TM 55-07/NAVSEA OP 3221 Rev 2
within the magazine, the obstruction must be covered completely with wood of at least /4-inch thick and secured with
nails or countersunk screws.
(4) Figure 7-27 illustrates the construction of the sides of a class "A" magazine. Bulkheads that form th
sides and ends are constructed of commercial 1-inch lumber, of 3/4-inch tongue- ndgroove sheathing, or of /4-inch
plywood. They are secured to uprights of at least 3by 4-inch stock, prefeirably 4by 4-inch stock, and spaced on 18inch
centers. Uprights can be spaced on 24-inch centers if /4-inch plywood is used.
(5) When a class "A" magazine measures more than 40 feet in any direction, a partition bulkhead will be
installed to divide the stowage area approximately in half. The bulkhead should extend from the deck to at least the top
of the stow. Boarding should be alternately spaced not more than 6 inches apart on both sides of the uprights.
b. Portable Class "A" Magazine. Portable magazines are constructed for stowage of certain classes of explosives,
as authorized by the provisions of 46CFR146.29-100. These magazines are constructed of wood or metal lined with
wood at least 3/4-inch thick. Not more than 100 cubic feet of explosives plus 10 percent of explosives (gross) will be
stowed in a portable magazine.
(1) Construction details of a portable class "A" magazine are shown in figure 7-29. When a portable class
"A" magazine is to be constructed of wood, the general materials and dimensions used will not be less than those
required for a nonportable-type "A" magazine. It is recommended that 4by 4-inch uprights be used exclusively in the
construction of magazine runners, uprights, and cover support members. Spacing of uprights should not be more than
24 inches on centers if 4by 4-inch material is used. The magazine shell is constructed of a single course of minimum 1-
inch commercial lumber, although 2-inch material is recommended for added rigidity. Plywood sheathing three-fourths of
an inch in width or tongue-and-groove sheathing three-fourths of an inch is also acceptable for construction of the shell.
All inner surfaces of the shell should be smooth and free of nails, screws, or other projections.
(2) After completion of the basic magazine, the magazine interior and cover are protected with a moisture
barrier of polyethylene or waterproof paper at least four-thousands of an inch thick. The barrier material should be
installed as a single piece; however, overlap of pieces is sometimes necessary. Water runoff will be directed toward the
magazine exterior by overlapping of the bottom piece over the top piece as shown in figure 7-30. Portable magazines
stowed in a hold where protection from the weather is not a factor do not require moisture-barrier construction.