The Cannon and the Voice of the Generations

This short story features Naerian. He is a young, gifted mechanical tinkerer attached to Clan Iredale. If a waterwheel needs fixing, he's the guy to fix it. These days, however, he spends most of his time agonizing over an age-old dilemma: when is a weapon of war deadly enough? This is no mere philosophical question. Indeed not. The destiny of Clan Iredale hinges on the answer Naerian comes up with. And he doesn't have much time to do it. This isn't like fashioning a new drive belt out of cowhide. A powerful cabal of clans has formed to conquer the Iredales, to wipe them out.
These clans want what the Iredales have: control over the mouth of the Columbia River. The cabal doesn't have the faintest idea what they'll do with lower stretches of the river if and when they get them, let alone with the Columbia River bar. They have no notion of how to keep the navigation channels open, or how they'll keep overseas trade flowing, or how they'll provide wharfage. Pilings? What are those? Buoys? Another mystery.
But never mind. In the short run, they'll happily settle for seizing the stacks of gold they imagine are sitting in Clan Iredales' vaults. After much deliberation, Naerian concludes that if the Iredale's own weapons are more deadly than the cabal's weapons, then the Iredale's weapons will be as deadly as they need to be. Huzzah! So it is that Naerian sets out to fabricate a weapon that will enable the Iredales to prevail against their adversaries. The only downside is that this wonderful plan risks everything that Clan Iredale holds dear.