Running a Space Derby, Part 1
"These notes are a vastly expanded version of a presentation that I made at the
Arapahoe District Roundtable, Denver Area Council, in May 1999."
-- Steve Allen, Pack 467, Englewood, Colorado.
Background.
In a space derby, scouts fly balsa wood rockets driven by rubber band powered propellers along fishing line.
The rockets are built from kits sold at the scout shop.
It's much more challenging to host a space derby than a pinewood derby,
thus it's essential that you prepare properly.
If you're prepared, you and your scouts should have a good time.
Official sources of space derby information.
The Cub Scout Leader How To Book has a space derby section.
The BSA book, Cub Scout Grand Prix, Pinewood Derby Guidebook,
has a brief section on building a rocket.
When and where should you hold a space derby?
Though asuccessful space derby can be held outdoors, an outdoor space derby is somewhat risky.
Rain is an obvious hazard; less apparent is the dramatic, often unfavorable effect that a
moderate wind can have on the flight of a rocket.
My pack held a race outdoors in a swirling wind and most of the rocket flights were disappointingly short.
If this is your first space derby, hold it indoors -- you face enough challenges already.
If you do hold a space derby outdoors, try to erect the gates that hold the fishing line on a hard level surface.
Small parts sometimes go flying during a space derby; they are very hard to find in grass.
How long will a space derby take?
A space derby takes longer than a pinewood derby with a comparable number of racers.
A Denver-area pack that regularly puts on a space derby runs aheat every 3 minutes.
With a 6-lane race course that's 120 potential racing slots in an hour,
though some of those slots will inevitably go unused.
The pack races 40 scouts in an hour, letting each participate in at least 2 heats.
If your space derby is poorly organized, the heats will go much slower and you may not have
enough time to let scouts race twice.
Don't race too much.
BSA produces materials and instructions for three Cub Scout races, the pinewood derby, the rain-gutter regatta,
and the space derby, but three races a year may be too many for a pack.
Assuming you hold a pinewood derby every year, you may want to hold a raingutter regatta and
a space derby in alternating years.
If you choose to hold all three races in a single year, spread them out.
You could also make the raingutter regattaor the space derby optional.
Provide alternate activities for scouts who aren't racing.
A space derby (and a pinewood derby) involve a good deal of idle time for scouts.
Most only race twice and relatively few win.
Those eliminated in the first heats soon tire and may want to leave.
Those scheduled for later heats get bored as they wait.
To reduce boredom, plan a few separate events for boys who aren't racing.
Make the events optional -- it's counter productive to force scouts to participate
in these events if they are fascinated by the races.
Announce the alternatives at the start of the meeting.
As the initial excitement of watching others race diminishes, remind scouts of the alternatives.
For example you might establish a "mummy wrapping" station.
Pair the boys as they arrive at the station, giving each a roll of toilet paper.
Each boy, in turn, wraps the other from head to toe.
During our 1999 pinewood derby,we set up a station where boys could built small catapults.
Every scout visited that station and every scout went home happily clutching a catapult,
even those who's cars had performed poorly.
These alternative activities don't have to be elaborate.
You could also set up a tug-of-war or a bean-bag toss with small prizes.
The How To Book has more ideas and there are pages of games on the Web.
You could also reduce boredom by telling racers to arrive just before their pre-assigned race time,
say Wolves at 6:30, Bears at 7:00, Webelosat 7:30.
Buying space derby kits
Comparative derby kit costs from the 1999 Scout catalog.
When purchased in lots of 8, kits cost
Pinewood Derby
Raingutter Regatta
Space Derby |
$3.11
$3.17
$4.00 |
Warn the Scout Shop of your planned purchase.
If you're in a large pack, the Shop may run out of rockets and space derby supplies (extra rubber bands, etc.).
It happened to me.
A salesperson suggested calling several weeks before my next space-derby purchase to alert them.
Avoid foam rockets.
BSA briefly sold space derby kits withStyrofoam rocket bodies.
Styrofoam had a serious flaw: it melted when spraypainted.
All space derby kits are supposed to now have balsa rocket bodies;
check your kits after you buy to make sure there's no foam.
Hold a practice race
Because many more things can go wrong during a space derby than a pinewood derby,
I highly recommend holding a practice space derby a few days before the real races.
We opened our practice session to the entire pack but only a half dozen scouts showed up, the perfect number.
A practice session gives race supervisors a chance to refine their race procedures;
it may prove to be the difference between success and disaster
Use mechanical winders
It's hard for younger scouts to wind rockets with their fingers.
Adults can have a hard time too.
Fingers slip or minds lose count.
If you plan to wind propellers by finger, which I advise against, assign the task to a group of adults.
It takes an adult about 30 seconds to wind a propeller 100 turns.
Wear gloves to protect against the inevitable slips.
Model airplane suppliers sell hand-cranked mechanical winders that make it much
easier to wind propellers provided
(1) there's an easy way to attach the winder to the rocket and then detach it
(2) practiced adults handle the winders. More on both later.
These winders have a small hand-powered crank on one side that drives a rotating hook on the other side.
One turn of the crank might turn the hook 5, 10, or 15 times, depending upon the design of the winder.
Thus 20 turns of the crank on a 5:1 winder will put 100 turns into a rubber band.
Once you've practiced, it takes about 8 seconds to wind a rocket with a 5:1 winder;
not counting the time it takes to attach and detach the winder.
Higher ratio winders, which boast 10:1 and 15:1 ratios, wind faster but they break fairly
easily because of the increased stress to which their gears are subject.
A good quality 5:1 winder is more than adequate for a space derby.
Recommended winder.
The Peck-Polymers 5:1 winder works well.
It is widely used by model airplane enthuaists.
I purchased it through the mail from F.A.I. Model Supply, P.O. Box 366, Sayre, PA 18840-0366, 1-888-882-9873.
It lists for $8.75; but they gave me a 25% discount for Cub Scouts.
Shipping cost $3.50 for 3 winders.
You can also buy these winders from Peck-Polymers, P.O. Box 710399, Santee, CA 92072-0399, (619) 448-1818.
Colpar Hobbies in Denver sells them for list price.
Don't buy the flimsy blue winders sold at the Scout Shop or through the Scout Catalog.
They work very poorly.
Hand cranked drills:
Instructions that come in the space derby kits suggest using hand cranked drills as winders;
drills will do the job but they are much more expensive than 5:1 winders.
Electric drills make poor winders because, as far as I know, there's no easy way to count the turns.
If you wind the same propeller several times with the same drill for a fixed amount of time,
you'll find that the resulting number of turns is highly variable.
High quality mechanical winders work much better.
Recommendation: Use mechanical winders.
Have an extra winder on hand in case one breaks.
Attaching winders quickly
Put a winding loop in the tail.
As noted above, mechanical winders work great at a space derby if they can be quickly attached and detached.
The instructions that come with the space derby kit show a hand drill attachedby a special fitting
to the dowel in the rocket’s tail.
Once attached, this combination works great.
Unfortunately, it’s very time consuming to attach and detach the fitting.
Winding is much easier if you put a windingloop in the rocket's tail using 4-inch cable tie strips.
Loop 2 rubber bands tightly around the dowel and through the tie strip as shown below.
Then pull the rubber band tight.
Pull the rubber bands through the rocket with a longhook fashioned from coat hanger wire.
To wind the rocket, hook the mechanical winder through the loop of the tie strip.
(Tail winding loops can also be made from nylon washers and other rigid items,
but cable ties work well and cost little.
Rubber "O" rings don't work as well because they are too flexible.)
It takes 2 people to wind a rocket with a mechanical winder, a holder,aged 10 or higher
(see comments below, 10 may not be old enough), and anadult cranker.
The holder grasps the rocket and propeller as the crankerhooks the winder to the winding loop,
pulls the rubber band out several inches,cranks, and then eases the dowel back into place, detaching the winder.
The whole process takes less than 15 seconds once the winding team gets the hang of it.
(There's definitely a learning curve.
Ask winding teams to practice.)
Let practiced adults crank; let Webelos or older scouts hold and load.
As noted earlier, winders work great in the hands of adults who have practiced.
Too many problems arise when winders are in the hands of boys.
At our 1999 space derby I tried to turn winding completely over to a group of 6th, 7th and 8th grade Boy Scouts.
Once the Boy Scouts practiced, they were great holders.
They also did a good job loading rockets into the starting gates, though they needed occasional adult assistance.
They had problems cranking.
Recommendation:
Ask practiced adults to serve as crankers.
A small group of practiced Webelos Scouts could probably serve as holders and loaders during a space derby.
Practiced Boy Scouts are certainly capable of holding and loading.
Warning: I haven't yet tried using Webelos as holders, so I recommend that several practiced
adults stand by, ready to step in if the Webelos falter.
Pre-assemble or you'll regret it
The propeller assembly that comes with space derby kits has several small parts that scouts can easily lose.
Even if parts aren't lost, scouts and parents are extremely likely to assemble propellers incorrectly.
In 1998, we let scouts and adults assemble their own propellers.
Incredible as it seems, 30 out of 45 propellers arrived at check-in incorrectly assembled.
In most cases the flaws were so serious that they had to be corrected before the rockets could race.
The most common fault was a backward propeller, which couldn't be wound.
Many rocket builders also omitted the plastic sleeve that fits on the propeller wire, leading to increased rubber band breakage.
Bushings were also absent, undermining propeller performance.
The urge to put propellers on backwards is overwhelming.
In 1999, when we preassembled propellers, one parent called to tell me that her son's preassembled propeller was backwards.
It was not.
Another parent, convinced someone had made an error, took his pre-assembled propeller apart and put it back together --backwards.
I fixed his handiwork during check-in the night before our space derby.
If you leave the winding-loop assembly to scouts and parents, problems will surely arise,
even if you distribute special instructions with the kits.
Some will ignore the loop altogether.
Others will devise their own creative but non-functional loops.
Pre-assemble the cable tie, the dowel,and the rubber bands.
Tighten them firmly so they won't come apart.
If you don't pre-assemble, you'll have to fix many loops at check-in.
Why not do it now?
Recommendation:
Purchase space derby kits for the boys.
Ask a group of parents to pre-assemble the winding loop, i.e. the cable tie, the dowel, and 2 rubber bands.
The parents should also pre-assemble the propellers.
Repack the kits and distribute them.
Pre-assembly vastly reduces race-day problems.
The propellers in the kits are of uneven quality;
while assembling, make sure the ridge against which the wire pushes as the rubber band turns is in good shape.
Return kits with bad propellers.
Once you get the hang of it, it takes 2 1/2 minutes to unpack a space derby kit, assemble the propeller
and the winding loop, and repack the kit.
Test wind your first attempts to make sure you're doing it right.
Remember the ancient proverb, "Foolish is the pack that fails to pre-assemble."
Note to BSA
BSA could improve space derbies substantially if it:
- Sold higher quality mechanical winders.
- Put pre-assembled propellers in the kits.
(Inexpensive wind-up airplane kits all have pre-assembled propellers.
Why not this one?)
- Improved the quality of the propellers.
The ridge against which the propeller wire pushes is inadequate and does not hold up well under repeated fingerwinding.
- Put a modified plastic dowel, something like that shown below, in the kits.
This would make tail winding simple.
Common rocket assembly flaws and the need for early check-in
Even though you have decided to avoid disaster by pre-assembling, scouts are still
likely to make several rocket assembly mistakes.
Problem: No notches for dowel or inadequate notches.
If you follow my pre-assembly advice, this will probably be the #1 problem observed at check-in.
The dowel must rest in fairly deep notches cut into the rocket body.
Without notches, the dowel will slip when the propeller is wound.
Check-in fix: cut notches.
Problem: Incorrect number of rubber bands in the rocket.
Check-in fix: add or remove rubber bands.
(Hint: the rubber-band count will be right if you pre-assemble the winding loops.)
Problem: Stuck nose button.
This can easily happen if the nose button is inserted when the paint is still wet.
It is only a problem if you need to change the rubber bands.
Check-in fix:
Ignore the problem unless a rubber band is broken or the rubber band count is wrong.
(Hint: the rubber-band count will be right if you pre-assemble the winding loops.)
Problem: Winding loop too small.
If you pre-assemble cable-tie winding loops, a minor problem will arise if a scout tightens his
cable tie and makes the loop too small for the winder.
Check-in fix: grasp the dowel with one hand and the cable tie with the other,
pull them apart and get someone else to thread a new cable tie through the gap.
Clipoff as much of the old cable tie as possible and fashion a loop from thenew cable tie.
Problem: stripped propeller.
If a scout winds his propeller numerous times before the races, he may strip the tiny ridge that
the propeller wire pushes as the rubber band turns.
Check-in fix: if the propeller wire is long enough,
you can pull it out and then bendit into a "U" that will hold the propeller.
Have extra pre-assembled propellersready to install if this doesn't work.
Problem: Hanger protrudes into the rubber band chamber:
The hanger on top of the rocket must not protrude into the hollow chamber in the center of the rocket body.
If it does, it will interfere with the rubber band.
Unfortunately, the picture on the space derby kit box shows a hanger that has been inserted too far;
rocket builders who imitate this picture will attach the hanger incorrectly.
Check-in fix:
Pull or cut the hanger from the rocket body.
Cut a new notch for the hanger if the old one won't work, and reattach the hanger properly.
There are at least two ways to reattach a hanger quickly.
(1) Use hot glue.
(I advise against instant glue because it will glue fingers, eyelids, etc. together in a flash.)
(2) Drill a hole in the hanger, slip a 7 and 1/2 inch plastic tie strap throughthe hole, wrap it around the rocket body, and tighten.
Problem: Hanger on backwards.
The rounded end of the hanger must point forward.
If it doesn't, the rocket may pull free of the carrier during flight.
Check-in fix: You can remove and then reattach the hanger, as described above,
or you can simply wait for the races and the tape the hanger to the carrier so it won't pull free.
If you decide on the latter fix, put a note on the plane so the race officials will know what to do.
Problem: Hanger not glued on tightly.
If the rocket builder attaches the hanger with too little glue or doesn't allow the glue to dry thoroughly,
the hanger may pull off on race day.
It's hard to detect this flaw during check in, thus rocket doctors should be ready to fix it during the races.
Fix: Reattach the hanger with hot glue or with a tie strap as described above.
Recommendation (and I really mean it):
Have a careful pre-race check-in at least a day before the races.
The check station crew should include the rocket doctors who will make trackside repairs during the races.
Experience gained at the checkstation will be invaluable during the races.
Tape the following check listto the check-in table.
Notches for dowel present and sufficiently deep.
Cable tie loop OK, loop large enough
2 rubber bands, not broken, not lubricated (more on lubrication later)
Propeller turns freely
Propeller ridge not stripped
Hanger securely attached, rounded end forward, does not protrude into rubber band chamber.
Equip the check station crew with the following items, all labeled with the owner's name.
Needle-nose and regular pliers
Scissors
Utility knife
Long piece of stiff wire with a hook at the end. Use it to pull rubber bands through the rockets.
Extra BSA space derby rubber bands (Purchase in lots of 24 from the Scout Shop)
Pre-assembled propellers
Extra tie strips
Tape
Hot glue (If loose hangers are to be reattached with glue)
7 1/2 inch plastic tie straps
an electric powered drill, and drill bits
(If loose hangers are to be reattached with tie straps.
Battery powered drills work great if there is no near-by outlet.)
Advise parents of the importance of day-early check-in.
Parents in my pack didn't appreciate the importance of day-early check-inin 1999.
As a consequence fewer than half our rockets were checked in the day before the space derby.
I couldn't bring myself to turn away the rockets that appeared on race day, many at the last minute.
Despite my efforts to fix these late arrivals, a number of problems slipped through,
complicating our races a great deal.
Beg parents to bring rockets to check-in.
Running a Space Derby, Part 2.