UB I Type Coastal UBoats UB 1 through UB 17, 1915
These submarines were tiny, with just 2 torpedo tubes forward with no reloads (though some drawings show a spare torpedo, this seems hard to imagine when you consider the size of the interior and the demands for accommodation at sea). They carried a single officer and 13 men.
The Germans built other coastal submarines, but types UB II and UB III were significantly larger and more capable. A measure of this growth rate is seen in the fact that the UC I type of coastal minelaying submarines developed in parallel with the UB I coastal type (both to meet wartime needs for fast increases in production) were more similar to the UB I boats than were the UB II boats. Indeed, the UC I type seems based on this design, but had a longer nose to provide room for storage of their sea mines.
UB I Type Evolution and Design
(this section courtesy of Tom Koehl, with edits and analysis of construction variation by Tone)
The development of the UB I type submarine was spurred by the Imperial German Army offensive into the Low Countries in the Summer of 1914. Seizure of the ports of Bruge and Ostende gave the Kaiser’s forces improved access to the North Sea and the English Channel. Recognizing that the resisting British divisions at the Front depended upon a steady flow of ammunition and stores across the Channel, the German High Command, in order to sustain its momentum as it turned southwards into France, set plans in motion to disrupt Channel shipping as soon as possible.
The large ocean-going German submarines were considered too unweildy to operate efficiently in the restrictive waters of the Channel. A new, smaller submarine was needed: one that could be built rapidly and transported by secure overland routes to operating bases in Flanders. Coincidentally, in October of 1914, a small stock of Daimler marine diesel engines was allocated for naval submarine construction. These four-cylinder, 60 shaft horse power engines were rapidly combined with two 45 centimeter torpedo tubes to form the nucleus of the UB I design.
The Uboot Inspektion (UI), under the Reichs-Marine-Amt (RMA), or Imperial Naval Office, established the specifications for a new coastal submarine design, designated Project 34, which could be constructed in the brief span of four months. The boat which evolved under the direction of Dr. Hans Techel and his engineering team at the Krupp yards of Germaniawerft was an efficient blend of minimal resources, compact dimensions, simplicity of design and utilitarian ingenuity.
Conceived as a single-hulled boat displacing approximately 125 tons, the UB I design was dictated by two essential criteria: first, the maximum allowable width for rail transportation, which worked out to be 3.15 meters; and second, the requirement for quick, simple construction which translated into a totally functional design totally devoid of compound curves and complex assemblies.
Because of the size constraint, only a single propeller was used. As the supply of Daimler engines was limited, the Korting diesel engine as used in large motor launches was also used with only minimal modification. The pressure hull was riveted up from cylindrical and truncated conical boiler plate sections. While simple to fabricate, this gave the boats a distinctively angular shape below water, which was faired into a horizontally oriented elliptical bow cap to accommodate side-by-side torpedo tubes. A narrow, free-flooding deck casing was fitted to blend into the bow cap and ran the full length of the hull, and a relatively large conning tower was positioned amidships with an angled torpedo loading hatch aft of the tower superstructure. The interior of the hull was devoid of bulkheads forward of this opening to enable torpedoes to be loaded into the tubes.
Submerged propulsion for the boats was provided by a 120 shaft horse power electric motor built by Siemens Schuckertwerke. The storage batteries (referred to as accumulators in the Royal Navy) consisted of 112 13 MAS 505/5 cells, divided fore and aft of the main diving tank in seven rows of eight cells per unit. The diving and trim tanks were internal to the pressure hull, as were the diesel fuel oil bunkers, for a fluid volume of only 23 cubic meters. The performance of the boats was respectable: 1600 nautical miles surface range at 5 knots, which translated into a tactical operating radius of some 500 to 800 miles; a maximum submerged speed of 5.5 knots and ten hours submerged duration at 4 knots; and because of the small upper superstructure with large limber holes and numerous ballast tank vents and inlet valves, the boats could submerge in only 22 seconds.
Rather than having movable bow diving planes, the half-spade shaped fins were fixed at a downward angle and the deck casing limber holes were more closely spaced forward of the conning tower to create a natural bow-down angle and submerge the planes immediately on opening the ballast tank vents. Forward momentum of the boat would further force the bow underwater as the propulsion was shifted from diesel to electric. The movable stern diving planes (sometime referred to as horizontal rudders by the British) were proportionally oversized as compared with the planes on larger U-boats, thereby giving sufficient control authority to adjust the attitude of the boat. The boat could be operated with a slightly positive buoyancy, and as long as the motors provided forward propulsion the fixed bow planes would keep the bow down, but if speed was decreased, the bow would naturally rise even without putting a rise on the stern planes.
The armament of the boats was very primitive, limited to the two bow 45 centimeter C03 torpedoes (with no reloads, though some drawings seem wishful in indicating a spare being carried this just does not seem feasible) and an 8mm machine gun mounted on the forward deck casing. Photographic evidence seems to suggest that some boats were later fitted with a small-bore cannon in place of the machine gun, however deck space was very limited, making a crew-served weapon very impractical. Photographs also suggest that the machine gun was seldom fitted. Some of the boats were fitted with the distinctive bow net cutters.
The contract for construction of fifteen boats was signed on 15 October 1914: UB 1 through UB 8 from Germaniawerft in Kiel, and UB 9 through UB 15 from AG Weser in Bremen. On 25 November, two additional boats, UB 16 and UB 17, were ordered from AG Weser because a decision had been made to hand over UB 1 and UB 15 to the Imperial Astro-Hungarian Navy (KüK Marine) for Mediterranean operations. These boats became U-10 and U-11, respectively, and the KüK Marine also ordered and took delivery of three additional boats which became U-15 - 17.
While the two sets of boats conformed to the same general specifications, they differ in some details, such as the profile of the aft deck casing, the conning tower angles, the stern cone and lower rudder fairing, and the tower deadlights. Nothing is known concerning the origins of these differences, however it seems likely that they may have been for any of three reasons: the detail drawings may have been finalized by each yard independently; experience with the first series may have dictated the changes; or it may have been for tooling reasons. It is interesting to note that the Germaniawerft boats used the few available Daimler diesels, while the AG Weser boats (including the mine laying adaptation, the UC I type, which were built by AG Weser and AG Vulcan of Hamburg) used Korting diesels. Also, the details of the UC I type appear to derive directly from the AG Weser UB I boats.
The actual construction time of the boats was incredibly short. The lead boat, UB 1, was completed at Germaniawerft on 22 January 1915, only 109 days after the contracts were signed and 75 days after the keel was laid. The class construction program was totally completed by 21 April 1915. Even the more complex UC I type mine layers, with their greater displacement, a six-cylinder diesel, and correspondingly larger motors and storage batteries, only required four months each to complete.
Detailed Differences between the 17 boats
The 17 boats differed in many small particulars. The following is an "Audobon Guide" to the UB I Type boats, prepared in large part to the research efforts of Tom Koehl. It may assist you in identifying an image you find (which you should please share with me).
Here are some primary differences between various units of the UB I Type. Tom Koehl pointed out that the most vital determinant of which boat had which characteristics is likely attributable to whether it was manufactured by Germaniawerft in Kiel (as were UB 1 through UB 8) or by AG Weser in Bremen (as were UB 9 through UB 17). The links in the table below show images of submarines illustrating the various appearances, but you will find discrepancies between them (e.g.: one image purportedly of UB 2 shows large vent holes and another shows small vents), and this is most likely due to inaccurate identification of the boat in the image though one might leave open the possibility that alterations were made after the boats were first launched.
Taking into account the very real possibility that a number of the identifications in the photos are incorrect, I think a few generalizations can be made. Germaniawerfft boats UB 1 through UB 8 had large vent holes and tended to carry their forward dive planes in a higher position on the hull. AG Weser boats UB 9 through UB 17 used small vent holes, and over time a preference for more holes was made to favor speed of diving over highest possible underwater speed (the more numerous the holes, the quicker the deck void floods but the greater the underwater drag). Other, more subtle or transient point sof difference between boats might be found in the placement and angling of the forward dive planes, with some carrying these higher on the hull than others, and paint scheme (light gray vs dark vs camouflaged, with or without eyes and a mouth for good luck and/or fun). Careful inspection, of course can reveal even differences in the way the eyes were painted -- part of the fun of studying boats built in such small numbers.
Errata on 3D model
Tone developed the 3D model from the Lothar Wischmeyer plan drawn in 1984. It is labelled as UB 16, and though it does appear to be redrawn from original dockyard drawings (Eberhard Rossler has a nearly identical drawing in one of his books) but has several errors, some of which are wrong for any completed boats for which I have seen images. His plan shows the ladder on the starboard side of the conning tower (no photos showing the ladder indicate this, but for the photos I have which seem likely to depict UB 16 this detail cannot be seen), so I suspect that this detail is wrong in his drawing. But most tellingly, the drawing clearly indicates the large vent hole pattern common to the Germaniawerfft boats which cannot be right for UB 16.
I took the liberty of placing my own ladder on the port side where it seems to belong, as did the unknown builder of this physical model, but we both made the mistake of using the large vent holes (I discovered the pattern of this variation after completing my work).
UB I CLASS DEPLOYMENTS
At about the same time that the UB I and UC I type boats started coming off the builders ways, the political pressures against Germany’s unrestricted submarine warfare campaign, as well as the British offensive in the Eastern Mediterranean, prompted the High Command to split the operational assignments of the boats between the North Sea and the Adriatic. Using four flat cars per boat, the Flanders-bound boats were transported in sections by rail to the yards equipped with cranes capable of lifting the 127 and 168 tons of the UB I and UC I boats, respectively. German technicians assembled and tested the boats for watertight integrity, pressurizing the hull interior with air to 50mm of mercury overpressure. The boats were then towed through the Scheldt and the Ghent-Bruges Canal to the base at Bruges. This operation, using tugs and caissons (pontoons) to minimize the boats’ draft, took 5-1/2 days.
For the Mediterranean-bound boats, rail travel all the way to the Stenia Yard at Constantinople was impossible because of the differing track gauges and tunnels through the numerous mountain ranges. The only solution was to assemble the boats at the Austro-Hungarian base at Pola (now Pula) on the Adriatic, then make the remainder of the journey by sea. Proven sea-worthy, six boats eventually undertook this journey.
THE FLANDERS FLOTILLA
The Flanders Flotilla was formed on 29 March 1915 under the command of Kaptain Paul Bartenbach, who, before the war, had commanded the pioneering cargo submarine U-1. The mission of the flotilla was very specific: harass the cross-channel traffic and coastal shipping in the North Sea, directly by torpedo attacks and indirectly by sowing mine fields. The following boats were assigned to Bruges:
UB 10, 12, 16 and 17 were converted to UC I type mine layers in late 1916/early 1917. The boats’ overall length was increased to 105 feet and four mine tubes for eight mines were fitted in place of the two torpedo tubes (in contrast to the six tubes and twelve mines in the original UC I type boats). Their size increase was limited by their smaller propulsion plant. The Flanders Flotilla was also assigned the conventional mine layers UC 1 through UC 11.
THE MEDITERRANEAN FLOTILLA
The boats destined for Mediterranean operations were transported to the Adriatic base of Pola to operate with the Kaiserliche und Koeningliche Oesterrich-Ungarisches Seearsenal (KüK Marine, or Imperial Austro-Hungarian Navy). Assembly was completed in Floating Drydock “T” by German technicians, the boats were pressure-tested and then assigned to either the German Navy or KüK Marine.
In addition to the UB I type boats and KüK Marine submarines operating out of Cattaro, UC 12 through UC 15 were transported to Pola to complete U-Flotilla Mittelmeer (Mediterranean). To harass the British forces off Gallipoli and Russian shipping in the Black Sea, a half-flotilla (U-Flotilla Konstantinopel) under K/Lt Otto Hersing was assigned to Varna, on the western shore ofthe Black Sea. It was originally thought that several boats could be sent to Constantinople by rail, but when this proved to be impractical, as mentioned earlier, UB 3, 7 and 8 as well as UC 14 and 15 were ordered to make the voyage by sea. The latter four boats arrived safely, however, UB 3 disappeared in the Aegean off Smyrna on 23 May, or shortly thereafter, probably the victim of a drifting mine or accident.
The fact that until 1 August 1915 only Austria-Hungary was at war with Italy placed Germany in a delicate diplomatic position, particularly because the German commanders lost no time in attacking Italian shipping. The immediate solution was to nominally transfer “Seiner Majestaets Unterseebooten” to the KüK Marine. In point of fact, UB 1 and UB 15 were officially transferred as U-10 and U-11 before they were even completed. Three additional UB I boats were ordered from AG Weser (U-15, 16 and 17) to compensate the KüK Marine for five larger ocean-going boats then under construction in German yards but taken over by the Kriegsmarine.
The UB I type submarines, in spite of their small size, must be considered a great success. Fully ten of the seventeen submarines (twenty, if the KüK Marine boats are included) survived the war to be surrendered and scrapped after evaluation by the Allies, including the lead boat, UB 1, which had a distinguished career as U-10 of the KüK Marine.
Related Reading: UC 5 and the UC I Type
While I have no models on the site for the UC I boats, Tom has transcribed reports made by Britain when she captured UC 5. Since this type is so closely related to the UB I type, I decided to post the reports and a short cover page here.