The ornamental design for spiral windcatcher, as shown.
FIG. 1 is a front elevational view of a spiral windcatcher showing my new
design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a sectional view taken in the direction of arrows along line 3--3
of FIG. 1; and,
FIG. 4 is a sectional view taken in the direction of the arrows along line
4--4 of FIG. 1.
While FIG. 2 is randomly showing a grid type surface on some of the
individual elements of the claimed design, it is understood that this
surface continues over the entire structure.