The Open 6.5m is a box rule which allows for the development of some of the most radical design ideas. This affordability and the reasonably relaxed design rules have led to the class becoming a hotbed of development and innovation. Canting keels, trim tabs, water ballast and articulating bowsprits are just some of the concepts tried in the Mini Class. Concepts that work can often be applied to larger boats.

The Design Rules

• Maximum Length – 6.50 metres This does not include rudders and their fittings, the fittings of the bow sprit bob stay, the push pits, the pulpit, solar panels and wind vane pilot.
• Maximum Beam – 3 metres including moving keels, masts and rigging.
• Maximum Draft – 2 metres, regardless of the angle of heel and the position of appendices or mobile appendices.
• Bottom of keel to top of the highest sail – 14 metres
• Bulb – the height and width must not exceed 450mm
• Water Ballast – must be fixed inside the hull and is part of the structure of the boat. The total volume of water ballast must not exceed 400 litres symmetrically displaced along the longitudinal axis of the boat.
• Sails – 8 maximum This includes a storm jib and trysail as compulsory. A wingmast, of more than 2m2 in projected area, counts as one sail. Double film sails count as two sails.
  Sail materials:
  Mainsail - woven polyester, with windows of 0.2m2 max.
  Headsail - woven polyester and polyester film (3DL are permitted but only in polyester).
  Spinnaker - nylon

Series and Protos

The class is split into two groups, prototypes and series (or production) boats, high-tech vs low cost.

Prototypes

Prototype boats are the foreground for designers to play with. These boats and their designs are built specifically for the race and with only one thing in mind, to go fast.

New prototype boats now are often made entirely out of carbon fibre to be both lightweight and strong and incorporate many of the above design ideas all intended to make the boat faster.

The one main disadvantage of prototype boats is their cost. Due to the modern technologies employed in their construction they are very expensive, with a new prototype boat costing sometimes as much as double that of a production boat.

Series or Production Boats

These boats fit the same box design rules as prototype boats however, they have a few more stringent rules such as less exotic building materials allowed and a smaller mast required. There are different designs of production boats however; for a certain design to become a production class it must have at least 10 of them built in the same yard. This means costs are cut down as the yard can employ more mass production methods.

The advantage of production boats is obviously the cost as they are far less extreme than prototype boats and the yards are not building one off designs at extra cost. However, the biggest disadvantage and the most important in some peoples eyes is that they are slower than prototype boats and as such extremely difficult to win races in.