A crack in a construction drawing is drawn on the drawing board in order to have the dimensions of the individual parts and how they fit together on site during production and assembly. This means that lines are drawn on the drawing board that symbolize the top of the workpiece as well as sections and cutouts. This method used to be common in all areas in which excessively large components are used, especially when several copies of a workpiece have to be made or the construction is complex. This technique can also be used to build a grid by stretching strings at regular intervals and transferring the grid to the construction drawing.
It owned places were smoothed and in historical times yardstick and chalk line the design drawing unraveled - hence the name, the flies'. Tightly tensioned cords are used for this, as you can very quickly create a straight line between two points with a cord and use it as a compass . This means that all of the compass-and-ruler geometry is available.
The tear floor must be level so that the cracks can be transferred to the blanks to be processed with an angle iron or other suitable measuring tools.
Because the production and assembly of these parts were also time-consuming, roofed racks were probably developed early on. In late industrial times, cord floors were found as a large hall, usually an attic in a production hall with its own skylight .
Today, the dimensions of the parts are increasingly transferred directly from the CAD / CAM or CAAD program to the automated production machines , or are output with special plotters , so that the cord floor is hardly needed in practice.
Construction drawing boards
The method is already known from classical Greek temple building, where a smoothed layer, the euthyntery , was applied to the foundation of the building, the stereobat . In addition to structural and metrological purposes, this leveling layer was used in particular to draw up the floor plan of the building. Lace-up bottoms can also be found in the early architecture of the Orient and the Far East.
It is not exactly known since when these places were also widely used on site for tearing open the building structure and its individual parts (an architectural drawing of the temple of Didyma carved into the wall dates to the 3rd century BC), certainly since the early In the Middle Ages, the first version of the plan was made on parchment, paper, or wood (the drawing board ). The offset plan , in the timber construction plan , then had to be available in natural dimensions on the construction site. Various types of stencils were then drawn from these (measuring boards) .
In the Dombauhütten the Gothic , the method has been proven to spread on suitable soils already inside the unfinished building, the large rods of the vaults and tracery untie. From written records it can be assumed that these tear floors were designed as wooden platforms. For this purpose, the soil was then covered with a thin sand - or screed layer of plaster covered. When the Schnürboden was fully drawn, another layer of screed / plaster was applied. There are also lacings in red chalk and scratches with a scriber in stone. Occasionally, there are "drawing boards" vertically on walls.
In a few churches from the High Middle Ages, the original lace floors from the construction period have been preserved, primarily in France ( Chartres , Reims , Soissons , Noirlac , Clermont-Ferrand , Limoges , Saint-Quentin , Narbonne ), but also in York , Wells , Orvieto , Trogir (Cathedral); on the floor of San Paolo fuori le Mura in Rome, Giacomo della Porta tore the cross-section of the dome of St. Peter .
In addition to church construction, the method was probably also widespread for secular buildings and especially in carpentry and joinery until the 20th century - so it can be assumed that in early construction, in addition to stone masons , wood construction was also widely planned on the drawing floor. It was used in stone and wood construction for roof constructions , stair nosing profiles , shuttering boards , wreath timbers , and especially in vault construction - also in bridge construction - for the construction of the teaching arches as well as the falsework .
Lace floors in shipbuilding
Especially in shipyards , the curves of the frames , bulkheads and other parts, as well as the deck plating, are recorded in the original size in the attic of the shipbuilding hall from the information in the drawings . This floor is also called mall floor . Also sailmakers used string floors for their pattern.
- Konrad Hecht: Measure and number in Gothic architecture . In: Treatises of the Braunschweigische Wissenschaftlichen Gesellschaft . tape XXII , no. 2 . Friedrich Vieweg Verlag, Braunschweig 1970, OCLC 603368407 .
- Klaus Tuchelt , lecture. Quoted from Ref .: Ulm: A late Gothic “drawing floor” . S. 128 .
- Benno Ulm : A late Gothic "drawing floor" in the parish church in Hörsching . In: Ulm, Kleinhans, Prokisch (Hrsg.): Oberösterreichische Heimatblätter . tape 37 , 1983, pp. 121–132 ( online (PDF) in the forum OoeGeschichte.at).
- Rudolf Koch: Supplements to the exhibition "Gothic Treasures Upper Austria" . Linz, Schloßmuseum 2002, chap. Construction operation and construction technology - examples of the art of stonemasonry ( memento from February 23, 2010 on WebCite ) (with a picture of the reproduction of a drawing floor, Gothic exhibition 2002).
- Konrad Hecht: Measure and number in the Gothic architecture. In: Treatises of the Braunschweigische Wissenschaftlichen Gesellschaft. tape XXII , no. 2 , 1970, p. 240–250 (quoted from: Ulm: Ein late-Gothic “Reißboden”. P. 126 f.).
- Entry falsework. III. General arrangement of the L. In: Dr. Baron v. Röll (Ed.): Encyclopedia of the Railway System . 2nd Edition. tape 7 , 1915, pp. 80 , col. 2 ( zeno.org ).
- Entry tear open. In: Otto Lueger : Lexicon of the entire technology and its auxiliary sciences . tape 1 . Stuttgart / Leipzig 1906, p. 363 ( zeno.org ).
- Entry Schnürboden. In: Lueger: Lexicon of Technology . tape 7 , 1906, pp. 770 ( zeno.org ).