Space Derby


The Space Derby will take place during our November Pack Meeting.  The Space Derby is friendly racing with no trophies awarded or results tracked.   The real goal is to have fun with your son building a rocket.  With that in mind, challenge your son to do as much of the work as possible.  You might be surprised what he can do.   You will find he will be more proud of a square, self-decorated rocket where he has done most of the work, than he will be of a perfect Apollo-13 replica that you build for him!

We have a Space Derby "track" that has four lanes.  We will line the Scouts up by rank starting with the Tigers, and race four at a time.  There will be adult winders at the head of the line winding the rockets for the boys.  Boys can get back in line after their race and race multiple times as time allows.

This is a Scout only event: no siblings may race a rocket.

Rocket Assembly Instructions for Space Derby Rocket


Here is a series of photos I took as I assembled a sample space derby rocket.  I wanted to create a step by step guide to help you and your son be successful in your rocket build.  Although the picture on the front of the kit is a round rocket, and my rocket is mostly round, there's no reason your rocket needs to be round!  Feel free to use your imagination.

NOTE: Use 2 rubber bands.  We will use 2 rubber bands for racing.

If you find an easier way to do these steps, let me know so I can publish it for the pack's benefit.

Lessons learned from last year's Space Derby:
  • Because of the glue involved, this is a multi-night project.  Some rockets showed up last year with wet glue and parts falling off.  It's probably not a good idea to wait until Derby night to start building your rocket!
  • The lighter the rocket, the faster/farther it will go.  My rocket example below was pretty heavy and did not go very fast.
  • Be careful not to lose the tiny brass insert when you open your rocket kit.  You will need it later.

Here are the two body pieces right out of the box.



Sand the inside rear edges to create a notch.  The rear is on the right in the above picture (the end with the large opening).  This notch will be used for the white plastic piece that holds the rubber band.  Without the notch, the plastic piece will spin and you will lose power.  I used 60 grit sandpaper.


Here is what your pieces should look like once you have created the notch.  Make sure your notch is deep enough.  Test fit it with the little plastic bar from the kit.


I used Elmer's Glue to attach the pieces together.


I smeared glue on both sides, aligned the pieces and pressed them together.



Insert the hub (small, round, white plastic piece) into the nose hole to make sure the pieces are properly aligned.


Move the hub in and out a bit to make sure it is not being glued in.  I left the hub in while the glue dried over night.


Put something heavy on top and let the glue set up overnight.  Thanks Harry Potter!


This is a good step for mom and dad to help with, as it involves some precise measurements and a knife.  Make a 1 inch mark three inches from the nose and three inches from the tail of your rocket.  Refer to the directions that came with your space derby kit for a nice diagram of this measurement.


Now cut out a 1" notch where you marked.  I used a utility knife, and it was probably not a very good choice.  I had to work on it quite a bit to make the notch big enough for the hanger.  Probably some wide cutting tool would be more effective.  The balsa wood is very soft so any sharp piece of metal should do the trick.  You'll notice that later I had good luck cutting the balsa wood with a putty knife.  It may have worked here also.


Test fit the hanger to check your notch size.  Remove it when you are done testing.


Now it's time to shape the body.  I used 60 grit sand paper and sanded it down to size.  This will probably be a bit tedious for a younger child; I will find out shortly when I have my kids make theirs.  I read online that a potato peeler would work, but I tried it and didn't have any luck.  Of course a knife or dremel tool would make quick work of balsa wood, but I am trying to stick to tools that are safe for my Wolf Scout.  I found that using a sanding block, or even wrapping the paper around a ruler for support, was helpful.  Sanding against the grain made the work go the fastest.  The biggest problem is the size and round shape made it hard to brace the wood against anything while I sanded.  

Learned from last year's Space Derby: When the kids made theirs we ended up taping a full sheet of 60 grit sandpaper to the workbench and the boys scraped the wood on the taped down sandpaper.  This was a very effective method for them to shape their rocket.  One of  my boys really sanded his down and it ended up being pretty fast because it was so light.


Here is it almost done.  I used some 150 grit paper to smooth it out.


Done with sanding.  What a mess!


Time to add some fins.  Fins are totally optional.  There are some pieces of card stock in the kit so I cut them to fin shape.  NOTE: You will notice in the later picture that the fins have changed shape.  This is because I discovered now that my rocket was sanded, the plastic bar that holds the rubber band would not clear my fins.  I had to modify the fins to make more clearance.


Cutting a notch for the fins.  I got smarter this time and used a putty knife instead of a utility knife.  The soft balsa wood is easy to cut and the putty knife made a better notch than the utility knife.  I will probably let the kids do these kind of cuts under close supervision now that I discovered that you don't need a real knife.


Here are the fins and hanger in the completed body.  I dry fit them (no glue) for now and will go back and glue them at the very end if I haven't messed anything up.  The astute reader will already know that I messed up the fins...  Good thing I didn't use glue yet!



Time to assemble the rocket motor.  Here is a detailed close-up of the hub and propeller assembly.  I have not yet bent the wire over the propeller.  Notice the red plastic tube that is slid over the hook.  This is critical!  If you forget this, your rubber bands will be cut by the thin wire hook.  I found it was easier to slide the red tube down the straight end of the wire to the hook.  I didn't cut my red tube any shorter.  The other important piece is the brass insert.  You can see it sticking out of the hub.  This will be seated in the hub once everything is assembled.  Without the brass insert the plastic propeller can bind against the plastic hub.  Notice also that the little round nose of the yellow propeller is pointed against the hub and the flat part is pointed out.


Preparing to assemble the motor.  Notice the nifty tool I made with a piece of wire.  You need something like this to fish the rubber bands through the body.  This picture shows 2 rubber bands. We will use 2 rubber bands for the space derby.  Bring your extra rubber bands in case one breaks during the race.


Here I am fishing the rubber bands through the body of the rocket.


Here is a detail of the assembled tail.  When the rubber band is wound, the plastic bar fits snugly in the notch.  My notch could have been a little deeper, but this one worked OK.  Notice the reshaped fins.

A cable tie is included in your kit.  This can be used to hold the plastic retainer to the rubber band when it's not wound.  Please try and assemble your rocket engine like the picture, otherwise you plastic retainer may fall out and get lost.  Do not over tighten the cable tie or it may cause the rubber band to break.  Once the cable tie is installed, you can cut off the excess length.


The finished product!  A little paint and this baby would make Buck Rogers proud!  You may notice there is a second cable tie in the picture below; you can ignore this as we are only using one this year.


Good luck on yours!  I have been told that the rubber bands need to be "broken in" before the race or they may snap.  Breaking in consists of first wind them 80 turns and let it unwind.  Then 100, then 120, etc.  Basically take it through a few test runs.

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