It looks to be very user friendly, and has some very interesting potential applications in the arena of adhesive application and repair for underwater environments.  No metering/measurement of the two parts is required, as they only require a kneading action to mix the two doughy components to uniform color.

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The video is sped up to quickly demonstrate the overall process required.  This  process requires a high level of attention to details, as they are very important.  Training and experience are necessary for good results.

Chemical adhesion between all of these layers will create a bond that is durable and suitable for restoring strength back to the structure.

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It is pretty cool to see the change in appearance as the coating is applied. I am amazed at how wet the part is sprayed.  Definitely not a traditional spray application method.  The coating is just dripping off of the part. My guess is that the spraying with an air nozzle is working to help remove any runs and wrinkles in the surface finish.

This coating process will act like a painted surface more than a part that has been subjected to a hardened plating process.  Surface adhesion will be very important to test the durability of the finished look.

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Material Fatigue in the corner

The loose panel flexed so much and for so long that it fatigued the material and failed in the corner of the inner fender next to the attachment to the rest of the hood.  To repair this, I removed the area with the rivets, ground down the surfaces of both pieces on both sides, and reattached them with fiberglass and epoxy resin.

Prepared glass and resin

I wanted to place epoxy and fiberglass on both sides of the repair area to ensure a good, solid bond that would hold very well.

Epoxy Resin and Fiberglass applied

After the area was prepared, I applied epoxy resin to the surface to ensure good adhesion.  I had a low spot that was a gap, so I mixed some microfiber and epoxy to make a paste and fill this gap.  A stronger bond is produced when the fiberglass is not spanning an open gap between the two pieces.  I placed two layers of 3oz Chopped Strand Mat over the paste and worked the air out to make a nice consistent repair.  I then ground down the surface to make a nice-looking, consistent repair.

The rear of the inner fender had similar problems.  A hole had emerged in the black SMC piece.  I ground down both surfaces and placed some fiberglass across the area to bond it together.

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The following is how I did it.

Composite Grinding Tools

Beginning with personal safety, I used a dust mask to prevent inhaling the dust into my lungs.  I used OSHA Z87 approved safety glasses to protect my eyes.  A pair of earplugs protected my ears.  Abrasion/dust resistant gloves for my hands, and a light jacket to keep the dust from my skin.

For removing the layers of SMC to feather edge the surfaces, I used several abrasive tools.  A five-inch pneumatic grinder with 80 grit sandpaper worked well on the large areas to quickly remove large amounts of material.  A right-angle die grinder with Roloc 3″ or 1.5″ sanding disks worked well for the concave areas and other difficult access areas.  A straight die grinder with a fluted burr worked to get into the detail areas of the front grill and other cracks that needed material removed.

All of the tools I used were air powered, so I had a good air supply that would keep up with me.  The large amount of dust that is produced from this sort of work presents explosion hazards when using electric tools.  Large dust piles can also spontaneously combust, so care must be taken during dust storage and disposal.

A air blow gun was also used in this process to clean the dust from the part and from my clothes.  It is important to keep personal safety equipment such as safety glasses and earplugs in place when using the blowgun.  A small vacuum can also be substituted with care taken to prevent dust ignition/explosion.

After all of the material is removed from the SMC hood, all of the dust is blown off to leave a part with a bonding surface that is clean, dust-free and ready to be repaired with epoxy and fiberglass.

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Time, effort, epoxy, and fiberglass, allowed me to successfully completed the repair.  This SMC hood will be repaired as good as new!

Damaged area to be repaired

The hood was placed upside to allow for work access.  The repair area had several cracks and breakage areas.  The repair began with surface preparation.

Surface Preparation on the repair area

I used a grinding disc to remove material on the front and back side of the repair to scarf the repair into the large area.  Good surface preparation gives us a clean area that can hold a bond and create a transition area.  I also drilled some holes in the end of the cracks to stop their propagation.

The back side was prepared too

The back side was prepared for repair by grinding the surface to allow for good bonding by the epoxy resin and glass reinforcement.

Beginning to add material

I started to add epoxy and fiberglass back onto the fender.  I had to gradually move back out to where the existing fender used to be.  I worked both sides bit by bit and allowed it to start curing before adding more.

Getting the shape back

I actually went a bit beyond the shape I needed.  This allowed me to get the surface planes in the right spot, and later return and trim back the proper hood edge.

Back side getting rebuilt

The back side of the repair also got transitioned into the hood and out to meet the front repair area.

Grinding the repair

After most of the rebuilding was complete, some grinding got it back into shape to allow an evaluation of the repair progress.

Grinding on the back

The back side was cleaned up as well, getting the appropriate part thickness back to where it was originally intended.  A nice transitioned surface was created, and all sharp edges were removed.

Bodyfiller for cosmetics

I used some bodyfiller to smooth the repair and restore the cosmetics of the hood.  I could also have used epoxy, and it would have bonded better.  Polyester bodyfiller is less expensive, easier to apply, and easier to sand.  I smoothed the surface and feathered it back into the surrounding area to allow for a consistant surface.

Application of Primer-Surfacer

Urethane Primer-Surfacer is applied to the whole area to allow for removing the sanding/grinding scratches and preparing the surface for paint application.

The repair is complete, and the hood looks back like it was original.  This repair, and many others, can be detected with some investigation of the back side of the repair area.  This will be a very durable repair and will last as long as the rest of the composite body panel.

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I have been using autobody filler since age 14, and am finally getting good at it!  Just kidding.  It is more art than science, and practice makes perfect.  Basically, a surface needs to be properly prepared to achieve good adhesion.  Then the filler is applied after being mixed with hardener, and allowed to cure afterwords.  Some fillers can be sanded as soon as 20 minutes after application.

Basic setup and tools

The basic setup is a working board surface to mix the bondo and hardener.  The mixed material is applied with a squeegee or putty knife to fill in low areas.  They also aid in cleanup, along with some paint thinner to clean the tools.

Hardener added

Mixing the hardener starts the application window from where the material goes from liquid to solid.  The hardener is a peroxide paste that directly affects cure time along with temperature.  Too little hardener can also cause poor physical strength characteristics along with difficult sanding properties.

Uniformly mixed

The hardener must be uniformly mixed before it is applied.  This prevents lots of problems down the road.

Applied to surface

The body filler can be applied with putty knives or squeegees to achieve the desired affect.  This polyester bodyfiller will shrink during cure, so filling high is typical.  The flip side is that all of the high spots must be sanded back down, which is wasting filler and time, so it is a fine line to walk.

Working with body filler can be frustrating for the beginner who must practice lots of patience.  There are many important aspects that must be followed, just like all composites materials processes.  Autobody filler requires proper surface preparation, mixing and metering of materials, and attention to details in order to avoid future problems.

A couple of other practices I recommend is to always wear a dust mask, keep the body filler dry, and only apply bondo over sanded bondo.  Some like to just build layers without sanding the lows, and this can lead to adhesion problems.

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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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The advantages of fiberglass composites mesh very well with their use in various applications in this industry. The strength-to-weight ratio is very important, along with the good adhesion of automotive paint. The low tooling cost of fiberglass relative to sheetmetal is a huge advantage, allowing for inexpensive low-volume production. The long service life and resistance to corrosion is another advantage over competing materials.

There are a few disadvantages for composites. Cracking can develop over time with improperly supported structures. Depending on processing, the smoothness of the surface (surface profile) can be subpar to that of sheetmetal, and is subject to worsen over the first year of its life. Paint adhesion can be a problem for all materials, and fiberglass composites have their own unique issues.

With proper processing, all of the disadvantages can be overcome. A properly designed and supported structure with good workmanship will never crack and will last forever. Surface profiling can be eliminated with a good print blocking material, good skin coat, and good resin. Paint adhesion can be optimized with the correct gelcoat and paint preparation methods and materials.

Fiberglass composites are well utilized in the RV and specialty vehicle market and will remain there forever. They are the best solution for the many challenges faced by the folks that build these great RVs.

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