46 C.F.R. §§ 42.20-3–42.20-13

A Type “A” vessel is assigned a freeboard not less than that based on table 42.20-15(a)(1) provided that the vessel meets the flooding standard in § 42.20-6.

A vessel that meets the requirements of subpart D, F, or G of part 172 of this chapter is considered by the Coast Guard as meeting the flooding standard referenced in paragraph (a) of this section.

Each Type “B” vessel is assigned a freeboard from table 42.20-15(b)(1) that is increased or decreased by the provisions of this section.

Each Type “B” vessel that has a hatchway in position 1, must have the freeboard assigned in accordance with paragraph (a) of this section increased by the amount given in table 42.20-5(b) unless the hatch cover complies with:

Any Type “B” vessel that is greater than 100 meters (328 feet) in length and any hopper dredge meeting the requirements in subpart C of part 44 of this chapter may have a reduced freeboard from that assigned under table 42.20-15(b)(1) in accordance with paragraph (d) or paragraph (e) of this section if—

The freeboards for a Type “B” vessel which comply with paragraph (c) of this section may be reduced up to 60 percent of the total difference between the freeboards in table 42.20-15(b)(1) and table 42.20-15(a)(1) provided that the vessel meets the flooding standard in § 42.20-7.

The freeboards for a Type “B” vessel which complies with paragraph (c) of this section may be reduced up to the total difference between the freeboard tables referenced in paragraph (d) of this section provided that the vessel meets the flooding standard in § 42.20-8 and the provisions of § 42.15-80 (a), (b) and (d) as if it were a Type “A” vessel.

Design calculations must be submitted that demonstrate that the vessel will remain afloat in the conditions of equilibrium specified in § 42.20-12 assuming the damage specified in § 42.20-11 as applied to the following flooding standards:

When doing the calculations required in paragraph (a) of this section, the following permeabilities must be assumed:

Design calculations must be submitted that demonstrate that the vessel will remain afloat in the conditions of equilibrium specified in § 42.20-12 assuming the damage specified in § 42.20-11 as applied to the following flooding standards:

When doing the calculations required in paragraph (a) of this section, the following permeabilities must be assumed:

Design calculations must be submitted that demonstrate that the vessel will remain afloat in the conditions of equilibrium specified in § 42.20-12 assuming the damage specified in § 42.20-11 as applied to the following flooding standards:

When doing the calculations required in paragraph (a) of this section, the following permeabilities must be assumed:

For each type of consumable liquid, the maximum free surface of at least one transverse pair of tanks or a single centerline tank must be included. The tank or combination of tanks must be that resulting in the greatest free surface effect.

For cargo liquids, unless the compartment is assumed to be empty as required by § 42.20-9(b)(3), the free surface of those compartments containing liquids is calculated at an angle of heel of not more than 5 degrees.

The vertical extent of damage in all cases must be assumed to be from the baseline upward without limit.

The transverse extent of damage is assumed to be equal to B/5 or 11.5 meters (37.7 feet), whichever is less. The transverse extent is measured inboard from the side of the ship perpendicularly to the center line at the level of the summer load waterline.

If damage of a lesser extent than that specified in paragraph (a) or (b) of this section results in a more severe condition, the lesser extent must be assumed.

The following assumptions apply to the transverse damage specified in paragraph (b) of this section for a stepped or recessed bulkhead:

If a wing tank has openings into adjacent compartments, the wing tank and adjacent compartments must be considered as one compartment. This provision applies even where these openings are fitted with closing appliances except:

Only transverse watertight bulkheads that are spaced apart at least 1/3(L) 2/3 or 14.5 meters (0.495(L) 2/3 or 47.6 feet), whichever is less, may be considered effective. If transverse bulkheads are closer together, then one or more of these bulkheads must be assumed to be non-existent in order to achieve the minimum spacing between bulkheads.

Downflooding. The final waterline after flooding, taking into account sinkage, heel, and trim, is below the lower edge of any opening through which progressive flooding can take place. Such openings include air pipes, ventilators, and openings which are closed by means of weathertight doors (even if they comply with § 42.15-10) or covers (even if they comply with § 42.15-30 or § 42.15-45(d)) but may exclude those openings closed by means of:

Progressive flooding. If pipes, ducts, or tunnels are situated within the assumed extent of damage penetration as defined in § 42.20-11 (a) and (b), progressive flooding cannot extend to compartments other than those assumed to be floodable in the calculation for each case of damage.

Final angle of heel. The angle of heel due to unsymmetrical flooding does not exceed 15 degrees. If no part of the deck is immersed, an angle of heel of up to 17 degrees may be accepted.

Metacentric height. The metacentric height of the damaged vessel, in the upright condition, is positive.

Residual stability. Through an angle of 20 degrees beyond its position of equilibrium, the vessel must meet the following conditions:

Intermediate stages of flooding. The Commandant is satisfied that the stability is sufficient during intermediate stages of flooding.

A lighter, barge, or other vessel without independent means of propulsion is assigned a freeboard in accordance with the provisions of this subpart as modified by paragraphs (b), (c), and (d) of this section.

A barge that meets the requirements of § 42.09-5(b) may be assigned Type “A” freeboard if the barge does not carry deck cargo.

An unmanned barge is not required to comply with § 42.15-75, § 42.15-80(b), or § 42.20-70.

An unmanned barge that has only small access openings closed by watertight gasketed covers of steel or equivalent material on the freeboard deck, may be assigned a freeboard 25 percent less than that calculated in accordance with this subpart.