Akella based the 'Defiant' on a kit model of HMS Unicorn (28 guns). While the kit claims to represent a frigate built by Fredrik Henrik af Chapman and launched in 1700, several facts make that impossible, not the least of which are that Chapman was not born until 1721 and the first frigate bearing the name Unicorn did not enter service until 1748. It is this HMS Unicorn that the in game and Corel models actually represent.
HMS Unicorn was a 28-gun, Sixth Rate frigate of the Royal Navy. Originally ordered as a 24 gun ship to the draft of the French privateer Tyger. The third vessel of the Royal Navy to bear the name, the Unicorn, as well as the Lyme which was a near-sister, were the first true frigates built for the Royal Navy. They were actually completed with 28 guns including the four smaller weapons on the quarterdeck, but the latter were not included in the ship's official establishment until 22 September 1756. The two ships differed in detail, the Unicorn having a beakhead bow, a unicorn figurehead , two-light quarter galleries and only five pairs of quarterdeck gunports, while the Lyme had a round bow, a lion figurehead, three-light quarter galleries and six pairs of quarterdeck gunports.
The Unicorn was first commissioned in March 1749 under Captain Molyneaux Shuldham, under whose command she spent her first commission in the Mediterranean until returning home to pay off at Deptford in June 1752. After repairs, she was recommissioned in January 1753 under Captain Matthew Buckle, and sailed for the Mediterranean again in April 1753. In February 1756 command passed to Captain James Galbraith, then in that September to Captain John Rawling. After active and continuous service during the Seven Years War, she finally paid off in late 1763, and was broken up in 1771.