These materials can be found by defeating Bounty Hunters, Warships, and on occasion, War, regular, and very rarely, even light Class ships. The most common materials; iron, canvas, and pine, can be found by sinking Bounty Hunters. Rare materials; oak, silk, and steel are most often found in the loot from Warships, and other ships, but strangely not ever from regular bounty hunters. As for grog, it has not been released to the game yet.
Grog's game card was changed after a maintenance occurred. Developers confirmed it would be coming to the Test Server along with Rank V and VI Hulls, in March 2012. When the new hulls were released, Grog was not. It is assumed that Grog was canceled from development.