Hot air balloon feedback

A bit of feedback on this particular session "Full of hot air"

Equipment/Materials: No template was supplied in any of my three boxes.  I figured it out and made my own from cardboard, but it would have been nice had each box come with one.

Process: This was very challenging for the younger kids. 

Cutting out the shape reasonably accurately was somewhat hard - the paper shifts around while cutting throwing some copies "off".  I found a solution during pre-session testing, I used a couple of paper clips to hold the sheets of tissue paper together while cutting and that seemed to make it accurate enough.

Glue sticks need to be used on tissue paper with great care or else you'll rip it, but in order for the balloon to hold together you have to use a heavy, thick line of the blue.  Taken together, this is very hard especially for the 3rd and 4th grade kids.

We found when gluing together pieces you had to be quick - if you let the glue dry much at all before pressing the two pieces together the resulting seam was not strong enough.  You don't have to *rush*, but you do have to be reasonably quick.  Unfortunately, the kids are already dealing with getting a thick enough glue line on the paper, having the tissue not tear, then trying to line up that new sheet of tissue paper over the old and press it down, without getting it too crooked (because it's very hard to remove again to reapply).  This was also very hard and many mistakes were made.  I found that it helped this process if you laid the two pieces needing stuck together side by side, both folded and aligned such that if you put glue around the outside edge of one, you could just "unfold" the other balloon segment right on top.  As long as your folds were pretty consistent, this got you 90% of the way to proper alignment.

Applying the collar to the balloon is, in my opinion, done in a way that won't work well.  The point of the collar can't be to tightly couple the hair drier with the balloon when you "fill" it because if you did that, you would have to insert the hair drier, turn it on, then turn it back off again right away.  The hair drier only *just* starts putting out hot air by the time you have to turn it off, so you've just filled the balloon with cool or maybe warm air.  I tested this several times and the air inside isn't very warm when you have to do it this way, and you can't leave the drier run for any time because there's nowhere for the air to escape to so you stress your seams and will have a blowout.  I found it was better to make it loose enough that when you insert the hair drier into the collar, there's a gap of an inch or more.  This way you can run the hair drier for several seconds until the air blowing out around the collar is actually very warm or even hot, ensuring that you've given the hot air balloon as good of odds as is possible for it to at least float for a few seconds, or at least fall as slowly as possible.

When you finally try putting air in them, we found that nearly all had repairs that were needed because the gluing was very difficult to get right. And repairs were hard in many cases.

I downplayed the expectations very, very significantly, because in my testing I simply couldn't make a balloon that would even "hover" for a few seconds.  It even says in the handbook to mention that they're not really going to "float up into the air".  They all sunk, though some fairly slowly.  I even tried in our 50F garage, figuring the difference in temperature would help.  It did a bit, but not enough to make it excitingly buoyant.  I made sure all the kids were aware that these weren't going to float upwards much at all, if they floated upwards *at all*, and I think the kids ended up pretty happy about the end results - not because they were great results but because their expectations were set so low, so anything better than "plummet to the ground" was pretty exciting.  So as far as that goes, it did end up working out better than I initially expected, just not as good as I would have hoped or enough to outweigh the difficulties in building them.

We also tried using a heat gun - 700F instead of the hair drier's 400F.  I thought perhaps increasing the temperature of the air inside the balloon would be just enough to make it rise a bit on its own, but even that wasn't enough (though they did float downwards even more slowly, and perhaps one or two sort of did float.  Almost.)

We even tried a double-sized one.  I hadn't been able to test this one before so it was a great experiment in the classroom after we talked about volume to surface area ratios to see if it did any better.  It was 3 feet in diameter made of 12 pieces of tissue paper glued together.  I hoped that the extra volume would be enough to make it actually float.  It did sort of hover better and fall more slowly.

I think this was a difficult, challenging lab with somewhat disappointing results.  If they had really floated well, then the results would have made the effort worth it.  If it had been an easier/faster lab even with somewhat disappointing results, then the outlay in effort would not have been too high for those results.  Add the two things together and they made it hard without a payoff at the end.  All we really ended up building was complicated, hot-air-balloon shaped fall arrestors.  Some of our parachutes from the last section of this module actually spent longer in the air than some of the balloons.