Traditional materials such as wood, steel, aluminum, bronze, iron, lead, lexan, Plexiglas, polyester, fiberglass, balsa cored fiberglass panels, foam cored fiberglass panels, paint and epoxies may be used. Carbon fiber and kevlar, shall not be used. Hull, deck, and house must be made from wood or fiberglass. Further material restrictions for individual items are located in their respective paragraph.
Titanium will not be used on Thunderbirds after January 26,1994. Titanium installed on Thunderbirds prior to January 29, 1994 may remain.
The use of materials not listed above as acceptable must be approved by the I.T.C.A. Measurement Committee.
The selection of wood is at the option of the builder except as listed below but all woods must weigh in excess of 20 lb. per cubic foot (320 kg/cu. m) at 15% moisture content. All plywood is to be of Marine or Exterior type. It is expected that the yacht shall be constructed in accordance with materials and techniques normally considered sound for yacht construction.
Fiberglass construction, with or without cores, may be substituted for the construction of the hull and/or deck and cabin prescribed in the plans, provided that they meet the following specifications.
k= (aT2 h-h2)1/2
where T is the period of one complete oscillation in seconds: h is the distance of the center of gravity below the pivot; and a = 0.248 if h is measured in meters and 0.81 if h is measured in feet.
NOTE: A builder may choose to install additional components into the hull before removing it from the mold. In this case, the weight, center of gravity and radius of gyration shall be determined with these components installed, and the builder's affidavit shall include a list of these additional components. their individual weights and their positions measured from the stemhead parallel to the waterline and below the sheer.