It is shown that weight can be saved, and stiffness gained by a proper choice of the design, that is the type of frame of any truss. A method is developed first to choose the best among several statically determinate designs. It is then demonstrated that, when a redundant truss has to carry one set of loads, it is always possible, by the removal of some bars, to get a statically determinate truss which is lighter, for the same ultimate stress. But the redundancy keeps its advantages when the structure has to carry several sets of loads in turn.

The following Paper comprises some of the results of an investigation originally undertaken by the writer to determine the effects of the humidity of the atmosphere and other secondary factors upon the static lift of airships. It is almost invariably found on completion of such a craft that a considerable deficiency is revealed between the designed lift and the apparent value deduced, for example, from a “ lift and trim ” trial. Clearly, it is of considerable importance that the reason for this discrepancy should, if possible, be determined; for whilst the loss may be only a small percentage of the total displacement of the ship, and hence difficult to trace, yet considered in terms of disposable lift, it frequently is very serious.

The rapidly extending employment in many industries of cold pressing and stamping operations in the production from sheet metal of a great variety of components, embracing both simple and very complex shapes, renders cold pressing an extremely suitable subject at the present time for a joint discussion by a group of technical societies representing a wide range of industries. The particular interests of these industries naturally vary widely, both as regards type of production and the materials employed, but there should exist many basic problems common to all.

There have recently appeared a number of papers and notes bearing on the merits of turbo-prop vis-a-vis turbo-jet transport aeroplanes, mostly exhibiting specific favour towards one type or the other, but disagreeing among themselves and all based upon investigations which, it is contended here, are incomplete.

The basis used has invariably been a comparison of the relative direct operating costs per unit of weight (i.e. per passenger or per ton) per mile, and the relative earning capacities have not been considered. This, it is believed, is a serious omission which can only lead to a distorted assessment and erroneous conclusions.

The author has been associated with a thorough-going investigation into the relative merits of twin-engined turbo-prop, turbo-jet, and reciproeating-engined aeroplanes, all designed on a strictly comparable basis to do, as far as the performance of suitable available engines would allow, the same job in terms of capacity payload and associated operational stage length, take-off and landing performance and one-engine-inoperative climb performance in given atmospheric and altitude conditions.