(BAR-31) Anduril Roadrunner
Here's a semi scale flying model rocket of an actual twin-turbojet VTOL Autonomous Air Vehicle.
2024-04-20
I created an OpenRocket simulation to determine the air worthiness of this model. I'm planning on using two D12 black powder motors.
Nose Cone Started with a 4 x 4 piece of scrap cedar. I lagged it to the headstock and turned the piece to 1-3/4" dia. and then bored a 0.90" dia hole x 5" deep. Then turned the shoulder for a C-55 and turned the taper.
2024-04-24 Motor Mount - Day 01
Two 24mm motors feeding into a BT-5 ejection tube.... so I needed some way to neck the ejection charges down. I took a piece of 3/4" plywood and made a header. I used plywood to avoid the wood splintering when the ejection charge fires.
Plan is to glue the two body tubes to the header, and to themselves, and then use some wood glue on the inside surfaces as fire proofing.
2024-04-25 Motor Mount - Day 02
Glued the 24mm tubes to the header, and started building fillets. Also started fireproofing the header internal parts with wood glue.
2024-04-26 Wings and Motor Mount Day 03
I cut the wings from 1/4" plywood and the Vert. Stabilizers from 1/8" Basswood.
2024-04-27 Gluing the Wings
Once I laid out the wings and the body tube I found that the motor mount was wider then the distance between the fins. So I modified the fins slightly.
The body tube was cut so the fins could glue to the inner coupling.
I used the 1/2" thick (actually 0.4375) plywood fin alignment fixture that I made for my Level One rocket. A few playing cards were added under the body tube to get the fins on C/L.
Wood glue was applied to the tube, then Wing #1 was set into it and removed. The procedure was repeated for Wing #2. The tube was placed in the fixture, and then the wings were set into place. The 12" Steel Scale holds the wings flat.
I fired up the CAD station and made a study drawing of the body to determine the front and rear chord lengths of the shrouds. Then it was an easy matter of transferring those dimensions to a piece of BT-80H tubing, and then cutting them out with some shears.
I installed a couple of 1/16" basswood supports inside of the shrouds to give the vertical stabilizers a double wall attachment for gluing.
As much as I hate to do it, I've redesigned a new motor mount to use a single 24mm composite motor. I'm not up for rolling the dice on the exploding Estes D12 24mm BP motors.
I was just looking forward to all the smoke and thrust flames from dual D12's... 
I still have the dual 24mm motor mount... maybe after she's flown a few times I'll use BP.
2024-05-01 Vertical Stabilizers
I cut the thru-the-wall slots and started gluing the vertical stabilizers. Started with the outside fillets... let the dry for a few hours...
and then filled the void with wood glue....
05-02-2024 Single 24mm Motor Mount - Day 01
Used the wood lathe to make the Centering Ring and Bulkhead for a single motor mount that's a spool design to slip into the rocket.
05-03-2024 Single 24mm Motor Mount - Day 02
Finished up the motor mount. Also applied some wood glue to the inner surfaces as a fire proofing aid.
05-03-2024 CWF And A Bonus
Applied a liberal amount of CWF to the wings fillets and air inlets. Also found that my Altimeter Two will fit - taped to the motor mount tube. Woot - Woot!
Well, it was symmetrical, but it's not any longer. I used (2) launch lugs and placed them near the rear. And here you thought I had forget 'em, didn't ya? 👀
I cut a 5/8" Dia x 4" long piece of steel to use as the Ballast. It will slide into the nose cone ahead of the spool, and eject out of the rocket with the spool.I then did two spin tests: One without the ballast, and one with the ballast. As predicted, the rocket is stable with the ballast.... and unstable without the ballast.
