Klima EXA Build Thread pt1 - intro and parts

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May 9, 2011
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I've been asked to do a build thread on the EXA rocket by Klima. When Raketenmodellbau Klima GmbH in Emersacker was built in 2004-5, the 'cornerstone' of the structure was added - a 10m tall Red Rocket called the EXA Air Missile. Its upper third protrudes from the top of the structure while the middle third makes up the corner of the building and the rest is inside and serves as the focal point of their Sales Floor. This model is about a 1:16 (3/4" = 1' 0") scale model of that structure.

The box art shows the building, the model and the parts breakdown, along with a lot of text (in German, with which I am only vaguely familiar).
The box is deceptively thin...
but, upon opening, reveal a bounty of craftmanship.

The four centering rings and four fin cores are made out of 1/8" foamcore. The motormount tube is suitable for 24mm motors. it is 2-3/4" long and is consistent with the thick-walled Estes BT-50. A thinner Custom Rocketry-style motor hook is provided. I'll probably scrap it and use an Estes 24mm retainer or just friction-fit my motors. A motor block is also provided. I'll give that to the daughter and let her find something crafty to do with it.

The stuffing tube is 15-1/8" long with a 0.99"ID and a 1.02"OD. A heavy tube, 7-1/8" long with a 0.8"ID and 0.97"OD, serves as the shoulder for the nosecone.

The parachute is plastic (old school) Estes-Style 15" (flat to flat) hexagonal tie-it-yourself chute. I'll probably swap out a nylon chute, who knows...?

The selling point(s) of the kit are the two vacu-form sheets. One contains the two halves of the body and two halves of the nose cone. the other contains eight nicely rounded fin halves. These are a far cry from the vacu-formed components of the old Estes Space Shuttle stack, the Starship Enterprise, TIE Fighter or Klingon Battlecruiser. At 0.04" thick, I think these are as heavy as the Maxi-Brute Honest John fins from the late 70s.

The instructions consist of one sheet (in English, thankfully) and two sheets of b/w photos. Apogee, from whom my wife acquired the kit, classifies this as a Level 5. While I don't think it's as intense as the Estes Shuttle on any of the 3' Saturn kits, I'll still take my time on it - not only for the difficulty level but also because I have a number of other projects in various stages already.
Subscribed :pop:

I've never done any vac-form modeling. I'll be paying close attention when you start joining pieces.
I got one fin together before we left. I'm not too pleased with it, but everything is aligned and it will just be a bit more work on my part. Pics when i get back.
Each pair of fins was cut out and, as worked, cut into individual pieces.

Note: When cutting vacu-formed styrene, use a sharp knife (I use an X-Acto with No11 blades) and make several passes. DO NOT ATTEMPT to cut through in one slice. After about 3 light passes, you can flex the pieces back and forth until they snap clean.​

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The instructions call to use the old tube-type plastic cement. Perhaps they still use the same formula in Germany as we used to get in the 70s, but the last time I bought any here I found it to be as useless as a football bat. Instead, I opted to use Weldwood Contact Cement to bond the foamcore centers to the vacu-formed styrene. I know that's not a conventional choice of glue, but ordinary plastic cement won't bond to foamcore (and may even attack the foam component - I didn't test it) and Carpenter's glue won't adhere to the styrene. Epoxy is exothermic and would likely warp the styrene, so I didn't bother trying.

The contact cement is applied sparingly to both pieces and allowed to dry. Care was taken to avoid getting the contact cement on what will become the fin seam - that will be bonded with plastic cement later. When the contact cement is glossy (about 15 minute and not more than an hour) is it ready to be positioned. Contact cement isn't forgiving so you have to be spot on with your alignment. Fortunately, each fin has four alignment holes to ensure that you're spot on. Clamp it on the flash per the instructions and leave it to set up. Even though the bond is billed as instant, I gave each fin 2 hours.

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In the end, I don't think the foamcore made full contact with both fin pieces, but it makes enough to hold everything together.

Once set, you can trace the edges with a ballpoint pen. I don't remember why, but this instruction appeared in the Estes Starship Enterprise and Space Shuttle. Even though it's not stated in the instructions, it was clearly shown to have occurred on the kit's photo sheet. Score with the knife as cited above. By the third pass, the knife should start to penetrate. Flex the unneeded material until it snaps off.

Use plastic cement to seal the joins. I use Plastruct Plastic Weld for all styrene to styrene applications.

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There were a few instances where the foam was too close to the seam so the seam wouldn't easily close. I thinned some Squadron White Putty with the plastic cement and filled the seam. I don't think there's any difference between the White and Green putty Squadron produces (except, obviously, the color). Use it sparingly - too much will warp the styrene!

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Sand down all the seams, removing any flash that may have remained after the cut and snap action. Then set them aside until later.

Separate the two body halves from the nosecone halves. The latter will be put aside for later.

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Note: One half of the body and one half of the nosecone have lips to provide extra gluing surface. Do not remove them.​

Again, trace the edge with a ballpoint pen... 2017-01-04 17.36.42.jpg ...then score and flex... 2017-01-04 17.50.07.jpg ...until the halves come clean. 2017-01-04 17.53.04.jpg 2017-01-04 17.54.08.jpg

The ends will be addressed in Part 3 as I'm only allowed 10 pictures per post.
I discovered that I had bought one of these when reviewing unmade rockects over Christmas, so I will also be following the thread with interest.
The ends of the body shells were cut using the same method of mark, score x3, flex and break. A bit more care had to be taken to avoid tearing into the end cap. Both halves should have their edges sanded at least until the pen mark and little lip is gone.

Once accomplished, the aft and forward centering rings can be glued in.
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I used the same contact cement for this.

In the interim, the motor mount can be assembled. I just went stock, figuring that my AT 24/40 would support anything I needed beyond a D12. The motor block is glued into the end of what amounts to a BT-50. The hook butts against that and the whole thing is glued into a 1" stuffer tube.
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I wasn't exactly getting a warm fuzzy from the fit of the 2 tubes, so I started peeling off the outside of the motor tube.
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Once I was sure I'd be able to properly seat the motor tube without the Carpenter's Glue grabbing, I went for it.
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A hole is punched a few inches back from the end of the stuffer tube...
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and the kevlar line is tied so that it loops around the outside of the stuffer tube and enters through the hole. I tied a bowline and sealed the hole with a drop of Carpenter's Glue.
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The process is repeated on a heavy-walled tube which serves as the shoulder of the nose cone
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This side gets nylon line instead of kevlar.
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Wow. I guess I forgot about finishing this. Sorry about that.

The Centering Rings and their corresponding locations on the other half-shell got contact cement and then the body shell halves were put in place and cemented together with styrene cement.
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After a rough sanding (100 grit), thinned white putty was used to fill the seam.
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As the putty cured, the nosecone was started.
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Once the pieces were cut, the core Tube and Ring were fit and contact cemented.
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Similar to the body, the remainder of the Tube and Ring were contact cemented and the 2nd half-shell attached.
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Once the nosecone was rough-sanded and puttied, it was starting to look rockety.
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(I promise to not take so long on the next installment)


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I guess I didn't address cutting the fin slots before the body halves were attached. There's a V-shaped gully that catches the X-Acto blade well. a few passes in each direction and then cutting the V on each end creates a 4 flaps inside the body. These will cohere nicely with the styrene fins.
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At this point, we're attaching foam-core to (sanded) stuffing tube. A line of Carpenter's Glue was applied to the root of the fin
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The fin was worked into the slit with a slow see-saw motion to keep the body from collapsing in the process.
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Just before setting it all the way in place, Styrene Cement was applied to the joint all the way around plus the faces which will make contact upon completion. Another application of Styrene Cement was applied and allowed to wick into the joint.

This was repeated on the other 3 fins and then a line of CyanoAcrylic glue was run down the seam of the first and a spatula of MicroBalloons was splashed on top of that. When the CA cures, the excess MicroBalloons were tapped back into their container and the rest were dusted off. This was repeated on the other side and then again on the other 3 fins. These rough fillets were sanded with 100 grit to eliminate the irregularities due to the random nature of the CA/MicroBalloons.
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Squadron White Putty, thinned a little with Styrene Cement, was added over the rough fillets.
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A drop or two of Styrene Cement, smoothed with a fingertip, completes the fillets.
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Everything was sanded with 220 grit. Rustoleum gray primer was applied and, once dry, another round of 220 grit. A couple of noticeable pits were filed with thinned Squadron White Putty and resanded. Another coat of primer was followed with 320 grit sandpaper and, finally, a polishing with a ScotchBrite pad. Krylon Fusion "Sun-Dried Tomato" was chosen for the topcoat. I honestly don't know why I went with that color - I think I just went into the local hardware store and looked for an off-red...

The decal graphic was supposed to be available on the Klima website, but the link provided in the instructions was broken. Frank Baeyens, from the Facebook 'Model Rocketry Fanatics' Group, lives in Belgium and knows the owner of Klima. He contacted Klima for me and they sent him the graphic which he forwarded on to me
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I printed them up on clear decal paper and had my jar of MicroSet decal film shatter all over it. I salvaged several of the decals but the excess film made several too thick to be usable. My printer didn't make them opaque enough for my liking, so I went with what I had and may redo them all at some later date.

On one fin, there are noticeable dimples. These are drilled out with the tip of a #11 X-Acto knife or a heated pin. A screw eye goes into each one. I did a test fit, backed each out, added a dot of Carpenter's glue (since the screw eye goes into the foam-core fin-innard), and them screwed them back in. These serve as the launch lugs, so ensure that they are true to the roll axis.
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I've launched the Klima EXA twice now, both times on a D12-3. Both flights were 'squirrely' to about 300', implying the need for more nose weight and power. I will probably fly it next on an AT E18 or so.

Sorry for taking so long to finish this build write-up.
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Hey, thanks for finishing! Every time I read this thread I think about getting brave enough to try one of my vacuform kits.