L1/L2 Super DX3 Build (After the Fact)

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pendrin2020

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So I'm sure there's been a million of these builds, but here's mine. lol. I'm an older Student at Tennessee Tech, and I've been into rockets on and off for about 20 years. I never quite found myself in a situation where money, time, and a valid excuse all occurred simultaneously for me to get certified. In this case, the excuse was potent enough to justify whipping out the credit card, and making time.

I'm the project manager for a SEDS chapter here at tech, and we need someone with their L2 so that we can fly in a competition later this semester. As a group we've all been building for years, but we've always just had someone around who could be "the motor guy". This semester, we needed a new one. I him-hawed for a bit, but decided to take the plunge on a MadCow 4" Super DX3. It was cheap, and I figured I could get out for around $300 before motors... some of you are laughing already.

Right after I Got my tracking number for the kit, I got a wild hair up my crack... this is a hair that I am sure you are all very familiar with...

"well, if I'm gonna go that far..."

I set to work planning how I was gonna turn this simple cardboard beast into a true head-turner. Before the parts had even shipped, I had placed another order with MadCow, and several orders on Amazon.

The next week, the kit arrived from MadCow, and I took the obligatory social media shot. The guitar case for reference made sure I got a response from friends and family. :lol:

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Kit Contents:
31" Pre-Slotted aft airframe
19" Payload tube
16.5" Plastic Nose cone
2 centering rings
1/4" Birch plywood fins
rail buttons
shock cord

Other parts I was waiting on:
Parachute
4"x31" replacement airframe tube to replace payload tube.
60" Nomex shock cord protector
9" Nomex square (I know, too small)
better recovery hardware (no forged hardware? C'mon MadCow)
extra centering ring
Motor retainer
Building supplies (This is a massive list)

Here was the plan:

1. I'd extend it so that I could sub-divide the payload bay for cameras and experimental electronics payloads, and still be able to do dual-deploy.
2. I'd buy the plywood and hardware necessary to convert the coupler to an AV bay (centering ring cut from old payload bay)
3. Internal. Fiberglass. Fillets. and I'm not talking shredded fibers. WE DOIN' A LAY-UP IN THIS B****.

Next Post: The Tale of the Over-Built Fin Can.
 
After the rest of the parts rolled in, I started on the fin can. First I prepped the tubes and surfaces. I sanded down through the glaze on the body tube, and just went ahead a pealed the glaze layer off the motor tube.

The motor tube was a no-brainer. The rings were attached with 5 minute epoxy so that the ring with the shock cord mount had a 1/4" lip of motor tube. The middle centering ring was placed strategically to meet the leading edge of the fin slots when there was approximately 1/2" of motor tube protruding from the back of the rocket. Total no-brainer right? yeah... bout that.

The middle centering ring wound up 1/2" too far forward, and I had to eyeball the overhang. This meant I wasn't sure whether or not there was enough motor tube after the rear centering ring was installed to install the Aeropack retainer I had bought. Every so often I get a good feeling when I build something. I look at it, and I go, "Yo, I totally nailed that". And that was the feeling I got when I looked at the overhang when I eyeballed it. I decided to trust my intuition.

A few minutes later, the epoxy had hardened significantly. I dry fitted the fins, centering ring, and retainer. Flawless... not a millimeter too much, and not a millimeter too little.

Feeling victorious, I then I dusted off my T-square and drafted the fin-alignment guide from scratch.

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before I attached the fins, I took them outside and put a nice parabolic profile on both the leading an trailing edges. It took a while to be happy with them, but I think it was totally worth it.

Some 5 minute epoxy securely fastened them to the motor tube, and I began to prepare for the mess I was about to make. Now, I've never worked with fiberglass cloth and resin before, not like I was about to do. I'd used small patches of it to reinforce fillets and such, but I'd never tried to just outright laminate something. I was feeling lucky (and adventurous), so I just went out onto my deck, with temps in the 30's, I put down a plastic sheet, I mixed up some bondo polyester epoxy, and I set to work.

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I started by using a tongue depressor to spread epoxy on body tube, motor tube, and fins. Then I folded a 5"x5" square of 6oz fiberglass around the tongue depressor, and blindly tried to smooth it against the epoxy. I couldn't see past my hand, so I kept having to stop and rotate the fin can towards the flood light I was using (it was night, obviously). When I was done, there was a smooth sheet of fiberglass on both side of each fin that connected the body tube to the fin to the motor mount. Another round of social media pics had my buddy Allen Hall telling me it might be the strongest paper fin can he'd ever seen. I think he was being nice, but I'm still stupid proud of it.

After the layup, it was still 35 degrees outside, so I had to stand there and bake my work with a hair dryer for 45 minutes before it had cured enough to bring inside without smelling up the house. Thankfully, that meant I was free to start sanding it as well, so I was back outside with my dremel ten minutes after that cleaning up the excess epoxy and stray fiberglass strands. Here she is, mid-grinding.

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This was probably the most gratifying portion of the build. Seeing these pics makes me glad I didn't just buy a big fiberglass kit like I wanted to originally. I was so proud of that fiberglass job, that I waited several days to install the aft centering ring so that I could show it off to my friends in the school makerspace. I may be almost 30, but you don't act like a kid every now and again, no one will appreciate you when you're an adult. :cool:

Next up The AV bay.
 
Eventually, I had to seal up the can, and put some exterior fillets on it. The internal lay-up was strong enough that I considered these a cosmetic and aerodynamic addition. I taped off my lines, I mixed up some 5 minute epoxy (It was what I had on hand), and i Layed out all six fillets in about an hour and a half. In spite of the terrible epoxy choice, they still came out great.

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The rest of build is pretty chaotic. I immediately set to work carving seven new bulk plates. I needed six airframe bulk plates and one for the coupler. I managed to carve them out of 1/4" Birch ply on a scroll saw. With a little bit of trimming with a dremel, they all seemed to slide right into place. The AV bay was the easiest addition. I drilled the necessary holes for the all-thread and the 1/4" u-bolts, and slapped it together.

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One addition I was extremely unsure about, but I had seen enough examples of to justify trying, was a single baffle plate in the fin can to allow me to mount a U-bolt after having already installed the motor mount. I epoxied two bulkplates together, installed the u-bolt, an proceded to drill as many holes in it as I dared. I slathered epoxy around the body tube, just above the motor mount, and slid it into place. (I would find after doing this that two hours of googling the topic is not enough as an additional 10 minutes of googling will yield drawings of far more attractive designs) :facepalm:

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Nevertheless, my 1/2" baffleplate functioned as intended allowing both 2 gram motor ejection charges, for both of my cert flights to separate the rocket at apogee (and a 2 gram test charge before my L1 attempt).

Next up is the finish.
 
I forgot to mention that i cut a centering ring from the old payload bay and installed it on the AV bay. It wasn't the most flawless cut, but it got the job done for the moment. The red stuff is bondo filler. Remember what I said about chaotic? lol

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That red filler was rubbed into the fins, and the spiral creases of the tubes and then sanded as smooth as I could make them.

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After that, I installed the rail buttons and the forward bulkplate that subdivided the payload section, and she was ready for paint A few coats of primer later, she looked like this.

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Tomorrow, I'll talk about weight, balance, and recovery.
 
Those fillets look awfully nice, especially with a high degree of difficulty for being done with 5-minute epoxy. A 10 from the judges! Also, I love rockets with flat paint.
 
"well, if I'm gonna go that far..."

It is my personally held belief that as soon as anyone even picks up an Estes Alpha at the hobby store, he is already subliminally planning for his Level 3. :cool:
 
"well, if I'm gonna go that far..."
It is my personally held belief that as soon as anyone even picks up an Estes Alpha at the hobby store, he is already subliminally planning for his Level 3. :cool:

Yes... I am truly a data point in your favor. wanna hear a true kick in the ass? I spent 5 hours on OpenRocket yesterday designing my ideal L3 bird... Then I realized... I had basically created a slightly modified 5" Blue Iguana from MCR. :facepalm:

This story seems destined to be a classic. Looking forward to the rest!

Thanks!

Those fillets look awfully nice, especially with a high degree of difficulty for being done with 5-minute epoxy. A 10 from the judges! Also, I love rockets with flat paint.

Thank you! The trick is to only mix enough for one fillet at a time. lol

Also, EVERYONE loved the way that primer looked! She's glossy white now, though. Easier to see on the ground.
 
So at this point, I've Nickel-and-Dimed myself up to about $500 before motors It seemed like every time I turned around, I needed a $20 or $30 trip to lowes. One trip, however, was to a local hiking/backpacking/Rock Climbing store. I needed shock cord, and I wasn't going to settle for anything I wasn't willing to bet my life on. I walked out with 30' of 1" tubular Nylon. The kind of stuff I used to make slings for extending anchors when climbing. I'd taken 15' foot falls on this stuff, and I'd seen others take 40'+. Back at the makerspace, I stretched out the new cord and compared it to the stock one from MCR... big difference. The Chute would be a 50" parasheet from MCR. Can't remember the brand off the top of my head.

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After a final weight and balance check, everything got weighed separately, the cg of each assembly was measured, and the proper overrides were plugged into OpenRocket. She was a bit of a fat girl. 5.25lbs before motors, and I didn't care for the reality of having to put another pound of weight in the nose cone in order to balance with 4 grain motors. Alas, I made yet another trip to Walmart and I picked up a package of loctite plastic-specific epoxy, and a few bags of split-shots from the fishing dept. Returning home, I realized I hadn't bought NEAR enough fishing weights, and I decided to substitute the missing lead with some extra chain maille links I had lying around from my medieval reenactment days. The epoxy held all of the metal in like it was nothing, but I still decided to fill the nose cone with foam just to be sure.

She was balanced. Now I just had to work out what configuration I wanted to use for my cert launches.

I prepped the rocket for dual deploy, but I realized that if I was going to launch it that weekend, there just wasn't enough time to finish the sled, and get familiar with the system (Not to mention figuring out where to get ematches and black powder. I didn't know Chris Short is a true one-stop-shop, yet) I decided to work it out on the day and hope that an acquaintance, Allen Hall, who was attending SkyJam as well, would have some time to help me out.

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I had to skip the first day of SkyJam due to family stuff, but I managed to wake up at 5 to drive the four hours down there to try to find him, and hopefully get some help setting up. On the way down, I couldn't help myself. I stopped at that the "rocket rest area" on I65 and posed for a pic. The facebook post read "my rocket vs my buddy's... guess which one of us is married."

I had no electronics, but I was pretty sure I'd be just fine with motor ejection, and a JLCR I had borrowed from the SEDS club. When I got there, I managed to track down Allen, and to my surprise (and extreme gratitude) he immediately jumped into the role of mentor. Most of the rocket people I've met are pretty cool, but Allen is one-of-a-kind. If you happen to be at a launch and hear his name, find him and shake his hand, you won't regret it.

Allen, it turns out, had already been thinking about my L1 attempt. I'd been messaging him on FB casually through the week as I was building, and he knew I was going to try to make the launch, but I hadn't really asked him for anything more than a little advice. He took it upon himself to bring a used 54mm motor to use as a plug for ground testing my ejection. We spend the morning and some of the afternoon setting up the last details on the rocket, and testing the ejection. the fin can was a super tight fit for all my recovery hardware so we ended up squishing it all down, and using a technique Allen calls "Shear Taping". You tape both sections together, and you cut slits in the tape strips so they tear when the charge goes off. Technique worked so well, I used it on my L2.

Those CTI 54's come with a 2g charge, and let me tell you... It's enough. The fin can shot backward five feet and the payload section didn't stop until all 30' of shock cord were taught, and off the ground!

By the time I had the rocket ready for my cert flight on a CTI 54mm I218 drilled for 10 sec delay, the weather had turned sour, and the ceiling was down to about 1500'. In fact... it was starting to rain. The rocket was only going to 1400 on this motor in the sim, so I was confident I could stay below the clouds.

Allen and I had the same though, "DO IT".
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I ran to the flight line, and was lucky enough that the organizers hadn't completely dismantled yet. The RSO gave me the go ahead after the proper questions and whatnot, and Allen and I hustled out to the pads. We slid her onto the rail, wired her up, snapped the "last chance" pics, and got back to the control table. It took a few seconds for them to reassemble the control box, and the first launch attempt was believe to be a failure due to bad igniter, but it turned out they hadn't plugged the control box antenna back in.

The rain was picking up slightly... here's what happened next.

[video]https://www.facebook.com/nathan.krupla.1/videos/1722345714516266/[/video]

She arced over well below the clouds, and the CTI delay grain burned way long (Allen anticipated that). The charge eventually popped and the Jolly logic did its job splendidly. just before touchdown, the rocket clothes-lined on the irigation system for the field, but slid to the ground all on its own. Those spectating would later tell me that the launch had a flair for the dramatic all its own. From the weather to dodgy ejection delay to the irrigation hang-up (and not to mention the way I holler. XD.). A minute later, I was standing over it, inspecting for damage. Nothing as far as I could see. Grinning from ear to ear, I picked it up and dashed back to the pits to cover it with a plastic sheet I'd brought. Allen still says he thought it was cool that we pulled off a cert flight in the rain. :).

Allen and I packed our gear hurriedly as the rain picked up, and we waited to do the inspection / paperwork until the plastic wrapped rocket was the only thing left to stow. He agreed with my initial inspection, and the papers were signed. I drove the four hours home glowing.

A week after opening the kit, I had my L1, and to be real, if the weather had held, I would have gotten L2. But that's the last chapter of the Saga... and It'll have to wait for the morning.
 

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Congrats! 5 lbs is a pretty heavy L1. (I did it too.) What motor did you use?


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I218. Great motor. (That’s what I get for perusing TRF first thing in the morning without my glasses.)


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Alright, I'm tired of the story time format. lol

Pad weight for L1 was 8lbs-ish.

in between L1 and L2, I dropped the payload section and put a massive dent in the tube, so it had to be cut down. The rocket is now a couple inches shorter than a stock Super DX3.

I put on another two coats of primer, sanded, and applied 3 coats of Rustoleum glossy white enamel.

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I can't get these photos to rotate to save my life...

Two weeks after my L1, I swung by Allen's house to take the L2 exam, and continued south to Andalusia for the night. I rolled into SEARS to find clear skys and friendly faces. Chris Short supplied me with an Aerotech DMS J250, and I prepped for an expected apogee of around 3000ft.

[video]https://www.facebook.com/nathan.krupla.1/videos/1736119256472245/[/video]

This rocket seems to have an affinity for water. The payload section came down in an Irrigation ditch, and the JL CR got soaked (still works but needs testing). The coupler was soaked in CA so the water didn't do any damage there, and the enamel kept the tube from soaking though on the outside. The tape band from the shear tape had sealed the end of the payload section attached to the coupler, and the nose cone was screwed on with a tight enough fit that only a few drops of water got inside. Definitely dodged a bullet. she was dry by the time I got back to the RSO table to have it inspected again. For the life of me I can't remember the name of the guy who was doing the practical part of my cert. Nice enough guy, I'm just an airhead who can't remember. lol

The paperwork was signed, SoI packed up to head home and nurse my Sun Burn.

And that's the story so far...
 
Congrats! With two water landings you have a good basis for rocket-naming inspiration. I got my L2 on a rocket I call Swamp Thing based on pre-cert flights :facepalm:
 
It's name is 'Falcon Not-So-Heavy'

The name came from a kid in the makerspace here at Tech. He was walking out the door when he said it but he stopped dead in his tracks when he saw my reaction. The Falcon heavy launch had just happened the week before, and I just couldn't pass it up. lol.

Maybe the draw towards we conditions is fitting seeing as how the real Falcon Heavy's core booster didn't land on the drone ship?:confused2:
 
So.... I weighted the Nose Cone for 4 grain motors... what do you guys think is the highest thrust she could survive? Just curious...

Also possibly thinking about stripping fin can and doing t2t.

Somebody talk me down off the ledge, please. XD
 
Sure....continue to fly this, as it was intended...A simple sport flier! Add the electronics, fly the crap out of it, have fun & gain experience with dual deploy.

All the while, watching around you, for what other fliers are sending up that catches your eye.
My personal favorite is a 3in. fiberglass rocket..with a 54mm hole. [1/8in. thick G-10 fins]
Every one should have this size in their fleet.
You can now fly just about all 38's and 54's ...I's through honk'n L's

Now you got something , you can spank the crap with & not worry about coming apart at Mach-2.5
That should keep ya busy till your L-3.
No point in wasting all that time & effort, revamping a perfectly good rocket, so you can spank it,just build another designed for "spanking"....LOL
You pick the kit that tickle's your fancy.

I'm partial to one of these:
https://www.rocketryforum.com/showthread.php?120615-CJ-s-quot-PUNISHER-quot-build!
which I designed.
DSCN3632.jpg DSCN3696.jpg

or:

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Sticky at the top of this [high power]
https://www.rocketryforum.com/showt...DARKSTAR-3-OR-ANY-GLASS-KIT-BUILD-quot-STARTS

I happen to fancy these 2. Punisher is small compact, easy to store and travel. Will go to a mile [5,000 + ft] on 2 grain 54's..... and 17,000ft M-2 with L size 54's


Congratulations on you double certs!
Have fun and build light = go fast & high!
Fiberglass=takes a lick'n & keeps on tick'n! :smile:
 
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