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 TB 740-97-4
APPENDIX Q
DYNAMIC DEHUMIDIFICATION INSTRUCTIONS FOR
BOAT, PICKET, STEEL, DIESEL ENGINE DRIVEN
DESIGN 4003
1. General. This appendix provides detailed Instructions for preparation of the picket boat, design 4003, for dynamic
dehumidification.
2. Preparation Instructions. a. Disassembly and Stowage. The following items will be removed, identified and stowed
in the dehumidified area:
(1) Anchor, anchor fittings and rope.
(2) Handrailing and stanchions.
(3) Horn and bell.
(4) Stern light and staff.
(5) Navigation lights.
(6) Windshield wiper assemblies.
(7) Mast and jackstaff.
(8) Deck wrenches.
(9) Canvas covers.
(10) Life float.
(11) Hand bilge pump.
(12) Void compartment and rope locker access covers.
(13) Searchlight.
(14) Window glass.
(15) Emergency tiller.
b. Ventilation. The access covers to the rope locker and the voil compartment under the cockpit will be removed as
specified In a a above. The resulting openings will be blanked, and the blanks provided with gooseneck-or turbine-type
vents. The gratings for the access covers may be used in lieu of the ventilators when the boats are stored under shelter.
Hull plugs to the void compartments will be removed and secured adjacent to the openings.
c. Preparation for Dynamic Dehumidification.
(1) Dehumidzfied area. The washroom, quarters forward, engineroom, and cabin will be prepared for
dehumidification as a single zone.
(2) Provisions for air circulation The door to the washroom, all locker doors, access cover to engineroom in cabin
passage, the port and starboard bunk covers In the cabin, and the wood access cover on steering console will be secured
In an open position to permit circulation of the dehumidified air.
(3) Sealing for dehumidification. Methods and materials used In sealing for dehumidification will be in accordance
with this bulletin.
(a) Dehumidified area. Edges of doors, portlights, windows, hatch covers, and all other openings, in the nature of
seams or joints between closely opposed surfaces, which give access to the dehumidified area will be sealed with
strippable coating and bituminous coating. When sealing portlights, extend the strippable coating outward, over adjacent
surfaces of the bulkheads.
(b) Propeller shafting. Apply a seal of strippable coating around the propeller shaft at the stern tubes and at both
ends of the strut bearings.
(c) Cowl vents. The cowl vents will be fitted with minimum No. 26 gage galvanized sheet metal blanks and sealed
with strippable coating and bituminous coating.
(d) Steering cable. The opening for the steering cable, at bulkhead aft of the engine compartment, will be sealed with
strippable coating and bituminous coating.
(e) Louvered vents. The two louvered vents will be fitted with minimum No. 26 gage, galvanized sheet metal blanks
or exterior grade plywood blanks, properly secured, and sealed with strippable coating and bituminous coating.
(f) Hull openings. All openings In the hull, with the exception of deck drains aft, will be fitted with minimum No. 26
gage, galvanized sheet metal blanks and sealed with strippable coating and bituminous coating.
(g) Dehumidification piping system. The points of entry of all air ducts into compartments, the connecting joints of all
air ducts (including construction seam of the tubing) will be sealed with strippable coating and bituminous coating. The
sealing will be carried over and around flanges, adapters, and other devices used to attach or introduce the tubing or
ducts.
(h) Sluice valve. The sluice valve in way of the forward bulkhead of the engine compartment will be secured in a
closed position
(4) Dynamic dehumidification Installation.
(a) Dehumidification machine. A package dehumidifier, single desiccant bed, absorbent type, 10,000 cubic foot
capacity, 110-volts, alternating current, will be installed, generally, as shown on figure 59. The machine will be mounted
on a stand and protected with a cover fabricated, generally, as shown on figure 61. The machine will not service more
than a group of four boats.
(b) Air duct. Tubing, 4-inch diameter, No. 26 gage, with necessary fittings, supports and connections, will be
installed. Connection of ducts to the dehumification machine will be made by
Change 2
Q-1
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