Plan file details
Graupner Cirrus. Radio control scale model sailplane. Wingspan 3m. Scale is approx 1/6. This kit used a ready-moulded ABS plastic fuselage.
Quote: "The model version of the Cirrus sailplane offers a wingspan of 118-1/8 in, approximate scale is 1/6th.
The design of the model required several deviations from the dimensions of the fullsize machine in order to gain optimum flight characteristics and performance.
The photos show the sailplane owned by the Fliegergruppe Wolf Hirth of Kirchheim/Teck. This plane carries the name 'Rolf Kuntz'. It sports a slightly larger wingspan than the standard version.
A prominent feature of the model's wing is its high aspect ratio. With a ratio of 1:17 it closely resembles the fullsize ship's shape. Thanks to its torsion box leading edge and the appropriately selected airfoil shape the wing is nonetheless torsionally stiff and strong.
In the case of the canopy no attamept has been made to duplicate the intersection between the fixed and the sliding section of the canopy. He who wishes to incorporate such detail may paint it on, using a non-shrinking varnish (such as Alyyfiz enamel varnish, ident no 1470). Refer to plan for details.
As a departure from fullsize practice the model has been designed with a full floating stabilator. This is an adventage from both a constructional and an aerodynamic point of view. In the case of the all moving ailplane the entire surface is used for control about the transverse axis. It is movably mounted and operated via a control horn in the case of the radio control model.
Just like its full size counterpart the Cirrus model is not a dyed-in-the-wool aerobatic model. This is easily recognised from its configuration.
As the model will be generally flown without aileron control, a dihedral angle of 6° has been selected as suiting its wing span best. Wing attachment points at the fuselage are designed for this dihedral angle.
But even if equipped with ailerons the Cirrus is incapable of flying rolls. In this case the ailerons must only be used for attitude control and to initiate circling flight.
Attention: If you are going to incorporate ailerons, please do read the R/C Installation instructions first. For the model equipped with ailerons the dihedral angle may be reduce to approx 4°. To this end the four wire prongs (104) must be bent accordingly. The gap formed by this modification between fuselage and wing panels should be fulled by a conical false rib..."
Note this kit used a ready-moulded ABS plastic fuselage, but see Cirrus Fuselage (oz9876)
for a plan showing alternative built-up balsa replacement fuselage design, by Trevor Faulkner.
Update 10/04/2018: added kit reviews from RCM&E December 1969 & Radio Modeller November 1969, thanks to RFJ.