Um, given the Merrimack & Monitor famously beat upon each other until the light failed and a draw ensued, I don't think flame-bombs would make much of a difference.
But, given the results when any iron-clad tackled a *wooden* warship on river or coast, you didn't need flame-bombs...
{ Hasty re-Google for some stuff I noticed last night...}
Paixhans developed a delaying mechanism which, for the first time, allowed shells to be fired safely in high-powered flat-trajectory guns. The effect of explosive shells hitting wooden hulls and setting them aflame was devastating, and was demonstrated in trials against the two-decker
Pacificateur in 1824.
The shells which produced those very extensive ravages upon the Pacificator hulk in the experiments made at Brest, in 1821 and 1824, upon the evidences of which the French naval shell system was founded, were loaded shells, having fuzes attached, which, ignited by the explosion of the discharge in the gun, continued to burn for a time somewhat greater than that of the estimated flight, and then exploded; thus producing the maximum effect which any shell is capable of producing on a ship.
— A treatise on naval gunnery by Sir Howard Douglas.[4]
Dahlgren guns aka 'soda bottles' were better made than Paixhan's and, remarkably, never exploded in service...
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A modern version of the incendiary shell was developed in 1857 by the British and was known as
Martin's shell after its inventor. The shell was filled with molten iron and was intended to break up on impact with an enemy ship, splashing molten iron on the target. It was used by the Royal Navy between 1860 and 1869, replacing
Heated shot as an anti-ship, incendiary projectile.
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