FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1926
1926 - 0058.PDF
10 SUPPLEMENT TO FLIGHT JANUARY 28, 1926 THE AIRCRAFT ENGINEER adds to its compressive strength and reduces the amount of internal stiffeners required inside the hull; thus reducing detail work and effecting a saving of labour costs. In considering such future prospects, steel has an advantage in that it may be welded, if such a method of joining is found to be desirable, also it may be of the rustless variety. On the other hand, we may reasonably expect that the science of metallurgy will make progress in the development of light alloys, eliminating the tendency to corrosion, and increasing" its tensile and compressive strength. Already we have new alloys of considerable strength, and not much more than half the weight of aluminium, which even at the present time might be used for some secondary parts of aircraft. But, to revert to the present uses of Duralumin, its appli- cation with advantage is not confined to the purely monocoque type of construction in metal. It possesses distinct advant- ages over steel for rib construction, because in such necessarily ing figures give the results of this test, and the weight of the spar :— Maximum test load, 4'8 times normal load, plus structure weight. Maximum stresses realised in overhang, 38,000 lbs. per sq. in. Maximum stress in inner bay, 40,200 lbs. per sq. in. Removal of load showed a slight permanent set around the fitting, but no indications of the spar failing. Maximum end load in inner bay, 33,000 lbs. Maximum bending moment in overhang, 455,000 in.- lbs. Weight of spar per ft. run, 4 • 25 lbs. This particular spar is made up of laminated plates of Duralumin. One advantage among others is that the number of laminations can be reduced or increased as the strength requirements dictate. This spar is sufficiently stable to require no internal stiffeners, and has proved to be ooooo ooo o o o o o o o o O This photograph o shows the step of o the Short all-metal o hull flying.boat " Singapore." O O o o o o o oooooooo light parts, it can still be used in reasonably thick sections, which consequently can be of simpler and more reliable form than similar steel parts. This fact regarding rib construction is becoming more and more recognised by builders of metal aircraft, and even those who have specialised in steel construction generally, are being attracted to light alloy for rib construction, because of the special advantage it posse; ses for this work. When we come to the construction of main spars steel becomes more applicable, and the higher tensile steels have, perhaps, a slight advantage over Duralumin where lightness is the main consideration. Nevertherless, the use of a light alloy presents some advantages even in this case, and these may be stated as follows :— The metal is easier to work and to form into shape. Where riveting is employed, the metal is more readily drilled or punched, and the rivet heads easier to form, leading to greatly-reduced labour charges. The sections of the spars also can be of simpler form, because the thicker sections of material which can be used are more stable in themselves, and this simplicity of form again leads to simplicity in strut fixings, etc. One of the accompanying photographs shows a type of Duralumin main spar under test at Rochester, and the follow- highly resistant to torsional loads. One advantage of using Duralumin is the ease with which it can be worked when in the annealed state—or if the work is of a simple nature— after normalising. The age-hardening of Duralumin after normalising is a very valuable feature, which is non existent, so far as the writer is aware in any of the high-tensile steels. This property can be used to save the power required to form any simple shape, and the material will age-harden in the usual time afterwards, whereas with steel it needs annealing to enable the shape to be obtained, and must afterwards be heat-treated if its full strength is to be developed. Metal Wing Coverings When we come to consider the possibility of covering the surfaces of planes with metal, it is obvious that some form of light alloy is the only solution. Even with such a metal the sheeting has to be so thin as to offer difficulties in manufacture and application. Indeed, such disadvantages have up to the present more than offset the possible advan- tages to be gained. The successful application of metal covering is linked up with the possibility of making the covering the main strength member of the plane. Some progress has been made in this direction, in an experimental 48/
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
