Klima EXA Build Thread

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DES

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I received one of the Klima EXA kits for Christmas. This is a neat looking rocket, reminiscent of classic sci-fi.

This will be a little bit of a build thread, but fair warning -- by necessity, it is also a glue thread…

Much of the rocket construction involves gluing various vacuum formed plastic parts to each other, and to foam core and cardboard. I welcome input from others who have already tackled and figured this out.

DSCN3545.JPGDSCN3546.JPG


Problem #1 - the rocket kit is manufactured in Germany, and so most of the recommended adhesives are also German. That’s fine, ought to be able to source equivalents in the US, right?

So, the very first step involves gluing foam core fillers between vacuum formed skins to form the fins. The fins are pretty thick, not quite 1/2 inch. Everything is nicely molded and pre-cut and fits together very well. The foamcore appears to be some sort of urethane foam with paper skins. It is not styrene as Testor’s cement does not melt it. The vacuum formed skins - initially, I assumed those there ABS or styrene (Mistake #1...) as parts of the instructions say to glue them with UHU Hart, which is basically Testor’s orange tube model cement.

Instructions recommend gluing the foam core to the plastic skins with PU Foam Glue “Beli-Zeli”. Not available here in the US, and I didn't see the need to order it from the UK, so a google search later, some RC model airplane forums suggested this was similar to Gorilla urethane glue, and suggested success with the clear, low foam version.

So I cleaned the plastic with alcohol, let dry, and proceeded to glue up two of the fins with Gorilla clear urethane, clamped everything up with clothes pins, and let cure for a couple of days. Unclamp, trim out the fins. Next step is to “seal the seams with “UHU Hart” (plastic model cement). Seemed plausible, but I noticed that parts of the fin edges seemed loose and unsupported. I had used plenty of glue, so why is this plastic loose? A little bit of prodding, and it was clear the plastic had not adhered to the glue or foamcore. The plastic didn’t adhere at all, it was just being held together by surface tension.

Before proceeding further (and before doing the other two fins) I decided a bit of testing was in order. I took some of the scrap plastic, glued two pieces together with the Gorilla glue, and two with the Testors.

Long story short - absolutely zero adhesion for either the Gorilla glue, or the Testors cement. The gorilla glue peeled right off, the Testors had almost zero burn in, and popped right apart.


Plastic Skins and foamcore insert
Plastic skins and foam core insert.

Problem #2 --- So this isn’t ABS or Styrene, just how the heck are you supposed to glue these things together? This is starting to behave like HDPE polyethylene milk jug plastic. How do you assemble a model out of un-gluable plastic?

More testing was in order. I have just about every adhesive known to man (and a few more) in my glue cabinet. I collected more plastic scraps and half a dozen of the most promising adhesives for an ad-hoc test. Everything was cleaned with alcohol, but I did not roughen or sand, as most of the joints on the model are thin edges you cannot really roughen. Here’s the results –
  • Gorilla Glue clear urethane - zero adhesion; cured adhesive film peels completely off
  • Testor Orange tube plastic cement - almost no burn in, no welding, cured film brittle and shatters.
  • Loctite “Plastic Epoxy” - this is an acrylic with some solvents, should bite the plastic. Poor adhesion. Better than the Gorilla glue, but almost no peel resistance.
  • JB Weld Structural Plastic glue - this is a two-part urethane, specifically labeled for “most plastics”. Fair adhesion, but some peel resistance. Didn’t pull apart in sheer. Managed to tear the plastic a bit while it was peeling apart. Not great, but it did glue the plastic together.
  • DAP CA with plastic primer. The primer is heptane, the CA is “toughened gel”. Scrubbed both pieces of plastic with the primer, let dry, then applied the CA and clamped together. Success! Good bond, good peel, destroyed the plastic trying to pull the pieces apart.

DSCN3550.JPGDSCN3551.JPG


Gluing the foamcore inserted between the plastic skins requires a pretty liberal glue bead to fill the gaps, so going forward, I will probably use the JB Weld plastic glue to glue in the inserts, and, then “seal the seams” with the CA and Primer. I’m going to need to order a bottle of primer.

This approach will work, but is not an ideal solution and starting to get a bit exotic. More work than expected for a consumer kit.

Anyone have any thoughts on how you are supposed to glue these things together?
 
Tim Van Milligan says he achieved good results with Rocketpoxy.
Exa Rocket From Klima (apogeerockets.com)
I suppose any thick paste epoxy would also work.
I have some RocketPoxy, I'll mix up a dab and test it out.

I'm also looking to see if I can find the Beacon Foam Tac - that looks like it has promise. Its flammable, so Amazon won't ship to Alaska. But I might be able to find it in town or from another vendor.
 
Cripes. Kit should have it's own included adhesives with it's super secret plastic formula. It seems a far cry from their cluster engine Andromeda kit. You go from level one to master in one kit. Those germans want you to be smart at "Mach" speed. I have the Exa in a shopping cart. I might remove that, because I'm scared.

Curious to see how it balances and weighs out,,once glued up, with the proverbial dab of everything on the shelf.
 
If there is a lot of gap space between the foam cores and the fin shell, then the Rocketpoxy should help.

The Beacon Foam-Tac stays flexible even after it fully cures. As you could guess it does not sand, any squeezed out would need to be wiped off or trimmed with a hobby knife.

That said, I just used it again for the wraps on an Apogee Saturn V, and for styrene wraps it works great. Barely any odor, no messy spray, some forgiveness to precisely position the wrap.

I'm surprised it will not ship to Alaska, I guess because it is flammable and has to be flown-in?
 
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