Carbon fiber 2 stages rocket build.

[Zertyme]

I'm back with another build!

This time with 2 stages. I got the idea of making one after I saw a beautiful two stages launch at the 2019 ALRS, in Switzerland.

My plane is to build a versatile and high-performance sustainer. I will go for a 29mm airframe with a 24mm motor mount to keep the altitude "low". Here in Europe, most of the launch site is limited to 2km waivers, sometimes 3km. I will definitely fly the sustained alone on an F240.

For the booster, I want to keep it simple as this is going to be my first two stages. I still need to figure out the electronics for the sustainer ignition.
I will make a Delrin transition then epoxy a carbon coupler tube for the connection.

Don't mind the " separation shear pin"





The booster will have a 38mm MMT while being 54mm in diameter.

I'm also going to roll all my tubes bit, not the carbon fiber coupler that I will use as mandrels. I will not go in deep on the subject as there's already a lot of threads about this.





I already made the 24mm MMT. It's 16cm long for 11.1g and only around 0.6mm thick.

Fins will be 2mm thick carbon similar to my other rocket:





The nosecone will be the trickiest part to do. I'm going for a 7:1 VK profile.
Has anyone already 3d printed a mold?
I have access to a 3d too so that might be a solution.

What do you think? Do you have any recommendation on flight computer with OVSI?
I'm going to post a screen capture of the .ork file as soon as possible.

 

[Nytrunner]

Nice project!

May get more relevant responses over in the Staging/air start advanced section

 

[tim cubbedge]

Thread moved to staging/airstarts.

 

[BDB]

This looks great!

 

[RalfB]

Hello, for my projects I have printed the last three nosecone. That works great.
Here is a link: https://www.thingiverse.com/thing:3383641
In the meantime, I glue together the multipart forms. since I print this in ABS that is great.

 

[Zertyme]

Sorry, I forget there was a staging section on the forum...
Anyways here are the screenshots of the .ork file. It's only temporary for the moment.



and here is the closeup of the sustainer

Hello, for my projects I have printed the last three nosecone. That works great.
Here is a link: https://www.thingiverse.com/thing:3383641
In the meantime, I glue together the multipart forms. since I print this in ABS that is great.

My idea was to make only the male mold and then use a fiberglass or carbon sock. I would then make the tip in aluminum or brass. I would also turn the mold out of foam on the lathe but I will get a more precise form on the 3d printer.

 

[Bat-mite]

Very cool. Will be watching.

 

[mikec]

I will make a Delrin transition then epoxy a carbon coupler tube for the connection.

I had a similar piece of Delrin with more meat in it than that break during an M-to-L two-stage flight. My strong recommendation is to not use Delrin for an interstage, use centering rings inside a fiberglass coupler. Or an aluminum transition might work.

Your rocket might be low enough power for the Delrin to work, but beware of scaling.

 

[Zertyme]

I had a similar piece of Delrin with more meat in it than that break during an M-to-L two-stage flight. My strong recommendation is to not use Delrin for an interstage, use centering rings inside a fiberglass coupler. Or an aluminum transition might work.

Your rocket might be low enough power for the Delrin to work, but beware of scaling.

Aluminum will be my last resort if I can't find anything else. I could also make the transition out of foam then give it a layer of fiberglass or two.

 

[Zertyme]

Finally had time to start this project. I'll be going slowly but surely.

First of all, the sustained body tube. I used a 28mm carbon tube then wrapped it in kraft paper to build up to 29mm.
I'm not going through all the processes as it is pretty well documented ok the forum.




After removing the peel ply, I added a thin layer of epoxy. I then sand down only the top section of the airframe, leaving the fins section with the peel ply finish.


To give it the nice wet look, I wiped thin layers of epoxy using a lint-free cloth. After around 4 coats I was satisfied with the result.


View attachment 395514

I will then polish the entire airframe when the fins will be attached.

 

[Zertyme]

One fin is finally done!
They are made out of a 1.5mm thick r&g carbon fiber plate.
To bevel them I used my belt sander.



I then proceeded to give it a bit more airfoil using a popsicle stick wrapped in sandpaper. It flex just enough to round up the flat part.



And here is the airframe with the fin next to it. The airframe was also given its last coat of epoxy.

 

[Zertyme]

All the fins a now epoxied on. I used Jbweld for both the fillets and tacking.



I decided to go with a tip to tip just for training. I know that it is not very useful in such a small rocket.



Turned out quite well...
I still need to figure out where to pass the cables for the sustainer igniter.

 

[Nytrunner]

Either flat wire down the side of the motor case, or a small brass tube or brake line (flattened) between airframe and mount tube. Both of those are options I've seen from.experienced stagers

 

[Zertyme]

I got a lot of things done in the last weeks. First of all, I finish off the tip to tip section.



I also started working on the nosecone. I decided to go for a conical as it would be easier to make a mold for it on my lathe.

I also machined the nosecone tip out of 6061. It's only around 10g.



I used fiberglass and black dyed epoxy for the nosecone. I'm still working on the finish. It's made out of 3 layers of fiberglass braided sleeve, 1mm thick.

I also made a cable cutter out of the same round stock as the nosecone tip.

Works like a charm for zip ties.
The sustainer alone will accelerate at more than 100G to 1200m on a F240.

 

[Zertyme]

Pretty satisfied with the final nosecone: it weighs 30g with the aluminum tip. (The body tube and the fins weights 55g)



I still have to work on the coupler but also on the Av bay. I'm hesitating whether or not I should install the 24mm motor mount.

 

[mbeels]

That's beautiful, looking really good! What about just using an adapter to reduce down to 24mm, then you still have the possibility of flying a 29mm motor.

 

[Zertyme]

That's beautiful, looking really good! What about just using an adapter to reduce down to 24mm, then you still have the possibility of flying a 29mm motor.

Thanks!
Yes, that could work. But I need to find a way to hold the adapter in place: I don't have any retainer because I was planning on using a friction fit. So I think I'll need to modify the already build 24mm motor mount.

I'm already planning on a V2 for Mach 2 to nearly Mach 3 flight (with the booster)

 

[Andrew_ASC]

Make sure your interstage design has zero wobble with slight side load shoving on rocket on ground. I’ve used aluminum motor casings overhang in the past to accomplish that. Anywhere from 2-3” overhang for L1 rockets seemed successful. Borrowed technique from Adrian Adamson. Specific length didn’t really compute. Just lay airframe on ground and extend sustainer motor casing outward until both stages are solid without wobble.

For staging electronics I recommend Featherweight Raven Altimeter. Easy to program and sim on ground using open rocket output .csv data. Offers user programmable velocity or altitude versus time check for tilt protection. Also Mach immune.

Other than that... Nice thread nice build and have a good flight.

 

[Andrew_ASC]

That's beautiful, looking really good! What about just using an adapter to reduce down to 24mm, then you still have the possibility of flying a 29mm motor.

When you use a 29mm CTI casing there is a flush tail cone that is OEM part so no motor modification. It will allow offset casing rearward into interstage airframe tubing easily for solid interstage joint with minimum wobble. My experience...

 

[Andrew_ASC]

Not trying to thread jack. Here was motor overhang example from previous project of mine. This was 29mm MD.

 

[Zertyme]

Make sure your interstage design has zero wobble with slight side load shoving on rocket on ground. I’ve used aluminum motor casings overhang in the past to accomplish that. Anywhere from 2-3” overhang for L1 rockets seemed successful. Borrowed technique from Adrian Adamson. Specific length didn’t really compute. Just lay airframe on ground and extend sustainer motor casing outward until both stages are solid without wobble.

For staging electronics I recommend Featherweight Raven Altimeter. Easy to program and sim on ground using open rocket output .csv data. Offers user programmable velocity or altitude versus time check for tilt protection. Also Mach immune.

Other than that... Nice thread nice build and have a good flight.

Thank you for your feedback.

I was planning on getting a Raven and a
Featherweight Gps

The body tube came out a tad bit too short for 6Gxl motors (not enough place for recovery and nose cone shoulder) so I might reroll a longer airframe or make a 38mm upscale. There is less space than I expected in the nose cone for the electronics or the recovery.

But to my knowledge, there is no flush 38mm closure.

 

[Zertyme]

View attachment 402004
Not trying to thread jack. Here was motor overhang example from previous project of mine. This was 29mm MD.

Is the blue "warps" where you have your electronics? Still hesitating on whether I should go for HEI or flat copper cable running down the motor.

Here is the possible 38mm to 54mm upscale.



I have also been working on this beveling jig for the booster and other projects.

 

[Andrew_ASC]

Yeah blue thing was an Av Bay for Raven and a APRA comp altimeter. I also made custom nose hold tracker electronics. Was my competition design for university in 2017, it won nationals. Lol. I was addicted to HPR after that...

Teams have since tweaked initial design and pushed 18,700 ft in L1 category specific impulse motors. Fun stuff...

 

[rfjustin]

Beautiful work OP, keep it up.

 

[Zertyme]

Made a 38mm carbon fiber tube. Came out at 125g, 61cm long and 1mm thick.


I still need to work on the finish.

I'll be doing to fin out of a 2mm thick G10 covered in 2 layers of carbon on each side for a total thickness of 3mm
Then I'll reinforce the fillets with 100g/m2 UD carbon.

I want the booster to be able to fly as a high-performance 38mm, from G to J class motor.

The coupler is from a proline nose cone.


I'll be posting a screenshot of the work as soon as I can.

 

[Speaknoevil]

Fabulous project!

 

[Zertyme]

More update!

I cut the fins core on my CNC router.



Really not that bad for a 200 dollars router (model 3018).

Here are the OpenRocket screen captures.
This is the booster alone.


And here is the booster with a sustainer.

View attachment 407146

The next step is laminating the carbon fiber on the fiberglass core.

 

[Nytrunner]

Those motors are a lot bigger than your first sims

 

[Zertyme]

Those motors are a lot bigger than your first sims

Yes, I've changed the design multiple times. Those shown in the latest sim are the largest motor I could use (J510 to I243).

The booster alone will fly on a G67 then on an H669 in march. I'm in Europe and we only have 2km waivers.
For the moment I'm planning on launching the J510 to I243 in July at Aeronaut along with another 2 stages.

 

[Zertyme]

Booster nosecone mold is done!
I recently got a 3D printer (Anet A8 Plus) and this is my first print. It's a 7.5:1 Vk nosecone.

After sanding and filling:


It's finally starting to look like a rocket...