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DESIGNE AND CONSTRUCTION SZD-56-2"DIANA 2" PDF Print E-mail
Written by Administrator   
sobota, 17 czerwiec 2006
A brand new wing design has been developed for Diana-2. Based on the aerodynamic concept applied in Diana-1, Krzysztof Kubrynski, Ph Dr Eng developed the wing with sophisticated non-linear geometry, and wing to fuselage transition optimized for entire operational envelope of the sailplane. It’s worth noting the entire process has been accomplished with the software developed by Mr. Kubrynski.
Developing the most aerodynamically efficient components of a sailplane (wing with optimal airfoils, tail plane, and fuselage shape) does not assure the desired characteristic of a complete configuration, when combined in a 3-dimensional body, due to mutual interaction (aerodynamic interference) between the components.
The most effective method of aerodynamic design is direct optimization. The method allows defining the geometry of a complete sailplane, resulting in the close to optimal 3-dimensional lay-out and minimized aerodynamic drag. Unfortunately, the available implementations for calculation of aerodynamic characteristics are not accurate enough for practical application on objects as complex as complete sailplane. Considering those limitations, design of Diana-2 components was first optimized, and then adverse effects of interference were eliminated with method of reverse design.
When designing components, solution for pressure distribution resulting in desired aerodynamic forces and moments, as well as the correct shape of boundary layer (i.e. location of transition point, prevention of separation etc.) was found. Geometry generating this pressure distribution was defined in second step.
The goal of aerodynamic design is to create sailplane geometry generating highest possible performance within operational envelope, which includes low stall speed, low minimum sink, and good glide ratio at high flight speeds. More importantly, benign stall characteristics, aileron efficiency, correct characteristics in turns [circling], and low sensitivity to wing surface contamination (water and insects) are also objectives of aerodynamic design.



Contribution of wing drag is approximately 90 percent of total sailplane drag at low airspeeds, and falls down to around 60 percent at high airspeeds. Obviously the primary goal of aerodynamic design is reduction of the profile drag and induced drag. Airfoils with maximally extended range of laminar flow have low profile drag. As the flow changes spanwise, to optimally adapt to the local flow conditions (Reynolds number and lift coefficient), the airfoil shape should be individually designed for each wing cross-section. Shown below is a diagram illustrating effects of the new airfoil design in comparison to airfoil of Diana-1.
Wing planform and application of winglets can minimize induced drag with optimum spanwise lift distribution.
Series of numerical iterations were performed during design of new Diana. They allowed us to analyze flow and optimize design of 2-dimensional wing airfoil and complete 3-dimensional configuration of the sailplane. As a result the wing planform is non-linear with continuously changing airfoils over entire span. NACA ducts on bottom surface of flaperon supply pressure to 0.6 mm diameter orifices [approximately 1700], located on lower wing surface, forward of flap leading edge, creating pneumatic turbulizer.
Sophisticated aerodynamic design of Diana-2 forced state of the art manufacturing techniques to build the sailplane. Diana-2 has been fully modeled in UNIGRAPHICS NX – high end design software widely used in aerospace. Wing tooling masters [positive models with all reference points and parting planes defining female mold] have been CNC machined from high density tooling board offering excellent geometrical stability.









Regardless of all technological advancements offering highly automated design and transition into production, hand work and craftsmanship built by exceptional, extensive experience remain the key-points in construction of prototype. This approach remains unchanged and is still carried on by world most successful sailplane manufacturers.
CNC machining of wing model combined with first rate materials has raised initial cost significantly but, when compared to traditional methods of manual fabrication, the total cost to produce such complex wing geometry has turned out lower. The biggest advantage that has attracted us was reduced time and precision unattainable with manual methods.



The tool masters of new wing molds have been produced within 0.1 mm tolerance to assumed theoretical shape, with wing panel length of 7200 mm and average chord nearly 600 mm.
Horizontal reference plane built into wing tools allows for correct reproduction of the complex wing geometry with non-planar chord surface. Lay-up molds, built from thermally stable homogenous material, guarantee accuracy of shape within the required tolerance.


The production tooling has been designed to provide full interchangeability of parts assured by locating features built into mold of every component and subassembly later installed in the wing.
Geometry of production wing is maintained at the highest accuracy with application of paint on the tool surface before lamination of skins begins. After de-molding, without any surface finish, the prototype wings looked like this :







The aerodynamic analysis indicated change of wing position in relation to fuselage, so geometry of wing to fuselage transition had to be modified also. To reduce parasite drag, trailing edge thickness had to be maintained at 0.8 mm, constant throughout the full wing span. Regardless of its manufacturing and service disadvantages, this goal has also been accomplished.
Last Updated ( środa, 09 sierpień 2006 )
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