Questions about rolling carbon fiber tubes

The Rocketry Forum

Help Support The Rocketry Forum:

Neutron95

Well-Known Member
Joined
Jan 17, 2010
Messages
176
Reaction score
13
I have a few high performance designs on the horizon, so I figured it would be a good idea to learn how to make my own tubes. I also have an old midpower rocket built out of a bunch of BT-80 tubes that eventually had to be retired due to fatigue, so I'm going to clone it in carbon as a learning experience. I would appreciate it if some of the resident experts could review my ideas before I waste a bunch of money on a bunch of unsuccessful attempts.

For the mandrel, I'm planning on using a 48" section of 2.65" Blue Tube coupler wrapped in 5 mil mylar as shown in the Jim Jarvis guide to composite rockets. My main concern is the tube spirals. I'm thinking about applying compression, and I'm not sure if the pressure could cause the mylar to bulge down into the spiral grooves. I'll probably fill them just to be on the safe side.

For the actual materials, I'm planning on using the Soller Composites 3k 2x2 Twill, mostly because it's cheap enough that I can afford to screw up some tubes. I think that I can get away with just two layers as this will be a midpower sport flying rocket. I'm not quite sure what Aeropoxy laminating epoxy to use though. Jim recommends using the 3665 hardener with the 3032 resin, but he says that it requires an oven to set up. The data sheet says that it sets up at room temperature, so I don't know if it has been changed at all since the guide was written. I don't have an oven, and I don't want to have a tube that won't set up on my hands. I live in Southern California, so the weather should be warm enough to get it to set up.

My final quandry is how to get a good surface finish. Peel ply is the obvious answer, and I'll probably use that for the fin can, but it looks like it will take a lot of work to get a really good finish with it. I've seen some people on here get good results with mylar film and with the Soller Composites heat shrink tubing, and I'd like to use those if possible.
 

rharshberger

Well-Known Member
Joined
Oct 13, 2014
Messages
9,289
Reaction score
1,397
Location
Pasco, WA
I have a few high performance designs on the horizon, so I figured it would be a good idea to learn how to make my own tubes. I also have an old midpower rocket built out of a bunch of BT-80 tubes that eventually had to be retired due to fatigue, so I'm going to clone it in carbon as a learning experience. I would appreciate it if some of the resident experts could review my ideas before I waste a bunch of money on a bunch of unsuccessful attempts.

For the mandrel, I'm planning on using a 48" section of 2.65" Blue Tube coupler wrapped in 5 mil mylar as shown in the Jim Jarvis guide to composite rockets. My main concern is the tube spirals. I'm thinking about applying compression, and I'm not sure if the pressure could cause the mylar to bulge down into the spiral grooves. I'll probably fill them just to be on the safe side.

For the actual materials, I'm planning on using the Soller Composites 3k 2x2 Twill, mostly because it's cheap enough that I can afford to screw up some tubes. I think that I can get away with just two layers as this will be a midpower sport flying rocket. I'm not quite sure what Aeropoxy laminating epoxy to use though. Jim recommends using the 3665 hardener with the 3032 resin, but he says that it requires an oven to set up. The data sheet says that it sets up at room temperature, so I don't know if it has been changed at all since the guide was written. I don't have an oven, and I don't want to have a tube that won't set up on my hands. I live in Southern California, so the weather should be warm enough to get it to set up.

My final quandry is how to get a good surface finish. Peel ply is the obvious answer, and I'll probably use that for the fin can, but it looks like it will take a lot of work to get a really good finish with it. I've seen some people on here get good results with mylar film and with the Soller Composites heat shrink tubing, and I'd like to use those if possible.
For the exterior of the tube ditch the mylar film otherwise you will end up with many air pockets to fill or sand out later, so far all three of my attempts to use a mylar wrapper have ended badly. Mylar as a interior tube release is fine IMO, just make sure it can slide freely on the mandrel or getting it off will be a bear. John Coker and Tfish both have good videos on rolling your own tubes. Honestly unless you just have a specific niche need, a good custom filament would tube will be superior to a hand rolled tube, check with TRF'r @REK to see what he can offer. I use peel ply (not film) the real fabric type usually a coated nylon material or polyester, it leaves a cloudy finish but simply sand it and apply another coat of epoxy and....

Not tubes but, picture on the left straight of the bag with peel ply texture, picture on right another fin from the same stack on left with a fresh coat of epoxy without sanding. I do not vac bag my tubes as its a pain to get the wrinkles out of the bag and to prevent the tube getting squished even a little by the process.
20200501_205414.jpg20200501_205444.jpg
 

watheyak

Barnstormer
Joined
May 11, 2009
Messages
714
Reaction score
209
Location
Arizona
Getting a good finish without work is usually a pipe dream unless you're using a mold that already has a great finish. Nice, shiny raw carbon finishes take a lot of elbow grease. Like Rich posed above, the peel ply leaves a textured finish. The next steps involve coats of epoxy, much sanding and polishing. The "Jarvisonian Method". You either think it's worth it or you paint it. I'll never knock someone for painting a carbon rocket.

I also never vacuum bag tubes. The best "no work" finish I've gotten on a tube used a Soller carbon sock and their heat shrink tubing. I think I gave that one a light sanding and clear coated it. My only reservation is that I'm not sure how much compression their tube actually gives. Maybe a lot. Maybe not.

And these days I don't even make my own tubes, I just buy them from REK. They're nice!

Below is the elbow grease route. Curtis tubes, not REK.

d.jpg
 

JimJarvis50

Well-Known Member
Joined
Jan 18, 2009
Messages
2,358
Reaction score
544
Here are a few suggestions for simplifying the process.

First off, compression + mylar. For compression to be effective, you have to squeeze out the epoxy somewhere, normally into a breather material of some sort. The mylar just traps the epoxy rather than removing it. So, the normal result is just an uneven surface. Better is to apply some tension to the end of the cloth, but that won't work very well for only two wraps. I would say that for two wraps, you don't need compression.

You'll have plenty of working time with the 3660 hardener. There's a new one, 3663, that is supposed to provide more working time, but cures over the same duration as the 3660. I haven't used it, but it might be a good solution. The 3665 might claim to cure at room temperature, but it takes a long time. You really need an oven for it, although 90F is all you need.

Peel ply would be better than mylar. I have tried mylar in the past and found it very difficult to get good results. The key with peel ply is to make sure it is completely wetted out. You'll often see a ton of small bubbles under the peel ply. A very useful trick is to tap the surface of the peel ply with the tip of a chip brush. Just do the entire tube, hitting the entire surface with the tip of the brush. The bubbles will magically vanish, leaving a surface that is relatively easy to finish.

The peel ply surface can be finished by coating the tube once or twice with a very thin coat of epoxy, sanding that down reasonably smooth, and then wiping the tube once or twice with epoxy. With one or two coats, you can't eliminate all imperfections, but you can get close. Then, the epoxy wipe fills the sanding scratches and you end up with a pretty good finish. The idea is to put it on and then wipe off literally all of it with a cloth. You've gone far enough when the tube feels dry to the touch and not sticky. It's about 25% of the work of the full method, which is not nothing, but you get about 75% of the result. Most of the tubes I make are done this way, and they look fine.

Make sure your blue tube mandrel is straight. It's hard to get tubes that don't have a slight bend (although I have never used blue tube and maybe they'll be just fine). The sprials won't matter if you avoid compression.

Jim
 

Neutron95

Well-Known Member
Joined
Jan 17, 2010
Messages
176
Reaction score
13
Thanks for the advice Jim. I think that I'm comfortable enough with my process to start ordering materials now.
 

JohnCoker

Well-Known Member
Joined
Apr 13, 2013
Messages
1,676
Reaction score
316
Good luck with your tubes! It's nice to be able to make your own for special purposes, but it's hard to justify making standard sizes.

You're going to be working with a lot of epoxy over a significant amount of time so take precautions. I suggest wearing a respirator.
 

boatgeek

Well-Known Member
Joined
Dec 27, 2014
Messages
2,590
Reaction score
1,021
If you're not planning high Mach flights, you might want to price check marine laminating epoxies. West is popular. I personally like System 3 Silvertip, and there are no doubt others. They're made for the same purpose but aren't as heat-resistant. That doesn't really matter much if you're not going really fast.
 

Neutron95

Well-Known Member
Joined
Jan 17, 2010
Messages
176
Reaction score
13
If you're not planning high Mach flights, you might want to price check marine laminating epoxies. West is popular. I personally like System 3 Silvertip, and there are no doubt others. They're made for the same purpose but aren't as heat-resistant. That doesn't really matter much if you're not going really fast.
The eventual goal is to go as high and as fast as I can with 29mm motors. I'm still working on the sims, but the altitude shot will probably max out at around Mach 2.5. The stupid flight profile that maximizes velocity might get close to Mach 3.

If I get the 29mm two stage design working reliably, I might build a short 38mm booster for it and put the staged J record pretty high. But that is going to be a lot of work.
 

JohnCoker

Well-Known Member
Joined
Apr 13, 2013
Messages
1,676
Reaction score
316
The eventual goal is to go as high and as fast as I can with 29mm motors.
Smaller tubes are harder to do than larger ones, especially if you vacuum bag, because the wrinkles are harder to get out. I suggest not using too heavy a weight cloth and doing more layers of it.
 

Neutron95

Well-Known Member
Joined
Jan 17, 2010
Messages
176
Reaction score
13
Smaller tubes are harder to do than larger ones, especially if you vacuum bag, because the wrinkles are harder to get out. I suggest not using too heavy a weight cloth and doing more layers of it.
Thanks for the advice. The current iteration of the 29mm design has some very thin walled tubes. I'm expecting that this project is going to require a lot of trial and error before I eventually refine the design down to something that I can actually build, that will hit my altitude goals, and will fly and recover reliably. I'll be lucky to make a single piece of flight hardware before the end of the year.
 

REK

Sponsor
TRF Sponsor
Joined
Feb 21, 2012
Messages
2,713
Reaction score
22
I have a few high performance designs on the horizon, so I figured it would be a good idea to learn how to make my own tubes. I also have an old midpower rocket built out of a bunch of BT-80 tubes that eventually had to be retired due to fatigue, so I'm going to clone it in carbon as a learning experience. I would appreciate it if some of the resident experts could review my ideas before I waste a bunch of money on a bunch of unsuccessful attempts.

For the mandrel, I'm planning on using a 48" section of 2.65" Blue Tube coupler wrapped in 5 mil mylar as shown in the Jim Jarvis guide to composite rockets. My main concern is the tube spirals. I'm thinking about applying compression, and I'm not sure if the pressure could cause the mylar to bulge down into the spiral grooves. I'll probably fill them just to be on the safe side.
I don't recommend using 5 mil mylar for the fact that your tube's ID will be a lot larger than the already correct size of the coupler for the BT-80. I would go around 2 mil mylar or my preferred favorite "parchment paper", also parchment paper will allow for the tube to slide off easily (so long as the mandrel is not crooked). Do no worry about the tube spirals, also what sort of compression are you planning on? I would not recommend this, because then you will have a hard time removing the tube or most likely not be able to remove it at all.

For the actual materials, I'm planning on using the Soller Composites 3k 2x2 Twill, mostly because it's cheap enough that I can afford to screw up some tubes. I think that I can get away with just two layers as this will be a midpower sport flying rocket. I'm not quite sure what Aeropoxy laminating epoxy to use though. Jim recommends using the 3665 hardener with the 3032 resin, but he says that it requires an oven to set up. The data sheet says that it sets up at room temperature, so I don't know if it has been changed at all since the guide was written. I don't have an oven, and I don't want to have a tube that won't set up on my hands. I live in Southern California, so the weather should be warm enough to get it to set up.
Aeropoxy 3665 hardener says it will cure at room temperature, but after a quick chat with Aeropoxy on why a carbon tube of mine was still tacky after 24 hours, they revealed to me that it will cure at around 80 degrees F. An oven is indeed required for that hardener, unless it is hot as hell in your area. I've used the 3663 hardener and that one will cure at room temperature. The Adtech 820 resin system that Soller Composites sales is also a room temperature cure resin system. I have used it before and I will recommend it.

My final quandry is how to get a good surface finish. Peel ply is the obvious answer, and I'll probably use that for the fin can, but it looks like it will take a lot of work to get a really good finish with it. I've seen some people on here get good results with mylar film and with the Soller Composites heat shrink tubing, and I'd like to use those if possible.
No matter what you try and as others have pointed out, you will in the end up having to put in a little bit of elbow grease to get the best finish on your tube. I recommend going with peel ply, because it will be easier to sand down and acquire a good finish.

I hope this helps you in making a successful tube
 

Neutron95

Well-Known Member
Joined
Jan 17, 2010
Messages
176
Reaction score
13
I don't recommend using 5 mil mylar for the fact that your tube's ID will be a lot larger than the already correct size of the coupler for the BT-80. I would go around 2 mil mylar or my preferred favorite "parchment paper", also parchment paper will allow for the tube to slide off easily (so long as the mandrel is not crooked). Do no worry about the tube spirals, also what sort of compression are you planning on? I would not recommend this, because then you will have a hard time removing the tube or most likely not be able to remove it at all.
Thanks for the advice. I decided to just use peel ply and no compression. I will definitely give the parchment paper a shot.
 

REK

Sponsor
TRF Sponsor
Joined
Feb 21, 2012
Messages
2,713
Reaction score
22
Thanks for the advice. I decided to just use peel ply and no compression. I will definitely give the parchment paper a shot.
I recommend getting the parchment paper that shows two chocolate chip cookies, I don’t know if there are different brands in your area, but that one is the best one I’ve used.

Also, I recommend spiral wrapping the parchment paper with a 50% overlap. Trust me you don’t want to cut a huge peice to overlap the mandrel with.

One last thing, tape will hardly stick to this stuff, so when you spiral wrap the parchment paper, apply a ring or two of tape in order for it to lock in place at each end.
 

mpitfield

Moderator
Staff member
TRF Lifetime Supporter
Global Mod
Joined
Jul 7, 2013
Messages
4,813
Reaction score
416
Location
Toronto, Ontario
Just pointing out what is likely a typo "3032" resin, you mean 2032, correct?
 

cwbullet

Obsessed with Rocketry
Staff member
Administrator
TRF Lifetime Supporter
Global Mod
Joined
Jan 24, 2009
Messages
24,787
Reaction score
2,936
Location
Glennville, GA
CF sleeves are another way to go.
 

JimJarvis50

Well-Known Member
Joined
Jan 18, 2009
Messages
2,358
Reaction score
544
I have rolled single-wrap 29mm tubes that turned out well. I just a 1" dowel and that seems to give just the right size for the motors.

Way back when, I tried Mick Kelly's method of wrapping the tube in mylar and then heat shrink tape. I had lots of difficulty with it due to air bubbles and seams, and that dampened my enthusiasm for mylar. But I was wondering if it might not be possible to wrap a tube with very thin mylar. Maybe have the mylar in a U shape, set the tube on it and work out any air bubbles from the bottom up. At the top, just overlap the mylar a little, but no compression involved. I can sort of visualize this working.

Jim
 

Neutron95

Well-Known Member
Joined
Jan 17, 2010
Messages
176
Reaction score
13
I got the Blue Tube today. It has a bit of surface texture, so I'm going to give it a few rounds of sealing and sanding while I wait for the carbon and epoxy to arrive. It's also a very loose fit in the BT-80 tubes that I bought before deciding to switch to all composite construction. I'll probably use the 5 mil mylar film for the first tube to make up that slight difference.
 

Neutron95

Well-Known Member
Joined
Jan 17, 2010
Messages
176
Reaction score
13
After reading this thread, I decided to more accurately check the straightness of my coupler tubes. By rolling them on a glass table, and trying to slide a piece of paper underneath them at various points, I figured out that they were both slightly bent. I did notice that it didn't take a whole lot of pressure to flex the tube straight though. I bought a six foot length of aluminum tube, and I'm going to put centering rings on it at 3 inch intervals, and see if that straightens out the tube.

If that doesn't work, I'll probably try the first piece anyways. I figure that it probably won't be good enough to use in the final rocket, so it won't be a tragedy if I have to cut it off. I'm hopeful that since the bowing is very slight, I'll still be able to get the tube off. Worst case scenario, if both of the mandrels are unusable, I'll just throw a layer of carbon on the BT-80 tubes I already have, and call it good enough.
 

Latest posts

Top