Building Your Own Airship Envelope
Created by Pecktec on 9/23/2013 7:57:17 PM

Building Your Own Mylar Airship Racer Envelopes

I started working on this project thinking I would be able to use a commercial balloon to lift my airship. As the airship became heavier and heavier it was apparent that I would need more volume than I could conveniently find, so I opted to make my own. After some searching online, I came across a webpage called BALLOON KITS They have everything you need to make your own custom balloon as well as detailed instructions with photos to reference. I had considered other types of foil (like an emergency blanket) but it turns out the balloon film has a waxy coating that allows it to seal.

Luckily I already had some of the tools I needed. I had a craft iron from some model air plane projects and my soldering iron has a hot knife attachment. I chose to purchase the 38" x16 yd. roll of foil, which arrived in about two weeks. It cost around 30 bucks and I used about half of it  – so I figure I could have gotten two tries out of that order.

I tried to follow the instructions as closely as I could but I was also working on a deadline as Dragon Con was a mere two days away. So, I did cut a few corners. I had picked up a balloon that could almost lift the gondola so I decided to use this as a loose template.  I used a large roll of paper and rolled it out on a piece of plywood I'm using as a table. I took the roll of foil and rolled it out as flat as possible then using a clamp to hold it down I rolled it back onto itself. The Mylar film is very thin and fussy so getting it flat was a bit of a chore. I laid the deflated balloon I was using as a template on the film. All I knew for sure was that it needed to be markedly larger than the template. I also wanted a large seem so I could use it to attach the gondola.  I took the craft iron and tested the heat on a scrap piece. Seeing that it sealed it just fine I started making my way around the template.

It’s important to think about where you want to inflate the balloon at this point. The commercial ones have a self sealing mechanism. For do- it- yourself, you will simply need to make a longish filling stem. Be careful not to seal it in. When the balloon is done you will use this to fill it with helium then roll it up and tape it shut. I made my way around the template making sure I was making a much larger balloon. I then broke out the hot knife (It’s way too thin for scissors or the Exact-o blades that I tried at first) and cut around the outer edge of the sealed portion. I then, very carefully, pulled up the scrap Mylar. I went around inspecting the seam the best I could and repaired it in a few places. The next day I took it to party city and filled it up. It was about $4.00 to fill it up -- mostly because they had to guess at the size.

Immediately I noticed a leak. It wasn't horrible; just a small spot. When I got home, the balloon had deflated somewhat and we went about finding the leak. My wife held the balloon for me as we flattened the affected area onto the table. I used the iron to reseal it the best I could, and it worked beautifully.

Because I live in TN and this had to make the trip to GA that day, I didn't add any more helium. I picked up a disposable tank on the way out of town, and, on race day, we filled it the rest of the way.  

This first attempt at the airship envelope wasn't nearly as difficult as I imagined, although the envelope was far from symmetrical and a little odd looking. I have enough foil to make another large balloon so I think next time I will do a proper template and make it a bit slower to get a nicer looking balloon. All in all, it was lots of fun and super easy.

Click any image below to see larger version.

Lay out Mylar
Iron shape Mylar
Cut Out Mylar
Trim Mylar
Finished Custom Mylar
The ship is ready


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