Introduction: Klingon Battle Cruiser Sports Scale Rocket Workshop

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This project came to life in preparation for a meeting of the Belgian Voyage Club (the Belgian Star Trek fan club, BVC in short). On each of these meetings we do some fun activity. As a maker, obviously I wanted to get my fellow Trekkies into making too. I set out to organise a workshop, but for once not for kids as I’m used to, but for a bunch of people with a young spirit.

I went for building model rockets (a familiar subject for me, as a member of the VRO, The Flemish Rocket Organisation). The classic Klingon Battle Cruiser was the obvious choice. With its back swept wings, large nacelles, long “neck” and small bow section, it is probably the easiest ship in the Star Trek Universe to convert to a rocket for atmospheric flight.

Obviously there is the classic Estes Klingon Battle Cruiser kit, but that one requires some serious modelling skills. In this project I worked out a simplified, so called “sports scaled” version that can be built by anyone (with some guidance of course). In the workshop the concept proved to be quite robust. Several participants had little experience in model building, but the concept proved to be quite robust and with some guidance all were able to build a flying Battle Cruiser by themselves.

This Ible should guide you when building this Klingon Battle Cruiser yourself, providing you have some previous experience in rocket building or in building flying models in general. For the fans that do not have any model rocket experience, I recommend to get help from someone who does. My friends from the Belgian Voyage Club can testify it’s a great project to share between newbies and more experienced modellers. For those familiar with the skill levels in building model rockets: I would consider it a Level 3 on the Estes scale of 5. Obviously, it could also become the base of a more detailed flying scale model.

Along the instructions on the build in this Ible, I also explain the choices I made to simplify the model and the lessons learned from the workshop. The pictures shown in this Ible are from both a test build on a couple of dark autumn nights at home and from the workshop. You can see the happy builders and their launches in the last step.

Building and launching rockets can be dangerous, but there are plenty of sources where you can get the info on starting with that hobby safely, so I’m not going into the correct way to launch model rockets. See for example this Model Rocketry 101 Guide.

As English is not my native language, please feel free to point out any errors or unclear text.

If you like this Ible, please give it your vote in the contests.

Step 1: Materials and Tools

The materials for one model, including one rocket motor and igniter, cost under 10 EUR each.

Materials (first picture, from top to bottom, left to right):
A piece of 2mm thick balsa, 100 mm by 500 mm
A thin walled cardboard tube 20mm in diameter and 235 mm in length.
This is half the length of standard BT-20 model rocket body tube. I used a body tube from Opitec’s “Rocket model II”
A standard 19mm model rocket motors should fit in it.
20 cm of a balsa “stringer” with a triangular section 2x45°-90°, 10mm wide or smaller
Available at modelling shop for building flying model airplanes
A piece of 5mm thick balsa or light plywood, about 100mm by 40 mm
A wooden egg 40 by 60 mm
In case you do not have access to sanding equipment, a wooden half ball 50mm diameter is a better alternative, as explained in step 6 on the bow section.
A (wooden) button about 30mm diameter
A half ball, about 10mm diameter, in plastic or wood.
I happened to have plastic ones, clear and with a mirror base, a feature I used in a simple “window effect”.
A printout of the pattern/skin attached in the next step
Half the length of a standard 19mm diameter model rocket motor casing (A, B, or C type), emptied.
A screw hook or eye, maximum 13mm wide.
A streamer or a small parachute.About 50cm of Kevlar string as “shock cord”.
I like to use the “QUEST-way” to attach the shock cord to the rocket by tying it to the motor hook. This works fast and reliable, which is particularly important in workshops. I do not use elastic bands with streamers and small chutes. Obviously you can do it the classic “ESTES-way”.
A motor hook for standard 70mm long model rocket motors.
A launch lug, about 9 cm long.
I use a piece cut from a tube sold to hold up air inflated balloons. Do check if your glue works on them, as the plastics used are sometimes hard to glue (PE-like).

Tools, paint and adhesives (second picture, from top to bottom, left to right):
Sanding paper, medium grit
Gouache paint (school paint). I mixed the colour from blue, yellow, red and white
PVA glue
Cutter knife
Cutting surface (I worked on cardboard, for the workshop it was not possible to provide enough self-healing cutting mats)
Scotch tape
A metal ruler
Spray adhesive (contact glue)
A hacksaw
A (columnar) drill and a 2mm drill bit (not shown)
If you use the wooden egg, a belt sander comes in handy (not shown)
Something to protect your working surface from (spray) adhesive (like old newspapers, cardboard… , not shown)
For the workshop we also used non-stick baking paper to work on when using superglue (not shown)

Launching equipment (third picture, from top to bottom, left to right):
A launch pad (I used a tripod made from water pipes) with deflector plate
An ignition system
A model rocket motor: B6-2 (first flight) or C6-3 (I used German WECO motors)
An igniter (I used KLIMA igniters)
An igniter plug (an Estes one is shown)
A 3mm launch rod

Step 2: Making the Pattern

To simplify the build I made patterns that remain glued to the balsa, doubling as a detailed skin on the model.

I looked for orthographic views of D-class Klingon Battle Cruisers and found this nice one. It depicts a D4, which is supposed to be a version dating from the “Enterprise” era. You can find its story here.

I scaled the image in relation to the body tube and cut it into the parts I needed using GIMP. Of course you can use many other “image manipulation program”. The parts are simplified to 4-sided shapes with mostly straight sides, so they can easily be cut from the balsa with a knife and a little sanding. I didn’t bother to cut the images with exact trapezium shaped selections, but made a rough selection and made a “mask” with white rectangles (and arcs) around the edges after pasting them in a new image. I stretched the parts connecting the nacelles to the wings to compensate for the fact they are depicted at an angle.
On the main hull part and the bow section and added discreet lines where they are to be cut.

Finally I managed to arrange the parts onto one A4 page. Print it at a 100% size: check the main hull parts match in height with the width of the balsa (10cm or a couple of mm less).

Once the parts are cut from the paper, they are arranged on the balsa to check their fit. You could cut out the parts slightly to large as they can easily be cut to size together with the balsa, but keep that to a minimum, as there is not much room to spare. It is very important that all parts are oriented along the grain of the balsa wood in such a way that the grain always runs from the side the parts will be glued to the rocket and in parallel with the leading edge. The 2 mm balsa is quit fragile perpendicular to the grain.

For the 5mm Balsa used for the bow section that is less critical, but I still try to take in account how the parts are to be glued on the model.

To work fast I tried a spray adhesive (a kind of contact glue in a spray can). This proved to be very suitable. When spraying only the back of the paper, you can still reposition the pieces when sticking them to the wood and the bond is suitable but not very durable. When spraying both the back of the paper and the wood you need to position the parts “first time right” (it’s contact glue), but the bond is stronger. For the workshop we used the first method and added some glue to a corner here and there, where the paper came off.

If you prefer not to use spray adhesive (one reason could be the price of a can), you can use any other glue that allows sticking paper to wood, without it bubbling. However I doubt a Pritt style glue stick would give a strong enough bond. I would go for transparent contact glue, applied in a thin layer.

Step 3: Cutting the Parts

Once all parts are glued, cut them out using a cutter knife and a metal ruler, on a suitable surface protecting the table underneath. For the few rounded edges, you can look for utensils with the right curvature (like the small bowl I used for the bow section) or cut them out roughly and sand them down (like I did for the nacelles). For the workshop I cut out the bow section beforehand.

Step 4: Main Hull and Wings

To mount the motor hook, a small slit is made in the body tube, at about 65 mm from the aft end. The engine hook is taped in place as shown.

The halves of each Trapezium shaped part of the hull are taped together with a short piece of tape.
First the largest trapezium is “draped” over the body tube with its aft end (with the motor hook) sticking out a couple of mm. Supported with some scrap balsa it is fixed in place with some small drops of superglue. Once it stays in place a strong bond is made by adding a plenty of superglue at the inside.

For the next step it is best to put the motor in place, so you can apply force on the tube, without flattening it.

Once this has set the other trapezium is glued in place with some drops at the front corners and pressing the parts together, at the aft corners. Again more glue is added at the inside, letting it run along the body tube. Do not use to much glue to avoid it rung along the visible part of the body tube. I had this problem when building the example and it proved to leave traces, even after sanding and painting.

Stick the wings to the hull, with the paper facing up (i.e. the side of the largest trapezium). As the bond of the paper is not that strong yet, soak the seams well with superglue.

Step 5: Pylons and Nacelles

To mount the nacelles in the correct angle I went looking for an easy way. I needed pieces providing angle close to 135°. I came up with using balsa triangular profiles with 45° and 90° angles glued together as shown in the pictures. Pieces of about 2cm long just fit under the wings and pylons.

With these parts, first the “pylons” are attached to the nacelles. When assembling, keep example images at hand as a reference. Also check the nacelle-pylon assemblies are each other’s mirror image. As before, fix the parts in place with small drops of superglue. Only after checking the correct alignment (and adjusting where needed) soak the seams with superglue.

The same concept is used to connect the pylons to the wings. When building the prototype I noticed top edge of the pylon needed adjustment to fit with a correct alignment. I adjusted the patterns to take that in account.

Step 6: Bow Section

To make the bow section I used a beach wooden egg as available from crafts shops. The shape is a reasonable approximation to the shape needed and its weight brings the centre of gravity forward as needed.

First a flat face is sanded to the egg, till it is flush with the body tube as shown. For the workshop I did the sanding beforehand, with a belt sander. In case you do not have access to sanding equipment and do not want to do a lot of sanding by hand you can use a wooden half ball instead, as shown in the bottom pictures.

The wide end of the egg usually comes with a hole that cannot be used. I put thick balsa splinter in it and sanded it down, adding the round “deflector dish” shape at the same time.

A hole is drilled in the narrow end of the egg, to place a screw hook or eye. A columnar drill makes this easier. This to, I did in preparation for the workshop.

The half of the rocket motor casing is cleaned out on the inside by running a screwdriver or something similar inside. The shock cord is run through and tied to the screw hook or eye. Then the spent motor casing is put over the hook or eye and using the body tube to align correctly, it is fixed in the right position with some small drops of superglue. Then it is put vertical and a good amount of PVA glue is poured in. Let it set.

The other end of the shock cord is run through the body tube and tied to the motor hook. The streamer or chute is tied in place, close to bow section.

The flat section is made in two parts to keep the bow section in the right orientation. The front part is glued on the flat face of the “egg”. The back part is glued to the body tube. As you can see in the back part is a bit short. On the prototype I added a triangular piece of 5mm thick balsa, but for further builds I made the pattern a little longer.

Step 7: Strenghtening and Adding "impuls Engine" Fins

For a strong model give all joints a fillet of PVA glue, a good practice when building rockets. In the workshop, we didn’t have the time to do that and let the glue set. The models were strong enough to fly, but some needed repairing after a hard landing (we were using only streamers).

Inspired by the Classic Estes kit I added some “vertical” fins at the location of the impulse engines. This made sense to me as the model still misses some stabilisation in the “vertical” plane. However, instead of reproducing the engines and putting fins on top, I simplified the engines themselves into fins. I also oversized them somewhat and added another pair on the underside of the vessel.

As before, first fix them in place with small drops of superglue. When you are sure they are in the right position as shown in the picture, soak the seams with superglue.

Step 8: Finishing

Mix the colour matching the main shade of the paper coverings (a pale brown-green). For the workshop I painted the body tubes and “eggs” beforehand. That way the models already looked OK without further painting. As drying time was limited we also minimised further painting. If you have the time paint all blank wood and cardboard, including the edges. When using gouache (“school paint”) that is not to runny you can wipe of any spills on the paper when you’re quick. This makes it quite feasible to paint all edges too.

The superstructures on the bow section are simplified to a round, flat “button” and smaller half ball on top. These are glued together and painted before sticking in place. It is important that the superstructure is only glued to the front part. Check if bow section still slides off the body tube smoothly.

Step 9: Launching

When preparing for launch, do not forget to add the wadding to protect the streamer (or chute). Check if the centre of gravity is well in front of the main hull.

Having a rather small launch area available, I prefer to use a streamer, as I rather have some repairs to do after a hard landing in the grass, than a rocket floating off to far.

The weight without motor should be around 85 g.

I prefer to use a 1m long one, to allow this rather heavy rocket to get enough speed before leaving the launch rod. A simple 3mm diameter steel rod from a DIY shop works great.

I estimate the flight altitude to be about 35 m with a B6-2 and about 70 m with a C6-3.


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