LOC Graduator Build - "Diomedes"

Discussion in 'Mid Power Rocketry (MPR)' started by JCRL, Oct 9, 2019.

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  1. Nov 22, 2019 #31

    JCRL

    JCRL

    JCRL

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    I glued my rocket together over the last few days. I hadn't used two-part epoxy before this project. I used a 5 minute epoxy to glue in the forward centering ring. Next I used CA to tack the fins to the MMT and popped in the rear centering ring. Once that had dried for 24hrs, I removed the rear centering ring and used a 30 minute epoxy to apply all the interior and exterior fillets. It's extremely messy on the inside and regular messy on the outside. I couldn't get the hang of making the fillets with a popsicle stick without pushing epoxy further up the fin and onto the body tube. I assume that this just comes with practice, but if anyone had helpful tips, I'm all ears. Anyway, I cleaned the rocket the best I could with rubbing alcohol and I'm hoping the excess sands easily.

    Since this is my first time doing this, please let me know if you see any errors or causes for concerns.

    IMG_20191122_084647.jpg IMG_20191122_084704.jpg IMG_20191122_084721.jpg
     
  2. Nov 22, 2019 #32

    ChicagoDave

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    Excellent progress on your Graduator!!

    I usually use tape to mask off the fins and body tube where you don't want the epoxy to go. For example on the external fillets I would mask off one popsicle width of space for the epoxy. Then after about 5 - 7 minutes pull up the tape so it doesn't get epoxied in place!!

    For the interior fillets, neatness doesn't count :) Just keep in mind you're adding weight to the back of the rocket which will move the CG back a little, so take that into account when running the SIMs.
     
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  3. Nov 22, 2019 #33

    Nytrunner

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    YIf you've gotten epoxy on the inside of the tube behind the fins, you may need to do some sanding to get the rear centering ring to fit in there
     
  4. Nov 22, 2019 #34

    JCRL

    JCRL

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    Great tip! It's so obvious once it's pointed out.
     
  5. Nov 22, 2019 #35

    JCRL

    JCRL

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    Glued the rear centering in place just now. @Nytrunner there was a lot of goop on the ends and it required lots of sanding. It seated well though. Next step is to JB Weld the retainer in place.
    IMG_20191122_135510.jpg
     
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  6. Nov 23, 2019 #36

    caveduck

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    Nice going! Graduators are super versatile and fun. Mine is over 30 years old and still flying fine. You can eventually get your Level 1 cert with an H97 or the like. An F67 is a great non-HPR motor for it.
     
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  7. Nov 25, 2019 #37

    JCRL

    JCRL

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    Fixed an aluminum retainer to the end of the rocket using JB Weld on Sunday.
    IMG_20191125_110204.jpg

    Tied the shock cord and attached quick links for the parachute and payload bay. Glued on launch lugs. Assembled the payload section. I'm nervous about the payload bulkhead because it was really loose and wobbly - came out of the package this way. I was hoping that a little bit of glue would fix the problem but the bulkhead started sliding down into the coupler when drying upright. I let it dry for 15 minutes on it's side and then stood it up - seems to be good now.
    IMG_20191125_132405.jpg
     
  8. Nov 25, 2019 #38

    JCRL

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    Well crap, the bulkhead fell through the coupler - luckily I caught it before it got cemented halfway down and sideways.

    I guess I'll let it sit for 24 hours and hope that the epoxy adds enough material to the bulkhead for it to fit next time.
     
  9. Dec 2, 2019 #39

    JCRL

    JCRL

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    Alright, so after the bulkhead fell through the payload tube, I let everything dry for 24 hours. I sanded down the inside of the payload tube and the outside edge of the bulkhead until they fit together securely. Then using 5 minute epoxy, I repeated the process of gluing the bulkhead in place. This time it was successful, however, the area where the bulkhead sits in the coupler swelled and made the fit of the payload tube to the booster so tight, that I was afraid they were inseparable. Well, I sanded the hell out of the coupler to level out the bulge and the rocket sections fit smoothly and snugly now. My only hope is that there won't be some kind of catastrophic weakness in the coupler/bulkhead.
     
  10. Dec 3, 2019 #40

    ChicagoDave

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    One trick I've used is to "tack" things in place with 5 minute epoxy, then go back with 30 minute epoxy to secure the joint. (That or use CA to tack, if that makes more sense, depending on what is being joined...)

    On the bulkhead I put about 1/8" of 30 minute epoxy over the whole plywood to provide some extra protection against the ejection charge. Not sure if that was necessary but it was easier than just making a fillet.
    bulkhead.jpg
     
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