Plywood is used in many different applications, including wall sheathing, flooring, furniture, and cabinetry. But a lesser known application for plywood is for use in aircraft. The earliest airplanes used wooden parts as it was more accessible than current materials like aircraft-grade aluminum or steel. Today, there are still plenty of different aircraft which use solid wood and plywood to construct the many different components inside and out. But what makes aircraft grade plywood different from standard grade?
Standard Versus Aircraft Grades
Standard plywood comes in many grades, types, and materials. Your typical hardware store plywood comes in up to a 4 foot by 8 foot sheet, and around a ¼” thick. Usually, you will see different grades of plywood as well, either prime, B, C, or sometimes D grade. These designations categorize each selection of wood based on their inherent qualities. The better the grade, the less imperfections and a better overall performance. Cost will vary with each grade, with prime being the most expensive.
What makes aircraft plywood different
Aircraft grade plywood is similar to standard plywood, however the materials of construction are vastly superior and performance is placed over appearance. While naturally appealing in appearance, aircraft plywood only has it’s great appearance because of the required species of wood for its performance. They also come in boards as thin as 0.40 mm thick. Most people will not opt for aircraft plywood for any general woodworking or construction project since it costs about four times as much as a standard sheet of plywood, but if your project budget allows, you will not go wrong with using aircraft grade.
Summary
Aircraft grade plywood is similar to standard plywood, however the materials of construction are vastly superior and performance is placed over appearance.
Aircraft Plywood Manufacturing
Aircraft plywood is manufactured to adhere to certain specifications defined with the intention of use in aircraft. Typically, the specification defined for this grade of plywood is MIL-P-6070. With this specification, the qualities of aircraft plywood differ from regular plywood to improve performance in situations that aircraft would experience. The boards should be strong and the adhesives should withstand moisture and heat. The specification also requires testing of the boards by applying a shear force after being submerged in boiling water for three hours to verify the quality of the bonding layers.
Many conditions seen by aircraft are what drives the defining properties of aircraft plywood. For example, when flying, aircraft will experience turbulent winds, which can cause vibrations and dynamic forces on the external parts. The aircraft experience other extreme conditions such as shifting temperatures and moisture. These unusual conditions necessitate the improved formulation for plywood where plywood could be an excellent choice in material, given that it is made with superb components and of the highest quality.
The manufacture of aircraft plywood is similar to regular plywood, however the quality and grade of the wood and resins are more premium. Typically, birch or African mahogany is used in the creation of aircraft plywood. This is due to these species’ tensile strength, hardness, and generally smooth grain structure. In fact, Douglas fir wood, a common standard plywood species, has an ultimate tensile strength of 2.3 GPa, whereas birch wood has an ultimate tensile strength of 2.60 GPa, or 15% more strength than standard plywood. In addition, birch and mahogany seldom have pockets or voids, making them the ultimate choice for a clean, strong product.
Basswood is also an accepted species for manufacture, however it is less common and is slightly less rigid than birch or mahogany. Basswood is also much lighter too, coming in at nearly half the density of birch or mahogany. For specific applications, Basswood’s properties could be a great choice, providing formidable strength while being as light as pine wood.
Summary
The manufacture of aircraft plywood is similar to regular plywood, however the quality and grade of the wood and resins are more premium.
Applications for Aircraft Plywood
Aircraft plywood has been used since World War II. Many airplanes used during this period were constructed using aircraft plywood, notably the British-made DS.98 Mosquito, a plane nicknamed the “Wooden Wonder”. This plane served many years as both a fighter plane and a bomber craft. The choices in materials stemmed from the climate and the service conditions. Beyond the 1940s, aircraft plywood has seen continued use across a wide array of aircraft for many components, including floor boards, wing skins, and gusset plates.
Aircraft plywood is also great for applications outside of aircraft. The inherent properties of aircraft plywood make it an excellent choice for kitchen cabinetry due to its high strength and strength retention when exposed to heat and moisture. If you live in a humid climate, this grade of plywood would serve well as a structural board for walls and floors since it resists moisture in hot, humid air. While not the most economical choice, aircraft plywood would serve any need with absolute certainty.
Summary
The inherent properties of aircraft plywood make it an excellent choice for kitchen cabinetry due to its high strength and strength retention when exposed to heat and moisture.
