The first group of a large series of contemplated experiments on the effect of roughness was intended to show the effect of great roughness on airfoils of various sizes and attitudes.

Experiments on the effect of atmosphere and of sea water on the building materials employed by us have been carried on for years in the North Sea with the aid of the Hamburg Naval Observatory. Parallel experiments are being made at the Pisa Naval Observatory in the Mediterranean Sea. Metal sheets, sections, assemblies and experimental floats are being exposed to the action of the elements. Different construction techniques are discussed and a variety of specific airplanes are presented which incorporate some of the new thinking.

Memorandum presenting an overview of the development of light and small airplanes. Some of the characteristics explored include the development of airplanes of medium weight, development in countries other than Germany, development of light airplanes, general constructive fiducial lines, safety problems, the economy problem, and some special structural considerations are provided.

"The most usual method of arriving at the maximum amount of spindling or hollowing out permissible in the case of any particular spar section is by trial and error, a process which is apt to become laborious in the absence of good guessing - or luck. The following tables have been got out with the object of making it possible to arrive with certainty at a suitable section at the first attempt" (p. 1).

This report is an evaluation of the experiments on the use of heavy oils in explosion engines. A method for determining the heat of vaporization of these heavy oils is presented.

Memorandum presenting a description of some of the speeches made at the fifteenth regular meeting of the Wissenschaftliche Gesellschaft für Luftfahrt. Many of the speeches were conducted on aircraft design and construction, but some covered topics like statistics.

The object of this report is the description of a method which seems to be practicable for determining the path of an airplane, especially in taking off and landing. This report tells how, by means of a camera, preferably a kinetograph, which simultaneously photographs a stop watch the distance of an airplane from the camera and its height above the ground can be determined.

This report presents a theoretical treatment of the vaporization process of medium and heavy oils. The results of this investigation, which were mostly obtained from the lighter components of the heavy fuels, require a 10- or 16-fold vaporization in comparison with gasoline. We must attain a still finer degree of atomization, in order to include the heavier components.

"In undertaking to analyze the functioning conditions of a reduction gear on an aviation engine, we will consider an ordinary twelve-cylinder V-engine. The reduction gear employed consists either of a pair of spur gears, one of which is integral with the engine shaft and the other with the propeller shaft, or of a planetary system of gears" (p. 1).

Report presenting an investigation of the phenomenon of knocking in gasoline engines and some of the problems that it may cause. It is of the greatest importance, not only for automobile engines, but also for every other kind of internal combustion engine, since it limits the degree of compression and the thermal efficiency and its investigation indicates ways for saving fuel.

Now that the two-stroke-cycle engine has begun to make its appearance in automobiles, it is important to know what services we have a right to expect of it in aeronautics, what conditions must be met by engines of this type for use on airplanes and what has been accomplished.

This report describes the layout of the laboratory along with the motor and balance for the wind tunnel.

"We propose to show how to calculate the cooling capacity of all radiators through which the air flows in separate streamlets, whether enclosed in actual tubes or not and whatever cross-sectional shape the tubes may have. The first part will give the fundamental principles for calculating velocity of air in the tubes and the heat exchange by radiation, conduction and convection, and show, by examples, the agreement of the calculation with experiments. In the second part, the effect of the dimensions and conditions of operation on the heat exchange will be systematically investigated" (p. 1).

The use of duralumin by French airplane designers is presented, the results they have obtained, and their hopes for the future.

This report examines the cause and effect of the energy conversion in airless-injection engines. In order to obtain a criterion for the chosen working method, it takes into consideration the time relations between the individual processes. Observations of the engine alone do not suffice to obtain the necessary basis for a critical analysis of the processes.

Experimental data, such as the results of tank tests of models, render it possible to predict, at least in principle, as to how a hull or float of a given shape will comport itself. We will see further along, however, how uncertain these methods are and how they leave room for empiricism, which will reign for a long time yet in seaplane research bureaus.

The test equipment for studying the vaporization of heavy and medium oils is described as well as some of the experimental properties explored such as vaporization speed and diffusion coefficient. The experimental arrangement is also discussed.

"Our attempts to improve the properties of airfoils by removing the boundary layer by suction, go back to 1922. The object of the suction is chiefly to prevent the detachment of the boundary layer from the surface of the airfoil. At large angles of attack, such detachment prevents the attainment of the great lift promised by the theory, besides greatly increasing the drag, especially of thick airfoils. This report gives results of those experiments" (p. 1).

This report presents methods by which the cells of large commercial airplanes may be reduced. The tail of large airplanes represent an area where considerable improvement in weight and size reduction can be attained.

Memorandum presenting two principal methods of mixing for carburetor engines, one using a suction carburetor and the other using a pressure carburetor. An investigation of the spark plugs in the engines and how to design them so they can resist high levels of heat is also provided.

The Behm acoustic sounder for aircraft enables the barometric determination for the altitude by night or fog and therefore promises to prove of great importance in safeguarding air traffic.

The objects of the experiments herein described were to test the protection afforded by Valspar oil varnish against the absorption of moisture by wooden airplane parts and the consequent changes in their elastic properties and to compare some of the best Dutch varnishes with Valspar.

In the construction of aerodynamic tunnels, it is a very important matter to obtain a uniform current of air in the sections where measurements are to be made. The straight type ordinarily used for attaining a uniform current and generally recommended for use, has great defects. If we desire to avoid these defects, it is well to give the canals of the tunnel such a form that the current, after the change of direction of its asymptotes, approximates a uniform and rectilinear movement. But for this, the condition must be met that at no place does the flow exceed the maximum velocity assumed, equal to the velocity in the straight parts of the canal.

The advantages of the Kirsten-Boeing propeller consist essentially in the adjustability of the thrust in any desired direction, in the plane perpendicular to the axis of rotation of the system, and in its high efficiency. The propeller, which greatly resembles the paddle wheels used on river steamers, differs fundamentally from the latter, in that all the blades work simultaneously in the fluid medium (air or water).