I. Classic Moths shall conform to the Equipment Rules of Sailing (ERS) as published by the International Sailing Federation (ISAF), except as modified by these rules. Definitions and figures from the ERS shall be used to interpret these rules as applicable.
II. Basic Definition: A Classic Moth is a monohull boat with one sail, mast, boom, rudder, and either one centerboard or one daggerboard, as further defined by these rules.
III. Hull:
A. Hull length shall not exceed 11 feet.
B. Hull beam shall not exceed 60 inches overall.
C. Hull weight shall be a minimum of 75 pounds.
D. Structural parts shall not be unreasonably increased in any area with the sole intent of improving the weight distribution of the hull.
E. No ballast is permitted.
F. No hollows or concavities that exceed 1 inch in depth shall exist below the sheerline and aft of the leading edge of the centerboard or daggerboard.
G. Hiking boards, trapezes, trampolines, outriggers, or other devices to assist in hiking with the exception of foot straps are not permitted.
H. The hull shall have sufficient flotation to allow bailing it out, if swamped.
IV. Spars:
A. Limit Marks:
The Limit Marks shall have a minimum width of ¾ inch.
B. Mast:
1) The distance from the lower point to the upper point shall not exceed 15 feet.
2) The mast section shall not exceed 3 and ½ inches in any direction.
C. Boom:
1) The outer point distance shall not exceed 9 feet.
2) The boom section shall not exceed 3 inches in any direction.
V. Sail:
A. The sail shall be of single woven ply with the exception of sail reinforcements, batten pockets, windows, stiffening, tablings attachments and identification marks.
B. The window area shall not exceed 400 square inches.
C. The leech length shall not exceed 17 feet 5 and 29/32 inches.
D. The half width shall not exceed 66 inches.
E. The top width shall not exceed 1 and 5/8 inches.
F. Battens:
1) No more than 4.
2) The combined length of all battens shall not exceed 92 inches.
3) No batten shall be placed closer to a spar than 6 inches.
G. The leech shall be shaped such that the aft head point, outer ends of each batten pocket, and clew lie on the arc of a circumscribed circle. No part of the sail shall lie outside this arc.
H. All sails will display the Moth Emblem consisting of a 12 inch outside diameter blue circle with inscribed red M. Circle and M width shall be 1 and ½ inches.
I. All sails will display numbers as approved by the CMBA or local authority. Boat registration numbers of the IMCA will be honored, if known.
J. The sail foot shall be restrained by attachment(s) so that it remains within 3 inches of the top of the boom. Loose-footed sails are specifically prohibited.