What are the two types of dope used for fabric finishes?

The correct choice is based on the specific types of dope historically and currently used in fabric finishes for aircraft. Cellulose nitrate and cellulose acetate butyrate have been traditional dope materials utilized in the finishing of fabric surfaces on aircraft.

Cellulose nitrate is known for its fast-drying characteristics and is effective in adhering to fabric. Meanwhile, cellulose acetate butyrate provides a more durable finish that offers better resistance to environmental degradation, such as UV light and chemical exposure. These two types of dope contribute to the overall performance and lifespan of the fabric covering.

Other options listed do not represent the traditional or common finish types used for aircraft fabric. While acrylic and polyurethane are modern alternatives frequently used for finishes due to their durability and aesthetic properties, they do not fall under the category of dope traditionally associated with fabric applications in aviation. Polyester and vinyl, as well as silicone and epoxy, also refer to materials used in different applications but do not specifically pertain to the dope finishes that are essential for aircraft fabric coverings.