Sirius Rocketry Eradicator Build

Earlier in the year, David Miller of Sirius Rocketry contacted me about doing a build and review of his newest "Transition Series" kit, the Eradicator. Having built many of the Sirius kits (even doing my Level 1 cert with a Sirius Interrogator-G), I jumped at the chance.

A couple days later, this beauty arrived in the snail mail. Check out those parts!

The Sirius kits have excellent instruction manuals --- Parts List, illustrated steps with diagrams, and no ambiguity. There are 17 steps in the standard build. One of the things I found most helpful in the instructions are the points where alternate build strategies are mentioned. For example, the Eradicator has two ring fins at the base of the kit. As I browsed the instructions, I shuddered at the thought of masking that complex area at the base of the rocket in order to get the ring fins correctly painted. No sweat, though --- the instructions point out an alternate method and order of installation to permit assembly without the rings, painting them separately, then adding them after that step. While I most likely would have figured this out from scrutinizing the parts closely, the instructions made it easy to decide the best build path for my comfort level.

The cutting and gluing begins...

The centering rings, fins, etc. on the Eradicator are laser cut from a light ply, and have very little grain. A little work with the hobby knife and I freed them from their carrier sheet. In this, however, I made a mistake --- even though the wood has a minimal grain, I like my fins smooth, and thus use sanding sealer. On most kits, I can seal the wood after I have it glued up on the body tube. Doing so on the Eradicator is certainly possible (after all, I did it), but I *should have* sealed the wood while it was still on the original carrier sheet. There are a set of "vanes" (8 of them) which are quite small (at least for my big fingers), and made for a certain amount of "why did I do it this way?" emotion when I got around to finishing. So, my suggestion is --- if you're going to fill the wood, do it *before* you cut the pieces out. Not a drawback in the kit, by the way --- just a tip for anyone choosing to finish the wood later.

Motor mount --- The Eradicator has a 29mm motor tube long enough for even lengthy RMS casings. The first major glue up is the centering rings on the rear end of the motor mount tube.

One of the skills needed to build larger rockets is "through the wall" fin assembly. While many kits offer pre-cut body tubes, knowing how to cut your own fin slots is a useful skill, and the Eradicator requires the builder to develop and exercise this skill. A tube marking/cutting guide is wrapped around the base of the body tube and taped in place. Then, using a piece of angle iron for a guide, the 4 fin slots are cut out with a sharp hobby knife. When I first glanced at the instructions and saw I'd be cutting out my own slots, I thought, "Geez, too cheap to give me a slotted tube?", but, I have to admit, this portion of the build turned out to be my favorite part of the assembly. I took great care in doing the cuts, and it still took very little time to accomplish. And, in the end, it reinforced a skill I had not practiced in awhile --- and reminded me that I enjoy being a BUILDER, and not just an ASSEMBLER.

Now that the fin slots are cut, it was time to assemble the motor mount tube inside the main body tube. For a bird this big, epoxy is our friend. Additional centering rings are applied to the top of the motor mount tube, to act as mounting points for the ring of vanes and the upper body tube.

Now we epoxy the fins "through the wall" onto both the internal motor mount tube AND the outside body tube. I was very glad I'd taken my time and done precise cuts for the tube slots, as everything fit together perfectly, with no crushing of the body tube around the fin joints. After the epoxy dried, I applied white glue fillets at the fin/body tube joins for extra strength, per the instructions.

At this point, we *could* install the ring fins, but I opted to leave them off so as not to complicate my future painting efforts. Instead, I skipped step #11 on the instructions and moved on to installation of the Kevlar shock cord mount and elastic shock cord. This was followed by gluing on the top body tube, then installation of those vanes mentioned earlier. In the same way as the vanes "dress up" the rear of the Mars Snooper, I think these vanes add a nice touch to the Eradicator's body tube interface.

This completed the major assembly of the Eradicator, and so it was on to finishing. Here, I ran into my second "mistake"...filling the spirals on the body tubes. I've been experimenting with different fillers on my last couple models, and decided to try out Bondo red Spot Putty. While it was a snap to fill the top tube spirals, the rear tube was a pain in the...posterior. All those fins and vanes in the way! I should have filled the tube spirals before I even began, THEN assembled the fins and vanes onto the tubes. Oh, well. The tubes still turned out nicely; it just took a longer time and the lower tube wasn't quite as perfect as I like. After filling the spirals, I shot the entire bird with Rustoleum grey primer.

While the main model gets painted Rustoleum gloss white, the nose cone and ring fins are to be painted grey. I wanted to get the outside AND inside of the ring fins grey, and used a trick for painting ring fins I picked up awhile back --- I tacked the tube fins to a piece of lightweight stiff wire (the kind of wire you can pick up at Michael's and is used for floral arrangements). This provides a "holder" in which you can spray the inside and outside of the fins. Both the nose cone and the ring fins received a couple coats of Rustoleum gloss grey.

Once the rings dried, I removed them from the wire and glued the rear one into place in the pre-slotted fins. The front one gets split, then glued in place on the front set of slots in the fins. The seam in the ring fin is hidden by joining the two ring fin ends at a fin joint. Clever idea, there, David!

Next to last step --- the Eradicator offers two options for launch guidance; 1/4" launch lugs or rail buttons. At this size of rocket, I feel that launch lugs detract from the "look" of the rocket, so I opted for rail buttons (incidentally, BOTH lugs AND rail buttons can be installed; they are offset 45 degrees along the body of the rocket, so you can have maximum flexibility in launch hardware). A little drilling and epoxy, and voila! Ready for the final finishing step...

Finally, time for the decals. The Eradicator comes with two big decal sheets, and you use all of them. Several are "wrap around the body" decals, so it's necessary to be very careful with alignment so that the ends join perfectly as they meet. The use of the decals give this bird a very "military missile" feel.

One other finishing tip: Although the instructions point to "masking" an area between two sets of fins and painting the area black, I opted to skip the pain of this process and substitute the use of a couple pieces of black Monokote...ever so much easier to position and looks much better than my painting skills would permit.

In summary, I would say that the Eradicator was a straightforward build, with enough challenges to make it interesting (i.e. fin slot cutting, ring fin painting, impressive decals), but with parts that went together quickly and accurately. The fit and finish on the kit were (like every other Sirius kit I've built) top-notch. It's an eye-catching bird, and I can't wait to put her up this summer, first on an F50-6T, then later on a G40 or G64. There's plenty of room in the upper tube for dog barf, the 30" chute, and my Altimeter 2 & squealer, so I expect a great set of flights. I'll be sure to stop back and post pics of her boosts.

If I had not been taking my time to document the build with photos (not to mention wanting to double- and triple-check my work, since I knew I'd be writing a review), I believe I could have built the Eradicator over a weekend or two. As it was, I spent about 24 hours total on it, and the results, I believe, speak for themselves.

Looking forward to the next rocket to emerge from Sirius Rocketry's shipyards, David. Hope it's soon!

Beautiful, absolutely beautiful ,nice work and a great looking kit !

I know what`s on my list to order from David.

And by the way ,David is one heck of a gentleman and great vendor !


Paul t

sodmeister said:

Beautiful, absolutely beautiful ,nice work and a great looking kit !

I know what`s on my list to order from David.

And by the way ,David is one heck of a gentleman and great vendor !


Paul t

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Totally agree! And beautuful bird and construction!

Beautiful job on the build!!