Were there any medieval European ships designed to be "bomb ships" in the manner of 18th-century bomb ketches--i.e. with an unusually large forward-firing piece of ordnance designed for use against land targets? I'm familiar with the forward-firing guns on late-medieval and Renaissance galleys, but they didn't seem to have been primarily meant for engaging land targets--or am I mistaken in that? There's also the tantalizing hint that Mons Meg might have been mounted on a ship, but no confirmation that I know of.

So...well, anybody with a clue?

I came across this incident in The Memory Palace of Matteo Ricci.

Setting: During the Siege of Antwerp in on April 5th, 1585, the defenders, trying to dislodge the Spanish troops who had built a bridge of boats across the River Scheldt to block supplies from reaching the city, floated downstream a new type of mine designed by their consultant, the Italian engineer, Frederico Giambelli.

Quote:

"This "mine" was in fact a seventy-ton ship whose hold was lined with bricks and filled with an admixture of gunpowder and sal ammoniac, over which were placed layers of tombstones, marble shards, metal boat hooks, stones, and nails. The vast mass of explosives and projectiles was covered by a roof of heavy stone slabs so that the blast would be forced sideways and outward instead of upward. The vessel exploded when a carefully prepared fuse reached the hold, just at the moment the Spanish troops were trying to maneuver it out of the way. Though the casualties could not be counted because the bodies were so mutilated, between four and eight-hundred men were killed in the one explosion, establishing some kind of new benchmark in the history of war."

More about this incident is written online here: http://www2.cddc.vt.edu/gutenberg/etext04/jm40v10.txt

I hope that helps.

Not quite what I'm looking for, unfortunately; it's the medieval version of this, if any existed.