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New Project: $4 Hot Air Balloon

Up, up, and away, with Scotch tape and a painter’s drop cloth.

New Project: $4 Hot Air Balloon

On a June afternoon in 1978, while most normal kids were focused on sports or getting Dad’s car keys, I was busy readying another one of my quixotic contraptions, made out of junk-at-hand, for its maiden voyage. Assisted by a good friend who also enjoyed such nerdy pursuits, I stoked a fire inside an improvised burner and slowly, carefully inflated the large, fluttering balloon I had fashioned out of plastic drop cloths, Scotch tape, and coat hangers.

The sides of the plastic envelope became warm to the touch, and I could feel a slight upward tug on the hoop that framed the inlet at the base of the balloon. My friend and I took turns steadying the giant transparent chrysalis over the chimney and gleefully fueling the fire with old exams and papers from the just-completed school term. Another minute passed; the balloon felt very warm and I could feel its positive buoyancy. I wasn’t sure how hot the top might be getting and didn’t want to press my luck. I released the hoop.

The balloon lifted upward perhaps 10 feet clear of the chimney. It seemed to hesitate there, as though comprehending its new freedom, and then accelerated skyward with a swirling whoosh. To my total surprise, it kept climbing past treetop level, 100 feet, then 200 feet, and began to drift as it climbed. First it cleared the field, then the neighborhood, and then went out of sight over the hills.

Our elation was only slightly dampened by my father’s reprimand for our irresponsibility and my mother’s aggravation over the disappearance of yet more household supplies — aka “engineering materials.”

We went on to fly more balloons (tethered), one even carrying a half-pound camera aloft. Years later, I bought and flew a ready-made model hot air balloon with my son. While more colorful to look at, it didn’t fly nearly as well as our homemade versions had. For all you readers who enjoy that special kick that comes from seeing an unusual homemade rig actually work, here’s some fun that can be had on a kite-string budget.

Specifications

My original balloons were fashioned from two 9’×12′, 0.7mil plastic drop cloths, seamed together into a cylinder along their 12′ sides. The finished envelope enclosed a volume of roughly 230 cubic feet (6.5 cubic meters), weighed 15oz (425g), and would lift again as much in payload when thoroughly heated. Unladen, these balloons had lots of extra lift for rapid climb and a long flight before cooling enough to descend.

The single-drop-cloth balloon presented here encloses about 75ft³ (2.1m³), weighs about 8oz (227g), and will provide another 4oz (113g) of extra lift when heated to the plastic’s safe capacity. These smaller balloons provide shorter flights but are much easier to handle.


  • Goli Mohammadi

    Super neat, Mathew! Thanks for sharing.

  • Goli Mohammadi

    Very cool, Stephen — thanks for sharing!

  • http://Sk You:mama

    Coolio

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