One of the recurring themes in accounts of naval combat during the Age of Sail is the notion that splinters were more deadly than the projectile itself. There are doubters. But I am not one of them.
When a kinetic projectile hits an object it has two courses of action. It can penetrate or it can rebound (yes, some will say embed is a third choice but it is merely a subset of penetration.)
If it is of sufficiently high velocity to cleanly penetrate it will produce little in the way of splintering making an impact that is somewhat analogous to an icepick, that is, a hole approximately the size of the projo. Of course, in a sailing ship the aftermath of such a penetration was a significant emotional event to those on the same deck as the projo would not have enough kinetic energy to pass out the other side of the ship but would rather rattle around until its energy was spent.
If the projectile is only barely able to penetrate then the effect would more closely resemble that made by a sledgehammer. The entry hole would more than likely be a jagged square as the planks forming hull would be shattered by the impact. The pieces of the hull thus broken off would be propelled inward at approximately the same speed as the projo.
Should the cannonball fail to penetrate it would still impart it’s kinetic energy to the hull. This would cause the planks to quickly accelerate inward and then rebound. The impact of the projo creates an effect on the other side of the planks known as spalliing, that is, the interior of the plank, and in the case of a large frigate such as the USS Constitution that plank was some 22″ thick, is shattered resulting in splinters moving at several hundred feet per second.
Below shows an aluminum pellet, approaching from the left, hitting an aluminum plate. The pellet disintegrates but it creates an shower of hot, high velocity fragments on the inside.
One of the reasons the rather low velocity carronade gained popularity (in addition to providing improved hitting power to smaller ships, requiring fewer men to crew the piece, and using less powder per shot) was the fact that the carronade round worked in the sledgehammer model, not only making disproportionately large holes in the target ship but creating lethal splinters.