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Ich habe verstanden.

Snow White slowly comes alive

Veröffentlicht am 28. September 2015
Zugriffe: 4549

http://UL-Segelflug.de/images/TS_Schneewittchen-Grossmodell.jpgLike this -or similar like this- Snow White could appear, once she comes alive. Snow White SW-1 will be a Motor glider, designed and build by German Dr. Andrés Chavarria-Krauser, corresponding to German LFT-L (120 kg-class, similar to FAR-103). A radio-controlled model 1:4 for flight-tests is already in operation since about two years. Since necessary flight-tests are mainly completed, Andrés works at step three of his design- and build-program. As Andrés is a real scientist, he sure works very meticulous the scientists way:

1. Build of a radio-controlled plywood model, scaled down 1:4 for all sorts of flight-tests
2. Build of different wing-ribs and other parts for strength-testing
3. Build of a Wing-center Mockup (seating-box) original size 1:1
4. Build of the final Design, as shown at the drawing below

The construction itself is a Horten-like Flying-wing with common rib-constructions made of wood and carbon.

http://UL-Segelflug.de/images/HT-Schneewittchen-Dreiseitenriss-Copyright-Dr-Andres-Chavarria-Krauser.jpghttp://UL-Segelflug.de/images/GT_Schneewittchen_Grossmodell_Flugerprobung_0645.jpgSnow White SW-1 scaled 1:4 test-flying by the designer and builder, Dr. Andrés Chavarria-Krauser, at a model-airfield near Heidelberg/Germany

Once finished full-size, Snow White will have a remarkable Wingspan of 12,5 meters (41 ft), a Empty-weight of 103 kg (227 lbs), a MTOW of 240 kg (529 lbs), a Glide-ratio of 25 at 82 km/h, a lowest Sink-rate of 0,78 m/s at 65 km/h and a Minimum-speed of 54 km/h (29,15 kt).

To be independent getting into the air, Snow White will be provided with a Geiger HPD10 Electric-drive and a H25K-Propeller (foldable), which brings the motor glider to max. 110 km/h at horizontal-flight and a cruising speed of 74 km/h. The max climb-rate is calculated with 1,95 m/s at 68 km/h. For sure, all those are very impressive values.

Meanwhile, Andrés has already finished phase 2 of his construction-plans, while he is experimenting at phase 3 with his full-sized Mockup of the center-wing section.
And that is how the "seat-box" inclusive cockpit-spacing looks like in original-size. It obviously cannot been recognized at first view, also the airfoil of the center-wingbox has a curved shape, which contributes to the overall lift of the Horten-wing. The airfoil was designed and calculated by Andrés himself and it has been extensively tested in several large-scaled model-planes before. "The airfoil has a semi-laminar profile with about 40% laminar track, whereby the turning point obediently moves at a high angle of attack to the front. This makes a stall very harmless" as Andrés explains.


But all this extra effort and time to build a full-sized Mockup, he does not do it for fun. He does this for some very pragmatic reasons. As Andrés is convinced, technical drawings are simply made to design and build machines, but not for interactions amongst men and machines.

To his personnel conviction, probably the most difficult questions in aircraft-construction are as follow: "How does the pilot fit in to the cockpit? Does he feel comfortable in his cockpit-seat during several hours? Does he has easily access to all instruments and operating units? How is the visibility out of the cockpit and around?"

To receive answers to those questions in advance, he did build his Mockup of the center-wing section, inclusive a simple and easy to adjust cockpit-seat. Thereafter, he invites different people to sit down in the box and commenting their personal feelings and impressions. Part of those "test-seating sessions" of course, is also done by his wife.


In the next step of testing, he installed curved parts as an outer cockpit-contour, which additional limits the space in the test-cockpit.


Also of interest is the segmentation of the wing into five segments, knowing that this will increase the Empty-weight of Snow White at the end. Sure something, 120 kg-designers try to avoid, to keep the Empty-weight down as low as possible, since this is the absolute limit for certification.

But due to transportability, splitting up the wings in several parts is common practice, while the additional weight must be saved during constructions at other places. Another reason for splitting up the wing in five independent parts, is the size of 5 m length in the workshop of his house.


A real interesting Flying-wing project indeed, which will be followed and reported by UL-Segelflug.de in the near future.

(See also Blog about other Flying-wing projects)

Build-progress of Snow White SW-1 can be followed and commented in the Webblog of Andrés which is published in English.

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