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Hans's Mega Magg Build of Confusion

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bobbyg23

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No photo updates today, not enough time, trying to get things polished up for Saturday.

I now have five of the six 29mm tubes all finished and ready for flying. I just need to make a retainer for the altimeter mount on the 6th one. I had been struggling to come up with an idea that was simple and effective... and I just figured it out mid-sentence while typing this update. So I should hopefully have that done tonight.

I've got everything finished for the shear pins now too. I'm going with three 2-56's. I'm only worried about drag separation in this case, otherwise I would have upsized them if I was doing a proper dual deploy. The nose IS pretty heavy after all. Since it's a heavy walled cardboard rocket I opted to stiffen the areas around the pins by soaking with CA. Given how thick the plastic walls of the nose cone are, I think it should create a good shear to break the pins easily.

Recovery gear only needs to be shifted around a bit which will take me about 5 minutes, I also have a swivel that needs to get installed.

The last big thing is that I need to calibrate the new Raven and work up a pre-flight checklist for this rocket. After a few dumb moments this year I've decided each of my high-power rockets will get a checklist to make sure I do silly things like turn on the altimeters. Oh yeah, and I need to make sure I'm properly venting the altimeter to the outside. A bit tricky with the MMAS setup but not terrible. Just means more holes in the right places.

Other than that I'm ready for my charge tests, and if those go well it's ready to fly in three days.

-Hans
Can't wait to see it fly on Saturday!
 

crossfire

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I have 5 flights on my Warlock all flight were motor ejection. So fa I am 5 for 5 on deployment 3 flights were useing JLCR.
 

HHaase

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Charge test today. 45 grains of FFg, 3x 2-56 shear pins. Lays out just perfect. A few more things to sort out still but this was the biggest of the remaining list of items.

 

HHaase

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Up and away with a CTI 3grain J355 redline. Hit just over 2700ft. About 10% shy of sim estimates. I love this deployment bag, I'm going to buy more of this chute setup in the future.

I did have some altimeter issues during pre-flight so I flew it on a motor charge and only used the altimeter for data recording. Other than a few bonus seconds on the delay, the flight itself went quite nicely. Easy recovery with only a bit of scuffed paint. This rocket is a blast to fly. With my current avionics installation it's also a serious pain in the ass to prep for electronic deployment. I need to work on improving that and have a few things I'm already looking into.

-Hans



mmagg-0032.JPG
 

HHaase

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So I did have one major anomaly that I didn’t like, and I’m still digging into the cause. I had both of the altimeter charges deploy on the pad when I was finalizing the prep for launch. I haven’t found a cause yet. Thankfully I opted to leave the positive wire for charges disconnected until the last moment, and did the final connection externally. I connected the charges, got good continuity beeps from the altimeter, and let it sit for about 30 seconds. Things seemed fine. As I was feeding the wires into the airframe I had both charges go off simultaneously. Other than being very surprised, and the big obvious paint scrape on the nose, everything and everybody were just fine.

I'm still investigating what happened, and I'm going to drastically change how I handle my altimeter mounting and prep sequence going forward. Right now all I know for sure is the wiring was connected properly. I'm still checking altimeter data and programming to see if something may have caused it in there. Somewhere along the line I either assembled something wrong, programmed something wrong, or misunderstood something in the sequence. Until I understand what happened I'm going to stop flying electronic deployment. Something in my system design or procedures allowed this to happen. I don't want a repeat.

The only thing I'll say conclusively is that the safety checks and balances I had on my checklist kept me safe. Never get lax on safety.
 

HHaase

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Here's the checklist that I used yesterday morning for this particular launch. The first couple sections I did the day before, the rest were done at the field. This rocket is probably overly complex but I'm trying to build up my knowledge base for an eventual run at L3 in a couple years.
 

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bobbyg23

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It was a great flight. The bonus seconds on the delay had us all a bit worried!.
IMG_3397 resize.JPG
 

HHaase

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Ok, time for some 'lessons learned' on this build and this flight. It flew great and there are a number of things I really liked about this build. But there were some things that proved far too cumbersome in practice. This rocket is going to be a paradigm shift in my design theory for sure.

Because of the incident with the deployment charges I'm going to be a lot more critical here than usual. I cannot allow that to occur again. So prepare for a very wordy 'after action review'.......

The Good:
1: This rocket flies beautiful. I love LOC kits. I'm going to buy more LOC kits. I've already picked my next LOC kit (Hint: It's bigger).
2: Super happy with the Rocketman recovery gear. I had some 'bonus seconds' on the delay, and it deployed at speed, but zero issues with recovery.
3: Much love for deployment bags. I'm going to use them going forward for all my higher performance builds.
4: This is the first time I'm actually completely content with the entire recovery train to be honest. All my previous builds something always irked me.
5: My Eggfinder is now working. I forgot my longer antenna, so range was reduced, but the electronics in the system worked just fine without issue.
6: 2nd rocket in a row that I've used PETG printed charge wells. Zero issues at all with them. I'll continue to do this.
7: The checklist was huge for me. As my rockets increase in complexity these will become more critical.
8: Safety rules = the win! Things could have been very bad when my charges went off. Establishing and following the safety rules kept me from getting hurt.

The neutral:
1: My experiment using the MMAS tubes for electronics did work, but in some areas was cumbersome. I won't be completely using this method again in the same way, but there are some elements that I may re-use in future builds. Much of this was due to limitations of the 29mm tubes I was using.
2: I need to consider multiple styles of rail buttons, to make sure I'm compatible with different rails. We had 1010 rails, and I had 1515 buttons. Had to swap to fly.

The ugly:
1: Something in my altimeter system design allowed the charges to go off while on the pad. This is a safety critical flaw that I need to address.
2: On closer review, I need to really work on improving my altimeter and avionics mounting theory. Everything worked on this build, but the concepts I used are best meant for smaller diameter rockets with limited access. Larger airframes like this one need a completely different methodology.
3: Wires suck for this kind of situation. I need to reduce and eliminate wiring as much as possible going forward.
4: I'm going to start eliminating the Featherweight magnetic switches from my designs. The more I use them the less I like them.
5: Truth be told, my confidence in the Raven design is a bit shaken too.
6: I'm at the point I need to start doing multiple redundant altimeters. Already working on this.
 

DMehalko

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Nice review, did you get your decent rates with the 6‘ rocketman? It looked a smidge on the fast side still?
 

HHaase

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Definitely a bit quicker than I anticipated, looks like it averaged 35fps under the chute going by the altimeter data.
Oddly enough the Raven FIP software doesn't plot out descent rates. So I had to extrapolate that from the altitude graph.

Also looks like my delay was 20 seconds! I thought I had drilled it for 15, and the advertised full-time delay on that motor is 17. A bit concerning. I need to get the altimeter working properly.

-Hans
 

Crazyrocket

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Quick question as I did not see it in the thread anyway (or maybe I just missed it). How did you set up your deployment bag? Did you eject it at apogee and let the drogue pull it off it some other method?
 

HHaase

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Essentially, yes. I picked up one of the deployment bags with integrated drogue, and just had it all deploy at apogee.

I was going to try reefing it with my chute release but at the speed things were going at deployment, that method didn't work out.

-Hans
 

Crazyrocket

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Thanks for the info! I need to try d-bag sometime. Most of my rockets are 4" so probably not really needed.
 
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