Grunau Commodore (oz16753)

About this Plan

Grunau Commodore. Radio control scale model sailplane. Wingspan 378 cm.

Quote: "Grunau Commodore, by Rudolf Wilhelm. About the original: The Grunau Commodore was a one-off model built by the Schneider company in Grunau/Giant Mountains and was intended as a high-performance glider for glider pilots who had completed training with the training glider and the training sailplane such as the Grunau Baby. It had a wingspan of 16 m, an empty weight of only 145 kg, and a glide ratio of 1:23. The airfoil was Gö 535 at the root and symmetrical at the tip. The wing and horizontal stabilizer were planked. The fuselage was entirely plywood-covered, while only the leading edge of the wing was. It is recommended to familiarize yourself with the construction methods of these old 'plywood boxes' before starting construction. Books [1] [2] and [4] are only available through interlibrary loan at any public library. [13] is described in FMT 4/82 and can be acquired for a donation.

Regarding the model: The only plastic parts on the model are bellcranks, Bowden cable tubes for the aileron bearings, and pin hinges on the elevator. This already indicates that it is a model for model builders. I tried to adopt the original dimensions and construction methods as closely as possible. Wing chord, rib spacing, frame spacing, etc., are reduced to a scale of 1:4.21 compared to the original. The reference was a three-view drawing, which is at a scale of 1:20 for the model. This resulted in a wingspan of 3.78 m. Only one measurement is incorrect: the fuselage height is approximately 2 cm too low, as I was initially unaware of the original airfoil. Since I had no experience with the old airfoils, I chose an Eppler airfoil section E 203 - E 193 - E 193.

Construction Instructions: Fuselage: Whether the fuselage was built with solid frames or entirely from stringers cannot be determined from the three-view drawing. I only used two plywood frames, namely the nose frame 1 and frame 4, because they give the fuselage its shape. The rest are exclusively stringers made of 5 x 5 pine or balsa. At the stringer joints, either filler blocks or plywood reinforcements are glued on to increase the gluing surface.

First, the fuselage sides, including the plywood corners, are made. If stringers need to be bent, a hot bending jig or clamps can be used. The side panels are glued to frames 1 and 4 while lying on their backs; then the ailerons and reinforcing corners are fitted. The fuselage spine (parts marked o - top) can then be glued on. The skin is made from 0.6 mm aircraft plywood. Either the planking is done frame by frame, resulting in an uneven but true-to-life appearance, or one large piece is used for planking, and the planking joints are then marked with a knife and pencil..."

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