Thunderbird 26

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Thunderbird 26
Designer Ben Seaborn
Year 1958
Draft 1.46 m (4 ft 9 in)
Type Monohull
Hull weight 1,656 kg (3,651 lb)
LOA 7.89 m (25.9 ft)
LWL 6.17 m (20.2 ft)
Beam 2.3 m (7 ft 7 in)
Hull appendages
Keel/board type Fixed - 694 kg (1,530 lb)
Mast length 11.54 m (37.9 ft)
Total sail area 28.61 m2 (308.0 sq ft)

The Thunderbird class sailboat was designed in 1958 by Seattle Washington naval architect Ben Seaborn, [1] in response to a request from the Douglas Fir Plywood Association (now APA - The Engineered Wood Association) of Tacoma, Washington for design proposals for a sailboat that would "... be both a racing and cruising boat; provide sleeping accommodations for four crew; be capable of being built by reasonably skilled amateurs; provide auxiliary power by an outboard motor that could be easily removed and stowed; and out-perform other sailboats in its class." More than 35 years of experience and construction of more than 1,250 Thunderbirds around the world have demonstrated that the 25.90-foot (7.89 m) Thunderbird class sailboat is a success on all accounts.


Design and construction

T-Birds can be built of marine plywood, usually fiberglass-covered for minimum maintenance, or with a fiberglass hull and deck. The International Thunderbird Class Association (ITCA) maintains specifications of what dimensions and specifications fit the definition of the Thunderbird class. [2] Many plywood T-Birds have been built by amateur builders, while fiberglass T-Birds usually are built by professional boatbuilders, although plans also are available for "one-off" construction of fiberglass T-Birds by amateur builders.

In North America, professional builders of fiberglass T-Birds are located in Canada (Victoria, British Columbia and Toronto, Ontario). In Australia, where T-Birds also are popular, fiberglass T-Birds are built using hull and deck molds owned by the Australian Thunderbird Class Association. Fiberglass boat parts—such as a complete deck, cabin and cockpit; hatches for the main cabin and forward and aft decks, and a lightweight, foam-filled fiberglass spade rudder—are available from fiberglass boat builders, to modernize or restore older T-Birds.

The 38.32-foot (11.68 m) mast, 13.50-foot (4.11 m) boom and 8-foot (2.44 m) spinnaker pole can be built of wood, but most boatbuilders and owners now choose ready-made aluminum spars from a source that meets ITCA specifications, for low maintenance and high performance. Dacron sailcloth is used for the mainsail, genoa and working jib, and nylon for the spinnaker. An alternate dacron/mylar film sailcloth laminate also is approved for the genoa. Only one size of mainsail, genoa, working jib and spinnaker are authorized by ITCA for racing. In keeping with ITCA policy of maintaining the affordability of the T-Bird, only one set of new sails is permitted in a two-year period.

Genoa (sail) type of large jib or staysail

A genoa sail is a type of large jib or staysail that extends past the mast and so overlaps the main sail when viewed from the side, sometimes eliminating it. It was originally called an "overlapping jib" and later a Genoa jib. It is used on single-masted sloops and twin-masted boats such as yawls and ketches. Its larger surface area increases the speed of the craft in light to moderate winds; in high wind, a smaller jib is usually substituted, and downwind a spinnaker may be used.


A spinnaker is a sail designed specifically for sailing off the wind from a reaching course to a downwind, i.e. with the wind 90–180° off bow. The spinnaker fills with wind and balloons out in front of the boat when it is deployed, called flying. It is constructed of lightweight fabric, usually nylon, and is often brightly coloured. It may be optimised for a particular range of wind angles, as either a reaching or a running spinnaker, by the shaping of the panels and seams.

Used T-Birds of plywood or fiberglass construction are often available for sale in many regions where T-Bird fleets have been organized (see below). These boats offer an economical choice for the sailor interested in becoming a T-Bird owner. Prices can range from under $2,000 for older wood boats that may need restoration or repair in various degrees, up to about $20,000 for a completely equipped newer fiberglass boat in championship form. Average prices for boats in good cruising or racing condition in the U.S. and Canada are typically in the range of $5,000 to $13,000, depending on local market conditions. Compared to other sailboats in this size range, such boats can be considered bargains in terms of racing and cruising performance, and cost.

Plan and specifications


Mainsail Dimensions:

P 31.0 ft
E 13.0 ft
I 26.75 ft
J 8.0 ft


The Thunderbird's exceptional performance can be attributed to a lightweight, 3,650 lb (1,656 kg) hull and rig with V-bottom hull and hard chines. Outstanding stability is provided by a 1,530 lb (694 kg) cast iron keel of advanced design with a 4.79-foot (1.46 m) draft. The sail area is 363 square feet (33.72 square meters) in the mainsail and genoa, and racing boats are equipped with a spinnaker. The Thunderbird (or T-Bird, as it is commonly known) has proven to be fast in both light winds and heavy, often out-performing contemporary displacement-type sailboats of similar or even larger size in local handicap races. By way of comparison, where the PHRF handicap for the Thunderbird is 201-204 (seconds per mile), the J/24 rates 185, the San Juan 24 228-237, the Ericson 26 234, the MacGregor 26 259, the Catalina 27 204.


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Its 7.54 foot (2.30 m) beam makes it possible to haul the boat by trailer, without special permits, for launching, winter storage and for traveling to long-distance racing or cruising destinations.

Pacific Thunderbird variant

In the early 1960s there was a variant made called the "Pacific Thunderbird" designed by Naval Architect Ben Seaborn, the original designer of the Thunderbird class. The sail logo was the Thunderbird logo inside a large letter P. It was a scaled-up version to a LOA of 32 feet (9.8 m). It was made in Japan of fiberglass covered plywood. It had a fixed keel with a depth of about 6 feet (1.8 m), a beam of about 9.5 feet (2.9 m), a self-bailing cockpit, and an inboard engine. The mast height and sail area were also reduced somewhat, so the boat was more stable. Below it had headroom of about 6 feet (1.8 m), a spacious enclosed head, a fixed table with folding leaves, a full galley (sink, icebox, counter, and stove), and births for 5 (with the fifth birth running under the port side cockpit seat). This design was still a fairly fast boat, yet more seaworthy and very comfortable for coastal cruising. There were, however, very few of them sold. [3]

For images of this design, see this site. (Note that this boat was modified to have a bowsprit; the class design does not have this.)

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  3. Personal recollection of Robert G. Benson, whose family bought an early production model and sailed it for a number of years off the Southern California coast.