Aerodynamics

From wind tunnel to super-ellipse

Almost irreconcilable: minimum sink with good thermalling qualities, excellent glide also at higher speeds, as well as very docile handling.

These goals could be fulfilled in the Antares. The aerodynamic design is the result of a multi-year research project, and it was created, uncompromisingly, as a unified design. In doing so, all conceivable measures of optimization were utilized. Nine perfectly harmonized airfoils ensure a minimal profile drag. The laminar flow on the bottom surface reaches 95 percent of the airfoil chord. Here, a zig-zag shaped turbulator tape forces a transition from a laminar to a turbulent boundary layer.

A turbulator tape that is properly dimensioned and positioned according to the boundary layer conditions has no significant performance drawbacks when compared to boundary layer blowing. However, the tape is significantly less sensitive to dirt and scratches. The airflow over the top surface remains laminar up to 75 percent of the airfoil chord. This is currently the highest achievable value for an airfoil without boundary layer suction.

An additional negative flap setting of -3° can be selected for fast glide. This allows for very high speed flights with unachievable glide performances. Only at air-speeds of 220 kph / 119 kts to 245 kph /  132 kts (depending on the wing loading), do the airfoils leave the laminar drag bucket.

Wing geometry

An extremely slender super-ellipse defines the wing geometry of the Antares 20E. Through this geometry, the induced drag is reduced to the theoretical mini- mum. This corresponds with the optimal values of the untwisted elliptical wing, but without having to accept the critical stall characteristics of this classic layout.

The wide outer wings and winglets effectuate very docile flight qualities. In addition, the winglets facilitate 5 percent reduction of the induced drag. As a result, the induced drag of the 20m Antares wing is only 95 percent of the induced drag of an equivalent flat, untwisted elliptical wing.

Detail perfection

The Antares 20E possesses a wing area adapted to the needs of a motorglider.

This, together with a high aspect ratio of 32, guarantees excellent climbing characteristics in thermal flight.

 

  • Wing and winglets have been developed as a single unit. Being in perfect harmony with the wing, the winglets yield substantial drag reductions, while at the same time improving flight characteristics
  • The compact electric motor permits an optimal rear fuselage contraction, which results in a further drag reduction.
  • Aerodynamic performance losses in the area of the wing-fuselage junction have been minimized through  a special fuselage center section design combined with the use of custom turbulent airfoils in the vicinity of the fuselage.

Handling

Full span flaperons give the Antares 20E extreme agility. The flaperons are actuated through a novel control mechanism which, together with a consequent use of high quality ball bearings, rather than glide bearings, results in substantially reduced friction resistance for all controls. This, in combination with the outstanding flaperon differentiation, enables the very smooth flight controls of the Antares.


Large tail surfaces with high aspect ratios and state of the art airfoils ensure perfect maneuverability in all flight and loading conditions while keeping empenna- ge drag at a minimum.


High extending, triple cascading Schempp-Hirth spoi- lers allow for steep and safe approaches with limited loss of lift. This has the effect that the stall speed hardly increases with the extension of the spoilers.


All these aspects make the Antares an extremely agile, but not “skittish” aircraft. The Antares 20E is stable in flight, but reacts communicatively to thermal activi- ties, and offers an agility comparable to that of 15m sailplanes. For example, a +/-45°-curve reversal at  115 kph / 62 kts takes only 3.2 seconds.

Antares 20E: the performance of open class – the handling of 15m-class