Section 45.51 - Types of ships(a) For the purpose of this subpart, a type A vessel has-(1) No cargo ports or similar sideshell openings below the freeboard deck;(2) Only small freeboard deck openings fitted with watertight gasketed hatch covers of steel;(3) No dimension of a freeboard deck cargo opening greater than 6 feet and the total area not exceeding 18 ft2 ; and(4) No more than two freeboard deck cargo openings to a single cargo space.(b) For the purposes of this subpart a type B vessel is a vessel that does not meet the requirements in paragraph (a) of this section.