# Bonding Fiberglass and Quantum Tubing

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#### Kruegon

##### Well-Known Member
I recently acquired a PML AMRAAM-4 that was preowned. It wasn't built well. I removed all 8 fins, bare handed, with zero damage to the tube or fins. Yeah. Built real well.

It was also built stock. No a/v bay. Used the piston. Not really my style. I've stripped it down to parts. I'll be ordering the CRs, coupler, and MMT shortly. A little clean up on some epoxy residue and she'll be ready to go back together.

Now I want mine much better constructed. Quality isn't going to be an issue. Bonding may be. What's the best way to bond the G10 and wood CRs to the quantum tubing?

#### Rex R

##### LV2
pretty standard routine, wash with Hot soapy water(fg & quantum tube), and rinse. using 60 - 80 grit sand paper scratch up the bonding areas, rinse the residue off the parts, when dry epoxy. I will note that pml says to use 'jb weld steel' to bond their rail guides(urethane) in place.
Rex

#### Kruegon

##### Well-Known Member
Well I've never worked with quantum tubing or fiberglass before. So I had no idea how to start lol.

I'll be using 1010 rail buttons with T-nuts on this one. The a/v bay is going to be the interesting part of this one. Considering the forward fin placement.

#### dixontj93060

##### Well-Known Member
Not a fan of Quantum Tube. Personally I'd use the plastic epoxies available from Loctite and others to assure a solid bond.

#### manixFan

##### Not a rocket scientist
When I started I built a lot of PML kits. If you do as Rex suggests you'll be fine. I used System3 epoxy with plastic mini-fibers as filler and it's held up very well. My Tiny Pterodactyl has over 30 flights in about 15 years.

But the larger tubing does not age well. Some tubes that have been kept in a Texas garage have showed signs of deformation and debonding from clear epoxy (not my kits - ones I acquired in a 'garage sale'). If you've already gone to all that trouble I would highly recommend you buy standard 4" tube and use that instead of the QT. You'll never regret using standard tubing but the same may not be true of the QT.

For me QT was a great way to get started - it was easy to work with, it looked great with very little effort, and the PML kits are well designed with good instructions. But you are way past that so I think it's time to move beyond the QT as well.

Good luck,

Tony

#### Steve Shannon

##### Well-Known Member
TRF Supporter
Quantum Tube is very tough (until it sometimes spontaneously splits) and should be prepared exactly like Rex R says.
I've had QT tubes collect core samples and survive unscathed. I've also had one crack and split upon landing softly for no apparent reason. The flex in the material makes them a poor choice for Mach transitions unless you reinforce them internally and replace the PML phenolic coupler with something tougher. The QT itself didn't break when I flew a Sudden Rush on a v-max K, but the coupler broke, resulting in an explosive early deployment of the main at LDRS 27. I've heard it's on a video, but I've not seen it.

#### Kruegon

##### Well-Known Member
I picked up the kit for $25.00. I figure I can have her 100% flight ready for around$25.00 more. It's a heck of a deal otherwise I wouldn't have grabbed it up. For now it's simply a cheap way to get another 4" kit in my fleet. Be day soon I'll be building a true scale 4" of this missile. Till then, this one will get me by.

#### manixFan

##### Not a rocket scientist
One last suggestion then for the MMT. I glued some 80 grit sand paper to a PVC pipe coupler that I then stuck over a long dowel. I used that to scuff up the inside of the QT where the forward MMT centering ring will be glued. Filled epoxy (with a structural filler) seems to work better than regular epoxy as of course there is no penetration of the epoxy into the QT. As I mentioned I used the plastic mini-fibers which create a tough yet flexible joint which think is important with QT which does expand a lot in heat. I've not had any fin issues in normal flight activity.

No doubt the best thing about QT is how easy it is to get a good looking finish. I sometimes miss using it for that reason.

Good luck and post a pic when you are done. I have AMRAAMs in sizes from Estes to 6", including several of the PML versions - they are great looking rockets.

Tony

#### Kruegon

##### Well-Known Member
I can't wait to design out a true scale version. Tail cone, aft set fins, and even the beveling. Ah one day. That one will be glassed standard tubing though. And possibly 75mm in a 4" airframe.

#### markkoelsch

##### Well-Known Member
You could replace the QT with Phenolic. No bonding issues.

#### Kruegon

##### Well-Known Member
You could replace the QT with Phenolic. No bonding issues.
That is true, but there is the whole cost thing. I'd be pretty much just salvaging the fins at that point. I've been considering the design. The MMT is phenolic. Should be zero issues bonding the root edge. Internal fillets to both the to both the MMT and the inside tube should be very strong. I mean bonding to the g10 fins won't be an issue. Once the internal fillets are done, what are the actual odds of the fun pulling through? Then JB Weld fillets outside.

All of this took some consideration from the info given here and and my own googling. And on my budget, it's not like I'll be transitioning through Mach. At least not anytime soon.

#### markkoelsch

##### Well-Known Member
That is true, but there is the whole cost thing. I'd be pretty much just salvaging the fins at that point. I've been considering the design. The MMT is phenolic. Should be zero issues bonding the root edge. Internal fillets to both the to both the MMT and the inside tube should be very strong. I mean bonding to the g10 fins won't be an issue. Once the internal fillets are done, what are the actual odds of the fun pulling through? Then JB Weld fillets outside.

All of this took some consideration from the info given here and and my own googling. And on my budget, it's not like I'll be transitioning through Mach. At least not anytime soon.
I have run phenolic through Mach. Probably get it for 20-30 dollars.

#### MaxQ

##### Tripoli 2747
Coincidently, I am working on a PML Quantum Leap that I purchased years ago.
When the kit arrived at the launch site it was the Q tube version - not the phenolic version I had hoped for, but the vendor had it there, so I took it.

It sat in my shop while I pondered three things - 1.) the inherent limitations of the Quantum tubing, 2.) the limitations on motor choice if I used the "kwik switch" motor mounts that came with the kit and 3.) Those flimsy thin G10 fins
I ditched the piston before I did anything...given the temp effect I observed on just the couplers that came with the kit.

Based on reports from those that used the stock tubing, I decided not to spend the money replacing the body tubes with phenolic, and use the quantum tubes for fiber glassing.
I wanted to do two stage sport flights, and did not plan on going Mach with this kit, since the "kwik switch" motor mounts limit motor length - ie. the "kwik switch" motor mounts won't allow using really big motors longer than 13.75 ".

Since the quick switch motor mount lengths limit me in motor length motors in 29mm, 39mm (and 54mm w/o the kwik switch motor adapters), I won't be flying the large motors from K on up - but I still have my choice of over 50 different motors from H, I, and J (and that is just in the Aerotech line alone).

What I am doing is reinforcing the wimpy G10 fins and fin cans on the QT:
-I used West Systems microlite filler with epoxy to lay in heavy fin fillets at the fins roots which are through the wall mounted.
-then tip to tip FG on the fins after sanding the QT surface with heavy grit 80 through 120.
The fin fillets are real solid, but the fins were subject to flexing near the tip.....until I did the TTT FG.
After curing for a week, it appears to be holding just fine on the Quantum Tube.

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#### WILDMANRS

TRF Supporter
Coincidently, I am working on a PML Quantum Leap that I purchased years ago.
When the kit arrived at the launch site it was the Q tube version - not the phenolic version I had hoped for, but the vendor had it there, so I took it.

It sat in my shop while I pondered three things - 1.) the inherent limitations of the Quantum tubing, 2.) the limitations on motor choice if I used the "kwik switch" motor mounts that came with the kit and 3.) Those flimsy thin G10 fins
I ditched the piston before I did anything...given the temp effect I observed on just the couplers that came with the kit.

Based on reports from those that used the stock tubing, I decided not to spend the money replacing the body tubes with phenolic, and use the quantum tubes for fiber glassing.
I wanted to do two stage sport flights, and did not plan on going Mach with this kit, since the "kwik switch" motor mounts limit motor length - ie. using really big motors longer than 13.75 ".

Since the quick switch motor mount lengths limit me in motor length motors in 29mm, 39mm (and 54mm w/o the kwik switch motor adapters), I won't be flying the large motors from K on up - but I still have my choice of over 50 different motors from H, I, and J (and that is just in the Aerotech line alone).

What I am doing is reinforcing the wimpy G10 fins and fin cans on the QT:
-I used West Systems microlite filler with epoxy to lay in heavy fin fillets at the fins roots which are through the wall mounted.
-then tip to tip FG on the fins after sanding the QT surface with heavy grit 80 through 120.
The fin fillets are real solid, but the fins were subject to flexing near the tip.....until I did the TTT FG.
After curing for a week, it appears to be holding just fine on the Quantum Tube.
DO not bring that rocket out in the cold weather.
The quantum will shrink and the fiberglass will not

#### EeebeeE

##### Well-Known Member
Not a fan of QT. Why build rockets that inherently have a speed limit?

My suggestion...Now that you have the fins off, the nose cone apart, etc. save yourself the hassle and get a different airframe. Plus if the fins were that easy to remove, chances are the motor mount shouldn't be much harder. Yank that sucker out of there. You can use the QT as PVC for your toilet. Buy some FG airframe for those FG fins and let that rocket loose!

#### MaxQ

##### Tripoli 2747
DO not bring that rocket out in the cold weather.
The quantum will shrink and the fiberglass will not
Hey Tim...thanks for the advice... most of my flying is at southern launches /not in winter, but I'll keep that in mind.
That said, will that shrinkage factor for QT in cold weather affect an epoxy bonded part to QT - as well as any fiberglass layer to QT??
If so , PML should add that to their cautionary notes on QT, just like their build it strong cautionary notes on their suggested motor list for their QT kits on their website.

And I suspect we will all want a clarification and consensus of the temperature range for "cold weather" ...some of you northern and mid western guys have a different take on what cold weather really is, my uncle in Chicago would go out in the dead of winter with a light jacket and laugh at me in my parka.

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#### MaxQ

##### Tripoli 2747
Not a fan of QT. Why build rockets that inherently have a speed limit?
Because some rockets are intentionally built not to go fast, ever.
For instance, nothing looks sillier to me than a scale rocket project that never went fast to begin with in real life, going close to Mach speed on lift off.
Granted, some actually did, like an ABM Sprint. Some did not.

There are projects that just need to go fast enough to be stable off the rod, and also activate a G switch for electronics.
And some people just really like slow take offs, the original Big Bertha was very popular for that reason.

I have a CHAD two stage that is lots of fun with a slow take off, right before it launches the second stage abruptly...I can't fly it in strong winds, but on a mild day it is a hoot.

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#### Rex R

##### LV2
and some places are not well suited for altitudes over say 5k AGL. Woosh defines cold as anything under 20F we don't launch (as a club) under 16F . I set up my pml BB with that in mind.
Rex