Apex F3L 2m RES Glider

The APEX F3L is the latest 2m RES glider development by Stefan Schweiger, designer of the internationally proven Purito. Following four years of continuous development and testing, the APEX represents a systematic refinement of the Purito concept with emphasis on aerodynamic efficiency, energy retention, and performance in wind.

The aerodynamic layout and airfoil system were designed by Eser Kismir.

Structure & Construction
The wing utilises a tubular main spar layout with construction principles derived directly from the Purito platform, for ease and accuracy of assembly. Structural design prioritises torsional stiffness, load consistency under launch, and repeatable build accuracy.
The kit follows the established Purito construction methodology and is optimised for precise, low-tolerance assembly.

Ballast System
Internal ballasting is implemented through the wing spar, positioned directly at the model’s centre of gravity (CG).
Typical flying weight: 380–480 g
Additional ballast capacity: up to 90 g, installed via the canopy
This configuration allows rapid mass adaptation without CG shift.

Flight Characteristics & Measured Performance
The APEX has been validated through competitive flying and direct comparative testing against lightweight Purito setups.

Launch performance
- Identical launch heights in calm conditions
- Slightly improved launch altitude in headwind

Glide & penetration
In zero-air comparative tests from equal launch height:
- Flight time: no measurable difference
- Distance covered: 30–40% greater for the APEX
This confirms higher average airspeed at equivalent sink rate.

Wind performance
The airframe allows operation at a significantly higher base speed while maintaining controllability, providing improved penetration and working range in moderate to strong wind.

Geometry & Specifications
Wingspan: 2000 mm
Wing chord: 190 mm
Tip chord: 104 mm (5 different airfoil sections used across the span)
Wing area: 34 dm²
Wing configuration: 3-piece design
Airfoil: Proprietary in-house design by Eser Kismir
Fuselage length: 1280 mm
Ready-to-fly weight (F3L version): approx. 380–420 g

The APEX is currently available in a pure glider F3L configuration only. An electric version is in development and will follow soon.

For more info and a very nice build log see this RCGroups thread.