Using a straightedge and sharp knife or a pair of scissors, cut a 4" strip from the full length of the edge of the 38" piece of fiberglass cloth, and set it aside for the inside keel. Be careful handling the cloth after it's been cut to keep the edges from un-raveling. Roll the remaining piece of fiberglass cloth out on the bottom of the upside-down hull, and trim the edge with a pair of scissors so that it hangs over the first lap by about an inch. Save the piece that you cut off to use for the stems.