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dhbarr

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Inspired by Kraken, Ular, Golden Acorn, Paralyzer, Bluefin Tuba, Six Pack and Serval ( I have a problem, I know that ).

But how to test? Unless someone wants to help me get the first one setup in OpenFoam, I'm a bit out of my depth on CFD. I've read plenty of whitepapers on gridfins, but no working examples.

Burning a bunch of g150's would do the job, but would run the bill up pretty quickly.

So anyway, I've just ordered a decent number of d21's. I think I can grind past mach1 & stay there for under $10 a pop, and break through transonic with d21-d10 staged.

"You're crazy!" I hear you saying. Yup, that's true. So after this round I'll upscale and compare/contrast 5,6,7,8 fins. Next stop, Mach 2?
 
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dhbarr

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I'm working on calculating constant fin area given different tube geometries; see what I've left out:
- square, which is a straightforward rectangle unrolled
- Kraken style, which is a straight delta
- plane-intersecting-cylinder, which is sinusoidal

I'll want to run each of these shapes on the front and back of the fins, in combination with each other possibility. Probably should run different calibers as well, but I'm really only interested from ~.25 to ~1 or so.

Thoughts? Angles which will be the most interesting?
 
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dhbarr

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I'm thinking about trying CF biax-uni-biax, should be strong enough for the fins.

For -retrieving- these tiny bolts of lightning, what are folks' thoughts?

Noseblow tethered with a tiny streamer is what I've come up with so far, and/or LED night launch w/ piezo buzzer.

Obviously I need to solve this part before attempting to put any mach-proving electronics in the nose :)
 

dhbarr

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Burned a d21-4t today. Wireless ignition system works well, peak thrust of 32N and all over in about 6 seconds.

We'll mark that as a success, plus I got to take apart the burned casing to confirm how everything is arranged internally.

Also took measurements to confirm boat-tail design. It -may- be possible to bring this in right at 1g / NPEAK , about an ounce AUW.
 
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dhbarr

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No progress report, got busy overbuilding a Sprint XL to take CTI 6g loads.

My Kevlar situation is sorted, so next up I think I'll grab some vulcanized 18mm from UMRS and really get started.

Sim results actually suggest d21 to an RC load, but the altitudes coming back are insane.
 

dhbarr

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Putting this one on hold to focus on the buildoff. More later!
 

dhbarr

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Merry Christmas!
tiny_tuba.png

Grr! OR keeps getting crazy on accel / alti, but solid charts on stability / cg-vs-cp.

As an aside, the tubefin option also has some nonsense results as you get under 1cm, as well as depending on how far up the BT one goes.
 
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