beeblebrox
8 C6-0, 12 D11-9, 20 D20-0, 20 E5-0, 3 Cinerocs
I understand the problems Steve Shannon describes above but I think there might be better ways to address them.
Problem #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.
Building a fin can by hand does not prove the builder has any knowledge about rocketry. All someone has to do is follow simple steps to bind together simple parts. It might help prove the candidate has skills applying epoxy, sawing, using fiber glass, etc. but these skills are as related to rocketry as using a 3D printer. Not that much.
So I think we need to agree on what skills we want to measure and then plan accordingly. To me it would be much more important to evaluate a candidate's ability to stress test a rocket before flying it for example and for the candidate to prove that the rocket passes a series of rigorous tests. For example:
When using traditional building techniques, it is not easy to perform some of these tests because we only have one rocket and these tests can destroy it. A big advantage of 3D printed models is that we can re-print as many as we need, making it possible to conduct much more rigorous tests and this will in turn produce much better and much safer rockets.
- Does the shock cord support more that 50x the weight of the rocket?
- Do the fins support a later force that is n times larger than the mass of the rocket?
- How much force needs to be applied to the motor mount before it fails?
Problem #2. The strength of most 3D printed parts is still not strong enough.
This is simply not correct. There are many materials and many techniques to make very strong 3D printed parts. I have seen many failures of rockets build by conventional methods.
Tripoli and NAR have done an excellent job at helping define safety rules in particular related to where and how rockets should be launched. What I think could help alleviate this concern is to publish an official set of rules, as the examples above, that clearly specify tolerances and testing procedures for different types of rockets. Performing, recording and demonstrating the results of these tests should be a very important step to passing certification for any level, not just L3.
Final comments:
If we want to attract younger generations to rocketry, we need to adapt to new ways of doing things. Banning 3D printing is not going to help so I would like to suggest that we instead embrace the new technology. Rather than worrying about some unethical candidate that does not follow the rules, lets try to create an environment were more people can collaborate on creating and improving rocket designs. To help with this, I have shared my designs online here. It would be great if NAR and Tripoli could work together on enabling collaboration in designing advanced rockets.
If at some point becomes "too easy" to build a fin can, then we should all be happy about that and the best thing is that we will then have time to work on improving other aspects of rocketry such as navigation, instrumentation, recovery, etc. All of these, will help advance the state of rocketry which after all is what we are all trying to do.
Thanks,
Jose Saura
Covington, WA
I agree 100%!!! As a point I have built a 3d printed Nike Smoke 2.7" Diameter, It flew great three times with high thrust F-Motors (F67 2x, F80 once), Yet someone else's "Conventional Kit" slightly larger, flown with a low thrust G25 shredded the fins off. (It was the Estes Pro line kit) 3D printed fin cans will have more accuracy of alignment, which is getting more important as the size of the rocket and velocity gets higher. I am working on some 3d printed fins right now that are designed to fir a piece of fiberglass sheet inside the fin and sticking out as a fin tab to the motor tube. It is SO much easier to cut fiberglass into rectangular shapes and not have to machine leading edges. Testing with high thrust motors hopefully by May or June. (I hate flying in freezing numb finger weather...lol)