Loc 7.5in 1/2 scale Phoenix Missile Build

Discussion in 'High Power Rocketry (HPR)' started by Merlrem, Dec 5, 2017.

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  1. Dec 5, 2017 #1

    Merlrem

    Merlrem

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    I've been lurking here for a while, so I figured I'd make an account and post my level 2 build. I got a Loc 1/2 scale Aim-54c phoenix missile from AMW on Black Friday for their awesome deal, and I've just started construction. The kit is relatively new and lacks documentation, but the nice guys at Loc have been very responsive to my emails so far.

    The kit should fly well on a large J / baby K, and with the right reinforcement it could likely fly on an M. I'm not l3 though and I don't have much anticipation of going for that in the near future though. It's about 6 1/2 feet long, and the aftmost airframe section is actually made up of two pieces, a 30in section and an 8in section.

    Anyways, so far I've built much of the new Loc adjustable nose weight system and I've rounded my fins. Lots of work to do and I plan on taking my time with this one, so updates will probably be slow here.

    Anyways, I've attached some pics of the progress so far. AMW threw in a free 7.5in E-bay, so I'm planning on using that for the dual deploy setup. Unfortunately, there isn't much airframe between the ebay and the first coupler (highlighted in brown in the image attached), so I'll have to figure out exactly how to get all of my recovery stuff in place. I'm currently planning on cutting the green coupler, because right now according to the provided rocsim files it will intersect with my forward centering ring. Is this the right plan? I can also move the forward centering ring back.

    20171201_141739.jpg

    20171203_141627.jpg

    20171203_141658.jpg

    Capture.jpg
     
  2. Dec 5, 2017 #2

    qquake2k

    qquake2k

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    Looks like a fun project!
     
  3. Dec 5, 2017 #3

    cavecentral

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    This looks suspiciously familiar. The holes in the tables are a dead give away.
     
  4. Dec 5, 2017 #4

    Kallahan11

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    I've got that exact tabletop for my computer desk at home, my father is a Steelcase retiree.
     
  5. Dec 5, 2017 #5

    Eric

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  6. Dec 5, 2017 #6

    Merlrem

    Merlrem

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    haha yeah! I figured as it's a new kit without many existing threads, I'd start my own!


    Solid build! How was it sanding down that forward centering ring? I'm considering just cutting my coupler, but I have access to a belt sander which would make sanding a good option.

    I'm planning on finishing the adjustable nose weight system this afternoon and attaching my forward centering ring and first coupler. I'll update again once that's done!
     
  7. Dec 5, 2017 #7

    Eric

    Eric

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    Took a couple minutes on the belt sander. It wasn't to bad. But with enough epoxy, it looks amazing.

    Sent from my VS988 using Tapatalk
     
  8. Dec 6, 2017 #8

    Merlrem

    Merlrem

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    Alright I went ahead and sanded down the forward ring on a disc sander. Super easy to get a perfectly vertical edge, and it fits nicely into the coupler now. I also went ahead and trimmed the included coupler so it would fit with only 2.25 in of overlap with the 8in middle airframe section, so that the e-bay can get a comfortable 5.25in of overlap. I didn't have time to epoxy in the front centering ring today, but now I have plenty of time to plan out exactly how I want to do the motor mount before I continue the build.

    I'm at the point where I need to decide exactly what strength to weight ratio I want, which is a tough decision. I want to be able to eventually fly on bigger L's, but I'll be flying on smaller motors most of the time so I don't want to be able to fly monster motors if it means I can't fly on a small K / big J any more. Either way, I have to decide now what kind of reinforcements to do. I'm considering threaded rods in my motor mount or filling it up with expanding foam or both. I'm likely going to do tip to tip fiberglassing on these huge fins, but I probably won't fiberglass the upper sections or anything.

    Here are some pics from today:

    20171205_183111.jpg

    20171205_183108.jpg

    20171205_183043.jpg
     
  9. Dec 6, 2017 #9

    Eric

    Eric

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    Its looking good. Do the fins only have a small tab to go Through the wall?

    Sent from my VS988 using Tapatalk
     
  10. Dec 6, 2017 #10

    ECayemberg

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    Looks good; it's one rad rocket for sure!!!! Looking forward to following along!

    The stock 7.5" Phoenix takes L motors without issue; I wouldn't hesitate to stick an M in there either. Built stock, it doesn't need reinforcement for the motors mentioned. Tip to tip isn't a bad idea....if you plan to go fast enough to wiggle the fins. Still, the fins are relatively short in span and long in root, so there's not a ton of room to flex there.

    Adding threaded rod to the motor mount isn't a good idea, in my opinion. No need for it, no structural benefit, and it adds a load of weight to the wrong end of a rocket that already needs nose weight. Skip it! Foam it if you like; less weight and more structural benefit....if you feel it necessary:)
     
  11. Dec 6, 2017 #11

    Merlrem

    Merlrem

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    Ah, that's what I was hoping for. I doubt I will foam the motor mount, then, just because it makes repairs and later access incredibly difficult, and I won't be pushing this airframe to its limits in the near future. I'll see later whether I want to fiberglass the fin can. I'm more worried about hard landings and breaks from storage/transportation than I am about fin flutter, and I want to learn tip-to-tip anyways.

    -Tom
     
  12. Dec 7, 2017 #12

    MaxQ

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    Nice project...welcome!
     
  13. Jan 11, 2018 #13

    Merlrem

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    After a long break for the holidays, I'm back at work on this!

    Since the last post I've attached the motor mount and started work on the fins.

    Here's a pic of the forward ring connection. Note how the ring sits inside of the rearmost coupler. The coupler is epoxied on both sides. I believe this was done to avoid having to produce and ship the 38 inch lower section. By shipping a 30 inch and 8 inch pieces, it all fits in a 30 inch box quite snuggly. Also, it makes the lower airframe a bit stronger, since the payload bay can butt up right against that coupler.
    [​IMG]

    I epoxied the ring in with the last of my 30 minute hobby epoxy, so I did the outer fillet in proline, which is strong but incredibly messy. At least you can't see this part... While I was gone I ordered a $30 quart of Aeropoxy ES6209 from Giant Leap, as it is supposedly the strongest epoxy for wood by a wide margin. I plan to use it for my interior fillets and all of my structural joints, but I'll probably find something lighter and cheaper for external joints. Maybe aeropoxy light.
    [​IMG]
    [​IMG]

    Here's the aft: I've got a flanged 75mm Aeropack retainer, which I plan to use with a 75-54mm quick change adapter for most of my flights.
    [​IMG]

    I'll make a separate post for the fins progress.
     
  14. Jan 11, 2018 #14

    Merlrem

    Merlrem

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    So unfortunately the fins that came with the kit were pretty warped, but that is to be somewhat expected with fins this size. I've put in quite a bit of effort to straighten them, but I've made little progress. There's one fin that I'm particularly worried about, but I don't really have the means to recut them any time soon, and I've already rounded them so I'd rather not. I've tried moistening the concave sides and clamping them down and even ironing them, but one of the fins remains warped as ever.
    [​IMG]

    Here they are layed out next to the rocket, showing the overall size relationship of everything and how it will be finally assembled:
    [​IMG]

    I attached them by clamping them to some 48 inch aluminum angles, which removed any chance of side-to-side warp being an issue. Unfortunately, there is a small amount of twist in some of the fins that remains. I'll have to figure out what to do about that.

    Photo boxes are very handy for setting up rigs to hold everything together. A rubber band around the leading edges keeps them pressed right up against the body tube and prevents them from leaning at all.
    [​IMG]

    It took about 10 grams of aeropoxy each to attach the roots the fins with a thick coat of it. The long pot life and minimal flow really, really helps with fins this big. I was careful to avoid putting much epoxy at all at the very back of the fin roots, because I'll be pressing the middle centering ring up against the back of these forward fins and I don't want any epoxy blobs blocking that. The large diameter should make internal fillets a breeze. I got some "jello shot syringes" that I plan to use to apply the internal fillets, because they're basically the only ones big enough to actually suck up the aeropoxy. This stuff is incredibly thick, and calling it "pourable" is kind of a stretch. I've been using a spoon to help measure it out.

    [​IMG]

    Here's a bonus pic of the payload bay that AMW kindly included for free for black friday. Usually it's a bit of a struggle to fit everything into E-bay, but I definitely won't be having any trouble with this one haha.
    [​IMG]

    With the two opposite forward fins attached, here's what it looks like right now:
    [​IMG]

    It's kind of a pain to think that I'm going to have to repeat this entire fin process again for the aft fins, but it should be worth it. From bottom to top, there are 5 distinct sections: the fin can, which is permanently attached to the 8 inch middle airframe where the drogue chute will sit. Next is the E-bay which will be epoxied to the 18.5 inch payload section where the main lives.

    Finally the nose cone, which has the loc adjustable nose weight system. I'm pretty sure it's the same system as the one in the 5 inch phoenix. This works by mounting a 3 inch tube in the nose cone, where you can insert a weight module followed by a short coupler to keep it pushed all the way up. It's held in place by another bulkhead bolted to the back of the one that holds the tube. The shock cord mounts directly to the weight module, which is nice. Unfortunately, you have to buy an additional coupler, bulkheads, and eyebolt each time you want to make a new weight module, but I don't anticipate having to make too many of them.

    I'll probably have all four fins attached by the end of the week with internal fillets done over the weekend, assuming I can figure out how to unwarp the trouble fin.
     
  15. Jan 11, 2018 #15

    Tim51

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    Glad to see the build progressing - thanks for posting great pics and detailed account of the experience.
     
  16. Jan 12, 2018 #16

    Merlrem

    Merlrem

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    All 4 wings are now attached. I've finished most of the internal fillets for them, using roughly 5g of aeropoxy per fillet. I also made a super handy, heavy duty stand this afternoon for this rocket and any future 12in or smaller rockets. It uses about 14ft of 1in PVC plus some split insulation foam, and can hold 3 rockets or more if you double up.

    [​IMG]

    Luckily, the gap between the fins and the wings is large enough for the mount to fit between them. Unluckily, the wings extend so far forwards that you have to have the forward section mounted to put it on the stand. This is a major pain, because connecting and disconnecting 7.5in cardboard airframe sections is a serious PITA. Any slight misalignment or distortion of the tubes completely prevents them from fitting. Hopefully I'll figure out a good way to do this, or just heavily loosen the fit of the two pieces and rely on the sheer pins more.

    Here's a bonus pic of the mock-up for the finished bird:
    [​IMG]

    This evening I'll do the last set of fillets, mount the middle centering ring up against the back of the wing tabs, and start mounting the fins.

    It's also time to start thinking about my recovery plan and electronics! I've got the included 78in LOC chute and a tubular nylon shock cord (not sure how long it is), but I need to pick out a drogue and make my recovery harnesses. Since I used a pair of U-bolts for the fin can, I'll need to get a couple short sections of nylon or kevlar, and some swivels and quick links to connect it all up. That's something I can think about later though.

    For electronics, I'm going to go for redundancy here. Since this is the most money I've ever spent on a rocket, I don't mind spending to have a second altimeter to ensure I get it back safely. I'll probably use a Stratologger and an RRC3 for diversity, each with a pair of parallel batteries and it's own pair of ejection charges. These are the cheapest ones available and I've already got access to stratologgers, and the only thing they're missing AFAIK is telemetry, but if anyone has any comments about altimeter choices I'd love to get some input. I have plans to build a custom radio flight computer eventually but I'll wait on that until this thing is done and flown.
     
  17. Jan 13, 2018 #17

    ksaves2

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  18. Feb 17, 2018 #18

    Merlrem

    Merlrem

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    Been a while since the last update, but I've got all the centering rings in, and the fillets done. The rocket's been moving around quite a bit, so progress has been pretty slow. Back in the groove now, though. Target is to launch mid-late April, which should be doable. I've still got to setup the recovery system, but I've been slowly amassing the parts for it.

    Pics:

    Internal fillets: (Unfortunately, I forgot to take a pic of the rear internal fillets before I put the last centering ring on, so this is the only pic I have.)
    [​IMG]

    Another pic of installing the fins:
    [​IMG]

    Here it is with a 4" pac-3:
    [​IMG]

    External fillets:
    [​IMG]

    [​IMG]

    I plan on doing tip-to-tip fiberglassing on the fin can, and while I'm at it I might as well glass the payload tube. It should make those rear fins pretty indestructible when it comes to the landing, and help prevent any zippering. Also, it should hopefully help straighten out the warping on some of the fins. Going to start that process probably in a couple of weeks, so it might be a little while before the next update.
     
  19. Feb 18, 2018 #19

    Sevian

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    Are you going to have adjustable nose weight? If so, what are your plans?
     
  20. Feb 18, 2018 #20

    Tim51

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    Nice job.
     

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