J.Herris German Seaplanes of WWI (A Centennial Perspective on Great War Airplanes 15)

Oertz W6 Flying Schooner
  
  The Oertz W6, known as the Flugschoner (Flying Schooner), was ordered in August 1914 but was not delivered until July 1917. The W6 was easily the most distinctive Oertz flying boat due to its tandem biplane wing design. This configuration was chosen to provide great wing area within a reasonable wing span. The W6 was powered by two 240 hp Maybach Mb.IV engines mounted in the hull driving the pusher propellers via shafts with bevel gears as in previous Oertz designs. Originally, ailerons were mounted only on the forward upper wing. These proved inadequate and an additional pair of ailerons was fitted between the aft pair of wings.
  Other than its tandem wings, the W6 closely followed the configuration of earlier Oertz flying boats. The hull was broad-beamed, the engines were hull-mounted driving pusher propellers, and the tail surfaces were carried high above the hull. Originally wing-tip floats were not used, but these were added based on flight experience.
  The W6 was significantly larger than earlier Oertz flying boats and carried a crew of three. Only one aircraft, Marine Number 281, was ordered and built.


Oertz W6 Specifications
Engine: 2x240 hp Maybach Mb.IV
Wing: Span 20.00 m
Area 162.7 m2
General: Length 14.58 m
Empty Weight 3,780 kg
Loaded Weight 5,030 kg

M.Dusing German Aviation Industry in WWI. Volume 2 (A Centennial Perspective on Great War Airplanes 85)

Max Oertz, Jachtwerft, Neuhof-Reiherstieg (Hamburg)
  
Foundation:

  Max Oertz, a builder of high-quality sailing yachts, began designing aircraft in 1909. Later he took over the contract manufacturing of some Wright biplanes for the Berlin company, which in return provided the distribution of the monoplane designed by Oertz.
  Max Oertz designed his first powered aircraft as early as 1909, and the first closed aerodynamic fuselage in 1911. Max Oertz designed several flying boats for the Navy and maintained his own airfield in Schneverdingen for test flights. Most of the known aircraft were flying boats, of which the Oertz W6 Flugschoner was particularly striking, a tandem biplane with an additional conventional tailplane and double rudder. The two Maybach engines were housed in the elegant boat hull and drove the propellers via long-distance shafts. Prince Heinrich of Prussia supported him, and the Reichs-Marine-Amt (RMA) also took over some flying boats.
  But around 1917, the company was incorporated into the “Hansa-Brandenburg” company.


Aircraft Development:

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  The appearance of the large fast American Curtiss flying boats in the War gave the impetus for us also to start construction of large boats to a considerable extent. In connection with the Brandenburg Aircraft Works, the construction of two large flying boats with two 300 hp engines were commenced. The hulls of these boats were already finished when the Armistice came, but the work on the complete boats was then stopped.

Журнал Flight

Flight, October 9, 1919.

THE OERTZ FLYING BOATS

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   "Already at the outbreak of war, Mr. Oertz was considering the design of large flying boats. In order to reduce the overall span of large machines, which may, under certain conditions, be a great disadvantage at sea, he evolved the, in itself, quite novel idea of constructing a tandem machine. [This is incorrect. The tandem machine had already been considered, and, in fact, several had been built, although they could hardly be said to be very successful. - ED., FLIGHT.] After model tests by Professor Prandel at the Gottingen Laboratory, the construction shown in Figs. 7 to 10 was decided upon, and the boat was finished in 1916. It was given the official, and more seamanlike, title of 'The Flying Schooner.' The 'Flying Schooner' had two 240 h.p. Maybach engines, placed side by side, and attained a speed of about 71 m.p.h., which was better than the speed predicted by Gottingen. The 'Flying Schooner' was especially good for starting and alighting. In order to enable it to make shorter turns, inter-plane ailerons were fitted between the rear planes. These have not yet been fitted in the photograph, Fig. 8, but may be seen in Figs. 9 and 10.
   "The appearance of the large fast American Curtiss flying boats in the War gave the impetus for us also to start construction of large boats to a considerable extent. In connection with the Brandenburg Aircraft Works, the construction of two large flying boats with two 300 h.p. engines was commenced. The hulls of these boats were already finished when the Armistice came, but the work on the complete boats was then stopped. May it be resumed again for the benefit of peaceful development."