Beta (oz7557)

About this Plan

Graupner Beta. Radio control sailplane. Wingspan 1970mm.

Direct submission to Outerzone.

Update 8/4/2023: Added kit review from Aeromodeller, Jan 1980 (RC Sport Flyer column), thanks to Aeronorm's post on HPA, see https://www.hippocketaeronautics.com/hpa...

Quote: "RC Sport Flyer, by Chris Pinchbeck. Graupner Beta: A comparatively recent introduction to the UK market, this model is primarily designed for thermal soaring but is also suitable for slope soaring in light to medium wind strengths. It can also be converted to a power-assist soarer using Graupner parts 164 or 62. The 1970mm span wings are in two parts for ease of transport. Tail surfaces are permanently attached.

This is a builder's model, and unless you enjoy this aspect of the hobby, look elsewhere for your glider kit. The quality of the woad is excellent with some of the best die cutting I have ever seen. There are a number of ABS moulded parts to fabricate the wing roots, a nicely moulded cockpit and canopy, all linkages and rod-in-tube control 'snakes'. Glues are supplied together with covering tissue.

The plan is very clear and there is an overlay to show radio installation details. The German Instruction book contains stage photographs and a very useful 'exploded' drawing of the finished model; this detail is cross referred to the English translation. Building instructions are concise and very detailed.

Fuselage assembly is based upon the fuselage bottom sheeting being pinned to the plan. Formers, corner support strips and sides are then built up on this base. The control snakes are fitted before top sheeting. Three gauges are supplied which ensure correct alignment of the forward fuselage sheeting, and also correct incidence for the wing seat. The sheet tailplane and fin are fitted, then the whole fuselage carved and sanded to shape.

Wing assembly starts by building up the root area using the ABS parts. The tubes for the wing join dowels are held in these plastic mouldings which ensure correct positioning of the dowel tubes. The rest of the wing is then built on the board in a conventional way. The top and bottom sheeting for the wing root area is die cut. Since these areas differ slightly, it is essential that the various parts are clearly identified before cementing in position.

The fuselage and tail group of the review model were given two coats of thinned clear dope, sanding between coats. Lightweight tissue was then applied by brushing on a further coat of dope. Two coats of sanding sealer, rubbing clown between and after applications, completed the preparation. Two coats of Humbrol white enamel thinned with white spirit were brushed on to give the final colour. After application of the transfers, a black cheat line was positioned. The wings were covered in white and transparent yellow Solarfilrn, white from leading edge to main spar, transparent yellow from main spar to trailing edge. The join was hidden under an 1/8 in wide black trim tape.

There is not a lot of room for the servos and although two sided tape could be used, I decided to wedge them in position using a combination of balsa wood and foam packing. With the receiver in its bay and the battery in the nose, lioz of lead were required in the nose to achieve the correct centre of gravity position. Finished weight with Sanwa radio equipment is 2 lb 7-1/2 oz which gives a wing loading of approximately 9-1/4 oz/sq ft.

The model flew well off a towline, gaining height with no need for elevator control. Directional stability was good with only one jab at the rudder needed to keep her straight. With little or no thermal activity on the test day, flight duration was not outstanding but the glide path gradient was not steep, and Beta seemed to glide on for ever during the latter stages of the landing approach. Subsequent flights proved that the stall is gentle with no tendency to drop a wing. Bungee launches were not attempted since I feel that the low hook mounting would probably need 'beefing up',

Off the slope with an 8mph wind, Beta floated around when other models were grounded. Its docile performance coupled to good control response were evident once again.

Conclusion: An excellent kit, well presented, which builds up into an attractive model with good inherent stability and control response. Ideal for the beginner who enjoys building."

Supplementary file notes

Review.

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