Definition
Smooth, rigid plates placed against the surfaces of a composite or bonded layup during curing to distribute pressure evenly and produce a smooth, uniform finish on the part.
Plain English
Flat, hard plates pressed against a part while the glue or resin sets, so the surface comes out smooth and the pressure is spread out evenly.
Context Anchor
Seen in aircraft maintenance and structural repair, especially when bonding wood, metal, or composite parts.
Derivation
Caul' is an old English woodworking term for a board pressed against a surface during gluing to keep it flat. The aviation usage carries the same idea into composite and bonded repairs.
Why Pilots Care
Proper use ensures structural repairs meet airworthiness standards by preventing voids or uneven bonds that could lead to delamination in flight.
Analogy
Like pressing a heavy, flat board on top of a freshly glued tabletop while the glue dries, so the surface stays flat and even.
Intuition Check
Do not confuse “caul” with “caulk.” Caul plates do not seal gaps; they press and support a part while the bonding material hardens.
Example Sentence 1
The technician positioned caul plates over the composite repair before placing it in the autoclave.
Example Sentence 2
After the cure cycle, the caul plates were removed to reveal a smooth, ready-to-paint surface on the wing repair.