Aeroplane construction and operation; including notes on aeroplane design and aerodynamic calculation, materials, etc. A comprehensive illustrated ... flight officers and students. Ad

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1918 Excerpt: ...were made on ribs by Mr. Heinrich of the Heinrich Aeroplane Company, the ribs being built up on short pieces of spar so that actual conditions were approached. Instead of using a distributed load, such as usually comes on the rib, a concentrated load was placed at the center. If the rib were uniform in section the equivalent uniformly distributed load could be taken as one-half the concentrated load, but because of the lightening holes this would not be very exact. It would be on the safe side, however, as such a test would be more severe than with a uniform load. The ribs were of the same type as shown in Fig. 5, and were placed 32.5 inches apart. The front spar was 2 7/16 inches deep, the rear spar 2 1/16 inches deep, and the overall depth of the rib at the center was 3 1/8 inches. The rib flanges were of white wood 3/4 inch wide, and 3/16 inch thick. In rib No. 1 the web was solid whitewood, 3/16 inch thick, and in ribs Nos. 2 and 3, the webs were mahogany three-ply veneer (5/32 inch thick). Test of Rib No. 1. There are 5 lightening holes between spars, with 2 inches of material left between the holes, and 1/2 inch between first hole and front spar opening. With 95 pounds concentrated load at the center, the first fupture appeared as a split between the first hole and spar opening. At 119 pounds, the flanges had pulled away from one side of the spar, and 1/8 inch away from the web. Full failure at 127.5 pounds. Web was split between each lightening hole with a complete cross break at center of web, the latter being caused by a brad hole in the web. Test of Rib No. 2. Laminated web, with no brads driven opposite lightening holes. At 140 pounds rib deflected 5/16 inch, and when relieved sprang back only 3/16 inch. With 175 pounds, the deflection again was ...