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In Reply to: Off topic. Cub Scout Pinewood Derby engineering posted by Al Nico on February 24, 2007 at 16:19:00:
I remember doing that waaaaay back when and being greatly dismayed when my super-aero design was absolutely dusted by big sleds with a lot of weight in them...I don't think aero should be ignored but make sure (as it sounds you are) to focus on maximum permitted mass and minimizing rolling resistance.
Check the tracking of your car to minimize hunting left and right as it rolls down the track - as it bumps the sides (or center guide) it scrubs off speed.
Follow Ups:
Thanks Caffienator.The car is 4.99 oz. It goes so straight that it exactly stays next to a line in the kitchen floor for over 15 feet.
We just helped a friends kids in another pack and they got 2 trophies last night.
The weight in the far back makes the weight travel further down the sloped part of the track. The light front with wheels pushed forward makes for easy direction changes due to the extra leverage and low mass.
Wow and your cub scout did all that by his self?LOL pinewood derby that the windup string derby things are something for the dads to compete with each other.
My son and I built a Tomahawk cruise missile looking string racer when he was in scouts I modified the prop like we use on our control line speed planes and some other things used some competition rubber. the result was the torque was so much it wrapped itself around the string and got blown away by a brick hanging from the string LOL
funniest part is my son now maintains the radar systems on the USS Shiloh CG-67 one of the nastiest guided Missile cruisers in the Navy.
Went through this years ago when my three boys were in scouts. They collected beau coupe trophies for heats won and design. Aerodynamics are nominal given the speed and mass of the car. I suggest crafting a beautiful car that looks as nice as it is fast. This opens the door for design trophies. Be creative with the design. You can have a unique and beautiful car and still have low drag. If allowed carve the bottom of the car like a boat hull - try to reduce ground effect. If you're concerned about aerodynamics then you should be concerned about ground effect (generally the raised part of the tract if very close to the bottom of the car. Don
Ground effect is a subject I am light on. We kept the car a little less than the 3/8" minimum clearance from the track. I do seem to recall that wind resistance under a car can be higher than over the top. The stability of the car is excellent.
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