What type of washer is used to cover a slotted hole in an outer ply?

The correct answer is the ASTM F436 washer, which is specifically designed to cover slotted holes in structural steel applications. ASTM F436 washers are flat washers made of steel that have been properly treated to resist corrosion and ensure a secure connection. Their design allows the washer to cover the entire area of the slotted hole, providing a larger bearing surface which helps to distribute the load and minimize the risk of damage to the connected parts. This is particularly important in structural applications where stability and integrity are critical.

In contrast, rubber washers typically serve a different purpose by providing a seal or cushioning effect rather than load-bearing characteristics, making them unsuitable for structural applications. Zinc-coated washers, while providing some protection against corrosion, do not specifically address the requirements for covering a slotted hole. Lastly, flat washers alone do not ensure the necessary properties or compliance with specific standards required for structural connections in this context. Therefore, the ASTM F436 washer is the most appropriate choice for effectively covering slotted holes in outer plies.