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145 OF ENGINEERING FORMULA.
Slates. :
Table of Sizes and Weights of Slates, exclusive of Laths.
Names. Sizes. Squares covered by 1000. Weight’ of 1000. Weight per Square,
Doubles .. Ladies .. Countesses Duchesses 13x 6 16x 8 20x10 24x12 ; 4a 72 10 cwts. 15 25 40 60 cwt»-, a
Wooden Rooks. (Principals 10 feet apart.)
t; - Span in feet. Prin- cipal. Tie- beam. King- poste. Queen- posts. Small Queens. Straining Beam. Struts.
20 4X4 9X4 4X4 — ' ’— 3 X3
25 5X4 1ÜX5 5X5 —A— — 5 X3
30 6X4 11X6 6XB •— ■ — 6 X3
*35 5X4 HX4 . 4X1 — ?X4 4 X2
45 6X5 13X6 -— 6X6 — 7XÖ 5 X3
50 8X6 13X8 — 8X8 8X4 9X6 5 X3
55 8X7 14X9 9X8 9X4 10X6 5|X3
60 8X8 15X10 10X8 10X4 11X6 6 X3
* The roofs above 30 feet span are calculated as k^ueen Trusses
Scantlings of Purlins and Rafters.
Bearing in feet. Scantlings of Bearing in feet. Scantlings of
Purlins. ' Batters. Purlins. Rafters.
1 6 6X4 1 4X2 10 8X6 6 X 2+
8 T X 5 4 X 2f 12 9 X 1 6 X 2i