Making Carbon Fibre Airframes - Coast Rocketry

I want to understand a little bit better the process of making carbon fibre airframes as I would like to do it for a scratch build I have planned.

I see Coast Rocketry sell mandrels, carbon fibre cloth & sleeves as well as heat shrink tubing.

https://www.coastrocketry.com/composites.htm

Can anyone give me a basic explanation as to how I go about making the tube with this method? I understand the basics of fibreglassing - epoxy and wrapping glass cloth round the mandrel - is it the same with carbon fibre? Or is a different bonding process required?

And what sort of results and performance should I expect? It is for a supersonic HPR

Luke said:

I want to understand a little bit better the process of making carbon fibre airframes as I would like to do it for a scratch build I have planned.

I see Coast Rocketry sell mandrels, carbon fibre cloth & sleeves as well as heat shrink tubing.

https://www.coastrocketry.com/composites.htm

Can anyone give me a basic explanation as to how I go about making the tube with this method? I understand the basics of fibreglassing - epoxy and wrapping glass cloth round the mandrel - is it the same with carbon fibre? Or is a different bonding process required?

And what sort of results and performance should I expect? It is for a supersonic HPR

Click to expand...

If you understand fiberglassing, then using carbon fiber is similar.

The main difference is that the cloth itself is stiffer, so while a thin FG cloth will stay flat around a mandrel without any compression, a CF cloth will be happy to peel itself off in an attempt to become straight again.

It's the same basic principle as fiberglass with a few slight differences. In my experience, CF cloth is usually slightly stiffer then FG cloth (depending on weight of course) so smaller tubing sizes are harder to work with. It's also harder to tell if the carbon fiber is wetted out or not. Fiberglass turns clear - carbon fiber just turns glossy. I also put quite a bit more work into the layups of my carbon fiber tubing if I want to keep the appearance of carbon fiber. Mistakes with fiberglass tubes can be corrected with sanding and a coat of filler. Mistakes with carbon tubes have to be corrected with sanding and multiple epoxy coats.

Alex

Luke said:

And what sort of results and performance should I expect? It is for a supersonic HPR

Click to expand...

CF layups are generally lighter and stiffer than fiberglass ones, so you should save some weight. However, stiffness isn't a primary issue with tubes, so that probably won't help much.

Performance of what? Lighter is better for maximizing acceleration. A carefully built rocket will generally be under the optimal weight for altitude anyway.

the plan so far tinkers on the line of supersonic, I was hoping that utilising CF for airframe and fins might save enough weight to carry me comfortably over that line.

Performance in terms of stiffness as well. What type of CF should I be looking at using? How many wraps of it will I need to be sturdy for mach 1? etc

Luke said:

the plan so far tinkers on the line of supersonic, I was hoping that utilising CF for airframe and fins might save enough weight to carry me comfortably over that line.

Performance in terms of stiffness as well. What type of CF should I be looking at using? How many wraps of it will I need to be sturdy for mach 1? etc

Click to expand...

I have never seen a project that needs carbon fiber at M1. Generally, fiberglass, blue tube or even paper will hold up just as well as carbon fiber.

To answer your other questions we'll need to know more info about your project. What diameter tubing will you be using? Will you be using a custom NC or one made my a manufacturer?

Alex

Like everyone else has said laying CF is very similar to FG. CF is a little harder to get wrapped tight since it is a little stiffer. When I cut my fabric I attach a 3/4 steel rod with duct tape to the bottom of the fabric. As I roll the fabric on the weight helps to keep the CF laying flat. Once I get to the very end where there is 2-3 inches of CF left to roll on the mandrel I cut the duct tape which removes the weight and lay the final 2-3 inches. To get smooth overlaps at the beginning and end I remove 4-5 strand rows of CF. I do this at the start and also at the finish. I would suggest making a small test tube first as practice. My first layup was not very good and I wasted a yard or so of CF. My second layup was much better based on what I learned from the first attemp. I personally prefer laying up CF the strands do not move around as much as FG.

Aksrockets said:

I have never seen a project that needs carbon fiber at M1. Generally, fiberglass, blue tube or even paper will hold up just as well as carbon fiber.

To answer your other questions we'll need to know more info about your project. What diameter tubing will you be using? Will you be using a custom NC or one made my a manufacturer?

Alex

Click to expand...

Yes I was under the impression that heavy wall phenolic tube would do the job fine, but surely a custom made CF tube is going to be lighter, not to mention cooler looking?! ha.

So the project is a 54mm airframe with 38mm motor, aiming to reach mach 1 and 1 mile altitude. I am planning to use a PML nosecone as I don't have the resources or knowledge to make my own nosecone.

Luke said:

Yes I was under the impression that heavy wall phenolic tube would do the job fine, but surely a custom made CF tube is going to be lighter, not to mention cooler looking?! ha.

So the project is a 54mm airframe with 38mm motor, aiming to reach mach 1 and 1 mile altitude. I am planning to use a PML nosecone as I don't have the resources or knowledge to make my own nosecone.

Click to expand...

I usually recommend 3-4 wraps of 5.7oz 3K carbon for a 54mm carbon fiber airframe. Either a plain weave or a 2x2 twill will work great for your application. Read through my "playing with fire" build for tips on finishing carbon fiber.

Also check out some old Jim Jarvis articles that used to be on Rocketry planet.
https://docs.google.com/file/d/0B-t2Ws3N1UvFY1ZCU1MwdEVaLW8/edit

I'm going to try and write an apogee article soonish that will give very detailed steps on laying up and finishing carbon fiber tubing.

Alex

Aksrockets said:

Also check out some old Jim Jarvis articles that used to be on Rocketry planet.
https://docs.google.com/file/d/0B-t2Ws3N1UvFY1ZCU1MwdEVaLW8/edit


Alex

Click to expand...

Would those be Old Jim's articles or Jim's old articles? Vintage has such a nicer ring to it.

My Vintage articles can be found among the technicalarticles here:

https://www.rocketryfiles.com/

Jim

Jim's guide is fantastic.

When you wrap around the mandrel material do you remove it after CF has cured?

accpool said:

When you wrap around the mandrel material do you remove it after CF has cured?

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Not sure who your question is addressed to, but with the method I use, the mylar wrapped around the mandrel is removed after the tube is pulled off. My experience is that this can be very difficult if the tube is curred too hot, even if the mylar is waxed. I have a sharpened stick that I use to carefully pry the mylar away from the carbon.

Jim

My question was just a general one. I see the pictures all of you post but have not seen the "dis-assembly" part. Thanks for the info.

I'm guessing Jim does it sort of like this.

[video=youtube;ULktB6THEZU]https://www.youtube.com/watch?v=ULktB6THEZU[/video]

Tony

Not very active lately, but there is enough good info here to keep you busy for quite a while.:grin:

https://groups.yahoo.com/neo/groups/CompositeRockets/info

NikeMikey

Thanks guys. I've had a read of Jim's very long tutorial..but it was extremely informative and well worth the time!

Moving forward...

I see Aeropoxy needed oven curing, I don't have facilities to oven cure my parts, is there a work around/alternative epoxy to use?

A curing oven can be nothing fancier than a box made from foam insulation board from a hardware store, with some low temperature heater of some sort stuck in. A low wattage light bult may well do the job. A small oil circulation radiative heater works quite well, though generally for larger boxes.

I've used my car in the summer when conditions are right, as a quick and dirty method.

Gerald

PS - Look up MGS 285/286/287 system. That's what I use. Properties are very good without post cure, better than pretty much anything else that can room temp cure. However it is not a high temp epoxy so I wouldn't be thinking to use it M3+.

Gerald

Luke said:

I see Aeropoxy needed oven curing, I don't have facilities to oven cure my parts, is there a work around/alternative epoxy to use?

Click to expand...

Aeropoxy with 3665 hardener really needs an oven but 3660 does not. It helps, but it's not essential. You'll have to work faster with the 3660 and then it will take longer to cure. But, it can be done.

Jim