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The Merlin, a unique subject for scale By Martin Simons In 1953 Fred Slingsby in England began production of the Type 41, Skylark 2, one of the first gliders ever to have a NACA six digit, low drag wing profile and certainly the first ‘laminar flow’ sailplane to enter production. It had a wing span of 48 feet, slightly less than the fifteen metres nominated for the (then new) ‘Standard Class’ in World Championships. The performance was very good and the type became popular with British gliding clubs and pilots. (Slingsby soon followed it with the Skylark 3, with over three metres additional span.) Rudolf Kaiser’s Ka 6 won the Standard Class design prize in 1958, and with it Heinz Huth twice won the St Class World Championships. The Skylark 2 already began to seem out of date. A group of aircraft engineers at the Bristol Gliding Club, led by Dennis Corrick, decided that the Skylark 2 could be considerably improved. A wind tunnel model was made to test the ideas before construction was begun. Taking an existing ‘2, they went through a program of modifications that produced the Skylark 2 Mark 4, christened Merlin. The most significant change was to reduce the wing rigging angle on the fuselage by four degrees. This ensured that the fuselage was aligned with the airflow at high airspeeds, and so generated less parasitic drag. The low speed performance for soaring was hardly affected. A slight adjustment of the elevator neutral angle was required to maintain trimming balance.
The only noticeable change in handling was that the fuselage was more tail down when landing, so the tail skid touched before the main landing wheel. Since the main wheel was also set further into the fuselage, and further forward, landings tended to be slightly heavier but not enough to trouble anyone. The wing span was increased to the full 15 metres by adding Hoerner tips. Other details included a much improved wing root fairing, smaller and better faired skids, and sealing of control line hinges and all other gaps and leakages. It was considered that the Merlin was capable of keeping up with the bigger Skylark 3 in competition flying. The Merlin remained in use for many years at Brisol but, when plastic sailplanes arrived, older, wooden gliders were often neglected and the Merlin remained out of use for over twenty years, slowly deteriorating in storage. It was rescued from this sad fate by Tony Cummins. He was able to negotiate for possession of the glider and worked hard for several years to bring it back to first class condition and full airworthiness. It is now as good as new, beautifully finished in its bright yellow colour and still carrying the contest number, 33, on the vertical tail. After some early test flights in 2005, Tony brought it to the Vintage Glider Club rally at Camphill in June-July 2005. In mediocre soaring conditions he showed the Merlin to be as good now as ever it was before, capable of keeping up with the best of its generation. |
