This is a modification of the free paper model from Currell of the Moon Rocket "Friede" featured in the Fritz Lang film Frau im Mond. I decided to build the rocket with an 18mm motor mount.
I built the paper rocket mostly stock, except for the fact that I cut out four centering rings out of foamboard to fit inside the rocket. The hole in the centering rings is to hold a BT-20 body tube for the motor mount. I made sure the motor mount tube was slightly longer than the body tube and that the motor block was in place. I installed the shock cord per my usual method: I like having a Kevlar® shock cord. I also used a shoulder piece from those Quest or Estes kits that give you the yellow fake motors to push in the motor blocks. I used one of these to fit inside the nose cone, centered with the help of foamboard.
The paper rocket instructions include forming the five cone parts to make the nose cone, rolling the body tube, and folding and shaping the four fins. The fins were difficult to make in that there are many folds as well as back-to-back gluing. When the fins are complete, there are little tabs that are used to glue the fin to the main body tube. This is accomplished by making a few small slits in the body tube and by fitting the fin tabs into those slots. I then reinforced the fins by adding some glue fillets. I initially thought the tabs would be insufficient but after three or four launches and streamer recovery, they have held up well.
What I did not add to the rocket was all the exhaust nozzle detail. An option for the kit includes a red circle that be glued to the bottom of the rocket over the bottom centering ring. All I had to do was cut a 19mm hole in the center for the motor mount to go through. In my Friede, I have part of the body tube sticking 3mm out the back of the rocket.
I filled the shoulder completely with clay but only after the shock cord was glued inside the nose cone. I added a streamer and a launch lug. The nose cone alone weighed 0.75oz.
What you will need to build the "Friede":
PROs: If you like Sci-Fi, then this rocket has to be on your build list. It is distinct and has a great history, too.
CONs: The fins are wobbly and deform easily due to the cardstock and the method of attaching them to the rocket. I think that if I were to make the rocket again, I would reinforce the fins more so that they kept a more rectangular shape. Also, I would make the inner body tube a BT-50 (and still keep a BT-20 for the motor mount) so that I would have more room for a parachute or streamer. It is currently a little crowded when trying to stuff the streamer into the body tube.
On my first flight, I had added clay and did a swing test. Everything seemed to check out fine. I used a B6-4 and the rocket cleared the launch rod, but then began turning horizontal, expending most of its energy flying parallel to the ground. The parachute ejected when the rocket was only 30 or 40 feet above ground. I originally had a parachute in the rocket but decided on my next flight to switch to a streamer.
The second flight I used a B6-4 again, but I ended up adding more nose weight (the nose cone should weigh about 3/4 ounce). The rocket had a great, stable flight and there was no wobble at all. Nice, high altitude.
On the third flight, I decided to put a C6-5 in the Friede. This proved to be a little too much thrust for the rocket. I think due to the air speed and the uneven fins, there was more significant wobble on the boost. Recovery was fine but I think I will stick to B6-4s for the Friede.
PROs: The looks, the history, and the fact that the Friede is cheap to make.
CONs: fin construction. The fins are flimsy and hard to attach to the rocket. I would definitely come up with a plan for stronger fins if I were to build another. Also, I would increase the inner body tube to a BT-50 so I would have more room for a streamer or parachute.