Flight, August 28, 1919.
THE E.L.T.A. SHOW
The only other Dutch machine exhibited is that built by
VAN BERKELS PATENT, HOLLAND.
This is a twin-float seaplane, shown at the exhibition without engine, but intended, we believe, for a Mercedes. The fuselage is built up of a light framework covered with three-ply wood. The ply-wood covering of the rear portion of the fuselage is continued outwards over the tail plane, which latter is built integral with the body. The fuselage is very deep at the rear, where as a matter of fact it performs the function of a fin, no other vertical fin being fitted. As the tail plane is at the top of the fuselage the whole tail looks somewhat unusual, especially as the rudder has its balanced portion projecting below the stern instead of, as in the majority of machines, above it.
The two floats, which are of the single step type, are flat-bottomed as regards their front portion, but to the rear of the step the bottom gradually changes from flat to Vee bottom, finally corning to a point at the heel of the float. The construction is very similar to that of the fuselage, brass screws and nails being used throughout. The floats are, of course, fitted with water-tight bulkheads, easily detachable inspection doors being provided in the deck for examining the interior.
The wing bracing of this seaplane is unusual, in that there is only one pair of struts on each side, in spite of the comparatively large span. The upper plane is of slightly greater span than the bottom one, and the inter-plane struts slope outwards to obtain the best load distribution on the respective spars. The lift and landing loads are taken by tubes sloping from the floats outward to the lower surface of the bottom plane at the points where occur the inter-plane struts. As the float strut formation is in the shape of a letter M, as seen from in front, and having a transverse horizontal strut between the floats, the outward component of the lift pull on the sloping struts is transmitted to this horizontal strut, which is therefore in tension when the machine is flying, and probably in slight compression when the machine is at rest. We understand that this machine has not yet flown, but a speed of 155 km. per hour is estimated for her.
Another exhibit on this stand which attracts attention is a small 8-cyl. rotary engine of the two-stroke type. It was, we learn, designed by Mr. Kerner, of the technical staff of Van Berkels. Its chief feature is that, in order to avoid the trouble experienced in all two-stroke engines at certain speeds - either a mixing of the fresh charge with residual gases, or a waste of fuel through blowing part of the fresh charge out through the exhaust ports - a small piston disc is interposed between the fresh charge and the exhaust gases, thus preventing them from mixing, while at the same time being limited in travel so as to prevent the escape of the fresh gas through the exhaust ports. This piston disc is mechanically operated, but we were unable to ascertain the details of the mechanism. The Kemer engine is provided with external inlet pipes, and very large inlet valves are fitted in the cylinder heads. We understand that the engine has passed through satisfactory test runs, and it is claimed to develop 120 h.p. for a weight of 95 kgs.