Udema

An udema (also udenma) was a type of warship built for the Swedish archipelago fleet in the late 18th and early 19th centuries. It was developed for warfare in the Archipelago Sea and along the coasts of Svealand and Finland against the Russian navy. The udema was designed by the prolific naval architect Fredrik Henrik af Chapman for use in an area of mostly shallow waters and groups of islands and islets that extend from Stockholm all the way to the Gulf of Finland.

Background
In the early 18th century, the establishment of Russian naval power in the Baltic challenged the interests of Sweden, at the time one of the major powers in the Baltic. The Swedish empire at the time included territory in Northern Germany, all of modern Finland and most of the Baltic states, a dominion held together by the Baltic sea routes. Russian Tsar Peter the Great had established a new capital and naval base in Saint Petersburg in 1703. During the Great Northern War Sweden lost its Baltic state territories, and experienced destructive Russian raiding in Finland and along the chain of islands and archipelagos that stretched all the way from the Gulf of Finland to the capital of Stockholm. The traumatic experience led to the establishment of inshore flotillas of shallow-draft vessels. The first of these consisted mainly of smaller versions of the traditional Mediterranean warship, the galleys. Most of these more akin to galiots and were complemented with gun prams. The disastrous war against Russia 1741-43 and the minor involvement in Prussia in the Seven Years' War 1757-62 showed the need for further expansion and development of the inshore flotillas with more specialized vessels.

Traditional galleys were effective as troop transports for amphibious operations, but were severely under-gunned, especially in relation to their large crews; a galley with a 250-man crew, most of whom were rowers, would typically be armed with only one 24-pounder cannon and two 6-pounders, all in the bow. However, they were undecked and lacked adequate shelter for the rower-soldiers, great numbers of which succumbed to illness in the war of 1741-43. The Swedish military invested considerable resources into the establishment of the "archipelago fleet" (skärgårdsflottan), a separate branch of the armed forced that organizationally belonged to the army. In 1756, it was even officially designated Arméns flotta, "Navy of the Army", though it was in many ways a highly independent organization that attracted a social and cultural elite and enjoyed the protection of Gustav III after his 1772 coup that empowered him as an absolute monarch.

Several new ships were designed by the naval architect Fredrik Henrik af Chapman to bolster the hitting-power of the new Swedish arm, to provide it with better naval defense and greater fire support capabilities during amphibious operations. The result was four new vessels that combined the maneuverability of oar-powered galleys with the superior rigs and decent living conditions of sailing ships: the udema, pojama, turuma and hemmema, named after the Finnish regions of Uusimaa ("Uudenmaan" in genitive form), Pohjanmaa, Turunmaa and Hämeenmaa (Tavastia). All four have been referred to as skärgårdsfregatter, "archipelago frigates", in Swedish and English historical literature, though the smaller udema and pojama are also described as "archipelago corvettes" originally. The name "udema" has been carried on (in its more modern variant) as a traditional vessel name in the Finnish navy, with several ships named after the type.

Design
The first udema was built in 1760 and had two masts (mainmast and foremast) that were originally rigged with lateen sails with the later two ships adding an additional mizzen mast. It was later provided with a square sail rig similar to that of a polacca bark without topgallant sails. It had a low hull with a small quarterdeck structure and an arrangement of guns that was completely unique for its time. Its main armament consisted of a single line of eight 12-pound guns along the centerline of the ship and two 12-pounders in the bow facing forwards.. The centerline guns used pivoting carriages that could be rotated 360 degrees and aimed to either side of the ship in a manner reminiscent to the modern dreadnought battleships of the 20th century.

The first udema Gamla was c. 30 m (100 ft) long and with a draft of 1.5 m (5 ft). The later udemas, Torborg and Ingeborg were both longer and wider, 37 m (121 ft) long and almost 9 m (29 ft) wide with a draft of just over 3 m (10 ft). Torborg, built in 1772, had three additional 12-pounders, eleven in the centerline and two in bow facing forwards, housed under a decked superstructure with gun ports, but with the rowing seats left undecked. This arrangement proved to be less successful with reports about problems with splintering and lingering gunpowder smoke. She was also a poor sailer and slow under oars, earning the udema a poor reputation.

The Ingeborg, built in 1776, had an eight-12-pounder centerline armament which was open to the elements, but two heavy 18-pounders in the bow and two 6-pounders chase guns in the stern. The rowing benches with room for three men per bench were on either side of the centerline battery, but had to swung forwards and outwards to allow the guns to pivot to either side.

For additional maneuverability, the udema carried 14-18 pairs of oars. Rowers sat on the weather deck on either side of the main armament with the oarpoarts placed on a rectangular outrigger which improved their leverage. Rowers sat on the gun deck right next to the main battery and could not operate the oars when they were fired. In action, the udema had to rely on its sails for propulsion.

The concept of hybrid frigates with oar propulsion capabilities was not new. Small "galleasses" had been built for the English navy as early as the mid-16th century, and the Royal Navy had equipped the equivalent of sixth rates with oar ports on or below the gundeck as early as the 1660s. "Shebecks", Baltic variations on the Mediterranean xebecs, had been introduced in the Russian navy for inshore duties during the 18th century. Both of these have been suggested as possible inspirations for af Chapman's new designs.

Service
Only three udemas were built for the Swedish navy. Russian ship builders copied the Swedish designs, particularly around the time of the war of 1788-90, and it is believed that a type named simply "secret vessel" could have been a Russian udema. However, the conclusion has been questioned on account of the number of guns (44 in total), making it possible that it was actually a considerably larger turuma, one of larger "archipelago frigates".

The three Swedish udemas served in the Finnish archipelago squadrons throughout the Russo-Swedish war of 1788-90 by supporting amphibious operations, raiding the opposing Russian archipelago fleet, and protecting the left flank of Swedish army's operations on the Finnish mainland. Udemas fought in both the first and second battles of Svensksund. In the latter, which was one of the largest naval battles ever fought, a disastrous defeat for the Russians, and one of Sweden's greatest naval victory ever, the udema Ingeborg was among the few Swedish vessels lost.

Like the other specialized archipelago vessels, the udema proved to have only limited advantages. While it had superior firepower, its sailing qualities were poor, even compared with galleys, and were slow even under oars. The unconventional artillery layout was also deemed to be too weak and radical. The second battle of Svensksund showed that the smaller gunboats and gunsloops were far more efficient for the same operations and had almost entirely replaced the "archipelago frigates" by the Finnish War of 1808-9, where Sweden finally lost all of its Finnish possessions.

Influence
Though somewhat of a disappointment in Swedish service, historian Lars-Olof Berg suggest that the radical new design of rotating gun mounts may have influenced shipbuilders in other countries. Russian floating batteries were equipped with similar mounts by 1790. Designs were also presented and built in Great Britain and the US. Pivoting mounts were used in the US Jeffersonian so-called gunboat navy, even in much smaller craft, though it was often proved risky since the recoil could destabilize vessels with a small displacement, especially if fired over the side. The genuine breakthrough for true centerline armament layouts, however, did not come until the advent of armored steamships in the late 19th century.

Ships
Only three udemas are know to have been built, all of them for the Swedish archipelago fleet. These are listed below with launch year in parenthesis. Two udemas armed with a 24-pound armament were planned in 1760-62, but were never built.


 * Gamla, also called Uusima (1760)
 * Torborg (1772)
 * Ingeborg (1776, sunk at the battle of Svensksund)