Heating primarily and there was likely some flutter.
With the Markforged (if it is the Mark Two) solid strands of carbon fiber (or fiberglass or kevlar) and be inlaid into the print to increase the rigidity and give it a solid core to withstand and fluttering since nylon is more flexible than pet. However the Onyx material on its own may survive landing better than if it was stiffened with CF.
With the Markforged (if it is the Mark Two) solid strands of carbon fiber (or fiberglass or kevlar) and be inlaid into the print to increase the rigidity and give it a solid core to withstand and fluttering since nylon is more flexible than pet. However the Onyx material on its own may survive landing better than if it was stiffened with CF.
Exactly, the heating softened the leading edges, which allowed them to flutter. You can literally see the flutter in the edge as it cooled.Heating primarily and there was likely some flutter.
That said, I do use printed fins as the core of a composite construction. I've used a layer of fiberglass on the outside surface of small fins printed with a symmetric Von Karman profile on a minimum diameter rocket, and you probably could have used something similar on that fin can.
I've been playing around with much larger fins, where I print half a fin in Von Karman profile split vertically, laying flat on the print bed, and then laminating (with epoxy) two sides of the fins together around a layer of carbon fiber as core, and then a layer of fiberglass on the outside surface.
To take a look at the performance advantage at supersonic Mach numbers of the Von Karman fin airfoil, the Von Karman fin airfoil (I assume symmetric for both the leading and trailing edges) can be nicely approximated by a selecting the Biconvex fin airfoil input in RASAero II.
View attachment 477116
The rocket supersonic CD can then be compared to the supersonic CD with the traditional Hexagonal airfoil.
Charles E. (Chuck) Rogers
Rogers Aeroscience
To take a look at the performance advantage at supersonic Mach numbers of the Von Karman fin airfoil, the Von Karman fin airfoil (I assume symmetric for both the leading and trailing edges) can be nicely approximated by a selecting the Biconvex fin airfoil input in RASAero II.
View attachment 477116
The rocket supersonic CD can then be compared to the supersonic CD with the traditional Hexagonal airfoil.
Charles E. (Chuck) Rogers
Rogers Aeroscience
Pretty solid guess.Here is some data.
The RASAero II simulation predicted going above Mach 1 from about 1.2 to 9.1 seconds with a peak around Mach 2. Max altitude was predicted to be 23k feet.
View attachment 482427
Here is the barometric altitude measured onboard. The melted fins really killed the altitude to just 17k feet.
View attachment 482428
Zooming into the first few seconds, there are two kinks in the baro data. The kink at 1.2 s agrees with the prediction of hitting Mach 1 and a pressure change.
View attachment 482429
Not sure what is happening with the kink at 7.1 s. Is this the rocket again passing through mach, but at an earlier time than the simulation because the fins are melting and losing speed/altitude?
Can't you look at the velocity curve to see if it was passing mach at that time?Not sure what is happening with the kink at 7.1 s.
Can't you look at the velocity curve to see if it was passing mach at that time?
Oh, OK. I've no experience with Mach data. I just assumed you could smooth the data enough around the glitches to get a good guess.Well, no. Not with this baro data. Velocity derived from baro altitude is usually suspect, and it is totally meaningless in this case with the discontinuities in the altitude curve.
Rocket science is easy. Rocket engineering is hard.Its not like its rocket science.
Here is some data.
The RASAero II simulation predicted going above Mach 1 from about 1.3 to 9.2 seconds with a peak around Mach 2. Max altitude was predicted to be 23k feet.
View attachment 482427
Here is the barometric altitude measured onboard. The melted fins really killed the altitude to just 17k feet.
.........
Zooming into the first few seconds, there are two kinks in the baro data. The kink at 1.4 s agrees with the prediction of hitting Mach 1 and a pressure change.
View attachment 482429
Not sure what is happening with the kink at 7.2 s. Is this the rocket again passing through mach, but at an earlier time than the simulation because the fins are melting and losing speed/altitude?
I launched a 54mm min dia rocket with a 3d printed fin can by Landru several years ago, using an I65 motor. Right from the start, I was in trouble. Perhaps the rocket sat too close to the blast plate, because the rocket immediately began to corkscrew and the result was not good. Upon retrieving the rocket, I noticed the fins were melted and resulted in what looked like a boat motor prop. Two fins bent in one direction and the third bent in the opposite direction.
I'm thinking about it. I don't sell very many so it may be an option. Half the sauce is getting the print settings dialed for a good surface finish and lightweight finished product with good bonding...
Is plain-old-boring ABS an option? There is a feeling out there that PETG for temperature resistance is not that great in real-world situations, tho it certainly is superior to PLA according to my basic testing.
+1 PC blendABS and PC Blend are better options.
+1 PC blend
Seeing as how you got the rocket back in one piece instead of confetti, I'd say it was a successful flight.
Now I wouldn't want to fly that rocket again, that would be pushing your luck.
Enter your email address to join: