How to Use Bondo for Fiberglass

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Things You'll Need

  • Fiberglass Bondo kit

  • Clean piece of plastic or glass

As fiberglass components age, stress cracks and panel distortion can result. Replacement fiberglass panels are readily available but can be very expensive to purchase. The expense of replacing damaged fiberglass panels can be significantly reduced by instead repairing the panels with Bondo. Fiberglass Bondo is waterproof, extremely strong and can be used for virtually any fiberglass panel. As an initial matter, it must be recognized that there is Bondo for metal and Bondo for fiberglass. Ensure that the Bondo for fiberglass is used. Follow the steps below to use Bondo for fiberglass.


Step 1

Locate the filler and the hardener from the Bondo kit. The filler is the material in the can, while the hardener is the material in the small tube.

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Step 2

Select a clean piece of plastic or glass or some other smooth material to mix the Bondo.


Step 3

Mix the filler to ensure that the chemicals of the filler are evenly distributed.

Step 4

Mix the hardener by thoroughly kneading the tube.

Step 5

Pour or scoop filler material onto the mixing surface chosen in Step 1.


Step 6

Squeeze a single line of hardener from the tube across the filler located on the mixing surface.

Step 7

Mix the filler and hardener together until the mixture reaches a uniform color.

Step 8

Use the plastic spreader included with the Bondo kit to spread the mixed filler over the area to be repaired by using a firm wiping motion. The mixed filler should not be applied more than ¼ inch thick. Only wipe the filler on the surface in one direction, or bubbles will form into holes when the filler dries.


Step 9

Allow 5 to 10 minutes for the filler to cure.

Step 10

Once the filler has dried, it can then be sanded to the desired shape and painted if so desired.


The chemicals included with the Bondo kit should not be ingested. If ingested, immediately consult a physician. Avoid prolonged inhalation of Bondo vapor. Avoid prolonged or repeated contact with skin. The chemicals included in the Bondo kit are combustible. Keep chemicals away from heat, spark or flame.


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