Astrorizzicist - My attempt at a mostly 3D printed L2 capable rocket

[INFX_TryHard]

Intro​

I am sharing my progress on a mostly 3D-printed rocket design I started in March of this year. I started the design after losing my first level 2 attempt to the field. The overall goal of this project is to use this for my level 2 flight eventually, and possibly a 2-stage flight in the future depending on how everything continues to hold up. As of now, I just launched this past weekend on an H550 DMS as the test flight for this rocket, it weathercocked a decent bit but flew to 1040 ft and 270 fps. Upon drogue ejection charge, the primary charge blew a portion of the drogue bay apart, but everything recovery-wise held perfectly and someone else eventually found the two broken-off pieces later in the day. Besides a partial break, I considered this flight to be a near-complete success as my lost rocket never returned to me. Flight was in Bayboro, NC.


(Still at launch taken by club member)

Design Choices​

The overall design is a fairly simple 3" diameter, 58" long dual-deploy design with separation at the aft portion of the AV bay and separation at the nosecone. Drogue placed in the aft with main forward of AV bay with aft motor retention using a bulkhead threaded in. The design is entirely out of PLA, since I was most familiar with it, had an abundance for testing, and felt that the flight characteristics initially did not require any exotic material choices as I am also limited by my Ender 3.

Where the design starts to get interesting is how essentially everything threads together, all body tubes have a thread somewhere on them to connect. It was the easiest for me to model and test effectively, and it allowed for changing of parts when they do break or have fitment problems as I don't have to just epoxy everything together first try and hope it stays together. The nosecone and drogue aft bulkhead also thread into the airframe with the aft bulkhead being sandwiched between the end of the threads and a threaded in airframe section. The nosecone bulkhead threads in for easy removal and placement of the GPS and battery into the nosecone to separate it more from the other metal components in the AV bay. The AV bay uses a standard design with 1/4" 3D printed bulkheads with integrated steps and slots in the side to align correctly when placed. Contrary to the exploded picture below, I originally had an integrated shock cord mount but since changed to eyebolts on the advice of others. A modular motor mount system was also designed so I could easily swap from 38 and 54mm motors, I additionally used a cardboard liner on the inside of the mount. Cork and aluminum foil also lined near where the motor was near the cap of the motor mount for more protection which held up perfectly to the first flight. Two conformal 1010 rail guides were also integrated into the fin can but I later jb welded another onto the aft airframe section a week before launch connecting to the AV bay to make sure the sections lined up well with a sample 1010 rail I had access to.


(Pictured above uses some previous components that were not used due to design changes, but overall thread locations and sizes stay about the same throughout)

(OpenRocket file of the first flight on H550)

Testing and Pre-flight Adjustments​

Standing on the fins with all of my weight gave me a lot of confidence on their second iteration as the first design was way too small so I changed to a thicker airfoil design which allowed me to not have to think about fins breaking on the way up or on landing at all. The tubes also felt stronger when squeezing compared to cardboard. The coupler sections of the rocket at AV aft portion and nosecone did need substantial sanding as I haven't quite gotten the tolerances right on them, but all the threads turned out perfectly when pulling back the sides on each side by .15 mm in Fusion 360. Most of the rocket was printed at adaptive .2 mm layer height with .16 and .24 as the min and max. Since I wanted to keep this rocket low, I didn't sand any of the external surfaces so the surface was whatever my ender 3 was doing for that day, I left all the seams and most imperfections in the prints.

For ejection testing, I used the surgical tubing method mentioned in another forum post which worked a little too well for the actual flight. After my first test, neither section blew and in the video I could see some gas escaping through the threaded sections, to fix this, I applied white lithium grease to these threads and upped the charge for the next tests. This helped as I didn't see any more gas escaping through the threaded portions of the rocket.

Flight Configuration​

Recovery

• 20' of 1/4" kevlar in main and drogue
  • Main at 1/3 from nosecone
  • Drogue at 1/3 from AV bay
• 58" top flight standard main
  • 16x16" nomex (Larger than I would have preferred)
• 15" top flight standard drogue
  • 8x8" nomex (Larger than I would have preferred)
• Drogue Charge
  • 1.1 and 1.4 g FFFF bp
• Main Charge
  • 1.7 and 1.9 g FFFF bp

Electronics

• Dual Easy Minis
  • Primary at apogee and 200 m
  • Redundant at apogee +1s and 150 m
  • 160 mAh 1s from Altus Metrum for each
• Eggfinder Mini
  • 400 mAh 1s from Altus Metrum
• Twist and Tape for the switch

Future Flight/Plans​

My first flight was my second attempt at flight as 5 minutes into arriving at the field on the first attempt, I over-torqued my aft drogue bay the day before and it took a lot of force to release, when it came free, the threads on the lower section came with it too and sheared right off with a clean break. To fix this I made the connection point a lot thicker and made sure not to overtighten anything. For my second L2 attempt in January, I will be flying a J270-P in the same configuration but plan on adding an internal ribbing to the three primary airframe sections that experience ejection forces. I will also lengthen the sections by 5mm as fitment was a tad tight in the main and drogue bays with the lengthy ejection charges. I will likely change to centrifuge tubes for a much lower profile charge. A different airframe material for where the motor mount is exposed to the motor and the charges would also be wise, but I need more experience with PETG, CF PETG, and other materials before doing so. After hopefully getting my L2 for the next flight, I'd like to look into my first two-stage flight. Since I can essentially reuse the entire aft portion of the rocket, I also designed a subscale version of the rocket earlier on to help with my tolerancing and I can also just slide on top with an interstage. This is a later project that I don't have any timeline for but in the back of my mind for now.


(Fusion 360 CAD model of the updated design with internal ribbing)


(Two Stage Version)

 

[thzero]

Whats the weakest part of 3d printed part?

 

[thzero]

"The coupler sections of the rocket at AV aft portion and nosecone did need substantial sanding as I haven't quite gotten the tolerances right on them, but all the threads turned out perfectly when pulling back the sides on each side by .15 mm in Fusion 360."

Yes. I had lots of failed test prints with threads. Think I ended up with .3mm gap, and it works without sanding. However I also integrated a pin (just nylon bolt) to "lock" it in place.

 

[thzero]

PLA sucks. :|

" different airframe material for where the motor mount is exposed to the motor and the charges would also be wise, but I need more experience with PETG, CF PETG, and other materials before doing so. "

I found that Estes motors tend to burn hotter than any of the mid and low hpr power RMS casings - I haven't bothered with single use. But nonetheless I use a standard LOC tubing (or something similar) as a buffer.

Not had any issues with smaller BP dual deployment with .8 and .12 walls on smaller mid sized rockets with PETG.

https://www.rocketryforum.com/threads/3d-printed-modular-rocket.179657/
For reference.

 

[Choco_mint]

Awesome work!

Will you ever release the files for other people to download once you get it working the way you want?

My dad just got into rocketry and indicated that he wants to start going for certs after watching me get my L1 a few months ago, and he also just got a K1 Max!

He'd likely be flying it on a Cesaroni H123 to start since that's what I have already.

 

[INFX_TryHard]

Awesome work!

Will you ever release the files for other people to download once you get it working the way you want?

My dad just got into rocketry and indicated that he wants to start going for certs after watching me get my L1 a few months ago, and he also just got a K1 Max!

He'd likely be flying it on a Cesaroni H123 to start since that's what I have already.

Thanks!
Yes, I do plan on releasing files at some point, I will probably do this after my L2 attempt in late January as there are a few parts that I have slightly modified since my first launch, and I would like to test them to make sure all the files are in a print and fly configuration essentially.

 

[OzHybrid]

Have you checked with your prefect, rso and lco that they'll allow this construction method for a L2 certification flight?
From the Tripoli L2 Certification procedure available at tripoli.org under cartification then Level2

Although 3D printed fin cans are allowed, rockets that are entirely 3D printed are not.

I've not read the NAR rules. But if you are certifying, you need to understand them. It's not just about can you build a rocket, but more about can you demonstrate a skill set that makes you safe to build ANY rocket..

Of course if you are not certifying with it, go for it....

edit. Just read the NAR L2 rules. There does not seem to be anything preventing fully printing a rocket. I personally think that is wrong for an exam attempt.

It's like sending a self driving car to do your driving test.....

 

[bad_idea]

edit. Just read the NAR L2 rules. There does not seem to be anything preventing fully printing a rocket. I personally think that is wrong for an exam attempt.

It's like sending a self driving car to do your driving test.....

I can see not allowing rockets printed in their entirety in one piece, but every 3D printed rocket I've seen beyond small model rocket size has required substantially more assembly than an equivalent rocket made of traditional materials, due to limited print volume. Seems more of a handicap in that regard than an aid.

Makes me wonder what "entirely 3D printed" means in this case, i.e., is that Tripoli rule simply in place against the day when printers with a Z height of a half-meter or more become common, or does it also apply to a body tube built from 3D-printed segments? Though looking at the shortest J motor I can find (241mm ahead of the thrust ring), I suppose a 300mm Z - not all that rare anymore - could do it.

 

[OzHybrid]

When you buy a length of fiberglass tube you can reasonably know what it's going to perform structurally from the general performance characteristics of the material. You cannot do that with a printed material unless you know the printer, the material it's printed with.The print temperature, the bed temp the cooldown period. There are so many individual variables that the general result is an individual result strength wise and fdm will ALWAYS have a coil of string strength orientation While some people will produce strong prints, others do not. And it's impossible to tell the difference without destructive testing.
That's the safety issue. Allowing it for a certification flight is a really bad idea. The certification flight is the examiners opportunity to see that the builder is accross the majority of the spectrum of construction techniques. After the certification, what you launch is up to you.
Fully printed as per the TRA guidelines would be a structural element like body tube or nosecone that was printed. The decision as always whether you can launch is the rso and lco. The prefect can also not certify you. That's why checking with them all is a good idea to do before the day so your day doesn't get ruined.

 

[bad_idea]

When you buy a length of fiberglass tube you can reasonably know what it's going to perform structurally from the general performance characteristics of the material. You cannot do that with a printed material unless you know the printer, the material it's printed with.The print temperature, the bed temp the cooldown period. There are so many individual variables that the general result is an individual result strength wise and fdm will ALWAYS have a coil of string strength orientation While some people will produce strong prints, others do not. And it's impossible to tell the difference without destructive testing.

I agree with every word of this.

In your earlier statement that a 3D-printed cert rocket was like a self-driving car in a driving test however, you seemed to indicate you thought 3D-printing an entire rocket was an easy route, where in every way it seems to me a harder one, unless someone has the print volume to print an entire body with fins and motor mount (if applicable) in one piece.

* Hence - along with questionable performance for mass - why I have no interest in 3D-printed bodies for conventional shapes

That's the safety issue. Allowing it for a certification flight is a really bad idea.

If it's a safety issue on a cert flight, it's a safety issue on any flight. I do believe 3D-printed bodies and fins should attract more RSO scrutiny and questions in either case.

The certification flight is the examiners opportunity to see that the builder is accross the majority of the spectrum of construction techniques.

I don't see a cert flight as a test of every aspect of building, since there are so many different ways to build a rocket. It is a test they can build something though. If someone prints a strong, multi-piece body and assembles it securely, that tells me more about their ability to build something than if they use an off-the-rack tube. (It also makes me wonder why they'd bother, when off-the-rack tubes are better suited in most respects and a lot less work, but there's a certain mindset common to many people with 3D printers that's akin to the mindset that if all you have is a hammer, everything is a nail.)

If however someone 3D prints an entire body complete with motor mount, fins, etc., than I don't see it as something the flyer built. It might be something they designed, but it says nothing of their ability to build.

Fully printed as per the TRA guidelines would be a structural element like body tube or nosecone that was printed.

The wording for TRA L1 and L2 is "rockets that are entirely 3D printed." It doesn't mention nose cones at all, and it would cause a sea-change in certifications if it did. While still a minority, I've lost count of how many cert rockets - mostly from students - I've seen in the past few years that had 3D-printed nose cones. Starting to see a lot of 3D-printed fin cans too. I have some concerns about those on a cert rocket, but since they're allowed for L3, I guess they're not going away from L1 or L2 anytime soon.

The decision as always whether you can launch is the rso and lco. The prefect can also not certify you. That's why checking with them all is a good idea to do before the day so your day doesn't get ruined.

Certainly true, and all as it should be.

 

[OzHybrid]

Anyone could take the SCAD generators and print a rocket. There is no build documentation requirement for L2. And get NAR L2 certified. Hopefully no-one from Triloli would certify.
What I'm saying is that while there are some printing aspects that make a printed rocket more difficult, that I do not think it's appropriate for a L2 or 3 certification. I personally use 3d printing a lot. Having done that, on a strenth to weight ratio in all axes of loading, there are better material choices. Some of the better choices would involve 3d printing as a former and glassing or covering in CF over.
But the national bodies set the rules. Not me.
I just want to fly rockets. And design some bits and bobs...

 

[bad_idea]

Anyone could take the SCAD generators and print a rocket. There is no build documentation requirement for L2. And get NAR L2 certified. Hopefully no-one from Triloli would certify.
What I'm saying is that while there are some printing aspects that make a printed rocket more difficult, that I do not think it's appropriate for a L2 or 3 certification. I personally use 3d printing a lot. Having done that, on a strenth to weight ratio in all axes of loading, there are better material choices. Some of the better choices would involve 3d printing as a former and glassing or covering in CF over.
But the national bodies set the rules. Not me.
I just want to fly rockets. And design some bits and bobs...

Yes, it's a bad idea for most people to print a whole rocket for a cert flight, even if it's allowed (NAR), a worse idea if they didn't design it themselves, and it's a bad idea for anyone to stress 3D printed components too much without experience. Sufficient experience and engineering could override any of those concerns though for me though.

My own first L1 attempt failed when weakly set thermoset inserts I didn't understand how to use properly were pulled out of the ring attaching the nosecone to the tracker sled, losing the cone (but fortunately not the sled). I reworked sister parts to those that failed with epoxied steel nuts and a bunch of fiberglass, and they've flown fine since in a different rocket (though by the time I reflew my L1, I'd already replaced the 3D-printed parts with plywood in the cert rocket itself).

Edit for clarity. As with many things I'm neither 100% for or 100% against any particular approach, assuming it's done with forethought.

 

[INFX_TryHard]

@OzHybrid I agree in that much of the hobbyist 3D printing technologies today are not as strong as "conventional" model rocket building components, but I disagree with much of the rest of your argument.

I don't use 3D-printed PLA for trying to set any altitude or speed records, I made this 3D-printed rocket in an attempt to follow a non-"conventional" technique as I didn't have a wealth of extra body tubes and parts in my dorm. Having had experience with 3D printing and designing for a few years, I wanted to take on a small challenge. Even if someone were to take my files at some point to use for a certification flight, what is the difference between 3D printing ~20 components over the course of a week or two and putting them together compared to a kit sold with instructions? All you do is watch a 10-minute YouTube video and slap a bunch of 5-minute epoxy together and you have yourself a level 1/2 capable rocket within two days without any knowledge growth. I still have to figure out what print settings to use, print all of the parts, and assemble them. RSOs can still ask the same questions about "conventional" rockets as 3D printed, infill/wall settings, filament type, etc, they will give a pretty good idea about the strength of the parts.

I made the fins strong enough to where I stood on them and nothing happened, if I stood on almost any other L2 rocket from my club they would most likely break. I additionally didn't want to build an L2-specific rocket that I would most likely fly once or twice before putting up on a shelf or wall, with the 3D printed modularity I can constantly change and improve the design to fit my wants and needs for the next rocket. I vastly prefer the building and design process over the flight itself, my 4-7 months of design and building/assembly before my test flight were way more enjoyable than the flight itself due to the challenge it brought me.

For L1 and L2 flights, I have seen significantly more failures in how the recovery was completed whether it be rubber bands left on parachutes, altimeters not working, or motor ejection not working rather than issues in any part of the construction process itself. There is still so much more than just having a completed rocket. I've additionally seen many rockets put together within short periods with no surface prep before bonding, incorrect grain direction on fins, and quick links attached to the tiny 1/4" abs molded plastic loop on nosecones but they still flew before cracking or breaking off. Some of these issues can't easily be spotted easily by the RSO or remembered at all by builders after rockets get painted. Some rockets are made for the sole purpose of getting the L1/L2 and being done with rocketry as a hobby. If someone is going to print a rocket and not learn about it before flying, they are going to do it anyway with cardboard tubes and plywood found in the dumpster and mess something else up.

3D printing is a vastly growing technology that can significantly grow the hobby in more ways than can be thought of and shouldn't be disregarded for certification flights in my opinion. As 3D-printed rockets become more and more popular with more 3D printers coming into the homes of rocket enthusiasts, systems can and should be put in place to check for proper printing techniques by the RSO. After all, someone forgetting a rubber band on a parachute still isn't going to certify with or without a 3D-printed rocket.

 

[OzHybrid]

@OzHybrid I agree in that much of the hobbyist 3D printing technologies today are not as strong as "conventional" model rocket building components, but I disagree with much of the rest of your argument.

I don't use 3D-printed PLA for trying to set any altitude or speed records, I made this 3D-printed rocket in an attempt to follow a non-"conventional" technique as I didn't have a wealth of extra body tubes and parts in my dorm. Having had experience with 3D printing and designing for a few years, I wanted to take on a small challenge. Even if someone were to take my files at some point to use for a certification flight, what is the difference between 3D printing ~20 components over the course of a week or two and putting them together compared to a kit sold with instructions? All you do is watch a 10-minute YouTube video and slap a bunch of 5-minute epoxy together and you have yourself a level 1/2 capable rocket within two days without any knowledge growth. I still have to figure out what print settings to use, print all of the parts, and assemble them. RSOs can still ask the same questions about "conventional" rockets as 3D printed, infill/wall settings, filament type, etc, they will give a pretty good idea about the strength of the parts.

I made the fins strong enough to where I stood on them and nothing happened, if I stood on almost any other L2 rocket from my club they would most likely break. I additionally didn't want to build an L2-specific rocket that I would most likely fly once or twice before putting up on a shelf or wall, with the 3D printed modularity I can constantly change and improve the design to fit my wants and needs for the next rocket. I vastly prefer the building and design process over the flight itself, my 4-7 months of design and building/assembly before my test flight were way more enjoyable than the flight itself due to the challenge it brought me.

For L1 and L2 flights, I have seen significantly more failures in how the recovery was completed whether it be rubber bands left on parachutes, altimeters not working, or motor ejection not working rather than issues in any part of the construction process itself. There is still so much more than just having a completed rocket. I've additionally seen many rockets put together within short periods with no surface prep before bonding, incorrect grain direction on fins, and quick links attached to the tiny 1/4" abs molded plastic loop on nosecones but they still flew before cracking or breaking off. Some of these issues can't easily be spotted easily by the RSO or remembered at all by builders after rockets get painted. Some rockets are made for the sole purpose of getting the L1/L2 and being done with rocketry as a hobby. If someone is going to print a rocket and not learn about it before flying, they are going to do it anyway with cardboard tubes and plywood found in the dumpster and mess something else up.

3D printing is a vastly growing technology that can significantly grow the hobby in more ways than can be thought of and shouldn't be disregarded for certification flights in my opinion. As 3D-printed rockets become more and more popular with more 3D printers coming into the homes of rocket enthusiasts, systems can and should be put in place to check for proper printing techniques by the RSO. After all, someone forgetting a rubber band on a parachute still isn't going to certify with or without a 3D-printed rocket.

The difference is, Tripoli rules prohibit fully printed for a certification flight. NAR don't prohibit it. So between the organisations, they should align the rules. One way or another. Not allowing it for cert flights would be my preference for the reasons stated.
Also the failure modes you mention for conventional construction, leaving bands on chutes etc are equally applicable to any printed rocket. Including lack of surface prep for bonding.

 

[thzero]

@OzHybrid I agree in that much of the hobbyist 3D printing technologies today are not as strong as "conventional" model rocket building components, but I disagree with much of the rest of your argument.

I don't use 3D-printed PLA for trying to set any altitude or speed records, I made this 3D-printed rocket in an attempt to follow a non-"conventional" technique as I didn't have a wealth of extra body tubes and parts in my dorm. .... I still have to figure out what print settings to use, print all of the parts, and assemble them. RSOs can still ask the same questions about "conventional" rockets as 3D printed, infill/wall settings, filament type, etc, they will give a pretty good idea about the strength of the parts.

I say go for it. Certainly work with the RSO, etc. for club where you are launching. But I saw a post for Steve Shannon in the Tripoli Facebook group that the intended was fully printed OOB, but that if there was still significant construction then it didn't fall a foul of those rules.

But not really sure any internal ribbing is going to help.

I've sent my 2.6" fully 3d printed rocket up on a G64 - was find other than landing in a pond.

https://www.veed.io/view/4582c451-55d9-4c5b-8f05-09d3c9ec2c96?panel=share
I'm really kinda curious what it will do on an H128W
.

https://inverted-pursuits-lab.square.site/product/screwball/4?cp=true&sa=true&sbp=false&q=falsehas run on some Hs and a J

Although per their design file, its like 4mm thick walls. Whether correct or not, I'm not sure. Its certainly with only a parachute heavier than my fully loaded DD 2.6" rocket, but the same rough height.

 

[OzHybrid]

I say go for it. Certainly work with the RSO, etc. for club where you are launching. But I saw a post for Steve Shannon in the Tripoli Facebook group that the intended was fully printed OOB, but that if there was still significant construction then it didn't fall a foul of those rules.

But not really sure any internal ribbing is going to help.

I've sent my 2.6" fully 3d printed rocket up on a G64 - was find other than landing in a pond.

https://www.veed.io/view/4582c451-55d9-4c5b-8f05-09d3c9ec2c96?panel=share
I'm really kinda curious what it will do on an H128W
.

https://inverted-pursuits-lab.square.site/product/screwball/4?cp=true&sa=true&sbp=false&q=falsehas run on some Hs and a J

Although per their design file, its like 4mm thick walls. Whether correct or not, I'm not sure. Its certainly with only a parachute heavier than my fully loaded DD 2.6" rocket, but the same rough height.

But I saw a post for Steve Shannon in the Tripoli Facebook group that the intended was fully printed OOB

I assume you meant OOTB ( Out of the Box. )



As Steve has said many many times and is in his signature....... @Steve Shannon

Nothing I say should be assumed to be official Tripoli information unless specifically stated.
Steve Shannon
Amateur Radio AI7KS
GMRS WROM258

So unless the written rule is changed, it's open to interpretation.

 

[bad_idea]

I say go for it. Certainly work with the RSO, etc. for club where you are launching. But I saw a post for Steve Shannon in the Tripoli Facebook group that the intended was fully printed OOB, but that if there was still significant construction then it didn't fall a foul of those rules.

That would certainly be my reading of the rule in the absence of further explanation. When I see "entirely 3D printed," I think of "download these three STLs for nose, retainer cap, and body/fins/motor-mount, print them, tie them together with a shock cord and chute, and go fly," essentially printing an RTF or ARTF rocket.

I don't see a difference in constructing a rocket out of various 3D-printed pieces and constructing one out of various non-3D-printed pieces aside from the former being typically (though not necessarily) lower performing and likely being more work. Good to know that Steve said similar.

 

[thzero]

So unless the written rule is changed, it's open to interpretation.

Yes, that's what I was getting at. Whether it be nar or Tripoli or other org people should be talking to those who will be signing off on their cert

 

[thzero]

I don't see a difference in constructing a rocket out of various 3D-printed pieces and constructing one out of various non-3D-printed pieces aside from the former being typically (though not necessarily) lower performing and likely being more work.

Depends on what you mean by more work. Couple of my designs are literally twist together and few nylon bolts, plus epoxying in a motor tube.

Lot less work than through wall, etc work.

If you meant all the tinkering, cad designs, printing test pieces, etc? Then it was a heck lot more work.

And yes.. I can build same that performance is better due to lower mass. But then I gotta paint them!

 

[OzHybrid]

I assume you meant OOTB ( Out of the Box. )

View attachment 627364

As Steve has said many many times and is in his signature....... @Steve Shannon

Nothing I say should be assumed to be official Tripoli information unless specifically stated.
Steve Shannon
Amateur Radio AI7KS
GMRS WROM258

So unless the written rule is changed, it's open to interpretation.

The other other thing is, as per the Tripoli website.

https://tripoli.org/content.aspx?page_id=22&club_id=795696&module_id=520420

"As needed, the Tripoli Board of Directors (BoD) will announce updates in the Tripoli Report that shall be considered official even before a new version is published. "

While this was a clarification rather than a rule change, I'm uncertain why the only notification of it was on the facebook page.
And not in a designated place for notifications as specified. If you're going to be specific about where notifications take place, it's important to put them where you've said.

 

[JohnCoker]

Indeed, the distressing part of the 3D printing is how much equipment and obscure settings matter. I agree that additive manufacturing is the direction of the future, but for now it's hard to make general recommendations. For HPR, a lot of tuning is required to get printed parts to be as strong as those made from traditional materials.

Even without any tuning, the strength of components varies hugely by printer and material: https://www.jcrocket.com/printed-components.shtml.

 

[Handeman]

The whole point of certification flights is to certify the flier has the knowledge and skill to build a rocket that will successfully fly on the certification motor.

If that means do they know enough about cardboard or fiberglass tubes, epoxy, etc. or do they know enough about temps, infill, etc. for 3D printing is immaterial to my way of thinking. If they can build a rocket, in anyway they want, and successfully fly and recover it intact, on the certification motor, that is all that matters.

It doesn't matter if it is a light weight high performance rocket, or an overweight drag queen. If they are able to build a rocket that can successfully fly and recover, that's the requirement. Don't read more into it then there is.

 

[OverTheTop]

I'll just add a data point for 3D printed parts here. I print in ABS and have launched nosecones and transitions up to M2.14 successfully. L-O motors. 3D printing can be engineered successfully, like any other material.

 

[INFX_TryHard]

This past weekend, I completed a successful NAR L2 flight on a J270W with the 3D-printed rocket with every aspect of the rocket and my assembly going well. Reached just over 3000 ft and nearly 300 mph. There was a good bit of weathercocking after leaving the rail into the wind which I expected as winds were fairly strong most of the day and similar weathercocking happened for most other rockets flown. Landed less than a 1/4 mile away and nearly ended up in a ditch but luckily, only the tail cone got a little wet.

There were no signs of damage on any portion of the rocket and I believe this is in part due to adding an isogrid internal structure along with aluminum tape on the inside to help with heat and added thickness to regions with charges. Adding an extra 5mm to the 3 sections induced to charges also helped plenty with packing main and drogue portions. Flight configuration was the exact same as the first flight with no changes to the process. The motor retainer additionally had no problems with the longer burning J motor with no visual changes or warping present.

Overall outcome came to much more experience in the entire dual deployment process with this being my second successful dual deploy flight, realized that 3D printed parts are easily strong enough to make an effective high-power rocket, discovered some more weaknesses with my design that can be improved upon for more confidence/reliability, and had a lot of fun building/launching most importantly!

Flight completed with NC Rockets at the Bayboro Field.


(Still launch photo and video taken by club members)









View attachment -7433612530036484717vid_84600722_194417_907.MP4

 

[thzero]

Congrats!

 

[bad_idea]

Congratulations!

 

[cwbullet]

The whole point of certification flights is to certify the flier has the knowledge and skill to build a rocket that will successfully fly on the certification motor.

If that means do they know enough about cardboard or fiberglass tubes, epoxy, etc. or do they know enough about temps, infill, etc. for 3D printing is immaterial to my way of thinking. If they can build a rocket, in anyway they want, and successfully fly and recover it intact, on the certification motor, that is all that matters.

It doesn't matter if it is a light weight high performance rocket, or an overweight drag queen. If they are able to build a rocket that can successfully fly and recover, that's the requirement. Don't read more into it then there is.

Many folks that print rocket parts have more knowledge of the materials and adhesives than those that build kits. To make a quality fin can that survive high power motors, you often have to know the material and infills. Few who build with fiberglass or wood know what direction the fibers do. It can be essential to success with printing.

 

[cwbullet]

This past weekend, I completed a successful NAR L2 flight on a J270W with the 3D-printed rocket with every aspect of the rocket and my assembly going well. Reached just over 3000 ft and nearly 300 mph. There was a good bit of weathercocking after leaving the rail into the wind which I expected as winds were fairly strong most of the day and similar weathercocking happened for most other rockets flown. Landed less than a 1/4 mile away and nearly ended up in a ditch but luckily, only the tail cone got a little wet.

There were no signs of damage on any portion of the rocket and I believe this is in part due to adding an isogrid internal structure along with aluminum tape on the inside to help with heat and added thickness to regions with charges. Adding an extra 5mm to the 3 sections induced to charges also helped plenty with packing main and drogue portions. Flight configuration was the exact same as the first flight with no changes to the process. The motor retainer additionally had no problems with the longer burning J motor with no visual changes or warping present.

Overall outcome came to much more experience in the entire dual deployment process with this being my second successful dual deploy flight, realized that 3D printed parts are easily strong enough to make an effective high-power rocket, discovered some more weaknesses with my design that can be improved upon for more confidence/reliability, and had a lot of fun building/launching most importantly!

Flight completed with NC Rockets at the Bayboro Field.
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(Still launch photo and video taken by club members)




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Congrats.

 

[Flare]

My opinion, which may not carry much weight as a younger rocketeer, is that there shouldn't be any restrictions on 3D printed rockets for cert flights. It's been demonstrated now countless times that 3d printing can be used on rockets of this scale (and above). Many of the arguments I've seen in favour of restricting 3D printed rockets give off vibes of an old man saying "get off my lawn, kids". Sure, you can do a poor job building a 3D printed rocket, but it's just as easy to do a poor job building a cardboard and wood rocket. I'm sure most people have seen structural failures of all sorts from inexperienced builders even using traditional techniques.

I personally have never built a fully 3D printed rocket and have no plans to do so, mainly because they are heavy and I just love building my own composite parts. But I have flown rockets with 3D printed structural parts like bulkheads and nosecones no problem. It's very useful in rocketry and I admire people doing fully 3D printed rockets. It requires a different set of design skills but it has some incredible advantages too. You can do things like airfoiled and tapered fins which is almost impossible with traditional composite or wood techniques.

In any case, great job by TryHard on the L2 cert. (Did mine on the same motor!) Big fan of normalizing 3D printed rockets too. They work. Just gotta convince the old folks.

 

[thzero]

I agree and disagree. I think what was done here is totally within the spirit of it and really is no different, and actually more work, than someone picking up a Fiberglass kit from a vendor and building it when they've only built cardboard before.

I think where I disagree is when someone just pulls some stl files, complete as it needs to be, to just 'print and fly'. I think thats where it starts getting into a bit of the ?mark area that people are concerned with.

Doing a full 3D printed bird from scratch is more like rolling your own fiberglass tubing and nose cone, etc. with more traditional materials, than buying a kit or buying off the shelf components.

My 3d printed bird thats midpower has about 7 pages of assembly instructions - not so much because of the 3d nature, because it dives in a bit more of the avionics setup too. So its just not print and fly.

Sure, you can do a poor job building a 3D printed rocket, but it's just as easy to do a poor job building a cardboard and wood rocket.

Oh sure... some of the l1 and l2 rockets that have shown up you kinda shake your head at. So yes, it happens.