Code of Federal Regulations Title 46. Shipping § 46.178.450 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=.1xBasic Drainage

For partially protected waters required drainage=.5xBasis Drainage

For exposed waters required drainage=Basic Drainage

where:

Basic Drainage area in centimeters²=4389.12x[(Recess VolumexRecess Ratio)+(Weather Deck VolumexWeather Deck Ratio)];  or

Basic Drainage area in inch²=(Recess VolumexRecess Ratio)+(Weather Deck VolumexWeather Deck Ratio)

Recess Volume=(B_RxD_R) − V_R

B_R=average height in centimeters (feet) of the bulwark above the well deck or cockpit deck;

D_R=total deck area of the cockpit or well deck in the after 2/3 of the vessel length (LOD) measured in centimeters² (feet²).

V_R=volume of any weather tight structure below the bulwark of the well deck or cockpit deck.

Recess Ratio=L_R/L_C

L_R=the length of the recess in the after 2/3 vessel length (LOD).

L_C= 2/3 vessel length (LOD).

Weather Deck Volume=(B_DxD_D) − V_S

B_D=average height in centimeters (feet) of the bulwark above the weather deck;

D_D=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 centimeters² (feet²).

V_S=volume of any weather tight superstructure below the bulwark on the weather deck located within D_D.

Weather Deck Ratio=L_D/L_C

L_D=the length of the weather deck bulwark in the after 2/3 of the vessel length (LOD).

L_C= 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.