By tooxmaster

Parachute for Guardian 54

I calculated the decent weight of my 54mm Minimum Diameter project, Guardian, to be about 4 pounds. I need to be able to fit a reasonably sized parachute inside the nose cone of the rocket, while still having a decently slow decent rate. I decided to make my own 24″ Hemispherical 8 gore parachute.

I started with 0.001″ Ripstop Nylon, cutting it to the template produced by SpaceCAD.

IMG_0552Here you can see six of the eight gores and the shroud line material.

I sewed the gores together on the sewing machine. It was a challenge to learn how to sew again, but I did okay. My dad helped with the first few hems but I did the rest of them after I felt comfortable.

IMG_0560My dad sewing two gores together.

After all the gores were hemmed together, the shroud lines were attached.

Here is the finished product: IMG_0626


All in all, the parachute took about 4 hours to complete. Pretty good for a strong, light, and small volume parachute.

The packing volume turned out to be 4.25″ by 1.5″-D. This fits perfectly in my design.

Cropped 17.2.2014.16.6.24



Accidentally gone full Curt Von Delius – Introduction to my 54mm Min Dia, Guardian

Ridiculousness of minimum diameter rockets can of course be measured in units of Curt Von Delius. For example, fins on a minimum diameter rocket that have a span 1.5 calibers are about 45% kurt von delius. Scratchbuilding ups the CVD coefficient, giving you about 75% Curt Von Delius for the aforementioned scenario.

In my case, I accidentally went full CVD. (Well, almost. I have an airframe. That gives me about 95% CVD).



100% Scratchbuilt carbon fiber MD with the motor case acting as the coupler. The fins are 9 layers quasi-isotropic 5.7oz plain weave carbon, at about 0.085″ thickness.The airframe is 4 wraps of 5.7oz plain weave carbon, about 0.045″ thickness.

The motor is a Loki Research 54/2800 case, with either Soylent Green or my new ‘Supernova’ propellant. Expecting Mach ~2.5-3.1

38mm 6GXL Soylent Green


An extremely long case with an cool result! Burnsim classifies this as a 68% J-560

Pc_max is 820Psi, and Kn is 299-414. Peak mass flux is 1.8 with the stepped core configuration shown in the picture above, but with straight cores it peaks at 2.2! Another reason to step cores on long motors is to reduce erosive burning. Erosive burning is when  the core of the propellant grains gets eroded by the oncoming mass flux of the motor, exposing more surface area and skyrocketing the Kn and Pc. This motor uses a 28/64″ throat expanding to 0.73″.

There are 6 Grains, each 3.4″ long. The bottom two grains are stepped to 9/16 core, while the top four have a 1/2″ core.

The case is 23.25″ long, with 20.6″ total propellant length.

The propellant is “Soylent Green”, a moderate metals, 76% solids propellant. The propellant burns with a beautiful yellow-white flame. The green color comes from Chromium Oxide, a burn rate catalyst.


UPDATE: This motor was static tested successfully on the 19th of April, 2014.

“Color The Sky” – Fins (Part I)

Every rocket needs fins!

I designed the fins in Rocksim to be angular and mean looking. They go well with the stark nature of the crayon nose.

The fins for Color The Sky are made from 1/4″ Baltic Birch Aircraft Plywood purchased from Aircraft Spruce. It has 12 plies. This stuff is insanely tough and very smooth.


We started with the template and printed it out.  I traced the rough outline onto the plywood and marked where we would need to cut.




After cutting the fins on the tablesaw, we taped lined them up on the root edge and taped them together.


A pass on the belt sander cleans up the edges and makes them all the same.



Next step: beveling the fins.

“Color The Sky” – 75mm M Powered Crayon Bank

Recently I got this crazy dream in my head. HOW COOL would it be to stuff the biggest motor possible in a Crayon?! The crayon banks are just a little too small to fit a 98mm motor case sadly. We’ll have to settle for 75mm. (or maybe a custom size EX motor? hmm…)

First off – the plan:

Capture3″ Blue tube runs throughout the entire rocket. It’s essentially a 3″ MD rocket with a crayon bolted to the outside. There are wooden runners bonded to the blue tube that add strength and serve as “centering” strakes. They will be sanded to the shape of the ID of the crayon.


The fincan is reinforced as if the rocket is minimum diameter. this includes large fillets and tip-to-tip. The bottom crayon is then slid over the tube from the front.


Aesthetics: You can make this crayon any colour you like. The first rendition will be pink because real men fly pink rockets! I will be doing 1 or 2 layers of 5.7oz 2/2 till CF over the fins for strength, and aesthetics. Carbon just looks really cool juxtapositioned with the cardboard crayon bank.



That’s all for now. Stay tuned!

CCR75 – Tip to Tip reinforcement

The next and most difficult step is the tip-to-tip reinforcement. I’m using Aeropoxy PR2032/PH3660  with 2 layers of 5.7oz Bidirectional plain weave Carbon Fiber purchased from Aircraft Spruce.

I created a paper pattern using a printout of the fin and a lot of math. I made 3 copies of each pattern, and taped them to the cloth.



The first layer is half the size of the second layer, which creates a flutter resistant reinforcement.

All 6 pieces were then cut out of the cloth.


We encountered some problems here, since the original idea was to cut around the cloth and leave a bit of tape to prevent fraying. However, we soon discovered that trying to take the tape off resulted in more fraying than would have happened if we had just cut on the inside of the line. The next 5 pieces were carefully cut about 1/32″ inside the paper pattern.


Here’s what the top pattern looks like when all is said and done.



The first step was to clean the airframe and fin surfaces with IPA. After this point, the airframe was not touched with bare hands until the process was complete.



The next step was to mix up some Aeropoxy ES6209 for fillets. I made a 1 and a half gram batch, which ended up being almost perfect for what I needed.


After waiting about 2 hours for the Aeropoxy to start to cure, or “go green”, we started the layup.

I painted some PR2032/PH3660 on the surface and then laid the cloth.



I then painted enough epoxy to wet out the first layer, and then laid the second layer.


After the entire 12.7 gram batch had been used up, I laid some 0.0005″ mylar over the surface. Mylar is a great peel-ply material because it doesn’t stick to epoxy when the epoxy is cured, but it sticks down when the epoxy is wet. It also leaves an incredible shiny surface which looks great and requires minimal finishing.

We put about 33lbs of lead weights onto the mylar to compress the layup. This technique is essentially the best way to do a layup without having to use a vacuum bag.



After waiting the ~6 hour cure time, I peeled back the mylar.

The resulting finish is pretty good. It’s certainly not the best I’ve ever seen, but it’s extremely strong and that’s what’s important for this project.



Now, repeat all of that twice more, and the most tedious step can begin – SANDING!

CCR75 – Fin Bonding

The first step in bonding the fins is to sand off the gloss coat of epoxy on the carbon tube, to expose the cloth. I first cleaned the section of tube that was to be bonded with Isopropyl alcohol, and then sanded the tube with 150grit sandpaper until the shine was gone. I then cleaned the surface again with IPA.

You can see a few scratches here, you want it to be about like this; not too much more. It’s important to remember when bonding composites that you want chemical bonds, and not mechanical bonds. Thus, if you rough up the tube too much, you end up breaking the fibers instead of preparing the surface for bonding. 120grit is the absolute maximum that you should use for composite bonding.



I then mixed up a batch of Aeropoxy ES6209. Apply some to the root of the fin, and fit the fin into the alignment jig.



The entire surface is sanded here because i’ll be doing tip-to-tip carbon fiber reinforcement.

Here’s an overview of the alignment jig:



The tube is clamped in the Workmate table, with the jig resting on top. The jig has adjustable spacing between the two blocks to allow for different tube diameters.

The fin is clamped to the side of the jig as shown, and this allows for the fin to be perfectly straight in all vectors.


ES6209 takes about 5 hours to cure with this setup. The other two fins are repeated as shown.

CCR 75

I have on order an all-carbon-fiber CCR 75 from Carolina Composite Rocketry. It has been modified to fit my 75/7680 case, to fly on an Aerotech M685W. RASAero simulations put it at just over 40,000′ from Black Rock. Hopefully it’ll be ready for XPRS 2013.

I’ll be doing an experiment to see if a tailcone will help the drag coefficient. Using the Rouse-tech aft tail cone closure on one flight, and a normal aft closure on another flight.

These tests will probably happen after the maiden voyage at XPRS.