Untitled

INTERNATIONAL THUNDERBIRD CLASS ASSOCIATION

SPECIFICATIONS

9.0 Sails
- 9.1 Sail Materials
- 9.2 Sail Windows
- 9.3 Insignia and Numbers
- 9.4 Sail Measurement Techniques
- 9.5 Mainsail
- 9.6 Genoa
- 9.7 Working Jib
- 9.8 Spinnaker
10.0 Weight Requirements
- 10.1 Bare Boat Weight
- 10.2 Racing Weight
- 11.0 Instumentation
  - 11.1 Allowable Instrumentation

Tips For Builders

9.0 SAILS
- 9.1 Sail Materials
  - 9.1.1 No material other than woven dacron shall be used in the mainsail and headsails, except that the genoa may, alternatively, be made of dacron (polyester) substrate/mylar (polyester film) laminate. No material other than woven nylon shall be used in spinnakers.
  - 9.1.2 A certificate from the sailmaker stating the type and weight of the material used in each sail shall be available to the measurer for the initial measurement of a new sail. A sail maker's invoice shall be considered satisfactory.
- 9.2 Sail Windows
  Transparent windows the total area of which do not exceed 6 square feet (0.5574 sq. m.) may be fitted in each sail. Revised
- 9.3 Insignia and Numbers
  - 9.3.1 The official Thunderbird class insignia, as set forth herein, will be fixed to both sides of the mainsail and to both sides of the spinnaker if obliged to do by the National Authority of the country in which the yacht is normally sailed.
    This official insignia will be fixed "back to back" on the mainsail approximately 9'-5" (2.87 m.) from the head. Color shall be black unless designating a champion (see Section 9.3.3).
9.3.2 Each yacht shall carry the official registration number assigned by the Association, fixed to the mainsail and to both sides of the spinnaker if obliged to do so by the National Authority of the country in which the yacht is normally sailed.
Numbers shall always be black and shall be sized and affixed to the mainsail according to current International Yacht Racing Rules.
9.3.3 Champions may use the following colored sail insignia: (Numbers shall be black)
- a. International - Gold
- b. National - Orange
- c. Regional - Blue
- d. fleet - Red
These distinctive colors are the sole property of the skipper and shall remain with him if he should buy or build another yacht in which case the insignia on the original yacht shalt be changed to reflect the status of the new owner.

9.4.1 Main genoa and jib
Dimensions shall be taken with the sails laid on the floor with only such tension applied to them to remove wrinkles. The corner of each sail shall be located by the intersections of the adjacent edges of the sail (extended if necessary) except for the mainsail head. At this location the corner shall be the forward upper corner of the headboard.
9.4.2 Spinnakers
Dimensions shall be taken with the sail stretched between two people with no more than 5 pounds tension and no intermediate support for the sail between measurement points. Measuring tape shall assume same curve as the sail.

9.4.3 Any genoa or jib that has been previously measured and approved in accordance with the Black Book, but subsequently does not conform to one or more of the allowable minimum dimensions, shall be considered legal provided that;

a. No dimension of the sail exceeds the allowable maximum and the sail conforms in every other way to the requirements of the Black Book; and
b. The sail has not been altered in any way since measurement and approval, except for localized repair of damage.

9.5 Mainsail

9.5.1 Minimum fabric weight: 4 oz. /28" x 36" (113.4 grams / 7ll.2mm. x 914.4mm.)
9.5.2 The mainsail shall be attached to the mast so that the sail may be lowered and re-hoisted without the necessity of re-engaging the sail with the mast. Insertion of the luff rope in the slot or track is not permitted.
9.5.3 The foot of the mainsail shall be attached to the boom by means of a track or slot and meet criteria listed in Section 7.7. A loose footed sail is not permitted.
9.5.4 Adjustment to the foot of the main such as zippers, foot roach reefing strings and similar devices are permitted.
9.5.5 There shall be four (4) battens evenly spaced along the leech according to plan and shall measure:
Upper - maximum length 33" (838.2 mm.).
Intermediates - maximum length 55" (1397 mm.).
Lower - maximum length 41"(1041.4 mm.).
9.5.6 Mainsail dimensions.
Luff- 31' (9.449 m.) maximum.
Foot - 13' (3.962 m.) maximum.
Leech - 33' 3"(10.135 m.) maximum

Mid-girth shall be found by folding the peak to tack and peak to clew, marking these mid-points and measuring width of sail between them. Maximum shall be 8' (2.438 m.).
Upper-girth shall be found by folding peak to mid-luff and peak to mid-leech, marking these mid-points and measuring between them. Maximum shall be 4' 9" (1.448 m.).
Lower-girth shall be found by folding tack to mid-luff and clew to mid-leech, marking these mid-points and measuring width of sail between them. Maximum shall be 11' (3.353 m.).
The leech shall not deviate more than 3/4" (19 mm.) from straight lines between aftermost corner of headboard and top batten, between adjoining battens and between lower batten and clew.
Headboard shall not exceed 4-11/l6" (119.1 mm.) horizontally.

9.6 Genoa
- 9.6.1 Minimum fabric weight: 3.25 oz/28" x 36" (92.13 grams/711.2 mm. x 914.4 mm.); Except the minimum fabric weight for a dacron (polyester) substrate/mylar (polyester film) laminate genoa shall have an average weight of not less than 4.5 oz/28" x 36" (127.5 grams/711.2 mm. x 914.4 mm.).
- 9.6.2 Means of genoa attachment to the forestay and on luff are optional provided (1) The sail may be lowered and stowed below deck without detaching forestay to remove sail; and (2) The sail is not hoisted in a grooved device.
- 9.6.3 Genoa Luff shall measure 24' 3"(7.391 m.) maximum, 23' 9" (7.239 m.) minimum.
- 9.6.4 Genoa Foot shall measure 14' 0"(4.267 m.) maximum, 13' 6" (4.115 m.) minimum.
- 9.6.5 Genoa leech shall measure 24' 0"(7.315 m.) maximum, 23' 6" (7.163 m.) minimum.
- 9.6.6 Headboard is not allowed.
9.7 Working Jib
- 9.7.1 Minimum fabric weight:4 oz./28" x 36" (113.4 grams/711.2 mm x 914.4 mm)
- 9.7.2 Means of jib attachment to the forestay and on luff are optional provided (1) The sail may be lowered and stowed below deck without detaching forestay to remove sail; and (2) The sail is not hoisted in a grooved device.
- 9.7.3 Battens: Maximum of three (3) battens are permitted. They shall be evenly spaced along the leech according to plan. The upper batten length is not restricted provided the sail complies with 9.7.7. The remaining battens shall measure 28" (711.2 mm) maximum. - Revised
- 9.7.4 Jib luff shall measure 24' 3" (7.391 m.) maximum, 23' 9" (7.239 m.) minimum.
- 9.7.5 Jib LP (luff perpendicular) shall measure- 9' 0" (2.744 m.)maximum, 7'6" (2.286 m.) minimum.
- 9.7.6 Headboards and/or clewboards are not allowed.
- 9.7.7 With the sail corners drawn tight, no portion of the jib leech may extend aft of a straight line between the head and the clew by more than 2 inches.
9.8 Spinnaker
- 9.8.1 The minimum weight fabric shall be 40 grams per square meter.
- 9.8.2 Spinnaker leeches shall measure 8130 mm or 26' 8" maximum.
- 9.8.3 Spinnaker girth shall measure 5220 mm or 17'1" maximum.

10.0 WEIGHT REQUIREMENTS

10.1 Bare Boat Weight
- 10.1.1 The following equipment must be aboard when weighing and when racing:
  - a. Spars, standing and running rigging.
  - b. Floor boards.
  - c. Rigid bunk bottoms or bunk cushions.
  - d. Mechanical toilet complying with local regulations.
  - e. Permanently installed sink complying with local regulations.
  - f. Permanently installed water tank of not less than ten (10) U.S. gallons (37.9 liters) capacity (tank empty).
- 10.1.2 Yachts will be weighed with all other removable equipment off-loaded. Hatches will be left on hoard. Permanently installed electronic gear, stoves, ice chests and drawers may be left in place but will be listed on the measurement form as comprising the minimum weight.
- 10.1.3 Yacht weight shall be not less than 3650 pounds (1659.1 kg.) when equipped as above. If the yacht weighs less than 3650 pounds (1659.1 kg.), compensating ballast shall be attached to the underside of the main deck.
10.2 Racing Weight
- 10.2.1 Class racing weight shall be 4000 pounds (1818.2kg.) minimum with the following required On board when racing:
  - a. Engine, weighing 35 lb. (15.91 kg.) (minimum) as defined in manufacturer's specifications for net weight, stored aft of Bulkhead #5.
  - b. Three U.S. Gallons (11.4 liters) of engine fuel minimum and a suitable fuel tank.
  - c. 30 pounds (13.64 kg.) of ground tackle.
  - d. Safety equipment required must comply with the regional Coast Guard (or equivalent agency) requirements and include at least:
    - 1) Fire extinguisher - 2 lb. (.91 kg.) dry chemical or 41b.(l.81 kg.)C0₂
    - 2) Bilge pump.
    - 3) One buoyant cushion or life preserver for each person aboard.
    - 4) Hand, mouth or power operated whistle or horn capable of producing a blast of at least 2 seconds duration and audible for a distance of at least 1/2 mile (.804 km.).
    - 5) Running lights.
- 10.2.2 The equipment added to the bare yacht weight to arrive at the minimum racing weight is to be normal racing and cruising equipment and not ballast.
  Personal clothing and consumable stores including water and engine fuel in excess of the minimum may not be included in the minimum weight.
  Table of Contents

11.0 INSTRUMENTATION

11.1 Only the following instruments and/or electronic devices shall be installed and capable of operation on the boat during any Thunderbird onedesign race:
- 11.1.1 VHF Marine radios.
- 11.1.2 Devices to decipher radio navigational signals (Loran, GPS, Differential GPS, etc.) that are not coupled to any other device(s) other than a cockpit repeater display.
- 11.1.3 Inclinometers.
- 11.1.4 Depth-measuring devices.
- 11.1.5 Water thermometers.
- 11.1.6 Knotmeters and logs.
- 11.1.7 Devices to measure windspeed relative to the boat (apparent windspeed).
- 11.1.8 Devices to measure angle of wind relative to the boat (apparent wind angle).
- ll.1.9 Devices to display instantaneous data only derived from Items 11.1.6, 11.1.7 and/or 11.1.8 only (i.e. VMG to windward, true windspeed, true wind angle).
- 11.1.10 Compasses which record and display previous boat heading data which may be coupled to any other device except 11.1.8 (wind angle measurement device).
- 11.1.11 Voltmeters, ammeters and the like which monitor the boats electrical system.
- 11.1.12 Engine-related devices which operate only while the engine is running
- 11.1.13 Air thermometers, barometers and the like.
- 11.1.14 Stopwatches, timers and clocks.
- 11.1.15 Entertainment systems