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Design and Manufacture of Parachutes

Note: The following procedure applies for both the main and drogue parachutes; the only thing that differs is the scale. All of the following pictures are from the main parachute construction.

Materials

  • Ripstop Nylon
    • Fire resistant
    • uncoated
  • Parachute webbing
    • 550 lb breaking strength
  • Paracord
    • 7 strand
    • 1/8” diameter
  • Kevlar shock cord
    • Tubular
    • ½“ diameter

Making The Stencil

A wooden stencil was made according to the following diagram.

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The distance across the canopy was calculated using the website in the comments section. The stencil was created using a laser cutter in order to be exact, however, the stencil was too large to fit into the laser cutter, so seven different pieces were made, each with indentations or protrusions on two of the sides so they all fit together like a puzzle (picture below).

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The outside shape of the stencil pictured above corresponds to the left shape in first diagram, and the inside shape corresponds to the right shape in the first diagram.

Creating The Parachute

Using the stencil, an outline was traced onto the fabric with a marker. Next, an inch was added to each edge that was going to be sewn to create a tab. In, the picture below, the tab was added to the edges with the black marks.

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Once the outline was complete, it was cut out, and the process was repeated four times for each size. After that, the entire thing was sewn together according to the following diagram.

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First, a small section and a large section were sewn together so that the parachute was in four quarters, and then it was sewn again to get two halves before sewing all together. We found that the easiest and most accurate way of combining each of the sections was to first pin the tabs together by aligning them, then folding the tabs in half, then pinning them flat (pictured below).

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First hold the tabs together then fold them towards the base.

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Then fold the tab over so it’s flat against the fabric. Now it’s ready to be sewn. A straight stretch stitching pattern was used to sew the panels together. The tabs that were folded over should be on the inside of the parachute once it is done. Once all of the panels are together, the seams have to be reinforced. This was done by placing the 1” parachute webbing over the seams, pinning it by putting a pin straight through both the parachute and webbing (to hold it in place while sewing), then sew all of it together, this time sewing it twice on each of the edges of the webbing and using a cross stitch.

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To add the paracord, we used two different methods. For the drogue chute, we sewed about five inches of paracord directly onto the chute right on top of the webbing. We used two cords to connect each end to the adjacent corners of the chute, and then we ran the cords through a swivel before attaching each end to the opposite side it started on. Finally, a knot was tied in the paracord to keep the swivel in place.

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For the main parachute, we created a loop with extra webbing and sewed that directly onto the existing webbing before running the paracord through the loop and tying it off. This was done to increase the strength of the attachment. Rather than relying on one line of stitching on the thin paracord, we could instead have two lines of stitching and a wider attachment. Other than that, the procedure was the same as the drogue.

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Integration

An important part of the integration is packing the parachute. If not done correctly, the chute could not deploy properly or get tangled in the paracord. To properly fold the parachute, first fold the parachute half. Next, continue folding the parachute in half until it’s fairly narrow. Then lay the paracord on the parachute, and then roll the parachute up with the paracord inside of it. The diameter of the parachute when folded should be slightly smaller than the diameter of the rocket. The swivel on the end of the main chute should be attached by shock cord to avionics bay and the payload (which is connected to the nose cone), and the drogue chute should be attached by shock cord to the booster and avionics bay. In the diagram below the green box is where the main chute goes and the yellow box is where the drogue chute goes. All shock cords should be daisy chained for easy packing. Once everything is connected and folded, the ends of the folded parachute closest to the avionics bay should be covered by the parachute protector then packed into the rocket.

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Deployment

The chutes were deployed using a black powder charge. It is important to note that the parachute protectors must be completely covering the end of the parachute closest to the black powder inside the rocket tube; otherwise the black powder charge will burn holes in the parachute upon deployment.

Testing

The drogue was preliminarily tested by attaching it to a weight, then dropping it down the stairwell in Akerman. Next it was tested by using it as the main parachute for the half-scale. The main chute was initially tested by attaching a weight to it and dropping it off of the top of the Washington Avenue parking garage. The other phase of testing was the ejection tests. To conduct these, the rocket is assembled with a black powder charge inside. Then the rocket is taken outside, propped up on something, and the black powder charge is ignited. This is done to ensure that the amount of black powder is enough to blow the parachute out of the tube during flight.

Challenges

For the most part, things went very smoothly in the construction of the chutes, which was the biggest part of our job. One minor hitch was the inability to laser cut just one piece of wood for the stencil due to the size restriction of the laser cutter; this was solved by making a puzzle out of the stencil and just laser cutting each piece individually.

Comments

Information for parachute design and construction, along with a calculator for parachute size was found here.