At what angle should the sail of a sailboat be to produce the maximum speed?

Answer 1

I believe you're asking about sailing up wind. So a better way word your question is:

"When sailing upwind, how far (or what angle) off wind must a sailboat be in order to maximize the wind and produce the fastest hull speed?"

All sailboat makers design their hulls different. However, as varied as sailboats get, they all seem to obey the same basic principles when sailing upwind.

Most sail boats are equipped with a wind vane usually mounted at the top of the main sail mast of the ship. On it are two angled indicators with red flags at the tips (one towards starboard aft and one towards port aft) producing about a 60 degree arc open directly to the stern. If the wind vane is outside the 60 degree arc, you may use the wind. If you are inside the arc, you will get luffing or backing in your sails. The trick is to line up the wind vane so that it is just outside one of the indicators and make the sails taught (but never as taught as possible). That angle is about 35 degrees off wind.

Note that your resultant bearing will be greater than 35 degrees off wind. The boat slicing through the water is not 100% efficient due to varying keels, hull designs and displacements. Also water current can effect your bearing pushing you further off wind.

Once you "gain a feel" for the angle, you'll be able to hit it every time without cheating and looking up at the wind vane for help. Happy sailing.