Bob, 

What would the cube of a Cypress that was 18' CBH tapering to 12'
at 60'. The remaining 30' has small limbs so just give the trunk cube.
I need this to help me estimate the larger Cypress I'm seeing. I wll
post a couple of photos of the the subject tree on the file page.
Thanks, 

Larry

Larry, 

Volumes according to type volume model are as follows. 

Neiloid shape: 816 cubic ft 

Cone shape:   1089 cubic ft 

Paraboloid shape: 1633 cubic ft 

If the taper appears constant, then choose the cone shape. If the sides are concave, use the Neiloid shape. If the sides are convex, choose the paraboloid shape. Or, choose some combination. The average of Neiloid and Paraboloid is 1224 cubes. I'm guessing that the form of the trunk starts as Neiloid and then changes to probably midway between paraboloid and cone. Perhaps a 1224 is a good beginning figure. 

Bob