Deer Isle Koster
Fast | Weatherly | Beautiful
A Swedish, decked sailboat known as the “KDI”
SPECIFICATIONS
Overall Length 14' 0" | Waterline Length 12' 6"
Beam 5' 10" | Waterline width 4’3”
Draft (board up/down) 5" / 36"
Depth amidships 19"
Bare hull weight ~175 lbs | rigged ~250 lbs
Displacement 596 lb
Sail areas 97 / 98 (lug only/sloop)
Bruce Elfstrom, a designer-friend of mine, father of two now grown daughters, and small boat nut, drew the original KDI for his two girls. He was quoted in Small Boat Magazine, "I wanted them to have a big deck to jump off of, climb up on, swim off of -- to go out and just Swallows and Amazons stuff". That sums up the spirit of what was behind Bruce's thinking when he drew the KDI in 2009, inspired by the double-enders of Scandinavia and wanting a modern take on these classic work boats. What resulted was much more. Many describe the KDI as a fusion of the Koster boat with Catboat. The boat is simply fast, with a powerful but not over-canvassed lug rig, and NACA-shaped foils for rudder and centerboard. The hull is very wide for its length which favors sailing speed. That said, the boat rows well because of its lightness and the ability of the aft part of the hull to act as a skeg, which helps the boat track. The oarlock-to-oarlock span of the boat does require 10-foot oars but Bruce uses his KDI's with 9-footers. Two rigs have been drawn for the boat and proven equally effective: a lug only sail and a lug-with-jib rig. A generous fore-deck and side deck makes for extra security and comfort when sailing. Bags and gear can stow beneath the fore deck as well as in side tanks via fitted hatches. The ends of the boat are enclosed and sealed to provide flotation. A wonderful feature of the boat are the floorboards, which can double as a sleeping platform for camping on board with a tent formed over the boom.
Key Features:
Stable and comfortable with generous side seating
NACA shaped foils gives quick performance
Built-in flotation and decking of safety
Note that hull #7 and up are the MkII version which in fact is the same as the two original KDI’s built and still moored in Deer Isle. The Mk 1 kits were narrower and whereas the MkII’s match the beam of the originals but do have a “frying pan” bottom, meaning the first few planks are fitted together “stitch-and-glue” style and glass sheathed. The remaining planks are fit glued-lapstrake. The mark I kits are no longer cut and shipped. The MkII has the original performance or better than the originals and added ease of construction due to the modern kit design.
Complete kit contents for the KDI
plywood kit | timber kit | hardware kit | epoxy kit
Options, Upgrades and Accessories for the KDI
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Lug or lug-sloop option
Vacuum bagging rudder and daggerboard layers (upgrade)
Foil shaped centerboard and rudder (upgrade)
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No options at this time
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Oval vs. Horn oarlocks
Ronstan 12mm RopeGlide fairlead for mast (upgrade from RF59 which is standard)Description text goes here
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Lugsail or Sloop rig available
Oarmaking kit or Shaw & Tenney oars
Sawhorse cradles (highly suggested)
Foil shaped (NACA) rudder and centerboard
CONSTRUCTION PHOTOS
The KDI build is an intermediate level project because of the shapely hull. Most KDI builders have built a boat before, but a motivated first-timer with some good skills could build it from the kit. A strongback composed of precut chipboard is the building base for the boat. Bulkheads are part of the set up and planked over to form the shell of the boat. Upon turnover, the only structure left to build the boat are seats, deck, and trim.
An excellent photo album is kept by first-time boatbuilder Chris Burke on his Facebook page and you are invited to view it HERE.