Home - Dits & Bits - BR3043 - Part One - Chapter 10


Chapter 10: 1914-18 Single Hull Types H and R Classes

10.1 Introduction

1. To meet part of the large submarine building programme started in November 1914 negotiations took place with the Bethlehem Steel Works, USA for H boats designed by the Electric Boat Company of America and of which some were then being used by the US Navy. On 10 November 1914 a contract was signed with Bethlehem Steel Works for twenty boats, 'ten to be delivered during the war and ten afterwards'. built the first ten, H1 to H10. The first boat was completed in May 1915 and arrived in British waters in June 1915 and the whole ten were completed before the end of that month. All the drawings and patterns were available with the Electric Boat Company and this of course made for quick production. The second ten to be built in the USA were delayed since the engines, motors and other fittings were shipped to England to be put in the H boats mentioned below. Only four of the second ten boats were delivered to the RN H11, H12, H14 and H15 about 1918. The only completion date known is of H15 on 14 September 1918. H14 and H15 were transferred to the Royal Canadian Navy early in 1919,

H class boats
H class boats

10.2 Design

2. In January 1917 an order was placed with for twelve boats of the H type but modified from the American design to accommodate a heavier torpedo armament and W/T gear of much higher power. They were called the H21 Class, and numbered H21-32. As mentioned above engines, main motors and other fittings were obtained from America and this made for quick production. Complete sets of equipment for four boats were delivered to Barrow from the USA by mid May 1917. The first boat, H21, was completed in January 1918.

In June 1917 further orders were given for six boats from Cammell Laird (H33-38) eight from (H39-46), four from (H47-50), two from Pembroke Dockyard (H51-52) and two from (H53-54). Ten of these, H35-38 at Cammell Laird, H39, H40, H45 and H46 at and H53-54 at Devonport were subsequently cancelled when it was decided to build twelve R Class vessels in October 1917. The engines and motors for the boats ordered in June 1917 were made in England to the American design used in H1-20.

3. The redesign of H21 from Hl-20 consisted primarily of fitting 21-inch bow torpedo tubes in lieu of 18-inch tubes. This meant increasing the length of the boat by about 21ft although the diameter of the pressure hull amidships remained the same. The displacement increased by 16%. The redesign had its problems and modifications had to be made. As in most single hull vessels the surface stability of the H boats was small. In H1-20 the design surface GM was 7in. In H21 when first inclined it was 6.7in and after modification fell to 4.5 in. In general in the H21 Class in service the GM was 4-5 in. This is about the same as in the B Class and C Class, but in the light surface condition, without torpedoes etc as is likely to be experience when undergoing refit. The vessel was unstable with the battery removed and it was necessary to admit water ballast as the batteries were removed and to flood the duct keel before the last few batteries were taken out. The trouble originally in these boats appears to have been in obtaining a submerged trim more than stability as is explained in Paragraph 7.

4. The main characteristics of the two designs were:

H1-20 H21 Class
Length overall 150ft 3in. 171ft 9in.
Beam maximum (ex fenders) 15ft 4in. 15ft 4in.
Depth maximum 15ft 4in. 15ft 4in.
Displacement surface, tons 364 423
Displacement submerged, tons 434 510
Bhp surface 480 480
Bhp submerged 620 620
No. of cells 120 120
Speed surface, knots 13 13
Speed submerged, knots 11 10-10.5
Endurance surface, miles at knots 2000 at 13 2000 at 13
Endurance submerged, miles at knots 30 at 5 70 at 3
Torpedo tubes, bow Four 18-inch Four 21-inch

The information given above for H1-20 is taken from some notes prepared by DNC at the time. The details, which follow, concern the H21 Class. An Arrangement of WT Compartments is shown in as shown in Fig 10.1 and a General Arrangement in Plate 31.

5. The H21 Class were of the single hull type similar to the C Class although not of a complete spindle form symmetrical about an axis as in that class. The amidship sections were circular from 34-84 Frame stations i.e. over a length of 62ft. The sections aft were flattened vertically forming a chisel, end to get in two shafts as against the single shaft in the C Class. With this type of stern the boat was very stable for keeping depth underway submerged. The sections forward were raised and were flattened horizontally to assist in fitting the four bow tubes. The main axis through the centres of the amidships circular sections was parallel to the datum line and aft passed through the centre of the flat chisel stern. Forward this same axis was only slightly above the forefoot.

The arrangement aft of rudder, hydroplanes and stern fins followed the C Class pattern modified to take two shafts.

10.3 Dimensions

6. The Loa was 171ft 9 in. A figure of 171ft 0 in is often quoted but actually the after hydroplanes extended 9in aft of the rudder. The Lbp was approximately 167ft 3in and not the 164ft 7½in mentioned in Fig 10.2. The Lph was 150ft 9in including the two end main ballast tanks which were tested to 75lb/in2.

The moulded beam of the circular pressure hull amidships was 15ft 3in and to outside of plating 15ft 4in. They were fitted with 2½in rubbing fenders each side which made the maximum beam 15ft 9in.

The depth was the same as the beam, moulded 15ft 3in maximum 15ft 4in. The 'duct' keel was 12in deep and followed the contour of the hull, which meant moulded blocks or cradles for docking. This gave an overall depth of 16ft 4in.

The draught is given as 13ft 1in at 434 tons displacement and 13ft 6 in at 448 tons displacement. At 438 tons displacement the mean draught would be about 13ft 2½in. At this draught the freeboard to the top of the superstructure was approximately 5ft 6in and to the bridge deck 11ft 9in.

Fig 10.1
Fig 10.1
Fig 10.2
Fig 10.2

10.4 Displacement and Stability

7. The submerged displacement was originally 510.8 tons and this included a buoyancy space in the bows of 6.5 tons. When H21, the first boat, was inclined at on 17 December 1917 the surface displacement was 423 tons and the GM 6.7 in at a draught of 12ft 9in. This meant that approximately 88 tons of main ballast water had been removed and this was the full capacity of the four main tanks at that time. The stability was good but from the modifications made it is obvious the boat was heavy aft. Adjustments were made so that the surface displacement became 438.3 tons and the GM fell to 4.5in,

From a study of the particulars quoted by and DNC at various times and from Fig 10.2 it would appear that the following happened.

  • (a) A buoyancy tank in the bows was converted into a controlled free flooding space. A statement by has been seen that 'the submerged displacement with the buoyancy tank deducted is 504.3 tons.'
  • (b) The original No 3 main ballast tank was divided and the after portion made into an auxiliary ballast tank of 14.5 tons capacity. This left 25.5 tons of space in No 3 tank taking into account the buoyancy of permanent ballast stowed in this tank. This change left a total of just over 70 tons of main ballast water in the four main tanks.
  • (c) The experiment after modification showed that only 66 tons of main ballast water was used. DNC later confirmed that the capacity of the main tanks was 67 tons. This must mean that the after main tank of 3. 75 tons capacity was not used.
  • (d). Originally the boats were carrying about 88 tons of main ballast water which was now cut to 66 tons. Since this was to correct trim and not total weight, 24 tons of ballast was added. After the adjustment all this class were carrying on completion over 30 tons of permanent ballast mainly amidships in No 3 main tank.

8. The submerged displacement is therefore taken as 504 tons, the surface displacement as 438 tons with 66 tons of main ballast water. With 6.5 tons of controlled free flooding space the reserve of buoyancy was 16.6%. This is a very reasonable figure for a single hull boat. The standard displacement was fixed at 410 tons when required in 1930. This was the surface displacement less all oil fuel, lubricating oil, fresh water and about 6 tons of auxiliary ballast and trimming water.

Some years after the class had completed DNC quoted figures for the class of surface displacement with main tanks empty 442 tons and surface as inclined 448 tons. This means that 6 tons of water remained in the main tanks on the surface. This is the service surface displacement. In this condition the reserve of buoyancy was 15.1%.

9. The stability as designed was surface GM 6in. and submerged BG 14in. The surface GM in the H21 inclining experiment mentioned in Paragraph 7 was 6.7in, but after adjustments were made in that boat it fell to 4.5in.

The major reason for this loss of GM was the increase In surface displacement of 15 tons with an increase in draught of 5.5in. The waterline was decreasing rapidly as draught Increased. This meant a quick reduction in the moment of Inertia of the waterplane and in metacentric height.

After some years in service, DNC quoted the surface GM as 4-5in and the submerged BG as 10-11in for the class.

10.5 Speed and Endurance

10. The design figures were.

(a) Speed surface 13 knots
(b) Speed submerged 10-10.5 knots
(c) Endurance surface, miles 2000 at 13 knots
(d) Endurance submerged, miles 70 at 3 knots
  • Reference (a) above. The speed of 13 knots is the same design figure as for H1-20 and with the same machinery this assumption was undoubtedly optimistic with the increase in displacement. A reference has been seen giving 12 knots as the full speed for H5, one of the smaller type, and 12 knots was quoted for the H21 Class after completion of the first vessels. A reasonable surface speed given later was of the order of 11.4 knots. In the 1930's the operational speed was 11.5 knots.
  • Reference (b) above. The actual submerged speed expected was undoubtedly nearer 10 knots than 10.5 knots although the latter figure was quoted after completion. In 1918 DNC stated that '10 knots was expected to be obtained' as a 'short burst' with motors overloaded. The reference in (a) above which gave 12 knots surface speed in H5 also gave a submerged speed of only 8 knots for that boat, designed for 11 knots.
  • The main motors were rated at a total of 320bhp continuous and 620 bhp for 1 hour, in the 1930's DNC was quoting a speed 7.5-8 knots but this must have been at continuous rating. A figure of 9 knots is also given as the operational speed and endurance in CB 1815 (1930). It seems that 9 knots could be achieved at the 1-hour rating and about 8 knots at continuous rating of the motors,
  • Reference (c) above. H1-20 with 18 tons of fuel was stated to have a surface endurance of 2000 miles at 13 knots and this is considered optimistic. With only 16 tons of fuel in the H21 Class the figure could not exceed 1800 miles even if 13 knots had been achieved. at one time quoted this figure and also 2970 miles at 10 knots. All these figures are high, In the 1930's DNC gave 1100 miles at full speed, 1600 miles at 10 knots and 2000 miles at economical speed which are taken as reasonable service figures. They are related to a full speed of 11.4 knots.
  • Reference (d) above. The submerged endurance to be expected was generally greatly exaggerated although DNC did early on quote 23 miles at 4 knots.
  • Reasonable figures given in the 1930's are 9 miles at 8 knots, 34 miles at 3.5 knots and 100 miles at 1.5 knots.

10.6 Structure

11. The general layout and construction was similar to the early spindle hull types with main and auxiliary ballast tanks under and at the sides of the battery tanks in the amidships portion of the boat, These tanks at the sides extended well above the tops of the battery tanks.

The pressure hull plating was 20lb amidships. The frame spacing between Frames 26-82 was 1ft 6½in., elsewhere it varied. At one time the diving depth was given as 250 feet but this is optimistic and is probably an error. The C Class, with the same pressure hull plating and frame spacing on a smaller diameter circular hull, was designed for only 100 feet depth. However, later on, the maximum diving depth for the H Class was given as 150 feet, the boats being tested to 100 feet, it is known that some of the boats on service exceeded 150 feet depth although perhaps by force of the circumstance.

Four Internal main WT bulkheads were fitted and main compartments tested to 30lb/in. There were, however two large compartments, the officers' quarters and torpedo room forward of 68 tons capacity and the motor and engine room aft of 101 tons without allowing for the equipment in them. The flooding of either of these compartments would have been fatal.

12. The duct keel in this class was unique. It took the place of the ballast or docking keel and from just forward of amidships at approximately Frame 48 to the after end of the keel It was watertight and could be flooded. Its capacity was 2.75 tons from Frame 48 forward this keel was still called the duct keel but was not watertight. The amount of permanent ballast carried varied between boats but was over 30 tons, H26 had 32.5 tons on completion. Some of this permanent ballast may have been carried in the non-watertight part of the duct keel but the major portion was stowed in No 3 main tank amidships.

10.7 Tanks

13. The tank tests changed and may have been following American practice. The differences compared with the E Class were:

Tanks H-Class lb/in2 E-Class lb/in2
Main ballast 75 50
Auxiliary ballast 75 50
Trimming 75 50
WRT 75 50
Forbes Log 75 50
Oil fuel 25 50
Lubricating oil
Drain oil
10 50
Main compartments 30 35
Conning tower 35 35
Battery tanks 3 2

In the H Class the fresh water tanks were tested to only 5lb/in2 but they did not form part of the pressure hull. The WT portion of the duct keel was tested to 75lb/in2 and the adjusting tank 200lb/in2 before installation and 150lb/in2 when in place.

10.7.1 Main Ballast Tanks

14. The four main ballast tanks were sited one at the fore end of the pressure hull, one at the extreme after end and two amidships under and at the sides of the two battery tanks as in the early single bull type submarines. Cross venting troubles were experienced with the two amidships tanks. As designed, the total capacity of the main tanks taken as the difference between the submerged and surface displacements was of the order of 88 tons. Adjustments had to be made, and part of No 3 main tank was converted into an auxiliary ballast tank. The total capacity of the four tanks then became 70.2 tons, which allowed for the buoyancy of the permanent ballast stowed in them particularly in No 3 tank. As explained in Paragraph 7 it appears that No 4 tank aft of 3.8 tons capacity could not be used. This gave 66.4 tons of main ballast water.

The bow superstructure was originally a buoyancy space. This was converted into a controlled free flooding space of 6.5 tons capacity.

10.7.2 Oil Fuel Tanks

15. There were three oil fuel tanks with a total capacity of 15.9 tons all In the torpedo room forward. They were self -compensating.

The H21 Class carried 2.0 tons less oil fuel than H1-20 and since there was tank space to spare it seems reasonably obvious that additional weight could not be accepted

10.7.3 Other Tanks

16. As completed there was over 41 tons of tank capacity for auxiliary ballast water in five tanks. This was far in excess of normal requirements. The total compensating and trimming water required would not exceed 15 tons. It seems obvious that some of these tanks could not be used for other purposes at the expense of permanent ballast because of stability. They had to be flooded when the battery was removed.

A duct keel as mentioned in Paragraph 12. With a capacity of 2.75 tons it was tested to 75lb/in2 as for all the internal water tanks. It was therefore a strong structure and was of course the docking keel as well.

A mason for incorporating this duct keel in the design is difficult to find. It was not flooded to dive and emptied on the surface as a main ballast tank since it would then be included in the amount of main ballast water used and it is not. As stated in Paragraph 3 it was necessary to flood this keel as the last few batteries were removed from the boat. But in the design this requirement could have been achieved by a much simpler method.

Adjusting tank. This was a very strong specially built cylindrical tank tested to 200lb/in2 before installation and 150lb/in2 when in place, fitted amidships between the periscope wells and above main tank top level, it had a capacity of 1 ton and was a statical diving tank.

10.8 Main Machinery

17. The first RN twin shafted single hulled boats, the main engines were of American design two in number eight cylinder vertical SA diesel of 480 bhp total at 375 rev/min, they were non-reversible. , Ruston and Hornsby and the N B Diesel Co made the engines.

The main motors were also of American design with a total bhp of 620 bhp for one hour and a continuous rating of 320 bhp. The battery consisted of 120 cells in two sections of 60 cells, each in a battery tank.

10.9 Armament

18. The H21 Class had four 21-inch bow torpedo tubes In lieu of the four 18-inch tubes in H1-20, but carried only two spares making a total of six torpedoes.

This change in size of tubes was responsible for the increase In length of the boat of approximately 21ft and in surface displacement of over 70 tons. The torpedo tube space was divided from the torpedo room by a WT bulkhead just aft of the tubes which appears to have been added some time after construction commenced. The torpedo room and the torpedo embarkation hatch were in the same main compartment as the officers' quarters. Bow shutters were fitted. Although, normally, only six torpedoes were carried, the war complement was stated to be eight.

They carried 1 Lewis gun.

10.10 R Class

19. In that phase of the anti-submarine campaign during the war, which involved submarine versus submarine, difficulty was experienced in approaching enemy submarines undetected. If the enemy was moving away, she could never be caught submerged and the only chance our submarines had was to surface and open fire with a gun. It was for this purpose that the 4-inch gun was fitted at bridge level in the L Class. If on the other hand a submarine was given a high-submerged speed she might be able to overtake the enemy and sink her, especially if the attacking boat could launch a number of torpedoes. It was on this premise that the R Class was designed.

10.11 Design

20. In March 1917 DNC submitted to the Board the design of a small high-submerged speed submarine for this type of anti-submarine work but the proposal was not approved. Later in the year however Commodore (S) suggested that the design should be completed. This was done and approved later in 1917.

21. Orders for twelve boats were placed in October 1917 with four at (R1-4), two at Pembroke Dockyard (R5-6), two at (R7-8), two at (R9-10), and two at Cammell Laird (R11-12). The first boat, R7, completed at in June 1918 within nine months of order and seven of the class were completed before the end of that year, the two boats at Pembroke were not built.

22. The original design submitted to the Board had four 18-inch bow torpedo tubes, a submerged speed of 13.5-14 knots and a surface speed of 11-12 knots with two H Class engines.

The final design had six 18-inch tubes, a submerged speed of 15 knots and a surface speed of 9.5-10 knots with one H Class engine.

23. The main particulars with the H21 Class as completed are:

R Class H21 Class
Length overall 163ft 9in. 171ft 9in.
Beam maximum (ex fenders) 15ft 3in. 15ft 4in.
Depth maximum 15ft 3in. 15ft 4in.
Displacement surface tons 410 438
Displacement submerged tons 503 504
Reserve of buoyancy 23.5 16.6
Speed surface knots 9.5 11.4 (*13)
Speed submerged knots 15 9 (*10)
Torpedo tubes bow Six 18-inch Four 21-inch

*As designed. A general arrangement of the R Class is given in Plate 32.

24. They were single hulled boats of spindle form except at the forward end. Sections were circular about the main axis from the after end to the forward battery tank but from then became elliptical about a vertical axis and centres of hull section rose to the bows. Frame spacing was 18 in, except in way of Nos 1, 2 and 4 battery tanks where it was 19½in. The designed diving depth is given at 250 feet.

The superstructure was of a bare minimum and consisted only of a large streamlined bow structure extending about 40ft back from the stem with the forward end controlled free flooding tanks streamlined fairing around the bridge. Although with five internal main bulkheads subdivision was not good. The main machinery space was 53ft long and occupied 35% of the length of the boat, but sub-division of this space would have been most difficult.

There was no ballast keel but bilge keels were fitted,

Horizontal fins at the after end formed the outer bearings for the after hydroplanes and were in themselves necessary to give stability to the hull form when running submerged. The single propeller was on the main axis at the extreme after end of the boat. Twin spade rudders for quick manoeuvring were about 23ft from the stern and 3ft 6in. apart with a single centreline guard forward of them.

10.12 Dimensions

25. The Loa is given as 163ft 0 in by some authorities and 163ft 9in by others. The length from the stem to the after end of the hull was 161ft 6in. The propeller projected further aft, the tip of the propeller boss being 2ft 3in aft of the hull so that the Loa was 163ft 9in. The Lbp was 138ft 3 in which is an out of normal, figure because the rudders were 23ft in forward of the after end,

The Lph was 151ft 6 in. The foremost 10ft of the boat was free flooding. The aftermost 10ft contained the after hydroplane gear and was cone shaped. The forward end of the space was only 3ft 6 in diameter and formed the after bulkhead of the trimming tank. It was watertight and has been included as part of the pressure hull.

The maximum diameter of the pressure hull was some way forward of amidships and was 15ft 3in to outside of plating, Rubbing fenders were fitted at mid-depth to give a maximum overall beam of 15ft 9in.

26. The mean draught was about 11ft 6in at 410 tons surface displacement. The approximate freeboard to the bridge deck, at this draught, was 15ft and to the gun decks over 9ft. This was a very good freeboard and more than in any previous RN submarine.

10.13 Displacement and Stability

27. Between 1918 and 1920 the submerged displacement was given varying between 500 and 505 tons and the surface displacement between 415 and 420 tons.

For R7 and R8 gave the submerged displacement as 503.5 tons. From the draught marks after launch the surface weight was assessed as 403 tons. The total capacity of main ballast tanks was 93 tons. Six tons of ballast was added under No 1 battery, being stowed well forward undoubtedly for trim. The surface displacement would therefore be about 410 tons. In 1930, the standard displacement was fixed at 385 tons. This is in reasonable agreement with the surface displacement of 410 tons, but the surface displacement of 415 tons is quoted so frequently that it is evident that all the main ballast water could not be blown from the tanks and 415 tons is taken as the service surface displacement.

Figures for the R Class are therefore taken as submerged displacement 503 tons, surface displacement with main tanks empty 410 tons, and the reserve of buoyancy including the controlled free flooding space of 3.7 tons as 23.5% - a high figure for a single hull boat. At the service displacement of 415 tons it fell to 22.1%.

28. The only stability figures seen were given by DNC in 1918 as surface GM 9in and submerged BG 15in and are probably design values.

10.14 Speed and Endurance

29. The design figures were:

(a) Speed surface 9.5 knots
(b) Speed submerged 15 knots
(c) Endurance surface 2000 miles at 9 knots
(d) Endurance submerged 15 miles at 15 knots
240 miles at 4 knots
  • Reference (a) above. During the building stage 9.5 to 10 knots was expected. In 1918 DNC gave 9.5 knots and 10 knots. After completion 9.5 knots was usually quoted and there is no doubt this speed was achieved on trials. In 1930 the operational speed was 8.6 knots in fine weather with reasonably clean bottom. These trial and operational speeds are compatible.
  • Reference (b) above. The design speed of 15 knots was at 1200 bhp which was given to be the 'full load' of the motors at the 1 hour discharge rating. Because of the importance of the operational maximum speed being held for a reasonably long period in this class, the power at this speed would undoubtedly be limited to a longer rating of the motors. A trial speed of 15 knots continued to be quoted in the 1920's and would appear to have been obtained although perhaps at overload power. In 1930 the maximum operational speed based on the latest results from sea was taken as 12.5 knots which could be held for 1.8 hours.
  • Reference (c) above. The designed endurance was at first achieved and even exceeded. 2400 miles at full speed and 3000 miles at economical speed are given. Over 10 years after completion the operational endurance was still good at 2000 miles at 8 knots using 12.3 tons of fuel.
  • Reference (d) above, the design endurance was optimistic. 150 miles at 4 knots was given later but this was still high. Service figures given when only two vessels of the class remained were 12.5 knots for 1.8 hours, 5 knots for 12 hours and 1.5 knots for 97 hours on auxiliary drive. Better figures would have been obtained when the vessels were new.

10.15 Tanks

10.15.1 Main Ballast Tanks

30. Four main tanks were fitted, one abreast each of the four battery tanks. Nos 2, 3 and 4 tanks extended under the bottom and round the sides of the battery tanks. No 1 battery had to be sited lower than the other three batteries to allow torpedoes to be loaded into the lower tubes so No 1 main tank was at the sides only of No 1 battery tank, with a cross flooding trunk between port and starboard sides. The space under No 1 battery was used to stow permanent ballast. The total capacity of main tanks Nos 1-4 was 76.3 tons.

In addition two main tanks A of 6.8 tons and B of 10 tons were at the extreme forward end of the pressure hull to ensure that with the tanks blown the boat had a good trim by the stern and 'so prevent spontaneous diving when on the surface'. There is no doubt that these tanks would also be useful If the boat got out of control bow down when running at high speed submerged as mentioned In Paragraph 36.

The total capacity of the main tanks was 93 tons. The Kingston to each tank was in the crown of a small recess, in the hull at the bottom of the tank, and was hand operated. This explains in part the difficulty of completely blowing the tanks empty as mentioned in Paragraph 27. All vent valves were telemotor operated from the control room.

The fore end of the bow superstructure was a controlled free flooding space with a capacity of 3.73 tons.

10.15.2 Oil Fuel Tanks

31. Six tanks carried 13.25 tons of fuel of sg 0.896. They were sided tanks, two forward under the rear end of the torpedo tubes and four under the main engine. They were self-compensated.

10.15.3 Other Tanks

32. Five auxiliary ballast tanks had a total capacity of 9.2 tons. This is a considerable reduction from the 41 tons in H21 of very similar size and quantity of oil fuel, etc. Other tanks were as normally arranged although one space was found for the stowage of air bottles and another for distilled water - the first in a small boat.

10.16 Main Machinery

33. A single shaft boat with one main engine of the H Class type giving 240 bhp at 375-380 rev/min. Directly aft of the main engine the shaft carried two main motors giving a total of 1200 bhp. Further aft on the propeller shaft was an auxiliary propelling motor of 25 bhp for slow speeds submerged. This auxiliary drive was actually mounted on the shaft and not as In the L Class and L50 Class actuating the shaft through gearing. Chatham made the engines for R1-4 for R10 by the NB Diesel Co and for R7, R8, R9, R11 and R12 by Ruston and Hornsby.

The battery consisted of 220 cells of the J Class type split into four sections of 55 cells each, each section in a separate battery tank. Battery tanks with wood covers were fitted and not battery compartments presumably because of space.

10.17 Armament

34. Six 18-inch torpedo tubes were a powerful torpedo armament for this size of boat. The bulkhead at the after end of the tubes, which had been fitted in the H Class, was now standard practice.

In the design one spare torpedo was included but no spares appear to have been carried in peace time. The war complement was six spares. Stowage of these spares must have been most difficult and at the expense of the senior ratings' accommodation.

Originally it was intended to fit a 4-inch gun on a gun deck just forward of the bridge and in some vessels the gun deck was built together with a large gun access trunk and a magazine. Some drawings show the 4-inch gun. But there Is some doubt whether a gun was ever carried. Particular attention had been paid to streamlining the hull and topsides to obtain the submerged speed and a gun would hardly have been in keeping with that policy. Some authorities state that the gun was fitted and others thatft was not. Whatever happened at first the gun structure and gun was not fitted. In the later vessels and was removed from any of the earlier boats if so fitted.

10.18 Hydrophones

35. They had powerful and sensitive hydrophone equipment of five hydrophones by which it was claimed 'they could approach an enemy and obtain her position without using the periscope'. The hydrophone cabinet was just aft of the torpedo tube space.

10.19 Hydroplanes

36. The usual forward (drowned type) and after hydroplanes were fitted but a reference is made by DNC that emergency planes were fitted amidships designed to bring the boat level should she through any cause dive at an angle when going at high speed submerged. It is thought that this must have been in the original design but deleted later; no further reference to such hydroplanes has been seen. It is considered that blowing water from A and B main ballast tanks would have been much more effective in such an emergency than amidships hydroplanes and these tanks may have been introduced at some stage In lieu of the planes.



You say above about H1-H10 "the main engines were of American design two in number eight cylinder vertical SA diesel of 480 bhp total at 375 rev/min, they were non-reversible."
Does "non-reversible" mean that the engine could not reverse or that the propulsion had no reverse gear? I am trying to understand if the submarine could travel backwards either under diesel or electric power.
My G'Grandfather was in H6 when it grounded. I want to know if he could have tried to reverse off of the bank or could only wait for high tide and drive forward off of it.
Can you also please explain the abbreviation "SA"?
   Michael Tue, 28 Jun 2016
The SA stands for "Single Armature"

The engine was used to provide power for the electric motors which provided the drive. These were reversible.
   Merlin Tue, 28 Jun 2016

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Chapter 9: Monitor M Class TypesChapter 11: 1914-18 Saddle Tank Types L and L50 Classes