§ 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 Basic Drainage

For exposed waters required drainage = Basic Drainage

where:

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

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

Recess Volume = (B_R × D_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_D × D_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 centimenters² (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.

[CGD 85-080, 61 FR 966, Jan. 10, 1996; 61 FR 20557, May 7, 1996; 88 FR 10032, Feb. 16, 2023 ]