives the following-

Note. amps x volts = watts. 746 watts = one horse power. The difference between the electrical input to the motor and the mechanical output due to internal losses is defined as watts out /watts in. Typically a figure in the range of 0.89 to 0.95. From other similar motors a figure of 0.92 is used here.

(625 x 746) / 1000 = 466.25 kW mechanical output. 466.25 / 0.92 = 506.79 kW electrical input.

(506.79 x 1000) / 2800 gives supply voltage of 181 volts - not a sensible result.

200 volts is a more realistic figure (2800 amps x 200 volts x 0.92 x) / 746 = 690.6 shp.

As it happens the 'Particulars of Vessels 1959' gives 1382 shp (691 shp per motor) for the Amphion just prior to being streamlined, at 8.12 knots in trials with a clean hull. For reasons that are not clear it also gives 1250 shp (625 shp per motor) at 7.5 knots estimated with a clean hull.

The P of V 1959 detail for the Astute gives 1600 shp (800 hp per motor) at 10 knots - estimated with a clean hull. Though not stated, this data almost certainly applies to the performance after the modernization of the Astute that mainly involved streamlining with no major changes to the electrical propulsion apart from increasing the capacity of the battery by about 25 % and as with earlier Seraph conversion, the motors have been up-rated without significant alteration, Fig 4. The nominal voltage applied to the motors would remain the same. Generally similar to the earlier, modest modernization of the Five T Class.

Taking this figure of 1600 shp with twice the original voltage as applied in the Scotsman and we have a nominal 3200 shp. Close to the nominal figure of 3600 shp in the trial document, Fig 3.

Trial data is shown here to give some idea of the considerable overloads applied to the Amphion Class motors in the Scotsman - a maximum figure of 4527 amps for a tandem motor for 45 minutes, an at least 50 % armature current overload, but apparently sustainable for relatively short periods

For comparison, a similar figure for a single tandem motor of the converted T Class at full speed, was 3880 amps having risen from 3200 amps as the battery voltage dropped over a 20 minute period. The converted T Class had four such motors.

The above, taken as a whole, explains why the available Amphion Class motors were thought suitable for the high speed conversion of the Scotsman and for this article it was not felt necessary to pursue the matter any further by seeking more direct technical information about the motors.

However here are some incidentals that may be of interest. The nominal shp of the smaller T Class submarine was 725 shp and the motors weighed 34 tons with coolers against the 37 tons of the Amphion Class. (see below for S Class weight).

Information in BR 3043 shows the dependence on forced cooling of the S Class motors, with a considerably reduced continuous rating without cooling.

Extract from BR 3043 - ' In Swordfish the two main motors developed a total of 1300 bhp at 380 rev/min at continuous rating. They were also guaranteed for 1440 bhp for 1 hour. Working voltage 190.

The Shark and later vessels had tandem motors. The normal power output and revolutions remain as in Swordfish but the tandem motors were 'guaranteed' to give 1600 bhp at 410 rpm for 1 hour. They were also 'guaranteed' to give a total of 800 bhp continuous with coolers and fans stopped. The weight of the motors per shaft increased from an average of 10.75 tons to 13.25 tons in the Shark.

This figure of 1600 shp became of significance in the Seraph conversion discussed later.

Motor dimensional information

The 'Submarine Alliance' book by Lambert and Hill gives the Amphion Class dimension between the tail shaft centres as 6 feet 6 inches. The screw diameter was 5 feet 9 inches. The small scale drawings indicate that the motor body diameter was about same dimension as the screw.

The small scale drawing of the Group III Subtle (1953) supplied by John Lambert shows the screw diameter stated in text as 5 feet 6 inches. The diameter of the motors was just slightly less than this. By measurement the distance between the tail shaft centre lines was 6 feet 5 inches.

Getting the Amphion Class motors into the S Class hull would have been a tight fit and it is reasonable to suppose the motors were moved forward away from the stern pressure hull taper.

On the face of it, this would not be a problem as the engines were previously well forward with the power transmission shaft supported by the bearings of the motor in the original submarine. Pedestal bearings could have been fitted to support the shaft between the motor and the thrust bearings that apparently stayed in same position, with only the thrust blocks replaced with Amphion Class blocks with the S Class tail shafts retained and apparently with the original centres.

There are unsubstantiated reports that one motor was placed further forward than the other. There is no indication if the trim was compensated in this condition of imbalance.


Paxman's 6RXS was specially developed for service in submarines, the fabricated (welded) steel frame being better than a cast one for withstanding the shock of underwater explosions. It produced 400 bhp at 825 rpm and was coupled to a 275 kW generator by a Wellman-Bibby flexible coupling. The engines were made in pairs, left and right handed, so that all controls were between the two engines.

Richard Carr's excellent PAXMAN historical web site gives detail of the engines used in U Class and S Class submarines


Using the detail in the following text, the detailed drawings in 'The Submarine Alliance ' by Lambert and Hill and other sources, two diagramsFig 2a and Fig 2b have been prepared, that taking all the known detail and probabilities listed below, give a sensible, if somewhat speculative picture of the electrical propulsion system of the converted Scotsman and how it functioned.. It will be appreciated that in Fig 2b, most connection items shown will, in practice, have been duplicated, negative and positive.

The basic principles involved in the motor control of diesel-electrical submarines of the era can be found in the diagrams of the T Class Conversion article.

Motor Control

Amphion Class Switchboards

As there no doubt Amphion Class motors were fitted in the converted Scotsman, it is reasonable to assume that Amphion Class Switchboards were also available due to the post war cancellations of a significant number of this class of submarine and used in the Scotsman. It is also reasonable to assume that the Amphion Class link and port/starboard inter-connecting bus bar system that appears to have been fabricated as part of the switchboard contract was also used in the Scotsman. The same applies to surplus Amphion Class Battery Panels, likely available to fill the need created by the installation of the extra Batteries. This is relevant to the suggested forward connection for shore (S/m to S/m) charging. Fig 2b.

Chief Electrician Bill Smith, Scotsman circa 1954, who at that time had recently served as a young man on the Auriga, confirms that Amphion Class switchboards were in fact used in the conversion. This makes technical sense as these switch boards though basically similar to the original S Class type, were of more modern construction with greater capability to handle the increased voltage and armature currents. They also had the virtue of being of a pattern familiar to the Royal Navy submarine electrical ratings of the time. These were the last open submarine switchboards built for the Royal Navy. They were entirely constructed using large multiple blade knife switches, manually operated. (Fig 4) While quite different in outward appearance to the cubicle enclosed equipment seen in later submarines such as the conversion of the Taciturn, the basic principles remained the same.

Side Separation - Port/Starboard.

The first of eight T Class submarines - Taciturn entered the T Class Conversion programme in 1948 as the Scotsman was being commissioned and as already suggested, they likely shared a similar system design philosophy.

From BR1965 it is known the Taciturn electrical propulsion system was completely separated into port and starboard, each side with its own pair of batteries. In emergency there was a link system that allowed the switchboards to be supplied from either the Port or Starboard battery but under no circumstances did it allow the two pairs of batteries to be interconnected, port to starboard. The purpose of this strict isolation was stated to be the limiting of the maximum possible short circuit current and applied equally to the Scotsman.

The Scotsman tabulated trial data strongly suggests that its batteries and motors were also separated into port and starboard. (Battery voltage and battery current tabulation.)

The concept of side separation in the Scotsman is supported by FOSM 7th July 1948, amending an earlier letter setting out the range of trial rpm, where 'shafts in series ' was designated the lowest speed condition, but this would have involved switchboard interconnection as in the Amphion Class. The amendment replaced this item with '120 rpm. One shaft'. This amendment is reflected in the slow speed trial results that also indicate side separation.

A notation on the Scotsman trial document about supplying the Auxiliary Load from either Port or Starboard further supports side separation. The notes are reproduced in AUXILIARY LOAD below, but reliability is slightly diminished by an obvious data tabulation error.

The new twin shaft Porpoise Class (belatedly commissioned 1958), is reported to have been in the preliminary stages of design about the same time as the T Class Conversion was on the drawing boards circa 1950-51 and could have been in the minds of the designers as early as 1946, but with this new submarine they were not inhibited by the limitations of converting existing submarines and could halve the battery currents of the 6000 shp converted T Class simply by using a higher maximum battery voltage. This maximum battery of 880 volts at high speed required 448 cells in series arranged in two batteries. Such an arrangement could not be separately sided as could the T Class Conversion and the Scotsman, each with 448 cells in four 112 cell batteries arranged in two separate pairs. Each pair to give a maximum battery voltage of 440 volts per side, with 224 cells in series for high speed. It can be safely assumed that early design thoughts about the Porpoise Class would have had no influence on the Scotsman

Battery Grouping Switches

As suggested earlier, the basic design principles of the converted Taciturn were likely applied in the Scotsman with each separated pair of batteries capable of being connected in series or in a parallel. to increase the submerged speed.

However Amphion Class switchboards had no Battery Series/Parallel Grouping switches as fitted in the converted Taciturn.

On the Scotsman, the abandonment of the Amphion Class submarine 'creep' speed feature would have made redundant a single pole change- over switch on each of the switchboards, port and starboard. It is possible but unlikely that with additional blades and mechanisms, these switches could have been used for the new battery grouping function.

New purpose built cubicles, would seem to be a better approach to marshal and connect all the heavy cables coming aft from the pairs of batteries - it should noted that there would likely be a minimum of three individual cables per battery pole, thus 12 cables to terminate on each side, if not more. I has been assumed that in the Scotsman, these units were provided in separate cubicles Fig 3> adjacent to the switchboards, and from the above - one for port and one for starboard. Fig 2a and Fig 2b

Diesel Generator Connection

It is not known if the single small Diesel-Generator was intended to be connected to either Port or Starboard or just one side propelling, but the Amphion Class had a system of links that normally joined the Port and Starboard switchboards in the preserved Alliance and her sisters. For surface passage, this system fitted to the Scotsman, could have been connected the D-G to either side or both with one pair of batteries isolated. (Fig 2b).

Cliff Alexander 1956, recalls being in the Lochs with Scotsman charging her own batteries, this may imply the ability to connect the D/G set to either port or starboard as required. But it would not necessarily be a full charge, merely maintaining auxiliary services using only the starboard battery, we don't know.

Chief ERA Toms 1954, relating the usual practice in his time aboard (see full anecdote)

The Main Motors were 'A ' boat motors and our 'Donk' was a single 'U' class (wartime small boat one), when running on the surface with the engine, we ran on one screw and barely made 8 knots. The diesel was not connected to a propeller, it's function was to just keep the batteries topped up.

While Albert Burchnall 1948 recalls both screws being used on passage. (see full anecdote)

The proposed system in Fig 2a allows for both options. Various engineering officers over the years, may have favoured one or the other in any given period of service.

Note. Conventional direct drive U-Boats in WWII., according to author Clay Blair, used one engine to drive a screw and a motor as a generator supplying power to the motor driving the other shaft. This was considered an efficient fuel saving method of cruise propulsion. The Amphion Class direct drive propulsion diagram gives an idea how this cruising practice might have been achieved in a U-Boat, Fig 2b

Chief Electrician Smith advised that the single Diesel-Generator was fitted amidships and that generator output was fed through a Reverse Current Breaker. This would have been prudent design given the substantial battery capacity. RCBs may in fact, have been a standard fit in the U Class submarine?

Battery Inter-Connections and Charging

The previous section concluded that the four batteries were connected in sided pairs, each with a simple but substantial Battery Grouper Switch Fig 3, to enable series/parallel connection and the assumption made that the Amphion Class switchboard linking system was fitted to Scotsman. Fig 2b

In the Scotsman, the existing batteries, designated No 2 and No 3, would likely have retained the existing S Class isolating/fuse facilities and the new No 1 battery in the fore ends would have had a similar isolating panel installed. A complication is the splitting of the No 4 battery with half its cells far forward in the former tube space and the rest aft in the engine room. To be consistent with the DNC design practice, each of the two sections of No 4 battery would each have had a local isolation panel. Fig 2b suggests a possible battery inter-connection and charging scheme.

Forward Shore Charging Connection.

More from 1957 crew member Cliff Alexander in a telephone conversation, he clearly recalled there was a large switchboard cubicle in the fore ends. This switchboard was protected by wooden doors and Cliff also clearly remembers an electrician connecting charging cables to this switchboard. The cables came down the submarine through the forward hatch. Fig 1c

As discussed in the previous Control Section, it is probable that the switchboard that Cliff remembers was a surplus Amphion Class Battery Panel with its shore charging terminals being used to connect to the charging source through the forward hatch. Fig 2b.

The Amphion Class submarine had two of these Battery Panels, one located forward for No1 battery and one amidships for No 2 battery. These panels adjacent to their associated battery, basically provided a means of isolating the battery in an emergency. The isolating facility was a link made up of a fuse - one for negative, one for positive. The link had an insulated operating handle and when in place was clamped by two vice-like terminals closed by insulated handles. In the closed position, the fuse was adjacent to a magnetic 'blow-out ' coil that was magnetized by the battery fault current. Quite a neat system. Shown in principle in Fig 2b.

In addition they had fuses and knife switches providing emergency supplies to the Variable Pressure and Constant Pressure ring mains, There was also provision to supply 'Police Lights'.

Of particular interest in regard to the Scotsman, was the provision of large terminals to allow the connection of heavy flexible cables to enable shore charging of the individual Amphion Class batteries.

These terminals were rarely used in normal Amphion Class service, though in 1971, the Artemis sank alongside due to loss of a stable trim while refuelling allowing sea water to flood through the open engine room hatch that was unable to be closed because of shore supply cables passing through. Apparently the consequent inquiry deemed the accident happened

because too many people had forgotten basic principles of submarine safety - ship stability'.

The many people who manned the Scotsman over the years she was in service, did not forget!

Aft Shore Charging Shore Connection.

Cliff also clearly recalled that cables came down the hatch in the after ends where the stokers messed, passing through the water tight door into the motor room. He recalls an accidental restoration of charging supply causing the unconnected cable ends to short on the steel deck, the heavy current making the cable leap about. There were burn marks on the steel deck plate. Not an event easily forgotten.

In the Amphion Class motor room, there were special links that could be used to replace a normal link, shown in Fig 2a. These special links had two large threaded studs for the attachment of cables for shore supply. Circa 1950, on Amphion Class submarines they were referred to as the Scotsman charging links and were simply stowed away unused. No anecdotes have been forthcoming about connection detail in submarines assigned to charging the Scotsman, but the special links were likely the aft terminating point in the charging submarine for the cables from the Scotsman as shown in. Fig 2b.

The general understanding some 50 or more years ago was that these links were not provided in the Amphion Class 'as-built' but supplied later, specifically for the charging the Scotsman, however this has not been confirmed and in retrospect seems un likely. The links were probably part of the switchboard kit for emergency use. Something similar was no doubt provided on the T Class and S Class charging the Scotsman but no switch board details are available.

Regardless, the shore supply connections in the battery panels and the special switchboard links certainly gave a number of options for connecting the outgoing cables to the Scotsman.

Aboard converted Scotsman, given that Amphion Class switch boards and links system were installed, the cables coming down the after hatch, observed by Cliff, would have been connected to the special charging link with the threaded studs. Fig 2a and Fig 2b.

Albert Burchnall, 1951, clearly recalls the charging cables coming down the Scotsman's engine room hatch. However the simple hull outline sketch Fig 1c, that is part of the 1948 trials document shows the engine room hatch removed, but the accompanying overhead photograph shows an aperture in the casing behind the conning tower suggesting the hatch was still there and perhaps the drawing has an error of omission ? All quite confusing, but with no effect on the principles involved in charging the Scotsman from an outside source.

Internal Battery Cable Symmetry

Technically minded readers will note the lack of the internal inter-connecting cable symmetry with the possibility of un-equal sharing of charging current in parallel battery pairs due the differences in cable resistance.

This apparent problem must face all submarine design electrical engineers, but detail is not readily available to enable sensible discussion. It is interesting to note that on an Amphion Class submarine, the battery cables from the No 1 forward battery to the main switchboard aft, were about twice the length of those of the No 2 aft battery. Both sets of battery cables were paralleled permanently at the motor room switch boards. Similarly in the unconverted T Class with three batteries, without any recalled current sharing problems.

In modern submarines large motor propulsion powers seemed to be achieved by raising the supply voltage rather than increasing battery currents.

Charging in general

'6.(c). HMS Scotsman can only operate for 3 days a week'.

'6.(d) HMS Scotsman will require about approximately 3 tons of distilled water each fortnight'.

These comments from FOSM letter 14th March 1951, give some idea of the demands on the batteries of these repetitive heavy, high speed discharge/charge currents. Topping up up 448 cells would have been really hard work. Usual practice was to also test and record the SG of each cell prior to topping up.

Hydrogen explosions while charging, must been an ever present risk in this relatively small hull literally packed with batteries. Cliff Alexander recalled two large fans and trunking overhead in the cramped fore ends. He believes they were there to provide the increased need for battery ventilation

From FOSM letter 15 th September 1948, the first charging submarine was probably an Amphion Class quickly followed by the Tally-Ho and there was a spare set of leads that was transported by land as required (FOSM's letter). Albert Birchnall recalls Tally-Ho as the charging submarine most often used. The Astute was assigned in FOSM letter 2 May 1951.

The Tradewind was assigned in the summer of 1952. A series of Amphion Class were employed in later years-1954. Apparently the charging submarine retained the leads when not in use.

Chief ERA TOMS, comments on charging submarines in his anecdotes.

Cliff Alexander confirmed that in his time, the Scotsman, when alongside the depot ship at Rothesay, took its charging supply from that ship. Also that there were occasions up the Lochs where the Scotsman's small diesel -generator were used for charging the batteries. As already discussed in the D/G section, this may not have been a full charge.

A simple comparison is appropriate at this point, the maximum continuous output amps of the Amphion Class was limited by the rating of the motors as generators:

about 5000 amps compared to the 1170 amps of the U Class diesel-generator in the converted Scotsman Diesel generator.

BR 1965 gives the maximum continuous output current. the T Class motors as generators, 5200 amps at 220/270 volts. 3880 amps at 324 volts.

Note the relevant extracts on charging in the FOSM letters listed later in this article.

In the later years of the Scotsman's service, circa 1957/1959, the Solent was used for charging with a special flat decked barge separating the two boats.

Chief Electrician Smith. (see the attached anecdotes)

Operational Note.

It has already been stated that BR1965, re' the Taciturn, makes it very clear that under no circumstances should the port and starboard battery pairs should ever be placed in parallel. As has been discussed, the same battery isolation policy was likely carried out in the Scotsman. Consequently the same rules would have applied to the battery pair in the companion charging submarine. Some skilful switching would be required to avoid any pair of batteries being connected in parallel, but it could be done. However the Amphion Class link system did not have the built-in safety arrangement of a limited number of links, found in the Taciturn and her sisters.

Very heavy current sources were involved in all the activities of connecting /disconnecting the Scotsman from its charging source, requiring a good level of skill and discipline that had to be maintained almost daily from 1948 for over a decade.


Submarines of the era of the S Class T Class and Amphion Class had a machine called a REDUCER to maintain the Constant Pressure ring main at about 220 volt while the batteries were charging and could reach voltages up to 325 volts. The Reducer was a form of motor-generator with the motor connected across the battery supply. The generator armature was placed in series between the battery supply and the CP ring main. The voltage output was of such a polarity as to oppose the high charging battery voltage reducing the output to the CP ring main to about 220 volt, manually adjusted by the Motor Room watch keeper as the charging voltage gradually rose as the charge progressed. When not charging the Reducer could be shut down and the CP Ring Main supplied directly from the battery. The Reducer could also be used as a stand-alone MG set to charge a single sick cell at about 2 volts.

The Variable Pressure ring main was supplied by the battery and all the auxiliary machines supplied were designed to operate over a wide voltage range from less than 200 volts up to 325 volts.

The battery panel located near each battery could supply the ring mains in emergency.

Later submarines such as the converted T Class submarine simply had straight forward motor generators, with the motors supplied from the battery and the auto controlled generators directly supplying the CP ring main. The converted T Class had two such MG sets, one supplied from the Port side and one Starboard side. The CP ring main could be supplied directly from the battery if required.

The Scotsman fitted with Amphion Class switch boards may simply have retained the S Class Reducer as the Auxiliary Load was not likely to be more than the original submarine. The controls and switches for this system were located on the after end of the starboard switchboard Fig 4 and in the Amphion Class submarine was supplied through the main linking bus bar system as shown in Fig 2a.

In the Scotsman with the option of having the switch boards supplied with a nominal 440 volt battery supply when two batteries were in series for high speed, the Auxiliary supply would have come from one battery directly in a manner similar to that shown in Fig 2a, supplying a nominal 220 volts.

The submarine would spend most of its time with the batteries in parallel at slower speeds or stopped, thus the periods when one battery of a pair was supplying the Auxiliary Load was relatively short and of little consequence in terms of load sharing.

In the Amphion Class submarine the shunt fields of the two motors were supplied at 220 volts from the switchboard battery bus, but in the Scotsman an arrangement would have been made to supply the fields of one side from a single battery of that same side, in similar manner to the Auxiliary Load. But there would be no requirement for a side change-over arrangement of the field supply.

Trial Document Notation and Contrary Data

With the submarine electrical propulsion system split into port and starboard plus a notation in the trial document detailed below, we could safely assume the Auxiliary Load could only be supplied for either the port or starboard side, not both together. A possible arrangement is shown inFig 2b. The Auxiliary Change Over Switch, if it existed, would likely be housed in one of the new Battery Grouper (series/parallel) cubicles. Fig 3.

Unfortunately what would otherwise been a good indication as to the electrical lay-out is, is rendered unreliable by an obvious error as follows;

The tabulated numerical test data shows clearly that in the three supply conditions shown below, only the port motor was propelling at the same speed and power with no current drawn by the starboard motor, fields and fans. The only noted difference between a), b) and c) being the endurance, that is battery capacity.

The Notation

Note (a) Starboard shaft propelling and auxiliary load supplied from the starboard side (Nos 1 & 2 batteries) (endurance 156 miles)

(b) Port shaft propelling (Nos 3 &4 batteries) and auxiliary load supplied from the starboard side (Nos 1&2 batteries) (endurance 245 miles)

(c) Propelling and auxiliary load supplied firstly from starboard side (No 1&2 batteries) until battery is discharged then completely transferred to port side.

(Nos 3 &4 batteries) (endurance 312 miles).

I am inclined to believe the motor data was incorrectly tabulated and the submarine was first running on the starboard motor (a) then on the port motor (b) and (c).

In all three conditions the motor current was 185 amps, motor field plus fans 32 amps with the auxiliary load at 120 amps. All at a constant speed of 3.4 knots. The bracketed data in red has been added into the notation for ease of understanding.

This is a good example of the factors involved in submarine slow speed endurance and worthy of the extra text.


The tabulated trials show that at periscope depth over Loch Long Course the maximum recorded speed was 15.29 knots with an endurance of 0.74 hours.

The total shp was 3896, at mean rpm of 529.5.

The port motor current was 4221 amps at 373 volts.

The starboard motor current was 4450 amps at 360 volts.

Over the Electric Mile (sensor coils etc) Kilbrennan Sound at 50 feet, the maximum recorded speed was 16.33 knots with an endurance of 1.07 hours.

The total shp was 3241, at a mean rpm of 500.

The port motor current was 3472 amps at 381.5 volts.

The starboard motor current was 3434 amps at 373.5 volts.

A graph from the trials document shows that over 17 knots was apparently achieved at 530 rpm at 50/90 feet. (Fig 7). The graph data is as in the trial documents but with the scales redrawn for clarity and three shp values have been added.

The further performance information that follows was extracted from data provided by Ian Buxton. The original document is archived at the PRO/TNA, Kew. UK

The table records several speeds, both surfaced and submerged but for the purpose of this article, only the highest recorded speed submerged is shown-

The full detail of the particular propeller used is also shown in full

2.11.56 90-ft. Depth. 16.34 knots, 499.5 rpm. 3,625 shp, 19.76 tons of thrust.

Trial Records - HM Submarine Scotsman - Set of D Propellers.

Number of Blades = 3.

Diameter = 5ft. 4 in.

Pitch at 0.7 radius = 5ft. 0.67 in.

Developed Blade Area = 12.25 sq/ft.

Blade Ratio Area =0.55.

Blade Thickness Ratio = 0.06.

Blade Section = Elliptic Parabolic.

Propeller Drawing = A.E.W 14123

Speeds have been faired. Thrusts have been corrected for hydrostatic pressure.

Trial course - Arran and Kilbrennan.

Depth 50-80 fathoms.

Originally Stamped SECRET then RESTRICTED

This 1956 figure of 16.34 knots indicates that the alterations in shape from the rather odd looking 1948 version to the rather smart 1952 shape complete with fin, do not appear to have changed the maximum submerged speed performance first recorded in 1948.

Note. The term faired is associated with the graphic plotting of speeds using several points.


This well-known WWII submarine was streamlined for higher underwater speeds in 1944, with six of her sisters to follow. It would be unreasonable to believe that the office of the Director of Naval Construction was not seriously influenced by the high submerged speed experience obtained with the Seraph in the two years until conversion of the Scotsman commenced in 1946.

The 1944 trial document description of the streamlining of the Seraph is attached to this article. Fig 6.

It is interesting to note that at trial speeds of about 12.5 knots, both submarines had a similar performance. The Seraph retained the original S Class ballast tanks. However at this speed the Scotsman had considerably more endurance due to her large battery capacity.

1944 Streamlined Seraph 12.523 mean knots. 410.7 rpm. 1647shp. 192.5 volts.

1948 Converted Scotsman 12.69 mean knots. 400 rpm. 1678shp. 208.5 volts. (Note - the batteries were all in parallel )

The reader might reasonably ask if the changing of the ballast tanks on the Scotsman actually assisted in the achievement of the higher speeds? However there are perhaps other expert factors to consider such as the wake effect towards the stern when clearly the intention was to trial various screws and the NIGHTSHIRT apparatus, with apparent emphasize on submerged high speed 'noise ' testing and reduction.


Photographs Fig 8

During her service as a trials and experimental submarine, the Scotsman had a number of distinctive upper structure shapes. The most marked was her first conversion 1948, from a standard Group III S Class submarine of WW2, where a significant portion of her fore casing was removed and the conning tower reduced to a streamlined minimum.. Photographs show a canvas wind cheater in use on the surface. Fig 1b shows the induction tube provided as described in the original trials text Fig 5, for running on the surface in bad weather with the upper conning hatch closed. Photographs of this original conversion shape are on the web and in submarine publications.

In 1950 the fore casing was restored along with the fitting of a semi-enclosed cab-like bridge after barely eighteen months in service. This bridge was stepped towards the stern, it is not known if the induction tube was removed. The 'windows' give the fore part of this new bridge, a look vaguely similar to Soviet submarines It can only be assumed that experience and further research determined that the relatively large plane area formed by the forward casing, would in fact not be a problem at submerged high speed.

Post refit 30th June 1952, the submarine was fitted with a modern style fin, but cab windows retained. Other dates for this change, up to 1955 have been suggested but the clear statement by Roger Fry that she was in Falmouth with this shape in 1952, aligns with FOSM correspondence stating she was in Falmouth, in the immediate post refit period. Several photographs with this shape are on the web.

The speed data in the table in PERFORMANCE indicate these changes did not result in any significant loss in submerged high speed. Web photographs of this, now smart looking submarine, are rare.

In 1960, post refit. a new, rounder upper bow was fitted, quite different from the typical S Class 'notched ' bow the Scotsman had retained until this point. The trial purpose of this new bow is not known. The only new class of diesel -electric submarine was the 'Unclasps that appeared with quite a different bow. The rare photograph of this change was supplied by Roger Fry.


It can be stated that the technical aspects of this article have established that the Scotsman electrical propulsion conversion was carried out to allow the original battery voltage supplied to the newly fitted Amphion Class motors, to be doubled in value as required. This increased the maximum propulsion power that together with extensive streamlining achieved the desired high submerged speed. (Fig 5). The submarine was equipped to readily receive charging supplies from a depot ship or a companion submarine. Fig 2b The specific need for this high submerged speed experimental and trials submarine in 1945, over twice that of a front line Amphion Class submarine of the time, can reasonably be deduced from the following collected FOSM letter extracts and crew anecdotes.

The two references to ship's visits early in her service (Poole Quay and Bristol) indicate that the Scotsman itself had nothing to hide, only the documented results of the various trials

It has not been possible to obtain a copy of the Draft Staff Requirements 1946 or similar documents prepared to justify the expenditure of scarce submarine money on the conversion of the Scotsman, that by its design would generally have the additional overhead of a charging submarine, and in itself, have no value as an operational submarine.

In the streamliningT Class article there is a reference that might have some bearing on the origin of the Scotsman conversion as no other project of this sort emerged.- FOSM to the Admiralty dated 19th January 1945 (A1944/12) included this sentence;

Approval is further requested for the construction of an intermediate design of hull form with which experiment and development can be undertaken.

Fortunately a number of former crew members have stretched their memories and provided anecdotes and George Malcolmson RNSM, has kindly provided copies of letters from the FOSM from 1948 to 1953, from which have been taken extracts to give some idea of the purpose of the converted Scotsman. There is a gap mid 1949 to mid 1950, but for a general picture of Scotsman's activities the letters are quite adequate, with one proviso - the annual programmes are complicated by several letters partially amending the programme in the previous letter but hopefully the final annual programmes are correctly presented.

In the FOSM letters, there is mention of an apparently important trials item code named CANDID. The nature of these trials is unknown but in the period 17th May to 23rd May 1951, it required the transfer of an American underwater telephone from HMS Auriga. Apparently the Director of Torpedo, Anti-Submarine and Mine Warfare was the initiating authority of CANDID

FOSM letter 5th July 1948 details a series of routine acceptance trials, working up in the Third Submarine Flotilla, First of Class Trials (FOSM requested the assistance of Scotts of Greenock - the original builders), Automatic hydro plane trials and noise trials. FOSM then details the First of Class Trails that were largely carried out in September-October 1948 and reported to FOSM in a document date stamped 27 May 1949.


The 'copies list' is impressive and more extensive than similar letters referring to the Taciturn.

Captain (S/m) Fifth Submarine Flotilla.
Captain (D), Sixth Destroyer Flotilla
Director of Naval Equipment
Director of Naval Construction
Director of Naval Engineering
Director of Underwater Weapons.
Superintendent, Admiralty Experimental Works, Haslar.
Principal Ship's Overseer c/of Messers. Scotts' S & E Co Ltd.
Director of Torpedo, Anti-Submarine and Mine warfare.
Captain HM Underwater Detection Establishment

'The attached tentative programme of trials and exercises to be carried out by HM Submarine Scotsman during the first three months of 1949, is forwarded for your information '

'2. It is expected that two or three weeks will be required after the Easter leave period to complete trials of automatic hydroplane gear and that after this date the submarine will be available for trial required by Captain, HM Underwater Detection Establishment and Captain HMS VERNON as discussed at the meeting held by the Director of Underwater Weapons on 10 November 1948. '

A 1949 programme is detailed;

'18th January. Functioning trials with Automatic Hydroplane Gear off Portsmouth. HM Submarine Scotsman will sail to Rothesay on completion. '

'24th January - 14th February. 'Exercises with the Sixth Submarine Flotilla.'.

'16th February - 25th February. Docking for change in propellers, examination of underwater fittings, etc, in AFD 22. '

'28th February -1st March, Completion of noise trials at Loch Goil. '

'2nd March - 4th March. Acceleration and deceleration trials and completion of circle trials in lower Loch Long. Return to Rothesay on completion '

'8th March - 10th March. Reversing and endurance trials as required by Director of Electrical Engineering. '

'11th March - 14th. Installation of Automatic Recording Gear. '

'15th - Until commencement of the Easter leave period - Continuation of handling trials'.

Note. The missing letter(s) were from 15th March 1949 to 15th September 1950. During that period Scotsman was in the dockyard for a refit from 13th December 1949 until 23rd of May 1950. Emerged with a shape as in Fig 8.

A key missing letter is FOSM 8th March 1950 that apparently set out a programme amended by the next available letter - FOSM 15th September 1950.

'Item 2 (a). HMS Scotsman docks at Rothesay for fitting of First 'Nightshirt' Assembly, cleaning and coating of hull, inspection of propellers etc, period 27th September to 2nd October 1950. '

In regards to Albert's message below, it is important to appreciate there were First and Second versions of 'Nightshirt'. This will avoid the possible inference that the first ever fitting of 'Nightshirt' was later in 1950 than stated by Albert.

Albert Burchnall, Stoker Mechanic, assistant to the Outside ERA of the Scotsman - extract from his E-mail 28 January 2004;

We went back to Chatham in 1950, it must have been May time, because we were there when Truculent went down in the Medway.

The boat was fitted with Bronze Hollow Spider webs round each prop., and each was connected to the HP air system. The idea was to fill the void at the back of the props, and so reduce slap that it used to produce. This followed the same routine as the other trials. Up and down the Lochs at different depths and different speeds.

I forgot to say, that at the end of the diving each day, Being the outside ERAs mate it fell on me to charge the HP system back up to 4000 psi. That went down a bundle because the Weirs compressor was on the Stoker's mess deck!

On one of the runs, a high speed one at that, we were off course, and orders were given to surface at 30 degree bow up angle!!!. We caught the bottom with the starboard spiders web and buckled it quite badly. We went down to the torpedo station at the head of the Loch Long

Their divers disconnected it, loaded it on an open backed lorry, And the outside ERA Ken Blackshaw, and myself, (both of us on the back of the lorry). took it to Renfrew Airport to be shipped back to Dolphin.

At this time the Rest and be Thankful was a single track road with passing places, quite a bit scary travelling in the dead of night.

Anyway it came back and was fitted back in the floating dock at Bannatyne. After that it was plain sailing, and I left the boat in July. 1951


FOSM also stated - 'Item 2 (d) that the First 'Nightshirt' was removed in the dock at Rothesay approximately 13th November 1950'

An interesting FOSM snippet - 'Item 3. Captain, HM Underwater Detection Establishment representative stated that the Second 'Nightshirt' Assembly was to be delivered to dock in HM Dockyard, Portsmouth about 9th of October for welding and drilling. It is not anticipated that the work required could completed before December, 1950

'Item 4. It was decided that arrangements should be made to dock HMS Scotsman at Portsmouth during Christmas leave period for a trial fitting of the Second 'Nightshirt'.

(Other correspondence and anecdotes indicate the Scotsman always came down to Portsmouth for annual leave, despite her slow surface speed).

'Item 5. Immediately following the Christmas Leave period HMS Scotsman is required for trials with HMS SCORPION in the North Channel for the period 15th January, 1951 to 19th February 1951.' (Authors Note: Then a modern Weapons class destroyer engaged in ASW trials)

'Item 6. It was provisionally arranged that HMS Scotsman should dock at Rothesay 21st February 1951 (completion of SCORPION trials) for fitting of Second 'NIGHTSHIRT' etc Followed by Noise trials commencing Loch Goil 5th March, followed on completion by speed trials at Kilbrennan.

'Item 7. It was considered that the second series of 'NIGHTSHIRT' trials would need to be as exhaustive as the first series to enable a proper comparison to be made'.

Another point of general interest referring to 1950 - 'Item 8. HMS Tally-Ho is detailed to act as attendant submarine for HMS Scotsman for the period the trials 8 and 9, but is required to carry out other trials in the Londonderry area for the period 2nd to 8th October 1950 and hovering gear trials at Loch Goil during the period 10th to 13th October 1950.'

'Item 9. It was agreed that the trials of the hovering gear in HMS Tally-Ho, 10th -13th October 1950, should have priority over HMS Scotsman's trials for that period and should include a half day on the Sound Range.'

FOSM letter dated 14th March 1951, revising programme in 9th September 1950

'Easter leave at Portsmouth. 19th March to 22nd April 1951'.

'Trials with 173.X ASDIC at Portland. (Includes fitting gear at Portland) 23rd April to 16th May 1951'.

'Land 173.X and fit American underwater telephone from HMS Auriga for CANDID trials. 17th May to 23rd May 1951.'

Note by Author - On page 352 of Willem Hackmann's 'SEEK AND STRIKE ' published by HMSO as a history of Royal Navy ASDIC, he calls the 173 X set 'An American Underwater Communication Set'.

The following points were made in the 14th March 1950 letter, that were still relevant despite the amending letter that followed.

'6(b). An attendant submarine will be required, as before, for charging HMS Scotsman's batteries and arrangements should made for assisting HMS Scotsman in recharging her air bottles for 'NIGHTSHIRT''.

'6(c). HMS Scotsman can only operate for 3 days a week'.

'6(d). HMS Scotsman will require about approximately 3 tons of distilled water each fortnight'.

'6(e). Captain, HM Underwater Detection Establishment is requested to supervise the fitting and removal of the second set of 'NIGHTSHIRT' in the dry dock at Rothesay'.

'6(f). HMS Scotsman is to have a shallow water diver trained for the examination of the 'NIGHTSHIRT' assemblies as required etc.'

'6(g). The coils for measurement for underwater speed may be removed from HMS Taciturn prior to HMS Scotsman's trials at Loch Goil and Loch Fyne commencing 15th October 1951. This assumes HMS Taciturn will have finished her trials but in any case she must have priority over HMS Scotsman. Will Superintendent, Admiralty Research Laboratory please comment on this'.

Amending FOSM letter 2 May 1951

23rd May 1951 onwards

'Passage to Campbeltown via HMS MONTCLARE to disembark extra gear - 23rd to 28th May 1951. Captain (S/M) Second Submarine Flotilla to arrange transport of ½ charging cables to Campbeltown.'

'Exercises with Third Training Flotilla. 28th May - 9th June 1951'.

'Alongside at Londonderry. 9th -20th June 1951'

'Takes part in Phase 3 Summer Wars (an 'A' class submarines was required to charge HMS Scotsman at West Loch Tarbet.). 22nd to 28th of June 1951.' Authors Note - Isle of Jura. A good sheltered Western base for a submarine with limited range to enter the Atlantic.

'Post exercise conference Rothesay. 29th - 3rd July 1951'

'CANDID trial (based in Campbeltown with an Amphion Class submarine. 4th July -11th Aug 1951'.

'Passage to Portsmouth. 13th -15th August 1951'

'Merchant Convoy exercise. 26th September -7th October 1951'

Commence Trials of Second 'Nightshirt' assembly with Amphion Class submarine. 22 October 1951'

'Available fast ASW training 27nd November. 1951'

'Commence refit and fits viewing device. 15 December 1951'. (This was a glass port of some description to observe the screws).

This letter concludes item 2. 'A submarine to act as harbour charging unit for HMS Scotsman is to be provided by the Captain (S/M) Third Submarine Flotilla. At present, HMS Astute has been nominated for this duty but until the situation regarding Amphion Class submarines has been clarified by the Admiralty, this cannot be confirmed'.

Authors Note. It is assumed this is a consequence of the sad loss of the Affray in 16th April 1951

15th Dec 1951 to 10th July 1952-in refit. Emerged with shape as in Fig 8

The final available letter from FOSM is dated 8 th May 1952 - Headed HMS Scotsman TRIALS 1952-1953. New titles appears on the distribution list - Director of Physical Research and Range Trials Officer, Loch Goil.

The letter commences with - 'The proposed programme of HMS Scotsman for 1952-1953 is attached - It is based on the hope that the Scotsman will have completed her acceptance dive by 11th July 1952'

'10 th of July 1952. Arrives HMS Dolphin, Portsmouth from Chatham' Completion of refit that commenced in 15th December 1951.

A brief letter from FOSM 27th May 1952, 'Tradewind is to be made available to act as charging S/M for Scotsman during her work up at FALMOUTH from 21st to 26th July. Arrangements for getting the charging leads from PORTSMOUTH to FALMOUTH to be agreed between S/M 5 and SO S/Ms PORTLAND'

FOSM 8th letter content continued - A point of interest - 'The Noise Reduction Panel has been consulted in the drafting of this programme'.

And another '3. It will be noted that HMS Scotsman requires a charging submarine for most periods. The fact that two submarines will therefore be bound up for a very long period in technical trials has not yet been communicated to the Submarine Priorities Committee; it is hoped that these trials can eventually be given sufficient priority to be undertaken as proposed in the enclosure'.

A further points of interest 'Item 5 (b). The Engineer-in-Chief of the Fleet is to confirm that type J propellers will delivered to Rothesay in plenty of time.'

And 'Item 5(c) Director of Underwater Weapons, London to confirm that 'NIGHTSHIRT' will be ready during Easter Leave period 1953.'

Reiteration of earlier comments '6(b). HMS Scotsman has a passage speed of 6.5 knots and usually can only run 3 days a week when operating at high speeds.'

A letter with a revised programme was issued FOSM 12th September 1952 - this letter expressed concern that 'a considerable amount of information was available about the Scotsman fitted with normal type propellers whereas little is at hand about the wide bladed propellers. Moreover, it is considered that more material advantage will accrue to the Service generally by the early and decisive testing of these propellers than by the protracted trials of underwater photography, already projected as far as next Summer term, and at a time unfavourable to light conditions below the surface.'

The amended programme devoted 23rd -28th October 1952 to fitting wide blade propellers and 29th October to 5th December 1952 to testing wide bladed propellers on the KILBRENNAN measured mile and endurance trials, concurrently carrying out underwater camera trials at Loch Goil

Earlier it is was clear Scotsman has now been fitted with underwater camera facilities that would have to be trialed with scientists. The underwater camera fitting seems to have been something like a Signal Grenade Ejector with a hull valve and an internal loading valve. Apparently the camera was exposed to the sea pressure and the fitting of 'NIGHTSHIRT' involved the blanking of the underwater camera ports.

'NIGHTSHIRT' continued to be prominent in programming.

Mid February to end of March 1953 - 6 weeks. 'Available for SSX and Fast A/S training - leave Type J propellers and 'NIGHTSHIRT' on'

This is the last of the available correspondence.


Norman Friedman to his book 'THE POST WAR REVOLUTION' in Appendix I, shows the 'STAFF REQUIREMENTS FOR THE MODERNISATION OF THE FLEET, 1948. Listed is the intended fleet upgrading. An unexplained item amongst other items such as new ASDIC etc for all destroyers and frigates, is NIGHTSHIRT.

The US Navy pursued the goal of reduced noise using similar methods with a system called Prairie Masker.

NIGHTSHIRT was fitted to CAPTAIN class frigates for trials in 1945 to reduce propeller noise. Later it was also fitted to a number of other Royal Navy escorts and destroyers in the early post war period.

Despite all the testing by the Scotsman, there is no evidence that an Royal Navy operational submarine was fitted with this kit.


Stoker Mechanic Albert Burchnall - Scotsman 1948 to 1951

  1. A little bit more about Scotsman. With all the dockyard trials over we had our first visit to the Lochs. We lived on board except weekend at Rothesay tied up to Montclare. At least we got some decent runs ashore. Our first support was one of the A boats, but I cant remember the name. Scotsman didn't carry any of the charging leads, they were always left with the support boat. I recall Tally Ho ran with us for a long while, and Allan Collins who I write to remembers humping the charging leads backwards and forwards when we returned at night after the trials. As well as the speed and sound trials in the lochs we ran from Campbeltown, with the Sunderland flying boats from Stranrarr. Out in the Irish Sea they dropped Sonar buoys, We used to hop it at high speeds, and they spent the day trying to pick us up on the Sonar

    I remember one day starting out for Larne, and when we finally arrived we spent nearly 3 hours trying to get along side, fighting a 12 knot current. Because of the state of the batteries we had to give it up as a bad job and return to Campbeltown

    Between returning to Dolphin for leave periods this carried on until 1950.

  2. I have been in touch with a chap off Tally-Ho, who used to run with us in Scotland. He says the charging leads went down the engine room hatch. His reply to how many was 'I don't bloody know I only used to hump them.

  3. Any way as far as I can recall we used to do about 6 runs in the day, but being down below I don't know if they were all done in the same direction, or one up the Loch, and one down. We were already tied up in the Loch so there was no travelling before we started. When we ran with the Sunderland flying boats from Campbeltown, it was a couple of hours before diving stations round about 10am, and we used to start back for home about 3pm! Always got dinner on the way back to Campbeltown.

  4. About the ballast tanks. I only know that the saddle tanks were removed and slimmer external tanks fitted, and as I said before it made for a very rough ride in choppy seas.

  5. I can't say that I remember a Diesel generator in the fore ends, unless it was for emergency lighting but then it would still have come under the engine room branch and as you say it would have been quite a big size. One other thing Peter I can definitely remember charging cables coming in through the Engine room Hatch.

    (Authors note - the engine being in the fore ends was suggested in some general notes written in the fifties describing the Scotsman. There is no evidence to support this positioning and plenty confirming the engine room site including photographs showing the exhaust emissions)

  6. I joined Scotsman in June 1948. Picked her up in Chatham. about a month before she started the dockyard trials. Going down to the motor room. The layout was just the same as the normal way. One bank of switches on either side of the boat connected direct to the props. As I said when I wrote to Derek. The engine was one single Paxman Ricardo, down the centre of the engine room, And could only generate enough Power to enable the boat to do 8 knots to keep the batteries topped up. I will attach the only picture of the boat that I have. It was taken at Poole, we were on a visit because our skipper lived there.

  7. QUESTION. Albert, it has been suggested in the past, that the Scotsman only used one screw when on passage, say to Dolphin. Do you have any memories of this?

    ANSWER. Yes Peter I do have memories of this. As far as I can recall the Paxman diesel Gen was never connected to the motors. We used to travel on both prop's but our speed was regulated to 8 Knots. I think this was the speed was that allowed that kept up the battery's charge

  8. Going back to Scotsman, we never had the luxury of the Ark in my days. The only time we didn't sleep on board was leave periods in Dolphin, or the odd time we went to Rothesay, and tied up along side Montclare. One or two of the other lads I wrote to told me about the Ark.

    Albert supplied a press clipping photograph of the Scotsman, about 1949/1950, visiting Poole Quay.

    (Re Ark - see Cliff Alexander anecdote. Author)

Chief Electrician Bill Smith - Served on Scotsman about 1957

  1. 'You must remember that the 'powers that be' kept changing things on the boat and when I was on her, they were using her as a floating test bed with all sorts of machinery up for'd for noise test trials'

  2. 'I Haven't a clue now about the rating of these motors but she definitely had an 'A' boat switchboard with a reverse current breaker as she only had one donk fitted amidships and only two main motors with double armatures.'

  3. 'I was LEM on the Scotsman with five batteries, one donk, A boat motors and switchboard. Normally charged from Solent or Selene who carried our charging cables. Sometimes we used a barge to stow our cables which was moored up in one of the lochs up North, we tied up one side and the charging boat the other side. It was great to be back on a normal boat after that lot (I went to Token). Battery layout: 4B in fore ends 1 2 and 3 accommodation space and 4 A in for'd part of donk shop.'

  4. 'Scotsman when I was on her was used as a test bed for machinery and the one that brings to mind was what we called the donk shop washing machine which was a device that took the sulphur out of fuel but the old mind is hazy. Another feature we had was the bulkhead octopus glands for cables which meant there was only one hole through the bulkhead instead of many but it was ugly and took a lot of space'.

Will Keeps

'Quite fast. Worked with her in Campbeltown with Crusader-dunking sonar. Solent was used as charger & living quarters. Took Solent down to Pompey Xmas '59 from Faslane, vents welded shut, inside gutted. HMS Brocklesby also worked dunking sonar.'

Dave Perkins - long serving senior submarine rating in Royal Navy and Royal Canadian Navy - submarine author

We also had a 'joy-stick ' control for planes in Solent. It basically consisted of an 8-position hydraulic valve. The problem with it was that it set the foreplanes and after planes individually. Midships was neutral. A body had to be pretty sharp to keep depth using it and the only man I saw actually using it was an EO who was obviously involved with its development. We never used it except when he was aboard. It was installed in addition to the normal fore and after planes 'tapper-gear ' controls.

When I left Solent in '57 she was still working as a 'Slippery S'. About three months later the three Slippery-S boats (Solent, Selene & Sleuth) were replaced by three snorting S-boats (Scythian, Seneschal and Sea Scout) and Solent was sent off to be charging boat for Scotsman. That's when I joined Scythian. Small world ain't it?


Note. The Solent was streamlined in the same manner as the Seraph.

Cliff Alexander AB (UC rating ) Sept 1955 - November 1956.

Joined the Scotsman at Rothesay with HMS Adamant as Third Squadron depot ship.

Over the telephone Cliff supplied clear memories of vital information about the charging mentioned in the CONTROL SECTION but in addition to this, mentioned other points of general interest. During review of the draft article, he added further written comment.

  1. There was a small fridge in aft area of the accommodation space.

  2. Substantially the boat looked internally like an unconverted S class with a crew of about 35 to 40. Stokers lived aft and most seamen slept in the fore ends. With the shortage of bunks, hammocks were even slung in the forends during extended passage e.g. between Rothesay and Portsmouth.

  3. Up the loch there was a house boat called the ARK on which the crew lived when running in the lochs.

    Additional comments from Cliff - the ARK was a flat bottomed barge about 35 feet long. It had two distinct accommodation sections, one for NCO's and the other for the rest of the crew - mixed seamen and stokers. It was fitted with bunks etc and was quite comfortable. There was a set of heads perched up on the sloping stern with a flush tank above that. Bathroom facilitates were built centrally and above the living space.

    When moored to a buoy with the Scotsman alongside the ARK in rough conditions, the two bumped together quite alarmingly at times, especially at Inveraray which was quite exposed - fenders were not practical. The Scotsman never sustained any damage however but the ARK did on more than one occasion - it sprang leaks. I recall hopping out of my bunk into ankle deep water. That was OK but the boat's cinema projector was half submerged in the mess area. A testament to the Bell & Howell projector's rugged construction was that with swift drying out and a bit of tinkering by the boat's electrician, films were viewed again that night. Water was pumped out and temporary repairs made until the ARK could be docked in Rothesay.

  4. He recalled the Scotsman was open to the public at Bristol.

  5. He recalled the deck in the substantial area of the former tube space, was a step up of about 18', he believes the extra battery or part was under here. The 4th battery was actually in two parts - half of it in the old tube space under the fridge etc. Not sure where the other half was. (Author. It is notable that in the unmodified boat there is a step down of about 30' so in Scotsman it would be an under floor compartment high enough for battery cells.)

    On top were the freezers for bread and the like. He believes there was only one bulkhead door. (Authors Note, there would have previously been two for torpedo reloading.)

    Cliff had a bunk in this far forward area. Additional comment from Cliff - there were only two bunks in this compartment squeezed in alongside the fridge on the port side. A narrow walkway was on the starboard side which in my case was the only way of gaining access to the bunk round the rear of the fridge. The for'd hydroplane housing were also up this end as well as the chain locker! The second bunk was occupied by the ship's cook, a man who enjoyed a drink rather too much. Occasionally he had to go ashore for periods to 'dry out'. As no replacement was supplied during these absences, I took over - quite an experience but an invaluable one.

  6. Cliff recalled the fan trunking overhead in the fore ends. Mounted on the trunking was a an electric fire. When coming down the vertical ladder through the only means of ingress, the fore end hatch, those new to the boat would hit their head on the hot fire!

  7. There are suggestions that a snort was fitted in the fin about the time Cliff was aboard. He has no memory of this and says the Scotsman at this time was solely engaged in deep fast battery runs in the Lochs for various trials. Additional comment from Cliff - Practically all my time on the Scotsman was spent 'running up the Lochs' i.e. Loch Goil and Loch Long. Shore facilities were sparse, so little shore time was taken.

    I was a UC3 on the boat. The ASDIC control cabinet was close the control room on the starboard side near the chart table cabinet. The Skipper, Lieutenant Commander Harvey-Dutton had good 'connections ' which meant we had free access to the grounds of Inveraray Castle (while the residents were away of course and even had a peek inside on one occasion - a magnificent place). The Duke and Duchess of Argyle came aboard for dinner in the Wardroom on one occasion, which meant that most of us stayed well out of the way. A bit difficult considering the cramped situation. The Duke was wearing a kilt as I recall and you can imagine the scene as he descended the vertical ladder from the casing into the forends. And NO I did not do the cooking.

    Apart from the Skipper, the only crew members I can recall by name are: Terrence Brogan, the bunting tosser (signalman) - couldn't call him Terry, it had to be Terrence. Len Golding the Scratcher (2nd Coxswain) a wartime veteran who had aged beyond his years but a great character. The rest are clear images in my memory but their names escape me.

    Here is an irony.

    High speed/low speed runs up and down sound ranges with boffins aboard huddled over sound recording equipment, cameras etc and yet one day at Loch Goil, one boffin approached me and rather sheepishly asked if they could borrow my tape recorder as theirs was kaput. Mine was one of the cheapest of the cheap reel to reel recorders of the day - an 'Elizabethan' as I recall - a big black boxy thing. Cheap maybe but it did the trick apparently.



Peter. Have just recalled another fact/anecdote or two in the middle of the night actually.

One of the occasions I stepped into the cooks shoes was after the incident of 'The Exploding Puddings'. I used this incident as the basis for an award winning speech when I belonged to the Toastmasters organization in the 70's.

The cook used the dangerous practice of placing unopened tinned steamed puddings around the edge of his hotplates to heat them. He got away with doing this for ages but one day as he reached across to retrieve one it exploded in his face, so it was off to hospital for the cook!

Into the speech story I wove the character of 'Nazzer' Bone. Nazzer was a Stoker Mechanic and quite a personality. Short and stocky with a wicked sense of humour he sported a black bushy beard.


Lt (E) Phil Toms Royal Navy (ret). Chief ERA HM/SM Scotsman, 1954

My first awareness of Scotsman was long before I joined Submarines, I was an ERA on board the Oakham Castle, one of the sea going Sonar training ships. Our Sonar lads were the best in the business. The occasion was a large Fleet exercise somewhere off North Scotland and the Anti Submarine screen around the fleet consisted of Oakham Castle and a host of ordinary Frigates. Scotsman was the attacking boat and came through the screen as if they didn't exist, bar for Oakham Castle - our lads picked her up and got the Admirals permission to track her, we were struggling to keep up with her and the rest of the fleet had hysterics as we had right of way and they had to keep out of our way. That was a painful jerk to the Navy's belief that submarine screens could keep a boat away from the big targets.

This took place sometime between 1948-51 my time on Oakham Castle, I joined boats in June 51, and worked my way through 'Solent' 'Sirdar' (lost her in Sheerness Dockyard, east coast floods of 1953, capsized in dry dock, dock gates were washed away, from there I went to 'Auriga', a 'pier head jump' and sailed to America, I was the 'Outside Wrecker'. On our return trip some 12 months later, we snorted from the Bahamas to Plymouth.

On the 1st June 1954 I went to Scotsman as Chief of the boat as she was just completing a refit at Devonport, Scotsman's details as I found her when I joined, All her tubes were removed, she had batteries from the Fore-ends to the Engine Room Bulkhead.

The Main Motors were 'A' boat motors and our 'Donk' was a single 'U' class (wartime small boat one), when running on the surface with the engine, we ran on one screw and barely made 8 knots. The diesel was not connected to a propeller, it's function was to just keep the batteries topped up.

The hull was super-streamlined any overlap on the plates were filled in and before her final undocking and painting the entire external surface of the boat was 'sanded down' and special paint which dried very hard and shiny were used on her.

Most of our running was done in Loch Long it was part of a Sonar research area the Loch had Sonar receivers along its length, we had to run up and down the Loch doing various activities and had to turn around at the end of each run while still dived. The time I was on her there were many tests of equipment planned for the Nuclear Boat's, in the fore-ends there was a clear space about 3m x 3m, which had connections for Hydraulic, Compressed Air and Electricity, 'Boffins' used to come down to set up their test rigs on it. The other main tests were on different types of propellers, the Tiffies and Stokers had to change propellers at the floating dock in Rothesay. All too often these Boffin designed props used to forget to fit a screwed hole for us to fit an eye bolt. It became a real hassle with our Bos'n rigging up weird and wonderful slings to lift them, many had strange shaped propeller blades which we dare not damage when lifting.

To check these props working, we had a rare submarine fitting, a porthole immediately over the props so that a camera could record the water flow through the screws and a microphone above the props but inboard to listen for the 'Singing Propellers' (Pressure pulses from the front of the blades to Sub pressure spaces at the back of the blades).

We also had the first combined steering and planes 'Joy Stick'

On the high-speed underwater trials Scotsman used to bank over when turning apparently the Fin became important in such turns.

We were the most hated boat in the 3rd Squadron, when we came along side Adamant one of the A boats had to charge up our batteries, Capt S/M stated that we had to send over our ERAs and Stokers to do the charge, Scotsman's engine-room staff were the most experienced bunch of tiffies and stokers anywhere. It was amazing the number of differences in A boats supposedly all the same class.

My final fling with the Scotsman was when we sailed for Pompey, it took us three weeks, at times the tide was pushing us back in Liverpool Bay, She went in for a refit and I went to the Sturdy.

Regards Phil Toms.

John Eade - British Submarine researcher and writer re the Scotsman.

'A few years back I had the opportunity to speak to Cdr J J Tall, the Royal Navy Submarine Museum Director about the possibility of gifted or loaned artefacts. To which he did comment that he had sheds full of submarine propellers all shapes sizes and designs and was unsure of what their eventual fate would be. I believe the work carried out in this area had a far ranging effect on modern submarine development.'

John provided some press clippings of the time reporting on Naval Estimates. This is a small example of the emphasize on submarine and anti-submarine research and development.

'Navy and Anti-Submarine Defences' by Nowell Hall 'The Scotsman' Naval Correspondent. 7th - March 1950.

Of the Navy's allocation of Pounds Sterling 193,000,000 - 3,750,000 above the estimate for the current financial year - 72,930,000, the heaviest single item, is reserved for production and research. Much of it will be spent on countering the menace of the fast submarine. etc

This submarine built by Scotts of Greenock and commissioned in 1944 as a standard Group III S Class submarine. She served in the Asian theatre for a short period until returning to the UK when the war ended. Her last trial, a deep 'crush' depth test in Kames Bay in 1964, being sunk and then raised by the Admiralty lifting craft LC10 and LC11, before being sold to the West of Scotland Shipbreaking Company.

Scotts were apparently still involved removing equipment.

And so ended the life of this small submarine that with its crews and the various boffins, contributed so much to Royal Navy submarine and ASW technology, from the vital early Cold War years following WWII up to the advent of the Royal Navy SSN.

Peter D Hulme, copyright 2007. Taupo, New Zealand.



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Diesel Submarines 1948 - 1958Trials with HM Submarine Seraph