I am homeschooling my 6 and 8 year old boys this year and since we're reading The Twenty One Balloons, I got the idea to see if it would be possible to make a real, flyable hot air balloon. I was SO happy to find your site and your excellent step-by-step videos. The following are the pictures we took of our process (our son made the balloon with an older friend). They were very able to do most of the steps fairly independently, which was fun to see. We were able to get the right kind of custodial grade bag from our church, where they had rolls of them. GREAT PROJECT! --Jessica Smith
Measuring the diameter of the bag Cutting the foil square Making the straw frame hot gluing on the candles (we started with 4 and I did cut them down out of weight consideration) Straw frame done! Taping it all together The boys suggested 4 candles gave inflation, but no lift. The boys suggested more fire power! so we added 2 more candles and got lift off!
They wanted to try it outside and it didn't last long in the breeze.
Professor Adolfo Batisda
Professor Adolfo Bastida of the University of Murcia in Spain and who also runs a science program for young people sent these pictures. The project was complicated by trying to find the right kind of plastic bag. "You cannot imagine how many different bags we tested. Finally we found it: that right plastic is used by some hair dressers to cover the shoulders of their clients! Last Friday we did our balloons following your directions and it was amazing."
Joshua Allen Harris
This video link is to an artist named Joshua Allen Harris who makes surreal inflated creatures from thin plastic bags. I doubt it could be applied to a small hot air balloon (surface area, see Part 6), but the shear brilliance of the art is worth a look.
For years I'd heard that you could make a hot air balloon from a garbage bag. When I finally tried it, I found that - as with so much of life - the "devil's in the details." Here's what I learned, in the form of the embedded instructional videos below, with the help of some of my students.
REALLY USEFUL UPDATES
By far the biggest problem with this project is finding bags that are thin enough. Most garbage bags sold through retail are much too thick and heavy. However, some people have sent in some solutions.
From California Science Teacher Susan Rideout: "I have a tip - I used the garbage bags you recommended, and was not able to get it to launch until I cut the straws lengthwise in half (except at the join where they overlapped to connect). This removed just enough weight that with 5 candles I launched quite well. Just passing it along for future experimenters!"
I would add to Susan's suggestion that you can use 3mm or 1/8" square balsa sticks--or even thinner if you are really careful--instead of straws. Balsa might be harder to find, but it weighs significantly less than straws.
Steve Mazzanti, a Technology Instructor in Athens, Texas has used bags from the dry cleaners, which I mentioned in the videos. But the bags have a pesky hole at the top where the hanger goes through. I've been taping the the top, but Steve welds the plastic together with a clothes iron, first putting paper under and over so it doesn't stick. That sounds like an easier and better way. He even welds bags together end to end!
Richard Brown, a math/science teacher at Watertown High School in Connecticut, informed me of a widely distributed bag that worked for him. Look for Ruffies 8 gallon Color Scents (they smell like vanilla) at home improvement stores or Amazon (at least in North America--people from other continents please let us know where you've found thin bags). If you Google it you can see what retail outlets sell them near you. At 8.9 microns (or 0.35 mil) the bags are half again as thick as the thin bags I use, but Rich got them to fly (you might have to use a fifth candle).
Finally, I knew there must be a better way to attach the candles than the way described in the video. Somebody (I can't find the e-mail) suggested hot glue, which works well for me. And when I put them all together, in a line, it's much easier to light the candles. John Mason made the balloons in the UK with his Scouts and discovered that tiny pieces of double-sided tape work best for him to hold candles. And he will fold up the sides of the foil so that it does not drip wax.
Part 1 : Introduction
This video covers history of hot air balloons in Asia and France, modern day ballooning, and some basic terms.
Part 2 : How It Flies
This video presents some amazing facts that allow hot air balloons to fly, woven into cool videos of people-carrying balloons preparing for take off.
Part 3 : Fuel and Safety
This video shows why we think volitile fuels are a bad idea (we use candles) and I make the case that hot air balloons, education and kids (with adult supervision) all go together.
Part 4 : What You Need to Build a Hot Air Balloon
You need aluminum foil, plastic drinking straws, birthday candles. And the only tricky part is finding a trash can liner that's thin enough, but we'll show you where to look and how very thin plastic is measured.
Part 5 : Build and Fly
This video gives the construction details for keeping the botom of the balloon open and holding the candles and we make the case for flying indoors. You do not have to weigh anything, but we do on the video just to stay conscious of keeping it light.
Part 6 : Using Smaller Bags
Using smaller bags is more of a challenge than using larger ones. We'll show you why and present some tips for making them work. Plus a (green screen) ride in a hot air balloon for the student volunteer presenters.
I put a lot of work into making these instructional videos. It's encouraging to me to know that people are putting the information to work and I improve the instructions when people point out when something is not clear ( I answer specific technical questions as best I can, too). Furthermore, hundreds of people have sent me innovations that have made all the projects on ScienceToyMaker better. So, consider sending me feedback or leave a comment at the bottom of this page about how the hot air balloon project went for you.
