The American Marblehead Class


Biff Martin’s classic American M from a British design

 

Class Secretary
Ben Martin
10 Greystone Road
Marblehead, MA 01945-2829
978 828-9765

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Description

The “Marblehead Class” 50/800 started in the early 1930s, invented by members of the Marblehead Model Yacht Club. It soon became the largest class of pond model raced in the world. In the more than 80 year history of the M Class thousands of these wonderful models have been built. The Marblehead Class 50/800 is an American class; hence the “American M Class”, again our effort, born in Marblehead, to revitalize the oldest continually sailed racing model in the US. Every “M” ever built is welcome to participate in “American Marblehead Class” events as long as they meet the class rules published in the AMYA website. The idea of “American M” is to bring all eras of these beautiful boats to the water at the same time.

AMYA Class Rules

American Marblehead class 50/800 models of pre-1970 design will adhere to the following measurement rules:

The Rules of Pre-1970 Boats

1. Hull measurement

Length of hull will be 50 inches ± ¼ of an inch.

2. Sail Area

Sail area not to exceed 800 square inches, triangular measurement. The roaches of the sails and foot round are not to be counted in the sail measurement.

3. Prohibited

  • Sliding or adjustable keels.
  • Centerboards; but not to prohibit removable keels.
  • Leeboards.
  • Bilge boards.
  • Bowsprits.
  • Overhanging rudders.
  • Moveable ballast. (2016)
  • Prognathous keels (No portion of the lead ballast can project forward of any part of the leading edge the keel.) (2016)
  • Metal fin keels.
  • Ballast material of greater density than lead.
  • Multi hulls.

4. Garboards

Hollow of the garboards to be not less than 1 inch radius. (May be checked with a washer of 2 inches in diameter.)

5. Ballast

Ballast not to be changed or moved during a race event.

6. Draft

Maximum depth of the keel from the bottom of the hull to the bottom of the ballast shall be 20.0 inches (2016)

7. Hull weight

A. Minimum hull weight to be 2.5 pounds. (Without rig, ballast, or fin.) Winch, servos, rudder, and batteries are to be in place.(2016)

B. Hull shape: No restrictions on L.W.L., beam, freeboard or tumblehome.

C. Models may carry a bow bumper of a resilient material restricted to ½ inch thickness.

8. Rig

A. Rig not restricted.

B. Height of jib stay attachment to the mast not to be higher than 80 percent of the measurement on the mast from the deck to the bottom of the headboard.

9. Mast and Spars

A. Height of the mast not limited.

B. Mast and booms will be no greater than ¾ of an inch in diameter or if flat-sided no greater than ¾ of an inch on a side.

C. Area of the mast or booms not counted in the sail area.

10. Sails

A. Sails may be single or multi-panel.

B. (Deleted 2016.)

C. Roach of the mainsail not to exceed 2 inches, roach of jib not to exceed one inch.

D. Foot round of the main or jib not to exceed 1 inch.

E. Mainsail battens not to exceed 4 in number nor be longer than 4 inches.

F. Jib battens not to exceed 3 in number nor be longer than 2 inches.

G. Headboards not to exceed ¾ of an inch measure to the bottom.

H. Spinnakers are permitted but are not to be flown from higher than the jib stay at 80 percent measurement.

I. Spinnaker poles no longer than 15 inches.

 

Post-1970 “M” American Marblehead models will follow the early AMYA class rating rules with the exception of weight and depth as defined below (2016)

The Rules of Post-1970 Boats

1. Hull

A. Hull length to be 50 inches, ± ¼ of an inch.

B. 1/2 inch resilient material bow bumper attached to the bow of model above the waterline.

C. Minimum weight of the hull shall be 2.5 pounds with the winch, servos, rudder, and batteries installed. The rig, keel fin, and ballast are not included in this weight. (2016)

D. Maximum depth of the keel from the bottom of the hull to the bottom of the ballast shall be 20.0 inches.

2. Prohibited

  • Moveable keels.
  • Centerboards.
  • Leeboards.
  • Bilge boards.
  • Bowsprits.
  • Overhanging rudders.
  • Outriggers.
  • Multi-hulls.
  • Moveable ballast.

3. No limits on L.W.L, beam, freeboard or tumblehome.

4. Spars

The maximum dimension of spars if round, is to be ¾ of an inch in diameter. If spars are to be straight-sided, ¾ of an inch on a side.

5. Sails

A. Maximum sail area is to be 800 square inches.

B. Measurement of the mainsail is to be to the AMYA formula measured from the tack to the bottom of the headboard.

C. The jib is the same as the main except measured to the eye instead of the head of the sail when a headboard is not used.

D. The base of the headboards is not to exceed ¾ of an inch.

E. The roach of the sails

Main not to exceed 2 inches and may have 4 battens 4 inches long.

Jib roach not to exceed 1 inch and may have 3 batten 2 inches long.

F. Maximum height of the main sail is 85 inches from the deck to the bottom of the headboard or to the eye of the halyard if no headboard is used.

G. Height of the jib stay attachment to the mast shall not be higher than 80 percent of the height measurement from the deck to the bottom of the headboard.

I. Spinnakers are allowed

Spinnakers are not to be attached higher than jib stay 80 percent mark.

Spinnaker pole not to be longer than 15 inches.

6. The International rule boats can be registered in the class as long as they meet the post 1970 rules above with the weight and draft rules stated. (2016)