page_title: Udema
section_title: Design
hierarchical_section_title: Udema / Design
caption_attribution_description: English: Contemporary model of the udema Thorborg (built 1772) at the Maritime Museum in Stockholm. Scale 1:16.
context_page_description: 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 in the Baltic 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.
  The udema was of an innovative new design with a single line of guns along the ship's centerline, a foreshadowing of the dreadnought battleships of the early 20th century. The design proved impractical for its time, however, and only three udemas were built between 1760 and 1776.
context_section_description: The first udema was built in 1760 and had two masts (mainmast and foremast) that were originally rigged with lateen sails. 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 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, similar to the main guns of the 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, carried a mizzen mast, and 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 the 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-pounder 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 swing forwards and outwards to allow the guns to pivot to either side.
  For additional maneuverability, the udema carried 14 to 18 pairs of oars. Rowers sat on the weather deck on either side of the main armament with the oar ports placed on a rectangular outrigger which improved their leverage. However, they were positioned on either side of the centerline battery and could not row under fire; 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 Tudor navy as early as the mid-16th century. The Royal Navy, its successor, later 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.
caption: Contemporary model of the udema Thorborg (built in 1772) at the Maritime Museum in Stockholm. The centerline armament of the Thorborg was housed under a deck structure that covered the guns while leaving the rowing positions open to the elements.
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