O.Thetford, P.Gray German Aircraft of the First World War (Putnam)
Oertz W 4
A series of twelve living-boats was built by the Hamburg Yacht firm of Oertz: FB 3 a pre-war design which bore the Naval number 46, W 4s 63 and 75 of 1914, W 5s 276-280 of 1916, W 6 Flugschoner 281, W 7s 474-475 and W 8 1157.
All these aircraft featured engines buried in the hull and driving pusher propellers through a system of geared shafts. Dipl. Ing. Max Oertz gave special attention to hull design, providing sufficient beam to give adequate lateral stability on the water with no more than spring-loaded hydrovanes at the wingtips to prevent them submerging. A feature of the earlier machines was that the chord of the lower wing was considerably greater than that of the upper wing; it was also greater in span, with consequent inward rake to the interplane struts. The ailerons were also on the lower wingtips.
Flight, October 9, 1919.
THE OERTZ FLYING BOATS
[THERE is little doubt that the development of commercial aviation will be closely allied with the progress made in the production of seaplanes, especially as far as the British Empire is concerned. It is, therefore, of interest to know what has been done until now by others as well as by ourselves, and we think that the following notes, translated from Flugsport, dealing with an interesting series of flying boats designed and built by the Oertz Works at Hamburg, may be of interest. This factory was, before the War, chiefly concerned with the building of yachts and motor boats, corresponding, in a way, to our Saunders Works at Cowes.-ED.]
"The fight for existence between the flying boat and the float seaplane commenced in the very earliest days of seaplanes. Even now the final decision as to whether the flying boat or the float seaplane offers the best solution for aerial transport over the sea has not been made. The experience gained during the War cannot straightaway be applied to peace conditions. At the moment the flying-boat people naturally have the last word, since a flying boat was the first to cross the Atlantic safely. After the questions of weight and air-resistance, the most important point in the evaluation of the advantages and disadvantages of the two types is that of sea worthiness. By this is meant the possibility of getting off and alighting with a certain amount of sea running, and also to be able to 'live' when on the surface in rough weather. The performance required is in direct opposition to the qualities of seaworthiness, since a seaplane, to be seaworthy, must necessarily be of very substantial construction, which can only be provided at the cost of a fairly heavy weight of the hull and machine.
"Next, it would appear that the float seaplane would be superior to the boat seaplane in the matter of seaworthiness, since the boat has a very low freeboard, and, therefore, will be more likely to be swamped while taxying than will the float seaplane. Moreover, the lower plane of a boat seaplane is much nearer to the water than is that of a float seaplane, so that there is more likelihood of it coming in contact with the sea. It will, therefore, be seen that the difficulties that beset flying-boat constructors are by no means small.
"With regard to the questions of weight and air resistance, it must be said that the flying boat is more favourably placed in both respects. Although for powers of 150 to 240 h.p. the weight of the two types does not differ greatly, the advantages of the boat seaplane increase with size. Thus, a float seaplane of 1,000 h.p. will be about 4,400 lbs. heavier than a boat seaplane of the same power.
"From the point of view of air resistance, the fact that a float seaplane has a fairly extensive strutting arrangement for the floats, while the boat seaplane can be made of fairly good stream-line shape, gives the boat type a smaller resistance than that of the float type, even when, as is sometimes the case, the engine of the boat seaplane is placed on a structure above the boat proper.
"After balancing up the pros and cons, of the case, taking into consideration the practical experience of the Navy, one arrives at the conclusion that the flying-boat type, as regards medium and large-size machines, is superior, also as regards seaworthiness. For types of up to about 300 h.p., possibly the float seaplane will be found the most suitable, while for types of from 300 h.p. to 700 h.p., there would seem to be little to choose. For larger types, however, the flying boat type appears to be the most promising. The chain of experience of both types is not, however, sufficiently long to make it advisable to decide finally for one type or the other.
"Among the most successful, and, therefore, most noteworthy, flying boats, are those designed by D. Ing. Max Oertz, which were built at the Oertz Works at Hamburg. Dr. Oertz, the famous yacht and motorboat builder, was one of the first in Germany to realise the possibilities of flying and the suitability of his works, with their special facilities and trained workmen specialists, for the requirements of aircraft construction. Above all, the Oertz Works were not laid out as quantity production works, but were used to meet the special requirements of yacht construction by scientific investigation into the smallest mechanical details, and to devote an absolutely loving care to workmanship and finish.
"These fundamental facts, which were reflected in all new productions of this scientifically working factory, whether boats or flying machines, could already be noticed in the very first machine built in 1910. This was a land machine, a monoplane with monocoque body, which weighed only 770 lbs., and, fitted with a 70 h.p. Gnome engine, reached a speed of 80 m.p.h. This first success encouraged Oertz to return to his proper element, the sea, and to apply the same principles to the construction of a flying boat; this was ordered by the Navy in the spring of 1913. Already in the autumn of the same year this flying boat could show its usefulness by successful test flights at Breitling, near Warnemunde. This machine, which is shown in Fig. 1, was fitted with a 100 h.p. Argus engine placed down in the boat, and driving the airscrew through shafts and bevel gearing. Tins arrangement, the constructional details of which had been worked out by Dr. Oertz himself, was something quite new for those times, and this first boat already showed the characteristics of all later Oertz flying boats. Among these is, chiefly, the division of the planes into two halves and the slanting struts, with means for quickly dismantling the complete plane cellule. In looking at this flying boat, the thing which at once attracts notice is the very large chord of the lower plane, compared with that of the top wing. The object of this arrangement was to raise the centre of pressure of the biplane, and thus reduce the undesirable pendulum effect caused by having the engine in the hull. The objections to this effect have, however, later proved to be of small importance.
"One of the greatest difficulties of that time was to design a boat hull which should have the greatest possible amount of lateral stability when on the sea. The French flying boats of that date had very narrow hulls, which necessitated fitting auxiliary floats to the lower wings. In anything of a sea, these wing floats were a constant danger to the plane, owing to the shocks and stresses set up. It was in this respect that the art of the experienced yacht builder came to the rescue. Oertz provided a boat hull, which not only had a very good stream-line form, but which also possessed a very great amount of lateral stability on the sea; so much so that it was possible for a man to walk half-way out on the lower plane without the machine heeling over enough for the plane to touch the sea. This great lateral stability on the sea has remained one of the features of all Oertz flying boats to this day. The credit of being the first to provide this lateral stability is not in the least reduced by the fact that the American Curtiss flying boat, which was used in the Transatlantic flight, shows the same feature. In order to reduce the danger of the lower wing tips cutting under when the machine is rolling in a sea or taking off, the lower wing tips were provided with flat spring boards which prevented, by their dynamic action, the tips from cutting under. These spring boards are shown in illustrations 1 and 2.
"Already at the first attempt the boat flew well, and proved the soundness of its design. Especially was the transmission found to work well, although, on account of trouble with the engine itself, no flights of very long duration were attempted. The first boat was perfectly smooth, that is to say, it had no step. In order to improve the getting off, experiments were then commenced on hulls provided with step. The first boat of the stepped type appeared in the spring of 1914, and is shown in Fig. 2. The machine was fitted with the first 160 h.p. Daimler engine. The photograph shows the general graceful lines of the hull and the large lower plane, which has upturned ailerons, after the manner of the old Tauben. The illustration also gives a good idea of the slanting inter-plane struts which, like those of the Hansa machines, gives equal distances between supports in upper and lower planes. On account of the late arrival of the engine, the boat was not ready for its first trial flight until two days before the great Warnemunde race planned for August of that year. All those who took part in the preparations for that race, which was postponed owing to the outbreak of War, will still remember the splendid and startling performance of this boat, which was piloted by the late pilot Stagge, who, by the way, had never flown a seaplane before. This, however, did not prevent him from doing a series of stunts on this machine. So absolutely 'right' was this boat, that it could be taken over by the Navy without any alterations whatever, and not long afterwards, piloted by Stagge, it was flying over Dover. Later boats of similar type are shown in Figs. 3 and 4.