Fir wood
| Fir wood | |
|---|---|
 |
|
| Tree species |
Silver fir , sea fir and others |
| origin |
Eurasia |
| colour |
light reddish-white to yellowish-white with a gray-violet to bluish shimmer (darkening) |
| Material properties | |
| Bulk density mean | 410 kg / m 3 |
| Raw density limit values | 320-710 kg / m 3 |
| Axial shrinkage | 0.1% |
| Radial shrinkage | 3.8% |
| Tangential shrinkage | 7.6% |
| Flexural strength | 68 N / mm 2 |
| Compressive strength | 40 N / mm 2 |
| tensile strenght | 80 N / mm 2 |
| Thermal conductivity | 0.098 W / (m K) |
| Fuel properties | |
| Calorific value | 16.2 MJ / kg |
As fir wood is wood of the fir (genus Abies ) designated as the BSP. also spruce , pine or larch wood belongs to the coniferous woods . In Europe and large parts of North Asia, this designation almost exclusively refers to the wood of the silver fir ( Abies alba ), more rarely the coastal fir ( Abies grandis ) from North America . Internationally, there are a number of other species whose wood is used for different purposes.
The range of applications includes, above all, its use in paper and pulp production , as construction and furniture wood for indoor use and as firewood .
properties
Fir trees are comparable to spruce trees in terms of their growth. They grow very straight with a solid, cylindrical trunk with few branches in the lower areas ( knotless ). The trunk lengths here reach up to 20 meters with a total height of the tree of up to 50 meters, the diameter is 0.4 to 1.2 meters. In the open, the trees become more voluminous with significantly greater knots. The wood is light reddish-white to yellowish-white with a gray-violet to bluish shimmer, with heartwood and sapwood not differing in color. The annual rings are clearly separated from each other, with the color changing continuously from light early wood to dark late wood , the annual ring boundaries are clearly defined. In contrast to other softwoods, they do not have any noticeable resin channels and pockets, which means that the wood can be macroscopically differentiated from that of spruce. The branches represent another difference: while the branches of the fir tree usually protrude horizontally from the wood and leave correspondingly round knot marks, those of the spruce are oblique and the marks are oval.
Fir wood also differs little from spruce wood in terms of its physical properties, but due to its optical properties and brittleness as well as the harder and more frequent knots it is used less in the construction and furniture sector and is preferred wherever the resin content of the spruce wood is bothersome . It is very soft with an average bulk density of 450 kg / m 3 and a moisture content of 12–15%. The mechanical properties of the wood are very good for the low density and are comparable to those of spruce wood, which makes it usable as building and construction wood.
However, untreated fir wood is not very weather-resistant. If it comes into contact with the ground, it degrades quickly; for outdoor use, the wood must be treated with chemical wood preservatives . The higher moisture content of the wood compared to spruce should be taken into account, especially if both woods are processed together. In areas where the wood is constantly exposed to moisture, fir wood is more durable than spruce wood. The processing of the wood by sawing, planing, milling and other techniques is possible without any problems, the connection with screws and nails as well as glue is problem-free, only logs with larger knots and reaction wood can have a disadvantageous effect. Paints, glazes and stains can also be used without any effort; in comparison to spruce wood, fir wood is well resistant to alkalis and acids.
use
Material use
As sawn timber, fir wood is usually traded and used together with spruce wood as a mixed range of spruce / fir, and the fields of application of both types of wood are almost identical; both woods are very similar in their properties. It is processed in the form of round timber , sawn timber such as boards and glued laminated timber and as veneer wood . At the same time, it is an important wood for the production of wood-based materials such as plywood , glued wood , chipboard and fiberboard .
Fir wood is used almost everywhere as building and construction timber, both in interior construction and in exterior applications. It is used accordingly in house building for roof structures , for wood cladding, railings, stairs, skeleton structures for walls and ceilings, windows, doors and gates; however, due to its greyish color and frequent splinters, it is not used that often for floors. Particularly in earthworks and hydraulic engineering, it is preferred to spruce due to its better moisture resistance. Because of this property, it was also used in shipbuilding, especially large straight trunks, as they used to be common in the Black Forest, were valued as masts. In furniture construction, fir wood is used both in solid form and in the form of wood-based materials as blind wood and main wood for simple furniture. In addition, there are a number of other applications such as ladders, concrete shuttering boards, wooden paving, fences, posts, playground equipment and many more. In the packaging area, fir wood is used to build boxes and pallets as well as to produce wood wool .
A central use for the wood of the fir and other conifers is the manufacture of paper and pulp. Due to the longer fibers compared to hardwoods, their fibers felt more easily, resulting in a higher strength of the paper.
Silver fir veneer
Trunks of silver firs from Gersbach (Schopfheim) support the largest self-supporting wooden roof in the world on the exhibition grounds in Hanover.
Energetic use
Fir wood with a calorific value of 4.5 kWh / kg or 1,400 kWh / rm also plays a central role in the area of energetic use , both in the form of logs for house firing and in the form of wood chips , wood pellets and briquettes for the corresponding heating systems .
supporting documents
- ↑ a b c according to DIN 68364 - Characteristic values of wood species - gross density, modulus of elasticity and strength. May 2005.
- ↑ Peter Niemz: Investigations into the thermal conductivity of selected native and foreign wood species . In: Building Physics 29 . tape 29 , no. 4 . Ernst & Sohn Verlag for Architecture and Technical Sciences GmbH & Co.KG, Berlin 2007, p. 311-312 , doi : 10.1002 / bapi.200710040 .
- ↑ http://www.lwf.bayern.de/mam/cms04/forsttechnik-holz/daten/w45_das_holz_der_tanne_elösungen_verendung.pdf