G117 to F51 Two-Stage

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Feb 5, 2015
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Assembly almost complete. Needed for completion: Avionics carriage for the payload section and narrow Rocket Poxy fillets. Paint after all ground tests.

Looks good. I'm building something similar right now. What avionics system are you going to use for staging?
View attachment TWINSTAR.ork

From a previous post prior to assembly:


For the OR Gurus:

I think I may have reached a limitation in the program (OpenRocket) as the graph in the simulation plot shows booster separation occurring after second stage ignition and I can find no function within the program to adjust this parameter, only the second stage ignition parameter is adjustable. What am I doing wrong?
Raven 3, my homemade GPS, an MATEK PDB and electronic tilt inhibition system using an Arduino Nano with a 9DoF IMU from Adafruit.
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Click on the Booster, select Edit, and there's a Separation tab that you can use to change the separation point. It's fun to play with, along with the delay before sustainer ignition.
Click on the Booster, select Edit, and there's a Separation tab that you can use to change the separation point. It's fun to play with, along with the delay before sustainer ignition.

Thank you, kind sir.
Nice project! Looks like a straight-forward construction for the 3 carbon rods lining up with the second stage sleeves. Those are carbon rods? I see a clear transition section for the first stage/second stage connection, but then in later pictures the transition section looks like carbon fiber. Why is there a difference?
Thanks! It has been a fun project! The carbon rods are 6mm and 8mm from amazon or ebay, I don't remember. The 6mm OD rod fits perfectly within the 8mm OD rod with no sanding or modification. I don't even need graphite. The tolerance is just tight enough to allow the rods to slide easily with no play.

It was a bit of a task to assemble and line everything up. The aeropoxy I used has a good pot life which made life a little easier during this process. Keeping everything aligned and concentric was a task that began with the construction of the sustainer motor mount. It was critical to ensure that the 8mm motor mount rods were properly aligned axially or the transition rods would be off and bind during separation. The other error would be that concentricity would suffer and the two vehicles would not be aligned axially. It turned out well. Maybe I just got lucky, but as far as I can tell any which way I look at it or roll it, they look to be inline when mated.

The plastic transition is a flimsy piece of crap from apogee. I reinforced the inside with 2x2 carbon twill and laminating aeropoxy. I lightly sanded the inside with 80 grit and layered strips of carbon. The resultant transition is surprisingly strong and concentric. I then cut the top off and built the rest of the transition (coupler, rods, bulkheads, etc.). The void inside the transition will work perfectly as the chamber for the separation charge. No centering rings were used in the sustainer, so I had to seal the spaces between the rods and fins with epoxy.

I used leftover 8mm rod for sustainer conduit which worked out well. I'm working on the electronics as we speak and will have it in primer soon. Can't wait to get this up in the air!
Any pictures/info/link/update on your project?

I finally found some time to work on my 2-stage projects while waiting for a good day to paint my L2 rocket.

Like you, I decided to try electronic staging in the MPR realm before upgrading to HPR. Here is my Magnum sustainer (24 mm MMT) and the booster (29 mm MMT) at the primer/Bondo stage. Hopefully it will fly on July 15 with MMMSC in Berwick, ME.

ImageUploadedByRocketry Forum1498427802.944121.jpg

I'm planning to fly it first with one Eggtimer quantum in the sustainer. If all goes well, I'll add another Quantum to the ISC of the booster for deployment and, eventually, a stage separation charge. After that, the techniques will be applied to a 3" to 54 mm 2-stage FG Punisher-inspired HPR rocket. I'm going to start working on that booster tonight (because my wife and kids are out of town).
Looks great Doofenshmirtz! I'm curious about your ISC. Do you have any close-ups? Is it a sealed chamber? Are you separating with motor ignition? As a personal preference, I'm not satisfied with using a coupler in the booster and sleeving into the sustainer. Although probably sufficient for LPR and most MPR the idea just doesn't seem robust enough to me. I tend to over-engineer things though. Thus my carbon rod idea. There is no perceptible slack or play between my stages when coupled, and there is just enough friction to keep the stages together even when applying the shake test with the two vehicles connected. I got lucky somehow (through slight misalignment, I imagine) that the coupler actually snaps into place when coupled, holds tightly when manipulated, and separates freely with a force equal to what I am guessing will be a small pyro charge. I have yet to do any ground testing.
Thanks, Ren and/or Stimpy! My ISC is pretty simple. It's a BT70 to BT60 transition, a few inches of BT70, a BT70 coupler and two homemade plywood bulkheads.

ImageUploadedByRocketry Forum1498439105.589961.jpg
ImageUploadedByRocketry Forum1498439114.737732.jpg

I still need to inset a screw eye into the lower bulkhead and attach the harness. For the maiden flight, I'm just going to use motor ejection for the booster, but after that, I'll install another Quantum in the ISC and attach a charge well.

You bring up a good point about the strength of the ISC. I really like your carbon rod idea. I've considered reinforcing my transition with an internal FG wrap, but it will probably be ok for the motors I'm considering for this rocket. My daughter had the same transition in one of her rockets that has flown on a cluster of 2 x E30.

For now, I'm hoping to just keep everything below 2k', so I can see the systems working. When I upgrade to HPR staging, the ISC will be made of FG coupler tubes and CRs, so everything will be much stronger. Then it will be time to start pushing the limits.
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Very nice! So you are drag separating? Did you purchase the transition or fab it yourself? Care to share your rocksim file?
Very nice! So you are drag separating? Did you purchase the transition or fab it yourself? Care to share your rocksim file?

Drag separation should cause separation for the first flight. If not, sustainer ignition will definitely do the trick. I'll try to use a charge on subsequent flights that are more complex.

For some reason, I can't upload the .ork file tonight, but here is an old file that I uploaded to a different thread:
Screen Shot 2017-06-09 at 2.43.10 PM.jpg
View attachment Magnum (electronic staging).ork

How are you planning to break the wire between your sustainer igniter and your AV bay? Someone on a different thread suggested Dean connectors. I've never used them before, so I may use loose-fitting JST or XT60 connectors, but I'm definitely open to suggestions.
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