Build Thread: 38mm Min Diameter Fiberglass Estes Vapor, "City Pop"

[emmah]

Back Story: Aesthetic Rockets and Drag Separations




I've been enamored with Estes' Vapor rocket since I first saw it mentioned. It's over a meter tall, slender, and has those photogenic, long, triangular fins. The problem, for a long while, was that it was a Hobby Lobby exclusive, and there's no Hobby Lobby near me.

So I built my own, looking for RockSim and Open Rocket files so I could get the fin dimensions. I upgraded it to through the wall fins which Jim from Bad Boy Rocketry cut and a 29mm motor mount.



The result was Saint Pepsi.



Another digression: I name my rockets for songs, albums, and artists/bands. There's a revisionist/nostalgic genre of synthpop known as vaporwave, which is influenced by everything from Japanese City Pop, video game soundtracks, and the soundtrack to Miami Vice. There's a vaporwave artist who releases albums under many names, including Saint Pepsi, and the name appealed to my sense of humor.



The vaporwave esthetic, design-wise, is full of rich pastels and neon colors (think Miami Vice, Atari's Tempest video game, Sonny, and Crockett) which I followed when finishing the rocket.

When I flew it at TCC's (Tripoli Central California) Dairy Aire launch this spring on a Cesaroni G106, it drag separated and shredded the body tube since I had put in a Kevlar shock cord.



Around the same time, Adam K from Hot Nozzle Society had taken a stock Vapor, covered it in carbon fiber, and flew it as a 38mm minimum diameter. It too lost its nose cone due to drag separation but the carbon fiber prevented a shred.

And Estes made the Vapor available through mail order (selling through two runs of them almost instantly.) So I ordered one and did a quick weekend build. Iceblink Luck is not a vaporwave song, but it is by the Scottish synth/fairygoth/proto-shoegaze band The Cocteau Twins.



I've rebuilt Saint Pepsi, but Adam's 38mm minimum diameter build had me wanting to try it myself.

So I started a design.

 

[David_Stack]

Inquiring minds want to know... how big a 38mm 'powerplant' do you intend to launch this on, and what does it sim to?

And OBTW... LOVE the Cocteau Twins reference, "Heaven or Las Vegas" almost never leaves the CD changer in my car

 

[emmah]

Specifying the Problem

What are the goals for this build?

• High performance sport flyer for I and J motors
• Preserve dimensions of an Estes _Vapor_ as much as possible
• Electronic deployment in a constrained space
• Fly with Featherweight Tracker
• Bonus: Fly on a Loki 38mm K motor

A sport flyer should be built solid. So I'm going with fiberglass nose, air frame, and fins.

The Vapor's airframe is 36", and I have fiberglass from Wildman in the same length.

The J and K motors I'm considering for this build won't leave much space for dual deployment and a tracker in a 36" air frame. Using Eggtimer's Apogee and a chute release with a head end deploy would be a way around this.

Here's a preliminary design in Open Rocket.

I'm deciding if I want head end deploy or mount the Apogee in a connector and pop the nose or the whole forward section.



To answer @David_Stack's question: on a Loki K1127, apogee is just over 6 kilometers! With a Cesaroni J600, 5 kilometers. An I204 is a more sedate 3 kilometers. Definitely a rocket for people who love FAA waivers.

The fins, after some discussion on the HNS Discord, are 1/8" g10.

That gives them some thickness for gripping the tube since I won't have internal fillets. I'll have to think about using Kevlar fibers or doing tip to tip on the fin can.

The fins are done. @Wingarcher cut them, and Mike at MAC Performance Rocketry finished them.



These look great.

 

[David_Stack]

Curious, how much did the c/g location 'shift' as a result of the different material densities/weights (cardboard, plywood, and plastic versus fiberglass airframe) between Saint Pepsi and City Pop? You showed screenshots of the two Open Rocket files, but City Pop includes all the avionics that are not part of the file for Saint Pepsi...

The c/g for City Pop is further forward (likely a good thing given that you are exceeding Mach), but how much of that move is the result of the avionics, and how much is simply due to the heavier airframe materials?

Tapped forward closure and an internal bulkhead for motor retention, or friction fit?

 

[QFactor]

Considering the story behind this build, shouldn't the rocket be named "Fatal Attraction" ?

 

[emmah]

The c/g for City Pop is further forward (likely a good thing given that you are exceeding Mach), but how much of that move is the result of the avionics, and how much is simply due to the heavier airframe materials?

The Wildman nose cone is 125 grams vs 25g for the stock nose cone. Without doing a component analysis I'm thinking it's the biggest contributor.

Friction fit will probably work fine for this, but I put in a forward retainer modeled after the Aerotech in the .ork file.

Aside, I think it's great that Open Rocket files are orks .

 

[jqavins]

Any progress?

 

[emmah]

Any progress?

I'm getting caught up after a three week break from work and finishing two other rocket projects.

I have the parts, and need to figure out if I'm doing head-end deploy or popping it apart ahead of the motor mount bulkhead.

 

[QFactor]

I'm getting caught up after a three week break from work and finishing two other rocket projects.

I have the parts, and need to figure out if I'm doing head-end deploy or popping it apart ahead of the motor mount bulkhead.

I don't envy you on that deployment decision with those itty bitty rockets.

Break out the ruler, the pencil and the paper. Sketch it up. Paper's cheaper than a building mistake.

 

[jqavins]

In post three, you've set it up for head end, and that looks like a good fit. There's room below the break for dog barf or a wad of Nomex or a piston or whatever. And room inside the nose cone for a tiny altimeter. That all looks like it should work fine.

For "regular" deployment you'd have to move the break up, or even eliminate it. Then there's room above the laundry for an altimeter, and it seems like that would work fine.

From here, i.e. not in your shoes, it looks like six of one and a half a dozen of the other. So if you're equally comfortable with both options, the best advice is don't overthink it; pick one, or you risk the dreaded analysis paralysis.

Caveat: the one thing I'd do before choosing is take the actual parachute, fold it up in flight configuration, and put it in a tube. See how much length it actually takes up. Sketch it both ways (as QFactor says) if you see the need (a mental sketch might suffice) then just pick one.

 

[emmah]

Thanks, @jqavins and @QFactor, I have the chute, the jolly logic, the featherweight, and the eggtimer apogee and I'm going to do some dry fits of all them. I'm willing to give up on flying with a Loki K to fit all the laundry and hardware in.

 

[QFactor]

Thanks, @jqavins and @QFactor, I have the chute, the jolly logic, the featherweight, and the eggtimer apogee and I'm going to do some dry fits of all them. I'm willing to give up on flying with a Loki K to fit all the laundry and hardware in.

Is the Jolly Logic the Chute Release - or just one of the altimeters? The Chute Release would be a big help on the deployment scheme,
but its arrangement and the chute packing are key.

 

[emmah]

Is the Jolly Logic the Chute Release - or just one of the altimeters? The Chute Release would be a big help on the deployment scheme,
but its arrangement and the chute packing are key

It's the chute release. I'll be fitting it with a thin-mil Top Flight 30" X-chute, that'll guide the head end vs. spit decision.

As a coworker reminded me this morning on Slack, about a unrelated design problem, "the churn's where all the interesting stuff happens."

 

[QFactor]

It's the chute release. I'll be fitting it with a thin-mil Top Flight 30" X-chute, that'll guide the head end vs. spit decision.

As a coworker reminded me this morning on Slack, about a unrelated design problem, "the churn's where all the interesting stuff happens."

Nice choice on the chute.

Have you experience with the Chute Release?

 

[emmah]

Yes, the chute release is one of my go-to bits of kit. This will be the first time I use it in conjunction with electronic deployment. I have to put together that egg timer.

I spent a half hour test fitting things and I believe I’ll be able to fit it all in. But still need to measure all the things.

 

[emmah]

Three updates.

My local club had a low power launch in Hollister (not too warm, but very sunny, and windy in the afternoon.)

• Flew the chute and release with a F67 on a Piercer Mini, the chute popped, after it landed in tree. (got it back)
• Flew the Featherweight tracker so I could get some experience with it



I need to do another flight with the chute and release on the Piercer Mini to correct issues.

 

[emmah]

Third update:

The Haruomi Hosono and Yukihiro Takahashi reissues I ordered from Light in the Attic arrived today.

Hosono and Takahashi's solo work, as well their work together with Ryuichi Sakamoto in YMO (Yellow Magic Orchestra) were a great influence on City Pop and Vaporwave.

 

[David_Stack]

"batonnetes d'artisanat". So much more 'artistic' than "popsicle stick"

Long live vinyl!