Granted, the two men had no prior ballooning experience, but hey, they found a few books on the subject and took it from there. They did the math, bought hardware and cloth ("it's for our camping club") in the nearest town and got busy building. The sewing machine they used for the hull was a 40-year-old foot-pedal dinosaur. They built a firing system out of a bike engine, a car muffler and a stovepipe that spat out "pure Hell-fire."
A few failed tests in the woods proved that the cloth was too porous to hold the air. The hull was cut up and burned in the furnace while new cloth ("it's for our sailing club") was procured from a more faraway city. Then they started over. When the old manual sewing machine threatened to wear them out physically, they just fitted it with an engine.
It could use some spinners, too.
The Strelzyk family launched the balloon (the Wetzels had gotten cold feet and opted out of the plan) after a total preparation time of 16 months. They sailed through the air, got within sight of the border ... and crashed. Six hundred feet short of freedom.