Profiles

A series of seven foils was developed for the wing using Xfoil. The objectives and constraints are the same as a conventional standard class sailplane, but with an extra constraint on pitching moment and our Reynolds numbers are slightly lower.
We have a well defined climb knee near Clmax and the lower surfaces stay laminar untill 90 knots at an all up mass of 233kg.
(In graphs below br2 is root and br8 is tip)

Design and Optimisation

An initial configuration was developed intuitively with vortex lattice tools. The ideas for the wing lift distribution were developed from research on a flying wing project where we had to explore non eliptic loadings to minimise adverse yaw. Because the SG-1 wing is smaller than normal, the optimisation can be with a relaxed constraint on span. The result is slightly tapered loadings that satisfy the Cdi and adverse yaw requirements.

For the optimisation of wing loading, wing area and aspect ratio a method was developed from the ideas of Fred Thomas. Thermals were categorised into types and optimum turn radii and interthermal speeds were calculated for each type. A simple cross country model gave cross country speeds and comparisons here allowed optimisation.

A scale model of an early version of our design gave some qualitative results. The final SG-1 design has less taper and sweep in the fin, which commences futher aft of the wing's pressure recovery zone and has a more even load and Cl distibution.