Our Tiger Den Leader built us a new track this year based on the now famous Pack 80 design. It is a huge improvement from the track we used the last couple times. He modified the design slightly using red oak instead of poplar and used exercise weights instead of the water jugs in the original design. The lines were longer than I would have preferred at 50 feet, but it all turned out to the good for my son. Most heats were decided by the final position on the track, not by who got to the end of the track first. About 6 of 30 were fast and light enough to get to the end of this long track.
Our Cubmaster posted a few early pictures last night. Take a look at his pictures here:
http://picasaweb.google.com/THEACTIONPA ... q3SAoGzRTw#
My son's space derby is the blue and yellow plane with the "13" sticker shown in the pictures. It took first place in Webelos Den and 1st place overall in the Pack finals. Ben has entered 3 Space Derbies and brought home two pack 1st place trophies and one 2nd place trophy.
This year's entry proved that light and aerodynamic along with a little wing for lift can beat the competition without a lot of work or fancy tools. The body on this year's entry was shaped using 2 sheets of 80 grit garnet paper flat on the work bench. The nose was shaped in about 2 minutes with Ben's Dremel. The total fab time was about 1 hour. Paint took about an hour for 4 coats of fast dry enamel. The paint job isn't slick or pretty, but served the purpose. There were a couple lighter entries that carried the same number of rubber bands, but they lost more speed down the track (no lift from fins or wing or poor balance?). I don't know, but it happened.
The new Cubmaster set the rubber band limit at 4. We had previously used 3 as the limit. Four bands tightly wound several times has enough force to destroy the stainless prop shaft on our ship. The eyelet twisted right open. I had a spare ready so we didn't have to miss our heat. One thing you can say for 4 bands is that a light ship can go 50 feet really quick and hit the end hard enough to jump out of the carrier onto the floor.
I made my own racer, which I since have tossed out. But it was so thin that there was air showing in places. I lacquered it for strength. I made the hanger adapter into a space frame, and hollowed the rubber band holder at the tail end, also shortening it. Then, I balanced and sanded and polished the propeller until it was as light as I dared make it. It would bend during static testing- and it was razor sharp. The whole magilla weighed 9 grams when I was done. I had to angle the propeller over to counteract the motor torque, so it wouldn't spiral around the line as it went to the finish. It looked like a cigar.