Carbon fiber 2 stages rocket build.
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Where did you source the prepreg? I was given a large roll of uni prepreg but the supply is getting low.
I got mine from r-g.de/en/home.html
Not the best, but it should do the job just fine.
While I'm at it, here's the list of prepreg retailers that I found, in Europe.
https://www.r-g.de/en/home.htmlhttps://www.easycomposites.co.ukhttps://www.carbon-vertrieb.comhttps://www.compositeshop.de/xoshop/https://www.castrocompositesshop.com/en/https://shop.swiss-composite.ch
https://www.r-g.de/en/home.htmlhttps://www.easycomposites.co.ukhttps://www.carbon-vertrieb.comhttps://www.compositeshop.de/xoshop/https://www.castrocompositesshop.com/en/https://shop.swiss-composite.ch
stantonjtroy
Well-Known Member
For what it's worth, Fibreglast has 3K Carbon twill, Carbon Uni & 7781 glass in prepreg: https://www.fibreglast.com/category/PrePreg_Fabrics Plus they're room temp shipable/storable.
These guys offer UV curable prepregs: https://www.abc-prepreg.com/page_uv_curable_prepregs#
This vendor has a fairly large offering of carbon prepregs: https://compositeenvisions.com/composite-reinforcement-fabrics/prepreg-reinforcements/ These do need to be cold stored and have a 5 yard minimum purchase. Prices aren't bad though.
Vacuoplex MP Microporous Complex Breather on the left (Peel-ply + micro-porous film + breather all in one), and prepreg on the right.
I'll probably 3d print a proper plunger for it, but this should do the job.
Just for comparison and curiosity, how tacky is your prepreg? Sticky to the touch? Or does it only stick to itself?
Oh, I should have said that this tube is a normal wet layup with 100g/m² UD carbon.
I have yet to test the prepreg. It's a bit tacky and a bit sticky to the touch, but my workshop is relatively cold.
Made another wet layup today. 100g/m² UD carbon, 3" ID but this time with shrink tape.
I also got more pictures of the process!
First hoop layer. It lays down really nicely.
This time around I oriented the support scrim towards me. It makes it much easier to apply pressure without disturbing the fibers too much.
The last layer is one. This picture also shows the main three tools I used during this layup. I only use the brush to first wet the mandrel and to tap down the fibers along the mandrel's axis. The rest is layup using the squeegee then de-aired using the fined roller.
Now time for the fun part: Shrink tape. This is my first time using shrink tape: note the "wrinkles".
And this is where things started getting a bit out of hand. The resin was already past it's "90 min working time", I started heating up the shrink tape (this one only starts to shrink at ~65°C) and the epoxy started flash curing. Oh well, I guess I didn't have to wait 24 hours to demold this one.
Trimmed, raw shrink tape finish.
I'm thinking about making another one, also with shrink tape but without flash curing the resin......
The N5800 ain't a gentle motor so I better make sure everything is up to the task. Better safe than sorry, I only have one chance to get this right. I can't just build two times the same rocket, like multiple universities' teams to increase my chance of success.
Here's how it sound. In the end, I'm slowly working my way towards the unidirectional carbon fiber prepreg.
View attachment 3in_UD_shrinktape_flashed_resin.mp4
Back to the other 65mm ID tube: I made a set of bulkheads and "centering rings". Nothing really special here.
More to come...
I also got more pictures of the process!
First hoop layer. It lays down really nicely.
This time around I oriented the support scrim towards me. It makes it much easier to apply pressure without disturbing the fibers too much.
The last layer is one. This picture also shows the main three tools I used during this layup. I only use the brush to first wet the mandrel and to tap down the fibers along the mandrel's axis. The rest is layup using the squeegee then de-aired using the fined roller.
Now time for the fun part: Shrink tape. This is my first time using shrink tape: note the "wrinkles".
And this is where things started getting a bit out of hand. The resin was already past it's "90 min working time", I started heating up the shrink tape (this one only starts to shrink at ~65°C) and the epoxy started flash curing. Oh well, I guess I didn't have to wait 24 hours to demold this one.
Trimmed, raw shrink tape finish.
I'm thinking about making another one, also with shrink tape but without flash curing the resin......
The N5800 ain't a gentle motor so I better make sure everything is up to the task. Better safe than sorry, I only have one chance to get this right. I can't just build two times the same rocket, like multiple universities' teams to increase my chance of success.
Here's how it sound. In the end, I'm slowly working my way towards the unidirectional carbon fiber prepreg.
View attachment 3in_UD_shrinktape_flashed_resin.mp4
Back to the other 65mm ID tube: I made a set of bulkheads and "centering rings". Nothing really special here.
More to come...
Section view both tubes I made. Yes, I chopped them both.
Tube 1: Made using what I would call the "go-to" method, just peel ply on the outside, no real compression.
Tube 2: The last one I made, with shrink tape. I'm pretty confident that if the resin had a cure properly without flash-curing, most, if not all the void would have been removed.
Maybe a backstory on this project.
It started back in October 2019 with the intention of designing and building a two-stage rocket to reach 164 000 ft. But with many redesigns, the simulated altitude kept getting higher and higher...
Currently, the main goal is to reach + 328 000 ft using commercial motors with modified casing closures: N5800 to M2245, fully subminimum diameter.
This motor combo has long being simulated reaching altitude past the Karman line, but someone had yet to succeed.
Tu Wien space team already made 2 attempts and are planning on a third at BALLS.
Design-wise it's pretty simple, a mix of Bare Necessities and PHX4. It's probably as short as possibly feasible without a similar inter-stage to PHX4.
Anyway, back to making the last three fins.
It's only a matter of time until RGClark finds out about this thread
It started back in October 2019 with the intention of designing and building a two-stage rocket to reach 164 000 ft. But with many redesigns, the simulated altitude kept getting higher and higher...
Currently, the main goal is to reach + 328 000 ft using commercial motors with modified casing closures: N5800 to M2245, fully subminimum diameter.
This motor combo has long being simulated reaching altitude past the Karman line, but someone had yet to succeed.
Tu Wien space team already made 2 attempts and are planning on a third at BALLS.
Design-wise it's pretty simple, a mix of Bare Necessities and PHX4. It's probably as short as possibly feasible without a similar inter-stage to PHX4.
Anyway, back to making the last three fins.
It's only a matter of time until RGClark finds out about this thread
Michael Wilson
Well-Known Member
And remember you’ve been working on this wayyy longer than he’s been messaging people about it. This was your idea, not his. Excited to see this build.
Indeed
I'll probably post an evolution of the design, from October 2019 to today. I find it quite interesting to see the interactive process and the influence of other birds.
Second fin have been cut out, 2 more, then... bevels...
I'll start working with the prepreg next week.
These look great! I’d love to get results like this so I have a bunch of questions for you.
- How did you get them so close to the right size? Did you use a template of some kind? If so, did you adhere it to the plate before cutting it?
- Did you use a carbide-tipped jigsaw blade? If not, what kind of blade did you use?
- Did you cut at full speed?
- Approximately how long did it take you to cut one fin?
- What did you do for dust collection?
- It looks like the outer piles are perpendicular to the root chord of the fin. Is that correct? Why did you choose that orientation?
Thank you, just take as much time as needed, patience is key...
1. Masking tape, a ruler, a square, and a mechanical pencil. Nothing fancy. I prefer using techniques that I'm comfortable with.
2. I used a normal blade for metal. They do the job just fine but don't last long. I used a total of two blades.
I do have two carbide grit blades, but I hate the rough cut they make.
3. y e s
4. Probably 10 minutes per fins (just for rough cutting with the jigsaw), what takes the longest is setting up the straight edge. I cut 1mm to the line, then belt sander, then by hand using a sanding block.
5. Shop vac. And of course, a proper respirator.
6. Because that's the only orientation I could fit the fins on the plate without having to do annoying cuts. At first, I was planning on making my own quasi-isotropic and balanced plates (90/0/+45/-45...): I have all the stuff needed. I ended up going for commercial plates (90/0) as those fins are for the booster (approx Mach 2.3 and KISS)
< aluminum plate I was planning to use to make my own platesI'll definitely be attempting to do my own plates one day, resin infusion, prepreg, or wet layup.
Thanks for answering all my questions! You can learn a lot from watching what other people do but it’s not always clear how—or why—they do it.
Your composite work is next-level! I look forward to seeing what you come up with.
Half of the LE bevel, still need to do the TE and the other fins.
I used the jig shown in post #22 for the rough bevel then finish by hand.
It's not the most efficient process but it gives really good results.
I started working with the prepreg: cutting the individual plies for the fincan tube. It cuts really nicely with a simple cutter blade. The ability to precisely cut it should come in very handy during the tip-to-tip.
All the plies packed and ready for the layup, hopefully, tomorrow.
To be continued...
I'm writing this post while waiting for the next round of prepreg to get to room temp, you'll know why... :
I made a first attempt at making a prepreg tube. And well, not very good.
Problemes:
I'll change a few things: Wrap the shrink tape with a much lower step over + maybe try the "mylar surface release" shown by Watheyak here.
To be continued...
I made a first attempt at making a prepreg tube. And well, not very good.
Problemes:
- Shrink tape step over too high = bad finish + too much resin bleed (I'm aiming for nearly 0 bleeds as the prepreg already has a low resin content)
- ID layer is dry. Possible causes:
- Fiberglass mandrel instead of aluminum (Heat distribution)
- Too much resin bleed
- Maybe, just maybe a "reaction" to the release agent? (extremely, extremely, extremely unlikely)
- And probably other things I'm still unaware of
- Chemlease 2693w is amazing, the tube release without any problem.
- The fiberglass coupler is good to at least 120°C for 2h.
I'll change a few things: Wrap the shrink tape with a much lower step over + maybe try the "mylar surface release" shown by Watheyak here.
To be continued...
I've made a pile of prepreg tubes for this and another hobby. I've got a bunch of really boring stuff to say about the subject. But here are the highlights.
I use .002" mylar to get rid of the tape spirals and keep the resin in place. The prepreg already has the correct amount of resin and if much of it escaped through the tape spirals, that could be the reason for the dry spots.
I also wrap the tape so the next edge is about 3/16" away. Very dense. I also make sure there is consistent tension while I'm wrapping it.
Don't forget release on the mylar!
I use .002" mylar to get rid of the tape spirals and keep the resin in place. The prepreg already has the correct amount of resin and if much of it escaped through the tape spirals, that could be the reason for the dry spots.
I also wrap the tape so the next edge is about 3/16" away. Very dense. I also make sure there is consistent tension while I'm wrapping it.
Don't forget release on the mylar!
Last edited:
Second attempt. Tighter shrink tape wrap.
I added a layer of vac bag film on the outside to prevent the resin from dripping down onto the oven.
Shrink tape finish, I'm ok with it.
But how's the inside diameter finish?
Better than last time. New one on the left
I had much less overall bleeding. Most of the bleeding happens at the edges:
This is where the shrink seems to bridge just enough for the resin to escape the layup. Something like a "tape dam" should fix it.
The tube is 190mm long, 1.7mm thick and, 156g.
I'm going to sand down the outside and coat the inside in a really thin layer of resin just to make it smoother.
It's starting to look like a rocket
I added a layer of vac bag film on the outside to prevent the resin from dripping down onto the oven.
Shrink tape finish, I'm ok with it.
But how's the inside diameter finish?
Better than last time. New one on the left
I had much less overall bleeding. Most of the bleeding happens at the edges:
This is where the shrink seems to bridge just enough for the resin to escape the layup. Something like a "tape dam" should fix it.
The tube is 190mm long, 1.7mm thick and, 156g.
I'm going to sand down the outside and coat the inside in a really thin layer of resin just to make it smoother.
It's starting to look like a rocket
Looks pretty amazing!
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