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Making Ripstop Nylon Parachutes
by William J. Orvis, LUNAR# 309
After spending hours and hours building and painting your latest rocket, using an inexpensive, plastic parachute is like using paper towels in a fancy French restaurant. But then those nice nylon parachutes cost six or seven dollars, which is often more than you paid for the whole rocket including the paint and glue. In this article, I will show you how to make your own ripstop nylon parachutes for a lot less than seven dollars. Now it does take some time, but making a quality parachute is a creative way to occupy your time while the glue is drying on your model.
The first thing you need is access to a sewing machine (or someone you can sweet-talk into sewing it for you). You can sew a new parachute by hand, but a machine does a much better and faster job. It does not need to be a fancy machine, just a simple straight stitch is all the capability that is necessary.
The other materials consist of:
I bought the light-weight ripstop nylon at Dom's Surplus here in Livermore for a couple of dollars a yard. You can make one big (24") or a lot of small parachutes with a yard of ripstop nylon.
For shock cords, go to the sewing section of PayLess or any other drug or department store and get 1/16" round and 1/4" flat elastic. Use the 1/16" stuff on your smaller rockets and the 1/4" elastic on the larger ones. Larger sizes are available for really big rockets. I bought Singer "Knitted Polyester-Spandex" elastic, which costs only a dollar or so per package containing 72" of elastic.
The cotton-polyester string is sold right next to the sewing supplies for a dollar or so per ball and the paraffin you should be able to find in your kitchen or garage. Any hard wax will do if you don't have paraffin (for example, ski wax) and you need only a small amount to wax the string.
Cutting and Sewing
When you have assembled all the parts, the next step is to mark and cut the nylon. First make a hexagonal pattern the size of the parachute you want to make. A 24" parachute would be 24 inches from flat to flat. Place the pattern on the nylon and mark all around the edge. Using a ruler, measure another inch out from the edges of the hexagon and draw another larger hexagon as shown in the figure. Cut out the nylon along this outer hexagon and cut in from the outer hexagon to the inner one at each of the corners.
Start with one edge and fold in the small spike of nylon at each corner and fold in the edge of the outer hexagon until it touches the edge of the inner hexagon. Fold this piece over again and pin. Folding the corners in and the edge over twice hides all the cut edges. Sew down this folded over edge to hold it in place. Do the same for the other five edges.
Next, you need to make loops to attach the shroud lines. From the left over scraps, cut a strip of nylon about an inch wide and as long as the scrap piece. You need a total of about 18 inches of this scrap in 3 inch lengths for a 24 inch parachute. Less is needed for smaller parachutes. Leave it as one or more long pieces until after you sew it as it is easier to sew as one long piece than a bunch of short ones. Fold the one inch wide strip in half the long way, then fold it in half again, making a 1/4 inch wide strip. Pin it and sew down the center to hold it in place. Cut a 2 to 3 inch length of this strip and fold it in half the short way. Place the folded strip on one of the corners of the parachute with about half of its length (the loop end) hanging off the edge. Sew this strip down to the parachute with several passes of the sewing machine. Be sure to not sew the loop closed. Do the same for the other corners. For smaller parachutes, use shorter pieces to make the loops.
The next step is to make the shroud lines. The shroud lines should be as long as the parachute is wide. That is, a shroud line for a 24 inch parachute should be 24 inches long, measured from there it attaches to the parachute down to where it is gathered together with the other shroud lines.
First cut a length of string that is long enough to make all of the shroud lines. For a 24 inch parachute, this is (6 x 24 =) 144 inches of string. Pull the string across the block of paraffin, pushing it down into the block with your thumb. Do this three or four times to get the string well coated with paraffin. The paraffin stiffens the string a little and helps it stay tightly twisted and less likely to tangle.
Cut the string into three equal lengths, with each length equal to twice the length of a single shroud line. For a 24 inch parachute this would be a 48 inch length. Tie one end of the string to one loop on the parachute. Use a good, non slip knot like a square knot or a bowline. Pull on it to make sure it will not slip. Tie the other end to an adjacent loop on the parachute and test it. Tie the other two strings to the two other pairs of adjacent loops.
Put your finger through the three loops and pull down the center of the parachute. Adjust the strings until all the loops come together and the center of each string is looped over your finger. Pull all the strings together about 3 inches below your finger and tie them together with a single, overhand knot.
Attach It To The Rocket
This finishes the parachute. To use it, slip the looped ends of the shroud line through the loop on a nose cone and pull the parachute through the open loop in the string. Attach the shock cord and you are done. You now have a really nice parachute for less than a commercial one and with enough material left over to make several more.
Copyright © 1998 by LUNAR, All rights reserved.
Information date: March 31, 1998 wjo
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