Specifications

Rainbow Dinghy – Basic Specifications & Dimensions

These specifications provide a framework for traditional and modern Rainbow builds, while allowing room for the thoughtful builder to experiment and apply their own ideas.

🛶 Hull

• Overall Length: 3657 mm

• Maximum Beam: 1181 mm (gunwales optional)

• Maximum Depth: 375 mm (excluding breakwater)

• Side Deck Widths: 216–266 mm

• Material: Marine plywood, minimum 3 mm thickness

• Minimum Hull Weight (unrigged): 42 kg

  • Includes splashboards, floorboards, chainplates & basic fittings
    
    

• Hull Tolerance: ±12 mm on all dimensions

• Buoyancy: Fore and aft bulkheads only; no others permitted
  
  

🪶 Rudder

• Blade Length: Max 610 mm below the hull at the stern
  
  

⚓ Centreboard

• Maximum Length: 1321 mm

• Maximum Width: 355 mm

• Maximum Thickness: 25 mm
  
  

🧭 Tiller

• Suggested Length: 508 mm

• Extension (Optional): Suggested 914 mm
  
  

⛵ Mast

• Max Section Size: 127 mm x 63.5 mm (or equivalent area)

• Suggested Section: 76 mm x 63.5 mm

• Max Height Above Deck: 5.6 m

• Construction: Timber, metal, or carbon (solid or hollow)

• Halyard Heights (Suggested):

  • Jib: 3657 mm

  • Spinnaker: 4419 mm
    
    

• Spinnaker Pole Support: Preventer or spreaders recommended

• Sail Track: Must remain straight when not under tension

• Rotating Masts Allowed: Yes
  
  

📏 Boom

• Maximum Length (including gooseneck): 2362 mm

• Maximum Depth: 152 mm

• Suggested Width (for central sheeting): 57 mm round

• Construction: Timber, metal, or carbon (solid or hollow)

• Sail Track: Must remain straight when not under tension
  
  

🌀 Spinnaker Pole

• Maximum Length (including fittings): 3505 mm

• Material: Timber, metal, or carbon (hollow permitted)

• Suggested Diameter: 25 mm round
  
  

🔧 General Rigging

• Trapeze: Optional, one per side

• Venturis & Self-Bailers: Optional

• Mainsail Sheeting: Customisable by builder

• Spreaders: Typically placed 2200 mm above deck

• Hounds Position: 4000 mm from deck

• Gooseneck Height: 540 mm from deck

• Snotter Height: Suggested 840 mm

• Preventer Wire: From snotter to bow/mid-bow fitting
  
  

🎽 Sail Plan

Maximum of 3 sails at one time:

• 1 Mainsail

• 1 Jib

• 1 Spinnaker (can carry multiple onboard, but only one flown at a time)
  
  

Mainsail

• Max Luff: 4800 mm

• Max Foot: 2180 mm

• Max Leach: 5110 mm

• Max Area: 8 sqm
  
  

• Max Girths:

  • Half: 1680 mm

  • Three-Quarter: 1220 mm

  • Seven-Eighths: 740 mm

  • Quarter: 1990 mm
    
    

Jib

• Max Luff: 3825 mm

• Max Foot: 1330 mm

• Max Leach: 3490 mm

• Max Area: 2.5 sqm

• Max Girths:

  • Half: 650 mm

  • Head: 70 mm
    
    

Spinnaker (Currently under trial)

• Max Area: 9 sqm

Sail Materials & Markings

• Material: Woven synthetic (weight optional)

• Plastic Windows: Permitted

• Battens: Number and length optional

• Vents/Zips: Not permitted

• Insignia: Red “R” in a blue circle

  • Circle Diameter: 381 mm

  • "R" Height: 203 mm

• Sail Number: 290 mm high x 50 mm wide

• All sails must be dry when measured
  
  

🧵 Rigging Lines (Suggested)

• Spinnaker Halyard: 10 m x 4 - 5 mm polyester

• Jib Sheets: 5.5 m x 6 mm polyester

• Main Sheet: 5.5 m x 8 -10 mm polyester

• Spinnaker Sheets: 10 m x 4 - 6 mm polyester

• Stays: 1x19 stainless steel wire, 3.5 mm circumference

• Trapeze Wires: 1x19 stainless steel wire, 2.5 mm circumference