Sew the first row using a 1/4-inch (0.64-cm) seam allowance and the second row using a 1/2-inch (1.3-cm) seam allowance. Use a straight stitch and a matching thread color for both rows. Do not backstitch. Use a long stitch length and a low tension on your sewing machine. This will make gathering it easier. Place the middle tier into the bottom tier. Find the bobbin threads from your 2 rows of stitching, then pull on them to gather the fabric. Keep pulling until the gathering edge matches the circumference of the middle tier. Knot and cut the excess thread. Cut the excess thread first to make it easier to manage. Tie the threads together, then trim the rest off. Double-check to make sure that the right sides of the tiers are facing each other first. Since the tiers are already tucked inside each other, all you have to do is pin and sew along the top edge with a straight stitch and a 1/2-inch (1.3-cm) seam allowance. Remember to backstitch and to take the pins out when you are done! Fold the seam against the middle tier. Secure it with sewing pins, then sew across it with a zigzag stitch. This will give you a cleaner finish as well as prevent the seam from scratching you. Sew 2 rows across the top edge of the middle tier. Gather the top edge until it is the same circumference as the top tier. Pin and sew the 2 tiers together with a 1/2-inch (1.3-cm) seam allowance and a straight stitch. Fold the seam against the top tier and topstitch it down with a zigzag stitch. The top tier isn't sewn together into a ring yet. You will have to coil the top tier into a ring and tuck it inside the middle tier to check the size. This includes all of the measuring, cutting, gathering, and sewing. When you are done, tuck 1 petticoat into the other with the wrong sides facing in. Sew along the top edge of the petticoat using a straight stitch or a zigzag stitch to hold them together. You are sewing the petticoats with the wrong sides facing in so that you have a clean finish on the inside and outside of the petticoat. For a more colorful petticoat, consider using different colors for each layer.
++++++++++
One-sentence summary -- Sew 2 rows of straight stitches along the top edge of the bottom tier. Gather the top edge until it is the same size as the middle tier. Sew the bottom and middle tiers together using a 1/2-inch (1.3-cm) seam. Fold the seam against the middle tier and topstitch it down. Repeat the process with the middle and top tiers. Repeat the entire process if you want a 2-layered petticoat.

There are a few different types of solar cells to buy, and most good options are either made in the United States, China, or Japan. However, the best cost-to-efficiency option is most likely polycrystalline cells. The number of cells you should buy depends on the amount of energy you're looking to produce. The specs should be listed when you purchase the cells. Make sure to buy extras. These cells are extremely fragile. Cells can most easily be bought online through websites like Ebay, but you may be able to purchase some from your local hardware store. It may be necessary to clean wax off of the cells, if the manufacturer ships them in wax. To do this, dip them in hot, but not boiling, water. Each cell shouldn't cost more than $1.30 per watt. You will need a thin board made out of a non-conductive material, such as glass, plastic, or wood, to attach the cells to. Lay out the cells in the arrangement you will use, then measure the dimensions and cut a board to that size. Leave an extra inch or two at both ends of the board. This space will be used for the wires that connect the rows together. Wood is a more common backing material to choose because it's easier to drill through. You'll need to drill holes in it for the cell wires to pass through. When you look at your polycrystalline cells, you'll see a large number of small lines going in one direction (the long distance) and two larger lines going in the other direction (the short distance). You will need to connect tabbing wire to run down the two larger lines and connect to the back of the next cell in the array. Measure the length of that larger line, double the length, and then cut two pieces for each cell. Using a flux pen, run 2-3 lines of flux down the length of each cell strip, or group of three squares. Make sure to do this on the back of the cells. This will keep the heat of the soldering from causing oxidation. Use a soldering iron to melt a thin coat of solder onto the back of the cell strips. This step is not necessary if you purchase pre-soldered tabbing, which is often a better option because it cuts time in half, heats up the cells only once, and wastes less solder. However, it's more expensive. Heat the first half of a piece of tabbing wire with a soldering iron. Then bond the wire's end to a cell. Repeat this bonding process for each cell.
++++++++++
One-sentence summary --
Purchase the cells. Measure and cut a backing board. Measure and cut all of your tabbing wire. Flux the work area. Solder the tabbing. Bond the wire to the cells.