Sailing theory for flatbottoms

Brief theory on flat-bottomed sailing boats, some differences with keel yachts

Flatbottom sailing for kielyacht skipper

Brief explanation of specific terms

Gaff rig

Flat bottom sailing baots have a traditional rig with a gaff mainsail on the will of the "Rakbanden" (balls) kept it at the mast.
You can bet on all the courses the mainsail.
What you should know:
It is better while setting the sails, not to steer the ship directly into the wind. The tree can be eased a bit already during you set the sails caus then he is located outboard and not swinging back and forth over your heads on board.

Running backstays

Larger flat-bottomed sailing boats (from about 11 meters) often have running backstays. The running backstays provide extra support for the mast. You need not worry that breaks the mast, if you just forget the runner set. The backstays also make sure that the luff of the sail is under tension when sailing close-hauled. So it's a little sail trimming.
Support for the mast with the same function as a permanent backstay on keel yachts.
What you should know:
The running backstay is eased to Lee, so that the curvature of the mainsail is getting enough space. The runner on the windward side is defined. Tighten the running backstay well in high wind.
Winch on a flatbottom sailing yacht Winch on a flatbottom sailing yacht

No Keel: Shallow draft

Flat-bottomed sailing have no keel, but a more or less flat or even slightly rounded hull shape. Thus they have little depth, ideal for the Dutch Wadden.
Flat-bottomed sailing in shallow water are in their element and you can dry out with the vessels on a sand bank in the Wadden Sea.
What you should know:
When applying to a quay or in a lock with wind, the slower the ship becomes, the greater the drift.


To sail a close-hauled course, the flat-bottomed sailing boats are equipped with lee-boards. The sword is always used on the leeward side, the side where the wind is blowing towards. The ship is based on the sword and has yet to be something like a keel.
Variable depth, you can determine how much you put down the lee-board.
What you should know:
If you are sailing downwind you do not need a lee-board. At a downwind course requires a sword just a little bit, which then simplifies the control and handling of the ship. The more you sail a close-hauled course the more you can sink the sword.


Flat-bottomed sailing boats maintain their stability over the width of the ship. Width is different than ballast. The width ensures that the ship gets less lean. Similar to a catamaran. Another advantage is the width of the ship, that it provides a relatively large interior.
Ideal family boat: There is always a very large interior space and even in strong wind heeling under sail is much less than with a keel yacht.
Lemsteraak VROUWE FRANCISKA falling dry Lemsteraak VROUWE FRANCISKA falling dry

Mass of the ship

Flat bottom are usually heavier than keel yachts. The displacement of a flat bottom sailing boat is fast at 10 tons or more.
Calm sailing behavior

Maneuvering with a flat-bottomed sailing vessel

Flat-bottomed ships are heavier than keel yachts and have a will of its own. This is partly due to the mass and secondly because they are more sensitive to side winds and drift off to. If you have it once in your fingers, you can add an extra dimension your skipper skills. The control of lateral motion is of course important on every ship.

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