BryRocket
Well-Known Member
- Joined
- Jun 19, 2017
- Messages
- 516
- Reaction score
- 175
Like most, I have been contemplating a Level 3 build and certification attempt. I had a pretty good idea of what I wanted to do, the techniques I wanted to use and a lot of the supplies already on hand so I reached out to a few local rocketry legends (Stu Barrett and Jim Jarvis) to see if they would mind lending a hand as my TAPs. I won't go into details on what it took to convince them to endure my countless emails and help me with the project but ultimately they agreed! I had planned for this build to take me a very long time but I ended up with about two months of reduced working hours (like most) so I hammered out a bunch of it.
I'll try to keep this thread as concise as possible.
Initial Plan: Roll-wrap 3" carbon fiber tubes and make a minimum diameter rocket that would fly on a CTI 6XL motor (this is where CJ tells ME I'm crazy). I also wanted to use the "zipperless coupler" design, suspending the EBay in the upper airframe. Here is the design:
Lets start with the tubes. I wanted to make 2 tubes, each 44' long and then cut them to size. I will not go much into the tube rolling process as you'd be better suited visiting Jim Jarvis' web tutorial on that HERE for part 1 and HERE for part 2. I used 2x2, 3K twill weave from Composite Envisions. I LOVE this stuff. The weblock makes it so much easier to cut the cloth into accurate patterns. I also used AeroPoxy system 2032 resin with the slower 3665 hardener. For the mandrel, I used 2 36" sections of Public Missiles 3" coupler tubing and then cut one down to make one long tube of 50". I printed out a number of centering rings and a large tube-joining coupler and mated them onto a long 1" piece of conduit to make the mandrel. I also printed out the rest of my mandrel setup. I then applied a high temp wax to the mandrel a few times, wiping it off really good between coats. 0.005" Mylar film was used to wrap the mandrel and was covered on both sides with the same wax. This is where my first problem occurred. Apparently I had some 0.002" mylar laying around and used it. The tube came off beautifully, I was so happy with it but then I couldn't get a motor case to slide in easily. It would actually take a CTI case but wouldn't accept my snap ring cases or the standard fiberglass couplers. I contemplated just committing to the CTI case, sanding down the OD of the coupler, etc but just couldn't stand it so I ended up going back and making two more tubes, but with the correct 0.005" mylar and the ID of those came out perfect. Ultimately I ended up with 3 good tubes, one a slightly too small ID.
The mandrel:
Printed centering rings and long coupler, conduit and PML coupler tubing.
Finished mandrel. The screwdriver just goes into holes that lock the tube into place.
Carbon cut to give me 48" tubes that have 6 wraps.
Ready to roll, albeit with the wrong mylar on the mandrel.
Didn't take photos during the rolling process but I have a time lapse video that isn't all that exciting. Here is the first finished tube. They all ended up looking almost exactly the same. After the carbon was completely rolled I used peelply over the top. For those that have rolled tubes, when you think you're about done as you finish the carbon and start the peel ply, you realize now the fun really starts trying to get it wetted out just right. Ugh.
Here is a tube after another light layer of epoxy has been applied and allowed to cure for a few days prior to sanding.
Now were having some real fun. Sanding down the tubes with 120 grit, then 320 grit, then 400 grit, then 600 grit then finally 2000 grit. I left the fin attachment area alone after the 120 grit.
Here are my tubes after that stage and cut down just a touch.
Next up will be fins.
I'll try to keep this thread as concise as possible.
Initial Plan: Roll-wrap 3" carbon fiber tubes and make a minimum diameter rocket that would fly on a CTI 6XL motor (this is where CJ tells ME I'm crazy). I also wanted to use the "zipperless coupler" design, suspending the EBay in the upper airframe. Here is the design:
Lets start with the tubes. I wanted to make 2 tubes, each 44' long and then cut them to size. I will not go much into the tube rolling process as you'd be better suited visiting Jim Jarvis' web tutorial on that HERE for part 1 and HERE for part 2. I used 2x2, 3K twill weave from Composite Envisions. I LOVE this stuff. The weblock makes it so much easier to cut the cloth into accurate patterns. I also used AeroPoxy system 2032 resin with the slower 3665 hardener. For the mandrel, I used 2 36" sections of Public Missiles 3" coupler tubing and then cut one down to make one long tube of 50". I printed out a number of centering rings and a large tube-joining coupler and mated them onto a long 1" piece of conduit to make the mandrel. I also printed out the rest of my mandrel setup. I then applied a high temp wax to the mandrel a few times, wiping it off really good between coats. 0.005" Mylar film was used to wrap the mandrel and was covered on both sides with the same wax. This is where my first problem occurred. Apparently I had some 0.002" mylar laying around and used it. The tube came off beautifully, I was so happy with it but then I couldn't get a motor case to slide in easily. It would actually take a CTI case but wouldn't accept my snap ring cases or the standard fiberglass couplers. I contemplated just committing to the CTI case, sanding down the OD of the coupler, etc but just couldn't stand it so I ended up going back and making two more tubes, but with the correct 0.005" mylar and the ID of those came out perfect. Ultimately I ended up with 3 good tubes, one a slightly too small ID.
The mandrel:
Printed centering rings and long coupler, conduit and PML coupler tubing.
Finished mandrel. The screwdriver just goes into holes that lock the tube into place.
Carbon cut to give me 48" tubes that have 6 wraps.
Ready to roll, albeit with the wrong mylar on the mandrel.
Didn't take photos during the rolling process but I have a time lapse video that isn't all that exciting. Here is the first finished tube. They all ended up looking almost exactly the same. After the carbon was completely rolled I used peelply over the top. For those that have rolled tubes, when you think you're about done as you finish the carbon and start the peel ply, you realize now the fun really starts trying to get it wetted out just right. Ugh.
Here is a tube after another light layer of epoxy has been applied and allowed to cure for a few days prior to sanding.
Now were having some real fun. Sanding down the tubes with 120 grit, then 320 grit, then 400 grit, then 600 grit then finally 2000 grit. I left the fin attachment area alone after the 120 grit.
Here are my tubes after that stage and cut down just a touch.
Next up will be fins.
Last edited:
