SuperFill Rivet Holes

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Overview

Superfil is a lightweight polyester-based filler used to fill countersunk rivet holes and minor surface imperfections before paint. Multiple RV-15 builders prefer it over the traditional alternatives (epoxy micro-balloon slurry or straight epoxy) for its ease of application and sanding.

This technique is NOT described in the Van's KAI. It is a finishing preference only — the choice of filler is up to the builder, but countersunk rivet holes should be filled before topcoat for corrosion protection.

Here is additional instructions from Tony, a multiple Lindy champion.

Why Superfil?

  • Why fill, beyond cosmetics: The steel mandrel stem left inside a blind rivet can rust over the life of the airplane, depending on climate and storage. Filling the holes largely removes that risk. One DAR characterizes filling as normal paint preparation — comparable to filling pinholes in composite — rather than a deviation from the build. Source
  • Easier to apply than mixing epoxy micro-balloon slurry — comes ready to use from the tube.
  • Easier to sand — cures softer than straight epoxy, feathers cleanly with 150–220 grit.
  • No mixing ratio errors — reduces waste and prep time.
  • Commonly available at automotive paint supply stores and online.

Application Notes

  • Small syringe to place, press in with fingers, wipe excess, light scotchbrite after cure.
  • Easier injection: Injecting through an 18-gauge needle is slow and hard on the hands — one builder developed hand pain doing a single wing, and thinning with alcohol didn't help. Instead, press the needle out of its adaptor (bench vise) and dispense through the adaptor's own bore, which is close to rivet-hole diameter, using unthinned SuperFil. Source

Alternatives

  • Epoxy micro-balloon slurry — stronger, but harder to sand and requires careful mixing.
  • Straight epoxy — not recommended for rivet holes; very hard to sand flush.
  • Rage Gold / Rage Extreme — similar automotive body filler products some builders use.

Sources

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