The Term "Koster Boat" stems from the type of fishing boats build on the Koster Islands west of Strömstad on the Swedish west coast.
The original fishing boats ("Allmoge båtar") were
about 10-12 meters in length , and were relatively broad and round, but had at the same time a deep and sharp underwater body, which made them very seaworthy and well sailing. They were clinker built
with Gaff rig and a bowsprit.
Later it was "copied" to be a Racing & Recreational boat and was fitted with Bermuda Rig and then called "Modern Koster"
popularity of the Modern Kosters rose drastically and in 1930 the "Swedish Kosterbåt Förbund" .
(SKBF) was founded.
In 1934 they launched an uniform rules for Koster Sailboats, giving
following classes: K20 , K22 , K25, K32 , K38 , and K45 . K stands for "kosterbåt" and the numbers indicate the minimum of square meters of sail the boat need to have. Up to 20% larger sail area is
allowed, so for instant a K32 can have between 32 and 38,4 m2 sail area. This means, that the measurements of a boat still plays a role. To which extend, is not known to this site, but the actual class
will be determined by SKBF when a Koster Boat is measured.
SKBF also made a unique Koster Class - K6 - the first boat of which was built in 1944.
It has a LOA of 6.25 m, a Beam of 2.25 and a sail area of 18 m2.
In 1966,SKBF announced a design competition under the "Koster Rule" for K25. This was won by Lars-Olof Norlin with a construction in fibreglass reinforced polyester - Allegro 27, thus confirming
fibreglass to be a material to be reckoned with for future boat building.
The first comprehensive fibreglass production, however, started already in 1964 when the first Laurin 32 saw the day of light
in Malmö Flyg Industry.