Panamarenko
Donderwolk [Thundercloud], 1970-1971
The Donderwolk (Thundercloud) is a strong but light aircraft, with hybrid characteristics. It at one and the same time a propeller plane, driven by a motor positioned at the rear, and a glider - provided with a delta-shaped Rogallo-wing. The closed, compact cabin, that resembles that of an old fighter plane, is made of aluminum. The dome is of plexiglas. Above the craft's hull there is a delta-shaped wing, the so-called 'Rogallo-Flexwing', named after the American NASA engineer who developed the Flexwing to help space capsules return safely to Earth.
'For my Rogallo-wing, I looked for a material that looked like a kind of membrane. That turned out to be a cotton impregnated with rubber. Because of the rubber's dark color, it looked like a thundercloud. My mother sewed that sail together on her own small sewing machine. That's the only thing she ever did: sew those slits for inserting the delta's tubes.' - Panamarenko
The wing is steerable with the aid of traction cables controlled from the cabin via two levers. The sail's main beams are constructed so that the wing can tilt forwards and backwards as well as left and right. A go-cart motor is fixed to the rear of the apparatus, and it has a capacity of 10 PK at 10,000 revolutions per minute. The propeller has a diameter of 80 cm. and makes 5,000 revolutions per minute. The gas-feed to the motor is controlled via a third lever in the cabin, and there is also a place to store a small, leather toolkit. The interior of the cabin is lined with felt.
'That was to dampen engine noise, and also and mainly to make the pilot's seating more comfortable. Otherwise the metal and the screws made it too painful for the knees.' - Panamarenko
From two early drawings of this aircraft (dated 5 October 1970), it appears that Panamarenko originally wished to construct a human-powered device. A bit later, he changed that: on two drawings from 1971, he represents it as propeller-driven.
'In the catalogue of Documenta V, I added this laconic comment with regards to the Donderwolk: 'Strong, light aircraft - untested'. This was to nip overzealous questioners in the bud, those who always want to know if I really had tried it out.' - Panamarenko
(source: Hans Willemse and Paul Morrens, in: 'Copyright Panamarenko', 2005)