1. 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. 
  2. 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. 
  3. Hull:
    1. Hull length shall not exceed 11 feet exclusive of protuberances such as fittings or deck joining flanges.
    2. Hull beam shall not exceed 60 inches overall.
    3. Hull weight shall be a minimum of 75 pounds.
    4. Structural parts shall not be unreasonably increased in any area with the sole intent of improving the weight distribution of the hull.
    5. No ballast is permitted.
    6. 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.
    7. Hiking boards, trapezes, trampolines, outriggers, or other devices to assist in hiking with the exception of foot straps are not permitted.
    8. The hull shall have sufficient flotation to allow bailing it out, if swamped.
    9. Hydrofoils are not permitted.
  4. Spars:
    1. Limit Marks: The Limit Marks shall have a minimum width of ¾ inch.
    2. 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.
      3. The distance from the upper point to the top of the mast shall not exceed 6 inches.
    3. Boom:
      1. The outer point distance shall not exceed 9 feet.
      2. The boom section shall not exceed 3 inches in any direction.
  5. Sail (Definitions and Diagrams of the ISAF ERS apply):
    1. Sail material is not limited.
    2. The leech length shall not exceed 17 feet 5 and 29/32 inches.
    3. The half width shall not exceed 66 inches.
    4. The three quarters width shall not exceed 36 inches.
    5. The Aft Head Point shall be within 1 and 5/8 inches of the Luff or Luff Extension.
    6. 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.
    7. All sails will display numbers as approved by the CMBA or local authority. Boat registration numbers of the IMCA will be honored, if known.
    8. If the sail is loose footed, the foot round shall not exceed 3 inches. If the sail is attached to the the boom along the foot, the attachment(s) shall ensure that no part of the foot shall drape more than 3 inches below the attachment(s).