A rocket stove is easy to build and require a large metal can, a metal duct elbow with an opening measuring 4 inches, a 40-ounce can with an opening of 4 inches and some insulating material. To build the stove, fit the duct in the large can, attach the 40-ounce can to the duct, and put insulating material in the large can.
Begin making the rocket stove by cutting a 4-inch hole in the large can's side. To make the hole, use the 40-ounce can with an opening 4 inches in diameter as the template. Mark the hole such that its bottom is positioned 2 inches above the can's bottom edge. Cut the hole using tin snips. Push the duct elbow in the hole from within the can. Allow 2 inches of one of the duct's ends to jut out from the can's front. Ensure the elbow's other end points in an upward direction and is approximately centered in the can. Support the elbow from beneath using a brick piece or stone.
Put insulating material such as sand, perlite and vermiculite around the duct in the large can. Fill until the materials sit about 1 inch from the elbow's top. Next, cut a hole 4 inches in diameter in the center of the large can's lid. Position the lid over the elbow, and let it sit on the insulating material in the can. Then, snip the bottom of the 40-ounce can, and slide it snugly over the end of the elbow that juts out from the can.