STUART ROY - NAVAL ARCHITECT
Fellow of the Royal Institution of Naval Architects & Chartered Engineer
Part 2: The design proposal and initial hull design
When working on his book, Chapman had the immense foresight and incredible dedication to “lift off” the hull measurements enabling him to record both the lines and the general arrangement layouts of some 120 vessels of the time including many from England, providing us with extensive insight to the vessels that we might now describe as “traditional”. A few years later in 1774 Chapman designed the Swedish Royal Barge “Vasaorden”. This boat is still in use today, but after serious fire damage in 1921 it was completely rebuilt in 1923.
When reviewing and analysing the plans and details of ornate historic rowbarges it became clear that through ancestry, evolution and refinement in use, the large rowbarge of Canaletto’s time had become very much more than a work of art. Most examples actually incorporated a refined and very effective low-drag hull form that would be difficult to better when designing a large man-propelled vessel. For a new rowbarge the major problem was how big should she be. She had to be much larger than Prince Frederick’s barge to carry the 30 passengers and the watertight bulkheads required by the MCA Code, plus the auxiliary engines required for manoeuvrability on a busy waterway and for re-positioning the boat quickly between engagements. But the power available from 18 oarsmen is still less than 9hp (6.71kW) however efficiently it is delivered, so the boat had to be slim, fast and not too heavy. Eventually after two increases in length and one in beam, it was found that a boat of 88ft (26.65m) overall length, 75ft 9ins (23.093m) waterline length, 12ft 6ins (3.795m) of beam and 35,150 lbs (16 tonnes) displacement fully loaded would be the largest feasible size that could be rowed at a reasonable speed on the tidal pageant course. And to accommodate the requirements for damage survivability in the event of an incident, the boat could not be a “walk-through” design as with earlier examples such as Vasaorden, but would need to be a “pontoon” of 7 watertight compartments with all the people placed above. By building the rowing benches above sealed “footwells”, the space beneath the sole would be buoyancy.
Effectively the hull design for what became “Gloriana” was based on the best features of the various boats mentioned earlier. Although Mark had found some historic plans of an 8-oared shallop that he particularly favoured it was not possible simply to scale up a 45ft long shallop to 90ft in length as the resulting boat would be far too heavy with rowlock positions that would be too high above the water for the oarsmen to use efficiently. The procedure was therefore to analyse the characteristics of the favoured hull forms and select the best features, ratios and values for the hull form coefficients and incorporate them in a new hull form of appropriate size and style. The selected hull features included the rake of the bow, angle of entrance at the waterline, the midships section, the shape of the run, the flare of the bow and the rounding of the sides. All this was blended into a hull that had the required overall dimensions and displacement, with optimum prismatic, block and water-plane area coefficients for low drag at rowing speeds to make best use of the limited power available from the oars. With all the technical requirements identified, the hull form for the new rowbarge was carefully defined on the computer screen in 3D using the excellent Maxsurf program from Western Australia. The hull was then “faired”, a process employed by naval architects to develop, refine and check the hull shape to ensure that it is smooth in all planes and suitably attractive when viewed from all angles. With initial estimates for the weight of the hull structure, rowers, crew and payload indicating a total of around 16 tonnes fully loaded the proposed hull form was designed to float on her draught marks at that displacement.
After 5 months working alone on the project, a design proposal had been prepared, a suitable hull design was complete and a preliminary 3D computer model had been developed. This enabled the stability to be assessed and the power required to be predicted using computer analysis of the hull model. With steady rowing using 18 oars, the speed of the boat was calculated to be 4 – 4.5 knots with the potential for 8 – 10 knots under auxiliary power, depending on how much power was installed. At that stage it was thought that a 30hp (22kW) hybrid diesel-electric system driving a single propeller would be ideal for the auxiliary power, but to save weight and provide greater efficiency this was later changed to an electric system powered by lithium batteries, twin 8kW motors, saildrive legs and self-pitching propellers.
To complete the proposal stage of the design process, a full set of preliminary stability calculations for both intact and simulated damaged cases was prepared and submitted to the Stability Unit of the MCA in Greenock. The client, Lord Jeffrey Sterling, had “come aboard” and kindly supported all the initial design and feasibility work. Then, to my great relief, in mid-September I received confirmation from the MCA that the proposed design had been accepted in principle and the results of the stability calculations were satisfactory. It was then time for Lord Sterling to “press the button” and start the project to build “Gloriana”.
In addition to having stability characteristics that meet or exceed the requirements of the relevant MCA Code, a passenger vessel must have its plans approved and be constructed in accordance with the rules and regulations published by a Classification Society. For Gloriana, the MCA requested that both the plan approval of the construction and the in-build inspections be undertaken by Lloyd’s Register, the world’s oldest, largest and most experienced classification society. It is interesting to note that Lloyd’s Register was founded in 1760, just at the time when the number of ceremonial rowbarges in use on the Thames was at its peak.
Part 3 - Construction
Vasaorden: Swedish Royal Barge, 1774
Gloriana: The Design Proposal submitted for Provisional Approval September 2011
Predicted wave pattern at rowing speed
and at full speed under power
Gloriana: Preliminary Hull Body Sections showing the rowers’ foot wells
Creating “Gloriana” - The Naval Architect’s story ………….