Tripoli prohibition on the use of 3D printed fin cans for L3 certification

[RocketRev]

Much of this discussion reminds me of Andrew Yang's arguments for starting a "universal income." He says that automation is putting lots of people out of work. That is true without a doubt, but automation has been putting people out of work for decades before Andrew Yang was even born. There may come a time in the future when automation may make working for a living obsolete and the need for a "universal income" might become a great idea. But we're not there yet. Yes, automation has put some people out of work. But to be frankly honest, I don't think we're likely to see automation make the human worker obsolete in my lifetime. So Andrew Yang's "universal income" is an idea who's time is not here yet. Its pretty much the same with 3-D printing. I have no doubt that eventually the BoD will ok the use of self-designed/built 3-d fin cans for cert flights. But we're not there yet. Why? Because far too many current 3-d printed parts being used in hobby rocketry, including fin cans, are FAILING. I've seen a bunch of them fail myself.
For the time being, as has been already said in other words, "the jury is still out" on 3-d printed fin cans. We are not yet at the point that we can ok their use for certification flights. Anybody besides me remember the controversies around hybrid cert flights? Some were certified even though they didn't get anywhere near the altitude that was expected? Was their flight actually the motor size that they said it was going to be? If the on-board tank only filled half way before ignition, was it really a level three flight? Was it actually only an "L" motor? Questions arose that needed answering before we could really know if hybrid flights were achieving what they were supposed to be achieving. I still have my doubts to be honest. Empirical data is the only answer.
For now, 3-d fin cans are in that same limbo area. And until we gather a whole lot more information we shouldn't take the chance on doing cert flights with them. Its just that simple. Will the time come that we will? Most probably. We're just not there yet.

Brad

 

[Steve Shannon]

Just for clarification, fin cans are not prohibited for Tripoli L1 or L2 cert flights and never have been.

 

[new2hpr]

Note: Devil's Advocate Post
By these same arguments, when fiberglass airframes first came into vogue, did anyone question them or was there ANY period of trial/experimentation before they were acceptable for cert flights? They very quickly solved structural issues in high stress flights, so does that absolve the builder of knowing how to specify an airframe capable of handling the load? By extension, someone certing with a kit - shouldn't the cert require that the builder also be capable of designing, verifying stability, etc? Someone else has "done all the work" by designing the kit (not all that far of a stretch from someone else designing the STL file or the Acme fin can). Do we need to require cardboard airframes? Does the builder need to roll his own from paper layers? Does he need to make his own paper from hand-ground pulp from a tree he grew himself?

The rat-hole can be taken to extreme. I think if a builder has shown that the 3d-printed part (whatever it is) has been tested to the limits of his prior cert level (actual flights) and maybe show structural testing data, he should fly (away cell of course).
-Ken

 

[John Kemker]

Note: Devil's Advocate Post
By these same arguments, when fiberglass airframes first came into vogue, did anyone question them or was there ANY period of trial/experimentation before they were acceptable for cert flights? They very quickly solved structural issues in high stress flights, so does that absolve the builder of knowing how to specify an airframe capable of handling the load? By extension, someone certing with a kit - shouldn't the cert require that the builder also be capable of designing, verifying stability, etc? Someone else has "done all the work" by designing the kit (not all that far of a stretch from someone else designing the STL file or the Acme fin can). Do we need to require cardboard airframes? Does the builder need to roll his own from paper layers? Does he need to make his own paper from hand-ground pulp from a tree he grew himself?

The rat-hole can be taken to extreme. I think if a builder has shown that the 3d-printed part (whatever it is) has been tested to the limits of his prior cert level (actual flights) and maybe show structural testing data, he should fly (away cell of course).
-Ken

The major difference is that fiberglass airframes were already available and had been used for a bit before the three-tier certification process came about. I originally certified as #2499, no tiers. NAR had just come out with their tiered approach, which just had you fly a G to over 1000 ft. and you were "Level 1" certified. Level 2 NAR required successfully fly an I before you could buy a J. There was no Level 3. Dave Gawlik, Tim Eiszner and several others that I knew of were flying fiberglass airframes. It was shortly thereafter that NAR and TRA got together and standardized the certification process.

 

[Flyfalcons]

Note: Devil's Advocate Post
By these same arguments, when fiberglass airframes first came into vogue, did anyone question them or was there ANY period of trial/experimentation before they were acceptable for cert flights? They very quickly solved structural issues in high stress flights, so does that absolve the builder of knowing how to specify an airframe capable of handling the load? By extension, someone certing with a kit - shouldn't the cert require that the builder also be capable of designing, verifying stability, etc? Someone else has "done all the work" by designing the kit (not all that far of a stretch from someone else designing the STL file or the Acme fin can). Do we need to require cardboard airframes? Does the builder need to roll his own from paper layers? Does he need to make his own paper from hand-ground pulp from a tree he grew himself?

The rat-hole can be taken to extreme. I think if a builder has shown that the 3d-printed part (whatever it is) has been tested to the limits of his prior cert level (actual flights) and maybe show structural testing data, he should fly (away cell of course).
-Ken

Kit or not, an L3 applicant will be proving to their advisors their knowledge of their's rocket's stability and expected performance on their chosen motor. Among numerous other details.

Honestly, I'm not sure why kit versus scratch is such a big thing. All these high power rockets are basically the same thing, and changing the fin shape, body tube length, and nose cone ratio from designs available in kit form doesn't really require any special skill. And my L3 bird is a scratch build.

 

[Wallace]

I actually decided AGAINST using a markforged for my minimum-diameter 3D printed rocket (you might remember it from the November CRMRC launch - the I205 powered rocket I never found again) for a couple of reasons. In order to inlay the fiber reinforcements, the parts have to be sufficiently thick for a fiber run both out and back, along with a sheath of the more conventional FDM filament around it. This makes it impossible to print a fully-formed fin can with reinforcements unless you use very thick fins. Also, the nylon or Onyx (proprietary, but like 80% nylon) filaments are significantly more flexible than PLA, to the point where fin flutter was a major concern on the markforged printed parts, but was not a problem at all on the parts I ended up flying, which were made from PLA on a Prusa. The one major advantage that the markforged has for airframe components in HPR is that nylon has a much higher glass transition temperature than PLA, ABS, or PETG, though this can be largely alleviated with primer and paint to give a bit of a dissipative layer over the more temperature sensitive components.

I plan to refine that design I flew last November (that really was a proof of concept where I was very concerned about thermals - hence the lack of an onboard tracker, I didn't want to risk losing it if there was a thermal failure), and eventually perhaps scale it up to a 38mm minimum diameter rocket. If there's interest I can throw up a thread documenting the project - there's some interesting thermal and structural analysis of 3D printed components at transsonic and supersonic Mach number I could share with everyone.

Whaddaya wating for? Throw up asap. The numbers, I mean...

 

[wsume99]

Much of this discussion reminds me of Andrew Yang's arguments for starting a "universal income." He says that automation is putting lots of people out of work. That is true without a doubt, but automation has been putting people out of work for decades before Andrew Yang was even born. There may come a time in the future when automation may make working for a living obsolete and the need for a "universal income" might become a great idea. But we're not there yet. Yes, automation has put some people out of work. But to be frankly honest, I don't think we're likely to see automation make the human worker obsolete in my lifetime. So Andrew Yang's "universal income" is an idea who's time is not here yet. Its pretty much the same with 3-D printing. I have no doubt that eventually the BoD will ok the use of self-designed/built 3-d fin cans for cert flights. But we're not there yet. Why? Because far too many current 3-d printed parts being used in hobby rocketry, including fin cans, are FAILING. I've seen a bunch of them fail myself.
For the time being, as has been already said in other words, "the jury is still out" on 3-d printed fin cans. We are not yet at the point that we can ok their use for certification flights. Anybody besides me remember the controversies around hybrid cert flights? Some were certified even though they didn't get anywhere near the altitude that was expected? Was their flight actually the motor size that they said it was going to be? If the on-board tank only filled half way before ignition, was it really a level three flight? Was it actually only an "L" motor? Questions arose that needed answering before we could really know if hybrid flights were achieving what they were supposed to be achieving. I still have my doubts to be honest. Empirical data is the only answer.
For now, 3-d fin cans are in that same limbo area. And until we gather a whole lot more information we shouldn't take the chance on doing cert flights with them. Its just that simple. Will the time come that we will? Most probably. We're just not there yet.

Brad

Ok, so the fin can fails on cert flight. Don't lots of conventionally built rockets fail on cert attempts too??? Then you haven't earned your certification. If you can build, safely fly and recover a rocket with the appropriate impulse class motor then you should be certified, period. If 3D printed fin cans weren't strong enough or unsafe then why aren't they banned for all L3 flights, not just cert attempts???

In my opinion the only valid argument for not allowing a certain type of building technique is if the parties responsible for witnessing the attempt do not possess the ability to determine the rocket is flight worthy prior to the attempt. Does anyone think that a flyer is going to go thru all the trouble AND EXPENSE to certify L1 and L2 and then attempt a L3 without being confident their rocket is flight worthy???? The issue isn't the builder's knowledge or skills but rather it's the certifying body's ability to evaluate the rocket being presented for the certification attempt. That's the real the reason for the ban but nobody wants to come right out and say it. That's what bothers me about this whole situation, just be straightforward about the reason.

To be clear, I'm not saying the ban was wrong I just disagree with the rationale given for it.

 

[jjwb22101]

Whaddaya wating for? Throw up asap. The numbers, I mean...

Thread started! It'll take a little while for me to turn the spreadsheets into some presentable graphs, and unfortunately I don't have any good pictures or video of the launch from last November - It's a bit tricky when it chuffs and then immediately accelerates upwards at something like 60G's!

https://www.rocketryforum.com/threa...h-and-fast-with-3d-printed-components.156975/

 

[Wallace]

Thread started! It'll take a little while for me to turn the spreadsheets into some presentable graphs, and unfortunately I don't have any good pictures or video of the launch from last November - It's a bit tricky when it chuffs and then immediately accelerates upwards at something like 60G's!

https://www.rocketryforum.com/threa...h-and-fast-with-3d-printed-components.156975/

Thank you Sir. I'm fairly certain we'll all benefit.

 

[Wallace]

Ok, so the fin can fails on cert flight. Don't lots of conventionally built rockets fail on cert attempts too??? Then you haven't earned your certification. If you can build, safely fly and recover a rocket with the appropriate impulse class motor then you should be certified, period. If 3D printed fin cans weren't strong enough or unsafe then why aren't they banned for all L3 flights, not just cert attempts???

In my opinion the only valid argument for not allowing a certain type of building technique is if the parties responsible for witnessing the attempt do not possess the ability to determine the rocket is flight worthy prior to the attempt. Does anyone think that a flyer is going to go thru all the trouble AND EXPENSE to certify L1 and L2 and then attempt a L3 without being confident their rocket is flight worthy???? The issue isn't the builder's knowledge or skills but rather it's the certifying body's ability to evaluate the rocket being presented for the certification attempt. That's the real the reason for the ban but nobody wants to come right out and say it. That's what bothers me about this whole situation, just be straightforward about the reason.

To be clear, I'm not saying the ban was wrong I just disagree with the rationale given for it.

Don't forget that trump card "S" word (Safety btw.) , seems as though once it's invoked, no matter how irrelevant, all arguments are thereafter null. Argue against safety? You must be out of your mind...

 

[BDB]

Has anyone tried tip-to-tip over a 3D printed fincan? It seems like that would be a great way to strengthen the build and to get a desired airfoil shape.

 

[Steve Shannon]

Note: Devil's Advocate Post
By these same arguments, when fiberglass airframes first came into vogue, did anyone question them or was there ANY period of trial/experimentation before they were acceptable for cert flights? They very quickly solved structural issues in high stress flights, so does that absolve the builder of knowing how to specify an airframe capable of handling the load? By extension, someone certing with a kit - shouldn't the cert require that the builder also be capable of designing, verifying stability, etc? Someone else has "done all the work" by designing the kit (not all that far of a stretch from someone else designing the STL file or the Acme fin can). Do we need to require cardboard airframes? Does the builder need to roll his own from paper layers? Does he need to make his own paper from hand-ground pulp from a tree he grew himself?

The rat-hole can be taken to extreme. I think if a builder has shown that the 3d-printed part (whatever it is) has been tested to the limits of his prior cert level (actual flights) and maybe show structural testing data, he should fly (away cell of course).
-Ken

Your last paragraph is probably the direction this will eventually take.

 

[Steve Shannon]

Don't forget that trump card "S" word (Safety btw.) , seems as though once it's invoked, no matter how irrelevant, all arguments are thereafter null. Argue against safety? You must be out of your mind...

I’m curious why just now, six months after the announcement, you’ve started gnashing your teeth and wailing over this rule to the point where you’re attacking us as hiding behind safety and not listening to reason. If we truly felt fin cans were unsafe we would prohibit them completely. We didn’t.

The primary reason Tripoli initially prohibited commercial fin cans for L3 certification flights (but only for L3 certification flights) was because it felt that buying a fin can and screwing it on a piece of tubing didn’t demonstrate the level of skill a person should have to be certified at our highest certification level. It risked making certifications too easy. Our highest level of certification demands our most rigorous testing.

When we noticed a surge in people buying cheap 3D printers and sharing files, we felt that this could be similar to the commercial fin cans in that a person could potentially download a fin can file, print it, and claim it as their own work without actually doing anything more than downloading it and printing it. And yes, that viewpoint does reflect our lack of experience at the time of the rule. So did our secondary statement that the parts made by 3D printers weren’t yet strong enough. That concern was also shaped by the materials available at the time and experience at the hobbyist and professional level (we have board members who have experience with both hobby and expensive professional prototyping machines; we’re not quite the Luddites you might expect).
Rather than complaining about how we never listen you should be demonstrating how far technology and materials have come since we established that rule. Show us that it’s not a potential risk for one person just print a 3D printed fin can and fly an M without any knowledge. Help us understand how to incorporate this technology in our L3 certification process without decreasing the rigor of the level 3 certification.
The people on the board are some of the earliest adopters of new technologies. But, being on the board forces each of us to consider things like this in terms of how it could affect the hobby for years to come. That’s why we will frequently adopt a conservative approach while we gather data. Attacking us for that doesn’t help your case.

 

[liv3mind]

I’m curious why just now, six months after the announcement, you’ve started gnashing your teeth and wailing over this rule to the point where you’re attacking us as hiding behind safety and not listening to reason. If we truly felt fin cans were unsafe we would prohibit them completely. We didn’t.

The primary reason Tripoli initially prohibited commercial fin cans for L3 certification flights (but only for L3 certification flights) was because it felt that buying a fin can and screwing it on a piece of tubing didn’t demonstrate the level of skill a person should have to be certified at our highest certification level. It risked making certifications too easy. Our highest level of certification demands our most rigorous testing.

When we noticed a surge in people buying cheap 3D printers and sharing files, we felt that this could be similar to the commercial fin cans in that a person could potentially download a fin can file, print it, and claim it as their own work without actually doing anything more than downloading it and printing it. And yes, that viewpoint does reflect our lack of experience at the time of the rule. So did our secondary statement that the parts made by 3D printers weren’t yet strong enough. That concern was also shaped by the materials available at the time and experience at the hobbyist and professional level (we have board members who have experience with both hobby and expensive professional prototyping machines; we’re not quite the Luddites you might expect).
Rather than complaining about how we never listen you should be demonstrating how far technology and materials have come since we established that rule. Show us that it’s not a potential risk for one person just print a 3D printed fin can and fly an M without any knowledge. Help us understand how to incorporate this technology in our L3 certification process without decreasing the rigor of the level 3 certification.
The people on the board are some of the earliest adopters of new technologies. But, being on the board forces each of us to consider things like this in terms of how it could affect the hobby for years to come. That’s why we will frequently adopt a conservative approach while we gather data. Attacking us for that doesn’t help your case.

This.

 

[Wallace]

I’m curious why just now, six months after the announcement, you’ve started gnashing your teeth and wailing over this rule to the point where you’re attacking us as hiding behind safety and not listening to reason. If we truly felt fin cans were unsafe we would prohibit them completely. We didn’t.

The primary reason Tripoli initially prohibited commercial fin cans for L3 certification flights (but only for L3 certification flights) was because it felt that buying a fin can and screwing it on a piece of tubing didn’t demonstrate the level of skill a person should have to be certified at our highest certification level. It risked making certifications too easy. Our highest level of certification demands our most rigorous testing.

When we noticed a surge in people buying cheap 3D printers and sharing files, we felt that this could be similar to the commercial fin cans in that a person could potentially download a fin can file, print it, and claim it as their own work without actually doing anything more than downloading it and printing it. And yes, that viewpoint does reflect our lack of experience at the time of the rule. So did our secondary statement that the parts made by 3D printers weren’t yet strong enough. That concern was also shaped by the materials available at the time and experience at the hobbyist and professional level (we have board members who have experience with both hobby and expensive professional prototyping machines; we’re not quite the Luddites you might expect).
Rather than complaining about how we never listen you should be demonstrating how far technology and materials have come since we established that rule. Show us that it’s not a potential risk for one person just print a 3D printed fin can and fly an M without any knowledge. Help us understand how to incorporate this technology in our L3 certification process without decreasing the rigor of the level 3 certification.
The people on the board are some of the earliest adopters of new technologies. But, being on the board forces each of us to consider things like this in terms of how it could affect the hobby for years to come. That’s why we will frequently adopt a conservative approach while we gather data. Attacking us for that doesn’t help your case.

Steve: You either mis-read my intent and or I wasn't clear enough. The "safety" comment was in no way directed at you, just a general observation from a few years experience on the forum. Also, as I've stated multiple times, I have 0 interest in printing fin cans, I enjoy building them way to much. Printing 'em would in my mind make for a "boring" build. My interest lies in printing parts that would be either extremely difficult or impossible to make otherwise.

 

[liv3mind]

This is not directly related to rocketry but it is directly related to 3d printing and bonding. As part of what I do for a personal business I 3d print fin boxes for surfboards. Just yesterday I had my first product failure, the epoxy resin has problems bonding to the plastic, in this instance, the fins took a physical impact and the resin de-bonded from the plastic, causing the box to spin/move slightly. The board will now need to be routered out and the fin box replaced. I remedied this by adding vertical channels to create a physical barrier with the resin to keep the box from spinning. To be clear the resin does not have issues bonding to foam, or fiberglass, only the plastic. Anyone interested, I have done a TON of hands on testing with PLA, PETG, and ABS and epoxy bonding. Pictures of the two different versions below.

If your interested in seeing more of the application, you can check more pictures on Instagram @liv3mind

Old design left, new right.

 

[Jose Saura]

Is this the Jose that has the Janus series rockets and flies with TCR sometimes?

Yes

 

[jbr]

so what proof is needed to make sure you designed it?
I can show the f360 file and being printed on my custom designed 300x300x1000 printer
the L1500 I flew it on was 5000NS, just shy of an M motor, one more grain makes it a M1800 with 6000NS

and you may have noticed what lettering I added to each 1/4 segment

 

[jbr]

fusion rendered version

 

[Steve Shannon]

so what proof is needed to make sure you designed it?
I can show the f360 file and being printed on my custom designed 300x300x1000 printer
the L1500 I flew it on was 5000NS, just shy of an M motor, one more grain makes it a M1800 with 6000NS

and you may have noticed what lettering I added to each 1/4 segment

I did notice your initials on a previous post, John. I’ve watched your posts; I have no doubt you did this yourself. Nice work.

 

[OverTheTop]

Has anyone tried tip-to-tip over a 3D printed fincan? It seems like that would be a great way to strengthen the build and to get a desired airfoil shape.

I attempted to print an isogrid core for fins on my Nike Apache, in ABS, and then skin them with thin CF plate. I aborted that trial as I couldn't get the bonding with the ABS consistent.

 

[Wallace]

This is not directly related to rocketry but it is directly related to 3d printing and bonding. As part of what I do for a personal business I 3d print fin boxes for surfboards. Just yesterday I had my first product failure, the epoxy resin has problems bonding to the plastic, in this instance, the fins took a physical impact and the resin de-bonded from the plastic, causing the box to spin/move slightly. The board will now need to be routered out and the fin box replaced. I remedied this by adding vertical channels to create a physical barrier with the resin to keep the box from spinning. To be clear the resin does not have issues bonding to foam, or fiberglass, only the plastic. Anyone interested, I have done a TON of hands on testing with PLA, PETG, and ABS and epoxy bonding. Pictures of the two different versions below.

If your interested in seeing more of the application, you can check more pictures on Instagram @liv3mind

Old design left, new right.

View attachment 403311

Have you tried Glenmarc G5000 (Rocketpoxy) Yet? Out of everything I've done testing on it's by far the best for most plastics.

 

[jbr]

My point in all of this is to thank Steve for giving me the desire to prove some things.
I will point out that the board has every right to say what can and can't be used but the reasons given are flat wrong.
It would have been better to just say that ALL fin cans can't be used regardless of who made them and what materials they are made from.




Why 6 months or more after this was first brought up?
It took me around 6 months to design and source parts and manufacture some of them and build the $2500 custom printer to make rocket parts.
This is a project that I have been thinking about doing and Steve gave me the impetus to complete it.



so the statements to be contested were
----------------------------------------
1. It’s impossible to know whether the L3 candidate designed the fin can. Simply printing a shared file doesn’t demonstrate expertise or knowledge, which is what certification represents.
2. The strength of most 3D printed parts is still not strong enough.
-------------------------------------------

my answers
1. I have shown it is not impossible to prove you designed and built the rocket and parts and it did take quite a bit of expertise and knowledge
2. My parts are strong enough

I also printed the nosecone

 

[Steve Shannon]

My point in all of this is to thank Steve for giving me the desire to prove some things.
I will point out that the board has every right to say what can and can't be used but the reasons given are flat wrong.
It would have been better to just say that ALL fin cans can't be used regardless of who made them and what materials they are made from.




Why 6 months or more after this was first brought up?
It took me around 6 months to design and source parts and manufacture some of them and build the $2500 custom printer to make rocket parts.
This is a project that I have been thinking about doing and Steve gave me the impetus to complete it.



so the statements to be contested were
----------------------------------------
1. It’s impossible to know whether the L3 candidate designed the fin can. Simply printing a shared file doesn’t demonstrate expertise or knowledge, which is what certification represents.
2. The strength of most 3D printed parts is still not strong enough.
-------------------------------------------

my answers
1. I have shown it is not impossible to prove you designed and built the rocket and parts and it did take quite a bit of expertise and knowledge
2. My parts are strong enough

I also printed the nosecone

I agree, John. You have definitely proven that I was completely wrong when I said it was impossible to know whether an L3 candidate designed the fin fan.
I believe that my statement that “Simply printing a shared file doesn’t demonstrate expertise or knowledge, which is what certification represents” is logically correct, but you have shown me that it’s highly unlikely that a person could “simply print a shared file” and have it work.
And, while I don’t know whether “most” 3D parts are strong enough, you have shown that you are capable of making them strong enough.

So this brings up the following groups of questions:
Should a person be certified who has never demonstrated building a high power rocket using traditional skills?

If the board were to accept self printed fin cans for all three levels (remember that they are already accepted for L1 and L2) it’s possible that a person could certify all three levels without ever knowing how to use glue a fin on straight. Is that acceptable?

What restrictions should be established for 3D printed fin cans?

If we see a large shift towards 3D printed fin cans, what will be the long term effect (if any) on how amateur rocketry advances and how it is perceived by regulators?

 

[jbr]

Since the TAPs are ultimately responsible for approving the design and parts used in the rocket for L3 certification and watching the attempt, I personally would put the onus on them.
Some kits make things much simpler as you don't have to design anything, most even provide the rocsim file, so all you have to do is glue it together, and the hard part is the documentation.

After one of my TAPs looked at the 3d printed parts, he was amazed at what could be done, but I doubt that he would have approved of it for certification.

I do make a lot of my own parts and hence have the equipment to do that and have made rockets capable of certing before, failing my last attempt 20 years ago (hard to think it was that long ago, but life got in the way) with a 6 inch zipper in the top tube which could have been cut off and flown again the same day. As a side note another L3 attempt was done the same day with a shattered phenolic tube and his TAP told hime to go buy another at the Giant Leap vendor on vendor row and he would sign the paperwork.

As I said before I really don't care what the rules are, but they should be plainly written and adhered to by ALL TAPS, and we don't need reasons why the rules are the way they are, they just are.

And what I have seen is that after you have your L3, you can do whatever you want, even with no hope of recovery or harming people standing 50 feet away from the launch.

 

[TimothyG]

I personally don’t feel requirement of one or another skill should be considered. The glueing a fin on straight comment is what this is directed towards. Certification is verifying your overall skill and experience to safely fly rockets. Just because someone has zero skill with balsa fin rockets doesn’t mean they lack the ability to safely do some other form of material work. My personal experience is more in line with metal work so I’m inclined to produce a metal fincan for my L3 over surface bonding fins in place. Same goes for someone who may have a great deal of experience with 3D prints. They could understand the limitations and advantages of the process well enough to accomplish the certification process. I personally don’t so I avoid the manufacturing techniques.

 

[jbr]

Now if you really want my personal opinion, understand that it is to test what I think is needed for L3 certification and is draconian and probably not really popular with kit manufacturers.
You need to be able to show you can do more than just glue on fins, you should be able to cut straight fin slots, make your own recovery harness, cut out your fins, glass rocket and fins if needed, in short make a custom design and the parts for it, and not use a kit. I stop short of making your own chutes, but I did do that for my 1st attempt.

I need to fly this rocket again but it requires an M motor ellis M1000 only took it to 5000, and I now have the vehicle to transport it again.

Here is the video of my first attempt, it starts at 1:29
the V2 our club made starts at 1:44

 

[liv3mind]

Have you tried Glenmarc G5000 (Rocketpoxy) Yet? Out of everything I've done testing on it's by far the best for most plastics.

I have not no, shapers and glassers in the surfing industry have their resins they love to use, so for us it’s about finding ways to create a better physical bond via channels/cutouts and texture. In the case of how much pressure and force fins have applied to them in the water, sanding/scuffing is not enough

 

[wsume99]

This....

I personally don’t feel requirement of one or another skill should be considered. The glueing a fin on straight comment is what this is directed towards. Certification is verifying your overall skill and experience to safely fly rockets. Just because someone has zero skill with balsa fin rockets doesn’t mean they lack the ability to safely do some other form of material work. My personal experience is more in line with metal work so I’m inclined to produce a metal fincan for my L3 over surface bonding fins in place. Same goes for someone who may have a great deal of experience with 3D prints. They could understand the limitations and advantages of the process well enough to accomplish the certification process. I personally don’t so I avoid the manufacturing techniques.

@Steve Shannon, first let me say I'm thrilled to see the conversation has turned in the direction it has. This is exactly where I hoped it would go. I'll throw in my 2 cents on your questions...

1) Should a person be certified who has never demonstrated building a high power rocket using traditional skills?
What is the purpose of certification? Isn't it to demonstrate that the individual possesses the skill to build and successfully fly a rocket in the impulse range the certification level applies to?? I think as long as the person is building their own rocket then it's up to them to determine how to use the skills they have to meet the requirements. I think you either allow 3D printed fins cans within a certification level or your don't. If you allow people to fly 3D printed fin cans in L3 then you should be able to cert with them. I'm fine with someone reaching L3 without ever building a rocket using traditional methods. Why, because they are meeting the same requirements that every other certified flyer has. They are demonstrating knowledge of amateur rocketry and an ability to build and fly rockets safely. How they do it is of little importance to me. Again, as I've said in this thread and others regarding this topic, 3D printing a fin can is not easy. I'm only planning my L1 attempt ATM but I spent a lot of time researching what I was doing, learning from others and then deciding on what was the best way to build my L1 rocket using conventional methods. From my own experience with 3D printing I can say that process is the same when printing a part. Even if I download a model I still have to think about how I want to print the part and there can be several builds before I get it right. There is no shortcut to building parts - rocketry or something else. So someone who would obtain L1, L2, and L3 certification with only 3D printed fin cans would have a very high amount of skill and that's the kind of people we want in amateur rocketry.

2) What restrictions should be established for 3D printed fin cans?
That is a good question. Maybe a simple restriction on the thickness of the fins? L1 - 1/16" minimum thickness, L2 - 1/8" minimum thickness, L3 - 1/4" minimum thickness. There are so many variables it would be difficult to implement something other than a high level rule like I suggested. And as printed fin cans become more prevalent then empirical data could be used to establish more effective restrictions.

3) If we see a large shift towards 3D printed fin cans, what will be the long term effect (if any) on how amateur rocketry advances and how it is perceived by regulators?
Not sure but I think excluding 3D printing makes amateur rocketry less inclusive and that is the opposite of what I see today and what I think we are about. I think there are more than enough experienced flyers out there overseeing the sport that any negative effects of allowing printed fin cans would be mitigated by your second question and my suggested response. Consider this scenario ... printed fin cans are allowed with the basic rules I proposed above and a rash of failures that result in a reduction of safety occurs and then the community responds with restrictions to eliminate those risks. I think that builds confidence in the amateur rocketry community.

Bottom line, I see way more upside from allowing printed fin cans than from prohibiting them.

 

[Maxwelljets]

If you allow people to fly 3D printed fin cans in L3 then you should be able to cert with them.

The same logic applies to flying pyramids, spools, and other oddroc designs, but I have heard zero complaints from people that those are specifically disallowed for cert flights.

I really don't think this restriction is that unreasonable. Once you're certified, you can do whatever you want, but L3 cert projects need to be easily evaluated by TAP members.

Granted, the reasoning that it's "hard to prove that the L3 candidate designed the fin can themself" is a bit silly. It's far easier to prove who designed a 3d model of a fin can than it is to prove that the L3 candidate did all the other work on the rocket themself.