Scratch Racer X Original Design / Scratch Built

Scratch - Racer X {Scratch}

Contributed by Steve Carr

Manufacturer: Scratch
(Contributed - by Steve Carr - 09/22/05) (Scratch) Racer X

Brief:
This is a paper rocket that I designed for the EMRR Challenge. I designed the rocket based on the old toilet paper roll rockets I used to build when I was a kid. My son did the artwork based on a Playstation game of his. It didn't look like the Mark V from Speed Racer, but it did remind me of his brother Racer X. Since I knew it would be light and I have a bunch of MicroMaxx motors, I thought it would work out OK on the little motors.

Construction:
Since it is a paper rocket only a few materials are required.

  • One 8.5"x11" sheet of 110# cardstock
  • 12" braided fishing line or small diameter Kevlar® thread
  • White glue, pencil, compass, large needle, and scissors
  • Finishing is part of the build process so add markers to your tools
  • A small amount of clay for nose weight

I had only built 1 paper rocket before this, so it has been a learning experience. They are not as easy as they look and take more time than one might think.

Start by cutting some strips of paper to the following dimensions:

  • One 3"x5 1/8" body tube
  • One 1/2"x5 1/8" nose cone base
  • One 1"x6" fins
  • One 1"x1" motor mount

Starting with the body tube, draw a line for the glue tab so you 3"x5" left. To lay out the fins, make a line from the bottom 1.5" and then up every 1.25". This will divide the 5" width into 4 parts for your 4 fins. Now make a small mark at the bottom of the of the strip 1/8" on both side of the fin layout line. These will be your fin spreads later. Now flip the strip over and make a line 1" up from the bottom. This will align your centering ring later. Now finish the outside of the BT with markers or hand it off to someone more artistic to do so. When that's done, roll over the edge of a table, put glue on the glue tab and hold a few minutes to set. Take the strip for the nose cone base and glue it together so it is small enough to fit in the BT.

For the fin strip, we need to layout the fins. On the bottom make a mark every 3/4" for the entire 6" length. At the top make one mark 3/4" from the edge then one every 1.5". Starting with the first mark draw a straight line to the corner then to the mark straight down and to the next 3/4" mark at the bottom. This will give you a 1"x 1.5" triangle.

Do the same with the rest of the marks until you have four. Cut them out and fold on the line down the center.

For the MMT, I wrapped the 1"x1" piece around a MMX motor and glued it then slid the motor out.

With the rest of the paper, you need to cut 3 circles:

  • One 2.5" diameter circle for the nose cone
  • Two 2" diameter circles for the centering rings

For the nose cone, cut it out and make 2 marks on the arc using a ruler 1 1/4" apart. Make a straight line to the center from each and cut out a wedge. Now do the artwork. When finished, pull the wedge closed and glue to form the cone. Now take the cone ring you glued earlier and glue it to the cone. This is best done by placing the cone upside down on a toilet paper roll laying the ring inside. Glue and center the ring and place a deck of cards on top for a little pressure till it dries.

(Scratch) Racer X For the centering ring you need to make smaller circles inside . One 1.5", one 3/8", and one 1/4". Make cuts from the outside to the 1.5" mark and fold them over. (See picture.) With the needle, poke holes to the inside of the 1/4" circle until it pops out . this little hole is for the motor mount tube. Now take a centering ring and slide it down (folded edges up) from the top to the bottom of the body tube and glue it so the ring is flush with the bottom of the rocket. Now take the MMT and slide it in the 1/4" hole in the centering ring. the rough sides of the hole make for good glue tabs. When dry, put some glue on a pencil or scrap of balsa and apply glue to the line on the inside of the BT you made earlier. Slide the other centering ring on the same way until the tops of the tabs meet the line. Your MMT should stick through about 1/8". Apply a little glue where the two parts meet.

You have 4 folded triangles for the fins. The point of the triangle should be glued to the layout line on the BT. The 2 tabs should touch the bottom of the rocket and be glued to the marks 1/8" to either side of the layout line at the very bottom.

Poke a hole in the bottom CR with the needle on the 3/8" circle for the launch rod. Then (this is the tough part) keeping the needle straight look through that hole and poke a hole on the 3/8" line of the other centering ring. Now place it on your MMX rod and run it down until it hits the nosecone and make a hole in the nose cone.

I poked a hole in the center of the cone pulled the braided fishing line through, knotted it, and glued the inside of the cone for a shock cord. I snipped the tag end off after the glue dried and I made a small Estes type with a scrap of paper to attach it to the body.

Flight:
I used a small amount of masking tape for a friction fit of the motor and no was wadding needed. You have to pay attention when putting it on the launch rod so all 3 holes line up and it slides freely.

Flight 1 was a surprise. It went about 15' straight up then did cartwheels at motor burnout. It needs nose weight!

Flight 2 was a lot better after a small amount of clay was put in the nose but it still needed a wee bit more nose weight.

Flights 3 and 4 made me laugh. They were perfect but only 20 to 25'. They were perfect for such a small and fat rocket.

Summary:
This was fun. The results though small were great.

One con to the whole thing is don't underestimate the ease of building a paper rocket. I did.

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