Technical Regulations for the InterClub Dinghy
Revised: April 20, 1997
1. The Technical Committee
The technical committee shall consist of one member per fleet. The fleet may change their nominee at any time. Any fleet may appoint a member to the technical committee, but only those fleets with five or more active boats shall have voting privileges. Fleets with voting privileges must also pay annual dues to defray operational expenses of the technical committee such as telephone, printing, postage, and measurement equipment. The committee shall elect a chairman from its members. The committee may elect a new chairman at any time. The chairman shall prepare a budget annually and submit it to the committee for approval by September 30 of each year. The committee shall approve or modify the budget and adjust the dues accordingly by October 31 of each year.
A majority vote of the dues paying fleet representatives is required for all changes to the rules. Proposed changes to the rules must be submitted to the committee chairman in writing one month before a vote can be taken and all fleet representatives must be advised of proposed changes two weeks before a vote. The technical committee may meet from time to time as needed and may conduct its business by mail, phone, or FAX; except that the technical committee shall meet during or within one week after the National Championships each year.
The technical committee shall be empowered to approve or disapprove of devices or additions to equipment or hulls which are not covered in these rules. Any changes to the hull or equipment shall be referred to the technical committee for its prior approval. Furthermore, anything not specifically specified in these rules may be considered illegal.
Racing shall be strictly one design in intent and the following rules shall be enforced to achieve this objective.
Each fleet member is encouraged to ask his or her representative for help in understanding these rules.
2. Hull Specifications
The external shape of a new hull shall conform to the specifications of the Sparkmen & Stephens design for the Interclub Dinghy within 1/4 inches tolerance. The official templates for the S&S blueprints shall serve as a guide with sufficient tolerances to allow for reasonable variations in existing boats as approved by the National governing body.
2.1 Construction materials
Hulls built after 4/1/90 may be constructed of E-glass and coremat only and hull thickness shall be limited to 5/16″. Hulls built before 4/1/90 may be constructed of wood and do not have a skin thickness or coring limitation.
Coring material: Any closed cell PVC high density foam (i.e. Airex, Divinicell, Klegecell) may be used.
Primary laminates of hull, deck, and tanks shall use polyester resin only. Epoxy resin may be used for bonding and joining purposes only.
Lead is not a building material.
2.2. Permissible reinforcements which deviate from the S&S specifications
2.2.1. Gunwale
The gunwale of a fiberglass boat may be stiffened by the addition of glass reinforced plastics (GRP) or wood. If knee braces are to be added they shall not exceed 6 inches in any dimension and shall be confined to 3 per side. Alternatively the gunwale may be stiffened by boxing in the section with a rigid, closed cell foam core and GRP whose dimensions shall not exceed 3 inches vertically or horizontally.
2.2.2. Thwart
The thwart may be stiffened by the addition of glass reinforced plastics (GRP), wood and/or by boxing in the section with a rigid, closed cell foam core and GRP. The overall width of this box shall not exceed 2 inches.
2.2.3. Bulkhead under thwart
A single bulkhead of wood or fiberglass (with or without a rigid core) joined to the centerboard trunk, the bottom of the thwart, and the inside of the hull is permissible. It shall not exceed ? inch in thickness and shall be fitted perpendicular to the boats centerline.
2.2.4. Mast Partner Reinforcement
A single gusset joining the hull to the mast partner is permissible. It shall not exceed 3/4 inch in thickness and shall have a maximum single dimension of 14 inches.
2.3 Hull Weight
2.3.1. Fully Rigged
Boats fully equipped for racing (i.e. with centerboard, rudder, boom, mast, lines and all fixed fittings) shall weigh at least 250 lb. This weight is meant to exclude sail, paddle, anchor, tools and any other personal effects.
2.3.2. The bow tip weight, which shall be measured on an approved jig, shall weigh at least 115 lb. The measurement shall be taken with the mast stepped in normal fore and aft trim and all other equipment included in the fully rigged weight in its normal position, including all permanently secured corrector weights. The rudder and tiller shall be excluded.
2.4 Centerboard Trunk
2.4.1. Slot Length and Width
The centerboard slot shall be between 44 inches and 48 inches. The slot shall be at least 7/8 inch wide when measured at a depth of 1 inch over the distance of 44 inches. (i.e. a 7/8″ x 1″ x 44″ template must fit within the centerboard slot).
2.4.2. Slot Location
The centerboard slot is to begin between 33″ and 34.25″ from the aft point which is the intersection of the transom with the underside of the hull, amidships, hereafter called point T2.
Centerboard maximum forward angle is not limited..
2.4.3. Pin hole location
The centerboard pin hole shall be between 75″ and 77″ from point T2.
2.4.4. Shimming
Centerboard slot may be shimmed in compliance with centerboard slot dimensions and location. No gear which will permit or facilitate the movement of the centerboard in the athwart ship direction will be allowed.
2.5 Mast Partner.
2.5.1. Mast Partner Location
The distance from that point which is the top, aft surface of the transom, amidships, herein called point T1, and the aft end of the partner hole shall be between 8′ 10″ and 9′ 0″. The partner hole itself shall not exceed 4″ in length. It is to be noted that point T1 is defined as the aft surface of the transom, or where that would be in the absence of any rubrail or contraction flange which might protrude beyond this point.
The mast partner shall be shimmed to within 1/4″ in the athwart ships directions.
2.5.2 Mast Blocks
Mast blocks must be constructed of wood or plastic. They may be placed in front of or behind the mast in the mast partner hole. No other mechanism may be used to prebend or straighten the mast in the fore and aft direction at the mast partner.
Mast blocks shall NOT be adjusted while racing.
2.6 Fittings
2.6.1 Chainplates
The distance from the aft end of the partner hole to a taut string running through the bearing points of the shrouds at the chainplates shall be a minimum of 1.5″. It should be noted that if a particular fleet amends this rule to allow two sets of chainplates, the forward most set must be used for any inter-fleet competition.
2.6.2 Traveler
The traveler may be fitted as desired except that it shall not be located more than 6″ forward of the exterior face of the transom and shall not project outboard of the gunwale.
2.6.3 Mast Step
The mast must be secured in the step to prevent forward and aft movement in excess of 1/8″. The mast may not be moved in the step once on the water.
2.6.4 Boom Vang
The boom vang may be rigged as desired but may not lift the boom in any way.
2.6.5 Forestay Adjustment
Any adjustment system for the forestay must be secured on or forward of the mast partner.
2.6.6 Other
Cunningham, outhaul, hiking straps, etc. may be fitted as desired unless otherwise limited by other sections of these rules.
2.7 Rub Rails
Functioning rub rails must be installed. They may be made of rubber, wood, or any flexible plastic.
2.8 Buoyancy
All glass boats shall have air tight tanks.
Additional buoyancy is permissible. All boats must have plugs in the tanks and must be water tight. All access port mounting rungs and connections must be bedded in sealant. Cover shall be bolt-on, threaded screw-in , or shall be permanently sealed shut with flexible sealant. Threaded drain plugs are strongly recommended. Corks are not acceptable.
All boats must have positive buoyancy with both crew in or on the boat when the boat is awash or swamped.
2.9 Floorboards
Fiberglass boats may add floorboards. Wooden boats shall have floorboards.
3. Centerboard Specifications
3.1 Construction
Centerboards may be of wood or fiberglass with rigid, closed cell foam core. S-Glass may be used in the construction of foils only.
3.2 Dimensions
They may be shaped as desired but shall conform to the enclosed diagram of the profile within a tolerance of +0.0″ and -0.5″. Maximum thickness for any portion of the centerboard which extends below the trunk shall not exceed 7/8″. The portion of the centerboard remaining in the trunk may be thicker to insure tightness within the trunk.
3.3 Jibing Centerboards
Jibing centerboards are illegal.
4. Rudder Specifications
4.1 Construction
Rudders may be constructed of wood or fiberglass with rigid, closed cell foam core. S-glass may be used in the construction of foils only.
4.2 Dimensions
Rudders may be shaped as desired but shall conform to the enclosed diagram of the profile within a tolerance of +0.0″ and -0.5″. The maximum thickness of the rudder below the waterline shall not exceed 7/8″. The portion of the rudder above the top of the transom is unrestricted.
4.3 Location
The distance from the transom to the rudder shall not exceed 1.75″ and shall be constant within 0.5″.
Measurement guideline: Measure the distance of the rudder at the top of the transom and at the bottom. The maximum distance must be no greater than 1.75″ The maximum difference in the measurement must be no greater than 0.5″
4.4 Fittings
Rudder head fittings, tiller, and tiller extension may be rigged out as desired.
4.5 Rudder Depth
The distance measured from the bottom of the transom on centerline to the lowest/aftmost point of the rudder shall be between 27″ and 29″. (Only to be used in the 90/91 season for reference)
5. Mast
5.1 Allowable Sections
The mast shall be made from a Kenyon B section or from a Zephyr #1 section. Mast wall thickness must be constant within manufactures tolerances and may not be stiffened except to reinforce the area where the mast contacts the partners. Any reinforcement added to the mast at the partner must be exterior to the mast and no more than 3 inches in length.
5.2 Mast Band
The distance between the top of the band on the mast and the top of the partner, excluding any shoulder at the mast opening, shall not exceed 21″.
5.3 Mast Height
The distance from the center of the halyard sheave to the top of the band on the mast (which shall be at least 0.75″ wide and be of a contrasting color) shall not be greater than 16′ 0″. The tack of the mainsail shall not extend below the top of the band.
5.4 Mast Restrictions
Only one mast may be used at the national regatta. In case of failure, another section may be substituted provided it is the same section as the original mast.
5.5 Main Halyard
5.5.1 Sheave
The halyard sheave shall not be larger than 1.75″ in diameter.
5.5.2 External
The main halyard shall be external.
5.5.3 Halyard Lock
Halyard locks are permissible and must be located above the deck. If the halyard lock is located at the top of the mast it must be at least 4″ below the center of the sheave.
5.6 Forestay and Shrouds
5.6.1 Tangs
Shroud tangs shall be external.
5.6.2 Shroud Location
The distance from the center of the halyard sheave to the intersection of the shroud tang and outside wall of the mast shall be between 53″ and 60″.
5.6.3 Adjustments
The forestay and the shrouds may not be adjusted during a race.
5.6.4 Forestay Location
The forestay is to intersect the mast at a point which is between 34″ and 39″ from the center of the halyard sheave.
6. Boom
6.1 Construction
The boom may be made from a Kenyon B section or from a Zephyr #1 section or made of wood. Booms may be stiffened.
Hollow wooden booms are not permitted.
6.2 Boom Band
The distance from the aft edge of the mast to the forward edge of the band shall not be greater than 8′ 8″. The clew of the sail shall not extend aft of the forward edge of the band. The band must be of contrasting color.
7. Sail Specifications
Sails built and measured before April 20, 1997 are grandfathered with respect to these measurement guidelines. Any modifications or alterations made to a sail (other than a repair) built and measured before April 20, 1997 are not grandfathered, and must conform to these guidelines.
7.1 Racing
Only one sail may be used on a race day.
Only one sail may measured in for use at the Nationals regatta. If the sail is damaged beyond repair, another sail may be measured in for use at the discretion of the race committee.
7.2 Sail Numbers
All sails shall have both sail numbers and class insignia no less than 10″ in height. The numbers shall be located near the leech between the two battens. The insignia shall be located above the numbers midway between luff and leech.
7.3 Cloth Weight
Sail cloth shall not be less than 3 ounce weight, per sailmakers yard. Mylar and Dacron are permissible building materials for sails.
7.4 Head of Sail
The top forward corner of the head shall be located as follows: Place one side of a square along the forward edge of the bolt rope (or the vertical projection of the front of the bolt rope) and slide it down the luff until the other side of the square touches the highest point on the head. The resultant corner of the square is the forward corner of the head.
The top aft corner of the head shall be located as follows: With the square in position for locating the top forward corner of the head, the top aft corner of the head is at the intersection of a straight-line projection of a tangent to the leech above the top batten and the horizontal edge of the square which contacts the highest point on the head.
The top aft corner of the head shall not be located above the top forward corner of the head.
7.5 Head Girth
The head girth shall be no more than 4.125 inches. The head girth is the straight-line distance from the top forward corner of the head to the top aft corner of the head.
7.6 Leech Length
The leech length, as measured from the top forward corner of the head to the intersection of the leech and foot, shall not exceed 17′ 5″.
7.7 Midgirth Measurement
The midgirth shall not exceed 5′ 4.5″ as measured from the midpoint of the luff to midpoint of the leech. The midpoint of the leech is determined by folding the top forward corner of the head so it meets the foot and the top aft corner of the head so it meets the leech. The midpoint of the luff is determined by folding the top forward corner of the head to the apex of the foot and luff at the tack.. Any hollow in the leech between the battens shall be bridged by a straight line and the midgirth measured to that line.
7.8 Battens Restrictions
There shall be two battens. The length of a batten shall not be greater than 19 inches. The centerline of the batten pocket is a line drawn along its length and central to its width. The batten pocket width shall not be greater than 2 inches. The batten pockets shall be located to divide the leech into three equal parts. This measurement is taken by first folding the head such that the forward corner meets the centerline of the bottom batten pocket and the aft corner meets the leech. The centerline of the top batten pocket at the leech shall be within ± 1 inch of the crease. The head of sail is then folded in the same manner as in measuring the midpoint of the leech. With the sail folded in this manner, the centerline of each batten pocket at the leech must lie on top of each other within 1 inch.
7.9 Roach Restrictions
With the sail folded in the same manner as the midgirth measurement, the after ends of the batten pockets shall be within 2 inches of each other.
7.10 Foot Roach
The top forward corner of the head to mid-foot shall not exceed 16′ 10″. The mid-foot is half the distance between the straight line intersection points at the tack and clew at the foot of the sail.
7.11 Clew Boards
Clew boards are not allowed, nor are any other artificial stiffeners.
7.12 Windows
Windows of transparent material are permitted.
8. Crew Limitations and Ballast
The boat shall be sailed by two (2) people whose combined weight shall be at least 315 lb. Should live crew weight fail to make this minimum, non-movable ballast may be carried to make up the difference. A maximum of 15 lb. of negative buoyancy ballast may be carried. Any additional weight must be neutral or positive buoyancy. Crews shall be weighed dressed for racing, this includes wearing life jackets. Weight jackets are not permitted.
9. Life Jackets
USCG approved personal floatation devices shall be worn by both crew.
10. Propulsion
10.1 RRS 42.2(d) is changed to “sculling repeated movements of the helm to propel the boat forward”
10.2 RRS 42.3(b) is relaced by “During and immediately after tacking and gybing a boat’s crew may move their bodies to roll the boat provided the the boat’s mast does not move aggressively away from verical more than once”
Interclub Dinghy Class 