FORM CLASSES AND UNIVERSAL VOLUME TABLES 



215 



volume utilized as board feet or in any other unit, can be computed 

 by first ascertaining this net volume. The form factor is 



Bh 



J- v' 



These form factors serve no useful purpose. 



178. Form Height. Form height is the product of form times 

 height. 



Since V=Bhf, tables of form height simply eliminate one of the 

 two multiplications necessary in deriving cubic volumes. 



0.710 



0.690 



0.670 



0.650 



0.630 



0.610 



| 0.590 



| 0.570 



§ 0.550 



_o 



™ 0.530 



« 0.490 

 fi 0.470 



0.450 



0.430 



0.410 



0.390 



0.370 



0.350 



20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 195 100105X10 115120 

 Heighten Feet 



Fig. 36. — Curves of breast-high form factors for form classes from .50 to .80 inclu- 

 sive, showing effect of height upon the form factor. From Tor Jonson. 



179. Form Classes and Universal Volume Tables as Applied to 

 Conditions in America. The standard form classes, when applied to 

 trees of different diameter and height, thus distinguish three variables 

 just as did the universal volume tables based on diameter, merchant- 

 able length and rate of taper. Universal volume tables if based on 

 total heights would show volumes for the given unit in three instead 

 of two dimensions; D.B.H., Height, Form Class. 



But to derive universal volume tables by form classes to be based 

 on merchantable length instead of total height would not be so simple, 

 for the following reasons: 



