Step 5: Building the Blimp Frame
Now you need legs for your blimp. I had the Apollo moon lander in mind when I did mine, and trust me, they're worth it -- they protect your precious equipment from impact damage, and balsa is so light that the weight added is practically negligible. Mine are 6" long, at an angle of about 45 degrees below horizontal. Cut / file the ends of each leg so that when the 'foot' is flat on the ground, the leg is at 45 degrees, and the 'top foot' is parallel to the horizontal. Now glue each leg into place so that they stick out to the sides, with the feet more or less flat (you're going to glue cotton balls to them, so it doesn't need to be perfect).
You'll need triangular supports for the legs, otherwise they'll bend out and snap under weight. Cut them to the same angle as the legs, with each of the smaller sides 1" long, and glue them onto the legs and the larger frame. Your blimp should be able to stand up now, so glue some cotton balls to the feet for soft landings.
One more thing to add in this step: the battery box. The battery is by far the heaviest component, so you want it to be exactly centered. Measure the dimensions of your battery, then use these to measure from the sides and sketch a box in the center. Make sure your battery fits before you glue the balsa, and leave a small gap for the wires to poke out.