boatgeek
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This rocket was probably the longest-term occupant of my design percolator. It started way back inspired by @jqavins' Office Supply Rocket. Around the time that came out (2019!), my dearly beloved wife noticed that a batch of toilet paper came with really thick core tubes, and she asked if I wanted to save them for a rocketry project. That sat for a while. Then in 2021, I was all ready to start up a build thread about a break apart rocket with offset tubes that would be really, really cool ... when @neil_w started up the Shear Insanity build. Since I didn't want to (a) look like a follower or (b) have to live up to much, much higher build and design standards, I decided to shelve it for a while. A few months ago, I was cleaning up the workbench, noticed the tubes again, and started work.
The original plan was for simple 18mm or D12-24mm sized propulsion. Then I hit on the idea of making it an alphabet rocket. After all, if it's pretty light, it can boost on a lot of different motors. So that meant that I needed passage for long 24mm motors from CTI--at least 3 grain and maybe even 6 grain. Once I started in on that concept, offsetting the tube sections became really difficult. I ended up abandoning that for concentric tubes all the way up. At that point, it became a fairly straightforward break-apart recovery rocket. The nose cone is 3-D printed, as are the rings that join the tube sections. Each one of those has a centering cone with four indexing ridges. They hold together remarkably well but still break apart easily when there's no compression on the stack. Here's a matched pair of rings. The recesses are at the top of each tube section, and the ridges are at the bottom. All 3-D printed parts were designed in Rhino.
The fin can rings have an added twist of having rail guides and centering rings built in. You can just barely see the recesses in the left hand unit--that's the upper one.
The fins are mostly-vanilla papered balsa. The only weirdness is that I papered them with epoxy as an experiment. I'm not sure if I'll repeat that in the future, but it did give a really stiff final product. The tubes tended to delaminate and had really off-square ends, so I cut them square and soaked with with laminating epoxy to firm up the surfaces.
The other really interesting part from a design standpoint is how to hold it together in the air until I'm ready for the pieces to all separate. My plan is to have a small eye screw and nut tied to the middle of the shock cord. That will connect to a magnet at the base of the nose cone. If that all works, it'll be really slick. I'm not sure if it will work yet.
I woudl also appreciate any input from people with experience flying berak-apart rockets to say how much space one needs between the pieces. At the moment, all of the parts are free-floating on the shock cord.
Without further ado, here's a mostly-finished product, both in flight form and broken apart:
Since those pictures were taken, I wrapped the entire brown fin can section in peel and stick holographic vinyl. Since there's no chute and apogee is a couple of thousand feet on maximum motors, I want to be able to see flashes in the air.
Still to be done before maiden flight at Sod Blaster V Labor Day weekend:
Get the magnet retention system working properly (will likely require a couple of holes in the orange section)
Update the sim with final weight and CG
In theory, this has a range of apogee from 2 feet (1/2A-0) to 2,000' plus (F79). We'll see how things pan out in practice.
The original plan was for simple 18mm or D12-24mm sized propulsion. Then I hit on the idea of making it an alphabet rocket. After all, if it's pretty light, it can boost on a lot of different motors. So that meant that I needed passage for long 24mm motors from CTI--at least 3 grain and maybe even 6 grain. Once I started in on that concept, offsetting the tube sections became really difficult. I ended up abandoning that for concentric tubes all the way up. At that point, it became a fairly straightforward break-apart recovery rocket. The nose cone is 3-D printed, as are the rings that join the tube sections. Each one of those has a centering cone with four indexing ridges. They hold together remarkably well but still break apart easily when there's no compression on the stack. Here's a matched pair of rings. The recesses are at the top of each tube section, and the ridges are at the bottom. All 3-D printed parts were designed in Rhino.
The fin can rings have an added twist of having rail guides and centering rings built in. You can just barely see the recesses in the left hand unit--that's the upper one.
The fins are mostly-vanilla papered balsa. The only weirdness is that I papered them with epoxy as an experiment. I'm not sure if I'll repeat that in the future, but it did give a really stiff final product. The tubes tended to delaminate and had really off-square ends, so I cut them square and soaked with with laminating epoxy to firm up the surfaces.
The other really interesting part from a design standpoint is how to hold it together in the air until I'm ready for the pieces to all separate. My plan is to have a small eye screw and nut tied to the middle of the shock cord. That will connect to a magnet at the base of the nose cone. If that all works, it'll be really slick. I'm not sure if it will work yet.
I woudl also appreciate any input from people with experience flying berak-apart rockets to say how much space one needs between the pieces. At the moment, all of the parts are free-floating on the shock cord.Without further ado, here's a mostly-finished product, both in flight form and broken apart:
Since those pictures were taken, I wrapped the entire brown fin can section in peel and stick holographic vinyl. Since there's no chute and apogee is a couple of thousand feet on maximum motors, I want to be able to see flashes in the air.
Still to be done before maiden flight at Sod Blaster V Labor Day weekend:
Get the magnet retention system working properly (will likely require a couple of holes in the orange section)
Update the sim with final weight and CG
In theory, this has a range of apogee from 2 feet (1/2A-0) to 2,000' plus (F79). We'll see how things pan out in practice.
I had to optimize so hard to have a chance of flying it on an A that I compromised away some other stuff. The tube size was definitely a hassle--just a titch bigger would have made a lot of things easier.
