The Hammer isn’t a natural island, but a massive earth elemental. It never ventures far from its mapped position, but it has no love of ships; any vessel that draws too close may be shattered by a hurled stone or a mighty fist. Though it’s possible airships might reach the island safely, they’ve only been in operation for about a decade—and airships rely on docking towers that the gnomes, quite happy with their fleet, have proven uninterested in constructing.
Source: Chronicles of Eberron
Without a proper port and subject to the whims of the elemental, The Hammer currently does not support any form of trade. The warforged rely on walking out to their anchored ship and climbing up from the bottom.
Source: Politics of the Lhazaar Principalities