Brotherband series - The Stern Chase #9 by John Flanagan

Pirates have stolen the Skandians' best ship and it's up to Hal and the Heron brotherband to find them in the unputdownable ninth adventure in the New York Times bestselling series. Outnumbered but determined, the Herons are ready for action. The scene is set for an epic battle at sea . . .

For years now, the Skandians have been the guardians of the Stormwhite Sea, stopping piracy wherever they find it. But there are some who don't like the Skandians' new role. When their enemies strike at the heart of Hallasholm, damaging every ship and stealing the pride of the fleet, there is one hope.

Hal's ship, the newly rebuilt Heron, was being repaired so the attackers didn't find her. Hal and the Heron brotherband - along with the Oberjarl, Erak - set off to find Wolfwind. But when they discover the thieves are using Wolfwind to plunder ships and towns and blame the Skandians, Hal realises the pirates have a more sinister plan.