The SALpeter represents the latest fine tuning of the proven Aspirin concept. Improvements were particularly strived for in the following points (in order):

• dead air sinkrate

• glide ratio against the wind

• launch height

• climbing in thermals

For the therefore a set of five different airfoils along the span was designed, matched to the local Reynolds numbers, lift range and thickness constraints. The Aspirin airfoil was still constructed for a larger relative thickness of 7.3%, to be able to compart reasonable servos without exterior parts and achieve an excellent stiffness-to-weight ratio.
With the AH160_9 series developed in month-long fine work the luxurious reserves in the negative lift range were reduced to the benefit of the most often used region. Relative thickness became smaller in the main part of the wing accordingly and was only kept where the servos are mounted.

Airfoils again were equipped with a contour kink and by this optimized for two preferrable settings (0/2 deg). In slow gliding the top surface remains smooth to avoid unnecessarily large laminar separation bubbles and reduce pressure drag. The kink in the lower surface does not lead to early transition then and the thin separation bubble can even reduce friction drag somewhat.
In fast flight the lower surface is made smooth, to keep the boundary-layer laminar up to nearly 100%. The shape parameter development was optimized in such a way, that the laminar drag bucket reaches to lower lift coefficients then compared to the Aspirin.
When the Aspirin was flown very heavy (> 310 g) in wind and with a too negative flap setting, sometimes a loss of glide performance returning from thermals could be noticed. It was not given to everybody to find the “sweet spot” concerning flap setting, ballast and velocity. The SALpeter offers a significantly wider optimum, with lower off-design performance loss.

The outer wing was kept a little more narrow and less swept than at the Aspirin, to optimize the last nuances of flight characteristics. For our taste the Aspirin sometimes tended a little too much to stalling in the middle of the wing and take down the nose subsequently. This gentleness was not needed for the experienced pilot.
Making this change of course it was taken care of adjusting stability and circling characteristics such, that the competition pilot does not need to be too fixed on the model but has a good indication of thermals.
Accordingly an intermediate aspect ratio as the optimum compromise concerning stiffness, Reynolds number and mass-wing-loading ratio for best allround performance in typical wheather conditions was chosen. A glider with a huge operation spectrum should be made, one which always works.
The vertical tail of course is profiled asymmetrically again, to reduce the yaw excursions after release as quickly as possible. The Aspirin sometimes showed hardly noticable yaw wiggles in slow flight, which were removed on the SALpeter. Nevertheless the airfoil is still strongly oriented at the HT23 and delivers high maximum lift.
Compared to the Aspirin span was marginally increased from 240 to 244 mm and also area is hardly changed with 1.70 dm². Despite that effectivity was increased, yet without producing too much mass, inertia and drag with a too large vertical stabilizer. Simultaneously core volume was reduced saving mass. Of course again each a left and right-hander version is available.

Also the elevator was slightly enlarged and adapted to the larger lift slope of the wing. The minimally lifting airfoil creates an even more harmonic slow flight behaviour, whereat it was daintly paid attention to not cause drag penalties in launch.
Dihedral was increased a tic to 6.2 deg, to allow circling with minimal stick inputs. It is not detrimental to launch heights at all. And upon floating in quiet air most of the corrections can be made with rudder only.

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Franz mit Aspirin 2006 vor dem
Airbus-Hauptquartier in
Toulouse nach einem Gespräch
in der Chefetage über
unsere Leichtbauerfahrungen....