How Do I Repair Cracked Fiberglass Panels On My Cover?

Having a protective cover on your truck bed provides many benefits, from keeping your cargo clean and dry to improving gas mileage. However, over time, wear and tear can lead to cracked fiberglass panels that need repairing. Don’t worry – with the right materials and some DIY know-how, you can fix those cracked fiberglass panels and get your cover looking great again.

What Causes Fiberglass Covers to Crack?

Fiberglass tonneau covers are durable but still prone to damage from:

• Heavy weight or sharp objects in the truck bed putting excessive stress on the cover. Too much weight can bend the panels or cause stress cracks.
• Normal road vibration and driving can loosen panels and hardware over time, leading to cracks or separation.
• Exposure to extreme weather like hail storms or winter ice/snow can crack the fiberglass.
• Accidental impact from cargo shifting or loading/unloading the bed. Fiberglass is rigid but still somewhat brittle.
• Improper opening or closing of the cover, bending the panels past their limit.
• Manufacturing defects or low quality materials that develop cracks prematurely.

Regular inspection and proper care can help prevent many cracks, but damage still occurs after years of use.

Gather the Necessary Materials and Tools

Repairing cracked fiberglass panels requires just a few supplies:

• Fiberglass repair kit – Contains fiberglass cloth/matting, resin, catalyst/hardener, mixing containers, etc. Kits made specifically for auto/truck repairs are best.
• Paint brushes – Disposable bristle brushes for applying resin. Foam brushes also work.
• Sandpaper – An assortment of grits like 80 grit, 220 grit and 400 grit for sanding and feathering.
• Masking tape – For masking off repair area from unaffected areas.
• Scissors – For cutting fiberglass mat to size.
• Gloves and safety glasses – For protection from irritating fiberglass and resins.

Make sure to use materials designed for fiberglass repair like polyester or vinyl ester resin. Epoxy resin is very rigid and may crack again. Read all safety instructions for the products you use.

Thoroughly Clean and Prepare the Damaged Area

Proper surface preparation is crucial for good adhesion when making fiberglass repairs. Follow these steps:

• Clean cracked area with a mild detergent and water to remove any dirt, grease or debris. Make sure the area is completely dry.
• Use 80-120 grit sandpaper to sand and roughen 1-2 inches around crack. This gives the repair resin something to grip.
• Feather and taper sanding outwards from the crack to smooth the transition.
• Wipe area clean again. Mask off repair area with tape for a neat repair.

This surface roughening provides the important “mechanical bond” for the new resin to adhere properly. Any compromised adhesion will lead to a weak spot and potential re-cracking.

Mix the Fiberglass Resin According to Instructions

The resin and hardener (catalyst) must be mixed in the proper ratio specified on the repair kit instructions. This is usually around 2-3% hardener by volume. Insufficient hardener will prevent proper curing, while too much can over-cure and become brittle.

• Measure out resin and hardener in mixing container. Pot life is limited once combined.
• Stir thoroughly for 2-3 minutes – resin should be uniform color with no streaks.
• Avoid creating bubbles, as they will be visible in the finished repair.

Mix only as much resin as you can use during the 30-60 minute pot life. You may mix small batches for multiple thin layers. Follow safety gear recommendations.

Apply Resin and Fiberglass Layers to Build Up Thickness

With the surface prepped and resin mixed, you’re ready to start applying layers:

• Use disposable brush to apply thin layer of neat resin over crack and surrounding sanded area. This wets out the surface for bonding.
• Cut fiberglass mat slightly larger than repair area. Place over resin tack coat. Use brush to smooth out any air bubbles.
• Apply another thin resin layer over the fiberglass, saturating through to bond with previous layer. Remove air pockets.
• Build up 3-5 total layers this way, alternating fiberglass mat and resin. Fully saturate each layer.
• Final layer can be only resin, feathered out onto surrounding area. This provides a strong, smooth finish.

Take care not to simply pile on excessive resin, as it can run off or over-cure. Fiberglass cloth provides the strength, while resin binds it together.

Shape and Sand the Repair for a Smooth Finish

Once the built-up repair has cured fully, the last steps are shaping and feathering:

• If needed, use razor blade to trim any excess fiberglass hanging over repair area.
• Use 80-120 grit sandpaper to shape and contour repair to match surrounding fiberglass.
• Smooth the edges by gradually feathering and blending repair into surrounding area with 220-400 grit sandpaper.
• Wipe off sanding dust and debris. Fiberglass repairs are now ready for finish painting.

Proper cutting and sanding leaves a repaired panel strong and durable, with no visible transition between old and new sections. Avoid over-sanding into good layers.

Apply Primer, Paint, and Clearcoat for Factory-Match Finish

Fiberglass repair complete, apply matching auto paint for a factory finish:

• Clean and dry repair area thoroughly after sanding, then apply primer. This provides base for paint to adhere.
• Once primer has cured, apply color-matched paint in 2-3 even coats until fully covered. Avoid runs or sags.
• Finish with 1-2 coats of clearcoat for glossy protection and to blend paint transition.
• Allow full cure time before handling panel. Reinstall on truck once paint has hardened completely.

Quality automotive paint supplies are recommended for color accuracy and durability in outdoor use. Now the repaired panel can withstand years more service!

Tips for Successful Fiberglass Panel Repairs

Keep these techniques in mind for easy, lasting fiberglass repairs:

• Limit flexing – Fiberglass cracks can worsen if panel is opened/closed during repair. Try to remove panel or keep shut until cured.
• Repair both sides – For long cracks, repair inside of panel too using same layering method for full strength.
• Round edges – Round the cut fiberglass cloth edges so they don’t poke through resin layers.
• Reinforce stress points – Add extra matting layers around attachment holes or other natural stress points.
• Apply UV barrier – Use UV-blocking primer/clearcoat so sun exposure doesn’t damage repair.
• Take your time – Work slowly and methodically for best results. Rushing leads to mistakes.

With a step-by-step approach and these tips, you can successfully repair cracked fiberglass panels on your truck cover. Just gather the right supplies and put in some elbow grease. In no time you’ll have those cracks filled for a seamless, durable repair.

Frequently Asked Questions About Repairing Fiberglass Covers

What’s the easiest temporary fix for a cracked fiberglass panel?

For a quick temporary repair, use fiberglass repair tape. It comes in various widths with adhesive backing. Simply stick it over the crack to seal it. This won’t be as permanent or invisible as a full repair but can buy you some time.

What’s the best way to prevent cracks in the first place?

To prevent cracks, open/close the cover carefully avoiding twisting or flexing panels excessively. Inspect hinges and hardware regularly and lubricate with penetrating oil or silicone spray if anything binds. Avoid excessive weight and impacts in the bed.

Can I just use regular body filler or Bondo instead of fiberglass cloth?

Body filler alone is rigid and will likely re-crack. Fiberglass mat flexes better and reinforces along the length of a crack. Use body filler only for small localized dents/dings, not cracks. The fiberglass system bonds together for the right durability.

Do I need to remove the whole panel or can I just repair in place?

For small cracks, you can often simply tape off the area and repair in place without removing panels. This saves time. For long cracks or ones near edges/hardware, full panel removal lets you reinforce all areas thoroughly. Assess on a case-by-case basis.

Is there a quick way to blend paint on a repair without repainting the whole panel?

Use very fine 600-800 grit or even wet sanding 1500 grit paper when feathering out the clearcoat around a repair. This smoothes the paint transition. You can also use rubbing/polishing compound to blend the paint further after it has cured. Mask off surrounding areas carefully.

What should I look for when choosing a fiberglass repair kit?

Look for a kit specifically designed for auto/truck use, not only boats. The resin should be polyester or vinyl ester formulation to avoid becoming too brittle. Make sure it includes quality matting/cloth and is not just resin. A kit with varied grit sandpaper and mixing tools can also be handy.

How soon can I drive the truck after completing the repair?

Most resins take 24-48 hours for an initial cure, but wait at least 72 hours before driving to allow full strength to build. If you must drive sooner, go gently over smooth roads. Let paint fully cure for 5-7 days before hauling cargo or going off-road.

What’s the most common mistake people make when repairing fiberglass

The most common mistake is inadequate surface preparation leading to poor adhesion. Even with layers of repair resin and fiberglass, the repair will eventually fail if not bonded well to the original surface. Thorough scuffing and cleaning are critical first steps.