Just because you get old, doesn't mean you stop playing

Around Christmas time, I looked on Matt S's blog and saw a cheap alternative to a "toy" I've been wanting to try.

HERE

And a short video of it in action

HERE

After melting a couple of grocery store bags over tea lights in the kitchen, I e-mailed Matt for some specs on the hot air trash bags. Here is a synopsis of the ingredients:

"The bag I first used years ago was a plain old clear, very thin dry cleaner bag, but you have to figure out how to heat seal (so as not to add any extra weight) the top perforations and hanger hole. Now I use a super-thin garbage liner I found through my work. The cross/frame is two pieces of thin balsa wood (I'll get you the exact dimensions - I know it is 1/4" wide, but I forget the thickness) epoxied together in the middle. Next I measure and pencil-mark lines for candle locations. I have found that 4 on each side and 1 in the middle is the best heat to weight ratio (total of 17 candles). Don't put the outermost candles too far out, as the bag will move around and get melted. The birthday candles that work best are the thin, plain ones with no frills or ribbing around them. I attach them by lighting one candle tondrips 2 or 3 drops of wax and then stick another candle on the drops. Then heat up the sides around the base to melt it just a little better. Then I hang the bag with the open end down to carefully attach it to the balsa. find the exact opposite sides and attach those two with a 2" piece of clear tape. Then attach the other two. If your sticks are the right length, the bag will be taught & straight with no extra slack between the 4 attach points. Next, wait for a calm (2-3 mph breeze max.) cold night, and find an open yard or field with no overhead trees or powerlines. have one person hold the top of the bag while you carefully but quickly light each candle with a candle lighter (or Bic). In a minute or less it will be tugging skyward, so let 'er fly!"

The bags you're looking for are mostly used for commercial applications, office buildings, schools, restaurants. The closest I was able to find at the grocery store were 33 gallon bags .55mil thick. I had .4 mil thick tall kitchen bags, but they were a bit too small and the tops would melt after a couple minutes with candles lit underneath. Just look for the cheapest bags and the cheapest birthday candles.

I got a 1/8 inch thick sheet of balsa 3 inches wide and just cut 1/4 inch strips with an exacto knife. Cheaper - I saved like two bucks :)

I was so excited when I got the first decent one together, that I literally threw caution to the wind and we lit the candles in the rotor of the house. The bag got caught in the rotor of the roof, and oscillated over our house threatening to land. It eventually oscillated into the neighbor's yard sending embers of balsa raining down over grass thankfully. I guess I'll heed the warning to only fly in CALM conditions.

Later in the evening, we went over to a friend's house who was having a get together. Constructed another one, and went to the park next door to fly. As we lit the candles, the calm wind puffed up, thwarting our attempt. Just as quickly as it started, it quit, and we re-lit the candles. In a minute, the bag took off, and oscillated briefly before rising up and up and up. It floated for over five minutes before burning out and was just a yellow speck in the sky. Who knows how high it went.

My buddy was enthralled with the entertainment and was trying to figure out how to rig the candles with fireworks that would explode when the candles got low for a proper finale'.

Thanks for the idea Matt. There's a lot of science application for kids, and a lot of fun for adults with only small risk of burning something down. (depending on your location)