Each triangle of longposts is connected top & bottom as shown in Fig. 2. Inscribed in each triangle A,B,C. is a small one abc the lower ab'c; being attached by staples to the low posts, see Fig. 3. There are diagonal wires on each of the three vertical sides of the triangular prism abc, a'b'c' See Fig.4. B Fig.2 B Fig. 3 Fig. 4 Figs. 23 should be constructed in the following manner; starting at a' the wire is taken to b; thence to a, from a to be from b back to a, so that the figure aba is enclosed by one continuous wire; a'cac'c'bc's' are done in the same way_ Fig ALTERNATIVE METHOD Bundle of 3 wires to be attached as shown in Fig 3. a b с DUG-OUTS. The attached 19 plates illustrate various recent types of dugouts, both British and German. "Notes on Cover against Shell Fire," issued by the General Staff, deduces from observations of direct hits certain principles to be followed in the design of dug-outs, and these principles are largely included in the actual designs attached, e. g. Supports of Roof Plates 4, 5, 8, 15, 17, 18 show strong supports, well braced. Bursting Course See Plates 2, 6, 10, 14, 15, and 19. Arresting Course See Plates 2, 6, 15, and 19. Entrances to Dug-outs The principle that the top of entrance should be at least 5 feet below the surface, with a bursting course over it, is illustrated in Plates 9, 10, and 12. Strutting the trench into which the entrance opens is illustrated in Plate 1, although the top of this entrance is hardly deep enough. Since "Notes on Cover against Shell Fire" was issued further data has been collected, and it appears that provided the roof is well supported, 9 to 12 feet of chalk, or possibly sandy soil, affords adequate protection against 5.9 in. or even 8 in. shell, but that 18 ft. of loam is desirable. This thickness of loam can, of course, be reduced if a bursting course is provided at ground level. Corrugated Steel Shelter. This is considerably strengthened by pit prop up-rights, about 4 ft. 6 in. apart down the center, bearing on cross pieces framed to the beveled bearers. One such shelter with only 4 ft. of loose earth over it stood a direct hit from a 5.9 in. shell. The German manual "Stellungsbau," published June, 1916, states that the following overhead cover proved shell-proof, but it is not stated against what type of shell. It will be observed that there are two arresting courses. There is no mention of air space in the manual. 1. Thin layer of earth. Layer of stones (bursting course). 2.7 ft. of earth (cushion). Double layer of fascines, laid cross-ways, four fascines thick (arresting course). 3.8 feet of earth (cushion). Double layer of logs (second arresting course). 1.6 ft. of earth (cushion). Layer of balks (inner roof). Total thickness=1434 ft. (4.5 m.). 2. Thin layer of earth. Layer of stones (bursting course). 4 ft. of earth (cushion). Layer of rails (arresting course). Layer of stones (2 ft.) (arresting course). Layer of fascines (cushions). Layer of broken stones (3.2 ft.) (second arresting course). Layer of logs (inner roof). Total thickness-13 ft. (4 m.). H. G. GANDY, Brigade Major, S. M. E. School of Military Engineering, Chatham. November, 1916. |