Basic model performance problems

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I 4.1 GENERAL POINTS

The diagrams of Chapter 1 and the main relationships of lift and drag to flight velocity, wing area, etc., help in the analysis of all model performance problems. For engine driven і models the need is usually either to achieve maximum speed with full control, for a pylon racer, or maximum rate of climb with a few seconds’ engine run, followed by a safe transition to gliding with a slow rate of sink, for duration types. For rubber driven models ; the climb problem is to make the most effective use of the energy stored in a given weight і of rubber, with, again, a smooth transition to gliding at the minimum possible rate of I descent For motor-assisted gliders, and electric-powered models, the primary concern ‘ may be with the margin of power available for climbing above the bare minimum required for level flight. For sailplanes the achievement of minimum sinking speed is always important, with safe characteristics on the towline for thermal soarers. For radio – controlled sailplanes, the quality of‘penetration’ is equally necessary. A model with good penetration is one which still retains a low rate of descent when flying fast. This will і enable it not only to make headway against a wind without too much loss of height, but in cross-country and slope soaring it will be able to pass through areas of sinking air more easily and reach the next upcurrent zone both sooner and higher than a sailplane with poor glide at high speeds.

I Fcr speed tasks, a sailplane has to fly very fast down a steep glide slope, with high ‘ speed reversals of direction at each end of the course. The requirements are very similar to those of the powered pylon racer, with the difference that the same model must also soar.