SPACE DERBY
Cub Scouts will find the Space Derby exciting. They blast off with models of miniature "rockets" propeller-driven and powered by three rubber bands that travel along a heavy monofilament fishing line. The official space derby kit includes all necessary materials and instructions for building. Join in the fun as the countdown begins for the space race of the century.
PACK 308 REGULATIONS FOR BUILDING THE SHIP
Space Derby Rules: All rockets must pass the following inspection to qualify for the race:
1. Only basic materials supplied in the Official BSA kit may be used. The hanging devise supplied in the kit must be used.
2. The nose cone (propeller assembly) must not be glued in place on the nose of the rocket. A notch or groove should be formed in the tail of the rocket to seat the band holding dowel. The band holding dowel must not be glued in place. (These rules allow band replacement in case of breaks)
3. The rocket body may be no longer than 7 inches, not including the propeller and fins. Width 2.75 inches -There are no restrictions on the weight or design of the rocket. Three rubber bands per rocket.
4. There are no restrictions on the weight or design of the rocket. Rockets may be detailed in any way as long as it does not exceed length restrictions, is flight worthy, structurally sound and does not interfere with another rocket during the race.
5. Rockets with wet paint will be disqualified
6. Scout may use graphite powder between the propeller and the bushing if desired. Other forms of lubrication are prohibited.
Tips For Construction of Rocket Builders and Preparing for Flight
(these are tips used by the "Rocket Masters" use at your own risk)
SHAPING & CARVING THE ROCKET
-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.
-Rocket body is shaped as small as possible. FAST ROCKETS HAVE A MINIMUM PROFILE.
-Inside of body is hollowed out to reduce weight. If possible, select the lightest body you can obtain. LIGHTER ROCKETS GO FASTER.
-Use a sharp knife for cutting the grooves for the hanger fitting and fins. A dull knife will crush and splinter the balsa wood. bullet When you start to carve, remember that the end with the small hose is the rocket nose.
- A new 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.
-Rocket is balanced fore and aft when a pin is inserted in rocket carrier hole.
-Plastic hanger is fastened securely to body.
-Groove for rear dowel is deep enough so dowel does not twist when rubber motor is wound tight.
MECHANICS OF THE ROCKET (PROPELLER ASSEMBLY)
-Do not glue the front nose/propellor 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!
-Propeller is balanced. Sand if necessary.
-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.
-The propellor should have the rounded shaft-end pointing into (touching) the space derby (this makes the bending of the wire easier and it reduces friction).
-Propeller wire is as short as possible. Notch on propeller engages propeller wire securely.
-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!!!
- 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!
-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.
-Propeller nose button is lubricated with graphite.
Rubber Bands
-Lubricate the rubber bands before the derby. This prolongs the bands' life and power and will help reduce the possibility of breaking during the competition. They can be soaked overnight in castor oil. Or mix two parts green soap, one part glycerin, and one part water and rub the mixture on the rubber band about an hour before racing.
-Have extra boxes of rubber bands on hand. Remember, it takes three rubber bands to fly each ship properly.
Experienced rocket racers "warm up" their space ships by gradually winding the rubber band motornumerous 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 streatch the baloons before blowing them up!).
Winding Rubber Bands
-A small hand drill is excellent for winding rubber bands. It also helps speed up the event. Check the ratio of the drill by making one revolution of the crank handle and count the number of times the chuck turns. Most drills average a one-to-four ratio; thus it would take 40 turns of the crank to give 160 winds on the rubber band motor.
- When using the hand drill winder, it's best for one person to hold the rocket and propeller while another stretches the bands about 12 to 15 inches beyond the rocket tail and turns the rubber bands, he gradually shortens the distance between him and the rocket. bullet For a more evenly matched race, wind all rocket motors the same number of turns. For 100-foot launch lines, 150 to 170 winds should be sufficient.
Finish
- Painting and decorations are encouraged. Use your imagination.
-Do not apply too much paint to the outside unless you sand between each coat. Decorate the rocket with bright colors.
-Rocket body is waxed to a high gloss to decrease wind resistance. á Fins are accurately aligned so rocket flies straight.
Space Derby Pre-Race Check List
1. Propeller is balanced. Sand if necessary.
(Remember to learn the direction to spin propeller THIS SHOULD BLOW WIND TO THE REAR OF THE CRAFT)
2. Do not cut the propeller wire too short.
3. Rocket body is shaped as small as possible. FAST ROCKETS HAVE A MINIMUM PROFILE.
4. Inside of body is hollowed out to reduce weight. If possible, select the lightest body you can obtain. LIGHTER ROCKETS GO FASTER.
5. Plastic hanger is fastened securely to body.
6. Groove for rear dowel is deep enough so dowel does not twist when rubber motor is wound tight.
7. Rubber bands have been tested to select the most powerful. Lubricate rubber bands in castor oil or a glycerin/soap mixture.
8. Propeller nose button is lubricated with graphite.
9. Rocket body is waxed to a high gloss to decrease wind resistance.
10. Fins are accurately aligned so rocket flies straight.
11. Rocket is balanced fore and aft when a pin is inserted in rocket carrier hole.
PREFLIGHT INSPECTIONS
1. Rockets are to be submitted to the registration table.
2. Each rocket will be inspected, registered and assigned a sticker with a spacecraft number.
3. After registration, rockets will be held by "Space Command" in the designated space hanger until race time.
4. If at registration, a Rocket does not pass inspection, the owner will be informed of the reason for failure, and will be given time within the official registration period to make the adjustment.
5. The rocket you compete should be a new rocket, with a balsa wood body, not one built in a previous year.
THE RACE
1. An auto winder will be used on race day. Each ROCKET will be wound the same amount of turns.
2. Prior to each heat, rocket numbers and lane assignments will be announced. Pilots are to take their rocket from the space hanger and give them to the official winder and then take their position at the finish line. Upon completion of the race, "Space Command" will give the rocket back to the pilot to place back in the designated space hanger.
3.At registration judges will assign a number to the rocket and separate it by rank.
4. Once the rocket is submitted for entry, no further adjustments can be made except in the case of mechanical failure (see 6).
5. The race will be double elimination. A rocket must lose twice before it is eliminated.
6. Any entry that experiences a mechanical failure will be allowed to re-race if it can be repaired during the same heat. It will count as a heat loss if it cannot be repaired prior to the beginning of the next heat. All repairs of this type must be done with "Space Command" observing and certifying as to its flight worthiness.
7. In the event that all rockets does not reach the end of the track, the one that goes the furthest is declared the winner.
8. One Rocket Only per scout.
9. Racing volunteers are only allowed in the Space Track area.
10. Race by rank with Tigers racing against Tigers, Wolves against Wolves, Bears against Bears, etc.
11. No late registrations will be accepted after den has started the race
12. Racing will be conducted using the Lane Rotation Method
13. All rulings by "Space Command" are FINAL.
RACE SUGGESTIONS FOR PACK ORGANIZERS OF THIS EVENT
1. To stage the race, boys wind up their rocket's motor (rubber band), then hook the rockets over the guidelines, centering the rockets between the vertical dowels and locking the propellers behind the horizontal dowels on the starting gate. Start the countdown and fire at 'zero' by lifting the rear of the starting gate frame which releases the rockets.
2. Run the race in heats, up to four contestants at a time. Boys work hard on their rockets, so each boy gets to try at least twice instead of eliminating him from competition after the first race. For example, in a 6-boy den, try heats of three boys each. The winner of each heat goes into the den finals. Then race the other four again with the winner competing with the other heat winners for the den championship and entry into pack finals.
3. Recruit adult partners as your flight operations team - two as starters with green flags, two as judges with checkered flags, and two as gate-keepers to line up the boys. Use other adults as inspectors, scorekeeper, etc.
4. Leaders should have extra rubber bands and props handy for emergencies. Remember that it takes three rubber bands to fly each ship properly.
5. To save time, whenever a ship gives any trouble, pull it off the line and run it with the last heat. Allow boys to wind propellers before coming to the starting gate.
6.Use Power Pro fishing line. Power Pro is a high-tech "super-braid" line that has almost zero stretch and is considably thinner for a given pound test. It's surface is also very slick. The 60 lb test I used is about the same diameter as typical 20 lb mono. I tested it in the back yard before deciding to use it and my test rocket required about 30% fewer turns to go the 50 feet verses regular Mono and got there quicker too. This is fast stuff and I highly recomend it to anyone wishing to tune up their track. The no-stretch property of this line makes it easier to get each lane set to the same tension also.
7. Track:It is also nice to load the starting gate with 4 space derbies. I could not imagine what 6 lanes would be like!
8. 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.
9. 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.
10. Tie several (5) pieces of cloth at and just beyond the finish line. This acts as a bumper stop without damaging the propellers.
11. Carefully look at the illustration in the Cub Scout Leader How-To Book.
12. 100 turns, 3 rubber bands for a 45 foot run. To reduce rubber band breakage, do not wind more than 100 turns.