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Transforming that Block into the Ultimate Derby Car

After waiting for a whole year, the time has finally arrived to transform a
pine block into the ultimate derby car. I know it is tempting to draw a few
lines and start cutting. But before that, ask yourself two questions:

1. Where will the weight go? Depending on how much wood you remove,
you will likely need to add between 2.5 to 3.5 ounces of weight. Too
often car builders don't consider the need to add weight until after the car
is shaped and painted. The time to deal with the weight is now, before
cutting the block. So, figure out what kind of weight you will be using and
where it will go. Speaking of where the weight will go ...

2. Does the design allow the weight to be placed near the rear axle? For
best performance most people recommend locating the center of gravity of
the car 1 to 1-1/2" in front of the rear axle. So, put about 2/3 of the
weight in front of the rear axle, and the rest behind the rear axle (For
cars with a light front end, you may need to put 3/4 in front and 1/4

Sketching - Now that you know where the weight will go, draw the side
profile of the car on both sides of the block, and draw the top profile on
the bottom of the block. Then draw the location of the pockets/holes
for the weight.

Rough Cutting - The weight pockets/holes are much easier to create while
the block is rectangular. So, begin the shaping process by creating
the weight pockets/holes. Then begin shaping the block by removing the wood
from the top of the car (using the drawing on the sides of the car), then
remove the wood from the sides of the car (using the drawing on the
bottom of the car).

Shaping - Shape the car using a rasp, file, coarse (60-grit) sandpaper, etc.
If you have a steady hand, a Dremel tool is handy. If there are any gouges
(boo-boos), fill them with wood putty.

Sanding - When the car is shaped as desired, sand the car with medium
(150-220 grit) sandpaper, followed by fine (400 grit) sandpaper. If you
want a nice finish, make sure that the car is very smooth. There should not
be any visible marks on the car (with the possible exception of fine
sandpaper marks on the bottom of the car, or on the back of the car where
the wood end-grain is visible).

Preparing to Paint - The car is now ready to paint. I recommend inserting
a long cabinet screw into the bottom of the car (screw it into a weight
pocket if present) as a painting handle. The screw only needs to go deep
enough to be firmly in place. Be careful to not run the screw completely
through the car! Now locate a place in a dust-free, shaded area where you
can hang the car while it dries. In this location hang a short wire between
two nails or screws such that the car can be suspended from the wire without
touching a wall or other object.

Painting Protection - If you will be using spray paint, put on eye and
breathing protection. Then place a plastic bag over the hand that will hold
the car and secure the bag with a rubber band around the wrist.

Painting - Paint the car following the recommendations on the paint can.
For spray painting, I recommend starting with several coats of primer followed
by 2 to 3 coats of acrylic-lacquer paint. For brush painting, acrylic paints
work well.

Drying - Hang the car to dry between coats. Use a binder clip or
clothespin to attach the screw to the wire. After the paint is dry and
before applying the next coat of paint, sand the car very lightly with
600 grit sandpaper and wipe off the paint dust.

Detailing - The car is now ready for numbers, decals, or other
decorations. After decorating, you may want to apply a clear coat finish.

Whew! That was a lot of work, but the car body is complete and it looks
great. But if you want the car to be fast, your work has only begun ...

From Pinewood Derby Times Volume 1, Issue 3

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