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Aviation History
1921
1921 - 0215.PDF
MARCH 24, 1921 of for their more specialised duties, although the initial cost is more, is the better boat, as it will be lighter, and as carrying capabilities are so important, the extra first cost is justified. In the usual type of hull the transverse" frames form continuous ribs round the body, giving to the yielding skin the necessary lateral stiffness, and resist all stresses tending to alter the form of the trans- verse sections ; however, this would give imperfect rigidity, as each one would be independent of the adjoining one, therefore, to give a combined and good resistance, they are united by the keelsons and side stringers. The boat's framework is thus com- posed of the trans verses and longitudinals. The former, disposed in direct contact with the skin, constitute the main skeleton of the hull, the skin and other members being fitted to it as a groundwork. The keelsons and side stringers are fitted in con- tinuous lengths within the transverse which form a supplementary skeleton ; these are connected, not merely to the inner surface of the transverse frames, but extend intercostally between them so as to connect to the skin. The lower part of the transverse frames are made specially strong by having the floors con- nected to same, as the bottom is liable to severe pressures, both widespread and local, through the hull being docked in trolleys or resting on the keel. For a similar reason the keelsons are made stronger than the side stringers ; they also prevent the hull from hogging and sagging. The centre keelson being strongest of all, it might be regarded as the backbone of the hull. It will be well to notice the difference and relative value of the two qualities, strength and stiffness, or rigidity. If we now consider the efficiency of the frames versus the stringers in stiffening the skin and supporting the sides against de- forming forces, the transverse frames are short compared with the stringers, as they only go from the keel to the deck, whereas the stringers run the whole length of the boat. It will be seen that the stringers, on account of their great length and consequent elasticity, cannot by themselves give useful resistance to widespread straining forces. Their principal duty is to give local support through their binding effect on the transverse frames, and, when fitted intercostally, to stiffen the skin. I think we might now consider the longitudinal versus transverse system of framing, or it might be stated which of. the two kinds of stresses, longitudinal or transverse, should govern the boat's structural design. In the longi- tudinal system the main fore and afters run all the way of the boat, the web frames being cut out to allow them to pass. The web frames extend round the body of the boat, usually at fairly wide intervals, and are of such depth and massiveriess that they form strong and almost inflexible supports to the sides, deck and bottom against all transverse Photo. No. 4.—N4 Atalanta. View from amidships, looking forward. strength to maintain unyieldingly its transverse shape. The longitudinals may be regarded as forming stiffening material for the skin and deck, giving these flexible surfaces the necessary rigidity to withstand all bending pressures acting between the supporting transverses (see Photo. No. 2). In comparing the longitudinal with the transverse arrange- ment of the light subsidiary frames, it will be seen that the heavy side stringers have been dispensed with; it also possesses the advantage of stiffening the skin against the buckling tendencies brought about by the fore and aft compression stresses which accompany hogging and sagging of the hull. Transverse frames and beams cannot prevent transverse buckling tendencies of the skin between them ; to counteract this, they must be placed closely together or the skin increased in thickness. As the compressive stresses above mentioned are most acute at the top of the hull, it is evident that a longitudinal arrangement of beams is even more important than a longitudinal arrangement of side frames. The longitudinal system is not only advantageous in in- creasing the longitudinal strength of the hull, but it also means a considerable reduction in weight which, while permitting additional carrying weight, also reduces the first cost. One of the disadvantages of this system is that the numerous deep projections cause the interior space of hull to be broken. A good example of the foregoing mentioned longitudinal systemis the N.4Atalanta designed by Mr. Charles E.Nicholson.' His method omits the closely spaced transverse frames and beams ; the transverse strength is obtained by fitting directly or. the skin a series of strong web frames at widely-spaced intervals. The longitudinals take the place of ribands, and forces. The supporting framework of the deck is arranged only require to be secured to the transverses carefully and very like that of the sides, light longitudinals being carried con- little fairing is required [see Photo. No. 3). Photo. No. 4 tinuously through the deep cross girders. It may be said shows diagonal planking OJ the N.4 Atalanta built on the longi- that in the foregoing system the deep web frames form the tudinal system, main skeleton of the hull, giving it all the necessary transverse (To be Continued.) No. 9 Squadron R.N.A.S. Dinner THE First Annual Re-union Dinner for members of the late No. 9 Squadron R.N.A.S. and 209 Squadron R.A.F., was held at the Dean Hotel, 87, Oxford Street, on March 5, Flt.-Lieut. T. F. N. Gerrard, D.S.C. (who was one of the Squadron-Commanders during the War), presiding. Ten former officers and thirty-seven old comrades were present. The company sat down to an excellent menu, which was appreciated in the good old English style, after which the Chairman, in proposing the toast, " To the Squadron," brought back to the memory of those present incidents, grave and gay, which occurred whilst serving their king and country overseas. The Secretary reported briefly on the work of the Committee, which was formed to inaugurate the function, and expressed the desire that there should be an annual Re-union, which was reciprocated by all present. An excellent musical programme was rendered under the direction of Mr. H. Ball, after which a very enjoyable and merry evening was brought to a close by the singing of the National Anthem and Auld Lang Syne." Copies of the photos, taken during the evening may be obtained upon application to the Hon. Secretary, Mr. A. H. Middlemiss, 74, Devonshire Road, Hackney, E. 9, who will be glad to hear from any who served with this Squadron, or who are still in the Service, who for various reasons were unable to be present at the first re-union. It is desired to get into touch with all old comrades, so that any item of interest may be forwarded to them, and also due notice of future re-unions. It is proposed to hold the next re-union dinner on the last Saturday in March, 1922. Cattewater Re-union Dinner , ™, „ , ^ ^ THE Cattewater (R.A.F. Seaplane Base) Old Boys Club are holding their second Re-union Dinner on April 2 (Saturday), at 6 30 p m. at the Midland Grand Hotel, St. Pancras. Tickets can be obtained of the Hon. Secretary, Mr. H. F. Bosher, 158, High Road, East Finchley, London, N. 2. 46th Squadron Annual Dinner THIS squadron is holding its annual dinner at Simpsons, in the Strand, on Saturday, April 2, at 6.45 p.m. Tickets /i each, and members are invited to bring one guest, provided he is paid for by the member so bringing him. All desirous of participating should communicate with Captain C. J. Marchant, 51, St. Kilda's Road, Stoke Newington, N. 16. Swift Reprisals . IN Mesopotamia two bands from Turkish territory recently made a raid in the Mosul area, and one of them collected booty to the amount of 70 camels and 1,300 sheep. Our aeroplanes were swift in retaliating by bombing the raiders' camps on March 3 with good effect. Two of our machines were hit by fire from the ground. 215
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