--- /dev/null
+[[meta title="Balloon twisting"]]
+
+[[tag make]]
+
+Last Saturday, Kevin and Debbie staged a rather impressive backyard
+carnival for Ethan's 5th birthday party, (inflatable jumphouse,
+bean-bag toss, petting zoo, etc.). I was invited to volunteer as the
+balloon animal guy. I'd never done balloon animals, but Debbie figured
+"if he can fold paper, he can certainly twist balloons".
+
+## The Basics
+
+So I picked up some balloons a few days before the event and started
+twisting. The basics were easy enough to discover:
+
+* Don't try to inflate the balloons with lung power, get a little hand pump.
+
+* Don't inflate the balloons all the way.
+
+* After inflating the balloon to the desired length, let a little air
+ out to make it more flexible and easy to work with.
+
+* Don't be afraid—just start twisting and see what happens.
+
+## The Party
+
+And it was easy enough to make some simple shapes, (poodle, wiener dog
+and sword), without looking at any specific instructions. As it turns
+out, the kids at the party were more than happy with these—and
+there's definitely an advantage to sticking to models that are really
+quick when there's a line of kids waiting.
+
+[[img balls.jpg size="297x150" class="left"]]
+
+I'd meant to do at least some googling and find something more
+interesting to make, but I neglected to do that until just before the
+party. So I didn't have time to look at more than one site. I learned
+a baseball cap model there, and also a really intriguing volley ball
+from three balloons (pictured here). It's slick because none of the
+balloon knots or twists are visible—plus it actually works pretty
+well as a ball for bouncing around in the air.
+
+I was feeling unprepared, so I kept twisting things in the car on the
+way to the party, (fortunately, I didn't quite cause an accident—no
+I wasn't driving, but the growing pile of balloons in the front seat
+did start distracting Stacy while she drove). On the way I figured out
+how to do a nice flower, (which, later at the party I made into a
+flower hat), and I also invented my first original design—a frog hat
+with oversized lips that can be squeezed to make it "talk". (Sadly, I
+was too busy doing balloons to actually take any pictures that
+day—and I'll have to figure out how to post video clips to do that
+one justice.)
+
+## The Project
+
+Anyway, the party was a lot of fun, and I was glad I could help
+out. When I got home I still had a couple of packs of balloons and I
+was still intrigued by that ball design, and wondered if similar ideas
+could be used to make something more elaborate. As with origami, I
+seem to be drawn more to the intricate geometric models rather than
+anything more organic like animals, (I think that's because my
+non-artistic brain can deal with "fold in half" much more easily than
+"fold at an angle that looks right for the beak").
+
+My thoughts landed on Tom Hull's fantastic [five intersecting
+tetrahedra](http://www.merrimack.edu/~thull/fit.html) origami design
+which I'd constructed once before as a gift, (I'll have to do it again
+and take a picture). So my pointless project for the weekend became
+recreating the structure from balloons.
+
+I started by twisting each balloon into thirds, hoping I could get by
+with just inflating 10 balloons, (2 each of 5 different colors). But
+it was quite easy to see that balloons would be too thick at that
+size. It was also really hard to weave each tetrahedron while having
+to hold three different balloon segments to keep them from untwisting.
+
+So next I attempted with full-length balloons. This would require 30
+total, (6 each of the 5 colors), but would make it much easier to
+assemble, since each beam could be threaded independently, (much like
+the process with the origami model). But as soon as I built one
+tetrahedron, it was plain to see that the balloons were too thin at
+that large size and the whole structure would be far too loose, (but
+the kids did like using the resulting tetrahedron as a playhouse for
+the afternoon).
+
+[[img five_tetrahedra.jpg size="225x225" class="right"]]
+
+So the final structure uses 15 balloons, (3 each of 5 colors). Each
+balloon is inflated nearly all the way and then twisted once in the
+middle. This makes each segment in the final structure just short of 2
+feet long while the balloons have a diameter of about 2 inches. And
+now that I'm typing instead of twisting, I actually went and read that
+Tom's origami design also uses a 1:12 ratio. So I could have saved
+myself some work experimenting by just reading that first. I did
+consider solving for the perfect ratio before starting with the
+balloons, but it's not easy for me to grasp the 3D geometries. Anybody
+care to help me solve that one? Tom also leaves the perfect ratio as a
+problem for the reader.
+
+It's really a beautiful structure when complete. A single picture
+probably doesn't capture it very well. It's much more pleasing to be
+able to examine it in person and view it from many angles. Also,
+assembling the structure is actually a fun puzzle to solve, and I
+think forces the solver to gain a new appreciation for some of the
+symmetries inherent in the design. It had been 2 or 3 years since I
+had done this in origami, and I really had to learn the model all over
+again before I could get everything threaded correctly.
projects / cworth.org / commitdiff
