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Fiberglass Part Making [by: Halloweenking]
Hotrodders Bulletin Board: Knowledge Base: Body-Exterior: Articles
When making fiberglass or any other composite material body piece or custom part, the most important ingredients are time and patience. Fiberglass and other composite materials (such as carbon fiber) require four things: cloth or weave, resin, separating agent, and a mold.
Fiberglass has long been used in the automotive industry, both in the production and customizing world. The first full American production car to utilize a fiberglass composite body was the Chevrolet Corvette, in 1954. Composite materials are used mostly because they are lighter weight and they don't sacrifice structural stability.
Within recent years, carbon fiber has become the latest "must have", mostly because of its distinctive look -- its extreme structural integrity and light weight are just an added bonus. Carbon fiber is much more attractive than fiberglass, but in most parts, such as body panels, both substances are used in a sandwiching process. Carbon fiber is also superior to fiberglass, as well as metal, in its strength to weight ratio.
Below is a step-by-step on how to accomplish the task of body panel construction. The process described below can be applied to any part or panel you wish to construct. For simplicity of explanation, a hood was chosen.
Making an OEM reproduction of an existing hood is as simple as 1-2-3. The easiest way to do this would be to remove your hood, strip off all paint, and smooth the hood to perfection with some minor bodywork and a coat of smoothly sanded primer. If you do not smooth the hood before making the mold, any imperfections in the mold will also be in your part. In the case of a carbon fiber hood, that simply isn't acceptable. After you have smoothed the panel, you will need to apply the separating agent to the surface you wish to replicate, in this case the top and rear frame of the hood. A good separating agent can be purchased at any composite material store. For smaller, less cosmetic parts, any type of wax can be used. After you have applied the separating agent, it's time to start making the mold.
You will need:
- Fiberglass weave or cloth pre-cut at least 3" larger on each side of the hood (should hang over each side), laid out for quick retrieval. Carbon fiber also, if you desire a carbon fiber part.
- A paint roller with a section of PVC pipe over the roller, snugly fit and coated with separating agent or wax.
- Plastic filler spreaders
- Natural bristle 3-5" paintbrushes with bristles held by adhesive, not crimped.
- 4 small plastic pails
- Rubber gloves
- Smock
- Old clothes
- Extra set of helping hands
- Gel coat
- Spray gun
With a mold, the basic idea is to replicate as best as possible and as smooth as possible.
- First, spray a uniform coat of gel coat on the hood, this will aid in both the mold making and resulting smoothness.
- Now, with your helper, lay one layer of fiberglass cloth on the surface, starting with the center of the cloth and out. Make sure there is a bit hanging over the sides, at least 2".
- Now, quickly mix your resin. The resin will start to harden as soon as the catalyst is added so quickly mix it and with a brush soak the fabric.
- Then, quickly apply another layer and soak with resin. Do this 3-4 more times.
- After you have applied the last layer, with the roller and pipe (with slight pressure), roll the fabric and resin smooth. This will not only smooth the fabric, but also squeeze any air that's trapped inside, making a stronger mold. The filler spreaders work just as well, but I've found a roller is much faster.
Do the same molding process to the rear hood frame. In the overlapping cloth or weave, on each side you can put a golf ball, or any object. This, when in both sides of the mold, can be an easy way to align the pieces. After the mold has cured for at least 2 hours you will simply need to lift it off.
Now that you have a female mold from the male part you wish to replicate, it's time to make the part.
- The first step is to apply the separating agent.
- After you have done that, you need to spray in the gel coat, just like before. For carbon fiber parts, a clear gel coat must be used.
- Just like before, lay one layer of cloth or weave in the mold. In carbon fiber parts, the first layer is always, of course, carbon fiber.
- Mix and saturate your cloth just as before. Lay on your second layer, in carbon fiber pieces it would be a layer of fiberglass cloth. Carbon fiber parts alternate from carbon weave to fiberglass weave, and will end in a carbon fiber weave.
- Just as before, on your last layer smooth with slight pressure with either the spreaders or roller and pipe.
- Now, before the two pieces fully cure (hood surface and hood frame) you will need to apply some resin to the hood frame and mate the two pieces together. Be very careful -- once it's on, its not coming off, so make sure it's aligned correctly.
- After the hood has cured, remove it from the mold. If it's a pure fiberglass hood you can prep it for paint. If it's a carbon fiber hood you can apply a few coats of urethane or polyurethane clear to enhance its looks or simply clean and install it on your vehicle.
This process can be used in any part making from OEM replication to custom parts. Custom parts will require a male piece to make a female mold. A male piece can be made from anything, foam, wood, plaster of paris, plastic filler or even candle wax or any combination therein. Foam can be used, but due to the chemical makeup of the resin, it must be covered in a few layers of either plastic filler or regular latex house primer, sanded smoothly, and of course before any application of resin you must apply a separating agent.
Always use good quality resins and cloth or weave from a reputable dealer. The quality of the supplies will result in the quality of your product.