The method here described has some advantages over the present standard method of designing with continuous spars. Firstly, it gives lighter spars by working as many points as possible up to the elastic limit. Secondly, it is far quicker to use owing to the necessary formulæ and processes of computation being more manageable and to the fact that practically each bay can be designed separately without affecting the others. Thirdly, the roughing out and the final checking are done with the same set of formulæ, whereas, if the usual type of spar construction is adopted, it is necessary to use different methods for the preliminary and final design. Fourthly, the accuracy of the work is not affected by the supports getting out of line when the whole structure deflects under load, a serious error in the older method being thus avoided.

During the war a heavy demand was made on the supplies of aeronautical timber, and in order to allow of the use of smaller sized timber, it became necessary to permit the introduction of splices into aeronautical construction. We knew of no means to obtain accurate comparative data, and the purpose of the present inquiry (with which Captain K. Robertson was also associated) was that of finding a method of splicing timber beams which should prove to be the most effective for withstanding bending moment (as in aeroplane main plane spars) and which should at the same time be simple to produce and easy to inspect.

As a preliminary step we invited suggestions from aircraft constructors and others as to the forms of splices which, in their opinion, were likely to give the most useful results.