**Did your ever heard the rule "length runs?"**

This rule is based on the so-called hullspeed of a displacement vessel. It grows with the distance between bow and stern. This distance is called the length of the waterline. At hullspeed the vessel is "trapped" between its bow and stern wave.

**The Beaufort Scale**

This scale for describing the wind speed was developed by Sir Francis Beaufort in 1806. While commanding the H.M.S. Woolwich, he observed the effect on the sails and ship. He defined twelve different classes for the power of the wind. Since this time the unit for the wind strength is called "Beaufort" [Bft]. In 1835, at the First International Meteorological Conference in Brussels, the Beaufort scale was established as international standard.

A common issue for watersports refers to the distance to the horizon. Often the question is asked, how far you can see a moving ship just beyond the horizon. We do suspect that this distance will depend on the vertical size of the ship and the observer's elevation above the sea surface. With the help of some simple mathematical considerations, applying not more than the Pythagorean theorem, we are able to answer this question.