
The charm of The Tall Ships Races is that so many different ships take part and visitors to the quayside can go on board.
Class A
All sailing ships over 40m length overall (LOA).
Class B
Traditionally rigged ships with an LOA of less than 40m and a waterline length (LWL) of at least 9.14 metres. Traditionally rigged ships are defined as those ships whose sail plane has a predominance of gaff sails.
Class C
Modern rigged ships with an LOA of less than 40m and an LWL of at least 9.14 metres not carrying spinnaker-like sails. Modern rigged ships are defined as those ships whose sail plan has a predominance of Bermuda sales.
Class D
Modern rigged ships with an LOA of less than 40 metres and an LWL of at least 9.14 metres carrying spinnaker-like sails.

http://www.tallshipsraceshalmstad.se/en/theships.2000_en.html