The strak is a type of graphic representation based on the representational geometry, which is used in shipbuilding , automobile construction and aircraft construction . The name is derived from the English word "strake", which describes a continuous plate corridor .
A definition for this could be: Finding an aerodynamic shape in terms of design, e.g. B. a fuselage or a wing, if only a few flat, vertical, parallel cross-sections of the volume are given.
The 3D model is divided into frames and sents.
Strak in automotive engineering
The look of a vehicle is the geometric representation of all customer-visible surfaces in the interior and exterior, taking into account all technical and aesthetic requirements.
In practice this means that the strak department (short: Strak ) forms the bridge between the design and construction departments . The design department delivers a 1: 1 plasticine model ( clay model) as the design result. This model can be scanned optically with a 3D scanner or mechanically (out of date) with a coordinate measuring machine. The touch, also called scan , is the template for the road division and consists of a point cloud in space ( see also rapid prototyping ). The point cloud is triangulated for visualization . A facet model is obtained from a large number of triangles.
The straightening department now designs free-form surfaces of the highest quality ( Class A ) in the CAS system such as ICEM Surf , Autodesk Alias ( see also Alias ) or CATIA X V5 . The touch serves as a reference in the room. In the strak, the surfaces of the plasticine model are reproduced in a higher quality. Bumps and S-punches are "extracted". Ambient light reflections (highlights) on the surfaces are optimized.
In addition to the design intentions, construction requirements are also implemented. The surfaces must be demouldable (no undercut, see mold making ) and there must be enough space for construction elements and neighboring components . If possible, tool dividing lines should not lie on the visible and base surfaces. Results from the aerodynamic studies are incorporated. The surfaces created by the strak are modeled into complete components in the subsequent construction process.
Due to the rapid development in the field of computer-generated image creation , the physical model is increasingly being replaced by virtual models ( see also virtual prototyping ). The starting point for the strak is therefore often no longer the plasticine model. Rather, design and construction processes run in parallel, and the road is created as part of the preparation of construction data for visualization with CGI applications such as Autodesk Maya , Autodesk VRED Professional or RTT DeltaGen.
Strak in aircraft construction
In aircraft construction, the word strak is often used when different wing profiles are used along the span (Profilstrak). Normally, a more arched and thicker inner profile can be "stiffened" via one or more intermediate profiles to a symmetrical profile at the wing tip. (see also aerodynamic offset ). The profiles at the transition points correspond to the original profiles (e.g. from a profile catalog), whereas all intermediate cuts result from the course of the strake. Computer programs that calculate and output these intermediate profiles are mostly used in model aircraft construction today.
At the time of wooden aircraft construction in spar-rib construction , the wing ribs, after they were glued to the spar, were sanded with a so-called straklatte (sanding lath), the so-called "abstraction". To do this, align the ribs in between using two reference ribs with the original profile. In this way, it is possible to compensate for minor structural inaccuracies in the ribs and to avoid distortions of the intermediate profiles. Then the framework was planked with plywood or covered with fabric. In contrast to the straklatte in shipbuilding, the straklatte in aircraft construction is stiff and straight.
A cabin glazing (hood) that is not separated from the fuselage contour, but is integrated into the fuselage contour, is referred to as a “recessed hood” (into the fuselage contour). Almost all modern GRP gliders are equipped with a retracted canopy.
- Kemp, Peter (ed.): The Oxford Companion to Ships and the Sea . 1st edition. Oxford University Press, Oxford 1976, ISBN 0-19-211553-7 , pp. 870 .