ECO 6

By Bernd Kohler - The Netherlands

The ECO 6 is clearly an enlarged version of our well known ECOnomy cruiser. The ECOnomy cruiser is 5.5m long with a beam of 2.5m.

One of my clients in Brazil, who by the way has made these beautiful renderings of the boat, wanted to use the Gunter rig and bigger ECO. By looking at the possibilities new ideas could be realized - bigger cockpit (for dimensions see lay out). The big surprise came as I could find a space for a separate toilet room. A bit unusual for such a small cat but the fairer sex will appreciate it.

The jib stay is connected to a bridle, the compression load is handled by the front beam which is made from a readily available aluminium tube. The trampoline is also attached to the front beam. Handling the anchor etc can be done from here, low and safe.

The front seats are a good place to be when underway in warm climates. Good ventilation is ensured by a big front hatch and forward opening windows in the front seat area.

Another addition are the seat extensions. Their function is twofold, first to enhance stability and if folded up the they are back rests. Other small differences: I moved the rudder link to the back of the rudder housing. In this way the main sheet can travel freely on its rail.

The Gunter rig is more or less the same as for my KD 650. The main sail is now attached to a boom. Again drawings show not only how to build the Gunter rig but also the boom. The jib is self tending.


L.O.A. 6.00 m
Beam 2.84 m
Beam c/c 2.24 m
Draught hull/board 0.22/1.00m
Weight 360 kg
Weight max. CWL 750 kg
Main 14.6 m2
Jib 4.6 m2

Rendering ECO 6

Speed and stability

A bit more about this issue. Stability on a small family cruising boat is paramount. I was happy that the regulations in Brazil permit a trailing width of 2.85m and I was designing for this maximum. The result is not bad. See dynamic stability below:

The diagram shows the static stability. Which is almost 1000 kilograms. The other curves show the stability for 5, 10, 15, and 20 knots of wind. The calculations are made with a safety making of 90%. Wind measurements have shown that the wind fluctuations can be that big. Example: In a force four wind you can have also force 7!!
Speed prediction. Because of the good stability of the boat, the boat has also more speed. The prediction shows the speed at differed wind speeds with a weight of the boat of 550 kilograms (red line) and 750 kilograms (white line). The speed prediction is without wave action. This means the boat can be faster on flat water and will be slower in big waves.


Construction is like all my boats the time proven (ply)wood/glass, Epoxy composite system. Easy to build also by a first time boat builder. Time to build the boat and rig will be around 600 hours.

The picture shows the internal structure of the boat.

The plans for the boat consists of 33 drawings. All technical drawings are to scale 1 : 1. The DXF files can be used for CNC cutting. But the simple shapes of for instance the bulkheads are not worth the trouble. The description outlines the construction of the boat and gives a detailed description with pictures of how to build the hollow rudders and the daggerboard in a relative easy way.


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