In addition to the low resolution versions that are on the RMG Collections website available for free you can purchase the high res version as mentioned by Christian. There are free high resolution copies of these same plans from RMG of a couple of the
Swan Class ships at
https://commons.wikimedia.org/wiki/Category:Ship_plans_of_the_Royal_Museums_Greenwich
Be careful to get the correct year. For example there are two set of
Swan plans, one from 1766 and one from 1781. The design provided for 16 gunports (8 per side, excluding the bridle-ports) and one pair was initially left unoccupied, and the ships were always rated at 14 guns. However, an eighth pair of guns was added from 1780 onwards to utilize the vacant ports, without any change in the nominal rating.
Do you have the original contract of her sister
Hornet 1775? It gives the dimensions of every part of the vessel. Just in case I have attached a PDF of my transcribed copy.
Allan