Astral (oz16809)

About this Plan

Astral. Radio control thermal glider model. Wingspan 2770 mm.

Quote (google-translated): "Construction Plan. Astral. Thermal and Light Wind Glider for Radio Controlled Flight.

The construction plan for the RC thermal and light wind glider Astral, included with this issue of FMT, had to be reduced to a scale of 1:2.5 for printing reasons. The model built according to these plans has a wingspan of approximately 1600 mm, making it suitable as an A1 model and suitable for both free flight and RC flight. A 1- or 2-channel radio system is recommended for RC flight. The smaller version can also be flown as a motor glider: 0.3 to 0.5 cc engine. Except for ribs 40, 41, and 42 at the outer wing folds, every other rib can be omitted on both the wing and the tail assembly.

The dimensions given in the construction plan and description apply to the larger original version (wingspan 2770 mm); they must also be reduced by a factor of 1:2.5 when building the smaller model (rounding down).

About two years ago, our design team developed an RC glider for thermal soaring. To achieve good thermal sensitivity coupled with minimal sink rate, we applied the proven principles observed in the construction of free-flight models: low weight, low moments of inertia, a highly cambered airfoil, and a rearward center of gravity. To make such a model lightweight despite the integrated radio control system, it had to be larger than an A2 glider; we therefore opted for a wingspan of approximately 2500 mm.

Three nearly identical models were built in the development series - they differed only in their airfoils. The airfoil specified in the plans is a Wortmann M2; it performed better in our tests than the Eppler 387. The model weighs less than 950 g ready to fly with the radio control system installed. The performance demonstrated more than exceeded our expectations. In calm weather, the sink rate is barely greater than that of a high-performance free-flight glider.

The disadvantage of such a model lies in its low horizontal speed; it is also unsuitable for wind and hardly usable for slope soaring. However, this slow glider is particularly well-suited for precision landings. The model aircraft enthusiasts who participated in the RC rally in Kehl/Rhine were able to see this for themselves.

It should perhaps be noted before the building instructions that the 'Astral' is not a beginner's model, because to achieve such performance, the wood must be selected very carefully and expertly, and the model must be built very lightly.

Building Instructions:

The fuselage is constructed using the familiar sheet-and-panel (box) construction method. First, the fuselage planking (1 and 3) must be cut from good quality 2 mm thick balsa wood, and the fuselage side reinforcements (4 and 5) from 0.8 mm thick plywood. Side 1 is attached to the building plan with pins. The fuselage stringers (6 to 9) made of 4 x 4 mm balsa and the reinforcements (4 and 5) can be glued to the fuselage sides (2 and 3) according to the drawings. Once the cross spars (10 and 11) are fitted, the now-finished fuselage sides can be glued to the upper side 1. The formers 14 and 15 (2 mm plywood) and parts 13 can be fitted simultaneously. This creates a vertical box that rests on its top side. When everything is thoroughly dry, the nose (16) and the lower..."

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