Body Shape

[MrRoadWarrior]

My family has won pack and district races the past few years using a body shape similar to Dr. Scott Acton's design from his video. http://pinewoodphysics.com/Free_Downloads.html I notice all the wide tire races here everyone is using fenders. Has it been accepted that fenders overcome the I-beam design? How thin do the inside part of these cars get? I'm assuming 1/4" Tungsten Cubes are used.

 

[GravityX]

Aerodynamics. With fenders, the air is not encountering the full face of the wheel and improves airflow around the wheel. Many of the cars you see run in the league events will also have inner wheel covers, again to reduce air drag. The slicker the car is through the air, the faster it is. But! It's only one part of the package. Yes to the 1/4" tungsten cubes.

 

[Vitamin K]

Aero matters and fenders matter, but they're not the most important thing. The factors I would rank (in order of descending importance) would be:

Axle alignment -> Wheel/axle polish and lube -> Weight placement -> Aerodynamics

Alignment and wheel/axle prep are pretty darn close in my mind. Both are absolutely essential for a fast car.

For Pack-level races, aero is less of a factor. I don't do fenders with my kids' cars, because they really do add a lot of time if you're making them yourself.

 

[HurriCrane Racing]

At the pro level everything is important and it must all work together. You will have no chance at winning if you ignore aerodynamics. An I beam car will not beat a good Street Stock style car with fenders.

At the scout level, you can get away with much less work and still be competitive. (Unless you are unfortunate to have a league racer parent in your pack).

 

[BulldogRacing]

I think this year I'm going to make a block car, and make it a fast scout style car, that's how much body design matters in most scout races, unless like crane said you have a knowledgeable parent son team in your pack. With a good alignment, rail runner, and good fast prep you'll smoke um, have fun with the body design!

 

[LightninBoy]

Even if you don't do fenders, I recommend a surf board design over the i-frame.

 

[LightninBoy]

I think this year I'm going to make a block car, and make it a fast scout style car, that's how much body design matters in most scout races, unless like crane said you have a knowledgeable parent son team in your pack. With a good alignment, rail runner, and good fast prep you'll smoke um, have fun with the body design!

I built a block car several years ago for the pack races. It was good fun watching it smoke everyone ... Except my other wedge cars.

 

[Vitamin K]

Even if you don't do fenders, I recommend a surf board design over the i-frame.

Is this primarily a body flex issue?

 

[BulldogRacing]

A surf board design is better aerodynamics than an I beam every day of the week. Think in terms of a wind tunnel and how the air would be guided into the wheels with an I beam.

 

[MrRoadWarrior]

We haven't begun the building process yet, but it sounds like my youngest son wants to run what his brother won district with last year. Which is fine with me; He gets to cut, sand, and all the other fun stuff.

I'm going to take Bulldogs video and put fenders on my car for the old timers race.

Our District races on an old wood track, with the scout champion finishing around 2.44 seconds.

We had two cars in the old timers division hit 2.387 and 2.388 in 2015. We race March 4, so I'll let you know things go.

 

[MrRoadWarrior]

per the rules, we have to keep the stock wheelbase, but we've cut a piece off and moved it to the front. Our COG in the past has been just behind the 1" mark, so my next question is a COM of 3/4" too aggressive? Do I just have to do some test runs and find out?

 

[Rocket car]

I would keep the COM at 1"- 3/4". Any more aggressive and you will have problems on a wooden track. Test runs will show if it wiggles and looses speed.

 

[MrRoadWarrior]

I dropped the car with fenders (my bad), and the kid's original car was unstable during tests so we built a new one with only 1 oz behind the rears but still a 3/4" COM.

The scout car finished 2nd in the wolf and bears, but the car that beat him had one bad run in the Championship round and we won the overall championship. That families old timer cars were way off the pace which makes me wonder. BUT a lot of cars were inconsistent between the three lanes. The hollow body wedge looking green car was about .012 faster than our blue one. I'm looking forward to building some league cars now.