The original drawings for the LEDA class frigates are all held by the National Maritime Museum, Greenwich, London SE10, and show the hull construction in considerable detail. Not all the drawings are specific to UNICORN, but most of those listed below are for ships of the same batch within the LEDA class of Frigates, together with a selection illustrating the development of Seppings’ final design. High resolution scans, prints and black & white copies are available from the Museum in various sizes and formats. The National Maritime Museum website has current ordering information, and uses the ZAZ number for b/w prints and the J number for colour prints and scans.
1596 / J9394 / ZAZ1964 Draught
“Draught of the Frigates of 46 guns building at His Majesty’s Dock-yard at Chatham, the Diana and Latona” (shows the lines and exterior fittings)
1597 / J3933 / ZAZ1965 Profile
“Profile for the 46 gun Frigates, Diana, Thames, Mermaid & Unicorn, building in His Majesty’s Dock Yard at Chatham…”" (a longitudinal section through the ship)
1604 / J3905 / ZAZ2018 Profile of Hamadryad
“Profile of the Hamadryad and Thisbe of 46 Guns…” (shows diagonal riders very clearly, cleaner copy than 1597)
1598 / J3931 / ZAZ1966 Orlop Deck
“Plan of the Orlop and Platforms for Frigates of 46 guns building in H. M. Dock Yard at Chatham vizt. Diana, Thames, Mermaid & Unicorn. Navy Office July 30th 1821.” (a plan view of the deck)
1599 / J3930 / ZAZ1967 Lower Deck
“Plan of the Lower Deck for Frigates of 46 guns (Hebe Class) building in H. M. Dock Yard at Chatham vizt. Diana, Thames, Mermaid & Unicorn. Navy Office July 30th 1821.”(a plan view of the deck)
1600 / J3929 / ZAZ1968 Upper Deck
“Plan of the Upper Deck for Frigates of 46 guns building in H. M. Dock Yard at Chatham vizt. Diana, Thames, Mermaid & Unicorn. When built with a diagonal deck the green lines to be conformed to. Navy Office July 30th 1821.” (a plan view of the deck)
1601 / J3928 / ZAZ1969 Quarter Deck and Forecastle
“Plan of the Quarter Deck and Forecastle for the 46 gun Frigates Diana, Thames, Mermaid & Unicorn building in His Majesty’s Dock Yard at Chatham. Navy Office July 30th 1821.” (a plan view of the deck)
1662 / J3932 / ZAZ1970 Disposition of the Frame
“A Disposition of the Frame proposed for Frigates of 46 Guns. Navy Office Septemr. 1817.” (showing the arrangement of the hull frames)
6576 / J3796 / ZAZ2156 Planking Expansion (showing shifts of butts, etc.)
“Disposition of the Planking for a 46 Gun Frigate of the Hebe Class”
6628 / J4279 / ZAZ1971 Head of Minerva (detailing an almost identical head to Unicorn’s.)
1609 / J3899 / ZAZ2023 Drawing of the Circular Stern of the 46 gun Frigates… (good detail of the stern galleries)
6027 / J3920 / ZAZ1990 Fittings to Quarterdeck and Forecastle of Frigates of 42 guns as Melampus… (good detail of fittings which would scale up for 46 gun frigates)
1603 / J3900 / ZAZ2017 “Part of the Midship section of the 46 Gun Frigates…” (labelled Hamadryad) (for the batch built at Pembroke)
6027 / J3920 / ZAZ1990 Melampus. “Fittings to Quarterdeck and Forecastle of Frigates of 42 guns (misprint for 46?) as Melampus”… (good detail of fittings inside the bulwarks)
1970 / J4077 / ZAZ2008 Leda Midsection. Later drawing of modified Leda class midsection, dated December 1815 and showing comparison between scarphed and coaked frame futtocks.
1413b / J3729 / ZAZ2130 “Midship Section for the Frigates of 46 Guns….” (Seringapatam class, with steep floors, but shows coaked frame construction very clearly)
The following series of draughts are also of interest as they illustrate the development of the Leda class from conventionally framed transom stern frigates to the final version, as seen in Unicorn, incorporating the full set of Sir Robert Seppings’ innovations:-
1931 / J4079 / ZAZ4909 Leda Draught This is the master draught for the original Leda Class dated 1796, heavily amended and annotated over the years with notes of copies sent out for building groups including the copies sent to Bombay for the Indian sub-group, and with an interesting pencil sketch showing the Seppings circular stern over the original transom stern.
1610 / J3943 / ZAZ1980 Arethusa Draught “A Draught of the Frigates of 46 Guns (151ft 5ins crossed out changed to 151ft 9ins, 1073 49/94 changed to 1077 6/94. Copies to Deptford, Portsmouth, Sheerness etc (illegilble and torn). Forecastle ports modified for Daedalus “The Hebe, Clyde, (Jason) and Medusa to be built at Woolwich, The Nereus, Druid, Hamadryad, (Nemesis) and Thisbe to be built at Pembroke. The Diana and Latona to be built at Chatham” Note: Arethusa only mentioned in later pencil scrawl. Note: Circular stern, deck plan shows transom.
1611 / J3937 / ZAZ1981 Arethusa Profile. Shows Seppings’ earlier wooden trussed frame system of diagonal riders. This may be the precursor draught.
1612 / J3939 / ZAZ1982 Arethusa Platforms and Orlop
1613 / J3938 / ZAZ1983 Arethusa Lower Deck
1614 / J3940 / ZAZ1984 Arethusa Upper Deck (shows transom stern)
1615 / J3941 / ZAZ1985 Arethusa Quarterdeck and Forecastle