The ornamental design for a chimneycapbase, as shown and described.
FIG. 1 is a front view of a chimney cap base in accordance with my design,
the undisclosed rear, left and right side are identical;
FIG. 2 is a bottom end view of the chimney cap base of FIG. 1; and,
FIG. 3 is a top end view of the chimney cap base of FIG. 1.
The exemplary embodiment illustrated is symmetrical about the elongated
axis thereof, such that the rear view, left side view and right side view
are substantially identical to the front view of FIG. 1.