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(BAR-47) UK's Black Arrow - With Gas Dynamic Stability (GDS)

I saw @Raptor 2 's version of this rocket here... he's using clear plexiglass fins to make the rocket stabile... I attempted to get him to axe the fins, using instead Gas Dynamic Stability. He was having none of that.

So I figured what the heck, I'll build a smaller version and try it myself.

This is a really simple BT-52H and BT-60 rocket powered by a 24mm motor. Rear eject motor and chute with room in the Nose Cone for an Altimeter Two.

It'll be silo launched from a PVC tube.

Building a GDS rocket is kind of a crap shoot...

A) In Open Rocket I add fins, with a weight of 0 grams, to get an altitude reading. Of course there aren't really any fins.

B) I added a bit of Nose Weight, just because it's always better to have it since we're not going for any altitude "records".

C) The GDS works via the perforated shell section at the base of the rocket. This allows the motor exhaust to pull in outside air, which stabilizes the flight during thrust.

D) I canted the existing nozzles on the transition at 10 degrees. This allows the rocket to spin which stabilizes the rocket during the coast phase.

Should be a fun build and flight.

2025-05-03 Nose Cone

Turned the Nose Cone from some scrap Southern Yellow Pine... the good hard stuff. Well hard for SYP anyway.

2025-05-04 May The 4TH Be With You....

Turned the Transition on the wood lathe.

Had to make two, first one I got the bore off center. :facepalm:

I discovered the key is to bore the I.D. undersized, and then cut it free hand to the correct size.

The Transition will be glued onto the O.D. of the BT-52H. Gives a good sturdy base to attach the Spin Tabs to.

CAD Model and Preliminary Drawings

2025-05-05 Assembly Day 01

Cut the tubes, found some Centering Rings in my scrap bucket, and started gluing...

(BAR-46) The Lucky 7

I got this design from a fellow rocketeer over at TRF, whose member name is Babar. Here's a link to his original design... 2FNC--- 2 linear fins and a nose cone. The Lucky 7

I thought I'd take a crack at making one of these that'll fly on 24mm motors. It's got a place for my Altimeter Two and will handle any Estes or Aerotech 24mm motors. Some dowels were added on both sides of the fin, and it also has doubled up body tubes, just to ensure longevity. I'll use some 2 ply's of 1/16" thick Basswood to make those 1/8" Basswood fins.

The plan is to start with the D12-7 BP motor... and work my way up to the Aerotech F32T-8.

2025-04-24

Got to spend a little quality time out in the barn this afternoon. Turned the Nose Cone and Transition on my wood lathe.

2025-04-25

Body Tubes, Mock-Up, Lag Screw Eye, and Gluing Begins

2025-04-25

Adding the fin dowels and building the triple tube BT-52H

There are 3 pieces of BT-52H in the triple wall fin can. The outer is an intact tube, the two inner tubes were cut twice longitudinally to the correct O.D. and then they were glued and inserted into the outer tube.

2024-04-27

Cut the BT-3 Launch Lugs, Sanded the Fin Dowel, punched vent holes in the tubes and sanded the Motor Tube. Glued the Fin Can Launch Lug.

Gluing the BT/C-50 to the Transition, and attaching the Upper Fin.

By printed the "Back View" of the OpenRocket model, a couple of temporary cardboard angle templates were made. Those were taped to the Lower Fin. That'll hold the fin in place, at the correct angle, while tacking the Upper Fin to the Lower Fin with wood glue.

2025-04-28

Gluing the Upper Fin, Motor Ejection Tube and Final Assembly

The temporary cardboard supports were removed this morning and the Fin Dowel was inserted into a bed of Wood Glue. Glue fillets to follow.

The Ejection Tube, a piece of BT-50H, was placed on the mandrel of my wood lathe and the white paper layer was removed. This makes for slip fit into the fin can. I don't really want any friction at this joint, the motor needs to eject and the lanyard straps of Kevlar will yank this tube and the laundry from the rocket... or at least that's the plan anyway.

I'm contemplating doing a static test of the recovery system...

Also finishing up gluing all the pieces together...

CAD

Created the model and started on the drawing package.

2025-04-29

Revised the Ejection Tube... actual parts and new drawing set. Gluing on the Upper Launch Lug.

2025-05-01 Swing Test

Just when you've got this whole rocketry thing figured out... you realize you don't. I swing tested the rocket today and it was not stable. No matter the orientation, it just wouldn't fly nose first reliably.

So the nose cone was bored for a 3/8" dia piece of ballast x 1.1" long, 15 grams.

That did the trick. Sim shows the rocket is now at 1.6 caliber or 10.6%. I think it was the % that bit this rocket, which I usually shoot for 8% to 12%... which it was under this time without ballast.

I tested the rocket in (3) orientations, all were stable, (1) is posted up here.