| A para-balloon is a small but very light-weight parachute with a very low sink-rate. The ones I experimented with had a canopy diameter on the order of 1 meter and a weight of about 5-10 grams. Such a parachute will descend in calm air at the rate of only a few centimeters per second, much like thistledown or a dandelion seed.
Launched in the right conditions, however, it can get caught in thermal updrafts and go UP!
HUNDREDS of meters in the air.
...Even completely out of sight.
I learned of these from a model airplane magazine (now long defunct) in the early 70's, and made dozens of them, at a cost of pennies apiece, while growing up in rural Texas. They are easy to make and fascinating to watch.
Making your own para-balloon
To make your own para-balloon you'll need the following materials:
-A lightweight polyetheline garment bag from a commercial dry-cleaner.
-A spool of cotton sewing thread.
-A roll of cellophane adhesive tape.
-A pair of scissors.
-Some sort of felt-tip marking pen.
-Some sort of plastic capsule (I've used plastic prescription pill bottles, or, alternately, the plastic capsules you get from gum-ball machines that contain the little toys, rings, or other party-favors).
Begin by spreading out your dry-cleaner bag so that it lies in its natural rectangular, flat form. Use a piece of your tape at each corner to hold it in place...you'll need to do this on a large table, but I've even done it vertically, taping the bag up against a wall.
You now want to draw a semi-circle with your felt-tip marker along one of the long sides of the garment bag, so that, when you cut through both layers of the bag along the semi-circular line, a circular parachute canopy will be the result.
You can make a compass by tying a length of your sewing thread to your marking pen. Hold the thread down with your thumb at some point along its length, and, with the pen in your other hand, stretch the thread out to full length, and use this to trace the semi-circle. There's no reason not to make this semi-circle the maximum width of your garment bag.
Most dry-cleaner garment bags will have an 'M' fold or pleat along each side, however. This allows them to expand like an accordion to accomodate the clothes that they will contain. So you don't hold the 'center point' of your thread and pen compass down exactly on the edge of the bag, but a distance beyond it equal to the width of the pleat in the bag.
Once you have a big, circular piece of lightweight plastic, fold it like a tortilla in half, then in quarters, then again in eighths. You now have a "pie slice" shape. Use your marking pen to mark regularly spaced points along the perimeter of your canopy at the folds. These will be the attachment points for the shroud lines. Then, cut 3 or 4 centimeters off of the "point" of this pie-slice shape of plastic...you want a hole of some 6 to 8 centimeters diameter at the very center of your canopy for stability.
The shroud lines are the next thing you make. You need eight of them from your sewing thread, of equal 1-meter length. The exact length is not nearly as important as that they be equal, however. 90 centimeters, 130 centimeters, no big deal, just make them all the same. Tape one end of each to the marked points around the perimiter of the canopy. Tie the free ends of all eight shroud lines together, taking care always that the shroud lines will remain all of the same length.
Finally, clamp the joined end of the shroud lines in your "payload capsule". I used to put my name, address, and phone number in the capsule, on the chance one of these might be found...it would be really interesting to know how far they might drift.
Launching the para-balloon.
Launching one of these is more difficult than actually making one. You can practice indoors, under a high ceiling, in order to have wind-less conditions. The procedure:
-Hold the payload capsule in your non-dominant hand...i.e., if you're right handed, hold the payload capsule in your left.
-Grasp the shroud lines all together in your dominant hand, maybe 20 centimeters from the point at which they are taped to the perimeter of the canopy.
-With your dominant arm extended full length, pivot it upwards. The canopy will partially inflate on the way up, which is fine. You want it to scoop up a mass of air.
-As your arm approaches the vertical, release the shroud lines. The mass of air scooped up by the canopy should continue upwards by inertia, carrying the canopy with it, and inflating it at its maximum upward point of travel.
-Move your other hand, holding the payload capsule, so that it will be suspended vertically under the canopy, with all shroud lines equally taut.
-Release the payload capsule, and step back.
...The para-balloon should deploy, inflate, and even travel upwards a few centimeters just on the inertia of the air mass swept up in your initial upwards sweep. It should then begin wafting downwards, just a bit faster than your average dust-mote.
As I said, it WILL require practice. It's easier described than done.
Don't attempt to launch one of these outdoors in winds exceeding 3 or 4 knots. You want a calm morning with sunshine, which generates the thermals. A successful launch will result in the para-balloon wafting along, bumping up and down with each micro-current. If a thermal comes along, the para-balloon will climb up, up, and away...
With practice you'll learn to detect the onset of a thermal by changes in wind velocity or direction, or even by minute changes in temperature.
I sent many of these flying away from the pasture at the farm on which we lived when I was in high school. Never had any response from anyone who might have found one. There wasn't much else to do...
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