Overview

The Space Derby is similar to the Pinewood Derby or Raingutter Regatta except that the models are miniature 'rockets' -- propeller-driven and powered by two or three rubber bands -- that travel along a heavy monofilament fishing line. The rockets are carved by the boys, with the guidance of their parents or other family members. Space Derby kits with building instructions are available at the Scout Shop.

Track Construction

• Use the design in the Cub Scout Leader How-To Book, pages 9-44 through 9-47,  ISBN 0-8395-3832-4.  Do not deviate from the measurements.  The 4 lane design fits nicely in a large van (or any vehicle that can handle a 4x8 sheet of plywood). It is also nice to load the starting gate with 4 space derbies.
• Measurements that are NOT included: The upright dowels (to stabilize the space derby in the starting gate) should be 3 inches tall and spaced about 2 inches apart.
• Thread the monofilament fishing line through each eye on the gates back and forth. Do not make separate lengths of line for each lane.  This makes it easier to make all the lanes the same tension by simply pulling the gates away from each other.  Weigh down the starting and ending gates with sand bags.
• Tie several (5) pieces of cloth at and just beyond the finish line.  This acts as a bumper stop without damaging the propellers.  Carefully look at the illustration in the Cub Scout Leader How-To Book.

100 turns, 3 rubber bands for a 45 foot run. To reduce rubber band breakage, do not wind more than 100 turns.

• There are many alternative non-rocket designs such as: cruise missiles, boats (Titanic is always popular), planes, jets, etc.
• The little plastic straw MUST go over the hook (not just the shaft as the drawing in the space derby kit illustrates) This is where the rubber bands will hook on - the wire hook will cut the rubber bands without the plastic straw liner!!!
• Lubricate the rubber bands (spray silicon, ethylene glycol, castor oil, ...)!  Stretch them numerous times before loading, hand wind the bands numerous times before races (20 winds, then 40 winds, then 60, 80, 100) -- this helps relax the elastic properties of the band and makes it more pliable and durable (this is exactly why the clowns stretch the balloons before blowing them up!).
• The plastic dowel at the rear of the space derby to hold the rubber bands MUST be kept from rotating (groove out the back so the dowel can sit in it!) - do not glue it!
• Do not glue the front nose/propeller assembly into the front of the space derby.  It is pulled off to re-load new rubber bands!
• Do not glue the back dowel onto the rocket.  It is pulled off to re-load new rubber bands!
• The propeller should have the rounded shaft-end pointing into (touching) the space derby (this makes the bending of the wire easier and it reduces friction).

Tips for Rocket Builders:

• Reduce air friction or "drag" by making all surfaces as smooth as possible. A blunt, rounded nose causes less drag than a sharp nose. A good design has all leading edges rounded and trailing edges tapered to reduce the drag.
• Rubber bands should be lubricated before the race. They are the "motor" and must be strong and flexible.
• Use a sharp knife for cutting the grooves for the hanger fitting and fins. A dull knife will crush and splinter the balsa wood.
• When you start to carve, remember that the end with the small hose is the rocket nose.
• A potato peeler is good for carving the shape.
• To help increase the rocket's speed reduce the wall thickness to a minimum of 1/8 inch. Do not weaken the area around the hanger (carrier) or carve away the nose button circle.
• Do not apply too much paint to the outside unless you sand between each coat.
• Be careful not to get glue on the plastic carrier, especially in the holes through which the monofilament line runs. Glue can interfere with smooth operation.
• Make the propeller shaft as short as possible by bending it close to the prop. Cut off the excess wire with wire cutters.
• Test the rocket's balance by hanging it from a string through the hole of the hanger fitting. If the rocket is nose-heavy, carve or sand a little wood off of the end. It it's tail-heavy, remove wood from the tail area.

Dens may wish to secure a 100-foot length of 50-pound monofilament fishing line for test runs in the backyard before the derby. Tie the line to a tree or post and string the rocket carrier on it. Tie the other end to a tree about 100 feet away. Make the line as tight as possible.