The major Dutch submarine builder before the Second World War was the shipyard Kon. Mij. De Schelde established in 1875 at Vlissingen, Netherlands. She built the first Dutch submarine Hr.Ms. O1 (former Luctor et Emergo) in 1904-1906 using an American Electric Boat Company-design. The original was improved in the next years. In advance there were two types of submarines, a smaller type for the Dutch coastal waters the ‘O’-series and a larger type serving in the Dutch East Indies, the “K’ series. Except for a former German submarine minelayer interned in the First World War and later purchased by the Netherlands, there were no submarine minelayers in the Royal Netherlands Navy until the O19 and 20 which were fitted out with 20 vertical mine tubes each filled with 2 mines. Both were commissioned in 1939. That does not mean that the Royal Netherlands Navy was not interested in submarine minelayers. The First World War was even ended when a Dutch military delegate collected all information available and dealing with such submarines. However it seems that the navy did not use the information except perhaps for the navy engineer Maximiliaan Fredrik (1895-1972), chief drawing room of the shipbuilding office. He was the men behind the Dutch successful 3-cylinder submarine project realized after the Second World War. In 1926 he was appointed as chief naval shipbuilding of the Kon. Mij. De Schelde and he became responsible for designing a small single hull submarine minelayer. The design was worldwide in countries like Japan, USA, Poland and Sweden between 1929-1934 protected by patents. Still hardly is anything information preserved except for a brochure, some photographs of a model of a half cross-cut of the hull on actual size and some small references in documents.
Source: Archive Kon. Mij. De Schelde (Towns Archive Vlissingen, Netherlands T513.2214) dated March 1933
It is not impossible that Gunning made his designs in deliberation with the NV Ingenieurskantoor voor Scheepsbouw (IvS) at The Hague, Netherlands. This was a dummy company set up by the former German Imperial Navy after the First World to protect and even improve the German submarine knowledge and joined by the German shipyards AG Vulkan, Germaniawerft and AG Weser. IvS designed and even built submarines for the German navy and countries like Russia and Turkey.
Source: original brochure showing the general layout in fig 1.￼
There seemed to have made several designs of the Schelde-Gunning submarine. In contrary to what was common, were the main ballast tanks not placed in longitudinally direction but transversely leaving a s mall built-in passage needed to go from bow towards stern en versa. The result was that she was shorter and broader than ordinary submarines, but in many respects superior according to the brochure. She could be very cheap and quickly be built while her construction was simplified compared with the common design with the longitudinally tanks. The available sketch is that of a 650 ton submarine. At that moment was the shipyard building submarines like the unlucky Hr. Ms. O13, laid down in October 1928 and commissioned on 8 November 1930. With as dimensions 60,6 (over all) x 5,40/5,75 x 5,72 x5,04 (hold) x 3,60 metres and a displacement of 555 (standard)-576,9 (surfaced)714,9 (submerged) tons. Diving depth 60 metres. In fact qua size quite comparable with the Schelde-Gunning design.
The main ballast tanks were to be used for storing the mines. One simple option was in vertical rails and launched through watertight hatches in the bottom of the tanks. Problem is that every time the submarine dived the mines became wet and needed to be regularly examined on shore. A more complicated but far better solution was to place the mines in pressure-tight vertical cylinders and maintaining continuous dry. For instance the Sautter Harlé mine with a 440 lbs explosive charge could be when using the cylinders. After removing the upper covers of the cylinders was filling possible with the use of a crane. When the mine were to be launched were the cylinders filled water stored in filling tanks. A safety device secured a correct launching sequence and further more was mechanically indicated how many mines were launched. If the cylinders were not used for storing mines could they be used to store for instance ammunition. The number of mines was not specified, just called large. The above mentioned O19 was fitted out with 20 French designed mine tubes each with 2 Vickers mines.
Despite the qualities mentioned in the brochure was this submarine not built. In 1932 was the shipyard negotiating with the S.A. des Ateliers&Chantiers de La Loire at Paris, France which latter firm was interested in license-building. In the concept contract is spoken from displacement varying between 500 and even 1.200 tons. As far as known is this license never realized.
The same year tried the Dutch shipyard to obtain a large Portuguese order consisting of the building of submarines and aviso’s. In the letters written by Gunning to his board becomes clear that a submarine layer was offered. The order was finally given to the British firm Vickers. In the same period asked the Royal Netherlands for tenders to built a submarine (Hr. Ms. O 16) using official navy plans made by naval engineer G. de Rooy. The De Schelde reacted with two tenders, one when using the navy plans and one using their own design. Obvious were the differences in building prizes. For the navy design 1.355.000 Dutch guilders or 1.231.000 without battery and for the submarine minelayer respectively 1.325,000 and 1.201.000 Dutch guilders. Still the Royal Netherlands Navy choose for their own design and not for the submarine minelayer. But at the same time she wrote an important letter to the shipyard. Namely that their choice for a conventional design had nothing to do with the quality of the disapproved design. The remarks the Dutch Admiralty could made were without meet by the shipyard with alterations. But still was the design not accepted.