It is Pinewood derby season for the Cub Scouts. As a father of a Weblo and a Den Leader, I hope to give your some ideas on building your car. Remember, the car is meant to be a father son project. Help your boy do as much as he can.
This year, my son decided to build a "Dukes of Hazard" inspired HMMWV (Humvee). These steps can be used to make any number of vehicles.
Disclaimer: The use of power tools in tales certain inherent risks. Proper protective equipment should always be used and tools should be properly maintained. Children should be closely monitored and aided if they are to use any power tools. I am not responsible for any injury you may sustain.
Step 1: Materials, Supplies, and Tools
It was time to gather up everything we needed.
1 pinewood derby kit
additional wood (we used balsa, so as to minimize additional weight)
wood filler (sandable)
sand paper (we used 120 and 220 grit dry, and 320 and 600 grit wet)
masking or painters tape
saw (a band saw works great)
power sander (optional)
Dremel tool (optional, but very helpful).
Step 2: Pick a Design
Now that you have the items you need, it is time to find your design. You could draw your own design, or search the internet or other references as we did.
As I said earlier, my son wanted to build a HMMWV. So, we did an image search on Google for an M-998. We found these illustrations from the military training manual for the HMMWV. We decided that a "fastback" design would work best for my son's plans, so I added a couple of lines to the design.
We then printed out our design with a length of 6.5 inches, since that size best fit our block of wood.
Note: Make sure that your design meets the specifications in the rules. You may also want to check to see if there are other restrictions imposed by your pack or counsel.
Step 3: Transfering Your Design to Wood
Cut out your design, and place it over a sheet of carbon paper. Tape the paper to the wood and trace the outline.
We had to cut out four separate pieces of wood to make our design, which meant that we had to trace our design on to all four pieces of wood.
Idea: If you do not have any carbon paper, you can rub soft pencil graphite on the back of the design or another sheet of paper. You can use this in place of the carbon paper, but the transfer is not af strong.
Step 4: Get Cutting
Now it is time to cut out your piece(s). It is pretty straight forward. Remember to cut on the outside of the lines. It is easier to shave or sand a piece down than it is to build it back up. This is also a good time to even up the two sides if your are building a fender-ed vehicle.
Please note that the blade is stationary in the picture. It was posed. I aided my son in the cutting process. Father and son project, right!?! The ESS ballistic goggles were used, however. Although ballistic eye wear is not necessary, some form of eye protection is.
Step 5: Sanding, Gluing, Filling Sanding Some More.
Before gluing everything together, it is use a sander to take down all of the nicks from the saw and to help shape it. After everything is roughly sanded, ti is time to glue. Spread a thin film of glue over the piece to be glued. Adjust the pieces so that they fit properly, and let the glue dry. Let the glue cure for eight to twenty-four hours.
Now it is time to file the seems and any low areas. (think of this as Bondo for your pinewood derby. It will make the finished car look so much better).
After the filler is dry, start sanding. We used a palm sander with 80 grit just to knock the filler down, and then started hand sanding with 120 grit. Then we moved up to 220 grit. At this point your car should be fairly smooth.
Step 6: Prime and Sand (optional)
This step is for that really smooth finish. (You could skip the prime painting and dry sand to 600 grit, but the wood grain will still show through).
Lay light coats of primer down so it doesn't run. The number of coats need depends on your primer. Automotive or regular primer may need 10-20 coats before you sand. Filler primer will need less. Let the last coat dry for 2-4 hour (the longer the better).
Now it's time to wet sand with 320 grit. To do so, dip your wet/dry sand paper or emery clothe in some water and start sanding. The surface you are sanding should be wet, so you may want to dampen it with your fingers. Sand until the surface is smooth. If you sand through the prime, especially on the edges, don't worry. You need to lay down a few more layers of primer. After these layers are dry, wet sand them (this time making sure not to sand through the primer.
Now it is time to pull out the 600 grit and wet sand. When you are done, your car should be silky smooth.
Note:Do not use self etching primer. It will not work on wood. Also, Do not dry sand primer. It's not pretty.
Step 7: Painting
Choose the color you wish to use, and lay down light coats just like the primer. Your don't want runs in your paint after all of your hard work. The picture below shows my son's car after three coats on the bottom and one coat on the the top and sides. It is a good picture to demonstrate that one should use a light colored primer for light paint jobs, and a dark primer for dark paint jobs. Notice the black showing through? After a few more layers it is nice and orange.
My son chose Krylon OSHA orange. There are not a lot of color choices, but it is a great Dukes orange. An added bonus is that each coat is dry in 12 minutes.
Step 8: Window Graphics
We plan to use decals for most of the graphics, but we have painted the windows. (In the past we have painted all of the graphics, but certain small details will be easier to achieve with a decal).
We masked off the car, using blue painters' tape and plastic.
Draw the windows on and then cut them out with a razor-knife. Carefully peal out the windows, and press the tape around the edges.
Paint several light layer, and let the paint dry. Carefully remove the tape.
Note: Make sure to give the base coat enough time to cure be for masking. I suggest waiting at least 24 hours. Also, don't leave the tape on too long. Even though it should be able to stay on up to a week without problems, the shorter the time it is on the less likely it will leave residue.
Step 9: Finishing Touches
Normally, I would paint all of the graphics, but due to the small details and time constraints, we decided to use stickers. We used white printable stickers and printed graphics we found on a Google image search. We cut out the stickers and placed them on the car.
We then laid down many light coats of clear paint.
Note: Even after using balsa wood for the added pieces, the car weighed 6.1 oz. We had to hollow out the under side byr drilling and using the dremel tool.