Koster Rule

• In cooperation with Nisse Dunér of the SS Fram, the "Koster Rule" is now translated into English as follows:
1. The koster boat is a double-ender, i.e the stern is sharp or rounded with an external hinged rudder
2. The stem shall be straight or inclined a max. 60 degrees
3. The construction of wooden keel, stem, stern post, frames etc. has to be strong
4. The ballast keel shall be of Iron and run almost the full length of the wooden keel
5. The profile of the lines of the underwater body shall be straight or moderately convex (not concave)
6. The length of the mast shall be not more than 3 times the length of the main boom
• This site will only allow few exceptions to the above rule i.e. the L38, which doesn't comply with rule 5 and a few boats with Lead Keel (Rule 4).
• On the other hand we are also sharpen the Rule by only allowing Laurin's Koster boats, designed with a "Whaledeck" 
• We allow these exceptions as these boats in other ways follow Arvin Laurin's "Koster interpretation" and therefore seem to be "natural members of the Family".
• This, however, must not be taken as an attempt to argue the validity of the Koster Rule!