 The Shōkaku class had a waterline belt that consisted of 46 millimeters ( 1 @.@ 8 in ) of Copper @-@ alloy Non @-@ Cemented armor ( CNC ) that covered most of the length of the ship . The belt was 4 @.@ 1 meters ( 13 ft 5 in ) high , of which 2 meters ( 6 ft 7 in ) was below the waterline . The lower strake of the armor was backed by 50 millimeters ( 2 @.@ 0 in ) of Ducol steel . The magazines were protected by 165 millimeters ( 6 @.@ 5 in ) of New Vickers Non @-@ Cemented ( NVNC ) armor , sloped at an inclination up to 25 ° and tapered to thicknesses of 55 – 75 millimeters ( 2 @.@ 2 – 3 @.@ 0 in ) . The flight and both hangar decks were unprotected and the ships ' propulsion machinery was protected by a 65 @-@ millimeter ( 2 @.@ 6 in ) deck of CNC armor . The NVNC armor over the magazines was 132 millimeters ( 5 @.@ 2 in ) thick and 105 millimeters ( 4 @.@ 1 in ) thick over the aviation gasoline storage tanks . All of the deck armor was overlaid on a 25 @-@ millimeter deck of Ducol steel . 
