To what extent are hollows permitted in the profile of a Marblehead hull?

The relevant rule is D.2.3 (b) (2).

D.2.3   CONSTRUCTION

(b)         Except for the trunking for hull appendages, the hull shall not have:

(2)         hollows in the plan view and/or the profile under the datum waterplane that exceed 3 mm,

The drawing shows a hollow in the profile under the datum waterplane. There is a difference between the true waterline (waterplane) and the datum waterplane referred to in the class rules. The class rules use a length restriction gauge of a specified design to determine the datum waterplane.

The drawing shows a hull with a hollow in the profile at the stern. It also shows the length restriction gauge and the datum waterplane. The hollow found when a straight edge is placed to touch the hull at A and D is greater than 3 mm. However D.2.3 (b) (2) applies to hollows under the datum waterplane. When a straight edge is placed touching the hull at B and C, the hollow is less than or equal to 3 mm. The hull, therefore, complies with D.2.3 (b) (2).