Roger Calvert's Steamboating Page
Roger Calvert's Books about Steam


SL Senta

Senta is based on a Flying Dutchman sailing boat shell, never fitted out for sailing. She is built of cold-moulded plywood, sheathed with glass fibre. She was first fitted out for steam in 1976; since then there have been many incremental changes, most of them improvements.

Overall length:6.1 m20 ft 
Beam:1.8 m5 ft 9 in
Draught:0.5 m20 in
Air draught:1.5 m5 ft

Senta on the Stratford Avon 1979


Senta on the Beaulieu River, July 2011 (Photo: Mike Bell)

Technical details:

For many years, Senta had a non-condensing "puffer" plant, using river water if fresh, otherwise an on-board tank. In 2002, the plant was converted to be either condensing or puffing, by changing a couple of valves. In 2003, an air pump was fitted, and the puffing facility removed.

Boiler: Vertical centre drum 8 coil (Ofeldt type) copper boiler, approximately 1 sq m (10 sq ft) heating area; built in 1993, but barely used until installed in Senta in June 2009. This replaced the previous vertical cross-tube boiler, fitted 1999 (itself replacing the second of two Merryweather 'A' boilers) which showed signs of trouble on an outing on the River Wey in May 2009, later inspection showing a hole from the water space to the centre flue at about the water level. It was not practical to repair this, so the current boiler was obtained and fitted.

Maximum operating pressure 7 bar (100 lb/sq in). Solid fuel (wood and coal).


Engine: Stuart Turner 5A, double acting single cylinder, 58 mm (2¼ in) bore by 51 mm (2 in) stroke, Stephenson's link reverse gear. Normal operating speed 400 to 500 rev/min. (Similar to the animation below.)

Condenser: 2 copper tubes approximately 16 mm (5/8 in) diameter, 1.2 m (4 ft) long, under the after part of the hull.

Transmission: 2:1 bevel gear step down to the propeller shaft; universal joints, thrust block at stern gland. Propeller 36 cm (14 in) diameter by 51 cm (20 in) pitch.

Auxiliaries: Prop-shaft driven feed pump with air pump on the same eccentric; hand feed pump; funnel blower; whistle; bilge ejector; Windermere kettle; electronic tachometer (converted from a bicycle speedometer).

Summer 2021: automatic bypass fitted, with float valve in the hot well.

Senta on Windermere, August 2002 (photo Roger Calvert)


Senta had a complete hull overhaul and paint during the winter 2008-09. The result is excellent - see the picture on the right.

When the new boiler was fitted in 2009, the previous wooden boiler casing did not fit, so for a while the finish was the plain steel casing. Over the next year, though, vertical wooden stave cladding has been added.

Senta on Windermere, September 2012 (photo Richard Bartrop)
Senta on the River Wey, May 2009 (photo Marguerite Calvert) Senta on Windermere Sept 2012 (photo Dot Bullough)
Senta January 2013 (photo: Roger Calvert)

Heavy weather!

Before the heavy snowfall in January 2013, the canopy was supporting the tarpaulin. Major repairs to the canopy structure were needed!

This has been resolved in January 2015 by the provision of a splendid new boat house!

New boat house January 2015 (photo: Marguerite Calvert)

Steamboat Links

animation of single cylinder double acting steam engine

Animation of single cylinder double acting steam engine


I can recommend the following books as being of interest to steamboaters:

Steam Boat Register

Published by the Steam Boat Association, with details of all known steamboats in the UK.

Steam Engine Principles: Their Application on a small scale by NG Calvert

A technically sound but accessible introduction to the theory and practise of small scale steam plant. Ideal for the model engineer or preservationist: 1991, ISBN 0 951360 1 1, paperback, 130 pages

Steamboating Guide

A compilation of articles from The Funnel, the magazine of the Steam Boat Association of Great Britain covering practical matters ranging from designing boilers to tying knots: 1994, ISBN 0 9513620 4 6, paperback, 175 pages. This book is still available, at a reduced price, following the publication of a new edition by the Steam Boat Association.

Steam Tables and Other Data for Steam Enthusiasts

Tables, in both British Thermal and SI units, of the properties of steam over the range of interest for preserved and reproduction steam engines, and other relevant data: 1991, ISBN 0 9513620 2 X, booklet, 12 pages.

The three above titles and 'The Story of Shamrock' may be obtained direct from the publisher.

Copyright © Roger Calvert and photographers 1998-2021.  Last updated: 29/12/2021.

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