CFR > Title 46 - Shipping > CHAPTER I—COAST GUARD, DEPARTMENT OF HOMELAND SECURITY > SUBCHAPTER T—SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) (parts 175 to 186) > PART 178—INTACT STABILITY AND SEAWORTHINESS > SUBPART D—Drainage of Weather Decks (§178.410 to §178.450) > 178.450—Calculation of drainage area for cockpit and well deck vessels.

178.450—Calculation of drainage area for cockpit and well deck vessels.

(a) The drainage area required on a vessel must be computed using the following formula:
For protected waters required drainage = .1 × Basic Drainage
For partially protected waters required drainage = .5 × Basis Drainage
For exposed waters required drainage = Basic Drainage
where:

Code of Federal Regulations

Basic Drainage area in centimeters2 = 4389.12 × [(Recess Volume × Recess Ratio) (Weather Deck Volume × Weather Deck Ratio)]; or

Code of Federal Regulations

Basic Drainage area in inch2 = (Recess Volume × Recess Ratio) (Weather Deck Volume × Weather Deck Ratio)

Code of Federal Regulations

Recess Volume = (BR × DR) − VR
BR=average height in centimeters (feet) of the bulwark above the well deck or cockpit deck;
DR=total deck area of the cockpit or well deck in the after 2/3 of the vessel length (LOD) measured in centimeters2 (feet2).
VR=volume of any weather tight structure below the bulwark of the well deck or cockpit deck.

Code of Federal Regulations

Recess Ratio = LR / LC
LR=the length of the recess in the after 2/3 vessel length (LOD).
LC=2/3 vessel length (LOD).

Code of Federal Regulations

Weather Deck Volume = (BD × DD) − VS
BD=average height in centimeters (feet) of the bulwark above the weather deck;
DD=total deck area of the weather deck adjacent to bulwarks but not in way of the cockpit or well deck in the after 2/3 of the vessel length (LOD) measured in centimenters2 (feet2).
VS=volume of any weather tight superstructure below the bulwark on the weather deck located within DD.

Code of Federal Regulations

Weather Deck Ratio = LD / LC
LD=the length of the weather deck bulwark in the after 2/3 of the vessel length (LOD).
LC=2/3 vessel length (LOD).
(b) Vessels with bulwarks in the forward part of the vessel shall not form a well with the deckhouse which retains water.
[CGD 85-080, 61 FR 966, Jan. 10, 1996; 61 FR 20557, May 7, 1996]