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Tripoli prohibition on the use of 3D printed fin cans for L3 certification
At our monthly BoD meeting we discussed the proliferation of 3D printing. We all agree that the technology is exciting and will undoubtedly lead to some great designs. However, for two reasons the board has decided to prohibit the use of 3D printed fin cans for Level 3 certification flights. The...
3d printed kits for HPR? Haven't seen those...
boyceaerospacehobbies.com
The OP could be designing his own, which would be very cool. His main question was whether it was allowed, not whether someone makes a 3D kit. I hope he is designing/printing his own, would love to see a project like that! (I do not currently own a 3D printer, so I love seeing projects beyond my capabilities).
And, to be fair, Boyce has some kits that look like they could accomodate an H motor. I may pick up this HoJo and see if it can fly on a 29mm H - blow it out or blow it up!
Honest John Missile Builders Kit
Honest John “Builders Kit” is the easy way to build a scale flying model rocket. Once body tubes are added, lookout!
Very cool - hope to see it at Higgs!
As an RSO or when I’m inspecting a certification rocket I usually start out trying to squeeze the fins together. If there’s a hidden fault that might cause a failure in flight it’s better to have the fins break off in my hands before the attempt. I haven’t had an occasion to do this with a 3D printed fin can yet, but I have faith in the test.
Most 3D printed rocket failures I have seen are usually in the airframe, ejection charge goes off blowing them into several pieces, 3d printed attachment points failing, nosecones breaking mid-flight, every failure has been parallel to the Z-axis layer. I so far only two fliers at our field have proven to me that they can fully 3d print a rocket and it be recovered fully intact (both fly them on J motors). Typically failures on hybrid 3D print rockets a much rarer, usually they stem from an issue with either the nose cone breaking along the layers or the shock cord attachment point at the nosecone failing.
The failures I have seen are pretty much the same.
How is that any different than "traditional" materials and construction methods???
This was actually one of the most frequently cited reasons not to allow 3D printed fin cans, because expertise is still so lacking (and will be for some time) that we don’t have enough people who can evaluate whether a 3D printed rocket should be allowed to fly.
Not so, the failures I have seen with 3D printed rockets were the ones that got by ME (sometimes 100's f launches in a weekend). I RSO the vast majority of all flights at all TriCities Rocketeers launches, I 3D print and fully understand the failure modes, a little epoxy and paint can easily cover most any defect especially bad layer bonding. The most sucessful 3D printed rockets were the ones printed then post print processed. We have a couple of fliers from B.C. who really have 3D printing down predominantly use a fortified nylon filament of some type, that goes through a post print heat treated. Their fin cans when tapped remind me of fins made with autoclaved pre-preg carbon, they fly mainly J motors in them. Another flier (Jose) does completely 3d printed rockets and I have yet to see one of his have a failure and he has flown up to J motors iirc (dont recall his filament choices).
So you've never had a traditionally constructed rocket you've inspected fail during flight?
Absolutely I have had traditional construction fails get through the checks, usually they were shreds, separations, or other catostrophic events failures not on nominal flight profile events like ejection charges firing at apogee
RSO duties are primarily a safety inspection of the rocket and not an opportunity to preform a functional stress test of the rocket construction and components. If I had concerns on exceptable stress on parts and construction, attempting something that might break a part or assembly on someones rocket would not be a technique I would use.
I surely don't think this is designed or intended to be a destructive test. At the same time, if routine handling and or a small tug on the fins causes flight-preventing damage, that's a clear opportunity to have a safety chat.RSO duties are primarily a safety inspection of the rocket and not an opportunity to preform a functional stress test of the rocket construction and components. If I had concerns on exceptable stress on parts and construction, attempting something that might break a part or assembly on someones rocket would not be a technique I would use.
RSO duties are primarily a safety inspection of the rocket and not an opportunity to preform a functional stress test of the rocket construction and components. If I had concerns on exceptable stress on parts and construction, attempting something that might break a part or assembly on someones rocket would not be a technique I would use.
I try to put myself in the flyer's shoes; "would I like the RSO doing as you said to my rocket/property"? There is an obvious answer, especially if it results in damage. My reaction, as a flyer, more than likely, would not be a very pleasing one. It is not your place or mine to do such stress testing, as you called it. Most of us that do RSO can readily tell, via visual observation/inspection, if airworthiness construction is an issue, without phisical manipulation of parts.. At least that has been my experience. However, whatever works for you...
