What Can This Survive?

[Kruegon]

I've acquired another used/rebuild. PML AMRAAM 4. Its quantum tubing with G10 fins. The aft fins are full length ttw. The forward canards are semi ttw. They were designed to go through the airframe and attach to the coupler.

I want an a/v bay. My plan is to wax paper wrap a coupler and insert it into the payload section. Then I'll put epoxy into the slots and set the fins. Afterwards they'll receive external fillets and the inside of the tube will be smoothed for the coupler to slide in and out as a removable a/v bay.

Assuming I prep the surface properly, and I use a quality epoxy, how much stress would you think it could survive? Could it survive Mach 1? Maybe 1.5? I really want to test this things limits without shredding it. How far would you be willing to push it?

 

[tim cubbedge]

PML fins are pretty thin so if it's a stock kit, probably not Mach. I believe they even mention on their website that quantum tubing is not designed for Mach.

 

[jd2cylman]

I thought PML said that Quantum tube was not good for over Mach? Maybe check the PML FAQ? That being said, I have a PML Endeavour that I've flown the crap out of but I don't remember the highest thrust motor I've used. A K805G for sure. I think I can only fit the 1706 case so far. One of these days I gotta smash out the quick change adapter to see if the 2560 will fit.

 

[tim cubbedge]

https://publicmissiles.com/product/airframes

 

[Rex R]

iirc pml lists a do not exceed speed of 900 fps for quantum tubing it is too flexible.
Rex

 

[Kruegon]

Well that sucks. This is the first time I've played with anything from PML. I was hoping it was noticeably stronger than cardboard.

 

[blackjack2564]

We have deconstructed these on K-1100's!


You may have a chance if you can line the entire rocket with couplers, but why force it.

It's a sport flier.

They make them with phenolic airframes, so you can glass them for high stress flights.

 

[dixontj93060]

+1 to what everyone has said.

QT=rubbery plastic=beware!

 

[MaxQ]

PML fins are pretty thin so if it's a stock kit, probably not Mach. I believe they even mention on their website that quantum tubing is not designed for Mach.

I have an old PML Quantum Leap kit - the airframe was QT - the G10 fins were so thin they flexed in my hand.
I intended to replace everything but finally decided to build it as is w/ the QT to get a rocket done and have more launch options - so I did a tip to tip FG on the fins on both the booster and sustainer, and it stiffened them up.

I've noticed in very cold air temps the QT seizes up on the phenolic couplers. I won't risk an internal piston.
I do not intend to fly this in cold weather, or beyond specs.
Meant as a spring/summer "fun flyer" for 2 stage flights.

I'll let you know how it goes.

 

[Steve Shannon]

I've had a Quantum tube rocket shred on a vmax 54mm K motor. What happened (my opinion) was the phenolic coupler shredded as the rocket came back down from supersonic. The Quantum Tube body tube was just fine, but the coupler shredded because the Quantum Tube flexed, got a little sideways, and snapped the coupler. That resulted in the main being thrown out at apogee, which blew out some panels.
I wouldn't use Quantum Tube to build a supersonic flyer again, but I think it's great for subsonic flights.


Steve Shannon

 

[heada]

I flew my stock PML QT AMRAAM4 on a J415 without issue for my L2. Tried a K1275 later and it reassembled itself at mach due to the altimeter deploying the ' chute, not a QT failure (I forgot to set a mach delay) Biggest issue with QT airframes is the temp based cycling. When its warm, it really expands and couplers will stick. When its cold, it shrinks and gets brittle and you have to add lots of tape to the coupler.

Fly it and have fun.

-Aaron

 

[Kruegon]

Well as I pointed out, it's a rebuild. I got it for $25.00 from a friend. He got it for $50.00 from someone I don't know. He stripped out the recovery parts and sold the shell to me.

Whomever owned it, didn't sand the tube or fins. For unknown reasons, they cut the sustainer tube in half and put it back together with a coupler. Obviously, nothing was bonded well.

I cut the sections back apart and removed the coupler, piston, and motor mount. Custom cut new 4"x54mm centering rings. Stripped the fins of their epoxy. Cleaned out the inside of the tubes. Ordered two now couplers and a set of decals.

I'll be rebuilding this one starting in a few days. There's still a little prep left, but I'm very close to ready to assemble. It's going to be interesting. This will be my first experience with QT and FG. I just need to settle on what epoxy to use. I'm thinking that staying with what I already know may be my best option. Though it may not be the best choice.

 

[MaxQ]

I flew my stock PML QT AMRAAM4 on a J415 without issue for my L2. Tried a K1275 later and it reassembled itself at mach due to the altimeter deploying the ' chute, not a QT failure (I forgot to set a mach delay) Biggest issue with QT airframes is the temp based cycling. When its warm, it really expands and couplers will stick. When its cold, it shrinks and gets brittle and you have to add lots of tape to the coupler.
-Aaron

QT - "When its warm, it really expands and couplers will stick."

Wouldn't that actually be the case "when it gets cold, and it shrinks"....?

When the QT shrinks around the coupler - it sticks, when the QT expands - it would seem to me to be a loser fit.

 

[Kruegon]

QT - "When its warm, it really expands and couplers will stick."

Wouldn't that actually be the case "when it gets cold, and it shrinks"....?

When the QT shrinks around the coupler - it sticks, when the QT expands - it would seem to me to be a loser fit.

That was my thought. I assumed they just got it backwards.

 

[heada]

It can expand and contract not just in wall thickness but also in over-all size. When warm, the wall thickness expands but so does the total ID/OD of the tube via radial expansion. Same for shrinking when cold. My personal experience is that when it expands, it tends to expand more on the wall thickness and not as much on the ID/OD. Therefore, with expansion, things get tighter. The inverse is true for contraction via cold. Again, my personal experience based on very hot, humid summers and very cold, dry winters in the midwest.

Test all your joints before flight and adjust accordingly.

-Aaron

 

[Handeman]

......
Test all your joints before flight and adjust accordingly.

-Aaron

+1 on that. We fly Oct to Apr so I only had issues with cold. The colder it got, the tighter the piston. But, once it's sanded down to work in a cold temp, it is always good down to that temp.