Had no idea quantum tube was so brittle.

[ClarkusAurelius]

That statement doesn’t match my experience. I’ve flown PML QT supersonic many times. Once I even had a shred with a 3” QT PML rocket flying on a K2045, but it wasn’t the QT that broke, it was the phenolic coupler that failed when the QT flexed. Blew every panel out of the chute and sheared some pieces off the altimeter, but the QT survived just fine. Fins all stayed attached (in fact they’re still attached). Motor retention had no problems. The weak point was the phenolic coupler, but the flexing of the QT started it.
I have taken core samples with QT also where I was able to knock the dirt out of the body tube and fly it again. It can be very resilient. But it’s not resilient when it’s cold and it doesn’t always fail predictably . I once had a soft landing in cool (but certainly not frigid) temps where a crack propagated right up the side of a QT rocket that had flown for years with no problems. It was rocky ground.
No tube material is perfect. Each has its own strengths and weaknesses.
Learning to deal with the expansion and contraction of QT and phenolic pistons was just a rite of passage.

Were you able to repair it? Or was it time for retirement? I have 12 inch zipper in my 4inch LOC from my chute coming out at 25 feet. Wondering if I can epoxy it back together. Read in another thread that QT should not be repaired but I’m not entirely sure. This is my first mid power rocket and it’s got a few mistakes on it that make me hesitant to fly it on anything over a G so no serious stress on it.

 

[JackC]

Were you able to repair it? Or was it time for retirement? I have 12 inch zipper in my 4inch LOC from my chute coming out at 25 feet. Wondering if I can epoxy it back together. Read in another thread that QT should not be repaired but I’m not entirely sure. This is my first mid power rocket and it’s got a few mistakes on it that make me hesitant to fly it on anything over a G so no serious stress on it.

If it’s LOC cardboard, the best thing to do is cut the tube an inch or so below the zipper then use a coupler tube to join a new section of another cardboard tube to replace the damaged section.

 

[Steve Shannon]

Were you able to repair it? Or was it time for retirement? I have 12 inch zipper in my 4inch LOC from my chute coming out at 25 feet. Wondering if I can epoxy it back together. Read in another thread that QT should not be repaired but I’m not entirely sure. This is my first mid power rocket and it’s got a few mistakes on it that make me hesitant to fly it on anything over a G so no serious stress on it.

If it’s cracked or broken Quantum Tube just replace the tube. If if cardboard, g10, or glasses phenolic and a small hole then you can repair. Large zippers are best fixed by replacing the zippered portion.
I replaced the phenolic coupler with a G10 coupler but it was so tight that when the tube got cold the QT started splitting. It’s sitting in the procrastination pile now.

 

[C.O.B.H.C.]

I have a Q-Tube PML Phobos that is over 10 years with probably well over 50 flights on it ranging from G to I motors. It's still flying strong. Only the piston has a few chips in it. I've also sanded the piston to fit so many times now it just drops freely down the airframe.
I also have a Q-Tube PML Miranda that I somehow forgot to attach or close the quick link to the parachute to and it fell from 2K with out a parachute and landed on grassy field with no damage.

 

[Steve Shannon]

I have a Q-Tube PML Phobos that is over 10 years with probably well over 50 flights on it ranging from G to I motors. It's still flying strong. Only the piston has a few chips in it. I've also sanded the piston to fit so many times now it just drops freely down the airframe.
I also have a Q-Tube PML Miranda that I somehow forgot to attach or close the quick link to the parachute to and it fell from 2K with out a parachute and landed on grassy field with no damage.

I've posted it before (maybe even in this thread) but I've done a ballistic core-sample with QT that would have destroyed cardboard or phenolic. I've also had one come down under chute and hit a rock on a cool (50°) day and develop a crack that ran three quarters of the length. It's much stronger than its detractors give it credit for, but it has its limitations. A person just has to learn them and fly around them. I like it.

 

[JackC]

I've posted it before (maybe even in this thread) but I've done a ballistic core-sample with QT that would have destroyed cardboard or phenolic. I've also had one come down under chute and hit a rock on a cool (50°) day and develop a crack that ran three quarters of the length. It's much stronger than its detractors give it credit for, but it has its limitations. A person just has to learn them and fly around them. I like it.

“A rocket has got to know its limitations!”