Say an airplane wing was damaged by hail, it's really costly to replace the panel due to inaccessible rivets and what not, and the back of the panel is inaccessible to mechanically remove the dent. How are light weight fillers made to fill the gap? Not like the heavy stuff like Bondo that is (was?) used to fill dents on cars, piled on and then sanded smooth. Airplanes need something light weight.

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    $\begingroup$ I don't know of any fillers used on aircraft skins. The problem is that the skin isn't rigid enough to hold a filler like bondo is for cars. When aircraft are hail-damaged they either fly with "speed dimples", or they are reskinned. $\endgroup$
    – Ron Beyer
    Oct 25, 2018 at 1:32
  • $\begingroup$ If you want a long read on FAA authorized repair procedures give that a go. $\endgroup$
    – Ron Beyer
    Oct 25, 2018 at 1:48
  • $\begingroup$ I’m not an A&P but I’ve worked a lot on small airplanes and I would be shocked if any filler was approved for wing repair. It would be appropriate for non-structural repairs like on fiberglass fairings and wing tips but not on the wings, tail, or fuselage. $\endgroup$
    – JScarry
    Nov 25, 2018 at 2:10
  • $\begingroup$ Poly-Fiber's SuperFil has long been used on aircraft. It adheres very well to aluminum, wood, and composites. Many people specifically use it to fill seams and low points specifically because it adheres well, is easily applied, has a 60 minute pot life and cures to sandable condition in 12 hours. $\endgroup$ Nov 25, 2018 at 11:57

1 Answer 1


Lightweight body fillers such as Poly-Fiber's SuperFil are two-part epoxy fillers. The reason they are lightweight is that a significant portion of the filler in the epoxy is composed of microballoons, also known as glass microspheres.

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    $\begingroup$ This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. - From Review $\endgroup$
    – Vikki
    Nov 25, 2018 at 4:01
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    $\begingroup$ @Sean The core of the question is "How are light weight fillers made to fill the gap?" My answer does exactly that, answer how the lightweight filler is made. $\endgroup$ Nov 25, 2018 at 11:49

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