The Heron is a boat built by Hal. It was originally supposed to be for an old Skandian warrior and his friends, but when he died, Hal bought it for his own. He designed the sail, getting inspiration from the wings of a heron, hence the name, the Heron. The ship is built with a fore-and-aft-sail plan.
It was also used in Brotherband training to be the ship for the brotherband, the Herons.
It isn't a very big boat, but doesn't need to be as it's crew isn't large.
The thing that sets the Heron apart is it's unusual sail which was designed by Hal, enabling in to sail into the wind. The sail is triangular and allows the ship to go faster and more directly into the wind.
Another addition is the keel box. Hal installs this in The Invaders. Hal can insert a fin inside the keel box to reduce The Heron's drift downwind.