Make a simple model rocket parachute using a plastic shopping bag.
Step 1: Supplies
-Plastic shopping bag (Thick Plastic, Menard's work's best)
-Paper Reinforcing tabs
-Old model rocket parachute
-Kite string (or similar cord)
-Sharpie (reg. and pen)
-Craft hole punch
Step 2: Preparing Bag
Place bag down flat and cut off the bottom reinforcing part's with scissors. Then also cut off the handles of the bag. This will make the next step easier.
Step 3: Trace the Parachute
Lay your bag flat down again. Use your ruler to get all the creases and wrinkles out. Using the old parachute* and a ruler to trace the shape of the new parachute with a Sharpie pen. Remove the stencil and you now have an uncut parachute.
*Instead of using a old parachute as a template, you can create your own style.
Step 4: Cut the Parachute
Now take the ruler and line it up with the lines you made. Take the X-acto knife and using the ruler as a strait edge, cut on the lines. This will make nice, clean edges and make your work look professional. Get rid of the scrapes.
Step 5: Mark and Cut Out Holes
Using a Sharpie marker, place a dot 1cm from the corner of the parachute. Then line up the punch with that dot and punch it thru. It is unlikely that the punch will cut thru the plastic completely (unless you were to heat the tip up to melt the plastic). If so, just pinch the tab and pull it off. Repeat with other corners.
Step 6: Rienforce the Holes
Now take the reinforcing tabs and place them over the holes. Repeat for the rest of the holes.
Step 7: Make and Tie the "Shroud Lines"
Now take your Kite string and cut 3, 2 foot pieces. These will be your Shroud Lines. Then Tie the lines to the parachute, with the knot of your choice, to the corners. refer to the completed picture for placement. Trim the loss ends.
Step 8: Testing
Take a nose cone from a model rocket or weight with a small loop in it. Bring the lines together and and put them thou the loop on the nose cone*. Then use the "loop over" method to secure it to the nose cone. Step 19C at this link
should help. Then using a fan, hold the parachute over the air and let it inflate. If all is well, you can remove the parachute and put it on your rocket. Have fun, and be safe when flying model rockets. :)
*Shroud lines are red for better viability