Archive for New Learnings

Never Stop Learning

March launch at Plaster was sunny with some wind. With the fin fixed, Sparkle Motion was ready to fly on a CTI K160. In January the launch lugs and the cracked fin, kept me from flying. I struggled with the launch lugs and it turned out to be an issue with a dirty rail.

https://picasaweb.google.com/g.phresh/PlasterCityMonthlyLaunches#slideshow/5581167681076812546 (photos courtesy of G’s new camera)

The take-off was nice, however the 6 second delay was too short. An early ejection caused a zipper in the cone, also shredded off the tracker transmitter and tore up the parachute. The rocket launched quite well as the parachute acted as a streamer and slowed it down. Luckily clear line of sight of where the rocket landed. To my good fortune, one of the boy scouts found the transmitter. It had been ripped free of the shock cord, which tore the cover off and lost the battery.

Mark C told me that the transmitter manufacturer could repair. I did buy another transmitter for my L3 flight next weekend. Speaking of L3 flights, was happy to watch Mike C’s successful flight on an Extreme Darkstar. He was too funny, later that day he stopped by G & my set-up areas to thank us for making our mistakes and learnings visible as that helped him in his pursuit. So glad someone could benefit from my misadventures. Although I do have to say that I learn the most from correcting my mistakes.

At home I (and Monty) assessed the Sparkle Motion’s damage. Looks like I’ll need to use some fiberglass material and an epoxy concoction to patch.

Lessons learned:

A clean launch rail is key. keep baby wipes and spare igniters on-hand.

Transmitters can be repaired. It is a good practice to tape the battery in place, tape the cover shut, and finally tape securely to shock cord well above parachute.

6 second delay on motor is not long enough.

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Test Flight Documentation

“You can only grow if you’re willing to feel awkward and uncomfortable when you try something new.” – Brian Tracy

This documentation for the level 3 flight feels like the equivalent of a term paper. What  the heck was I thinking. In preparation of the real event, I conducted a test flight using my level 3 rocket with a level 2 motor. The rocket did great both attempts, the human improved after the first.

Pre-Level 3 Documentation

Homework for Level 3

Last launch I was able to get feedback from Kurt and Jack on my rocket construction and electronics design. Fortunately only a few items to be addressed and some recommendations for future designs. Part of good design is to try to anticipate anything that could go wrong.

On the electronics board, is a switch to control the on/off for the ARTS2 altimeter. I had set mine up like a light switch. Click it up to turn on. However there is a lot of force when a rocket launches and there is a chance that the switch could get pushed down. The fix is to rotate the switch 90 degrees so it is horizontal. I could also change it so up is off and down is on.

The second correction needed is to secure the altimeter bay to the payload bay with a screw. Right now that part is held in place with three plastic rivets and I have a safety net of a shock cord tethering the piece to the nose cone. So that way if rivets give way, will not lose those parts.

This week, I will implement those two modifications and get my level 3 flight plan submitted to my advisors. December 11th in Lucerne is the target date for the level 3 flight.

Exactly What I Asked For But Not What I Wanted

Ok so I will own that I am a contradictory and often an inconvenient woman, however that has nothing to do with this post. This weekend was Plaster Blaster 9, and originally I wanted to go for my level 3 certification during this event. Plans changed and instead this would be the opportunity to fly the unnamed Xtreme Darkstar to demonstrate 1) solid basic construction, 2) use of electronics to control deployment, and 3) rigorously test G’s desire to be a  mentor.

This is a beauty shot of the setup. What is does not convey is the hours of launch preparation.

Get ready, it’s pressuring up. This is a gorgeous motor, CTI L820 Skidmark.

Thanks to pilot Harald Berge, for his well-timed photos of the launch. So nice to have someone else take photos, so I can stand back and just enjoy watching the flight.

Apparently these are mach diamonds. New learning for me.

Just a lovely take-off. Everything looked great until apogee. This is where my altimeter interpretation blunder comes into play. I instructed both altimeters to deploy the parachute at ‘Main’ which is low altitude instead of “Apogee’.

View of Ozark ARTS2 altimeter above

View of the Featherweight Parrotv2 altimeter above.

The rocket started to free fall, which is never a good thing. Luckily the rocket design saved itself by shifting horizontally and slowly spinning. Kinda like a helicopter blade, and then the parachute ejected. Recovery of the rocket was straight-forward, no damage. I was upset with myself, not the rocket, as it did exactly what I told it to do, but not what I wanted!

My fellow rockteers told be that I was the luckiest rocketeer that despite my mistake it turned out okay. The rocket launched unnamed, and after that fateful flight had named itself Serendipity.

Where Is My Mind

Good thing I had some extra time to work on the rocket, as I was deluded that I was almost done. As I was writing up my pre-flight prep list and discovered some d’uh items. Better to find them now then on launch morning.

I had waited to epoxy some of the last pieces…..and much to my frustration this is when I caused my own problems.

Was thinking that it was smart to include the bar on the u-bolt for reinforcement, however what I did not think through was that it would alter how these top and bottom pieces would fit on the avionics bay.

The electronics sled fit flat and snug inside the tube and against the lids, however with the u-bolt bar I had to file out space for this to fit in. Not a big deal, but it annoyed me.

When creating the electronics bay, G recommended that I make the mark the top and bottom accordingly. Well I did all that, yet did not notice the rivet holes that secure the electronics portion to the upper airframe. So I marked everything upside down.

Again not a huge deal, just made me wonder (cue The Pixies Where is My Mind?).

Argh drill the rail button screw holes too big. Yes the screw is 1/4″ and no you do not use that same size drill bit. Seems obvious now.

When the bulkhead ring was epoxied into the nose cone shoulder, it changed the shape a bit. So it was now a tight fit into the upper airframe piece. It took must sanding to correct this, and needs a bit more before Saturday.

By far, the most frustrating of all the bozo manuevers was the retainer ring. I decided to install it post build, however I made two mistakes that came back to bite me (and G) in the ass later. 1) The rear centering ring should be flush with the end of the motor tube, I managed to get mine a bit recessed and 2) when marketing and drilling the holes these were slightly turned inward (due to problem #1). I desperately needed G’s help to correct my mess on this.

Black Powder Experiment

This work for L3 project is really stretching my skillz. Since I am using electronics to control deployment of the parachute, I get to experiment with black powder, that’s gun powder people. Makes me feel like a mad scientist. With this rocket kit, it uses nylon screws to keep the nose cone in place.

As part of my design, I have to determine how much black powder is needed to properly deploy the recovery system. So I need enuff umph to break the shear pins, blast off the nose cone, and eject the parachute. I calculated some rough estimates based on the rocket diameter and tube length, however I did not know how to take into account the shear pins. G recommended a ground test.

Here’s the set-up. The rocket rests on wooden holden with lots of blankets to cushion any parts and protect G’s house from destruction. There are wires leading from the charge in the rocket, hooked up to a battery, with a continuity key/launch button. G’s done this before so has the process down, and all the right equipment to make it easy.

Here’s a video of the ground test http://www.youtube.com/watch?v=pYIZfPW9pY8

Be warned this is my first video, so excuse my lameness. The 2g of black powder was clearly not enuff. I will re-test at Plaster site with 3g.

Fun with Foam

Poor Cheshire has not had a successful flight yet. Last attempt the nose cone weight did not stay in place. So plan B involved foaming it in place.

All the tools needed to accomplish the task. I also bought an apron that I wear for messy rocketry processes.

The directions were very precise for amount, mixing, and drop(s) of water for proper expansion. First batch went amazenly smooth. The second I added 2 drops of water and did not get to the pouring right away. It took on a life on its own, expanding quickly. It was like an amoeba and started engulf objects. Could be the makings of a bad horror movie.

I made the mistake of grabbing for it and then my glove was stuck. It was comical. After I finished laughing and cleaned up the mess, I completed adding a second batch into the rocket. Let it stand over night and righted the nose cone. Woo hoo it stayed in place. Am thinking August 14th I may head out to Lucerne to fly Cheshire and try out some electronics in preparation for level 3.

Cheshire Takes to the Skies

After a disappointing non-flight at LDRS, it was time to correct the stability issue with Cheshire. With the motor loaded, the rocket was heavy. A fat bottomed rocket, which it meant that it need some nose cone weight to balance. I am now the proud owner of RockSim software. So I dove in and thrashed around the program trying to come up with the correct amount of weight needed to add to the nose cone. First attempt 4 lbs, second 4oz. Looks like I have a lot to learn about using RockSim.

G and I used some special plastic epoxy and buckshot to pour into the nose cone. Well pour is not quite the right description. Imagine a hole with less than 1/2″ diameter and trying to encourage a mixture of 8oz buckshot and 1oz epoxy through this. Once in place we waited for the epoxy to do its thing. It got pretty hot, so a nice cup of water to cool helped out.

It had to stay upright overnight to properly set. The concoction was quite stinky and still is. To do list for any future weight adjustments projects: locate my local gun store. All seemed well with the weight addition, so decided to drag race with G at Lucerne on Sat 07/10.

I finally arrived in the desert after several hours of construction traffic and needed to just calm the down the road rage vibe. Can tell that I am getting better skillz as the prep time to pack recovery system and load the motor was fairly quick. Mainly due to the lack of epoxy mess preventing the motor casing from smooth insertion. Before I always had to spend time sanding away any blockage.

(Shot of the buckshot dropped down into the shoulder)

As we made out way for launch pad assignments, the weight fell from G’s nose cone. This meant that mine was subject to the same failure. I reasoned that perhaps his rocket sitting in the heat sped up the issue. Okay I just wanted to fly my rocket, so I decided to just go for it.

All started out well and Cheshire was flying straight. We could see the point at which the weight fell in the nose cone as the rocket started to cart-wheel. Poor Cheshire slammed down hard on the ground and then the parachute ejected. Post mort revealed that the rocket was well-built and did not sustain physical damage. However the paint job did take a beating. The blow seemed to shake the paint off the nose cone in chunks. G also blogged about this excursion as well. Thanks G for the amazing photos.

(Monty assessing Cheshire’s damage. Looks like repainting of the nose cone is in order.)

Just a note on the motor, a Cessaroni I140 Skidmark. I just love the sparkly tail. My first one, and am a fan now.

Next up: Round 2 of weight modification will include foam to secure the epoxied buckshot in place.

New finishing techniques

Sparkle Motion was assembled and technically ready for paint but I was feeling a bit uneasy. Had lunch with G (my rocket therapist) to have him look it over. This was the my first rocket with four fins. I fould that to be tough. The first pair were perfectly straight, the instructions advise the builder to install the fins in pairs so check the 180 degree angle. Tape, tape and more tape helped me get the first pair just right. I let that set overnight, and started the second pair the next morning. Something must have gone wonky with my taping because the second pair of fins were *not* straight. I was worried that it would adversely affect the flight with unintended spin. Of course I did such a stellar job with the epoxy that I could not remove them. LOL! Apparently a bit of curve is okay, however he thought that in the future I should attach one fin at a time. Duly noted.

The Nike Smoke design also merges the nose cone and payload section into one piece. This was new to me, so installing the bulk head ring felt off. G suggested I use some fiberglass cloth to reinforce around the ring and up the inside of cone. The comical thing about trying to mount the bulk head ring and later the cloth is that it is a long part and my arms are not. I was up to my shoulder in rocket part and ended up with epoxy all over my arm. We later laughed that the rocket kit should come with those shoulder length latex gloves used on a cow dairy.

Okay so back to the finishing techniques. The rocket has a cloth wrap over the cardboard body tube for reinforcement. I did not like the texture of the cloth. I have found that every imperfection on the rocket surface looks worse with paint. G skooled me about using a SuperFil to even out the lumps and bumps, and then a UV Smooth Prime for finish. Of course this stuff is not sold in regular stores, and needs to be ordered from some aircraft place Aircraft Spruce  in Corona CA. Keep in mind that this launch is taking place on a Thursday, and I am targeting to fly that Saturday.

This obviously would not come together in time to have a pretty rocket to fly. It would have to fly naked, and get dressed up later.

Skillz improvement

Since both rocket builds were such challenges for me, I decided that I need to build another one before moving onto Level 2.

A LOC/Precision Hi-Tech H45 was selected for the skillz building exercise. This one I named Bliss and an orange theme seemed appropriate.

Construction went more smoothly than anticipated. Was glad to see that I was getting the techniques down, and progress was a bit faster. I did wise up about what items I can batch together to speed up my total build time.

So Bliss is built and partially painted. I ran out of the Racing Orange paint and the hobby store is quite slow on ordering new inventory. Instead of the clothesline hang system to paint, this time I use a dowel with a clamp for the rocket to set on. That worked much better with more uniform coverage.

One for the what I learned: I had been having problems with getting epoxy on the shock cord. Came across this tip on a rocket blog. It recommended to thread the cord back through the motor tube when epoxying the front centering ring. Experienced rocket builders may be saying well duh, however it was a revelation for me.