admin Date , September 3, 2025 Sailing Previous Blog Double Digit Wind Speeds Last Comments (0)
The motorway was busy. For some it was the first day back at school. For all it was windy and raining very hard. So no-one else turned up for Wednesdays on the water, even though the sun came out and the showers were infrequent. Sally the instructor turned up, so instead we talked about Raters - in particular Sally's B-Rater - Vanessa
Sally's B-Rater Vanessa next to Dainty Two, an A-Rater who is upside down and her hull almost fully restored.
The Thames A-Rater and B-Rater are both historic sailing dinghies associated with the River Thames, especially in places like Upper Thames Sailing Club and Thames Sailing Club. However, the A-Rater is the far more prominent and well-known class — the B-Rater was a short-lived experiment that didn’t catch on in the same way.
Here’s a breakdown of the key differences:
Thames A-Rater (The Famous One)
Purpose: Designed for maximum speed on the narrow, winding Thames
Length: ~27 feet (8.4m)
Beam: ~6 feet (1.85m)
Weight: Over 750lbs including all fittings
Sail area: Enormous — 350 sq ft and for a wooden rater 385 sq ft
Rig: Tall rotating mast (~45 feet high), powerful fully battened main, jib. A spinnaker is possible but not allowed for racing on the Thames.
Crew: 3 (usually: helm, mid-hand and jib-hand)
Top Speed: Very fast, especially on a reach or with gusts downriver
Performance: Outstanding acceleration and agility on flat water
Class Origin: Developed from the mid‑1800s, formalised as a class in 1907
Design: Open development class — hull and rig designs have evolved over time
Where Sailed: Mainly on the non-tidal Thames (e.g., UTSC, TSC, Thamesis SC)
Fun Fact: A-Raters are often seen planing upriver, which seems like witchcraft to newcomers. Their huge rigs and narrow hulls allow for blistering performance in just a puff of wind.
Thames B-Rater (The Experimental One)
Purpose: Intended as a cheaper, smaller alternative to the A-Rater. This doesn't appear to be true. The B-Rater is just as expensive as an A-Rater
Length: ~16–21 feet
Beam: Slightly wider than an A-Rater, for stability
Sail area: Much less than an A-Rater
Crew: possibly 2 but usually 3 like the A-Rater
Rig: More conventional than A-Rater — fixed or shorter rotating mast
Performance: Slightly slower, easier to handle, seen as less glamorous - but most can't tell a B-Rater form an A-Rater especially when they race together
Class Origin: 1900s–30s (varied attempts)
Design: Few boats were ever built; never caught on as a class
Where Sailed: Rare — very few B-Raters exist today. The only one that I know of is Vanessa (Saucy Sally is no longer viable)
Looking at the picture we can we that Vanessa is only about 1 ft shorter than the A-Rater - but it is water line length that is important and this I haven't measured yet. Vanessa has a similar beam to an A-Rater and can either be rigged as an A or as a B-Rater. Originally designed with a Gunter rig, Vanessa was the first Rater to have a Marconi rig (now called a Bermuda Rig). Vanessa built in 1902 was one of the first Raters.
When rigged as an A-Rater Vanessa is very fast sometime to the point of being uncontrollable.
Glamour Factor: When fully repaired, with a ivory on slip top and a varnished wooden hull, Vanessa will be one of the most beautiful Raters on the water and able to sport an A-Rater rig, a smaller B-Rater pointed sail rig or maybe a Gunter Rig as she had when built.
