These fins may have a more scientific name, but most of the sites just refer to them as “fins,” so we will too. Their purpose is to distribute the heat to or from the tubing which runs through them. The fins serve one of two purposes, depending on the application. In a solar water heater, the fins, usually painted black, help absorb the heat from the radiant energy of the sun and transfer that heat to the tubing, heating the water in the tube more efficiently. In a radiant floor, the heat from the water running through the tubing is transferred from the tubing to the fins to more evenly distribute the heat to the floor above.
To buy these for either application is kind of expensive ($6-12 each), considering the ease with which they can be produced with various homemade contraptions. As you look through the information in the BuildItSolar.com link, we have used another way to form these fins. We built two 8-foot forming jigs (much like the one illustrated under the “Sledgehammer Press” in the BuildItSolar.com link). Then we load up the jigs with two 4-foot pieces of metal on each jig, throw on the metal pipe, and put them inline with the tires of the car and run over them as we leave the house – slowly, so as not to spit the metal out or roll the pipe off. When we get home from work or errands, we run over them again on the way into the garage. Then we take them out of the jig before we go into the house and load them up again for the next day. Yes, we’re only making four fins at a time, but we make four fins every day until we’re ready for the next project – and we spend a total of 2 minutes per day on them.
Whatever the use, the process for creating these fins is the same.