up. Her deck beams, lateral and diagonal braces under the deck, a stringer plate connecting the deck beams with the sides of the vessel, continuous throughout her length, and the rail were of aluminum. The same metal was also used for dead-light frames and covers and small interior fittings. The sheaves of all her blocks were of aluminum.
I have read nearly everything that scientific men have written on the subject of aluminum as used in Defender, and from my reading I deduce that the metal failed to prove satisfactory because proper care was not taken to prevent oxidation by galvanic action. In the first place, bronze rivets were used instead of aluminum rivets, or iron rivets galvanized. Secondly, the insides of the rivet holes were not coated with white lead, nor were the rivets themselves dipped in white lead or paraffine before driving, as might easily have been done. In fact, no precaution whatever was taken to minimize galvanic action.
Mr. Herreshoff was advised to lay strips of heavy canton flannel well soaked in white lead between the lapping aluminum plates of the topsides and the bronze plates of the underbody, and then rivet up with the flannel between the edges of the two plates, forming a neutral joint. This precaution was not taken, however, the result being great corrosion where, through the
