6 BULLETIN 155, U. S. DEPARTMENT OF AGRICULTURE. 
_ STAVES. 
In designing staves economy dictates that the width and thickness 
be made such that stock lumber of standard sizes may be used. 
These are 2 by 4 inches, 2 by 6 inches, 3 by 6 inches, 4 by 6 inches, 
and 4 by 8 inches. Without strict adherence to the finer theoretical 
considerations as to thickness, etc., staves for most pipes for ordinary 
heads, and from 22 inches to 44 inches diameter are milled from 
2 by 6 inch stock, finished 13 inches in net thickness. From this up 
to 60 inches staves 2 inches thick are commonly used, and in some 
instances for pipes 72 inches in diameter. For pipes from 5 to 8 feet 
in diameter staves are usually 24 inches thick. For pipes to with- 
stand extremely high pressure and for those of extremely large 
size the thickness of the staves should be increased accordingly, -in 
order to insure safety against crushing or shear of the wood due to 
the greater tightness of cinching required. The width will be such 
as to cut with least waste from the stock sizes of lumber. 
Western yellow pine (Pinus ponderosa), Texas pine (Pinus palus- 
tris), spruce, California redwood (Sequoia sempervirens) and yellow 
fir (Pseudotsuga douglasii) have all been used for staves, but during 
recent years practically all pipes of this kind have been made either 
of redwood or fir, the other kinds of wood having proved to be less 
valuable for the purpose. At the present time fir is used much more 
extensively than redwood. It is less durable than redwood when placed 
in the ground under unfavorable conditions, but in other respects 
is considered to be just as good or better and costs materially less than 
redwood. The lumber for pipe should be of extra good quality. 
The following specifications for fir staves are typical requirements: 
Staves shall be made of live timber, sound, straight grained, entirely free from 
all dead wood, rotten knots, dry rot, cracks, shakes, or any other imperfections 
or defects that might impair their strength or durability. Pitch pockets will be 
allowed, provided they do not extend more than one-fourth of an inch into the 
staves. Small, tight knots not over three-fourths of an inch in diameter, and 
not occurring oftener than one in 4 feet of stave will be allowed, as will sap- 
wood on the inside of the stave so long as it does not extend more than half 
way through the stave at any point. 
Staves may be from 10 to 30 feet in length, but not more than 10 per cent 
shall be less than 14 feet in length. Timber must be thoroughly seasoned, either 
by kiln or air drying, before being milled into staves. ; 
Another requirement, not common, however, is that staves shall be milled 
from flat or bastard sawed lumber, those in which the edge grain passes through 
the stave in a distance less than one-half inch more than the thickness of the 
stave will be rejected. 
Other general specifications are— 
That the staves shall be dressed on both sides to true circles, and on the 
edges to conform to the radial lines of the pipe; that all staves shall be of 
uniform thickness, and each stave of uniform width throughout its entire 
