Accur8 Indigo Ragnarok Orbital Interceptor Build Thread

Discussion in 'Low Power Rocketry (LPR)' started by neil_w, Jan 2, 2018.

  1. Jan 2, 2018 #1

    neil_w

    neil_w

    neil_w

    Slipshod Perfectionist TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    3,904
    Likes Received:
    33
    Location:
    Northern NJ
    Greetings. This is a build of the Accur8 (aka John Pursley) Indigo Ragnarok Orbital Interceptor. John calls it a "short kit" which basically means it's a kitbash, in this case of the Estes Cosmic Interceptor. Here is what the finished model is supposed to look like:
    [​IMG]

    I say "supposed to" because I can already tell you mine ain't gonna be perfect. But it'll still be cool.

    The design is originally inspired by this old plastic kit from 1959:
    [​IMG]

    That kit was updated and reissued in 1976 as the Ragnarok Orbital Interceptor:
    [​IMG]

    I've been sitting on this build for quite a while, waiting until I had gotten far enough into it to ensure that the build thread wouldn't take forever. I think I've waited long enough.

    Next up: background

    ragnarok.png
     
    Last edited: Jan 24, 2018
  2. Jan 2, 2018 #2

    neil_w

    neil_w

    neil_w

    Slipshod Perfectionist TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    3,904
    Likes Received:
    33
    Location:
    Northern NJ
    Here is some background on this build. Feel free to skip this crap if you want.

    Back when I was first thinking about becoming a BAR, I ran across some pictures of the Accur8 Twilight Interceptor, and was sort of dumbfounded that such a thing was possible. I vowed that at some point I would have to try doing a skinned rocket. My ideal opportunity came when the Trajector and the Cosmic Interceptor were both put on clearance from Estes, *and* John had a 2 for 1 skin sale. So I figured it was time. I hemmed and hawed a bit (those who have read any of my threads will no doubt be shocked to hear that) but finally pulled the trigger and ordered the skins... and then both the Trajector and the Cosmic Interceptor went out of stock at Estes before I ordered them.

    Fortunately, the Trajector returned, but the Cosmic Interceptor did not. I wanted to combine the order, but didn't want to wait and then have the Trajector go away permanently (as it turned out I needn't have worried, but I didn't know this at the time). So eventually I just ordered the Trajector and assorted other things to get my free shipping, and then John was kind enough to sell me a spare Cosmic Interceptor kit he had at a very reasonable price. So I had my kits and my skins ordered. This was January of 2017.

    The plan was to use the Trajector, being a simple 3FNC, as a practice run for the Ragnarok (which is what i'll call it from now on, because the whole name is too much to type every time). I would learn how to work with the skins so I'd be, if not an expert, at least *competent* when building the Ragnarok.

    Oh, one other thing: I thought the Accur8 builds would be great for the winter because skins! No paint! Seemed like a perfect setup. I was psyched.
     
  3. Jan 2, 2018 #3

    neil_w

    neil_w

    neil_w

    Slipshod Perfectionist TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    3,904
    Likes Received:
    33
    Location:
    Northern NJ
    When my skins and kits arrived I was excited to check it all out. The Ragnarok package consisted of 2 sheets of instructions, 2 sheets of fin and other templates, and 6 or 7 sheets of skins. The skin prints look to be very high quality. I am very annoyed that it didn't occur to me to make high-quality scans of the skin sheets before I attacked them; coulda made a killer OR model out of this. Oh well.

    Here's what a typical sheet looks like (click for larger):
    IMG_6437.jpg

    In addition to the assorted skin pieces on this sheet, there are some instructions squirreled away into the open spaces. This is the main thing I'd change about the way these skins are designed: the same instructions appear in multiple different places, somewhat randomly scattered among the various sheets. For this kit, as mentioned, there are two separate sheets of instructions as well. These two sheets have much of the same info twice, except one sheet has smaller print and therefore room for a couple of very useful figures. All well and good except for one thing: the instructions are not exactly the same in all places. In most cases the differences are minor or even insignificant, but it's disconcerting not knowing which instructions to treat as canonical. I guess the bottom line is to read *all* the instructions and sort out your various questions before you start.

    As for the how the build works, I rather quickly noticed that one of my base assumptions about these skins was exceedingly wrong: this is not a no-paint build, *at all*. In fact there's lots of painting and finishing to be done. The difference from normal is that nearly all of the finishing is done before assembly. So, after being bummed about it for a while, I decided that I would just spend the spring and summer doing very leisurely fabrication and finishing of all the various parts, and then come wintertime I'd be ready to skin and assemble indoors.

    Next post starts the actual build.
     
    Last edited: Jan 3, 2018
  4. Jan 2, 2018 #4

    jpoehlman

    jpoehlman

    jpoehlman

    Well-Known Member

    Joined:
    Sep 29, 2014
    Messages:
    193
    Likes Received:
    0
    Subscribed! I’ve built one of these as a practice run for a pair of Interceptors “short kits” skins customized for my boys. The interceptors have yet to be build, but the Ragnarok turned out pretty well. It’s had one flight. Unfortunately, the chute failed to open as it remained wrapped around in the nonexistent protector.... my error in the setup. It landed with the vertical stabilizer down. It snapped off cleanly in 2 pieces. I think it can be re-attached with some CA.

    Good luck on your build. I found it to be pretty fun.

    I have to also credit John for his great support when I did have a question or two.


    Sent from my iPhone using Rocketry Forum
     
  5. Jan 2, 2018 #5

    neil_w

    neil_w

    neil_w

    Slipshod Perfectionist TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    3,904
    Likes Received:
    33
    Location:
    Northern NJ
    Excellent! As we move along I'll be interested to hear how your experience compared to mine.
    Absolutely true, he is very generous with his support via email. However, I do think he would do his customers *and* himself a service by putting most of that information up in a FAQ on his website. I have no doubt that most or all of the questions I've sent him are the same ones he's answered over and over.
     
  6. Jan 5, 2018 #6

    neil_w

    neil_w

    neil_w

    Slipshod Perfectionist TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    3,904
    Likes Received:
    33
    Location:
    Northern NJ
    Step 1: protect the skins.

    A light clearcoat just to keep them safe during handling. I used Krylon UV resistant gloss; afterwards, John told me that stuff has fairly hot solvents and could deform the skin vinyl. Fortunately I applied it light enough that I did not have a problem. While applying Future to my Trajector, though, I did experience a bit of running of the ink in a few spots, so it's possible I went a little *too* light....

    Step 2: cut some wood.
    John said you could use either 1/8" basswood or hard balsa for the fins. I went with basswood, thinking that it would be easier to seal and finish, what with its tighter grain. Also John definitely seemed to prefer it, so I went with it. The fins are laid out on a single 4"x36" sheet that is sort of a masterpiece of jigsaw-puzzling:
    IMG_6446.jpg

    Apparently my rendition was somewhat less than masterful, though, because I ran out of room for the final fin:
    IMG_6389.jpg

    So I got another sheet, and now I have plenty of spare 1/8" basswood. I would have needed the second sheet anyway, because one of the fins was not up to par and needed to be recut.

    The horizontal stabilizer assembly is nifty, consisting of two fins and two shaped pieces of wood dowel:
    IMG_6390.jpg

    The wings, too large for the 4" sheet of basswood, needed to be assembled from two parts each:
    IMG_6396.jpg

    I did a *lot* of careful sanding with the sandpaper on the bench to make sure the whole root edge of each wing was as flat as even as I could make it. End result was pretty good.

    I went with John's recommendation of rounded leading edges and tapered trailing edges. I learned two things about basswood:
    1) tapered edges are no problem, the pointed edges are not particularly delicate. I would have destroyed them many times over if they were balsa.
    2) basswood takes about 20 times more sanding than balsa to shape it. I was somewhat surprised how long it took me to get all the pieces sanded to shape, but I was in no hurry so I didn't worry about it.

    Here's the finished set of fins, unfinished:
    IMG_5972.jpg

    So far so good.
     
  7. Jan 5, 2018 #7

    les

    les

    les

    Forum Supporter TRF Supporter

    Joined:
    Jan 20, 2009
    Messages:
    2,175
    Likes Received:
    4
    Looking good!
     
  8. Jan 6, 2018 #8

    neil_w

    neil_w

    neil_w

    Slipshod Perfectionist TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    3,904
    Likes Received:
    33
    Location:
    Northern NJ
    All the wood fin pieces needed to be filled (sort of) and painted black, for two reasons:
    1) The skins need a good smooth surface to adhere to, and
    2) some edges would be exposed when all finished, and those should be black (actually they'd be better off in a dark blue to match the skins, but no matter)

    Normally I'd paper my fins and apply a coat of filler/primer. However it seemed crazy to paper a bunch of wood that would subsequently be covered by skins. John recommends using Rusto 2x clear gloss as a filler, but only if you sand it within a couple of hours of laying it down, before it becomes rock hard. I couldn't guarantee adhering to that timing, so decided to just try a very heavy (!) coat of Rusto filler/primer.

    I learned a couple of things. First, no matter how heavy you lay it down, it still won't perfectly fill the grain. There's a reason why Micromeister recommends many coats of primer for his "primer-only" fill technique. So I still had a bit of grain showing through in some areas. I decide that really isn't a problem since, again, it'll all be covered by skins. Didn't need to be perfect.

    The second thing I learned is that a very heavy coat of Rusto filler/primer is incredibly hard to sand. I've never had much problem with it before, but then I had never laid it on thick like that before. Very tedious.

    When finished, the fins looked... OK, I guess, but certainly far less perfectly filled than I'm accustomed to. Again, I decided it was OK.

    Sorry I somehow failed to take any pics of the primer stage.

    Then onto painting. The regular fins got taped on their edges, while the horizontal stabilizer was taped to a wood square dowel on the protected strip where the vertical stabs would be attached. I thought I was doing a really nice clean job until I noticed frighteningly large drips and runs on the wings. Apparently i held the can too close or moved too slowly. Think I would have mastered that by now. :facepalm:
    IMG_6200.jpg (Having trouble uploading the wing picture, will try again later.)

    I also realized that the primer sanding process had removed most of the primer from the edges, and so the paint was quite rough there... and those were the bits that might be exposed.

    First I wet-sanded down all the parts to smooth out the various bumps as well as I could. Then I hand-brushed some Testor's gloss black along all the edges. The edges looked OK when finished, the rest looked like a disaster though (click for giant hideousness):
    IMG_6444.jpg

    I continued to console myself that the ugliness would be hidden under the skins and wouldn't matter; the surface was still more than smooth enough for the vinyl to stick. I still was unsatisfied, though, so I thought I'd take a crack at polishing with auto polishing compound. I bought some Turtle Wax Polishing Compound (maybe not the best choice, but it was a relatively cheap experiment) and went at it. The results were... well, better than nothing but far from what I was hoping. Here's a before (left) and after (right) on one of the fins, it's very hard to tell what's going on in the pic but the short answer is "slightly better in the after".
    IMG_6393.jpg IMG_6394.jpg

    Eventually I just called it done, despite the fact that I had a bunch of fins that at best could be called "blackish" at this point. But I thought the edges seemed "OK", and the other bits would be hidden. Certainly not the high quality I had been hoping for when I started though.

    At this point I adopted the attitude that no matter how crappy a job I do on this, it'll still be an incredibly cool model. That's my story and I'm sticking to it.

    The best thing was: this marked completion of all the stuff I had to get done in the good weather. The rest of the build would be an indoor affair.
     
  9. Jan 6, 2018 #9

    goose_in_co

    goose_in_co

    goose_in_co

    Well-Known Member

    Joined:
    Jan 18, 2009
    Messages:
    331
    Likes Received:
    0
    Just curious, What parts of the Estes Cosmic Interceptor kit are used for this kitbash?
    I can see the nose cone, main body tube, and motor mount, but what else? If I could get a hold of a nose cone, could the rest of the parts come from my stash?
     
  10. Jan 6, 2018 #10

    neil_w

    neil_w

    neil_w

    Slipshod Perfectionist TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    3,904
    Likes Received:
    33
    Location:
    Northern NJ
    It’s 27” of 2” BT (Cosmic Interceptor does this with 2 pieces coupled together), on additional piece of BT (about 7” long) for the scoop, the nose cone and the motor mount. And the launch lug and parachute etc.

    I *think* that’s it.

    [edit] Nope, two more things: the cardstock vanes that go at the back of the motor mount, and the yellow spacer tube used in building the motor mount. Both could probably be improvised with other stuff.
     
    Last edited: Jan 7, 2018
  11. Jan 7, 2018 #11

    neil_w

    neil_w

    neil_w

    Slipshod Perfectionist TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    3,904
    Likes Received:
    33
    Location:
    Northern NJ
    What I learned building my Trajector was that skinning the body tube is the most instantly satisfying step of the whole build. For those who haven't worked with Accur8 skins before, here's how tube skinning works. I'm following John's instructions pretty closely here; the method is pretty highly refined and works extremely well.

    After the skin is cut out, a narrow strip of the backing material is cut off along the edge that will be adhered first (this is marked on the skin sheets)...
    IMG_6378.jpg

    ... and then put back where it came from.
    IMG_6379.jpg

    The wrap is then held around the tube in position. This is the single hardest part (such as it is): getting the skin into the exact correct position and holding it there. Note that this method would need modification if we were wrapping a much larger tube, unless you had huge Dr. J hands. For a 2" tube it works fine.
    IMG_6362.jpg

    Next, lighten up on the edge that has the cut backing strip, and remove just that piece of backing.
    IMG_6380.jpg

    Stick the edge of the skin down onto the body tube, taking cure during the whole process to keep the skin in that correct position you so carefully found earlier.
    IMG_6381.jpg

    Now the position of the skin is basically set, all that remains is to stick it on. Lift the edge of the remaining piece of backing and hook it around the body tube. Hard to describe, hopefully the picture shows it:
    IMG_6366.jpg

    Then simply work your hands around the wrap, starting from the part that is already stuck down. The backing will push away effortlessly as you go, until the final edge of the wrap comes back to join the original. John provides a narrow strip of overlap, which is good because the skin sticks best to itself (more on this later), and therefore this gives a nice secure edge that won't lift. It also ensures that there's no unsightly gap between the two edges.

    Final alignment of the edges reveals how accurately you positioned the skin in the 3rd step. I give myself A- here. I did slightly better on the Trajector, but this is fine.
    IMG_6383.jpg

    Three body skin pieces complete the job for this rocket. Here's the finished result. There's still lots more work to do on this, but this feels like a nice accomplishment. The whole process literally only takes a few minutes.
    IMG_6369.jpg
     
  12. Jan 7, 2018 #12

    les

    les

    les

    Forum Supporter TRF Supporter

    Joined:
    Jan 20, 2009
    Messages:
    2,175
    Likes Received:
    4
    Agreed - the simplest part, but you get the most covered at once and really start to appreciate the beauty of the wrap.
     
  13. Jan 8, 2018 #13

    Saluki

    Saluki

    Saluki

    Well-Known Member

    Joined:
    Jan 18, 2009
    Messages:
    235
    Likes Received:
    0
    Good build thread. I have wanted to see a build thread on this rocket since I saw these skins on Johns site.
    By the way, John has his skins on discount at his site if anyone is interested.
     
  14. Jan 9, 2018 #14

    neil_w

    neil_w

    neil_w

    Slipshod Perfectionist TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    3,904
    Likes Received:
    33
    Location:
    Northern NJ
    The rear end of the BT needs a "sausage cut". The skin shows where to make the cut:
    IMG_6369.jpg

    I was a little nervous about needing to freehand a bit cut like this while the skins were on... my blade tends to wander off sometimes. I tried to do it as carefully as I could, taking about 4 passes to get through the tube and skin. I did OK, but the edge was still pretty rough, and a bit of skin hung out over the edge. Dunno if you can see it in this picture, but it was the best I could do (click for the larger version to have any chance of seeing anything here; that applies to most of the following pictures).
    IMG_6384.jpg

    Next I had to clean it up. I CA'ed around the edge, and also along inside near the edge. In addition to hardening it up for sanding, it also served to seal the edge of the skin down:
    IMG_6385.jpg

    Then I sanded as carefully as I could. Part of what I had to do was sand off the bit of the skin flapping over the edges (we're talking about 1 mm here), so I had to sand with a block on the outside. The end result was good, but as expected I ended up with a considerable bit of white skin-edge showing:
    IMG_6374.jpg

    I am very happy that the "background" color of this build is black. I ran a black Sharpie carefully around the edge, eliminating all the bits of white at the edge. Only a couple of times did I drift onto the exterior skin; like I said earlier, this build is destined to be "good enough", and not nearly perfect.
    IMG_6386.jpg

    Here's a side view of the edge. Compare to the 2nd pic near the top and you'll see (?) the difference. The end result is not perfectly smooth but it's absolutely good enough.
    IMG_6387.jpg

    On the forward end of the tube, I noticed that the skin did not come all the way to the edge:
    IMG_6377.jpg

    I'm not sure why that came out like that, but either way I'll fix it later, either by trimming off that bit of BT, or by applying a bit of extra skin (not sure if I'll have a piece of the appropriate size yet). Or I could just Sharpie it. :)

    That mostly takes care of the BT. But there's still a bit more to come...
     
  15. Jan 10, 2018 #15

    neil_w

    neil_w

    neil_w

    Slipshod Perfectionist TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    3,904
    Likes Received:
    33
    Location:
    Northern NJ
    Note that I'm documenting the build in a different order than I've actually done it, to make it a bit more organized.

    So, the body tube is not quite finished. First, we must remove all the bits of vinyl where stuff will be glued to the body. I did an *extremely* careful job on this and was very happy with my results. Here's the spot where the vertical stabilizer gets mounted after I removed the strip:
    IMG_6431.jpg

    The next day I went to check on things and was greeted by this:
    IMG_6451.jpg

    Basically, *every* edge was lifting where I had cut it. This has become a theme of the build for me: this particular batch of vinyl is insufficiently sticky and/or flexible, and virtually every edge that is attempting to adhere to a curved surface will lift up. The exceptions are the places where the skin adheres to itself (such as where the body wraps overlap at the edges.) John told me back when I bought this that he has experimented with different vinyls and briefly used a version that had a less aggressive adhesive. I believe that my vinyl is from this batch, although that's up for some debate based on recent discussions with John. In any case I would suspect that newly issued skins will not have this problem, but that doesn't help me right now.

    I had already been dealing with this issue (a lot) when skinning the fins, with varying success (like I said, I'm posting in a different order than I'm building), but I have to admit feeling a bit of despair when seeing the body tube pieces lifting up like that. Although it is possible to glue the edges down (I'll cover this later), it is hard to do without making a mess, and I do not enjoy it. And so I took a deep breath, stepped away for a bit, and thought about it. Ultimately I realized that I *should* be able to deal with this in a reasonable way when gluing on the fins. So I decided not to do anything about these at the moment, despite how ugly they look right now.

    Lastly, the inside of the sausage cut is painted black. Instead of my usual Testor's enamel, I tried some Tamiya gloss black acrylic. Actually I should probably have used flat for this but no biggie. I really like the Tamiya paint; it dries fast and levels extremely well. Although it stinks while painting and drying, the odor dissipates much quicker than the Testor's enamel and since it cleans up with water there's no added stink of the thinner. With no primer, two brushed-on coats provided excellent coverage. Thumbs up.
    IMG_6462.jpg

    After the motor mount is installed there will be a bit more work to do here, but it'll be a while before I get to that.

    Next up: a few days in Florida, and then I'll start in on the fins when I return.
     
    Last edited: Jan 10, 2018
  16. Jan 10, 2018 #16

    barn

    barn

    barn

    BAR none

    Joined:
    Feb 25, 2009
    Messages:
    24
    Likes Received:
    0
    Enjoying this build thread. I've been curious about the Accur8 skins. Thanks for posting.
     
  17. Jan 10, 2018 #17

    burkefj

    burkefj

    burkefj

    Well-Known Member

    Joined:
    Jan 27, 2009
    Messages:
    2,440
    Likes Received:
    5
    That's a bummer, have you contacted John, he might replace the skins rather than try to work with bad adhesive, I think you may have problems on the cone if the stickiness is poor....

    Frank
     
  18. Jan 10, 2018 #18

    neil_w

    neil_w

    neil_w

    Slipshod Perfectionist TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    3,904
    Likes Received:
    33
    Location:
    Northern NJ
    I have but I should probably contact him again.

    You're right that the nose cone is going to be an issue. I had problems with edges lifting on the nose cone on my Trajector but was able to work through various fixes and came out with a good result, but for various reasons I might not have as good luck with it here. In any case that is why I'm leaving the nose cone until the end.

    Let me emphasize that the build continues to move forward despite the problems (it's about 3/4 built at this point) and it looks hella cool on my bench. :)
     
  19. Jan 10, 2018 #19

    neil_w

    neil_w

    neil_w

    Slipshod Perfectionist TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    3,904
    Likes Received:
    33
    Location:
    Northern NJ
    [ double post, deleted ]
     
  20. Jan 11, 2018 #20

    johnpursley

    johnpursley

    johnpursley

    Old Rocket Guy

    Joined:
    Feb 11, 2011
    Messages:
    43
    Likes Received:
    0
    Actually, basswood sands quite quickly...if you don't think of it as "hard balsa." Rule #1: Use a high quality (it makes a difference) very coarse OPEN GRIT sandpaper. Bass has a strange clingy, packy (technical terms) sanding dust that quickly reduces the cutting speed of sandpaper. Open grit grit simply cuts faster and works better with bass. Rule #2: Sand ALONG the grain. Yup, sounds counter intuitive but bass sands faster when you sand parallel to the grain. You should be able to sand everything for the RAG in 30 minute or less.

    John Pursley
     

Share This Page