Looking for something to do with old CDs and spotted a video on YouTube with the hovercraft idea. They used superglue on that video but I didn't want to chance that if my grandchildren tried this, so I used a hot glue gun to do the job. There is a new version of this project which includes trying it on water youtu.be/aOrlP7dvd4M
I think there is probably an optimal size of balloon. The small one I used did not last long. I tried a much larger balloon but that was too heavy so I guess it will just be a matter of try it yourself.
I have noticed from other peoples videos that they blow up the balloon first then attach it to the bottle top. This gets over the problem of blowing through the bottom of the CD when it gets dirty after has been on the floor. Seems like a sensible approach to me.
Some people have asked what is the purpose of this experiment so I searched YouTube and found this example by AirFloat "35-ton Load Floats on Air" https://youtu.be/t6m01VGiNPI#
I found this article whilst surfing the web and thought that people who are interested in this type of hovercraft would be interested rippl3d.com/hover-craft-challenge-1-0/
Karolis Giedratis asked if it worked on water. I have tried it on water and it unbalances and tips over so all the air escapes. Interestingly it still moves forwards but that is because it is being pushed through the water by the air bubbles, not floating on a cushion of air.
Drink bottle resealable top
You can make this with any suitable sized tube but it may be more difficult to fix to the CD and you have to hold the balloon to stop the air releasing before you are ready.
Hot Glue or Superglue
Hot Glue Gun or Superglue
You may need a saw to cut the top off the drink bottle if it is different to the one I used.
In reply to the few people who say they have failed to get this working this YouTube search gave me 3440 results and just the first page shows plenty of people having success www.youtube.com/results