It's likely that Grantville's machinists have heard of autofrettage. However, the autofrettage pressure must be much higher than the working pressure, which, for a cannon, is very high already. Autofrettage is typically used when pressures exceed 15,000 psi for brief periods of time, and so you must be able to achieve a higher pressure hydraulically.
Canon. In canon, the ironclad's main guns use Schedule 160 12" pipe as liners, wrapped with steel wire salvaged from the coal mine. (1633 Chap. 4). That, of course, is heavily dependent on twentieth-century materials. Should steel wire become unavailable, the backup plan is to cast bronze reinforcements around the tubes. I imagine that if there were no steel tubes, they would use cast iron.
Quality Control
A newly-cast gun barrel might have cracks and cavities (Hoskins 42). Before a gun was accepted (and paid for) by the military, it was tested. The British proofed guns by loading them with a double charge, and setting it off. The gun was then examined for cracks; this included filling it with water to see if it leaked. (Lavery 84). The gun would also be examined, usually visually, for the correctness of the bore diameter and the trueness of the bore. Note that if the bore droops, or bows to the side, this will impede the escape of the ball, and thus increase the pressure that the barrel must withstand (Hoskins 65).
Flaws may develop (or worsen) as a result of use (or misuse). Firing the gun too rapidly so that it overheats, overcharging the gun, and ramming the gun too hard all can create problems. Bronze has the great advantage that it tends to "crack and bulge before it bursts," unlike iron. (Id.).
Now let's discuss the Gribeauval system, which gave the French the best artillery in late-eighteenth-century Europe. Much attention was given to tightening the manufacturing tolerances for both the bore and for the cannon balls it fired. Rather than merely judge by eye whether the bore was dimensionally correct, the Gribeauvalist inspectors used a caliper gauge to measure the diameter to within 0.025 mm. (Alder 150).
In canon, Grantville's machine shops quickly demonstrated that they could do even better. Early in the new time line, Ollie Reardon manufactures new three-pounder cannon for Gustav Adolf. The metal is soft bronze, in which he drills out the bore on a lathe. He notes that ideally the finish cut would be with a reamer. (Flint, 1632, chapter 46). Whether reamed or not, the final product impresses Torstensson, Gustav's Chief of Artillery: "Those bores are perfectly identical!" In response, Rebecca shows him a micrometer, and explains that it has an accuracy of 1/1000th of an inch (one mil). (chapter 47).
Gun Popularity
Table 1–3 shows that even in Elizabethan times, there was a trend toward heavier armament:
I don't have a bronze vs. iron breakdown for 1585, but in 1592, naval guns were 79 % bronze. (Walton 220). Thus, there was also a trend toward replacing bronze with cast iron.
This information is still relevant as of RoF; both ships and guns typically remained in service for several decades. The British warships in active service in 1631 included the British Bear (40 guns, 1580), Adventure (26 guns, 1594), Warspite (32, 1596), Nonsuch (32, 1605), and Assurance (34, 1605). As for guns, on the Portuguese Santissimo Sacramento (launched probably in 1653; sunk 1668), the bronze guns are dated, either explicitly by the caster, or implicitly by design. Nine were cast before 1600. Eleven, between 1600 and 1650. Five were just identified as mid-1600s, and one was 1653. (Guilmartin). On the Kronan (sank 1676), one gun was cast in 1514 (Hoskins 18).
It would of course be nice to have comprehensive data for a date closer to the RoF (1631). I have found the Royal Ordinance Inventory for 1637 (Collins), but that's for the army. While the Royal Ordinance also supplied the navy, the latter would have requisitioned a different assortment.
What I can provide is data for individual ships; table 1–4 attempts to correct the usual British bias by providing some French, Danish, Swedish and Dutch examples.
By way of comparison, the principal Napoleonic battleship, the "74", usually had 28x32pdr, 28x18pdr, 18x9pdr. (Lavery 121).
In the table, I introduce the metric "broadside weight," the total weight of shot that can be fired at one time. This is probably a better measure of the power of a warship than just the nominal number of guns.
From a ship design standpoint, another important metric is the ratio of that broadside weight (pounds) to the ship displacement (tonnes); for the Swedish navy, it was around 0.4 in the 1630s, but increased to 0.75 in 1671. (Glete 571). In that year, the Kronan carried an armament of about 180 tonnes, 8 % of its 2,300 tonne displacement. (572).
Horizontal Distribution of Guns
We may recognize three basic gun arrangements: predominantly frontal; predominantly broadside; and turreted. The Mediterranean galleys are in the first category. One of the more powerful of the Venetian galleys at Lepanto (1571) might have a 52–55 pound full cannon, flanked by an inner pair of 12-pounders and an outer pair of 6-pounders. And it could have a second deck, carrying swivel guns, as was certainly the case for the larger Spanish galleys. (Guilmartin, 322-3). In the eighteenth and nineteenth centuries one could also find heavy frontal armament in certain specialized warships, bomb ketches and rocket ships. In the twentieth century, we have a similar arrangement on torpedo boats and missile boats. And attack submarines may be said to have a spinal armament, firing torpedoes from bow or stern.
Most warships of the late-sixteenth through mid-nineteenth centuries were designed to deliver powerful broadsides, but had rather weak bow and stern armament. Once the "line ahead" formation and related tactics, which lent themselves to delivering broadsides, were developed in the mid-seventeenth century, this was particularly true of capital ships. A frigate or lesser vessel was more likely to have chase guns.
Despite the importance of the broadside, seventeenth-century French warships tended to have relatively powerful bow and stern armament, because they were used in the Mediterranean against galleys. This required some adjustment in the hull to provide a good firing arc. (Langstrom 167). In general, since the number of bow and stern guns was limited by space, those tended to be the ones with the best range and accuracy. (ChapelleHASN 12).
It's perhaps worth noting that warship designers of the second half of the nineteenth century were "ram-crazy"; this in turn led to an undue emphasis on frontal firepower for steam-powered ironclads.
For a ship with broadside armament, the length determines how many guns it can carry per deck. Length was limited by structural concerns; local inequalities of weight and buoyancy would cause it to droop in the center (hogging) or sometimes at the ends (sagging). These in turn imposed strains on the hull; they were proportional to the square of the length. Wooden-hulled warships consequently weren't much longer than 200 feet; a British first rate of the 1745 Establishment was 179 feet at the gun deck. (Ireland 41).
Of course, the number of guns carried on a deck of particular length depended on the spacing between the gunports, and how close they came to the bow or stern. On the Dauphin Royal (1735), 74 guns, there were 13 ports to a side, the foremost about 18 feet from the stem and the aftmost about 10 feet from the stern. The port width was 2'10" and the distance between ports (edge-edge) was 7'7". (du Monceau 4).
Gunport spacing was limited by the area and crew needed to work the guns; the more powerful the gun, the greater these were. Gunport breadth, for example, was 3 feet for a 48-pdr and 1.5 for at 4-pdr (Id). The spacing was also affected by the framing; you didn't want to cut through a frame and weaken the hull. A mid-seventeenth-century Dutch admiralty had these rules of thumb: gunport spacing (center-center) 20 shot diameters; height, six diameters; width, five (Hoving 104). A mid-eighteenth-century rule allows for 25 shot diameter spacing and 6.5 diameter width, with the sill 3.5 diameters above the deck (Davis1984,110).
In the British 1745 establishment, no warship had more than 28 guns on a single full deck. However, there were post-establishment British warships, such as the First Rate Victory (1765) and the "Large" class 74s, with 30 guns on the lowest gun deck (Lavery 121
ff). And in 1764, du Monceau, said that a 112-gun French warship had 32 guns (24-pdr) on its second deck.
If you wanted more guns than a single full deck could accommodate, you put them on the quarterdeck or forecastle, or, if that still wasn't enough, you added a second (or if need be a third) full deck.
The mid-nineteenth-century introduction of iron and steel construction allowed warships to be lengthened, and thus history has some examples of some long "broadside ironclads." The longest of these was the HMS Minotaur (1863), 407 feet long, a sail/steam hybrid. There were also two-decker broadside ironclads, such as the French Magenta (1862), 282 feet long. (Neilson).
Broadside guns had a limited firing arc. In Napoleonic warships, the range of traversal was 40–45 degrees before or abaft the beam; this was apparently an improvement on earlier warships (O'Neill 71). However, in steam ironclads like HMS Warrior, the gunports were narrowed, thereby reducing the arc of fire (Lambert 46). The theory was that with steam propulsion, they weren't subject to the vagaries of the wind, and therefore could maneuver as needed to bring the guns to bear. Moreover, firing at extreme angles reduced the rate of fire. I also figure that the narrower gunports meant that the guns were less vulnerable to counterfire.
I believe the first turret ship was the wooden Royal Sovereign (1857); Eriksson's ironclad USS Monitor (1862) was the first to engage in battle. The advantage of the turret was that by rotation it could bring its gun(s) to bear in any direction, save for those obstructed by the ship's superstructure (including funnels, masts, and other turrets). Because of the size and expense of the turret, the tendency was for turreted warships to be fitted with a small number of very powerful guns. For this discussion "turreted" may mean a true turret (armor rotates) or a barbette (armor stationary).
Sails, masts, spars and stays would of course restrict the firing arcs; nonetheless, many early turreted warships were hybrids (sail/steam) because of doubts as to the reliability of the engine.
This led to a variety of curious expedients. On the ill-fated HMS Captain (1869), the two turrets were on the lower (main) deck, and the masts were stayed to the upper (hurricane) deck. I would imagine that this arrangement would limit how high the guns could be elevated. The hurricane deck was dispensed with on the double-turreted HMS Wyvern and HMS Scorpion (1863), on which the turrets flanked the main mast. Captain Coles proposed use of iron shrouds and stays. (Breyer 34).
HMS Devastation (1871) was the first turreted warship without rigging (it had a central mast for signaling and observation). HMS Inflexible (1876) had two screws driven by compound steam engines, and two masts that could carry 18,500 sf sail (Wikipedia). The latter was removed in 1885. (Breyer). While I am not aware of later turreted warships with sails, the broadside-armed HMS Calypso (1883) was ship-rigged (Ireland1997, 36) and the Russian cruiser Rurik (1892), barque-rigged.
Early turreted warships included those with one (USS Monitor), two (USS Onondaga) and even three (USS Roanoke) turrets. With multiple turret designs, one has the concern of where to place the turrets. The most obvious arrangement was to place them single file on the centerline. The obvious problem was that a bow turret couldn't fire directly astern, and a central turret (as on the HMS Monarch (1868)) couldn't safely shoot fore or aft.
One alternative was to mount the extra turrets on the side (wings). This increased the frontal fire at the expense of broadside fire. In theory, wing turrets could be staggered, and fire if need be across the deck. but that tended not to be too good for the deck. And the centerline design was structurally sounder.
Another option was to stack the turrets, like the tiers on a wedding cake. On USS Kearsarge (1898), the double-decker turrets turned as a unit. It's reported that the vibration of the 13" guns below interfered with the firing of the 8" guns above. (cityofart.net)
The 1870s Italian navy experimented with a "diagonal reduit", in which two turrets were mounted near the center of the ship but diagonally offset from it. (Breyer 33).
A single turret could carry one, two or even three guns, but if it attempted to fire multiple guns simultaneously, "invariably, one of the guns was thrown off target by the firing of the first weapon." (Kaufmann 5).
With muzzle loaders, the turrets had to be of large diameter, but the guns short-barreled, so they could be run back and reloaded inside. (Ireland1997, 38).
The mechanisms of turret gun laying and loading are discussed in part 2, and the armoring of turrets in part 5.
Vertical Arrangement of Guns
Positioning the gun on a higher deck has the advantage that the gunports are less likely to be forced to close as a result of rough sea conditions (Laing 76). Raleigh urged that the ship be designed and laden so that the lowest tier of ordnance was four feet above the water (Creuze 17). An upper deck gun will also have increased range (as predicted by Torricelli) and can take advantage of plunging fire (shooting at the flimsy enemy deck, not the relatively stout side). However, if the enemy is close at hand, the gun might not be able to depress enough to fire upon it, and the higher the guns are, the higher the ship's center of gravity must be, reducing its initial lateral stability (but the higher freeboard does provide some compensation by increasing the angle of vanishing stability).
In the fifteenth century, ships had guns mounted high up, in the aptly named forecastles and sterncastles. The size and number of these guns was limited by their effect on stability. In the early-sixteenth century, gundecks and gunports were introduced. Since the armament was lower, it could be made heavier. (Svensson 16). As broadsides became more effective, the superstructures became less useful and were reduced in size. The early-seventeenth century was a transitional stage in which the capital ships mounted heavy broadside armaments, but still had significant superstructures.
The depth (and draft!) of the ship limits the number of gun decks. Over the course of the sixteenth century, a second and then a third gundeck (~1591) was introduced. (Creuze 15). The Dutch didn't use three-deckers, but the English and French did. (Anderson 158). British designers of the late-eighteenth century found that three-deck 80-gun ships were top heavy; two-deck 80s were too long for their height, and hogged (drooped amidships); the two-deck 74s were ideal and, even though they were considered to be of the "third rate," became the most common "battleships" in "foreign service." (Millar 9).
On a Georgian frigate, the lower deck was called the gun deck but had no guns (Millar 10). But that did help ensure that the upper deck was safely above the water.
For the British navy, there was no systematic distribution of the different gun sizes among ships of different classes, and among the different decks of a given ship, until 1677, when it adopted a "solemn, universal, and unalterable adjustment of the gunning and manning of the whole fleet." (Tanner 233ff). This was altered (snicker) by the "establishments" of 1691, 1706, 1719, and 1745. After that warship design became somewhat more diverse again.
Gun Weight
After armor was introduced in the nineteenth century, warship design became "weight critical"-the hull displacement provided a particular amount of buoyancy, and the ship couldn't be heavier, so designers had to make compromises vis-a-vis weight of guns, engines, armor, and even fuel and ammunition carried.
As a loose rule of thumb, gun weight is proportional to the cube of the caliber (Meigs 204) and thus, for roundshot, proportional to the shot weight. For early-nineteenth-century British iron guns, gun weight was 170–411 times the latter. (Beauchant 102). Big guns have greater range, but small guns have a higher rate of fire.
We have already alluded to the fact that bronze guns could be made lighter than cast iron ones of the same caliber; steel guns had a similar advantage over their predecessors, because of steel's greater tensile strength per unit weight.
Guns designed to only fire shells (hollow projectiles) could be lighter than those firing solid shot; shells were lighter than solid shot of the same caliber; hence less powder was needed to project them; hence the gun barrels could be thinner. Or, keeping
gun weight the same, you could increase caliber. The Paixhans 80-pounder shell gun (1837) weighed the same as the traditional 36-pounder. (Tucker 1320).
Gun Crew
There's some data on crew size in Table 2A. In early nineteenth century French naval service, 14 men attended a 36-pounder; 12, a 24-pounder, 10, an 18- or 12- pounder, 8, an 8-pounder; and 6, a 6- or 4-pounder. (Douglas 149). A carronade only needed 4 men. (163).
Miller (57) provides the rule of thumb that one man was required for every 5 cwt. (112 pounds) of gun weight, although I think that's on the low side. However, he makes the point that gun crews changed constantly; if only one side were engaged, the free crews would come over to help; but crewmen would also be pulled off to handle the ship or to form a boarding party.
Gun Loading; Rate of Fire
It's dangerous to assume that the rate of fire was as good in the 1630s as in the more familiar Napoleonic period (Hornblower Syndrome!).
A modern crew of four handling a replica sixteenth-century wrought iron breechloader required 5 -10 minutes per shot (Konstam 40). An experienced crew might well do better, but on the other hand, handling a large muzzleloader would be more time-consuming. Elizabethan sea dogs probably just fired one broadside at point-blank range and then fought a boarding action. (Konstam 40).
"In 1646 Master gunner William Eldred stated, in The Gunner's Glasse that a maximum of ten rounds an hour could be fired from a gun, and that after forty shots had been fired an interval of an hour must be allowed to cool the piece." (Hughes 35).
Grantville Gazette 45 gg-45 Page 19
