Building a usable wharf before a full naval base

How long would a defended island need to build useful port facilities?

No firm construction time is given, but a heavy unloading wharf is a much smaller project than a capital-ship maintenance base.

A new unloading point would need imported materials and construction equipment before work could begin. One proposal beaches an expendable merchant ship and uses its derricks to unload equipment for the first works. A base maintaining large capital ships could take years and would need dry docks. A substantial wharf or quay for unloading fifteen-inch guns and their battery materials is a smaller undertaking. If the islands can support one another, that facility could turn one island into the main hub for heavier defences.