38mm carbon tubes

[Adrian A]

I'm in the market for some thin-wall 38mm carbon fiber tubing for a minimum-diameter build. In the past I have rolled my own, but I'd rather buy professionally made tubing if an appropriate layup is used and the wall isn't too thick. I thought I found just what I was looking for here:

https://www.rockwestcomposites.com/45635
but I didn't do my homework and it turns out that 1.500" ID isn't large enough to work with 38mm motors. D'oh!

The tube is nice and stiff and very light, with only a 0.035 wall and just 56 grams per foot. All the plies are unidirectional and most of the fibers are in the axial direction, for good bending stiffness.

Can anyone recommend a source for a tube like this with 1.51" or 1.52" ID rather than 1.500? I know there are several rocketry vendors with filament-wound, thick-wall carbon tubing, but lighter weight with a more optimal layup is what would make me happy.

 

[rfjustin]

@REK for visibility here.

 

[REK]

I'm in the market for some thin-wall 38mm carbon fiber tubing for a minimum-diameter build. In the past I have rolled my own, but I'd rather buy professionally made tubing if an appropriate layup is used and the wall isn't too thick. I thought I found just what I was looking for here:

https://www.rockwestcomposites.com/45635
but I didn't do my homework and it turns out that 1.500" ID isn't large enough to work with 38mm motors. D'oh!

The tube is nice and stiff and very light, with only a 0.035 wall and just 56 grams per foot. All the plies are unidirectional and most of the fibers are in the axial direction, for good bending stiffness.

Can anyone recommend a source for a tube like this with 1.51" or 1.52" ID rather than 1.500? I know there are several rocketry vendors with filament-wound, thick-wall carbon tubing, but lighter weight with a more optimal layup is what would make me happy.

I would like to make you one, but I am limited to 50”, will this work out for you?

 

[Adrian A]

50 " would be great.


If I could choose any layup, I would choose a ply of uni 90 degrees (hoop direction) on the inside and outside, and everything in between would be 0 (axial), up to a total wall thickness of 0.035". If you need to use cloth, then hopefully you could still do that with 0/90 orientation on the inside and outside layers with 0" uni in between.

 

[jpoehlman]

Looks like Robert at Buy Rocket motors just released close to what you are looking for 54mm - Carbon Fiber Airframes Standard (buyrocketmotors.com) lengths to 5 feet.

 

[manixFan]

Looks like Robert at Buy Rocket motors just released close to what you are looking for 54mm - Carbon Fiber Airframes Standard (buyrocketmotors.com) lengths to 5 feet.

38mm≠54mm


Tony

 

[REK]

50 " would be great.


If I could choose any layup, I would choose a ply of uni 90 degrees (hoop direction) on the inside and outside, and everything in between would be 0 (axial), up to a total wall thickness of 0.035". If you need to use cloth, then hopefully you could still do that with 0/90 orientation on the inside and outside layers with 0" uni in between.

I can most certainly do this, I’ll have it made this Sunday.

 

[Adrian A]

The tube came out great! The layup had 90 degree plies on the inner and outer diameter, and the rest of the plies are axial. The axial plies are effective anywhere in the layup, because their leverage comes from the 1.5" diameter. Putting the 90 degree plies on the inner and outer diameter layers maximizes the effectiveness of those plies for resisting tube crushing, because they get their leverage from the 0.035" wall thickness. The result is that the tube is much more crush-resistant than the Rockwest tube I bought, which for some reason put the 90 degree plies in the middle.

With these unidirectional plies, 0.04" wall thickness seems like it's plenty for a durable 38mm tube.

Alexander's quality looks perfect, and the carbon has that great ring to it that tells you it's a high-quality layup with the right resin content.

 

[rfjustin]

Always good to heart such positive feedback!

 

[manixFan]

The tube came out great! The layup had 90 degree plies on the inner and outer diameter, and the rest of the plies are axial. The axial plies are effective anywhere in the layup, because their leverage comes from the 1.5" diameter. Putting the 90 degree plies on the inner and outer diameter layers maximizes the effectiveness of those plies for resisting tube crushing, because they get their leverage from the 0.035" wall thickness. The result is that the tube is much more crush-resistant than the Rockwest tube I bought, which for some reason put the 90 degree plies in the middle.

With these unidirectional plies, 0.04" wall thickness seems like it's plenty for a durable 38mm tube.

Alexander's quality looks perfect, and the carbon has that great ring to it that tells you it's a high-quality layup with the right resin content.

Great to hear. I have one of the first 38mm tubes he made and it I was very happy with it for the price. I may need another one and good to know his layup meets your stamp of approval, knowing that you have been making small diameter rockets for a long time. On mine, the ID was tapered just a hair, so I used the smaller end for the motor and the other for the nosecone.

Maybe post some build pics as well - I've read through your 'Violent Agreement 2' PDF several times and learned a lot, and your technical analysis really sold me on the Raven flight computer. I really like seeing what seasoned flyers are doing.


Tony

 

[Adrian A]

Thanks, Tony. This tube will be going into a rocket with a standard dual-deploy configuration with innards that I'm designing for reliability. I'm also ordering another tube that I can use for a booster on a 3-stage minimum diameter 38mm flight I have in mind for BALLS next year. Keeping the back end as light as possible will help that one with performance and stability. I have a really strong and stiff 2nd stage that I made a long time ago that is still good as new, but the fins are a bit big, so it weathercocked a lot coming out of the tower at LDRS in Argonia a couple of years ago, resulting in a 6 mile recovery. I'll design the new booster for a little lower stack stability margin to give it a better chance of getting off to a more vertical start.

I do enjoy making build threads as I go along, and it slows me down enough to make better decisions sometimes, so I'll probably do a build thread for one or both of them. In the meantime I need to finish building out my shop in an alcove of my garage.