Observers at the Oxford and Cambridge University boat races on the Thames had noticed an increase in the number of steam launches to be found on the river between Putney and Mortlake. It had been recognized that the weight of the boat and machinery needed to be kept as low as possible. Steel and iron plates had been used for hull construction and waterproof paper planking had also been suggested as a means of reducing the weight of the hull. Propellers were four bladed, with the blades curved backwards, and presenting a large surface. Both vertical and horizontal boilers were used, with Messrs. Yarrow and Hedley, of the Isle of Dogs, and Messrs. Plenty, of Newbury, preferring to use horizontal fire tube boilers, with tubes running directly to the smoke-box in the smaller boilers, and returning along the sides of the fire-box in the larger ones. As for engines, the simplest ones were thought to be the best for pleasure launches, heavier engines being more expensive to make and maintain.