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ADDRESS REPLY TO THE COMMANDANT AND REFER TO NO. CA38/L11-1 (27-D3-576590) COMMANDANT'S OFFICE NAVY YARD, MARE ISLAND, CALIFORNIA CONFIDENTIAL   From: Commandant, Navy Yard, Mare Island To  : Chief of the Bureau of Ships Subject:     USS SAN FRANCISCO - Damaged Double Course Plating - Repair to References:  (a)  N.Y.M.I. Conf. Ltr. CA38/Al6(27-D3-576530) of December 22, 1942.  (b)  BuShips C&R Plan #167034 - USS SAN FRANCISCO - Main Deck Plating PN53-103  (c)  BUSHIPS C&R Plan #161808 - USS SAN FRANCISCO - Outer Shell Plating FN53-103 - 5th Long'l to Upper Deck  (d)  NYMI Plan #63942 - Damage Repairs to Double Course Shell Plating References:  (A)  Copy of reference (d)  (B)  Three photographic prints, M.I. #606-43, #607-43, #608-43      1.        This following report is intended to supplement information furnished by reference (a). Due to the special problems involved in the repair of the subject damage, copies of this letter are being forwarded direct to interested agencies in advance of the Bureau of Ships War Damage Report.      2.        During engagement described in reference (a), the USS SAN FRANCISCO received six hits which penetrated her double coarse plating. This plating extends in way of the shear strake from approximately frame 42 to 96. Three of these hits were from major caliber shells, causing a 16" to 20" hole and three were classified as from minor caliber shells. The repair of this damage, difficult at the outset due to the riveted S.T.S. double course structure was complicated further in three cases by damage to the H.T.S. deck stringer angle as well. Enclosures (A) and (B) illustrate the extent of the repairs that were required, and the discussion that follows describes some of the difficulties encountered snd procedures followed.      3.        In all cases of holes through double coarse S.T.S. plating, the restoration of structural strength was   - 1 -

(Continued) CA38/L11-1 (27-D3-576590) CONFIDENTIAL Subject: USS SAN FRANCISCO - Damaged Double Course Plating - Repair to - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - the primary consideration. In every case, three to five plates were damaged so that renewal of plating by riveting using the original butts would have been a formidable task, and would have resulted in the removal of much undamaged plating. A combination of welding and riveting was decided upon and a plan, reference (d), was drawn up wherein the procedure was carefully specified and locked-up stresses were minimized in the design by maintaining a free edge opposite the welded seam. In this manner only portions of plates needed to be renewed, and full advantage of existing riveted butts and seams was taken. A slight addition to strength of the seam was taken by eliminating airports in new plates, and blanking the adjacent ports with plating of full thickness.      4.        In establishing a shift in butts it was necessary to consider both the existing butts on the main deck stringer as well as the new butts on the two courses of shell plating. Due to the complicated nature of this problem it was not practicable to shift butts more than one frame space. At Frame 71, it was necessary to have two butts within a single frame space, and as an added precaution the welded joint was strapped.      5.        When the non weldable High Tensile Steel deck stringer angles required replacing, straps were installed at the new butts and these butts were welded for tightness.

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