Gnosis - a 54mm bluefin tuba

I figured out a workflow that sensibly lets me post camera images from my work computer, so here we go.
Lot of time without support calls, especially weekends...

Ingredients: One 4ft 54mm piece of Blue Tube, one plastic 54mm nosecone, plywood, 38mm MMT, assorted other hardware.

This rocket will probably be flyable on a wide range of motors -- if Ari's original builds are an indication, she may do ok from Mach+ on a baby J all the way to around a E depending on actual build weight. I also like the idea of using this rocket for my L1. Posting in midpower because I can afford to fly those more often and I'm trying to keep weight down

Cut the Blue Tube on a chop saw, first to length and then with a 30 degree miter. I wasn't being careful about measurements, focusing more on repeatability. There exists an aborted first attempt at this where I learned tube fins need to be cut to exactly the same length, and are easy to misalign.


To get the first fin aligned in parallel with the body tube, I placed the fin and the BT flat on a piece of plate glass. Mk1 Eyeball apparently isn't good enough for me, and a crooked first fin makes the entire assembly spiraled around the BT.

Yes, I'm using white glue.


Looks quite good withe the nosecone dry fit on top.


Bondo'd. Some of the spirals may still show after the first coat of primer -- well, that step includes the instruction "iterate" for a reason.

For this one I'd like to try my hand at a baffle. The body tube is 22 inches long and I don't want all of my laundry sliding backwards. Having access to a lasercutter is pretty excellent, though this plywood cuts slowly and has massive charring. Probably the wood density, or the glue... 1/8th birch ply seems harder to cut than 1/4 inch hardwood. Foil tape should protect from the ejection charge, right?

(you can't see it in the image, but some scrap balsa is holding the correct spacing/orientation for insertion.)

Straigtforward 38mm motor mount, eight-ish inches long. I'll epoxy those 4-40 screws in to both the motor mount and body tube. They'll provide a stable hardpoint for retention since there's isn't a lot of room for a threaded anchor in the centering ring. I'll probably reealuate for my next bird, but in any case the MMT is already epoxied in.

Ach, OS X is lying to me about the image rotation... dear computer, don't display as vertical unless the image is actually vertical.

Looks great Zero.

Dang it! Never had a tubefin rocket before-you are an inspiration! Thx-ZI!

Ok, I've decided to change the name to "Gnosis" (from "thelassaphobia") because the old seemed a bit dismissive of an actual problem people have. Are thread titles editable?

No other updates, no work done.

The next step is to attach rail buttons but I don't know how I want to standoff them to clear the ID of the tube fin.

Interesting name change, Zero.

Brings up memories of Gnossos Pappadopoulis in Richard Farina's novel "Been Down So Long It Looks Like Up To Me"

Gnossos said:

“SHAZAM!” He was up on the table, making a noise like a thunderclap, then with a bound into the middle of the dining room, pointing a finger at Harold Wong. “Beware the monkey-demon, Wong.” Then to all the startled faces, their every expression chilled stiff, interrupted: “Lock your doors, gang. Bolt your bedroom windows. He may be the house mascot now, but in ten years, zoom, back to Peking, a commissar. Swoop . . .” He was out the door, flapping his wings like a bird trying to fly. . . .

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Looking forward to seeing who the build goes now that you have found a worthy name.

To answer your question, I don't know if it's possible to change the name of a thread.

advanced edit first post is where you can edit the thread title .
Rex

advanced edit first post is where you can edit the thread title .
Rex
p.s.
looking good, just got tired of looking at it sideways
R

Thanks -- thread title changed. Dunno how I missed that!

Also hopefully "Gnosis" will be a bit easier for the LCO to read off my flight card. Maybe.

Seeing as before Ari's Bluefin, most everyone believed it impossible to break Mach with a tubefin, BOTH names are highly appropriate, but I do like Gnosis!
Ari should copyright his ideas, I believe that there will be a lot of Tubas out there soon (erm, like the one I am building.....)

Salvage-1 said:

Seeing as before Ari's Bluefin, most everyone believed it impossible to break Mach with a tubefin, BOTH names are highly appropriate, but I do like Gnosis!
Ari should copyright his ideas, I believe that there will be a lot of Tubas out there soon (erm, like the one I am building.....)

Click to expand...

Yeah, I'm building one too.


Sent from my iPhone using Rocketry Forum

This build isn't dead, merely hibernated for a while!


Drilled rail button holes. Looks like adding another stacked rail button washer will be plenty of a standoff to clear the ID of the tubefin.


Whoops. First hole hit the buried head of the screw I'm using for motor retention. Fortunately, this was easily patched with bondo.


Meanwhile, the planned baffle was giving us no end of trouble. Turns out there are several very good reasons they're built into short coupler sections. Instead, I did the Loc thing and epoxied the shock cord directly to the airframe.


Set out on the apartment's back porch for priming. A second-story apartment is less than ideal to build rockets out of, but we use what we can, right?


Here's after two iterations of prime, sand, and bondo. Should need one more quick sanding pass before colorcoating. Unsure of the final color scheme, but it'll definitely have purple.

Unless something unexpected comes up, I'll be flying this rocket for my L1 Cert at Fire in the Sky next weekend.

Is this going off a rod or a rail?

Kruegon said:

Is this going off a rod or a rail?

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1010 rail. I'll be sure to get a picture with the buttons on for ya

Painting begun.
A challenge: figure out where on here the paint is being laid down


Can I request a mod move this thread to high-power? Seems weird having a rocket with a 38mm hole in midpower.

I know, I know! You're making the fins blue so this would be a true bluefin!

Oh, wait, there's masking on the fins. I give up.

Ari.

Maybe the insides of the fins?

I've got a couple of rockets with 38mm mounts that are mid power...I will admit that a big bertha really scoots with a G67 . nice shade of blue.
Rex

SCrocketfan said:

Maybe the insides of the fins?

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Nailed it Now of course I need to mask off the inside of the fins, and that's proving challenging. I don't trust the pemtec "put some rolled up paper in there" method to not bleed.

Zeroignite said:

Nailed it Now of course I need to mask off the inside of the fins, and that's proving challenging. I don't trust the pemtec "put some rolled up paper in there" method to not bleed.

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It does work pretty well, bleeding was minimal. Just used it on my King Kraken two months ago. Maybe if you put Frog tape around the insides of the tube fins before putting the rolled up paper? Looks like the tops of the fins are square, which would make them easier.

Interested to see the results.

1. Spray the entire body and tube fins inside and out.
2. Mask the entire body and mask off the tops and bottoms of tube fins prevent trim color from fouling the basecoat.
3. Spray the fins with trim color.
4. Remove masking.
5. Clear coat entire airframe.

Painting the exterior of all tube fins with the base coat and applying trim color to the INSIDE of the tubes requires a reverse method. If the trim color is darker than the base color, just spray the entire airframe with base color and then mask everything so you can spray the interior with trim color. This requires more work and IMO doesn't yield results as good as having external trim color but to each his/her own.

That looks sharp!


I did it the other way, masking out the inside of the fins, first with Tamiya masking tape (expensive but excellent) around the edges, then filling in the rest with big blue masking tape. I trimmed down very close to the edge of the tube fins to prevent shadowing on the body.


The final result looks really, really good. This rocket gleams (hard to see in photos).

Now I'm working on surface prep on the nosecone. It'll probably be painted a nice medium blue.

This Testors lacquer paint is actually really nice. All of them have a metallic glint, and they have great coverage. There's a surprising amount of paint in the teeny cans, too.

This looks like a pretty cool rocket! I put together a quick open rocket file of this, (I guessed on the fin measurements, but should be close). Hopefully, I was able to attach it correctly. I just may have to build this!

Phil L.


View attachment Tubefin.ork

From Ari's posts on the Bluefin Tuba, it seems like the exact dimensions are really forgiving. I eyeballed this one.

This rocket has now flown extremely successfully, and I've earned my L1 Certification.

More tomorrow, when I have energy and youtube has done the video processing.

That's awesome!

Ari.

Zeroignite said:

View attachment 263779

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That's a real perty rocket! I like the contrast of colors!

Congrats!

When finished, the paint looked really good. I got several compliments on it at Fire in the Sky


Kruegon, here's how I have the rail buttons attached. It may be hard to see, but the top (near) button has a second black washer stacked against the BT, providing a bit of stand-off.


Final dry mass was 580g. Lookin' good on the pad.


First Flight was on an Aerotech G76 Green. She was laser-straight off the pad in the calm air, without the slightest hint of wiggle. Someone else found and recovered the rocket before I did (it landed behind a hill, so I didn't get a clear heading landmark). One thing that surprised me was how little the flight seemed to affect the rocket; I'm used to rockets that looked scuffed, dinged, and dingy after flight, but Gnosis was clean and only had a tiny scratch from where the rail brushed the inside of the fin.

I did a certifying flight on an Aerotech H170 Metalstorm. My girlfriend got some iPhone video
[video=youtube;svxeHGaId-Y]https://www.youtube.com/watch?v=svxeHGaId-Y[/video]

I was really surprised at the altitude Gnosis reached, and how quickly -- OpenRocket predicted just shy of 3,500ft which I figured was overly generous. This time there was some subtle weathercocking. Unfortunately, near apogee I lost the smoke trail against some grey clouds, and never regained visual on the rocket. Someone else recovered it while I was searching in circles around camp. I am definitely spending money on a tracker next. In any case, L1 Certification achieved! I'm glad to have certified on a scratchbuild.

This rocket flies really, really nicely, and will hopefully be a fleet staple for a long time.

Congrats on the cert, and for creating such a beautiful bird. That is a rocket to be proud of.