Following the repairs to the inside and outside of the Arctic Cat Snowmobile hood, it is time to provide the finishing touches to complete the project.
There were a couple of edges where the new fiberglass repair had been hanging over. These need to be ground back to recreate the clean edge.
The next step is to sand off the inside of the repair areas. The epoxy leaves a shiny surface. Sanding it down will allow it to create a better bond with the following process.
Now the inside of the repair can be painted. This paint is optional, but it does wonders to hide the repair. The prior failed repair was not painted over, and it was very obvious that there had been a repair. The paint in question was flat black spray paint from a rattle can. A layer of primer prior to the paint would have been a better solution, but this is only the bottom side of the hood.
The bottom side is completed, and now the top side can be finished. The surface has been filled, sanded, and smoothed. Now it can be painted.
The original hood was all gelcoated, and a proper repair would have been black gelcoat. However, the hood is 45 years old, and there were several other cracks and blems surrounding the repair area. A proper job would have included more work than the snowmobile was worth.
The last step was a coat of black paint. The primer and paint were both from rattle cans. The paint came out smooth, and blended into the surrounding gelcoat. It is much better than before, and the repair area looks good. The problem was that there are several other areas of the hood where the gelcoat was cracked and could use some repair. Again, more work than the entire snowmobile is worth. My luck is that this snowmobile hood will get damaged again anyway. These repairs should only fail from impact, not bad workmanship or materials.
Following the repair of the inside of the fiberglass hood from the Arctic Cat snowmobile, it is time to tackle the outside portion of the repair.
The outside of the hood had gelcoat that had been damaged, and is in need of a cosmetic repair. The hood had been prepped with a grinder to remove loose pieces and provide an abraded surface that will have good bond strength.
The first step is to remove the tape that had been limiting resin intrusion. The resin was well on the way to curing prior to the tape being removed.
Next was to begin the actual repair. The area was taped off to limit the resin and filler getting onto the neighboring gelcoat. The tape was used more as a dam than as a flat edge.
The repair material was a filled epoxy resin. The first step is to apply the pure mixed epoxy to the the substrate. This is done prior to the application of the filler. It helps with the bonding process to have some pure epoxy between the filler and the fiberglass.
Then a batch of epoxy filler was mixed into a thick paste to be applied to the repair areas. Part of the challenge is to fill the voids to be level with the existing gelcoat. If they are too high, they will need to be sanded off. Too low and a bunch more filler will be required.
The filler paste takes a while to cure. Once it does, the tape can be removed.
Then the sanding can begin. Beginning with a coarse grit helps the work go faster, but there is greater risk of creating damage to the surrounding gelcoat. The first pass here was at 80 grit.
These areas were sanded by hand. Power tools are available, but the overlap onto the gelcoat would have been greater. Depending on your project, that may not be as important to you. Going after an area with power tools runs the risk of flattening out the entire area and removing a bunch of gelcoat. The whole profile of the are could end up being sunken down from the original profile.
There were still a few very minor low spots that required filler. This was more of a “skin coat” so there was not the need for all of the tape.
All of the areas were skimmed with a thin layer of filler. Following cure, they were sanded again, but this time only a few high spots were sanded with 80 grit. The next stage was some 180 grit, finishing with some 320 grit sandpaper.
The final sanding was to ensure a smooth transition from the repair areas to the gelcoat areas. Making sure that there were not any dips or lines in the repair transitions will help to ensure that the repair will not be spotted. Sometimes the hard edges can be seen with a visible eye, but an experienced touch is the best way to check out a transition. Running your entire hand (not just your fingers) over the repair will help you gauge the smoothness and straightness of the repair.
The last thing to do is to paint it.
The damaged snowmobile hood is prepped and ready for a proper repair with new fiberglass and epoxy resin.
The hood had already been ground to promote adhesion. Then it was cleaned to remove contaminants.
The inside of the hood will be repaired first. The repair will be completed using fiberglass reinforcement and epoxy resin.
To keep the resin from leaking through to the other side, I used masking tape to cover the crack and other holes, applying it to the backside of the work areas.
The damaged hood was out of shape, and it needed to be pulled back to being straight. The corners of the hood were cracked and the center section of the hood was moving around. Not wanting the repair to permanently alter the shape of the hood, a pipe clamp was used to pull it back into the proper shape.
The first part of the process was to mix resin and cut fiberglass. Mixed epoxy resin was applied to the repair area to wet it out. Then a couple layers of the fiberglass random strand mat was wetted out and applied. Following of the glass strand mat, the 1708 was cut out to cover the general area. The 1708 was wet out and and applied. Then another layer of glass strand mat was applied to the general area that was ground out.
An inexpensive bristle brush was used to remove the air bubbles and smooth out the layers. This consolidates the fiberglass into a smooth layer that will add mass and strength to the hood.
The random strand fiberglass adds strength and adhesion to the 1708 fiberglass mat that is used to repair the cracks in the hood.
The mass is kept at a temperature of 60-80 degrees and allowed to cure overnight. The following day the extra fiberglass edge is trimmed with a razorblade knife to remove the sharp fiberglass edge.
The repair is allowed to cure for 24 hours before removing the pipe clamp.
The repair is structurally complete, but there is one more step to complete a professional repair.
Prior to adding resin and reinforcement to the Arctic Cat Snowmobile Hood, we need to grind the areas in need of repair. Grinding will remove the damaged resin and glass. This allows us to bond new resin and fiberglass to the existing good material. For repairs to be successful, proper bonding is extremely important. Removing contaminants and loose/damaged glass, resin, and gelcoat is one of the most critical steps in assuring a successful repair.
The repair will include both the inside and outside of the hood. The inside is a structural repair and the outside is mostly a cosmetic repair.
On the inside, I used a flat-disk right angle air grinder to remove the necessary material so that the repair could bond onto clean, original fiberglass.
Proper safety precautions must be observed. Gloves, glasses, and ear protection are all necessary. Skin protection is advised, as the dust can cause itching and irritation. It is also very important to not breathe the dust.
This is a messy job. Lots of fiberglass dust is generated during the process of removing material to get down to a good bonding surface.
These two corners of the snowmobile hood were cracked, repaired, and cracked again. The grinding had to remove most of the failed repair and get down the bondable fiberglass. It is important to remove shiny areas to allow for a good bond to form between the existing materials and the new repair materials.
The outside of the hood had cosmetic damage. While doing the dirty and messy grinding job on the inside of the hood, it is just as easy to keep going and doing the outside of the hood too.
I switched to an air-powered rotary file (grinder) to remove the cracked gelcoat and contamination.
It is important to grind out any cracks and loose material. Contaminants need to be removed as well. The abrasion will greatly improve the bonding of the new resin with the old subsurface.
Once the grinding is complete, it is important to remove all of the accumulated dust while keeping the surface free of contamination. Compressed air works well, but it must not contain water vapor or oil.
Now we are ready to move on to the fiberglass and resin.
Snowmobile engine hoods are susceptible to damage. The hood is at the front of the machine, which increases the likelihood for impact. The hood covers the engine and is hinged to allow access. This exposes the hood to engine heat and vibration. There hood also experiences forces where it is attached to the hinge connection.
This 1972 Arctic Cat Cheetah 440 snowmobile had seen damage across the front of the engine hood. Cracked at the corners, the hood had been repaired with fiberglass and polyester resin in the distant past. This old repair included 2-3 layers of plain weave cloth tape without any random strand fiberglass mat included in the layup.
The original repair was a structural repair on the two corners of the hood leading away from the hinge attachment holes. There had not been an attempt at any cosmetic repair to the front side.
A damage survey like this only leads to one thing- a repair project!
This can be repaired with a few basic tools and supplies. More to follow.
3D Printing is a new technology that will change how parts are designed and manufactured. This technology has advanced to allow the usage of carbon fiber reinforcement to create parts.
From Youtube Thomas Sanladerer
If you are starting out in the world of making parts from carbon fiber, you will need tools and materials to complete the process and have a successful outcome with your composite parts.
The following is an introductory video for the materials that you will need to complete the vacuum bagging process with carbon fiber and eopxy materials.
From Youtube The Fab Forums
I hope this helps some you guys out that are looking to try your hand at making some Carbon Fiber.