TyThompson has the tried and true approach. I am Cubmaster of our local pack, have been doing it for about 10 years and have dealt with literally thousands of cars over that time. The typical winners are either wedge or "dog bone" shape. Sometimes you will get a car so fast it amazes you, the little solenoid drops and it launches down the track like it was catapulted. Other times the exact same design will loaf along like a Yugo - a lot of luck is involded in the Derby.
You want your car as close to 5. 0 ounces as possible, because you are relying completely on potential energy to get your car on the go. We have seen people try every possible location of weight, from all of it in the back drilled in and bondo'd, to all of it in the front the same way, to thin sheets of lead distributed around. Weight in the back seems to be the most consistent winner.
In some areas they are extremely strict about how the car is made. Lathe turning of the wheels is a no-no in official competition around here for example. Polishing the wheels is usually fine, but they can't be polished / turned to an edge. People found early on that lathe turning the wheels to a very sharp "V" profile gave better performance due to less surface area and friction on the track.
I hate to say it, but fathers often ruin the contest for the kids. There is always some guy who thinks he is doing his kid a favor by ultra-engineering the car to give him an edge over the other boys. Everybody wants their kid to win, but the Derby is supposed to be about a boy building his car, maybe with some help from Dad. If he wins with a car that Dad took to work and built for him, what lesson is he learning? Every year we have to deal with this, and it is impossible to really sort out because there are some kids who can flat build a nice car, and some Dads who build some that viciously suck. Just desserts IMHO :-laf
As mentioned in the previous post, it is not unusual to have the sloppiest looking car in the race be the fastest, and that gets some of the Dads fired up when their boy's Thunderbolt Greaseslapper gets beat :-laf :-laf. One of our leaders several years back built a car out of a piece of beautiful walnut with all the tricks, and got beat badly by a kid who just left the block in raw rectangular form with some quarters stuck on for weight :-laf :-laf
To inject an element of fairness, our pack has an "Open" class race after the individual den races. In the "Open" class, anyone can race any car they want to, it just has to meet the size and weight constraints. In each Den race, we award a "Best of Show" trophy which is presented to the best "obviously built by a boy" car. In the Open race, the Best of Show is given to truly the best looking car, and there are some real doozies.
Pinewood Derby is a lot of fun. Tell the boys to do their best and cheer for the winner, whoever it is.
PS - Those with Tiger Cubs who are in their first Derby should talk to the boys ahead of time and explain how things work, that only 1 boy can win. Nowadays in much of their life "everybody gets a trophy" so it can break their little hearts when their jalopie doesn't win. It's a valuable learning experience all around, for parents and kids.
PPS - You can always tell right off the bat when a Dad has built the car. When they show up for weigh-in, Dad will walk in with a little box holding the car like it is the Hope Diamond. The kid will stand there dejectedly wanting to play with the car, but Dad will snap at him or gently smack his hand away from the car. At weigh-in, Dad watches the digital scale like a hawk and suspiciously gazes at the competition to be sure he isn't getting screwed out of a fraction of an ounce somewhere. During the race, Dad will nearly soil himself with excitement :-laf. Sadly, some Dads will cheat too, trying to add some extra weight to the car after weigh-in, so we have to have a table set up with a leader watching, after weigh-in nobody touches the car until race time. Never seen a boy try to cheat yet, but the Dads sometimes want to win just a little too badly. Had to have a talk with a couple of them over the years.
Paradoxically, nothing makes a man more indignantly outraged than getting caught doing something he knows is wrong :-laf :-laf
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