Accur8 Indigo Ragnarok Orbital Interceptor Build Thread

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

  1. Jan 11, 2018 #21

    johnpursley

    johnpursley

    johnpursley

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    Even though many elements of the instructions, cautions and whatever are repeated, often more than once you would be surprised how many emails I get with questions like "should I put a coat of clear on my skins before I start?" Rather than be a smart-a** and respond with "Have you read the instructions on any of the sheets?" (this particular question is answered on almost every single sheet in the kits...) Igenerally just give a straight answer that is "YES." So, even though it's repeated, folks don't see it. I hate to see space go wasted so pretty much every nook and cranny on the skin sheets have some kind of information applicable to the skin kit. The instructions have evolved over time for almost all my kits and frequently, as a result of correspondence with a modeler having a particular issue or problem I frequently immediately go to the graphics file for that kit and put the change (or something related) right on the skins so the next time it's printed you get the latest and greatest <sic>.

    I'm not much of one to skimp on replies. I realize the most STUPID question is the one that is not asked...so I appreciate those wo DO take the time to ask! ...And I try to respect that by providing thorough answers.

    John Pursley
     
  2. Jan 18, 2018 #22

    neil_w

    neil_w

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    Status update: I discussed this with John over email. He said that just printing new nose cone skins would not be a good idea since there's low chance of the new ones being a very close match to the old ones, plus the design has changed a bit. He graciously offered me a complete new set, but this build is way past the point where I can start fresh, so I decided to just finish up with what I have. I know what I'm dealing with, and my techniques for deal with unruly skin edges keep getting more refined, so I will make it work.

    I've learned a bit about the behavior of these skins (which may or may not be exactly the same as what John is shipping right now; still not 100% clear to me). Some of this was mentioned explicitly by John in emails during the purchase process, but having a lot of hands-on experience now makes my understanding much more nuanced. Here's my summary so far:

    A) Surfaces these skins like to adhere to, from best to worst:
    1) Other skin. Example would be the little overlap strips on the body tube wraps. This generally keeps the wraps in place pretty solidly.
    2) Finished surfaces. This is one reason why you must seal and paint all wood pieces.
    3) Unfinished surfaces. A fine example would be the body tube, where the cut-outs for fin attachment are made.​

    B) Also very important: these skins like to be flat (this characteristic is possibly enhanced by the clear-coat on top which adds a bit, however tiny, of additional stiffness). They will certainly conform to curves, but *all* the lifting I have seen involves curved skin trying to straighten out. In this respect it is very different from the stuff that Stickershock sells. Their vinyl is thicker but much softer and more compliant, and also reacts much better to softening with a hair dryer.

    By taking into account A and B you can anticipate and plan how to deal with most of the problems I've encountered.

    Proper build updates shall resume shortly.
     
  3. Jan 19, 2018 #23

    neil_w

    neil_w

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    The Cosmic Interceptor motor mount is a bit more involved than the usual, mostly because of the vanes and tail ring. John was very clever the way he adapted it to this model. Let's do it.

    On the Cosmic, the vanes extend beyond the diameter of the main BT. Here, the motor mount will be inside the sausage cut, so no room for that extra extension. And so the eight vanes are trimmed down as follows:
    IMG_6461.jpg

    Next, the mount is assembled as per the first 16 steps (!) of the instructions in the Cosmic Interceptor (steps 17 and 18 involve installation of the tail ring, but that goes unused here.)
    IMG_6469.jpg

    The motor mount tube is not a standard BT50, it is thick-walled and strong. The centering rings, on the other hand, are simple cardstock. While they presumably work fine for the motor mount, I'm certainly not going to anchor my Kevlar to them. I will pursue an alternate solution later. Usually I trim the motor hook, but on this one I left it intact. You'll see why below.

    Credit to John Boren for a very clever and well-thought out assembly sequence for the motor mount.

    The rear end of the mount is painted black; again I brushed on two coats of my Tamiya gloss black. On it's own this looks kind of crappy, but it's not a very visible part of the finished model and will be fine. Flat paint would have shown less of the surface imperfections.
    IMG_6502.jpg

    The finished mount goes into the sausage hole and butts up against the coupler that joins the two body tubes. This makes it easy to place the mount: just push it in until it stops. The fit is tight; after my first test-fitting I was unable to pull it out by hand, and had to grab the end of the tube with needle-nosed pliers and yank it out. I was very relieved it came out at all, and without damage. Since this had "seize-up" written all over it, glued in the mount with 30 minute epoxy. Here it is, installed:
    IMG_6503.jpg

    Note that I oriented the engine hook on the "inside". There is enough space to simply push the hook away from you, against the inside of the sausage cut, and remove the engine. Done this way, the hook is essentially invisible, and the extra finger grab on the end makes it easy to use.

    One final step remains: coat the inside of the sausage hole with a thin layer of epoxy, to protect it mostly from the burning of the delay grain. I'll get to that later. Next we'll start on the fins.
     
  4. Jan 22, 2018 #24

    neil_w

    neil_w

    neil_w

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    Here’s the inside of the sausage cut after applying a thin layer of epoxy.
    IMG_6508.jpg

    I seem to have forgotten that my epoxy (Great Planes 30 minute) does not dry clear. I will decide later whether to put another coat of black paint over this, or just leave it. If nothing else it does definitely seem to be well protected.
     
  5. Jan 23, 2018 #25

    neil_w

    neil_w

    neil_w

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    This build thread is getting much less interest than I expected, but I'm having fun writing it anyway. I had previously intended to document the fin skinning and assembly now, but I've changed my mind and will do the nose cone, which is the most challenging skin job. I was surprised how big these nose cones are, about 11" long not including the shoulder.

    Anyway: first we need to prep the nose cone. The gun ports on the bottom need to be filled in, and all the various channels (other than one) may optionally be filled. I figured I'd fill them all, why not? Well the reason why not turns out to be that it's a lot of work for not much benefit. I prepped my Trajector nose cone first, filling in all the channels (again, except the special one). After filling, it looked like this:
    IMG_6388.jpg

    I then decided not to fill the channels on the Cosmic nose cone just to save the effort. Then I swapped the two, so for this build I'm using the fully filled Trajector nose cone pictured above.

    Filler/primer and black gloss paint followed. My paint job turned out to be not nearly as smooth as I thought while I was painting. After seeing how challenging skinning the nose was on the Trajector, I knew I didn't want a bumpy paint job to cause me misery on this one, so I gave it a good wet-sanding with 1500 grit and then applied a coat of Future to give the vinyl a nice glossy surface to grip. The nose cone was now looking pretty darned good and ready to skin:
    IMG_6509.jpg

    The first skin piece is the hardest, as it must conform to the area around the cockpit. Having struggled a bit with this on the Trajector, I figured I could do better the second time. First I decided to pre-curl it, like I'd do with a transition, thinking maybe it would help it hold its shape better:
    IMG_6510.jpg

    This seemed like a good idea but I don't think it made the slightest difference. Here it is after application:
    IMG_6511.jpg

    I didn't get a particularly good alignment of the two ends of the wrap (call-out on the right), I give myself a B- for this. In the middle you can see a spot where I slipped with the Sharpie when I was blackening the edges of the skin. Turns out that will be covered later anyway, so it's a don't-care.

    The light-colored pieces near the cockpit are carefully cut off, leaving this:
    IMG_6512.jpg

    Next up comes the tip piece and the "glare shield" that goes on top, mostly covering the top seam:
    IMG_6513.jpg

    The glare shield didn't want to stay all the way down, so I sealed down the edges with Scotch Satin tape. John originally told me that clear tape is one way to affix skin edges, and to my surprise it worked really well on the Trajector so I was ready with it this time. It disappears against the skin almost completely. This close-up of the glare shield has a piece of tape on both sides holding down the edges, can you see them?
    IMG_6514.jpg

    Next the rear wrap goes on...
    IMG_6515.jpg

    ...and now I'm ready for the cockpit windows, which gave me a lot of trouble on the Trajector. One improvement here is that due to the black background, the front cockpit windows are done as a single piece that wraps over the top, rather than two separate pieces as on the Trajector. That means fewer edges to lift. :) I applied the pieces and the main change I made this time was that I burnished the living crap out of the edges with the curved back of a Sharpie (I've been doing that to all the edges on the nose cone). Knock on wood, the cockpit windows have stayed put so far. I'll keep an eye on them.

    Here's the finished nose cone. All told, there are 8 pieces of skin and (if I counted correctly) 6 pieces of corrective tape. I screwed up a bit here and there, but the end result is a handsome finished cone:
    [​IMG]

    The nose cone skinning process is very carefully thought out. I would be interested to know how long it took John to settle on the whole sequence, and the exact shape of all the pieces. It must have taken many iterations.
     

    Attached Files:

  6. Jan 23, 2018 #26

    Bat-mite

    Bat-mite

    Bat-mite

    Rocketeer in MD

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    Very interesting. Way outside my realm of experience. Not that I have a realm....
     
  7. Jan 23, 2018 #27

    neil_w

    neil_w

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    After doing a couple (well, 1 3/4 so far) of these skinned rockets, I'm pretty sure I would recommend to everyone to try one. It's a completely different build experience from the normal, and the end result is likewise very different and very cool.

    Estes still has the Trajector for $15.99... it's mighty cool with the NASA skin.
    [​IMG]

    IMG_6288.jpg
     
  8. Jan 23, 2018 #28

    GlenP

    GlenP

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  9. Jan 23, 2018 #29

    neil_w

    neil_w

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  10. Jan 24, 2018 #30

    les

    les

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    Not really "less interest". I've been watching and following each installment. I plan on getting one soon. Looks great.
    So fat I've done the Twilight Interceptor and NASA Trajector.
     
  11. Jan 24, 2018 #31

    neil_w

    neil_w

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    Remember that bit of exposed white at the front end of the body tube? Time to fix. I found an extra blue wrap strip that was included to use on the nose cone if needed. I did *not* need it for that, so it should work perfectly here.

    First I Sharpied around the very end end of the BT, so any exposed edges will not show white:
    IMG_6517.jpg

    Then I wrapped the blue strip around the end. Voila!
    IMG_6518.jpg
     
  12. Jan 24, 2018 #32

    neil_w

    neil_w

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    Check your PMs.
     
  13. Jan 24, 2018 #33

    neil_w

    neil_w

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    I updated the first post to reflect that John Pursley was originally inspired by this 1959 Aurora kit:
    [​IMG]

    Aurora updated and reissued that kit in 1976 as the Ragnarok Orbital Interceptor.

    There are a lot of cool old plastic models. Go get lost in the Fantastic Plastic model gallery for a while.
     
    Last edited: Jan 24, 2018
  14. Jan 24, 2018 #34

    Saluki

    Saluki

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    It would really be nice if John pursley would do a set of skins to represent the Aurora paint scheme.
     
  15. Jan 24, 2018 #35

    neil_w

    neil_w

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    He said he originally was going for the white color scheme, but changed it up at some point. The thing about the white is that you don't really need full-body skins for it; you could do it with white paint and some decals. The artwork is out there.
     
  16. Jan 26, 2018 #36

    Forever_Metal

    Forever_Metal

    Forever_Metal

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    I'll be doing my chair force and navy demo interceptors later this year using the skins!

    Looks good from here!

    fm
     
  17. Jan 26, 2018 #37

    neil_w

    neil_w

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    Nice, please post pics. John doesn't have any pics of the navy Interceptor finished model. Did you get the air force skin with chameleon or without? Do you have actual Interceptor kits or are you going the scratch route?

    Yes, I have questions. :)
     
  18. Jan 27, 2018 #38

    neil_w

    neil_w

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    OK, let's get cracking on the wings. A reminder yet again that I'm documenting the build in a different order than I've actually been doing it.

    After my crappy paint and sanding and polishing job, my wings looked pretty awful:
    IMG_6443.jpg IMG_6444.jpg

    Most of that doesn't matter once the skins are on. Here's how they looked immediately after:
    IMG_6445.jpg

    You can see where the surface of the paint is not flat under the skins, but it's not a big deal.

    A few more words about those wings are in order. John provides optional "cuffs" for the leading edges of the wings and stabilizers. These are simply long strips that can be wrapped around the edges to provide a more finished appearance. Further, the cuffs can be applied either under the main skins or over. Having already experienced some edge lifting, I thought that putting the cuffs over the wing skins would help hold down the edges. I also trimmed them a bit narrower so they wouldn't cover too much of the skin. Unfortunately I had the whole thing backwards. The next morning when I came to check on things, I was greeted with this:
    IMG_6447.jpg

    What you see there is that the cuffs have completely lifted from one side. In hindsight (and John confirmed this), putting the cuffs on first, *under* the main skins, would have worked better. First, I wouldn't have needed to trim them, since they'd be hidden. That would also have left a larger overlap between the skin and the cuff, which would have held better. The skin would have kept the cuff in place. Live and learn.

    I tried gluing down the cuffs with 3M 45 spray adhesive (yet another recommendation from John), but even it had a hard time holding down the cuffs, which really did not want to stay bent around the wing. And so I reverted to my Scotch Satin tape along the entire cuff, only on the underside of the wing, so it's not visible most of the time. They came out pretty good:
    IMG_6450.jpg

    One other thing I learned: John provides the skins slightly oversized, and then suggests trimming off the excess at the trailing edge. I could not do this effectively at all, so I ended up simply pre-cutting the skins a bit smaller than the fins, and simply living with a bit more exposed black at the trailing edge. I used this technique throughout the rest of the build. I am happy with the results.
     
  19. Jan 27, 2018 #39

    neil_w

    neil_w

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    Going in, the aspect of this build that gave the most concern was gluing the fins. I am used to gluing things unfinished with TBII and then applying some nice Quick and Thick fillets and knowing that everything is good and strong. On a skinned build wood glue fillets are not happening, since they'd have nothing to stick to, and would look ugly on top of the fins if they did. Would this thing hold together without my traditional fillets?

    John actually recommends using thin CA, claiming that a sort of "double glue joint" approach works very well with basswood and thin CA. I readily acknowledge that John has likely forgotten more about building rockets than I'll know in my lifetime, but I still couldn't get comfortable with this approach. And so, I decided to cross my fingers and just glue with TBII, and damn the fillets. I took some solace from the fact that the aspect ratios of almost all the fins provided for very long root edges, so I figured it had a decent chance to be strong enough.

    For the wings, the instructions are to glue the wings so that the tips are resting on the bench. First thing I had to do was secure the body tube in as perfect an upright position as possible, because any error would result in crooked wings. You'll see my rig in the first picture.

    Next, I prepared double-glue joints for the wings, and then applied the first one. I was very pleasantly surprised to see that the slot in the skin on the BT sort of held the wing root in position, and I didn't have to resort to any crazy trickery to get it to stay in place while drying. And so on went the two wings:
    IMG_6453.jpg

    The fact that the wings are sized and positioned to rest on the bench like that is yet another thoughtful design touch; without that it could have been a major challenge to get the wings on straight.

    OK, I said no fillets, but then I realized that I could do something. And that something is: medium CA fillets. I know they're not going to provide a huge amount of strength, but they do accomplish two things:
    1) "seal" the joint.
    2) Secure the edges of the skins at the joint.

    My first attempts at this worked very well, so I decided to stick with it for the rest of the build. Here's the assembly upside down on the bench while I apply the underside fillets:
    IMG_6454.jpg

    The medium CA fillets are nearly invisible in the final model, but do absolutely fill in and seal the joints.

    At this point it was starting to dawn on me that this is a big model, by far the biggest I've built (hey, I'm an LPR guy).
     
  20. Jan 27, 2018 #40

    Micromeister

    Micromeister

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    Very nicely done! A beauty of a rocket!
     

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