Selestra (oz12334)

About this Plan

Selestra. Radio control thermal soarer, for 3 channels. Wingspan 3215 mm.

Direct submission to Outerzone.

Update 16/07/2020: Added article, thank to RFJ.

Quote: "Like thermals? build Roy Garner 's superb 128 in open class Selestra.

ENCOURAGED by the interest and bullying of fellow fliers John Sault and Bob Page, the dream I had been fostering for over a year became reality, and the Selestra was born. The concept was simple but demanding. I wanted an open class soarer with a good minimum sink, but with a nippy thermalling capability similar to the 100S class sail-planes so small areas of weak lift could be explored and used to the full. Another re-quirement was the ability to cope with moderate winds. Last but not least, it must be simple and cheap to build, for we all know the price of balsa!

With these in mind, the following specification was reached. Span 128in. with a generous area of 1015 sq in. Aspect ratio 14:1. Aerofoil section was the proven (and trendy) Eppler 205. Airframe was capable of being ballasted to give a wing loading between 6.8 oz/sq ft and 11 oz/sq ft plus. The construction of the Selestra conforms to the well trodden path of wooden ships having a wing construction very similar to my commercial Sunshine design.

As I drew the plan, John built from it. In fact John's building of the prototype at times overtook my draughting. The project was completed eight days later at three o'clock in the morning! Next day John flew the Selestra into seventh place at the Kidderminster Open Competition.

The need for a couple of modifications became apparent at this event, namely an increase in fin area and wing incidence.

With the design finalised, we have had many happy hours flying our Selestra and hope you have the same. Board cleared? Off we go!

Construction: The fuselage has a straightforward con-struction with plywood side panels and balsa sheeting top and bottom. Designed width of the fuselage can be adjusted to suit your own airborne pack and the parallel sides at the wing junction allows the use of other wing panels if so desired.

Firstly, trace one main fuselage panel onto 1/16th plywood, marking former positions, wing and tail rod holes etc., as you go. Care-fully cut out the panel with a Stanley knife. Use this as a template to produce the second panel. Pin the panels together and mark the former positions onto this second panel. Drill the wing and tailplane rod holes, rudder cable outlet slots and sand the two panels equal around the periphery (watch out for splinters!) before separating the panels (Fig. 1).

Lay panels flaton building board, one right - one left! Using PVA, glue the 1/32 ply-wood doubler onto each panel and add the 1/8 x 1/4 and 1/8 sq spruce framing.

Cut out formers 1, 2 and 3 from 1/8 plywood and construct formers 4 and 5 over the plan. Note that formers 3, 4 and 5 may be en-larged to suit your radio installation, but they must all be the same width.

Glue formers 3, 4 and 5 into position at 90° onto one panel. Fig. 2 (note F3 yet to be added.)

On the other panel, construct the fin assembly by gluing 1/4 square stern post and 3/32 x 1/4 false LE and adding ribs T1, 2 and 3. Add the 1/4x 1/8in. spruce elevator pro-file stubs to each side then drill and slot them for elevator horn assembly. Trim down a commercial tail horn se it will fit and move freely between the plywood side panels. Fit a clevis onto the pushrod of a 48in. long control snake and clip the clevis to the tail horn. Trim the rear stub former to accept the control snake outer and epoxy outer tube onto one side panel. When dry slide the inner pushrod and horn assembly into the outer, epoxy the horn pivot bearer in position and check for free movement (Fig. 3). Thread rudder cables through outlet slots and tape the loose ends onto the cockpit sides.

Glue fuselage sides together, secure the elevator bearer and when all is square, clamp the rear fuselage together with clothes pegs. Check that the rudder cables and elevator controls move freely and put onto one side to set. (Fig. 4).

When dry, add formers 1 and 2 and stub formers top and bottom, note sub former 'Y' is the same width as formers 3, 4 and 5. Allow the fuselage, from 'Y' back to the fin to curve inwards and form its own natural line (Fig. 5)..."

Supplementary file notes

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