444 
LOGGING 
set as for a railroad survey and a line of levels established. The 
grade line having been determined from a profile map, it is 
established in the field.^ Center stakes for the bents are es- 
tablished at determined intervals, and following this the grade 
stakes are set for the batter-post mud-sills. The data for the 
base of each trestle bent are calculated for the use of the con- 
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Flume Curvature-Degrees 
60 
Fig. 164. — Graph Showing the Permissible Flume Curvature in Degrees 
for Logs of Given Lengths and Crook. 
structors, and show the length of the two lower sash braces, the 
distance along the batter posts, and the length each batter post 
must extend below the first sash brace in order that the trestle 
may stand plumb on the mud-sill. The determination of the 
length of each sash brace is important because it governs the 
batter of the posts and if it is not properly calculated the spacing 
between the posts under the cap will vary. 
Careful consideration must be given to curves and the maxi- 
mum degree of curvature required for the longest material that is 
to be handled must be determined. 
The relation of log lengths, both straight and crooked, and the 
permissible degrees of curvature are shown in Fig. 164. ^ 
1 The grade line of a flume is the cut-off height of the trestle bents, which 
is the base of the caps. 
2 From The Design of Log Flumes, by J. P. Martin, Engineering News, 
Nov. 14, 1912. 
