Hobie Cat 18 User Manual page 12

Points of Sail vs. Boat Speed
Wind speed = 10 MPH
Close Hauled
Close Reach
290°
280°
270°
Beam Reach
260°
250°
Broad Reach
The heavy line on this graph shows the speeds that a catamaran can achieve when sailing on different points of
sail, with the wind at 10 miles per hour. The heavy line shows that the highest speed is achieved on a beam
reach, where a cat can do 14 MPH; that is faster than the speed of the wind.
The graph also shows that doing straight down wind is very slow, with boat speed of less than 5 miles per hour.
If you sail 50° left or right of straight down wind, you can do 10 miles per hour. Sailing off on a broad reach
and then jibing and sailing back to the center will cause you to travel farther, but by traveling twice as fast, you
still come out way ahead. Again the point is to keep the sail generating forward lift (working like a wing) by
keeping the leeward telltales flowing. Note: Telltale location is critical, also don't expect smooth airflow
across the entire sail especially on a broad reach. Telltales all over the sail are not only worthless, but are very
distracting.
Upwind is similar to down wind in that if you take the shortest route, you go very slow. If you foot off you
have better speed, but will have to sail extra distance. If you foot off too much, you have great speed, but the
increased distance becomes too great. So where is that magic point that gets you upwind the quickest? It is
close to 45° from the true wind which is about 30° off the apparent wind. There is no easy answer to finding
this point, if there were, sailboat racing would be as easy as pushing on the gas pedal. The fastest point of sail
varies with boat type, wind speed, water condition, crew weight, etc.; but, IF IN DOUBT, FOOT!! The next
chart "Upwind courses,What is optimum?" will show you why this is true. Sailing upwind with other boats
will help you learn how to trim your sails and to find that magic point or "groove" on your boat.
Data Reference - "Aero-Hydrodynamics of Sailing" by C. A. Marchaj, page 87
Hobie University, NAHCA
340°
330°
310°
300°
240°
230°
220°
210°
200°
WIND
10°
350°
15
20°
MPH
10
5
Run
160°
190°
170°
180°
Page 7
This speed data is
typical for a Hobie 20
Close Hauled
30°
50°
60°
70°
80°
90°
100°
110°
120°
130°
140°
150°
Broad Reach
Close Reach
Beam Reach
30 Mar 02