One of a number of designs eminating from Uffa’s yard after the Mark I design was complete. Most were not taken forward but the Royal Navy did have a boat, RN-1, to a 17’6″ design built to trial on their Fairey Aviation Barracudas. It had to be smaller than the Mark I to fit the plane and indeed was narrow with greater tumblehome. Fairey Marine documentation also refers to the experimentation but the number built and any operational use are not known. The Imperial War Museum has many photographs from the trials.