■ FIGURE 4. At this point, the sides have been glued to the
bottom and middle decks.
■ FIGURE 5. Test-fit of the video camera.
wires between the upper and lower bays. Later, I decided
to attach a small digital video recorder to one face of the
BalloonSat. However, I didn’t know which face at the time
as the design could support a hatch on one face or on
two opposite faces. Therefore, I cut both notches large
70 July 2012
■ FIGURE 7. The airframe now has a top. The four holes
drilled for the tubes are now visible. They are near the
corners of the top deck.
enough for the camera. That let me put off deciding which
face gets the video camera until later.
I then stacked the middle deck and tubes on the
bottom deck of the airframe. The digital camera looks out
the bottom of the BalloonSat and so has to be mounted
into the lower bay. Like most cameras, this one is designed
to be mounted to a tripod using a 1/4-20 bolt. I placed
the camera on the bottom deck so its base would be up
against the future wall of the airframe. Then, knowing
where the camera will lay, I cut out a hole in the bottom
deck for the camera’s lens. To prevent sunlight from
causing glare, I then blackened the edges of the camera
Next, I used hot glue to attach three of the airframe
sides to the decks. I only attached three, since the fourth
side will be the hatch of the BalloonSat. The camera was
checked one more time to make sure that it still slid into
the lower bay. I also measured the location for the
camera’s 1/4-20 threaded hole. Before drilling the 1/4
inch hole, I first drilled a small test hole in the airframe to
double-check that my placement was accurate. After
verifying the hole was properly placed, I finished drilling
the larger hole for the bolt.
Before gluing the top to the airframe, I test-fitted the
video camera. As you can see in Figure 5, it fits into the
airframe and looks out the hatch. It was also at this point
that testing showed that trying to snap the 9V battery into
the holder would be a bad idea.
The stress and strain created by snapping the battery
into the metal holder would eventually break the Cellfoam
88 of the middle deck. Therefore, I replaced the metal
battery clip with a Styrofoam box made with 10 millimeter