GLR Mariah 54 - Block 3 Video Build

[cwbullet]

Take video.

I would like to take this time to suggest that everyone who has an interest in this bird to buy one. Support Giant Leap and buy one of these great kits.

They are an awesome vender and this kit is premium, high quality kit.

 

[CarVac]

Good luck with it. My professor shredded his on a K300 at XPRS this past September.

 

[REK]

Good luck with it. My professor shredded his on a K300 at XPRS this past September.

Thats interesting, did the rocket split in half or was it a fin came apart kind of shred?

 

[cwbullet]

Cwbullet it is my favorite model to this day and will continue to be my favorite. I will glady buy this model over and over again. I will be taking a very great friend of mine who is great at getting videos.

Your thread sold me on the Block 3. Now I own a block 2 and 3.

 

[CarVac]

Body tube failure, I believe. I didn't get a good look at it (felt sorry for him; he's never once had a successful flight that exceeded 10,000 ft AGL) but the fincan seemed largely intact.

 

[cwbullet]

I have flown my 38mm on higher thrust than that and no shreds. I would suspect there is something else involved. Are your sure there were no stability or drag issues? I did not even fiberglass the fins with tip to tip.

A K300 is pretty low thrust to get a shred. I am not say it is isn't possible, but definitely not expected.

 

[CarVac]

The something else involved was that it's 54mm, and that the overall impulse of the motor is greater than any commercial 38mm motor. The same wall thickness provides much less strength* in the larger diameter, and the rocket will spend a long time going really fast.

I didn't see the rocket before it was destroyed, nor did I witness the flight itself so I can't say for sure, but I doubt that the construction technique was the limiting factor.

*and by strength I refer to buckling resistance

 

[cwbullet]

What I am saying is overall speed is unlikely to be an issue. Mach Maybe, because the heat is sustained could induce failure but it is not even with the 7-12 second boost of a K300. Mach in this case would be very short lived.

Over all thrust is not a problem if there is not much kick and the rocket does not have fin drag that is high (Skeeter). It is the kick of a high thrust engine that causes the problem in my experience. My 54 mm Mariah has taken a J1299 and a J1999 and as low as a K270 without shredding and lived to tell about it. The 38 mm has gone as low as an I54 and I69 which are very low thrust and long burn. I am just saying that I suspect there is something else involved in the case and not the Mariah or the Magna Tube.

I asked the questions about construction because that is the usual case of a shred since these fins do not extend bast the tail. I also have several other minimum diameter Magna Frame builds that have wood fins that have handled the K300 without a problem.

 

[blackjack2564]

I thought it would be good to give out a heads up. On Decemeber 29th I will be taking the Mariah 54 and flying it on an L990 Blue Streak.

I just read this thread through....& did not see where you used the fiberglass to re-enforce the fins at all.
Did I miss it, or you didn't do it?
I love this kit & you did a wonderful job building & painting it. Beware though....1/16 in fins [.062] just glued on the fincan....flying on L's, might be a bit troublesome around 1.5 -2 mach ....where this motor should take you.

If I am incorrect & you did some extra re-enforcement go for it. If not, ya might want to try a large K next & see what happens. I have held in my hands 2 of these that did not survive L motors[one was missing a fin, the other sported a broken fin & was missing the upper third of fincan] and a third that did survive, WITH some glass added.

Good luck either way!

 

[CarVac]

It could just be my his luck with altitude rockets. He once made a rocket that was pretty much sure to go over 10,000 feet, stuck all of his best tracking and deployment electronics in it, and promptly lost it. Apparently, sometime after apogee, the Com-Spec just stopped receiving any signal...

 

[cwbullet]

That bites. I have a couple minimum diameter rockets in the woods around our field. I never learn that higher and faster has it's consequences.

A so for shredding, I am very good at that. I have an upscale big bertha where I has a momentary loss of common sense when I put a K2050 in it. It took off and littered the field with parts. I am sure they still fin them on ocassion. I found parts for months myself.

 

[cwbullet]

I have been indeed analyzing these shreds myself. They are indeed buckle failures due to the cause of the rocket going at an angle instead of going straight up. When going at an angle the mach forces are mostly attacking the nose cone and the fin area causing the rocket to bend and shred. If this model is to the survive its got to go straight up. I am one step ahead of this however. I will be adding a coupler to the inside to beef up the walls. Hopefully that will help in preventing any issues in case mine goes at an angle.

Good idea, but it does add a little weight. With an L you can add spare weight.

 

[CarVac]

If ever worried about the fins, I would worry about the tube peeling up at the cut in the fibers from the dado slotting. Not sure that the fins are long enough and forces high enough to do that, but I suspect that would be the failure mechanism.

 

[CCotner]

For what it matters, the M54 in question buckled along the spiral tube, immediately above the motor tube, right at the mach transition point in the flight. No deployment charges were fired during the flight. It appears that after buckling the top tube was damaged further, while the fincan was found intact. The flight appeared to multiple observers (in different positions) to be dead-on straight; the onboard baro altimeter recorded no detectable deviation from a straight flight given the atmospheric conditions, no other onboard data was recorded. I don't think there was any asymmetric flow contributing to the failure; it looks like it was a straight-up axial crush.

Also, as a side note, a rocket not going straight (arcing during burn, for instance) does not experience unusual mach behavior or forces. A rocket will only experience bending loads in flight if it is slightly unstable, or is coning or experiencing some other dynamic phenomenon. Has anyone checked that an M54 is totally stable with a K300? It doesn't seem long enough to be concerned about coning, but something is problematic.

It seems possible that it is also a heating problem from the long-burn motor. Does that seem possible? Does Magnaframe weaken at elevated temperature?

The flyer in question is rebuilding his M54 from a new kit but replacing the magnaframe with good ole-fashioned PML phenolic.

 

[daveyfire]

15 minute epoxy has a PSI rating of 5,000+ and magnaframe has the same PSI as 15 minute epoxy.. If 15 minute epoxy can survive then so can the magnaframe.

Based on this statement, I'm not sure you understand what a PSI is. (cite)

Sidebar: sometimes I feel like I'm turning into a curmudgeon. In the words of John Carmack, "ugh. A decade of experience and I'm turning into Bill Claybaugh." (Who is THE MAN, btw.)

 

[CCotner]

I understand the improbability of the damage; from HPR materials' average data on magnaframe, I estimate about 9kN of axial load for crush, and drag force at mach transition an order of magnitude lower than that. However, the actual failure is exactly what I described. You observe that the phenolic layers in the magnaframe failed first; I have always been incredibly wary of magnaframe because the phenolic layers should have much higher stiffness than the vulcanized fiber layers. This will cause any sort of bending load to be carried almost exclusively by the phenolic layers until they suffer a brittle failure, at which point the tube will strain further but not will be following the vulcanized fiber stress-strain curve, and will fail easily because it is so flexible. At least, that is my analysis. 'Composite' materials that aren't pseudo-homogeneous (like fiberglass, the resin bears no load, it's basically all fiber with resin in shear between fibers) (instead think about magnaframe, with bulk regions composed of vulcanized fiber or phenolic) need to have constituents with similar stress-strain curves to function effectively.

A similar problem arises in those beautiful carbon-fiber kevlar hybrid cloths; if kevlar and carbon fiber are parallel and under loading together, the kevlar will contribute very little strength until after the carbon fiber has failed, because the bulk material will strain at the rate dictated by the stiffest material.


Yes, I'm oversimplifying a little bit, but when the materials have drastically different stress-strain curves, it makes a big difference.

 

[blackjack2564]

It is not possible for the tube to be crushed under the load.

I was about to post this : Max Q + windshear+ flutter =op: when I kinda figured you[David] might show up...so I checked before pushing the button.....and there you were!

Sidebar: sometimes I feel like I'm turning into a curmudgeon. In the words of John Carmack, "ugh. A decade of experience and I'm turning into Bill Claybaugh." (Who is THE MAN, btw.)

No your not turning into a curmudgeon, your just tired of statements with a total lack of knowledge & no aspiration for it. I'm beginning to feel the same way. We've learned a lot the hard way & trying to save some others the bumps & disappointments we've known along the way. Hence the op: Sit back & watch, who knows even a blind knife thrower gets lucky every now & then.

 

[troj]

Based on this statement, I'm not sure you understand what a PSI is. (cite)

Sidebar: sometimes I feel like I'm turning into a curmudgeon. In the words of John Carmack, "ugh. A decade of experience and I'm turning into Bill Claybaugh." (Who is THE MAN, btw.)

David, there's a lot to be said for working to dispel the myths within the hobby

The more we all learn, the better off we all are

I'll be the first to admit, Physics gives me a headache, and I have no clue how to apply epoxy strength data to our hobby, or to this context. I need the Dick & Jane version

 

[CCotner]

I'll refrain from further technical posts, if they are going to be so unpopular.

 

[CarVac]

That is exactly the mindset that perpetuates the lack of technical discussion. Unfortunately, I have nothing further to add because I agree with your conclusion.

 

[jsargevt]

Experience teaches only the teachable. -Aldous Huxley

CJ, David and everyone else, keep talking and being "curmudgeons". Some of us listen as best we can. There comes a time when we need to test our theories to see if experience and conventional wisdom can't be altered into a new reality. Therefore, each person needs the opportunity to succeed or to fail on their own so they can see the truth that comes from experience.

 

[CarVac]

I think enough is in order. Like blackjack said, sit back and watch . I appreciate all your concerns and all the knowledge being presented. I want no one to feel that I am being discouraged. I am going all out and it will help me learn on what to expect next time I do something like this.

Like I wrote earlier, good luck. Hopefully that one failure was a case of a defective tube or something.

 

[CCotner]

May I ask a different question? I'm curious what you're using for deployment, and what kind of data it will record.

 

[CarVac]

How does your theory explain the failure in perfectly straight flight at the mach transition? I suppose that other successful mach+ flights were not any less stressful, and the straight flight would make your angle-of-attack theory mostly invalid. Please elaborate as to why a defective tube does not better explain what happened.

 

[CarVac]

If a tube is flying sideways, the center will actually have more drag because air can "slip" around the ends. A nosecone has even less resistance because it is skinnier.The majority of the forces will come from the fins, which will only try to make the rocket point in the direction of flight.

The burn marks are not on the nose and fincan because they are at the ends of the tube, but because they face forward. The air literally running into the forward facing surfaces are compressed by its momentum and heats up.

Furthermore, the flight was straight. Thus, it could not possibly have snapped for the reasons you described, which all involve flying sideways. However, you make a good point that the vent hole could have been the origin of the failure.

 

[CarVac]

But. It. Flew. Straight. My professor's flight did not take a turn at takeoff, and thus did not experience much bending moment. Therefore the failure had to have come from some reason other than it flying with an angle of attack.

If flynfrog's Mariah had flown straight, the scorching would have been in the same place.

 

[Aksrockets]

It wasn't that crazy of an angle. In the frame you took of my video, the rocket's angle was before it straightened out a moment later.
Alexander, if your theory is correct, makes you so sure yours will be perfectly straight?

[YOUTUBE]bfXzdSMrVHk
[/YOUTUBE]

I wouldnt be taking my chances. If I was flying a minimum diameter L motor. I would use G12 or Carbon.

Alex

 

[flynfrog]

Sinful, Im not 100% sure that the coupler will help it might just break in front of the coupler if it does let go the 6xl case stiffens up the rear of the rocket pretty well the brake was right in front for the motor mount. The entire surface of my rocket was scorched the peeled spot on the nose cone could have just been bad paint adhesion. I plan to take another crack at 20k this year with a l640dt. If I had to guess I would say the air frame was slightly under-stable and got into an oscillation so any stiffening of the tube will help this.

 

[bobkrech]

For what it matters, the M54 in question buckled along the spiral tube, immediately above the motor tube, right at the mach transition point in the flight. No deployment charges were fired during the flight. It appears that after buckling the top tube was damaged further, while the fincan was found intact. The flight appeared to multiple observers (in different positions) to be dead-on straight; the onboard baro altimeter recorded no detectable deviation from a straight flight given the atmospheric conditions, no other onboard data was recorded. I don't think there was any asymmetric flow contributing to the failure; it looks like it was a straight-up axial crush.

Also, as a side note, a rocket not going straight (arcing during burn, for instance) does not experience unusual mach behavior or forces. A rocket will only experience bending loads in flight if it is slightly unstable, or is coning or experiencing some other dynamic phenomenon. Has anyone checked that an M54 is totally stable with a K300? It doesn't seem long enough to be concerned about coning, but something is problematic.

It seems possible that it is also a heating problem from the long-burn motor. Does that seem possible? Does Magnaframe weaken at elevated temperature?

The flyer in question is rebuilding his M54 from a new kit but replacing the magnaframe with good ole-fashioned PML phenolic.

It is not possible for the tube to be crushed under the load. 15 minute epoxy has a PSI rating of 5,000+ and magnaframe has the same PSI as 15 minute epoxy.. If 15 minute epoxy can survive then so can the magnaframe. As for the flier rebuilding his M54 he should reinforce the phenolic with glass because from what I have been noticing it is the phenolic layer in the magnaframe that fails not the grey layer. These tubes are strong and I enjoy using them.

SinfulDarkLord needs to do some homework. CCotner is correct, however the occurrence of buckling at the Mach transition is just coincidental.

Column buckling failure of airframes is a well understood phenomenon, but not by the weekend launcher. It happens more than you think and a good example is the TRF archive reference below to a LOC Weasel column buckling failure on a Cesaroni I-540 at NERRF 3 that I analyzed for Boris Katan.

https://www.rocketryforumarchive.com/showthread.php?t=45337

Aeroelastic loads cause vibrations in the airframe which couple with the aerodynamic pressure loads and inertial loads created by high thrust motors to create a buckling failure in a minimum diameter airframe at the top of the motor casing which acts as a stress concentrator. The failure occurs with the top of the rocket folding over and being ripped off by aerodynamic forces.

Airframe column buckling failure is due to high velocity dynamic pressure loading and/or high acceleration inertial loading of a vibrating airframe and is due to a lack of airframe stiffness, not a high angle of attack. It is prevented by stiffening the airframe by inserting a full length coupler inside the airframe to stiffen it, or by wrapping the airframe with FG or carbon.

Bob

 

[CCotner]

SinfulDarkLord needs to do some homework. CCotner is correct, however the occurrence of buckling at the Mach transition is just coincidental.

Column buckling failure of airframes is a well understood phenomenon, but not by the weekend launcher. It happens more than you think and a good example is the TRF archive reference below to a LOC Weasel column buckling failure on a Cesaroni I-540 at NERRF 3 that I analyzed for Boris Katan.

https://www.rocketryforumarchive.com/showthread.php?t=45337

Aeroelastic loads cause vibrations in the airframe which couple with the aerodynamic pressure loads and inertial loads created by high thrust motors to create a buckling failure in a minimum diameter airframe at the top of the motor casing which acts as a stress concentrator. The failure occurs with the top of the rocket folding over and being ripped off by aerodynamic forces.

Airframe column buckling failure is due to high velocity dynamic pressure loading and/or high acceleration inertial loading of a vibrating airframe and is due to a lack of airframe stiffness, not a high angle of attack. It is prevented by stiffening the airframe by inserting a full length coupler inside the airframe to stiffen it, or by wrapping the airframe with FG or carbon.

Bob

That makes a ton of sense, thank you. I was trying myself to to figure out how the failure could have occurred, because the straight-up drag force was no where near enough to buckle the tube. I need to teach myself a good way to model that kind of behavior for my N5800. Bob, do you have a good resource? A quick look through the index of Anderson's compressible flow textbook didn't turn anything up. I have access to Ansys Fluent but am in the infant steps of teaching myself how to use it.