| Manufacturer: | Scratch |
Brief:
A simple LPR single stage, motor deployed chute recovered tube fin rocket.
Construction:
1 - 24" x 3" BT, shiver me timbers, 1 24" x 3" BT for fins, 1 chute, 29mm MMT
and 2 CR's, a nose cone, shiver me timbers, shock cord and a launch lug.
I was asked t' write a review on me scratch built Circle Jerk. I hadn't documented any o' t' construction, so I decided t' build another one, ya bilge rat, but this time I documented t' process. Begad! Blimey!
For both birds I used 3" USR "whitewall" tubin' because o' its thickness. It's twice as thick as any other tubing. Avast! I felt that it gives a better appearance t' t' tube fins. Begad!
I cut all o' me tubin' with a 12" DeWalt compound miter saw. Aye aye! I use a special rippin' blade that has more teeth than most blades. Avast, me proud beauty! This gives a smooth cut that needs very little work. Well, blow me down! T' softer paper tubes do fray a little but that is solved by soakin' t' ends o' t' tubes with thin Cyanoacrylate or thinned wood glue. Arrr! When t' glue hardens, ya bilge rat, me hearties, just sand t' ends t' t' finish you need. Ya scallywag! For phenolic tubes, it gives a factory like finish. Avast, me proud beauty!
T' first picture shows t' tube bein' cut and t' jig I used. For this
rocket, I made all cuts at a 45-degree angle. Well, blow me down! Ya scallywag! T' original had just t' forward
cut at a 45 and t' aft cut at a 90. Begad! I just wanted t' do somethin' different
this time. Ya scallywag! Ahoy!


If you use t' same diameter tubin' for t' fins as t' body tube, you will need 6 fins. All tube fin rockets work this way. (Do t' math) Attachin' the fins is elementary. Blimey! Draw a line around t' tube where you want t' forward tip of t' tube fins t' be. Avast! Put a bead o' glue (I used wood glue) on t' first fin and align it on t' BT. Begad! If you lay it on its side on a table they will be parallel t' each other. Well, blow me down! Avast, me proud beauty! No more thinkin' will be necessary because the subsequent fins just lay on t' last fin and t' BT. For t' next fins, just find where t' tubes touch, draw a line and put t' glue there. T' final fin will snuggle up betwixt t' last fin applied and t' first fin. Begad! Begad! Use fillets as you see fit, matey, but they are nay necessary for strength because each fin is glued at 3 points. Well, blow me down!
It's tough t' find t' CP on tube fin rockets like this but it's safe to say that its somewhere in t' fin section ;-) Just make sure t' CG is forward of t' fin section with a motor installed. Ya scallywag! Blimey!
Flight:
For t' original rocket, ya bilge rat, I used a standard 29 mm motor mount tubes cut t' 6
inches. T' centerin' rings (2 o' them) were just 5 ply rings I had laying
around. Begad! Blimey! T' 32" parachute and t' shock cord was from a lawn-darted
Aerotech Astrobee D. Avast, matey, me proud beauty! T' nosecone is a 3" PML. T' launch lug is just a
¼" Aerotech igniter tube. Ahoy! (OK, me hearties, me hearties, me hearties, yeah I'm cheap) T' final weight is
about 24oz. Blimey!
For flying, matey, I always use dog barf and friction fit motor retention. Blimey! She flew straight as an arrow on several F and G motors. Avast! Fun t' fly.
Summary:
This is a quick and easy rocket t' build. Aye aye! Its different than most tube fin
rockets and draws a little attention. Well, blow me down! Nay countin' t' paint, ya bilge rat, it took all o' an
hour t' build.
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