_(14596346858)_The_steam_ram_%2527Dunderberg%2527_(cropped).jpg) The steam ramDunderberg,Harper's Weekly, 1867 | |
| History | |
|---|---|
 United States | |
| Name | Dunderberg |
| Namesake | Swedish: "thunder(ing) mountain" |
| Ordered | 3 July 1862 |
| Builder | William H. Webb,New York City |
| Laid down | by 3 October 1862 |
| Launched | 22 July 1865 |
| Fate | Not accepted by U.S.N. Sold to France by 7 May 1867 |
 France | |
| Name | Rochambeau |
| Namesake | Comte de Rochambeau |
| Acquired | by 7 May 1867 |
| Commissioned | 7 August 1867 |
| Renamed | 7 August 1867 |
| Stricken | 15 April 1872 |
| Fate | Scrapped, 1874 |
| General characteristics (in French service, 1868) | |
| Type | Casemate ironclad |
| Displacement | 7,849 metric tons (7,725 long tons) |
| Length | 107.4 m (352 ft 4 in) (p/p) |
| Beam | 22.15 m (72 ft 8 in) |
| Draft | 6.5 m (21 ft 4 in) (mean) |
| Depth | 7.078 m (23 ft 2.7 in) |
| Installed power | |
| Propulsion | 1 shaft, 2 Horizontalback-acting steam engines |
| Sail plan | Brigantine rig |
| Speed | 14.5knots (26.9 km/h; 16.7 mph) |
| Range | 2,200kilometres (1,200 nmi) at 8 knots (15 km/h; 9.2 mph) |
| Complement | 600 |
| Armament |
|
| Armor |
|
Dunderberg, which is aSwedish word meaning "thunder(ing) mountain",[1] was an ocean-goingcasemate ironclad of 14 guns built for theUnion Navy. She resembled an enlarged, two-masted version of theConfederate casemate ironcladCSS Virginia. She was originally designed to have bothgun turrets and acasemate but the turrets were deleted while the ship was still being built. Construction began in 1862, but progress was slow and she was notlaunched until after the end of theAmerican Civil War in 1865.
The ship was not accepted by the Union Navy so her builder began seeking buyers elsewhere;Otto von Bismarck expressed some interest, and the thought ofPrussia armed with such a vessel prompted France to purchase her andcommission her in 1867 with the nameRochambeau. She was initially placed inreserve, but was mobilized in 1870 to participate in theFranco-Prussian War. The ship saw no action and wasdecommissioned after the end of the war.Rochambeau was stricken from theNavy Directory in 1872 andscrapped in 1874.
On 11 April 1862,William H. Webb, arguably the premier wooden shipbuilder in the country, sent a model of a large wooden-hulled, casemate ironclad with adisplacement of about 7,000 long tons (7,100 t) to theUS Navy Department. Webb signed a contract on 3 July with the Navy'sBureau of Yards and Docks for a ship that had anoverall length of 350 feet (106.7 m), abeam of at least 68 feet (20.7 m) and adraft of no more than 20 feet 6 inches (6.2 m). His ship was required to make 15knots (28 km/h; 17 mph) in still water and she was to be armed with four 15-inch (381 mm)Dahlgren guns in twogun turrets, each protected by 11 inches (279 mm) of armor, and eight 11-inch Dahlgren guns in acasemate. The ship was to be completed in 15 months at a cost of $1,250,000.[2]
Now namedDunderberg by Webb, the contract was amended on 27 August to specify her armor scheme. Above the maindeck, her armor was to be 4.5 inches (114 mm) thick. From the main deck to a depth of 5 feet (1.5 m) below thewaterline, the armor was to be 3.5 inches (89 mm) thick, tapering to 2.5 inches (64 mm) at its lower edge. The ship's main and casemate deck armor was .75 inches (19 mm) thick except at the rear of the ship.[Note 1] The main deck, from the rear of the casemate to the stern, was to consist of 4.5-inch armor plates that tapered to 2.5 inches in thickness.Dunderberg was to be given a completedouble bottom and her engine and boiler rooms were to be completely enclosed by watertightbulkheads. She was also to be provided with twomasts and the appropriate rigging.[3]
The ship was powered by twoback-acting steam engines driving one four-bladedpropeller 21 feet (6.4 m) feet in diameter, using steam generated by six tubularboilers at a working pressure of 25 psi (172 kPa; 2 kgf/cm2).[4] The engines, designed to produce 4,500indicated horsepower (3,400 kW),[5] and boilers were both subcontracted by Webb to theEtna Iron Works of New York City. The engines were originally intended to have abore of 90 inches (2,286 mm) and astroke of 45 inches (1,143 mm), but Webb increased the bore to 100 inches (2,540 mm) to insure thatDunderberg reached her contract speed. During the ship's firstsea trial on 22 February 1867, she reached a speed of about 12.5 knots (23.2 km/h; 14.4 mph); during a demonstration for her French buyers on 12 June,Dunderberg reached 13.9 knots (25.7 km/h; 16.0 mph). She had twoauxiliary boilers to provide steam for the steam engines that powered her pumps, ventilation fans and rotated the gun turrets. These engines, with their bore and stroke of 36 inches (914 mm), were larger than the main engines of thePassaic-classmonitors. All of the boilers exhausted through a retractablefunnel.[4] The ship normally carried 540 long tons (550 t) of coal, but could hold a maximum of 1,000 long tons (1,000 t). She had a lightbrigantine rig[6] that had a sail area of 11,170 square feet (1,038 m2).[7]
Herkeel was laid down before 3 October 1862 at Webb's shipyard in New York City,[Note 2] even though Webb was forced to useunseasoned oak forDunderberg because the supply of seasoned timber had been exhausted earlier in the war. Unseasoned wood was far more prone to rot and significantly shortened the ship's life. Her hull was very strongly built with the space between her frames filled with timber and diagonal iron straps tied her frames together.[9] The sides of the casemate at the level of the main deck were approximately 5 feet (1.5 m) thick.[10] Before beginning construction, Webb redesigned the hull, increasing its length to 358 feet 8 inches (109.3 m) betweenperpendiculars and its overall length to 377 feet 4 inches (115.0 m). Her beam decreased from 75 feet 6 inches (23.0 m) to 72 feet 10 inches (22.2 m) and she displaced, at her nominal draft of 18 feet (5.5 m) forward and 21 feet (6.4 m) aft, 6,948 long tons (7,059 t).[9] These changes made her thelongest wooden ship ever built.[5]Dunderberg's hull was protected frombiofouling by two external layers of zinc and copper. The ship was fitted with two rudders, the primary one in the usual location aft of the propeller, but she also had an auxiliary rudder placed in thedeadwood above and ahead of the propeller.[11]
Many other changes were made toDunderberg while she was under construction and significantly contributed to her delays in completion. The most important of these was the eventual elimination of her turrets[12] which began in October 1863 when Webb wrote toGideon Welles,Secretary of the Navy, saying that he concurred with theGeneral Superintendent of Ironclads,Rear AdmiralFrancis Gregory's suggestion that the "turrets be dispensed with and the casemate lengthened to accommodate an additional number of guns"[13] Welles did not approve the change until September 1864 when he authorized an armament of four 15-inch and twelve 11-inch guns in the casemate. This was extended by 73 feet (22.3 m) to an approximate overall length of 228 feet (69.5 m) so that it now covered the aftmagazine and shell room.[13] It was provided with a total of 22gun ports, six on eachbroadside, two on each corner and one each facing the bow and stern.[6] The design of the gun ports was another issue that took years to resolve. They were originally sized for the 11-inch Dahlgren gun with a height of 42 inches (1,067 mm), but this was inadequate to allow the guns to fully elevate as experience withNew Ironsides proved. The mounting of the much larger 15-inch Dahlgren gun in the casemate further complicated the design of the gun ports, especially since the design for theircarriages was not even finished until May 1866. The design of the gunport itself was revised in the second half of 1865 to reduce the chance of projectiles entering them; the new design was roughly hourglass shaped and narrower in the middle of the casemate than on either the inside or the outside of the gun port. All of these changes to the gun ports delayed the completion of the casemate's woodwork as well as the cutting and installation of the casemate armor. The angle of the casemate was also changed from the original very shallow 35° from the horizontal to an angle of 60° after Rear AdmiralJoseph Smith, Chief of the Bureau of Yards and Docks, noted that it would be very difficult to work the guns at such an angle. The deletion of the turrets also required a redesign of theconning tower as Webb had intended to mount it on top of the fore turret. A copy of that used by theMiantonomoh-class monitors was installed between the funnel and theforemast during August 1866.[14]
Dunderberg was built with a plough-shaped 44-foot (13.4 m),ram bow of which the forward 12 feet (3.7 m) were sheathed incast iron.[10] Her full armament was not installed before she was sold, but gunnery trials were conducted in February 1867 with two 15-inch and four 11-inch guns. With a gun port height of 50 inches (1,270 mm), the 15-inch guns could elevate +8.5° and depress to −5°; equivalent figures for the 11-inch guns were +5° and −7°. The 15-inch guns could traverse 30° forward of the beam and 28° aft and the 11-inch Dahlgrens could bear 28° to both sides. The only significant problem encountered during the trials was that the gun deck was made of soft pine and did not withstand the force of recoil well.[15]
Other problems that delayed the ship's completion were shortages of material, labor and money. Prices forpig iron and bar iron nearly tripled whileboiler plate and copper roughly doubled. Wages of even inexperienced workers increased between 50 and 100 percent. TheNew York City draft riots in July 1863 and severalmachinist'sstrikes further slowed progress onDunderberg. Webb failed to account for these problems when negotiating the ship's contract and he repeatedly tried to charge the Navy for alterations as well as use cheaper materials to reduce his costs. He also attempted to have his contract amended by act of Congress, but he was unsuccessful. The Navy agreed to pay for some of the changes made and it also reduced the reserve amount held back in case theship did not meet her specifications in 1865.[16]
By about 1864, both sides regarded the ship as awhite elephant; Welles wrote in hisdiary that he would rather have the money than the ship and Webb was spending more money than he could anticipate from the contract. Nonetheless, he continued work on theDunderberg as he had very little other work for his shipyard and, most importantly, in the hope of getting his contract amended to allow him to make a profit. On 22 July 1865, helaunched the ship, now with her hull complete and about half of her armor installed, with much fanfare. TheNew York Times estimated a crowd of 20,000 watched the launching. The following year, the government rejected offers by Peru and Chile to purchase the ship, both then atwar with Spain, lest the sale prejudice itslawsuit against Great Britain for selling warships to the Confederacy. Webb did manage to get aprivate bill passed by Congress in March 1867 that allowed him title to the ship once he repaid all monies advanced to him.[17]
After Prussia expressed an interest in the ship, theEmperor of France,Napoleon III, bought her in April for 2.5 million dollars over the objections of his own navy, which preferred a home-built ship.[18] The exact date of purchase is unknown, but Welles noted in his diary on 7 May that Webb had told him of the sale. On 27 June, Webb refunded the money that had been paid to him and also purchased those items furnished by the government. A little over a week later, he attempted to sail to France, but had to return to port the following day due to engine problems. These were not resolved until 19 July when he, and his entire family, set sail.Dunderberg arrived atCherbourg on 3 August and the French Navy took possession three days later.[19]
The ship was commissioned and renamedRochambeau, in honor of theComte de Rochambeau, a general during theAmerican Revolution,[20] on 7 August. After briefly running machinery trials two days later, Rochambeau began anoverhaul in the naval dockyard at Cherbourg to fix problems that had become apparent during her delivery voyage and to modify her in accordance with French practices. These changes included the addition of apilothouse on top of the conning tower, the replacement of the main rudder and the length of her stern was reduced somewhat. Her armament was removed and replaced by fourCanon de 270 Modèle 1864/66 and 10Canon de 24 C modèle 1864 (9.4 in) guns, both of which werebreech-loading. The 15-caliber 270-millimeter (10.6 in) guns fired a 216-kilogram (476 lb) shell while the 17-caliber 240-millimeter (9.4 in) guns fired one that weighed 144 kilograms (317 lb). The 270 mm guns were mounted in the corners of the casemate and could pivot between a broadside gun port and one on the corner. Eight of the 240 mm guns were mounted on the broadside and the remaining two were positioned in the bow and stern gun ports. The remaining four gunports, those on the corners closest to the broadside, were plated over.[21]
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The French carefully measured the ship during her 1868 overhaul. At the waterlineRochambeau was 107.4 meters (352 ft 4 in) long and had a beam of 22.15 meters (72 ft 8 in). She had a mean draft of 6.5 meters (21 ft 4 in), adepth of hold of 7.078 meters (23 ft 2.7 in), and displaced 7,849 metric tons (7,725 long tons). They rated her engines at only 4,000metric horsepower (2,900 kW), but they produced a maximum of 4,657 metric horsepower (3,425 kW) and gave a speed just over 15 knots during her machinery trials in June 1868 after the completion of her overhaul. At normal load she carried 540 tonnes (530 long tons) of coal and 735 tonnes (723 long tons) at deep load. In service the ship proved to burn a lot of coal, full bunkers and 30 tonnes (30 long tons) stored on deck provided her a range of only 2,200 kilometres (1,200 nmi) at a speed of 8 knots (15 km/h; 9.2 mph). They reduced her sail area to 954.42 square meters (10,273.3 sq ft).[22]
They measured the ship's armor thickness throughout. The casemate was completely protected by 120-millimeter (4.7 in) plates. The hull armor extended to a depth of 2.5 meters (8.2 ft) below the waterline and its upperstrake was 90 millimeters (3.5 in) thick while the lower was 70 millimeters (2.8 in) thick. Her decks were covered by 18-millimeter (0.7 in) plates and the sides of the conning tower were 250 millimeters (9.8 in) thick. In service,Rochambeau proved to be very wet and threw up a lot of spray in ahead sea. She had a very quick roll which caused problems when trying to work the guns in heavy weather as even moderate seas could prevent their use altogether since the gun ports were only about 1.4 meters (4 ft 7 in) above the waterline. Under sail alone in a good breeze, the ship could not maintain her course, could not be steered and would turn until wind and wave were on her beam.[23]
Rochambeau completed her refit on 18 May 1868 and was briefly under the command ofCaptain (Capitaine de vaisseau)Jules-François-Émile Krantz (a futureMinister of Marine) before being decommissioned on 1 August and placed in reserve. She was refitted from August to December and had her forward hull armor plates replaced by a one-piece cast iron ram. Still in reserve in 1869,Rochambeau was modified with an additional 240 mmpivot gun mounted over the forward end of the casemate and the pine planking underneath the guns in the casemate was replaced by oak.[24]
The ship was recommissioned with a crew of 600 men in mid-July 1870, just before the beginning of the Franco-Prussian War. She departed Cherbourg on 25 August to join the fleet in Danish waters and reachedCopenhagen on 31 August. The fleet fruitlessly cruised theBaltic Sea for several weeks before they were ordered home on 16 September.Rochambeau's shallow draft meant that she and the armoredcorvetteThétis were ordered to search the mouth of theJade Estuary on 26 September for Prussian ships, but they found nothing.[25]
Upon her return,Rochambeau was decommissioned again and her crew was ordered to help defend Paris. The ship was stricken from the Navy List (Liste de la Flotte) on 15 April 1872 and was scrapped sometime in 1874.[26]
