I thought I'd start a thread for this project.

40% upscale of the Centauri Engineering Centaur, a two stager which was offered from 1965 to 1971.

I bought and measured and started to cut the parts for this several years back. The ST-175 tubes were starting to get scarce . . . or perhaps I had the Aerotech 1.88" OD tubes (close match) on hand and thought I'd use them up.

I'm building this with 29mm mounts, sized for the 29mm Estes BP motors.

Fins are 3/16" balsa. Because they are made from multiple pieces I'm going to paper them.

Attached Thumbnails

   

__________________
NAR #27085 - Oregon Rocketry - SAM

I should have simmed out this project from the start. I didn't realize how "mushy" the F15-0 was. It might have worked out that a 24mm D12-0 or E12-0 to D12 or E12 sustainer might have worked out better.

But I did a rough first pass, and things look good. 2200' altitude, 2 calibers stability.

I'd fly this under PERFECT condiditons, from a nice long rod.

Attached Thumbnails

   

__________________
NAR #27085 - Oregon Rocketry - SAM

Aaah!

Just several nights ago I started a vintage Centuri Centaur. Always did like the design, and the fins are very classic Centuri! BTW, I noticed your note about the project in your Aerodart project posts and you mention ST-8 and ST-13 for the Centaur. The original Centaur was ST-10 to ST-13.

Good luck on the upscale...should be a hoot!

Earl

__________________
Earl L. Cagle, Jr.
NAR# 29523
TRA# 962
SAM# 73
Owner/Producer
Point 39 Productions

Rocket-Brained Since 1970

Thumbs up on ST8/ST10 confusion. I had the scale-up notes with correct everything listed, but left it downstairs and was in a lazy mood this morning.

I have a Semroc Centaur waiting for its fins to go on. Something that has been holding me up is a lack of a decent fin alignment guide. I have had bad luck with the Semroc method of putting the end of the body tube on a printed compass. I'm going to see if can print out a wrap-style guide with Open Rocket.

* * *

Downstairs: I glued the parts of the booster fins together, sandwiched them between waxed paper, topped with a sheet of thin plywood, put a thicker pice of plywood over that, then put a 6 gallon water can atop that. They're staying flat!

Glued the centering ring template from Open Rocket onto a piece of 1/16" basswood, and gave it a similar weighted-down treatment.

__________________
NAR #27085 - Oregon Rocketry - SAM

Maxi-Centaur build continued:

While filler and glue on fins and laminated centering rings cure in the sun, I used a drill press and Dremel tool (burr and sanding bits) to hollow out the nose cone and transition section, to lighten things up a bit.

Times like this, I wish I had a laser cutter or CNC machine. Cutting centering rings with a scroll saw is a PITA.

Attached Thumbnails

     

__________________
NAR #27085 - Oregon Rocketry - SAM

I decided against papering the upscale Centaur's fins.

Instead, I'm clothing them!

The light window-shade fabric I found at Joann's keeps its shape nicely during cutting.

In addition to the joint between the fin halves, I'll glue strips over the leading and trailing edges.

Attached Thumbnails

   

__________________
NAR #27085 - Oregon Rocketry - SAM

Maxi-Centaur build continued!

I've been gluing on fabric swatches as needed, notably to the trailing edges. Also filling gaps with filler and clothing over those.

I discovered that I mis-measured the distance between the surface of the body tube and the motor mount tube. So the tabs on eight fins is about 3/32" short.

So I cut narrow pieces of 1/8" stock, which I'll waffle-cut and then glue to the fin tabs.

I also planned and started making the launch-lug standoffs. One for the booster, two for the upper stage.

Attached Thumbnails

     

__________________
NAR #27085 - Oregon Rocketry - SAM

I am almost done fabricating the parts of the Maxi Centaur. I need to trim the root edges of the fins to make through-the-wall tabs. (I added 1/4" to the root edges, and added strips to increase that by 1/8".)

I was going to add a launch lug standoff to the booster, then realized that the fins of the Centaur MUST be interdigiated. So the booster launch lug will go on one of the fins.

Lots of parts!

Attached Thumbnails

   

__________________
NAR #27085 - Oregon Rocketry - SAM

Looks like it is coming along! Kinda looks a little like a two-stage Centuri/MiniMax Lil’ Hustler! Good progress.

I am pretty much at the same point on my ‘regular size’ Centaur that I started right about the same time you started this project. My kit had some *very* hard balsa fin sheets from which to cut the pre-printed fins! I had to change blades in my Xacto #5 and #1 handles a couple times each. Uuuhhggg!

Good luck on the rest of the build!

Earl

__________________
Earl L. Cagle, Jr.
NAR# 29523
TRA# 962
SAM# 73
Owner/Producer
Point 39 Productions

Rocket-Brained Since 1970

Maxi-Centaur build continued!

I weighed the parts of the payload section, after priming but pre-painting. I'll weigh them again after a few coats of paint go on.

I'll plug in the masses into Open Rocket to see how stability and performance change from the rough run I did earlier. (The transition and cone were partially hollowed out, and a coupler epoxied to the transition's shoulder.)

I cut the slots in the body tube and tested the fit of the tabs. Still a bit of sanding required.

I fitted all the fins in to get a first look at what the final model will look like.

Attached Thumbnails

     

__________________
NAR #27085 - Oregon Rocketry - SAM