Step 11: Fill the Envelope

The pictures show the envelope at several stages of filling. Make sure to duct tape a string or two onto your envelope before you fill, so you have something to anchor it with. I use clamps to hold down my anchor strings when filling.

Your balloon should fill up nicely if you use enough reactants, but don't be surprised if it takes five or six hours. The reaction will start to die off exponentially, and all the little bits of aluminum will float to the surface because they've lost so much mass. At this point, you can leave it for another day to collect all the last bubbles, or just pop off the lid and be done with it.

During filling, use a wet finger to check the one-way valve where your tube enters the envelope for gas leaks -- If you find any, apply duct tape. I have this problem, as the valve on my balloon has a rip in it, so once the envelope is done filling I press a piece of duct tape firmly over the filling hole and that holds the gas nicely.

If you have a buffer bag, put a clamp on the end and let it collect the excess gas -- if it turns out you need more, you'll have some.

Here's a video of the envelope filling (I know there's no cooling basin, I added one later):

<p>Can something be sprayed onto a plastic wrap skin, to help hold in the hydrogen gas? I'm trying to keep it light, but don't want the gas to leak out too quickly. Really cool project.</p>
<p>Do you have any idea how much weight (gram) the blimp can lift ? </p><p>Thanks</p><p>Sam</p>
You blimp looks awesome, only the code is without any doubt the most incomprehensible code I have ever seen! I can't make heads or tails from it. Could you explain the how te code works? I really like the 433 MHz set I got, but I haven't found a clear code that I can adapt to my homemade rover. <br> <br>Thom
Darn, I have been trying to figure out your code for quite some time, IT-IS-SO-SIMPLE, I have tried to use virtualwire but then I can't use the servo library (they hate each other). Thanks for sharing it!
when I first read the title I accidently read &quot;Hydrogen bomb.&quot;
Nice work on this project! I had the same 433 Rx Tx units and could never get them to communicate properly! Definitely one of the best troubleshooting sections I've read!
this soo reminds me of the hindenburg. tho to be fair, hydrogen had nothing to do with the explosion. zinc paint(?!) was the problem. <br>very cool project. <br>tho 433mhz might not be legal in USA, but even a toy car with arduino could work
You are my hero. I have tried filling a smaller blimp with hydrogen in the same way, but using only very small amounts of lye (five attempts with no success). I would love to build a setup like this some day, especially one using a hydrogen fuel cell for power. One question: does the water buffer remove any steam or water vapor from the hydrogen entering the envelope? I always worried about getting water in it. Thanks for a very informative 'ible.
You're right to be worried about water vapor. It will only be a problem if you let the reaction get too hot, which will make it start steaming or even boil if it gets out of hand. If you make sure it doesn't get more than a little warm ( I dunno, 75 deg F), the water vapor will be negligible. If you're really worried about it, you could try running the gas through a percolator to cool it down before it enters the envelope (meaning some of the vapor would condense out). The buffer I have is mainly to prevent any water in liquid form that bubbles up from getting close to the envelope. Don't give up on lye!
Awesome. Love the chemistry lab details and the troubleshooting section.

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