Firefly 850 One-design

The Firefly 850 One Design is a stylish, fast, exciting coastal racing or weekend cruising cata¬maran. The hulls are wide enough to provide a cozy double berth while weight and construction costs are kept to a minimum. The boat has the added advantage of being demountable so it can be trailed to races or cruising areas.

In 2005, I worked with Latitude 8 Yachts in Phuket, Thailand to start producing the Firefly 850 cats. Supervising in the build of the first two boats, Voodoo Child and Moto Inzi, I made some minor adjustments to the plans as well as upgrading and streamlining the build process.

In November 2008, the 9th Firefly 850 Sports, BlueNoze was launched by Latitude 8 Yachts while the 10th boat is presently under construction. The fleet of Fireflys has enjoyed One Design class racing in the region’s many regattas with 8 Fireflys competing in the last 2 Phuket King’s Cup Regatta.

The Firefly 850 is built using the strip plank sandwich construction method utilizing a Western Red Cedar core and Unidirectional Fiberglass laid at 90 degrees across the planks. Extra layers of fibreglass cloth are utilized for added reinforcement at strategic areas around the beams and below the waterline. Alternatively hulls and decks could be built in foam sandwich construction. Bulkheads, bunks aft decks and swim steps are all foam sandwich.

Although the Firefly 850 is designed primarily as a “camping” boat that most time onboard including sleeping will be preferred on deck, there are large berths in the ends of each hull. Located in the central part of the hulls are a seat on the outer side and a shelf and locker unit for stowage on the inner side. A small galley can consist of a single burner butane stove and small sink. Each hull has a hatch forward for ventilation as well as an opening portlight in the “galley”. There is also an opening portlight in the aft bunk under the trampoline so that it can be left open for ventilation in inclement weather.

On deck the layout is simple and easy for the crew to sail the boat efficiently. Mainsheet and traveler are both within arms reach of the helmsman so they can be released easily. Rudders have a break in the shaft just above the swim step which this setup allows. Although not kick-up the rudders can be easily removed for beaching. The resulting balanced spade rudder is far more efficient than the transom hung variety.

To windward the speed and height of the Firefly 850 One Design is quite outstanding, usually pointing noticeably higher than most of the rest of the fleet. In ideal conditions, 11 knots plus of boat speed and tacking through 80 degrees can be expected. In the 2009 Phuket Race Week, the winning Firefly Voodoo was able match Henry Kayes all carbon and 2 foot longer Sea Cart on the beats in 15-18 knots of wind. Tacking is positive with backing of the jib not required. When the spinnaker is set is when the boat really takes off. Reeching and running speeds of 20 knots plus can be maintained.

On all points of sail the Firefly 850 is a pleasure to sail. Often the helm can be let go of, with the boat continuing to track in a straight line. Another pleasing attribute is the bows up attitude that the boat sails at even when pushed hard under spinnaker. This is an important safety feature and one that is usually lacking on similar catamarans.

Recommended auxiliary power is a 6hp 4 stroke outboard long shaft on a lifting bracket.

Firefly 850 One Design Class

The Firefly 850 One Design Class has been established in Thailand since 2006, with 8 boats competing in the 2007 and 2008 Phuket Kings Cup.  The fleet also competes in the other regattas in the region with the Firefly of the Year award presented for the last 3 years at the completion of the Phuket Race Week regatta.


Although built by Latitude 8 Yachts in Phuket, plans are also available for builders outside the South East Asia region. Plans for the Firefly 850 Sports are extremely comprehensive and include:

  • Construction Plans Book of detailed drawings and instructions
  • Fabricated Fittings Book of drawings for fabricated fittings
  • Full Size Patterns for Hull and Deck Sections and for Rudder and Daggerboard Sections
  • Also Full Size Patterns for Bunks, Bulkheads and all flat panels.
  • Detailed and Accurate Materials Lists for WRC Strip Plank or Foam Sandwich Construction
  • Equipment Lists
  • Harken Fittings List
  • Disc of photos of the build process and fittings


LOA8.53 m (28′ 0″)          Draft 
LWL8.40 m (27′ 7″) Hull0.26 m (10″)
BOA5.73 m (18′ 10″) Rudders0.65 m (2′ 2″)
BCL4.70 m (15′ 5″)   
Hull BWL616 mm (2′ 0″) Working Sail Area 
Hull LWL : Hull BWL  13.6 : 1 Main and Jib46.8 m2 (503 ft2)
Displacement  Mast Height above deck  12.9 m (42′ 4″)
DWL1360 kg (2299 lb)   
Racing (Class Rule)1010 kg (2228 lb)   
Cruising1680 kg (3705 lb)   

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