Madcow Super DX3 cardboard and plywood kit 38mm mmt.

[GalantVR41062]

I picked this up last fall and have been slowly working on it. I have learned a lot over the last year getting into high power rockets. I plan to try and get my L2 with this rocket setup with full dual deployment.

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It is held together with a lot of TB2 wood glue, some JB 5min epoxy, JB weld, fixit epoxy, and Rocketpoxy.

It is a standard Super DX3 kit, I added a 1/4" of 4" body tube to the nose cone to help with the fitment from the nose cone to body tube. I added a baffle in the payload tube 3" up from the ebay to help hold the 70" topflight main chute off the ejection charges. I have 3 centering rings on the MMT and added material to the fins and extended the fin slots in the air frame.

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I am using 3 screws to hold the payload tube onto the ebay, and 2x 2-56 nylon sheer pins in the nose cone. I will use 1.4 grams of FFFg black powder for both main events fired by both altimeters.

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I have the Ebay a slip fit into the booster tube and added a little tape and a vent hole to the booster tube to help slow the event down as it maxed out the shock cord during ground testing with 1 gram of FFFg black powder.

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wood glue first then a internal and external fin fillets with Rocketpoxy.

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I picked up a sewing awl and have been working on recovery harnesses with 3/8" tubular Kevlar and 9/16" tubular nylon and a 1500lb swivel and SS quick links. I welded up the eyebolts and braced the ebay lids with a small strap of aluminum stock to the aluminum 1/4 20 all thread rod to hold the ebay together. I made a sled out of 1/8" plywood and safety wired it to the all thread and shaved the under side of the double thick ebay lid. The conventional ebay weighed in at 1lb 10oz and the lightweight version weighs in just under 1lb with 2 lipo batteries and a Missile Works RRC2+ and a RRC3 with dual charges for drogue and main.

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I did a weight check with a Loki 38-240 motor case and a Loki H160 blue reload and its a heavy bird.

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With that in mind I picked up a Topflight 70" main chute and with the altimeters deploying it at 500/300' I hope with the 18" x type drogue it has a 45-50ft/s decent on drogue and less then 15ft/s on the main.

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Here is the L2 motor I picked up, its a Loki 38-740 motor with a J320R reload should keep it subsonic and about 4,000'. I plan to make my L2 attempt August 11 2018 up in North Branch MN with the Tripoli high power club.

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All painted, I polished it and smoothed it out the best I can. it has rail buttons and a aeropack screw on retainer. The center of pressure is marked on the tube and should be stable with the J motor loaded up, the main being 9oz by it self and in the payload bay helps get that center of gravity up.

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I am studying for the test also, thanks for looking.

~John

 

[crossfire]

You have done a nice job. You might want a tracker in it for the L2 flight.

 

[GalantVR41062]

Yes our local club requires one in any rocket going over 3000' I think it is. They have trackers on hand to use, it looks something like this:
https://www.mikesfalconry.com/R-400A-216-219Mhz-Telemetry-Receiver-with-folding-p/2030.htm

I picked up some premaid ematches for the ejection charges as a few I dipped in H3 failed to light. I also bought a premaid ignitor for the motor as Loki reloads do not come with one.

 

[blackjack2564]

You have one of the best L-2 projects I've seen in a loooooong....looooong time.
Well thought out & executed, you should do very well.
Good luck & have fun!

 

[Bat-mite]

Make sure to get video and flights stats, and we'll be here to cheer your victory! With such a nice rocket, make sure you pass the written test!

 

[dr wogz]

I also think you've done an amazing job. I too have done my L2 on a MC Super DX3. (Aerotech j350W, is typically about 5lbs all in)

But I feel you've over built / engineered a few things:

Adding the extra tab portion to the fins. you're relying on a 1/4" butt joint, and at the point where it meets the BT. [potentially weak point for little gain] These fins are trapezoidal, don't stock out or hang off the BT, and don't see much force or shock when landing. And unless you intend to push this thing, you won't be reaching excessive forces or stress..

and, I'm not a fan of rocketpoxy. seesm overly goopy & messy..

You've used eye bolts in your bulkheads for cord attachment. and although they are welded, a single point attachment can twist enough to come undone (unscrew). I would at lease ensure loc-tite or better, a jam nut as well as loc-tite to ensure they don't unscrew.

If I recall, the av bay bulkheads are 2 pieces of 1/4" ply. It'll take a lot of force to rip a 1/4" bolt & nut thru that.. The added 1/4" Al bar stock is just added weight (although negligible)..

The nomex blankets shouldn't be free=floating on the shock cords. they can rise up & foul the chutes. I usually tie them off near the lower attachment point.

Deepened on nose weight, I try to get away form the threaded eye bolt in a NC. Cut two holes in the base of the tNC, and tie off the Shock cord thru those two holes (and one hole is usually used to add nose weight anyways!)

if you can, add a 1/4" of coupler to the inside bottom end of the rocket, the exposed 1/4" or so of BT at the very aft end tends to get dinged & bent from landings. Mine is fairly bashed in form numerous flights..

Heat shrink on your cord connections, love it, do the same myself!

But, you've done a wonderful job, and I wish you many a great flight with it!!

 

[pendrin2020]

SuperDx3 is a really wonderful kit! I got L1 and L2 in the space of a few weeks with mine last spring.

https://www.rocketryforum.com/threads/l1-l2-super-dx3-build-after-the-fact.145067/

My bird, with a 54mm J250 DMS motor weighed in around 8 lbs (I weighted the nose for 4 grain 54mm motors).

She's a fat girl when you start overbuilding her. I went so far as to fiberglass the interior of the fin can. Even so, 70" is a really massive chute. During my L2, mine came down super slow with a 56" chute.
In fact, I wish I'd set the JLCR to lower than 700. I had to hike to get it out of an irrigation ditch. Somehow, there was no water damage.

I see a lot of things in those photos that are important milestones in the hobby. I think everyone has that first one that they WAAAAAY overbuilt, but it's not a bad thing because they learned so much from actually building it. Beautiful job with yours.

My only suggestion, had I been looking over your shoulder as you built it, would have been to go ahead and peel the outer skin off of the motor tube. Once you do, adhesives can saturate right into the outer layers and the bond becomes significantly stronger. It's one of those neat tricks that will allow you to build ultra light in the future without losing strength.

That tip might not help you much, though. LOL, once I added up everything that I spent strengthening and upgrading my "paper bargain", I realized I could have just bought a fiberglass kit with all the bells and whistles, paid less overall, and had a rocket that was WAAAAAAY more durable in storage.

If the flights don't kill it, hangar rash will. ;-)

Good luck to you, sir!

 

[GalantVR41062]

One final check in with updates and final process for my L2 attempt tomorrow, studying to pass the test also. Over all height: 68 5/8" CP: 48 3/16" CG with J320r motor: 44 3/16" All up weight:7.45lbs, est decent: drogue 40-50ft/s, main decent <15ft/s.
Thrust curve puts flight specs at: max altitude 4000', max velocity 667ft/s, guide velocity 76.7ft/s, apogee time 14.6sec, opt delay 12sec.

Here is a quick run down on my packing plan for the flight. I will be flying it in the morning on a Loki H160 blue motor for a final all up check, full dual deploy test and final decent rates drogue and main, and altitude prediction on the larger Loki J320r motor.. Then test, then prep/attempt L2.

I took some advice and made a few minor changes. I did a simple stitch to hold the 12" square Nomex pads onto the shock cords, I have a big fender washer on the inside of the nose cone and the main is on the quick link for the shock cord so the nose cone should not have stress on it. and the ebay has 1/4" thick bulkhead on top and stock is supposed to be a double think with a centering bulk head inside the coupler on the bottom. I glued the 2 together and used a lathe to remove all but a 3/16" ring to center it, and a 1/8"x3/8" aluminum strap to bridge the all thread. I used a nut on both sides of the ebay bulk heads, made sure the eye lit bolt was good and tight with CA glue all over, the upper nut is pulled into the ply wood to help prevent twisting. I will keep an eye on this and switch to u bolts later.

I also added some scripture to the booster section: Job 9:9 and Job 26:7 a final coat of clear and buffed/waxed it. I will be taking as many pics and video as I can tomorrow, my phone, video from the ground by the launch pad and post flight data from the on board electronics and Jolly logic 3 altimeter. I will also be doing a L1/L2 video and post it up to YouTube.

~John

 

[GalantVR41062]

Update from Saturday, I showed up with a car full of stuff and setup my command center on the back of the car. Decided to take the test first and passed. Then to prep the rocket for a test flight on the Loki H160 blue.

Prep took time but I am feeling more comfortable and getting a process down for packing and all the things to do for DD.

Then off for inspection, going over the rocket with the RSO then off to the pad. Slid on the rail, armed the rrc3 and rrc2+ linked to the JL3, then vertical and ignitor install. Check ground camera and then back to the croud and waited. This is the time when I felt like hey did I attach the main to the quick link, I did the check list I am good.

Launch was perfect straight up 917' all 5 charges and main out at 500'. Drouge decent 45ft/s and 11ft/s on main, that perfect vertical slow decent I was hoping for.

Now it's getting a little late in the day but time to reset and go for the L2 flight. Loaded everything up with the Loki J320r un drilled delay, rocket hunter in the nose cone and headed back to the rso.

On the pad arm the rrc3/2+ then try for the JL3 and realize I forgot to turn it back on after charging it, the first and only hickup of the cert attempt I hope. Vertical then install the ignitor check the ground camera back to the dwindling croud. Wait again thinking what else I could have missed, again went down the checklist.

After some more waiting hit the go button and puff but no ignition. I only brought 1 ignitor so I bought another and installed, same thing puff no ignition. Definition of insanity.

At this point I almost called off the launch saying I can take a hint. But the rso spoke up and pulled out a home made ignitor that looked like a small beehive and he said we are going to get this red motor to light.

So one final trip to the pad, waiver time dwindling still heard all the beeps on the electronics glad for the lipo 7.4v battery's.

Back to the few people left for the day, then the count down and ignition, the red flame thrusting the rocket up straight and true. 2.6 seconds later it's still straight up into the blue sky and climbing.

A little later I see and hear the apogee events and the rso had eyes on it with binoculars, 4000' up everything looking good, the rocket doing a slow spin on it's flat decent.

500' the huge red main pops out and the hole thing falls in line for it's slow soft landing just inside the bean feild.

I ran out grabbed everything, looked great, shut off electronics and headed back to the rso. Thanking everyone for the help and encouragement, and the ignitor that did the job. L2 passed on a day when I saw a fair share of L1 struggles and a L2 cert flight break the fins off with a aerotech J270w.

I will get some pictures and video plus data from the rrc3 soon and post it up.

~John

 

[kuririn]

Awesome! Congratulations on a successful L2 flight.

 

[BDB]

Congrats on two great flights!

 

[Flyfalcons]

Outstanding writeup! Congrats, John!

 

[GalantVR41062]

I have ordered a USB IO from Missile works to get the data off the rrc3 as I can not get the Bluetooth dongle to work.

Data is looking good so far though. Rrc3 beeped out 3997', the rrc2 flashed out 4000' and the micro peak altimeter reported 1222.7m/4011'.

The ground camera shows it did one full revolution off the pad and straightened out as it gained altitude.



Thank you, this was done with Tripoli in North Branch Mn at the flying field, sod farm.
~John

 

[Kallahan11]

Congrats on Level 2 man, I did mine on a dual deploy modified Super DX3 as well.

 

[crossfire]

Great job on your L2 flight. Where is the launch site?

 

[MikeyDSlagle]

Great job on the build and flight. Looks great.

 

[Bat-mite]

Well done. Enjoy level 2!

 

[Nytrunner]

Good show!

I wonder about the fins that let loose on the J270 flight

 

[GalantVR41062]

I have not had time to get my cert videos, pics, data etc together and up on YouTube but here is the raw video from my phone.



~John

 

[Spicer007]

Very nice flight, congratulations on your L2 certification...

 

[GalantVR41062]

I added the option on having the MW T3 gps tracker in the eBay of the DX3.

I also installed the smaller main chute, and am planning on flying this tomorrow up in North Branch if the launch is a go. As for motors I am leaning towards picking up some CTI 38mm hardware. The J530 would put this up 5200' and stay subsonic, or J394.

I did get the data off the rrc3 and will be working a big video of my L0-L1-L2 jouney.

~John

 

[jlnel]

Congratulations!

 

[Banzai88]

APE and MAC both make excellent kits to put a tracker bay in yoru nose cone. Might help avoid some issues with your tracker, as it'll get it away from any metal interference.

 

[Handeman]

Congrats on the L2!

What rocket are you planning for a 54mm MMT so you can play with those Ks and baby Ls?

 

[GalantVR41062]

Light wind but heavy low cloud cover for the day. Flew the Dx3 on a AT H242T, trying to keep it under that 750' limit. Thrust curve was showing 850' but I was thinking it would do 800ish and that's want it did, rrc2+ showed 793' and the rrc3 beeped out 800'.

I changed the rrc3 to +2 sec apogee and main @400'. I decided to only put charges on the rrc3 and run the rrc2+ just for altitude.

It was a great flight, arcing into the wind a little and landed less then 100' from the pad. The 50" TFR chute I put in was about 18'/s decent and looked good.

Now to prep and fly low power over this winter. Lead Sled will fly in spring on a big J or Loki K627r. I have a MC 2.2" MD Tomach and a 4" MC Frenzy with a 54mmt and tail cone retainer that I am building along with some GPS tracking(MW T3) and low power direct staging and more complex staging with a PET2 event timer.

~John

 

[Bill Hanson]

Good choice! I got my L1 (single deploy) and my L2 (dual deploy) one month apart with this airframe. H123 and J420, respectively.
Love your paint job -- much more creative than mine.
Bill H

 

[GalantVR41062]

Making a few changes to the MC super DX3 I flew last summer for my L2.

I removed the single eye bolts on the eBay and replaced then with U bolts. I also changed the sled and electronics. It will fly with a ARTS2 and MW RRC2+ with some rotary switches and lipo 2s battery's. I have the ARTS2 set to deploy the drouge at apogee, and the main at 400' with logging at 200hz. Motor eject will not be used and the RRC2+ will be backup at +1sec drouge and main @ 300'.

I also took the base of the nose one off and am making a 38mm tube bay with a 1/4" plywood centering ring. This is where I can install the MW T3 GPS tracker and use my phone and Bluetooth GPS for live data and tracking.

I will be flying it on a 38mm CTI J530 IMAX, I am going to use a loaner case from my local club. Any tips for flying this motor or just a hope and a prayer?

Things I thought of: dip the emach in some H3 compound, use a lot grease on the o rings and epoxy the nozzle and delay grain into the liner (just above the orings).

Flight profile looks good: max altitude: 5250', velocity 830ft/sec, delay 14sec, guide velocity 90ft/sec.

This will be the highest and fastest to date for me.

~John

 

[blueapplepaste]

Looks great! Hope you don't mind me hi-jacking your thread. I'm about to start a Super DX3 and the centering rings are super loose on the MMT. Loose enough that I can't dry fit them without them just sliding down the tube on their own due to gravity.

Were yours this way (or anyone else with DX3/Mad Cow kits have this experience)?

I spoke to Mad Cow and discovered they included the wrong MMT in my kit, so they thought that was issue. But new one is just as loose.

 

[roytyson]

Looks great! Hope you don't mind me hi-jacking your thread. I'm about to start a Super DX3 and the centering rings are super loose on the MMT. Loose enough that I can't dry fit them without them just sliding down the tube on their own due to gravity.

Were yours this way (or anyone else with DX3/Mad Cow kits have this experience)?

I spoke to Mad Cow and discovered they included the wrong MMT in my kit, so they thought that was issue. But new one is just as loose.

Mine was like that. I just slathered Rocketpoxy on slid them into place and secured them with tape until it dried. The pit a ring of nice fillets top and bottom. Good to go.

 

[Banzai88]

Not an uncommon issue (especially bad with NCR kits). As Roy noted, just slather on the glue and use tape to hold things where you want them.