Belly Pan Basics
- Laura
The VRRA wants your bike to have a belly pan. This sounds like a good idea, so the thinking and planning begins.
What are belly pans for? Also known as oil containment pans, they sit under the engine of the race bike to collect any dripping fluids from the bike, as you circulate the track, thus preventing other riders from slipping in your dribbles.
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What are they made of? Aluminum, steel or fiberglass seems to be the popular choices, depending on the knowledge, tools available and comfort level of the fabricator. If all three of those categories are at zero, the options are wide open. Metal belly pans require a brake for bending, some serious metal cutting tools, and a degree of familiarity with welding. Fiberglass requires the ability to think in 3D while fabricating moulds from discarded cardboard boxes, pattern making skills to cut the cloth, a love of rubber gloves, and a cool head to work under pressure before the resin begins to set.
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How do they attach to the bike? There is definitely no "one-size-fits-all" solution. Bolts, quarter-turn fasteners, and clips will help with easy-on and off. Duct tape is not recommended.
Where to start? To save time, frustration and materials, a thin cardboard pattern is a good place to start. This helps acquaint you with the dark underbelly of the machine, and the potential difficulties that may be encountered, like the exhaust pipes, engine guards, and basic lack of symmetry. Check both sides, many times. Measure, measure and measure again. Write those numbers down and refer to them often.
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Now here's where it gets personal. I chose the steel option for my first try. I didn't know how to use a brake and I've forgotten what little I once knew about welding, but I really loved using the electric cutter on steel. So with help from a friend, an oil pan was created. Naturally, it didn't fit under my side fairings. And it looked like hell. But at least I'd made a start.
My bike, a 1989 Honda CBR250, is a street bike that I race. It has full fairings that cover the sides and join at the bottom front. The fairings are supposed to make the bike more aerodynamic and they fit snugly to the bike. A gusset has already been added to accommodate the extra width of the engine guards. No room for messing around.
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To improve the chances of success for my second attempt at a belly pan, I recruited the brain of my friend, Tim. He thinks in 3D and can make anything. After 30 seconds of staring at the bike, Tim suggested cutting off the bottom thirds of the side fairings and fiberglassing them together. This would allow independent removal and installation of all three pieces. Brilliant. Just one tiny, little problem. While I understood the concept of fiberglass, I'd never actually tried it. Tim to the rescue once again.
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Drum brake calipers were used to measure the distances between the existing fairings, at the top and bottom edges, while still installed on the bike. The fairings were then removed from the bike and reassembled with brackets to maintain the correct distance.
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The paint was sanded off the outside of the fairing to ensure adhesion to the resin, using a sander attached to an air hose. I don't know how many attachments there are for an air hose, but I haven't yet met one that wasn't fun to use. Particles flew everywhere but the variable speed made it easy even for a first-time user to control.
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The fairings were turned upside down and supported with cardboard boxes from the recycling pile. A basic form is created with cardboard (to support the wet resin and cloth), wax paper (it peels off the resin after it hardens), and duct tape (to hold it all together).
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Now it's time to get down to the actual fiberglass stage. If the directions on the can of resin are to be believed, this is a very precise process, requiring exact counting of drops of hardener, precisely measuring the resin, and knowing the air temperature. In reality, the resin and hardener are slopped into an old plastic tub and mixed thoroughly, while asking, "You got that cloth ready yet?" And you'd better be ready.
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The sanded parts of the fairing and the waxed paper are liberally coated with the resin, the carefully cut fiberglass cloth is set on top, and then another coating of resin is brushed over again. Air bubbles and dry spots are carefully smoothed over. This is not a good time to move the cardboard forms underneath. Naturally, careful planning led you to set up the forms in an area where you won't be bumping into it as it cures.
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The first form may not be your last form. Despite all the measurements and care taken, there may be some adaptations required. Fortunately, fiberglass is a forgiving material. Cut off the offending parts and try again. The exhaust pipe was causing grief. Despite numerous trims, the belly pan was not fitting smoothly. Worse, the belly pan was in danger of becoming a "belly shelf" as the cuts became lower and lower. A new cardboard form was created around the exhaust pipe, and the back of the belly pan was re-fiberglassed.
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With the fit perfected, it was time to create a fastening system. Four aluminum tabs were cut out and riveted to the sides of the pan.
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Matching holes were drilled in the tabs and the upper fairings to accommodate quarter-turn fasteners. An aluminum gusset was created for the front of the fairings to be bolted on.
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Time for the task of smoothing out the fiberglass. Using bondo was another first time experience. With a lesson from Tim, I was soon spreading, smoothing and sanding bondo over the pits and rough spots of the belly pan. Much akin to drywall mudding, but with more curves, I tried for a smooth surface. But really, who is going to see the bottom of the pan? I decided it was good practice for fabricating other bike body parts. You can never have too many transferrable skills.
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Spray painting came next. Not exactly like applying hair spray, I found out. The margin for error is smaller, and the results are more visible and longer lasting. Primer, colour, and then clear coat, with appropriate re-coat and drying times, as stated on the label.
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Read the label. It will save you some grief. And watch out for overspray on the surrounding area. (No, really? I thought it was just pollen on your car!)
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Go for a bike ride while the paint dries, then a final test fitting should do. Of course, at this point you realize that the rest of your bike is not nearly as sparkly clean as the belly pan. Never mind. Apply the stickers, admire, and get ready to head back to the track.
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- Laura
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