For over two decades, balsa wood has been employed in many applications as a core material. This type of sandwich construction has helped designers and engineers to achieve superior construction and performance in such diverse products as commercial boat hulls, decks, transoms, chain walls, air cargo pallets, aircraft floorings, partitions, buffets and lavatory doors and portable containers, flooring and bulkheads for high speed rail cars, molded water skis, and others. There are four steps to constructing concrete forms with balsa-cored fiberglass. Step one, a black gelcoat is applied against mold, approximately .20 inch thick. This is followed by a glass polyester spray up three-sixteenths of an inch thick, which is hand-rolled to eliminate any air bubbles. It is then allowed to cure. Step two, a glass spray-up (resin-rich) approximately one-sixteenth inch thick is applied. Then a three-fourth of an inch thick balsa core in the shape of a contourable sheet is nestled into the wet glass. After contouring to curved shape of mold, the operator trims excessive materials where required. Step three, it is then hand-rolled to assure positive bonding. The panel is placed glass side down and a three-sixteenth inch overspray is applied. Step four, after rolling out air bubbles, additional stiffeners of plywood are added at this stage at the joining sections. Curing follows. The form is then removed from the mold and trimmed of excess fiberglass.