20 minute job - wound the boiler coil. The lower portion is a spiral column that decrease in diameter as it goes up, then halfway up the coil, the tubing is wound as several layers of concentric circles. I don't invent this pattern, but copied a design that is used by a professional monotube boiler maker. The difference is, he fires his boilers with wood and I will use propane and this one is about 1/4 the size of what he makes. Mine also uses smaller diameter tubing. I was surprised to get the entire 50' roll to fit. Next, I get to do the tedious task of wiring the coils together to make them compact and stable. The wires will hold the coils in position but will also keep them separated so the heat can flow through.