There is a short descritption of it in the french forum: "Manuel d'utillisation" / "Procédure de départ et bateau pilote" , first thread:
that can be translated into:Le bateau pilote, démarre derrière un bateau choisi, et le suit à 2 ités, il contient tous les bateaux
inscrits qui n'ont pas pris le départ.
On reconnait le bateau pilote à ses contours noirs plus marqués.
Donc si vous prenez la course en cours, vous partirez de là.
The pilot boat is a virtual boat.
The pilot boat starts behind a special boat,andt follows her 2 iterations behing. All the boats that have subscribed to the race, but have not yet staret (setting a sail and a hadong) are in the pilot boat (welcome btw).
You can detect the pilot boat with its contour line (border line ?) that is a bit darker black than the other boats and the boat bit greener.
Then, if you start a race that has already started, you'll jump out from her.
On the Clipper race, the name you can see on the pilot boat is "durejournée", although there is a special character instead the "é" (...).
"durejournée" is the most recent boat that applied to the game and to this race.
The pilot boat follows a boat based on her ranking. At the beginning of a race, the folloowed boat is about half of the total ranking. But as the race goes on, the pilot boat will little by little drift to follow a boat from the back of the ranking.
As the ranking can change a lot at the beginning of a race, the pilot boat position can change a lot at every iteration.
Location becomes more "stable" as the race goes on.
The pilot boat and the demo boat are not related.
The demo boat is drawed in orange on the map. The demo boat allows anybody to test the game without registering with a login / pass (with the "Essayer avec le bateau demo" on the home page ("Try with the demo boat", I just checked and there is a not found page when clicking the english flag on the home page, will be fixed soon, sorry).