21-inch by 19-foot "Unfinished Business"

[Feckless Counsel]

TRF,

My first large build, "Anima Mundi", failed by CATO. This is "Unfinished Business."

Goals for this build are:

3FNC configuration
20.75-inch diameter
19-foot length
64.25-inch span
150-pounds pad weight
N3301 motor
4500-foot AGL apogee
L3 certification

Lessons incorporated from Anima Mundi include:

Wall Thickness - will use Spheretex bulker matt to increase airframe wall thickness to 0.125-inch. Result will be an airframe 4 times as stiff. Layup schedule will be 2 layer of 7628 glass, one core layer, followed by three layers of 7628. Projected weight after sanding and paint will be 11.25-pounds per each 48-inch section.

Vacuum Bagging - as there is no better method of assuring a strong, fiber rich composite. That is especially true using 7628 cloth. Concern here is for wrinkling airframe's layup. I'll need a tight mass before bagging over the cylindrical mandrel. Experience anyone?

Mandrel - will be commercial concrete forming tube. Custom mandrels, as in Anima Mundi, are not warranted here. Choices are 20.55-inch OD and 22.6-inch OD Sonotube. I'm going with 20.55-inch consistent with the bigger but lightweight goals of my research. Appologies, that is 1-inch smaller OD that before.

Nosecone - no more Russian movie surplus. This will be a 4:1 ogive cone formed on hot-wire cut EPS core. That is going to be challenging as I plan a similar core and skin construction.

Fins - last time I used 0.75-inch scrim coated balsa panel with 5.8 twill carbon post lamination. That was incredibly stiff but just a bit heavy. This build will follow the same schedule except thickness will be 0.5-inch for a 20% weight savings.

Balsa Leading Edges - are too soft so I'll be using the same profile in basswood or poplar as can be provided by suppliers.

Motor Tubes - phenolic motor tubes are not necessary, are expensive and add significant weight. This time I'm letting the motor case ride on centering rings. Root edge of the fin tab will be unconstrained by adhesive. Comments are welcome.

Option 1 - in deference to Dan Patel I'm seriously considering a 150mm central mount and homebrew 98mm adapter. Thanks to Dan for tangling my mind.

Option 2 - laminated end-grain balsa centering rings and bulkheads will be considered as budget allows. I really like that material!

Very best regards,

Feckless Counsel

 

[dixontj93060]

Geoffrey, have to hand it to you. Looking forward to this effort. A couple of questions though... What if any from Anima Mundi was salvageable after the CATO? I you didn't experience the CATO, do you believe the airframe would have held up?

 

[blackbrandt]

Did the nose cone survive?

 

[cwbullet]

wow, did I read 130+ lbs. I can't wait to follow this build. What motor are you planning to use?

 

[Feckless Counsel]

Tim & Blackbrandt,

Absolutely nothing survived the ground fire - nothing! But that's of no concern now. Only thing matters is this build.

I do think the airframe of Anima Mundi would have survived the flight. Still, I think it can be improved. We rocketeers are forward looking. Better is the thing. Won't you agree?

Feckless

 

[dixontj93060]

Won't you agree?

Yep.

 

[blackbrandt]

Where do you guys get the money to fund these!?!?!

 

[eggplant]

Where do you guys get the money to fund these!?!?!

Having a job.

 

[Rocketjunkie]

wow, did I read 130+ lbs. I can't wait to follow this build. What motor are you planning to use?

N3301, see first post. Even with an N, with a rocket this size and weight, it will be a lob shot :wink:

 

[cwbullet]

Sorry. I read that twice and just missed it. It should be an awesome flight.

 

[gary7]

And I thought my last two projects were ambitious, aggressive and impressive! WOW! Best of luck with this one Feckless. Hope the results are more favorable.

 

[Rocketman248]

Where do you guys get the money to fund these!?!?!

I remember those thoughts well. I wasn't into rockets at your age, but I was obsessed with guitars. I remember thinking that I would never be able to afford to have any fun. Just hang in there, dude. Keep the passion alive as you get older, and as you progress in your jobs/career, the bigger paychecks will start to come in.

In the meantime, you can still have a lot of fun with low/mid power with the occasional high power flight.

 

[jsargevt]

Having a job.

+1 for sure. I have a job and I cannot fathom how I'd fund this.

 

[CarVac]

Is wrinkling a problem with such large tubes? I know from my attempts at 38mm that wrinkling at that size is nearly impossible to eliminate with multiple-wrap layups, but the percentage change in circumference from a given diameter change (from compression) is much reduced at 20-inch diameter.

On the other hand, having a core makes it compress a lot more under full vacuum, so the diameter change will be increased when compared to 3-layer 3k CF layups on a 38mm mandrel...

 

[JStitz]

Feckless,when I first saw bbs post about that heavy prop cone I said no way..he's goin' Foam core stack.
Do you have a hot knife now? Do they still build these from old Model railroad transformers?

 

[Neuport]

Do they still build these from old Model railroad transformers?

And automotive battery charges among other power sources. I've built a couple with battery chargers and light dimmer temperature control.

 

[Aksrockets]

Whoa. The size of the rocket simply dwarfs the N motor, which is the size of the rocket I am currently building. Sorry to hear about the cato.

Alex

 

[THarrison]

Really glad to see you are rebuilding and look forward to the thread.

I wholeheartedly vote for a 150mm mount "just in case" you find somebody that might want to give you a 6" EX motor to fly. :wink:

-Todd Harrison

 

[bandman444]

I'm seriously considering a 150mm central mount and homebrew 98mm adapter.Feckless Counsel

Perhaps you have seen my 20inch Squat thread. But I did decide for the 150mm main mount.....I also added 3 98s for future fun.

 

[Quaranta]

Very cool. And I admire your ability to persevere!

Not to mention that I get to torment my wife by showing her your builds.

Her: Your not thinking of building one that big are you?
Me: Well I measured the garage,... I can go much bigger than that without you loosing your packing spot. :y: :wink:

Have fun. I'll enjoy following the progress.

 

[blackbrandt]

I would cram in a 150" motor mount. Maybe a P motor someday?

 

[butalane]

+1 on 150mm motor mount.

Have you considered shrink tape over vacuum bagging?

edit: I realize some consideration would be needed for this including tube support and a viable heating method, luckily ovens are not the only way to shrink heat tape - but the operation would leave you without wrinkles.

 

[CarVac]

That would be difficult to do on a 21-inch tube. You would need an incredibly large oven to fit the tube sections inside, and then it has to heat at least somewhat evenly.

 

[GregGleason]

The name "Unfinished Business" totally rocks!

Has that "I'll be back" undertone.

Greg

 

[jsargevt]

Very cool. And I admire your ability to persevere!

Not to mention that I get to torment my wife by showing her your builds.

Her: Your not thinking of building one that big are you?
Me: Well I measured the garage,... I can go much bigger than that without you loosing your packing spot. :y: :wink:

Have fun. I'll enjoy following the progress.

Ironically my wife keeps asking me when I'm going to build gigantic rockets like this. She tells me that I can park my car outside for it.

I tell her when we win the lottery I'll start gigantic builds. I am looking forward to watching this build.

 

[SMR]

The name "Unfinished Business" totally rocks!

Has that "I'll be back" undertone.

Greg

You can't keep a good man down. Looking forward to the build and the flight.

Sather

 

[Feckless Counsel]

TRF,

Thanks to you, everyone, for your contributions to this project. Your enthusiasm buoys my own.

May I focus on the issue of wrinkles from a vacuum bagged cylindrical mandrel? Do any of us have DIRECT experience here or am I cutting new turf?

Feckless

 

[Feckless Counsel]

Blackbrandt,

You asked about budget so I've attached a scratch sheet total for this project. Rockets fail and, at this scale, you must consider sponsorship, team efforts or a sugar-mama. Whatever it takes, right gents?

Feckless

 

[Eric1]

Yo Feckless!
I'll donate a couple of unistrut guides to help.

Send Address to my email or pm.

 

[Feckless Counsel]

Eric,

Thanks and I appreciate your generous support. PM is on the net. Is it acceptable to have your decal displayed on the project? That is a lady for sure!

Feckless