cardboard for its gore pattern; tape
several sheets together before laying
out the pattern. Draw a line down
the middle of the poster board and
then perpendicular lines at every
five degree lengths (this is the length
measurement in the spreadsheet).
From the center line, mark the
half width of the gore at every
perpendicular in both directions since
the gore pattern is symmetrical.
Draw a smooth line connecting the
half-width marks and you have the
shape of the gore. Now cut it out.
Lay out the parachute fabric and
smooth out its wrinkles before drawing the pattern on it. If the wrinkles
are very bad, you may want to iron
the fabric first. Since it’s nylon, be
careful that the iron temperature isn’t
set too high or that the iron doesn’t
sit on the fabric too long. Line up the
gore pattern with the heavier “
rip-stop” threads woven into the fabric.
When the long axis of all of the
parachute’s gores do not line up the
same way with the rip-stop threads in
the fabric, the parachute’s shape can
warp during a descent. It’s easier to
see the pattern in the fabric if a
contrasting colored pencil is used to
draw the outline of the gore pattern.
Rather than cutting out the gores
with a pair of scissors, use a hot
cutter. Hot cutters are essentially
soldering guns with a
rounded tip. The tip
melts its way through
the nylon fabric which
prevents it from
fraying. You’ll find hot
cutters in some soldering
gun kits and at kite
stores. Lay the fabric on
a sheet of Masonite
before you begin cutting
it. The Masonite will
protect the table you cut
the fabric on.
After cutting out the
gores, fold the top and
bottom seams over by
one inch and iron the
seam in. Then interlock
the sides of two gores
together as illustrated in
The seam between the gores is
temporary because the seam needs
a strip of 1/2 inch wide bias or —
better still — twill tape for strength.
Cut four pieces of twill tape to a
length six inches greater than half the
circumference of the parachute. Then
mark each tape at its center and at
five and six inches from both ends.
Lay a twill tape on top of a gore
seam and align the tape down the
center of the seam. Shift the tape
until the tape’s six inch mark lines up
with the bottom of the parachute
canopy and hold it in
place with a few hand
stitches. Do the same with
the other end of the tape
■ FIGURE 9A. Your
gore pattern should
look like this.
■ FIGURE 9B.
on the opposite side of the canopy.
Repeat this process of aligning the
rest of the tapes on the parachute
canopy. When done, the twill tapes
lay on the top of the parachute and
cross each other close to their center
points and are centered over the
parachute’s vent hole.
Fold the ends of each twill tape
at their five inch marks so the ends of
■ FIGURE 11. Shroud lines tie to the
eight loops at the bottom of the
parachute. Each loop forms as the
reinforcing twill tapes wrap around
the bottom of the parachute.
■ FIGURE 10. A cross
section of the parachute
placement of seam
reinforcing twill tape.
THE PARACHUTE GORE IS
NOT RELATED TO AL GORE
Fabric is made by weaving together
two yarns (yarn is twisted threads). The
vertical (or lengthwise yarn) is called the
warp and the horizontal (or side to side
yarn) is called the weft. In the case of rip-stop nylon, the fabric consists of threads
of twisted nylon fibers or monofilaments.
The end product is a flat sheet of twisted
and woven nylon monofilaments.
Since ripstop is a flat two-dimensional
sheet that doesn’t stretch, it can’t bend
into a three dimensional shape like a
hemisphere without wrinkling. Nuts &
Volts readers learned this when they cut
out and folded their first paper cube in
elementary school. In the case of the
hemisphere, the shape is modeled by
changing its continuous curved surface
into a series of neighboring flat strips. The
narrower and more numerous the strips,
the more closely the modeled shape
becomes a perfect hemisphere. However,
the thinner the strips, the more time is
spent cutting and sewing them into a
parachute. Not only does it take more time
and work, but it makes the final parachute
heavier due to the additional seams and
sewing. Each of the parachute’s flat panels
is called a gore. The old World War II
parachutes you see in the movies are
made with a greater number of gores
since the parachutes are so much larger.
In the parachute design in this month’s
column, an eight gore design was selected
as the happy medium between the perfect
hemisphere and a paper cube.
You can learn more about weaving
yarn into fabric at Wikipedia. I found a
good webpage on sewing kites (which is
similar to sewing parachutes) online at
Kite Sewing 101, www.geocities.com/
September 2008 85