The short answer....... protection.
The long answer based on a general search that yielded the following. Not sue I am buying all of this, but it makes sense for the most part. FWIW--->
Warships in the afe of sail used extra internal planking (like they used doubled frames) on gunwale areas, unlike most merchant ships, primarily for
structural reinforcement to withstand heavy cannon recoil, gunfire impact, and severe rolling in heavy seas, providing crucial strength where the hull curved dramatically
(tumble home??) and needed to support massive weight and stress, a requirement not as critical for less heavily armed merchant vessels. While both used
carvel (smooth-planked) hulls, warships needed a robust internal skeleton, often with thicker timbers or added planking, to bear immense forces and maintain integrity, making their structure inherently heavier and stronger in these high-stress zones.
Why Warships Needed This Extra Strength:
- Cannon Recoil: Firing large naval cannons generated immense force, requiring the hull to be exceptionally strong to absorb these shockwaves without failing.
- Gunfire Resistance: Warships needed to withstand enemy cannonballs impacting the hull, making robust framing essential to prevent breaches.
- Heavy Seas & Stability: The weight of heavy guns and the need for stability in rough Atlantic conditions put extreme stress on the upper parts of the hull (topsides), necessitating reinforced frames.
Why Merchant Ships Often Didn't:
- Lighter Loads: Merchant ships carried cargo, not heavy artillery, so they didn't experience the same violent stresses from broadsides.
- Cost & Timber Efficiency: Extra internal planking used more valuable timber and added weight, increasing build costs – a significant consideration for mercantile ventures focused on profit.
- Simpler Needs: Merchant vessels prioritized cargo space and seaworthiness for trade, not battle readiness, so standard framing (though still robust) was sufficient.
In essence, the extra internal planking on warship gunwales was a design adaptation for
combat survivability and performance under extreme stress, a luxury not afforded or needed by most merchant ships of the era.
Allan
