My costumes are usually based on hollow spheres made of cardboard panels taped together. The "lune" shaped cardboard panels are stuck together
with sticky tape. The following section gives instruction on how to build such a ball in easy steps.
Calculating the panel
or lune dimensions:
I use this formula to calculate the shape of each lune:
R = ∏ D (1/n + n/16)
This formula calculates the radius R of
circle for each side of each lune. The sides are rather gently curved - so the value of R is usually quite large.
D is diameter
of ball required for the costume - it is usually between 32 and 36 inches - note that you usually needit to go through a doorrway and that imits the size.
n is the number of panels or lunes to be used in the ball constructiion. (n is usually 12 or 16) Latterly I have prefered 16 panel (lune) spheres - 16 panel balls require more work but the results are visually better.
The length of each panel (or lune) before neck and hip allowance "l" is ∏ D/2
And ∏ D/n Is the maximum width of each panel (or lune).
example of a calculation: For a 36" 16 panel (lune) sphere.
R= 36 * ∏*(1/16+16/16) as ∏ = approx 3.1412
R = 120"
Thus to draw out the lune on a sheet of cardboard we now need to construct a compass with 120" radius - in the photo below I show how I do this using a length of 1x2 with a pencil inserted
through one end with a screw point at the other.
The next step is to calculate the length of the panel. To do this, draw a line
on a large sheet of cardboard of length l = ∏ D/2 = 56"
Draw arcs on both side of the line which intersect with both ends so that the overall shape of the panel is a lune as seen in the sketch below. Next , create a set back of half the width of a neck allowance (ca. 4") at one
end and at the other for a body ca. 10" for a 20" entry hole - so that the panel should look like that in the picture shown below: