164 



CEMENT AND CONCRETE 



FINISHED fa/v/r WITH PARTS 



half the diameter of tank plus the thickness of wall 

 and thickness of boards used. If the wall is to be 5" 

 thick at the top and boards 1" thick are to be used, 

 then the sections would be 3' 6" long at the inner 

 length. Since the outside surface of the wall of the 

 tank is vertical, both sills for the outside form will be 

 cut the same. The inner surface should be given a 

 slope of 2" to the foot, or, for a tank 2' deep, the bot- 

 tom sill for the inner form will be 4" shorter than the 

 top one. The sills for this form are best cut from a 

 2" x 10" or 2" x 12" timber when a jig or band saw 

 is available, making it possible to get both the inner and 

 outer sills from the same piece, as shown in Fig. 154-a. 



After sills are cut, the 

 boards must be carefully 

 fitted to make a tight wall. 

 The boards for the inner 

 section are made 5" short- 

 er than those for the outer 

 section to allow for thick- 

 ness of floor. After these 

 sections are completed, 

 they are assembled in place 

 and can be fastened togeth- 

 er by strips across ends. 



3) For concrete construction such as this, never use a 

 mixture leaner than 1:2:4. For small tanks, a 1 : 2: 

 3 mixture is better. 



4) Follow method of mixing and placing as outlined in 

 Sees. 141 and 143, with the exception of the following: 



FIG. 155. Circular tank complete. 



