Estes M.A.V. #7283, Build Part 4, Fin Can

The instructions show tube type plastic cement. I used brush-on liquid cement.

The fin can halves were pressed together dry.
The internal joints were brushed with the liquid cement while holding the joints closed and tight. Just the internal joints and at the top and bottom of the fin can got brushed on glue.

The fins slide into the bottom of the slot and are pressed up, locking them in place.
TIP: You really don't have to glue these fins in place. With the fins off you could easily fit this rocket in your range box. Slide in and lock the fins in place with the retaining ring at the flying field

On the left, the black ring isn't screwed all the way up yet. Notice the little bit of the slot still showing.

On the right, with the ring tight the fins are locked in place! They can't move up or down.
You could glue the fins in place but why? If a fin were to break, you've got a much easier fix.

Little Green Man With Stand!

On the Facebook Model Rocketry Fanatics page, David Koo posted:

"This was a really fun build!!! Little Green Man by Odd'l Rockets. The stand was 3D printed. Can't wait to launch him!"

Great, clean build David! I've got to admit, that's a very appropriate display for the L.G.M.
The rocket always has vertical flights - except for this past Sunday! A wind gust and launch rod tip-off sent him West.








To get to the 3D print files: CLICK HERE

Centuri Argus #KB-9, Fin Can From Thingverse

In a blog comment, Metalhead 1986 let me know:
"For those with 3D printers, the fin can is available on Thingiverse."

To go to the web page: CLICK HERE
Thanks to Jack Hydrazine for all the hard work.

The webpage also listed all the models that used this fin unit:

ENERJET: 1340 Sounding Rocket, 1340/20 Sounding Rocket

CENTURI: Phoenix Bird, Argus, M.A.R.S. Project
ESTES: Longshot, Maniac, Challenger II, Eliminator, Eliminator XL

3D Printed Parts?

On the Model Rocket Fanatics page on Facebook, Mark Foster provided a link to a Shapeways 3D rocket parts vendor - CLICK HERE

The work is impressive but I have mixed feelings about 3D printed parts. If you've seen the 3D print process you know production is slow. The parts are expensive.
3D parts have their place but I prefer a building challenge, not total pre-fabricated parts. On the forums a few posts infer; "Look what I built!" Well, you assembled a rocket. You didn't actually "build" something. I have built rockets from scratch and from kits.

3D parts do require cleaning up, there are ridges left from the plastic layering. The few 3D parts I've worked with required too much time to file and fill. Detailed fin cans (with bolts and straps) are difficult to smooth out without sanding down the bolt heads.

Like I said, these have their place but I won't pay that much for something I can do myself.
15 years ago I was building banjos. The resonator and metal parts were pre-fab. I still had to design, cut out and set all the inlays. Binding, fretting, sanding, filling and assembly were all part of the process. Even though I've played banjo for years I learned more about the instrument by building one. I think the same thing applies to rocketry.

Centuri Astro 1, Build, Part 4, Nose Cone and Fin Prep

Take an extra moment before screwing in the screw eye.
Mark the center with a pencil. Rotate the nose cone and chances are that first mark won't be perfectly centered. Mark the center again.

TIP: When screwing in the screw eye, go slow.
Screw a full turn, stop and check the alignment. Be sure it is going in straight. If you catch a crooked insertion early you can correct it before turning it in all the way.

TIP: The nose cone is a over 5" long and very pointy. In past experience, pointed balsa nose cones seem to get hit and blunted.
I'm building two kits as once.
The nose cone on the left is the before, on the right is the second cone rounded off. The later Centuri Astro I kits had plastic nose cones with rounded tips.

TIP: The balsa fin stock was slightly different between the two kits.
To match the density and grain the fins were grouped and marked on the root edges.

With this unusual fin shape it's easy to round the root edges by mistake. That was a problem with the Asto I fins. Many first time builders glued them on wrong, looking more like the Estes Alpha. I found myself almost rounding the wrong (leading) edges.
Marking the root edge tips made me stop, reposition and sand the correct sides.

New Concept 3D Printing

3D Printing takes a big step forward!
To see the short video, CLICK HERE

It looks like the piece is drawn out of a heated plastic tub.
Faster and no ridges to sand off!

Shapeways Fins

More and more 3D printed fin units and nose cones are available through Shapeways.

I found this one interesting from the Aerobotix pages. It's a three engine 13mm cluster that fits a BT-60 fin can.
To check out the other offerings: CLICK HERE

For lots of classic replacement nose cones and scale model fin cans.

3D Printed V2 on TRF

MrBill2u Posted this on TRF.
Now 3D printing gets very interesting - 

"There is a member of these forums by the name of Raygun who has a shop set up at Shapeways for 3D printed rocket parts. This is a tiny build thread for his BT-55 V2.
Check out the V2 fin can at the Shapeways website HERE
All the available rocket parts: HERE 
Things get interesting on Page 2

Here is a shot of the nosecone and fin can together. I shouldn't have any difficulty coming in under the 3 oz limit of an A engine with weights like this.

The build itself was 10 minutes. I tied the shock chord in a loop, wrapped it around the motor mount, slipped the centering ring on it and tacked it down with CA. I also tacked the nose cone pin with CA on either side. I mixed up some 5 minute epoxy and used it to secure the centering ring and then applied some to the tail cone aft section and tail cone built in centering ring. I inserted the motor mount and left just enough protruding from the back to run a small bead of epoxy around it. I then applied epoxy to the shoulder of the fin can and the inside of the air frame and slid it together. If I had 30 minute epoxy on hand I would have taken some pictures of the build, but the 5 minute clock did not allow for photography. 

Here is the completed rocket coming in just short of 12". I should get a chance to at least get it filled and primed this weekend."

The 3D printed nose cone and fin can are BT-55 based.
This makes this V2 the same size as the old Estes kit.

I have a feeling a few new rocket part companies will be springing up.