"Starship" - L3 Build Thread

Discussion in 'High Power Rocketry (HPR)' started by Ben Martin, Mar 4, 2019.

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  1. Mar 19, 2019 #31

    Ben Martin

    Ben Martin

    Ben Martin

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    Update #5

    Back from spring break!

    Picture #1 and #2: 3D printed sled came in from Additive Aerospace. It's beautifully designed and printed, looking forward to installing all the electronics and attaching it to the payload bay.

    Picture #3: Cut out a cardboard fin alignment guide for tomorrow.

    Picture #4: Sanded bases of fins with 120 grit in preparation for epoxy. Labelled each fin and its accompanying slot to ensure they fit properly.

    Picture #5: It's hard to tell, but I sanded the motor tube where the fins will be epoxied on. It required some innovative solutions since I didn't sand it before installing for some reason. Lets just say that there was a ruler, adhesive putty, sandpaper, and blue shop towels involved.

    I plan on doing a good sized fillet on the fin root and I'm deciding between foaming and traditional interior fillets. I'm leaning towards interior fillets but since the fins are so long and the gap is so narrow, I don't think it's going to be very easy to do. Injecting fillets is out of the question due to me using RocketPoxy. 20190318_221957.jpeg 20190318_222004.jpeg 20190318_222047.jpeg 20190318_222132.jpeg 20190318_234617.jpeg
     
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  2. Mar 20, 2019 #32

    Ben Martin

    Ben Martin

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    Update #6

    I made some excellent progress today!

    Picture #1: Epoxied the first fin on, ensuring that it is aligned proerly.

    Picture #2: Epoxied the second fin on, refining the process from the first one.

    Picture #3: Cardboard fin alignment guide seems to be doing a great job, have to make sure that the fins are perfectly aligned as it only has 3 fins.

    Picture #4: This picture shows the healthy epoxy fillet that I applied to the base of the fin, it turned out better than I expected.

    Picture #5: Close up on fillet, showing more detail.

    Picture #6: The booster section barely fit on my desk to dry overnight. I ensured that my roommate won't whack it with the door.

    Tomorrow I will be attaching the last fin and working on interior fillets which should be a blast. 20190319_191744.jpeg 20190320_010133.jpeg 20190320_010140.jpeg 20190320_010206.jpeg 20190320_010149.jpeg 20190320_011550.jpeg
     
  3. Mar 20, 2019 #33

    Bat-mite

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    Nice work on the internal fillets. Mine always look like they got tarred and feathered. Oh, wait, that's my external fillets. :oops:
     
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  4. Mar 20, 2019 #34

    chuck5395

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    Agreed. Nicely done.
     
  5. Mar 20, 2019 #35

    Ben Martin

    Ben Martin

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    Thanks! I can guarantee that the upper fillets won't turn out so well due to it being a *bit* tight . RocketPoxy has been great so far, looking forward to doing exterior fillets with it.
     
  6. Mar 21, 2019 #36

    Ben Martin

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    Update #7

    Picture #1: Installed the last fin.

    Picture #2: Another view of the fins.

    I plan on doing the interior fillets tomorrow, it's going to be a blast as the fins are too long for my wooden dowels. Time for some innovation and experimentation. 20190320_235742.jpeg 20190321_000005.jpeg
     
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  7. Mar 21, 2019 #37

    KC3KNM

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    The build looks great so far, impressive endeavor for a dorm room build! We built quite a few RC planes in our dorm and common areas... I know how much of a pain it can be to live in the dorms, less yet set up a workshop in them :D.
     
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  8. Mar 21, 2019 #38

    jqavins

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    A suggestion for your consideration: Choose an epoxy that's just a little runny, that is, one that runs but slowly. Set a fin vertical so that the other two each have one face forming a down-pointing V with either the airframe or MMT. Use a long thin dowel or stiff wire (like a cut up clothes hanger) to push epoxy into place along most of the length of the fin root, leaving a little at either end dry so the epoxy doesn't run off. Then just let it settle into place and form the fillet by itself. It won't be pretty, but who cares, it's on the inside?
     
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  9. Mar 21, 2019 #39

    Ben Martin

    Ben Martin

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    I don't have any other epoxy on hand and don't plan on spending money while I have a ton of RocketPoxy. My plan with RocketPoxy is to use the dowel to apply the epoxy. Even though it won't reach all the way down, it should still do the job.
     
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  10. Mar 21, 2019 #40

    Nytrunner

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    What's the prime motivator here? (aka, what motor are you planning for certification?)

    If it's under 35lbs, you're looking at busting 10k on a baby M
     
  11. Mar 21, 2019 #41

    Ben Martin

    Ben Martin

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    Probably something like the M1350W. I'm well aware that it will break 10K and mach.
     
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  12. Mar 23, 2019 #42

    Ben Martin

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    Update #8

    I picked up the stainless steel ubolts today from Home Depot. I also worked on the interior fillets, which turned out to be a bigger challenge than I expected.

    Picture #1: View of the fillets, the left fillet has the upper and lower fillet. I completed 2/6 interior fillets today due to how fun they are.

    Picture #2: Picture of the fin assembly at this point in time.

    I first attempted to just use a dowel to reach in and apply the epoxy. The dowel ended up being too large relative to the gap so the epoxy just grabbed onto the tube instead of remaining on the dowel. This caused a mess and made it difficult to get epoxy all of the way down.

    Second attempt was to deposit a generous amount of epoxy at the end of the fin root and let gravity do the work. The thing is... it's RocketPoxy. RocketPoxy, even when freshly mixed, laughs at gravity. So I ended up using a dowel to push the blob of epoxy down the root, which ended up being a lot easier/cleaner than the first attempt but not ideal. I plan on doing the rest of the interior fillets with this method as I cannot think of a better way.

    If any of you guys have suggestions for how to make the process easier, please feel free to share them. Fillet ejection is out of the picture and so is foaming, not many options at this point but you guys might have another angle to this problem. 20190322_230400.jpeg 20190322_230424.jpeg
     
  13. Mar 24, 2019 #43

    CaptHaywire

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    This is how I solved the problem. Pick up a dosage syringe that can be found at a drug store and vinyl tubing from the local hardware. Heat the RocketPoxy resin and hardener separately to 100 F. I used a microwave for this but be careful with small amounts, it is easy to overheat. Mix them together and pack into the end of the syringe. Place the tubing all the way forward and walk it back while injecting the mix. The epoxy is not at the elevated temp very long so you should have plenty of time to work.
     
  14. Mar 24, 2019 #44

    Ben Martin

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    I'm not sure if a syringe would even fit in the crack, and if it did, it would not hold nearly enough. I definitely need to heat up the resin and hardener as both of them are extremely thick. Is the resin supposed to be thick and cloudy for rocketpoxy?
     
  15. Mar 24, 2019 #45

    CaptHaywire

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    Yes the resin is very thick and that is why I heat it. Do not heat them together because the microwave may create a hot spot and then it starts to set.

    Determine the length of vinyl tube required to reach the front of the fins and add a few inches. Pack the syringe, attach the tube and inject away. I hope that helps.
     
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  16. Mar 24, 2019 #46

    jqavins

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    The syringe and long tube sounds good. Here is a simpler, but in other ways probably inferior, option. Inferior but likely good enough.

    Do what you did the first timet but use a thinner pusher. A thinner wooden dowel might be too floppy, but you can use a metal rod. Wire clothes hangers are cheap and everywhere. Cut the bottom out of one and use that to push the epoxy around. Use a saw to cut it, not wire cutters, as the square end you can get with a saw will work much better. Surely somewhere on campus you can find a disposable hanger and a hack saw without spending money.
     
  17. Mar 25, 2019 #47

    Ben Martin

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    Update #9

    Photo #1: Finished the last interior fillet. They may not be pretty, but they get the job done.

    Photo #2: An overview of the mess that the interior fillets caused.

    Today I will be epoxying on the rear centering ring and the motor retainer. 20190325_012415.jpeg 20190325_012500.jpeg
     
  18. Mar 25, 2019 #48

    jqavins

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    Here's a silly question: with the fin tabs so firmly attached both to the airframe and motor mount tube, is there any reason other than 1) tradition and 2) aesthetic cover-up to install an aft centering ring? Seems like structurally you'd be just fine without it.
     
  19. Mar 25, 2019 #49

    Nytrunner

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    Interesting question since the tube is locked in place (centered) already with the fins and forward ring. Arguments could be made for the extra bonding area of ring to mmt, bt, and fin backs, as well as its use transmitting forces from the retainer to the fin tabs via compression as opposed to adhesive shear strength only.

    That being said.....if the construction and bonding is sound...I can't actually come up with a good reason why not to try it
     
  20. Mar 25, 2019 #50

    Ben Martin

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    The relatively small increase in mass is worth the strength gained by having a rear centering ring. I don't have any reason not to install the rear centering ring, but it does not really do anything besides lock down the fins and transfer some forces.

    The rear centering ring does not even touch the motor retainer as it's a tailcone. It will just sit flush with the rear of the fins.
     
  21. Mar 26, 2019 #51

    blackjack2564

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    If using a standard retainer [rather than tailcone] the rear CR blocks back of tube from base drag during delay burn, otherwise it would "suck" up hot gases and char interior of rear tube.
    You see this all the time when flying clusters, but only flying central motor, if not blocking open tubes. They get charged/burned on interior.
     
  22. Mar 26, 2019 #52

    Ben Martin

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    Update #10

    Picture #1 and #2: Installed rear centering ring.

    Tomorrow I will be installing the motor retainer with JB Weld and completing one set of external fillets. I'm still looking for a place to buy 2 Stratologger CFs. PerfectFlite has been out of stock and not responding to emails while all of their vendors also don't have any in stock. For such a popular altimeters I find this weird. 20190326_003821.jpeg 20190326_003756.jpeg
     
  23. Mar 26, 2019 #53

    swatkat

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    Looks great! I will doing the exact same build, with just a few changes to my Performer 98. Waiting on delivery as mine has the aluminum nose tip. I'm using an 8 foot roto-chute from Bama Chutes on mine with 2 foot matching drogue. We have four people in our club doing this exact build, hoping for a drag race! (Same chute as mine as well, bulk order).
     
  24. Mar 26, 2019 #54

    Ben Martin

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    Thank you! The only holdup in this build so far is the electronics, which the Stratologger CFs are out of stock everywhere. That sounds like a lot of fun with your club, 8ft and 2ft sound like a good combo.
     
  25. Mar 26, 2019 #55

    Nytrunner

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    Check out Missileworks RRC2 and RRC3

    The RRC2 is a simple dip-programmable non-logging dual deploy alt, and the RRC3 is an extremely capable logging dual-deploy alt
     
  26. Mar 26, 2019 #56

    Bat-mite

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    Quick switch to RRC3?
     
  27. Mar 26, 2019 #57

    Tim51

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    Also being a fan of the SLCF I phoned Perfectflite some time back re a possible purchase. The lady who answered said that there was illness in the family. Understandably that's had an impact on the business and fulfilling orders.
    Great build by the way.
     
  28. Mar 26, 2019 #58

    Ben Martin

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    I actually originally planned for an RRC2+ and RRC3 but decided to go with Stratologger CFs due to the simplicity. It's too late to change now as I already bought the 3D printed sled and it doesn't work with Missilework altimeters. This was of course before all of the CFs went out of stock and you can't buy them anywhere right now, so I'm in between a rock and a hard place. Just have to wait it out I suppose.
     
  29. Mar 26, 2019 #59

    Ben Martin

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    Thanks! It's a shame about the lack of production, it's been like this for a while. None of the vendors have it in stock and PerfectFlite ran out recently. They haven't been responding to emails so the illness makes sense. Hopefully, they get better soon so that I can get my 2 CFs and others can order their altimeters as well.
     
  30. Mar 26, 2019 #60

    Bat-mite

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    That's unfortunate. I wish them well.
     
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