Manoeuvring takes time! You have to get on the deck, take out the sails, hoist them, pull, slacken...
Fortunately, on Virtual Regatta, it is much easier: just change course or select a sail from the game dashboard without even having to put on a coat!
In certain circumstances, these actions can impact the speed of your boat: in game, every time you change sails, tack or gybe, your boat slows down slightly. When things settle down, your speed increases again. This slowdown occurs because of manoeuvering.
The manoeuvering time can be reduced by equipping pro winches.