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Aviation History
1920
1920 - 0580.PDF
MAY 'if, 1020 Naturally, the^pressure at which the gas valves blow off ishigher at the ends of ship than midships. Forward combined control and engine car, Zeppelin There is every possibility that it will be practical to use even lighter fabric, of, say, 50 gms./m2 for Service rigids where the laCf' ounce of efficiency is of the utmost importance. Owing to the risk of damaging this fabric and the extra cost of obtaining such very finely woven cotton, it is probable that, for commercial ships, heavier fabric will be used. A curious feature in gasbags is that they maintain their gas-containing properties for a reasonable time, and then suddenly become porous. In nearly every case the gasbag has to be removed within a fortnight of the beginning of this sudden collapse in its gastight qualities. Generally speaking, the gasbags last about two years. The automatic valves have now reached about the limit in size, having regard to their very light construction. In rigids larger than 2,000,000 cubic ft. capacity it is probably best to fit two automatic valves instead of one, situated at the bottom of the butt end of each gasbag. Too great stress cannot be laid on the extreme importance of gasbags blowing off at a more or less uniform pressure. Gasbag No. XVIIIXVII XVI XV XIV :XIII XII . XI X IX VIII VII VI V IV III II I Automatic No. ofValves. 1 1 1 1 „, t. =• •:t ' • I x • • ; ••• t 1 - • t ; - _ I t t I 1 1 Gas Valve Settings Diameter of Valve Discsin m/m. Small valve 545.. 545 * Lai » 9 •ge , tt ' ft 11 It Small , 545 - 545 . 545 , 800 , 800 , 800 , 800 , 800 , 800 , 800 , 800 , 800 , 800 , 800 . 545 . 545 Valve setting in m/m. ofwater pressure. 16 16 13 13 10 10 9 9 9 9 99 9 9 9-5 9-5 13 13 Cars. General Car Arrangement.—In rigid airships it is obviously undesirable to concentrate too much weight at any one point. For this reason it is necessary to split up the total amount of power required into several distinct propelling units, bearing always in mind, however, modifying factors such as the horse-power of available prime movers, propeller effi- ciency, maximum weight and thrust which can be concentrated conveniently at any one point, and the number of units required to give the requisite reliability. Several systems of car arrangement have been in vogue from time to time. The Zeppelin Company's arrangement is to fit one large composite centre line car forward, containing in its front end the control and observation car. A car containing a power unit is fitted immediately behind the control car, the two cars being separated by a space of about 1 in. to prevent much of the noise and vibration passing from the power car into the control car. The wireless cabin is situated in the after part of the control car. A second centre line car is fitted well aft, containing a power unit. Between these two cars are fitted one or more pairs of small wing cars arranged at varying dis- tances from the centre line of the ship, to prevent slip-stream interference. The forward and after cars are also fitted with buffer bags and handrails, and are used as the two points of contact for handling purposes on the landing ground. The accompanying diagram of the car disposition of the German L 70 class illustrates this type of general arrangement (p. 579). Thr British system, except where German practice has been copied, provides for one small centre line control car fitted well forward. In some cases it can hardly be regarded as a car in the strict sense of the word, but rather as an excrescence built out from the internal keel of the ship where the bow begins to rise. This car only contains the control •i --
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