That depends on what sort of sails you have and if you have a keelstone. You don't sail directly into the wind but you can angle into it. A properly designed sailing ship can get up to quite an acute angle. It's all a matter of transfering the kinetic energy transfered from the wind into the hull via the keelstone. I don't fully understand the physics of it. If we have any mariners on the forum perhaps they might be able to enlighten us?