Solar Hot Air Balloon Message-in-a-Bottle

This is a hot air balloon made from trash bags and heated by the sun. Once airborne, it should stay up 'til the sun goes down or behind the clouds. Needless to say, it can travel a long, long way. Attached to it is a "message-in-a-bottle" asking anyone who might find it to email their location, just to see how far it flew. There's just something romantic about a message seeking out who-knows-whom in far away who-knows-where.

As a note, as boys, my brother and I lived on a tidal river in Florida. Walking the mangroves, we found a couple of messages-in-bottles that people sent. One came from another state. It said something like, "Send a postcard with your address and we'll send a present." My brother sent a note and sure enough they sent back a King James Bible (it was a "Fishing for Men" outreach project by a Georgia church). He still has that Bible. It was inspiring to think of how far that message had come and the path that it took. The magic of a message-in-a-bottle is to imagine, "Where will it go?" and, "Who will find this?"

Step 1: Materials and Tools

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Materials
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1. Trash bags -- They must be THIN, I used 0.6 mil but the thinner the better. Most quality bags are heavy, at least 1.0 mil. We want the cheap-O bags.
2. Tape -- I used regular masking tape. Likely scotch tape is okay too. Don't use the wide package tape though--too heavy.
3. Thread
4. Pen and paper
5. Plastic bottle -- I actually had to get rid of the bottle because it added too much weight.

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Tools
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1. Scissors
2. Blow drier

Step 2: Layout and Taping

This may look harder than it actually is. To go with the pictures, I tried to sketch some diagrams. Just realize that it's pretty simple.

STEP 1
Get 4 bags and cut them open by cutting the bottom and ONE side. It'll unfold then to a big rectangle. Lay out all 4 opened bags like in the picture/diagram. Tape them together to make a huge rectangle.

STEPS 2 and 3
Fold the huge rectangle over then tape the two sides closed. You now have only the bottom untaped and open.

STEPS 4 and 5
Hold the center of the open seam and lift it open so that the points marked A & B in the diagram come together. Tape and seal off the last open seam.

Step 3: Write Your Message and Inflate It

Get your message ready. Once it's inflated, it's go-time! I scratched the plastic bottle after it became clear that it was weighing down the balloon. I just rolled up the message, then tied it off with a piece of thread about a foot long. Essentially, the message asked for an email back to me simply saying where the balloon was found.

Just as a note, since this is a SOLAR balloon, so you'll want to do this on a bright sunny day.

Cut about 3 inches off of one corner. Just cut enough to shoot hot air in it from your blow drier. Simply start blowing hot air into the balloon. Be careful not to burn or melt the bags. The balloon will quickly take shape.

As soon as it's inflated, twist the opening so it closes, then tie your message onto it. Once inflated, I moved into the sunlight so the sun would start heating it up.

Step 4: Watch It Go!

Nothing much to say here, launch it and watch it go!

After floundering around a bit, it started to gain some altitude, bounced off some power lines and shrubbery, then finally got above the treeline. Then it was gone!

I intended to chase after it on my bicycle. I quickly saw that was pointless. Within 10 minutes, it was out of sight last seen heading north--still gaining altitude. It's hard to guess the distance, but I'd say 5 miles in 10 minutes (that'd make it 30 mph once it got up high).

Now, it's just wondering where it went, how far, and hoping that someone finds it and shoots back an email.