The Technology of the Ironclads

Note: The following article was published in two parts in the Naval Gazette, Vol. II, No. 6, and Vol. III, No. 1 and is Copyright © 1998 Mark F. Jenkins.

The ironclads of the Union and Confederate Navies dominate everyone's thinking about the naval aspect of the American Civil War. Although it may be successfully argued that wooden vessels still bore the brunt of the fighting (and are therefore due a larger measure of credit), the ironclads embodied the most modern designs of the era and reflected the oncoming Industrial Revolution. Some were intelligently designed and consciously revolutionary; many more were best described as haphazard, and a number were outright failures. Regardless, these vessels were the heralds of a new age of naval technology. Unlike many other advances throughout history, this was widely recognized at the time. A correspondent from the London Times may have said it best when he wrote, after witnessing the battle between the Monitor and the Virginia (ex-Merrimack), that the might British Navy had effectively been reduced to only two ships.

The following overview of the technology of the ironclads is divided into sections covering Armor, Armament, Propulsion, Control Systems, and Design and Construction.


Gunnery tests conducted by both sides early in the war demonstrated that armor thicknesses of two inches or less were insufficient to shield against naval gunfire. On the other hand, it was almost insurmountably difficult to make plating thicker than this, so most ironclads had multiple layers of plate, called "laminated" plating. Two layers of two-inch plate was generally the standard for Southern ironclads; deviations from this usually resulted from lack of iron (as with the Neuse), though a few had a third layer (such as the Tennessee and Columbia). The Monitor had no fewer than eight layers of one-inch plate on her turret. This created problems in fastening the plates together, as it raised the specter of sheared-off boltheads flying around the inside of the turret. This happened in the pilothouse of the Catskill off Fort Wagner, killing the fleet captain of the South Atlantic Blockading Squadron. Plates were usually rolled (cast in oblong blocks and rolled out to their desired dimensions) but on some vessels were actually hammered out (forged plate); this was done to the armor of the New Ironsides, and may partially account for the strength of that vessel's cladding.

All forms of iron armor were highly experimental at the beginning of the war, and several fairly exotic combinations were tried and used. The Galena possessed a complex "rail and plate" system (sometimes misinterpreted to mean T- rails with an outer plate sheathing), assembled in a similar manner to clapboard siding on a house, but it proved vulnerable at Drewry's Bluff. The Keokuk had a weird arrangements of slats of wood interspersed with edge-on iron plates or bars, which proved inadequate at Fort Sumter (she has the dubious distinction of being the only ironclad sunk by gunfire, notwithstanding the Cincinnati, sunk by the Vicksburg batteries; but the latter was hit in her unarmored stern, and was later raised and returned to service anyway). Several of William D. Porter's designs for the riverine ironclads included a layer of rubber or gutta-percha under the iron plates, presumably in the hope that it would help shot rebound off of the armor, but it proved useless and quickly rotted away in the humid Southern climate. Some ships simply used T-rails, despite the recognized fact that they were inferior to rolled plating, though many of the "City" class ironclads supplemented their plate armor with T-rails in certain locations. One cautionary note: some sources refer to ships being plated with "rail road iron," but this does not necessarily mean T-rails. The Albemarle, for example, was armored with rolled plates, but the plates had originally been T-rails, so the ship was often mentioned to be armored with railroad iron. Ships of both sides often had their armor coated with lard or tallow grease in an attempt to deflect shot. The effectiveness of this practice is somewhat arguable, but it would at least have had a positive role in defense against boarding parties, had this ever occurred. The chief result was an often-reported stink as the slush was heated on an iron surface under the blazing Southern sun.

The best armor configuration during the Civil War was found to be the forerunner of composite armor, where several layers of plate were mounted over a solid wooden sheathing, which was the usual method for armoring a Southern ironclad. Had the South possessed enough iron and forging facilities to clad its ships in six or more inches of plate over this sturdy bulkhead, the rams would have proved considerably more formidable. The wood provided a resiliency that the relatively brittle iron plating could not supply.

The original "floating batteries" (Devastation, Lave, Tonnant) used by the French at Sevastopol in 1854 introduced the use of a boxlike armor shield, slightly inclined. Nearly all of the casemated ironclads of the Civil War followed this pattern. Inclined armor is sometimes supposed to have saved weight, but this is a misconception. The volume of iron (and therefore its weight) was still the same, and there was a loss of usable space behind the shield. The advantage of inclined armor lay in the fact that a projectile traveling more or less parallel to the water (direct fire) would strike the shield at a considerable angle of incidence, directing its kinetic energy upward rather than concentrating it fully against the shield. Naturally, this advantage was lost when faced with plunging fire.

As a side note, it is interesting to observe that all monitor turrets were simple right cylinders. This was primarily for ease of construction (Ericsson's original design for the Monitor bore a hemispherical turret, and the turrets on James B. Eads' first-draft plans for the Osage and Milwaukee classes were truncated cones, but all of these were discarded in the final plans). Though vertically-sided, incoming fire that was at all tangential to the turret wall would have been deflected away in the horizontal plane to some extent, giving the monitor turret some of the advantages of the inclined shield without the corresponding loss of space behind the shield or the vulnerability to plunging fire (note that a projectile traveling in a ballistic trajectory has no lateral motion unless deflected in some way). The top of the turret and the monitor's deck, of course, enjoyed no such protection.

One significant weakness of the armoring of all the ironclads was a vulnerability to plunging fire. In the practice of the day, however, direct fire was the norm, so this vulnerability did not often become a significant factor.

Vessels were frequently armored in a style that would be called "all-or-nothing" in later American battleships, where vital systems and specific areas were heavily protected, leaving less vital areas with lighter shielding, though this was not applied systematically. The closest to this concept were the "City" class ironclads, designed with armor forward (to support the head-on-combat concept), armor abreast of the boilers and engines to protect them, an armored pilothouse and no armor elsewhere. When this proved inadequate, more armor was retrofitted, but still in specific functional areas, such as around the steam drum and engines, inside the vessel.

One item of some uncertainty is the principle behind the monitors' "overhang;" that is, the extension of the raftlike deck over the sides of the more conventional lower hull. Ericsson intended this as a source of stability as a gun platform, reportedly getting the idea from logging rafts in his native Sweden. This overhang proved to be vulnerable to the hammering of waves in a heavy sea, and it is thought that the Monitor was lost partly due to this hammering splitting the seams between the raft and the hull. This is somewhat controversial, as many accounts place primary blame on the poorly-sealed base of the turret; but naval officers of the time remained quite wary of the overhang.

However, the overhang also provided some protective benefits. A ram would encounter the overhang (which extended for some distance below the waterline) prior to striking the hull, and the solid raft would take relatively superficial damage from this. A shot entering the water next to the vessel, hulling a conventional ship, would have to travel some extra distance underneath the water before encountering the monitor's hull, robbing it of kinetic energy. No monitors were successfully rammed or hulled, so the exact extent of these benefits is unclear, but logic maintains that there must have been some.

The most important benefit accruing from the overhang was the protection it afforded the screw, rudder, and anchor. The screw and rudder were under the fantail, basically unavailable as targets, and Ericsson's patented system for raising and lowering the anchor under fire was located under the bow overhang. The overhang was reduced in successive monitor classes, and disappeared altogether in some (non-Ericsson) types, such as the Onondaga.


The rifled cannon was a relatively new development in naval artillery at the time of the Civil War, and many artillerists, John Dahlgren a prime example, maintained that smoothbores were still superior at ordinary ranges of battle, and burst less often than rifles. However, the Union Parrott rifles and Confederate Brooke rifles frequently found their way onto ironclad gundecks. Parrott rifles formed part of the batteries of the New Ironsides, Galena, Roanoke, Onondaga, among others, and nearly every Southern ironclad had 6.4" or 7" Brooke rifles as part of its armament.

Weapons were commonly rated in terms of inches (of the bore of the weapon) or pounds (of the weight of a solid shot). It's not easy to directly compare the two, especially since the weapons measured in inches were usually smoothbores and the weapons rated in pounds were often rifles, usually with enlongated projectiles. Dahlgren pieces were usually named with the Roman numeral of the caliber (for example, XI-inch for 11", and XV-inch for 15"). Also, there was disparity between Army and Navy nomenclature; the weapon that the Union Navy called a 150-pounder was named a 200-pounder in Union Army service (the typical weight of the shell fired by this piece was in fact 152 pounds).

Occasionally, smoothbores were rebored to make them into rifles, but this produced pieces with dangerous weaknesses. The "City" class gunboats were initially equipped with several old Army cannon rebored to make them 42-pounder rifles, but they so frequently burst that they were cheerfully disposed of when new pieces became available; crews were known to have simply tossed them overboard, and good riddance.

Rifles had significant advantages over smoothbores in range, accuracy, and penetrating power, though their projectiles could not be skipped over the water, and they had a tendency to bury themselves in the ground, reducing the shell-blast effect. The big 15" Dahlgren smoothbores mounted on most monitors were devastating at close range, able to penetrate the heaviest-armored Southern ironclads, but their effectiveness dropped off rapidly with distance. Eventually, of course, the rifle completely replaced the smoothbore in naval artillery.

The most important pieces of Union naval ordnance were the 11" Dahlgren smoothbore (used in the Monitor, New Ironsides, Keokuk, the Passaic, Osage, Milwaukee, and Sandusky classes, along with the failed Casco class); the 15" Dahlgren smoothbore (used in the Passaic, Canonicus, and Monadnock classes, the Dictator, and the never- completed Dunderberg and Kalamazoo class ships); and the 100- and 150- pounder Parrott rifles. Southern ironclads, as previously mentioned, usually bore various sizes of Brooke rifles, but many had a hodgepodge of other weapons, mostly acquired at the fall of the Gosport Navy Yard at Norfolk.

The major types of ammunition in use were the explosive shell and the solid shot. Less frequently used but still available were grapeshot and "hot shot."

Explosive shells, equipped with crude variable-time fuses, were most effective against wooden vessels and fortifications. Shells would often set fire to wooden ships, but more importantly, the bursting action of the shell would fill the ship with deadly splinters (often of considerable length-- a foot or more, for example). They would cause less actual damage to fortifications (especially if they were earthworks), but flying shrapnel caused casualties and set off secondary explosions among the fort's ammunition and ordnance, in addition to setting fire to flammable structures. They were generally not of much use against ironclads.

Solid shot, particularly of the few conical steel-tipped varieties, was the precursor of modern armor-piercing shot. When propelled by a sufficient powder charge, they could and did penetrate ironclad armor. Solid shot was also effective against stone or masonry fortifications, but mostly ineffective against earthworks; if a shot hit such a fortification squarely, it would tend to burrow in and stay there, basically making the earthworks stronger.

Grapeshot was a larger version of "canister," essentially turning the cannon into a giant shotgun for antipersonnel work. It was seldom used, as most naval battles were fought at ranges too long for grape (since the projectiles were considerably smaller than the bore, a lot of the propulsive force of the charge was lost and grape could not be fired at anything above pointblank range). Some vessels, such as the Virginia at Hampton Roads, carried slightly sub-caliber cannon balls to be heated in the furnace and fired as "hot shot," --devastating to wooden vessels. However, hot shot posed nearly as great a fire risk on board the firing ship as to the target, and the risk was usually not taken.

Of equal importance to the type of piece and the type of ammunition was the type of gun mounting arrangement employed. Many vessels of various types, Northern and Southern, mounted guns in the traditional fixed-broadside pattern, simply lined up at a row of gunports piercing the ship's side. The "City" class ironclads and other casemate ironclads on the rivers also employed this arrangement for forward and after guns. Many ships improved on this arrangement through the use of pivot guns, pieces on special tackles to swing them to fire out of one or two additional gunports. The Keokuk, Albemarle, Neuse, and the never-completed Wilmington were armed solely with two pivot guns each. In a sense, this could be considered a halfway step between the fixed broadside and the turret.

The most effective method of mounting guns, of course, was the monitor turret, an armored rotating gun platform that allowed the guns to fire at nearly any angle, regardless of the bearing of the ship. Ericsson's ideal was a complete 360° field of fire, but this was never attained in any completed vessel. The original Monitor could not fire directly forward, since the pilothouse was in the way, and every successive design had permanent smokestacks, deckhouses, or even other turrets blocking a portion of the field of fire. Nevertheless, the flexibility in aiming a monitor's guns gave it an important advantage against vessels mounting fixed broadside or pivot guns. To be sure, there were other problems. The limited space inside a monitor turret made it impossible for the guns to roll backward with the recoil in the usual manner, so there was special mechanical friction gear to absorb the recoil, requiring the gun crew to set this gear lest the guns jump their carriages upon firing. The engine power used to turn the turret was a little different in the various monitor classes, so the turrets turned at different rates and some were not accurate enough to stop on a precise bearing; in fact, the Monitor's own turret engine was so inaccurate that the turret crew began firing "on the fly" without stopping the turret, and eventually left the turret stationary and let the ship's motion bring the target into view. This somewhat defeated the purpose of the turret. However, successive classes improved on this situation.


The first practical steamships were in use four decades prior to the Civil War, and the first steam warships predated the war by some twenty years. But although even the conservative United States Navy had stopped building sailing warships, the engines that were being put in the new vessels were still relatively primitive. The steam frigate Merrimack's engines were so notoriously unreliable that they were rarely used, and they were the reason that the vessel was laid up at Gosport when the navy yard fell to the Confederacy. A heroic attempt was made to repair them when the vessel was reincarnated as the Virginia, but they never did work very well.

Steam engines were very much built on a rule-of-thumb basis, despite mass production of basic parts. Thanks to the work of men like the Union's Benjamin Isherwood, steam engines were approaching acceptable levels of reliability by the end of the war, but during most of the action engines were highly temperamental and gave each ship highly individual qualities, even in otherwise-indistinguishable sister ships. For instance, the "City" class gunboats were so similar in appearance that painted bands had to be added to the smokestacks to aid in differentiating the ships, and yet the Cairo was widely known as the fastest of the class, while the Carondelet was notoriously slow (that this did not necessarily have any bearing on their success or failure can be discerned from their respective careers). Steam engines of the era are generally described in terms of number of boilers, the bore (diameter) and stroke (travel- distance of the piston) of the cylinders, and the output horsepower (usually a few hundred).

The riverine ironclads in particular possessed engines very similar to (and sometimes taken from) the old river steamboats, which were effectively of an earlier generation of machinery than the engines in use on the coastal vessels. They were cheap to build, easy to maintain in the absence of repair facilities, and could run on firewood rather than coal in a pinch, though not very well. On the other hand, they operated at high pressure and were in constant danger of explosion, either through inattention or enemy action (as in the cases of the Essex and Mound City).

Many vessels carried engines that had previously seen service. Ironclads such as the Benton, Eastport, Atlanta, and Roanoke retained the engines that had driven them before they were converted to ironclads. In general, the additional weight of guns and armor severely hampered performance. Other ships, especially several Southern ironclads, utilized engines taken directly from other vessels. This rarely yielded effective results, and in some cases (such as the Georgia), the ship was virtually immobilized or at least rendered useless by lack of engine power.

Most ironclads were driven by screw propellers, but some bore wheels. Wheels were obviously the poorer choice for propulsion; they made for a big silhouette and were difficult to armor effectively, and were less efficient in driving the ship. On the other hand, sidewheels afforded better maneuverability in limited space, aided a shallower draft, and better fitted the engines generally available on the rivers. In some ships (Benton, Essex, the "City" class boats, Louisiana, Missouri, and the first incarnation of the Jackson), the wheels were moved inboard. This increased their protection but decreased most of the value obtained by having them in the first place. They could not be turned independently, so the rudders were the only means of directing the ship's course, and there was a considerable loss of power from the turbulence under the ship's stern. The most extreme case was the Louisiana, where the wheels were placed in tandem, one after another, and the turbulence of the first wheel rendered the second so inadequate that the ship could not even stem the Mississippi's current.

The converted sidewheelers (Eastport, Lafayette, Choctaw, Baltic) fared somewhat better, though the newly- constructed sidewheelers (Indianola, Tuscumbia, Chillicothe, Nashville) had significant problems. The sidewheelers had very imposing silhouettes that gave an impression of great power not usually borne out be performance. Oddly enough, the most successful of the wheeled ironclads were the Eads sternwheel monitors Osage and Neosho. These curious hybrid ships were swift with a very shallow draft, though their turning radius left something to be desired.

A few vessels' designers attempted to split the difference and equip their ships with both wheels and screws. None of these vessels (Louisiana, Indianola, Tuscumbia) were successes in this regard.

Of prime importance to the health of the ships' crews and the efficiency of the engines were the systems for ventilation and draft. Ventilators circulated fresh air through the ship, and draft systems pulled new air into the furnace. At their simplest (as in Southern ironclads), ventilation was provided by windsails, large trumpet-shaped tubes on deck leading down into the lower decks, which could be rotated according to wind direction, or by any opening, such as the gunports or the grated roof possessed by many casemated ironclads. Because of the vulnerability of such arrangements, ventilation was usually poorest in battle, and crews often suffered hellish temperatures under the iron shields in the hot southern summers.

Northern monitors, beginning with the original Monitor, introduced a system of machine-driven fans and blowers to force fresh air into the hull and circulate it. These systems were not perfectly effective, and small windsails were often placed over open decklights (small horizontal portholes in the deck, usually covered by a glass window and covered by an iron plate during action) to supplement ventilation.

True forced-draft engines were still a thing of the future, so ironclads depended heavily on the design and condition of their smokestacks for engine power. As smoke and gases were drawn out of the stack, it created a low pressure in the fireboxes into which fresh air was drawn. When a smokestack was perforated or shot away, as often happened, the draft to the engine was reduced and the ship lost power. Several classes of vessels had bands of armor on the stack to guard against this, and the Canonicus class of monitors had a telescoping stack that could be drawn down behind an armored section during combat.

The main engines were frequently not the only engines on board. Most ships carried a smaller engine (known as a "doctor") for use in various auxiliary functions including winding winches, pumping water, etc. Monitors, of course, had auxiliary engines to turn their turrets. All of these subsidiary engines ran off steam provided by the main boilers.

Control Systems

Control systems, in marked contrast to the technological advancement of other onboard systems, had changed little by the time of the Civil War. Steering was still accomplished by a wheel and transmitted via tiller ropes and tackles to the rudder, as it had been for centuries. The protection of these tiller ropes (also called wheel-ropes and steering chains) was a matter of importance in warship design, as damage to them would quickly put the ship out of action. The Louisville had her tiller ropes shot away at Fort Donelson and drifted away down the river, out of control. The Tennessee's steering chains were for some indecipherable reason left exposed in grooves on the afterdeck, covered only by a thin sheet of boiler iron, and they were soon shot away by the Chickasaw, leaving her unmanageable.

Communication between the pilot and the engine room was still accomplished by means of bells and speaking tubes (hollow pipes that were shouted into), or if these broke down or if the captain wanted to send a message anywhere else, someone had to be pressed into service as a runner. Signalling was accomplished by use of flags (in daytime) and lanterns and rockets (by night). Occasionally, Army signal personnel were pressed into service aboard ship, particularly in the case of the riverine squadrons, but also by Farragut at Mobile Bay, to communicate between ships by sempahore code.

Fire direction was still at the behest of the officers commanding the guns; centralized fire direction would have to await further developments in intraship communication.

Design and Construction Hull Forms

The hulls of the ironclads fell into four broad categories: conventional, riverboat (scow), monitor, and casemate.

Conventional hulls were found (naturally) on all of the converted coastal ironclads, as well as the Galena, New Ironsides, and Dunderberg. Modified conventional hull forms could also be found on the Onondaga and Keokuk. They had a keel, a round bottom, and generally a single screw and rudder located at the sternpost.

From the earliest days of steam, riverboats were constructed differently. Since they were not driven by the wind and operated in calm waters, there was no great need for a keel except for structural strength. However, there was a great need for the shallowest possible draft with the greatest possible load, so they were generally flat-bottomed, with a much greater beam-to-length ratio than could be found on seagoing craft. Some riverboats were catamaran (that is, two smaller hulls side by side with a space between them); the Benton was converted from such a vessel.

Monitor hulls were of an entirely different concept of construction. Reportedly, John Ericsson had been impressed by the stability of lumber rafts in his native Sweden, and attempted to adapt this for a warship design. The Monitor was described by him as having two distinct hulls, the upper raft-like hull for stability and protection, and the lower hull beneath it to house the engines, crew, and storage areas. The screws and rudders were entirely under the raft, shielding them from all harm except from below. Though a novel and brilliant concept in theory, it had some significant drawbacks in execution, as could be said about many of Ericsson's ideas, such as the insistence on a single turret. It made small allowance for the pounding the flat underside of the raft would take in a moderate to heavy sea, and there was no effective way at the time to connect the upper and lower hulls securely enough to avoid the inevitable weakening of the joints between them in such conditions. It is very possible that this flaw was directly responsible for the loss of the Monitor off Cape Hatteras. In successive monitor classes, the overhang was gradually reduced (and entirely absent in non-Ericsson designs), until when work on the Kalamazoo class was begun, it had all but completely vanished.

Southern casemate ironclads had hulls bearing strong resemblances to both the riverboat hulls and monitor hulls. Often flat-bottomed (though usually with a keel) and with extremely simple cross-sections composed mostly of straight lines, they could be constructed by semiskilled labor in remote locations. The designs of the Tift brothers, Nelson and Asa, were consciously intended to be constructed by housebuilders with no shipbuilding experience, a valuable advantage for the South, which had an extreme lack of shipwrights and construction facilities. The similarity to the monitor hulls arose from the "knuckle," the angular transition from the sloping casemate to the hull. A natural consequence of the inclined casemate, it conferred the stability and protection advantages of the monitor raft without the corresponding weakness.

Mass Production

The economic and social impact of the cotton gin often overshadows Eli Whitney's more important development, the mass production of identical components to speed production and repair of whole items (credit for this is usually given erroneously to Henry Ford, whose contribution was in fact the assembly line). Mass production was much easier in the North than in the underindustrialized South, and reached its naval pinnacle in the production of large classes of identical ironclads. This made possible the retrofitting of additional gear to entire classes, such as when an outer armored "sleeve" was added to the Passaic class monitors' pilothouses at Charleston. This would have been impossible had the pilothouses been built singly with varying dimensions. As another example, when the Weehawken developed engine problems, it was repaired with parts from the Camanche, also engined by Secor; since the Camanche had been earmarked for the peaceful West Coast, it was attributed a lower priority than the ironclads massing for the Charleston attack.

Mass production enabled the North to pit its strengths (industry and skilled labor) directly against the South's corresponding weaknesses. As industrial strategy goes, it was an invincible setup. The resulting network of contractors and subcontractors presaged the modern military-industrial complex.

Low-Tech Production

Where extensive shipbuilding facilities and skilled labor were not available, lower-technology means had to be employed to build ironclads. This was not limited to the Confederacy; it was also frequently the case with the Union riverine fleet.

The Tift designs, as mentioned, were prime examples. The construction of ironclads by Gilbert Elliott in the North Carolina sounds als serve to illustrate low-tech construction. The vessels were entirely built of wood, using local materials and labor, and the iron was added afterward as it became available. The iron-poor South was forced into this scheme. Elliott's constructions depended heavily on securing enough railroad iron for conversion into plate.

Shipyards sprung up in the most unlikely places, such as Shreveport LA, Oven Bluff AL, Columbus GA, and Yazoo City MS. However, the very remoteness of these sites greatly hampered production, and not just because of lack of transportation. The Oven Bluff facilities, for example, were severely affected by disease. Of these remote sites, only Shreveport and Columbus successfully completed ironclads, but only one from each, and these (Missouri and Jackson) never saw action.

The Union riverine fleet was under similar constraints, though the extensive railroad and telegraph networks of the North largely negated the disadvantages. Shipyards sprung up in such places as St. Louis and Cincinnati, where there were a number of workmen skilled in the construction of riverboats. The Western flotilla had to deal with the same problems that handicapped the South-- often, men or material had been earmarked for the Army and it was a difficult task to secure resources for the Navy.

Conversions and New Construction

Several ironclads, North and South, were converted from existing vessels rather than built from the keel up. (Northern coversions were the Roanoke, Essex, Benton, Choctaw, Lafayette, and Eastport; Southern conversions were the Virginia, Atlanta, Baltic, Manassas, Mobile, and Republic.) Conversion appeared to present several advantages againse new construction: there was no need to start from scratch if a suitable hull could be found, the ship had probably been built of prewar seasoned timber stocks, and the machinery would already be in place. However, the majority of these ships were lacking in motive power, since their engines had not been designed to propel the extra weight that the guns and armor represented, and the strength of the hull was often inadequate (especially in the cases of Roanoke and Eastport). The best of this rather ill-starred lot were the Benton and Atlanta. The Benton had been a powerful wrecking boat before the war and its coversion had been carefully planned, though it was always very slow; the Atlanta was converted from the British-built iron-hulled blockade runner Fingal and was one of the best-built Southern ironclads. Though it was captured by the Weehawken in a single battle, its obvious merits were perceived by the North, and it was quickly pressed into service in the Union navy.

New construction was the rule rather than the exception on both sides, and this is hardly surprising given the relatively small number of ships suitable for conversion. Some standardization of design and construction was attained, particularly in the North with its large classes of virtually identical ironclads, but the South also promoted standard designs, such as the "150' type" and the "Albemarle (diamond-hulled) type."

In many records, the mistake has been made that ships of the "150' type" were 150' in length, which is incorrect. The 150' figure is between perpendiculars, or "bp," the length from the break of the bow to the axis of the rudder post. For instance, the Richmond was the prototype of the 150' class of vessels, yet its length overall ("oa") was 188'. This sort of confusion is to be expected with regard to Southern vessels, since many in the South were unfamiliar with naval architecture and many records have been lost.

It has been the practice of some to collect Southern ironclads into "classes," but this may be more of a hindrance than a help. Though many were certainly built to a few standardized designs, in reality the locak shipbuilder had a very high degree of control over the actual dimensions and deatures of the vessel, and some very different ships were the result.


The ironclads of the American Civil War present a fascinating image of naval technology in the midst of transition between the old days of the wooden men-of-war and the modern navies of the late 19th and early 20th centuries. They stand at the divide between sail and steam, between wood and armor, and between old rule-of-thumb design and modern drafting and planning. In this respect, the many less-than-successful vessels accquire an even greater interest, perhaps, than those that were more fortunate. The great degree of invention and improvisation in their designs elicit an interest that is often lacking in what came before and after. In any case, the story of these vessels is vitally important to a full understanding of the evolution of the warship.

Copyright © 1998 Mark F. Jenkins.

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