View source for USS Dunderberg

{{Short description|Ironclad ship}}
{{good article}}
{{Use dmy dates|date=March 2022}}
{{Infobox ship
|section1={{Infobox ship/image
 |image=Harper's weekly (1867) (14596346858) The steam ram 'Dunderberg' (cropped).jpg
 |image_caption=The steam ram ''Dunderberg'', [[Harper's Weekly]], 1867
 }}

|section2={{Infobox ship/career
 |hide_header=
 |country=United States
 |flag={{USN flag|1865}}
 |name=''Dunderberg''
 |namesake=[[Swedish language|Swedish]]: "thunder(ing) mountain"
 |ordered=3 July 1862 
 |builder=[[William Henry Webb|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
 }}

|section3={{Infobox ship/career
 |hide_header=title
 |country=France
 |flag={{shipboxflag|France|naval}}
 |name=''Rochambeau''
 |namesake=[[Jean-Baptiste Donatien de Vimeur, comte de Rochambeau|Comte de Rochambeau]]
 |acquired=by 7 May 1867
 |commissioned=7 August 1867
 |renamed=7 August 1867
 |struck=15 April 1872
 |fate=Scrapped, 1874
 |notes=
 }}

|section4={{Infobox ship/characteristics
 |hide_header=
 |header_caption=(in French service, 1868)
 |type=[[Casemate ironclad]] 
 |displacement={{convert|7849|t|LT|sp=us}}
 |length={{convert|107.4|m|ftin|abbr=on}} ([[Length between perpendiculars|p/p]])
 |beam={{convert|22.15|m|ftin|abbr=on}}
 |depth={{convert|7.078|m|ftin|abbr=on}}
 |draft={{convert|6.5|m|ftin|abbr=on}} (mean)
 |power=*{{convert|4000|PS|lk=in|abbr=on}}
        *6 Tubular [[boiler (steam generator)|boiler]]s
 |propulsion=1 shaft, 2 Horizontal [[Marine steam engine#Back acting|back-acting steam engines]]
 |speed={{convert|14.5|kn|lk=in}}
 |range={{convert|2200|km|nmi|lk=in}} at {{convert|8|kn}}
 |sail_plan=[[Brigantine]] rig 
 |complement=600
 |armament=*4 × 1 – {{convert|274|mm|in|abbr=on}} Mle 1864/66 guns
           *10 × 1 – [[Canon de 24 C modèle 1864]] (9.4 in) guns
 |armor=*[[Belt armor|Waterline belt]]: {{convert|90|-|70|mm|in|abbr=on|1}}
        *[[Deck (ship)|Deck]]: {{convert|18|mm|in|abbr=on|1}}
        *[[Casemate]]: {{convert|120|mm|in|abbr=on|1}}
        *[[Conning tower]]: {{convert|250|mm|in|abbr=on|1}}

 }}
}}
'''''Dunderberg''''', which is a [[Swedish language|Swedish]] word meaning "thunder(ing) mountain",<ref>{{cite DANFS | title = Dunderberg | url =https://www.history.navy.mil/research/histories/ship-histories/danfs/d/dunderberg.html | access-date =1 January 2013}}</ref> was an ocean-going [[casemate ironclad]] of 14 guns built for the [[Union Navy]]. She resembled an enlarged, two-[[mast (sailing)|masted]] version of the [[Confederate States of America|Confederate]] casemate ironclad {{ship|CSS|Virginia}}. She was originally designed to have both [[gun turret]]s and a [[casemate]] but the turrets were deleted while the ship was still being built. Construction began in 1862, but progress was slow and she was not [[ship naming and launching|launched]] until after the end of the [[American 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 of [[Prussia]] armed with such a vessel prompted France to purchase her and [[ship commissioning|commission]] her in 1867 with the name '''''Rochambeau'''''. She was initially placed in [[Reserve fleet|reserve]], but was mobilized in 1870 to participate in the [[Franco-Prussian War]]. The ship saw no action and was [[Ship commissioning|decommissioned]] after the end of the war. ''Rochambeau'' was stricken from the [[Navy Directory]] in 1872 and [[ship breaking|scrapped]] in 1874.

==Design, description and construction==
On 11 April 1862, [[William Henry Webb|William H. Webb]], arguably the premier wooden shipbuilder in the country, sent a model of a large wooden-hulled, casemate ironclad with a [[displacement (ship)|displacement]] of about {{convert|7000|LT|t}} to the [[US Navy Department]]. Webb signed a contract on 3 July with the Navy's [[Bureau of Yards and Docks]] for a ship that had an [[length overall|overall length]] of {{convert|350|ft|m|1}}, a [[Beam (nautical)|beam]] of at least {{convert|68|ft|m|1}} and a [[Draft (hull)|draft]] of no more than {{convert|20|ft|6|in|m|1}}. His ship was required to make {{convert|15|kn|lk=in}} in still water and she was to be armed with four {{convert|15|in|mm|adj=on|0}} [[Dahlgren gun]]s in two [[gun turret]]s, each protected by {{convert|11|in|mm|0}} of armor, and eight 11-inch Dahlgren guns in a [[casemate]]. The ship was to be completed in 15 months at a cost of $1,250,000.<ref>Roberts, William, p. 364</ref>

Now named ''Dunderberg'' by Webb, the contract was amended on 27 August to specify her armor scheme. Above the main [[deck (ship)|deck]], her armor was to be {{convert|4.5|in|mm|0}} thick. From the main deck to a depth of {{convert|5|ft|m|1}} below the [[waterline]], the armor was to be {{convert|3.5|in|mm|0}} thick, tapering to {{convert|2.5|in|mm|0}} at its lower edge. The ship's main and casemate deck armor was {{convert|.75|in|mm|0}} thick except at the rear of the ship.{{#tag:ref|The rationale for the thicker aft deck armor is not given, but it appears to be intended to protect the machinery spaces that were vulnerable to a plunging shell fired from the rear.<ref name=rw65/>|group=Note}} 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 complete [[double bottom]] and her engine and boiler rooms were to be completely enclosed by watertight [[bulkhead (partition)|bulkhead]]s. She was also to be provided with two [[mast (sailing)|mast]]s and the appropriate rigging.<ref name=rw65>Roberts, William, p. 365</ref>

The ship was powered by two [[Marine steam engine#Back acting|back-acting steam engines]] driving one four-bladed [[propeller]] {{convert|21|ft|m|1}} feet in diameter, using steam generated by six tubular [[boiler (steam generator)|boiler]]s at a working pressure of {{convert|25|psi|kPa kg/cm2|0|abbr=on|lk=on}}.<ref name=rw81/> The engines, designed to produce {{convert|4500|ihp|lk=in}},<ref name=s2/> and boilers were both subcontracted by Webb to the [[Etna Iron Works]] of New York City. The engines were originally intended to have a [[bore (engine)|bore]] of {{convert|90|in|mm|0}} and a [[stroke (engine)|stroke]] of {{convert|45|in|mm|0}}, but Webb increased the bore to {{convert|100|in|mm|0}} to insure that ''Dunderberg'' reached her contract speed. During the ship's first [[sea trial]] on 22 February 1867, she reached a speed of about {{convert|12.5|kn}}; during a demonstration for her French buyers on 12 June, ''Dunderberg'' reached {{convert|13.9|kn}}. She had two [[auxiliary boiler]]s 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 {{convert|36|in|mm|0}}, were larger than the main engines of the {{sclass|Passaic|monitor|3|warship}}s. All of the boilers exhausted through a retractable [[funnel (ship)|funnel]].<ref name=rw81>Roberts, William, pp. 368, 371</ref> The ship normally carried {{convert|540|LT|t}} of coal, but could hold a maximum of {{convert|1000|LT|t}}. She had a light [[brigantine]] rig<ref name=ck9>Chesneau & Kolesnik, p. 119</ref> that had a sail area of {{convert|11170|sqft}}.<ref name=rw7>Roberts, William, p. 377</ref>

Her [[keel]] was laid down before 3 October 1862 at Webb's shipyard in New York City,{{#tag:ref|The exact date is not known, but references in Webb's letters place it between 23 September and 3 October.<ref>Roberts, William, p. 370</ref>|group=Note}} even though Webb was forced to use [[Wood drying|unseasoned oak]] for ''Dunderberg'' 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.<ref name=rw50/> The sides of the casemate at the level of the main deck were approximately {{convert|5|ft|m|1}} thick.<ref name=c7/> Before beginning construction, Webb redesigned the hull, increasing its length to {{convert|358|ft|8|in|m|1}} between [[Length between perpendiculars|perpendiculars]] and its overall length to {{convert|377|ft|4|in|m|1}}. Her beam decreased from {{convert|75|ft|6|in|m|1}} to {{convert|72|ft|10|in|m|1}} and she displaced, at her nominal draft of {{convert|18|ft|m|1}} forward and {{convert|21|ft|m|1}} aft, {{convert|6948|LT|t}}.<ref name=rw50>Roberts, William, pp. 365, 380</ref> These changes made her the [[Largest wooden ships|longest wooden ship]] ever built.<ref name=s2>Silverstone 1989, p. 12</ref> ''Dunderberg''{{'}}s hull was protected from [[biofouling]] 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 the [[deadwood (shipbuilding)|deadwood]] above and ahead of the propeller.<ref>Roberts, William, pp. 368, 377</ref>

Many other changes were made to ''Dunderberg'' 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<ref>Roberts, William, p. 362</ref> which began in October 1863 when Webb wrote to [[Gideon Welles]], [[Secretary of the Navy]], saying that he concurred with the [[General Superintendent of Ironclads]], [[Rear Admiral (United States)|Rear Admiral]] [[Francis Gregory (naval officer)|Francis Gregory]]'s suggestion that the "turrets be dispensed with and the casemate lengthened to accommodate an additional number of guns"<ref name=rw3>Roberts, William, p. 363</ref> 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 {{convert|73|ft|m|1}} to an approximate overall length of {{convert|228|ft|m|1}} so that it now covered the aft [[magazine (artillery)|magazine]] and shell room.<ref name=rw3/> It was provided with a total of 22 [[Glossary of nautical terms (A-L)#gunport|gun ports]], six on each [[Broadside (naval)|broadside]], two on each corner and one each facing the bow and stern.<ref name=ck9/> 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 {{convert|42|in|mm|0}}, but this was inadequate to allow the guns to fully elevate as experience with {{USS|New Ironsides||2}} 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 their [[limbers and caissons|carriages]] 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 Admiral [[Joseph Smith (1790–1877)|Joseph 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 the [[conning tower]] as Webb had intended to mount it on top of the fore turret. A copy of that used by the {{sclass|Miantonomoh|monitor|0}} monitors was installed between the funnel and the [[foremast]] during August 1866.<ref>Roberts, William, pp. 373, 377, 381, 383</ref>

[[File:Webb shipyard - USS Dunderberg.jpg|thumb|left|Illustration from ''[[Harper's Weekly]]'' showing ''Dunderberg'' under construction in late 1863. Note the prominent ram at the ship's bow.]]
''Dunderberg'' was built with a plough-shaped {{convert|44|ft|m|1|adj=on}}, [[naval ram|ram]] bow of which the forward {{convert|12|ft}} were sheathed in [[cast iron]].<ref name=c7>Canney, p. 127</ref> 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 {{convert|50|in|mm|0}}, 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.<ref>Roberts, William, pp. 384–85</ref>

Other problems that delayed the ship's completion were shortages of material, labor and money. Prices for [[pig iron]] and bar iron nearly tripled while [[sheet steel|boiler plate]] and copper roughly doubled. Wages of even inexperienced workers increased between 50 and 100 percent. The [[New York City draft riots]] in July 1863 and several [[machinist]]'s [[Strike action|strikes]] further slowed progress on ''Dunderberg''. 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 the
ship did not meet her specifications in 1865.<ref>Roberts, William, pp. 372, 380</ref>

By about 1864, both sides regarded the ship as a [[white elephant]]; Welles wrote in his [[diary]] 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 the ''Dunderberg'' 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, he [[Ship naming and launching|launched]] the ship, now with her hull complete and about half of her armor installed, with much fanfare. The ''[[New 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 at [[Chincha Islands War|war with Spain]], lest the sale prejudice its [[Alabama Claims|lawsuit]] against Great Britain for selling warships to the Confederacy. Webb did manage to get a [[private bill]] passed by Congress in March 1867 that allowed him title to the ship once he repaid all monies advanced to him.<ref>Roberts, William, pp. 380, 383–84</ref>

==French service==
[[File:The French Ironclad 'Rochambeau', formerly the American 'Dunderberg' - ILN 1863.jpg|thumb|The French Ironclad ''Rochambeau'', formerly the American ''Dunderberg'', [[Illustrated London  News]]]]
After Prussia expressed an interest in the ship, the [[Emperor 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.<ref>Roberts, Stephen, p. 333</ref> 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 at [[Cherbourg]] on 3 August and the French Navy took possession three days later.<ref>Roberts, William, pp. 385–86</ref>

The ship was commissioned and renamed ''Rochambeau'', in honor of the [[Jean-Baptiste Donatien de Vimeur, comte de Rochambeau|Comte de Rochambeau]], a general during the [[American Revolution]],<ref>Silverstone 1984, p. 111</ref> on 7 August. After briefly running machinery trials two days later, Rochambeau began an [[wikt:overhaul|overhaul]] 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 a [[pilothouse]] 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 four [[Canon de 27 C modèle 1864|Canon de 270 Modèle 1864/66]] and 10 [[Canon de 24 C modèle 1864]] (9.4 in) guns, both of which were [[List of British ordnance terms#BL|breech-loading]]. The 15-[[caliber (artillery)|caliber]] {{convert|270|mm|adj=on|sp=us|1}} guns fired a {{convert|216|kg|lb|adj=on|sp=us}} shell while the 17-caliber {{convert|240|mm|adj=on|sp=us|1}} guns fired one that weighed {{convert|144|kg|lb|sp=us}}. The 270&nbsp;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&nbsp;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.<ref>Roberts, Stephen, pp. 333–35</ref>
[[File:Rochambeau (1867).jpg|thumb|''Rochambeau'' in dry dock at [[Brest, France|Brest]] navy yard]]
The French carefully measured the ship during her 1868 overhaul. At the waterline ''Rochambeau'' was {{convert|107.4|m|ftin|sp=us}} long and had a beam of {{convert|22.15|m|ftin|sp=us}}. She had a mean draft of {{convert|6.5|m|ftin|sp=us}}, a [[Glossary of nautical terms (A-L)#depth of hold|depth of hold]] of {{convert|7.078|m|ftin|sp=us}}, and displaced {{convert|7849|t|LT|sp=us}}. They rated her engines at only {{convert|4000|PS|lk=in}}, but they produced a maximum of {{convert|4657|PS}} 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 {{convert|540|t|LT}} of coal and {{convert|735|t|LT}} at deep load. In service the ship proved to burn a lot of coal, full bunkers and {{convert|30|t|LT}} stored on deck provided her a range of only {{convert|2200|km|nmi}} at a speed of {{convert|8|kn}}. They reduced her sail area to {{convert|954.42|sqm|sp=us}}.<ref>Roberts, Stephen, pp. 334–35, 338, 345</ref>

They measured the ship's armor thickness throughout. The casemate was completely protected by {{convert|120|mm|in|sp=us|1|adj=on}} plates. The hull armor extended to a depth of {{convert|2.5|m|ft|sp=us|1}} below the waterline and its upper [[strake]] was {{convert|90|mm|in|sp=us|1}} thick while the lower was {{convert|70|mm|in|sp=us}} thick. Her decks were covered by {{convert|18|mm|in|adj=on|1|sp=us}} plates and the sides of the conning tower were {{convert|250|mm|in|sp=us}} thick. In service, ''Rochambeau'' proved to be very wet and threw up a lot of spray in a [[head 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 {{convert|1.4|m|ftin|sp=us}} 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.<ref>Roberts, Stephen, pp. 334–35, 338–39, 341, 345</ref>
 
''Rochambeau'' completed her refit on 18 May 1868 and was briefly under the command of [[Captain (naval)|Captain]] (''Capitaine de vaisseau'') [[Jules-François-Émile Krantz]] (a future [[List of Naval Ministers of France|Minister 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&nbsp;mm [[pivot gun]] mounted over the forward end of the casemate and the pine planking underneath the guns in the casemate was replaced by oak.<ref>Roberts, Stephen, p. 338</ref>

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 reached [[Copenhagen]] on 31 August. The fleet fruitlessly cruised the [[Baltic Sea]] for several weeks before they were ordered home on 16 September. ''Rochambeau''{{'}}s shallow draft meant that she and the armored [[corvette]] {{ship|French ironclad|Thétis||2}} were ordered to search the mouth of the [[Jade Estuary]] on 26 September for Prussian ships, but they found nothing.<ref>Roberts, Stephen, pp. 338–39, 341, 345</ref>

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.<ref>Roberts, Stephen, p. 345</ref>

==Notes==
{{reflist|group=Note}}

==Footnotes==
{{Reflist}}

== References ==
*{{cite book|last=Canney|first=Donald L.|title=The Old Steam Navy: The Ironclads, 1842–1885|publisher=Naval Institute Press|location=Annapolis, Maryland|date=1993|volume=2|isbn=0-87021-586-8}}
*{{cite book|title=Conway's All the World's Fighting Ships 1860-1905|editor1-last=Chesneau|editor1-first=Roger|editor2-last=Kolesnik|editor2-first=Eugene M.|publisher=Conway Maritime Press|location=Greenwich, UK|date=1979|isbn=0-8317-0302-4|url-access=registration|url=https://archive.org/details/conwaysallworlds0000unse_l2e2}}
*{{cite journal|last=Roberts|first=Stephen S.|year=1993|title=The French Coast Defense Ship Rochambeau|journal=Warship International|publisher=International Naval Records Organization|location=Toledo, Ohio|volume=XXX|issue=4|pages=333–345|issn=0043-0374}}
*{{cite journal|last=Roberts|first=William|year=1993|title=Thunder Mountain: The Ironclad Ram Dunderberg|journal=Warship International|publisher=International Naval Research Organization|location=Toledo, Ohio|volume=XXX|issue=4|pages=363–400|issn=0043-0374}}
*{{cite book|last=Silverstone|first=Paul H.|title=Warships of the Civil War Navies|year=1989|publisher=Naval Institute Press|location=Annapolis, Maryland|isbn=0-87021-783-6}}

==External links==
{{Commons category|Dunderberg (ship, 1865)}}

{{Union ironclads}}
{{French ironclads}}{{List of Ships Built by William H. Webb}}{{World's largest wooden ships}}

{{DEFAULTSORT:Dunderberg}}
[[Category:Ships built in New York City]]
[[Category:Ships built by William H. Webb]]
[[Category:1865 ships]]
[[Category:Ironclad warships of the French Navy]]