Composites with a nice, decorative gelcoat finish such as boats and RV’s require special care to make holes in them for placing bolts and rivets.  Disturbing the area around your hole in a gelcoated surface can lead to very expensive repairs by a fiberglass expert.

You can make holes yourself, but it requires extra care and attention.  I found a great Youtube video that demonstrates this from user CenturionCrew.

Of course the biggest mistake that can be made is improper placement of the hole.

Following the instructions in the video and drilling a nice slow speed hole is the best way to be successful.  He also mentions the caution that must be noted to stop the drill chuck from contacting the gelcoated surface.  One tip that I have is to place a small piece of rubber hose over the drill bit to contact the gelcoat before the drill chuck.

One other note with holes (all shapes and sizes) in cored composites fiberglass pieces.  If there is a layer of balsa or foam core in the cross section, extra precautions should be exercised.  One is to coat the inside surface of the hole with gelcoat, resin, or silicone to keep moisture and UV out of the core.

Another concern is compression of the core with mechanical fasteners.  Balsa and foam cores typically are low in density, and are not meant to be highly compressed.  If you are going to bolt something on, and it is going to be really tight, it is best to use a metal sleeve in the hole that is the same thickness of the fiberglass part.  Large washers or backer plates should also be used to distribute the load across a larger surface.

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Fender corner damaged by cracks

I began the work by preparing the area by grinding away the outside layer of existing material.  This helps us get a good mechanical bond and a clean surface.  It also allows for a feather edge transition between the repair area and the existing composite.

Fender getting epoxy and glass

The ground-out area is within the black outline created by a primer layer, and the underlying SMC is white in color.  This area was ground with 40 grit sandpaper and followed by a healthy dose of compressed air to remove the dust from the process.  I then wet-coated the areas with epoxy resin before turning to the glass and wetting that out.  The soaked glass was applied to the back side of the fender to add strength back to the cracked laminate.  A thickened epoxy paste was added to the front to fill the cracks that were ground out, as well as filling the holes drilled in the end of them.

Driver's fender from the backside

The glass applied to the area was applied down with a strong bristle brush to get maximum surface contact and remove air bubbles between the layers.  The strength of the glass and epoxy will restore this area of the hood back to its original specification as long as a good bond is made to the composite laminate.

Trimmed after cure

As the resin and glass cure, there is a time window when the resin is in the solid phase, but not rock hard.  This is when it is appropriate to take a utility knife and trim the edge of the loose glass.  If it is tried too soon, it will move the glass on the laminate repair, and if it is too late, the knife will not cut through.  If this time frame is passed, it still can be cut with a saw blade or grinder, but is much messier.  This is also a good time to wipe up any resin that is draining from the repair.

The repair area can now be sanded and body finished before paint and primer!  This resin will need to be covered to prevent UV damage in the future.

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Advantages of composite poles over wood are numerous.  Composite poles have a lifespan of roughly 80 years versus the 25-30 years for wood, due to rotting issues.  These rotting issues with wooden poles are combatted with chemical additives that are sometimes corrosive and toxic.  Composite poles have a weight advantage, as they weigh about two-thirds less than a wooden pole, which allows for easier transportation to the jobsite and reduced equipment requirements for installation.  Due to their controlled and known construction, composite poles have physical properties that are more stable and reliable over the duration.  Composites are intrinsically non-conductive, which is ideal in this application.

Replacing an existing material in a current application always brings hurdles and challenges for acceptance.  The wooden poles are known by purchasing, engineering, installation, and line utworker crews.  Composite poles have a higher upfront cost, though long-term savings are significant.  As the educational resources reach those affected, the transition will take place and composite utility poles will become widespread.

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The manufacture of fiberglass parts typically requires a gelcoat layer to aid in the release of the parts from the mold. The parts that will be painted also are manufactured with gelcoat but it is a “sandable” variety. These parts are often automotive-related, and may include pickuptruck toppers, fiberglass kitcar bodies, and other aftermarket add-ons such as running boards or hood scoops.

The unsaturated polyester/vinylester gelcoat is directly compatible with resins and laminate of the same chemistry. Gelcoat can be used with epoxy resins but requires a tiecoat for adhesion because of the chemistry difference.

Gelcoat is applied at 18 to 25 mils (thousandths) and will lose thickness as it cures. Typically when it is dry on the part, it can be down to 12 to 18 mils. This is a lot thicker than a painted surface. One of the disadvantages of gelcoat is that it can be more difficult to repair, especially with color matching. The thickness typically allows for sanding out scratches and blemishes, but going through can be painful and will require a respray. The outer layers of gelcoat will likely discolor over time due to UV degradation, and sanding and buffing into the underlying gelcoat may cause discoloration as the layers are different colors depending upon the depth.

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Some resins cure with time and elevated temperatures, which are achieved with the use of ovens. These allow for nearly unlimited open working time before cure. When things are satisfactorily placed, the temperatures are elevated to start the cure process.

UV Light is another curing mechanism that has special applications and takes the temperature consideration away. This has a big use with the infrastructure restoration industries working onsite and underground. It is much more of a specialized niche application.

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