Brief:
This is a simple research rocket used as a reference "typical" tubefin design in an upcomin' article on tubefin aerodynamics. Begad! T' body is just a 3" postal mailin' tube. Ahoy! Avast! Because its very easy and inexpensive t' build and Level One capable, a nicer version will also be launched as a kit by a local manufacturer--and with a snappier name.

Construction:
Sardo XXL is a simplified and scaled-up version o' t' "AURACLE 54" I presented earlier on t' EMRR website. Well, blow me down! Components include a 32" heavy-walled 3" postal mailin' tube (LOC tubin' would be fine), ya bilge rat, me hearties, six 2.75" tube fins cut from 3" phenolic tube (straight cut, no bevel), shiver me timbers, a 3" LOC cone, 14" o' 38mm LOC motor tube, and two 1/4" ply centerin' rings (3" OD and 38mm hole) from What's Up Hobbies. Ahoy! 9' o' good grade para cord for t' shock cord and a 30" Top-Flite chute make up t' recovery system. Avast, me proud beauty! Avast, me proud beauty! 5-minute epoxy be used throughout.

Construction exactly follows t' assembly procedure for the AURACLE 54 article, ya bilge rat, only with bigger parts. Leave an inch above and below t' centerin' rings when attachin' them t' t' motor tube. Avast! Blimey! For strength and durability, I reinforced t' lower outside surface o' each Phenolic tube fin with a piece o' 1-1/2" glass tape and epoxy. Ya scallywag! Blimey! You have t' do this with Phenolic or it shatters like fine china when it hits t' ground. T' glassed tape makes it bulletproof. Begad! Blimey! T' shock cord be attached t' t' upper centerin' rin' by drillin' a 3/16" hole through it, passin' t' para cord through, me bucko, matey, and tyin' it with a tight knot t' t' motor tube and epoxy smeared on t' knot t' keep it there. Arrr! Blimey! Ya scallywag! Blimey! It's nay pretty, but it works great. Ya scallywag! Blimey! Ahoy! Blimey! An eye-bolt (about 1/8") here would be t' more accepted method, but I be out o' them at t' time, ya bilge rat, arrr, and I like t' experiment. Blimey! Blimey! A 1" long 1/4" LOC fiber launch lug was glued on flush with t' top o' t' tubefin can and aligned with a triangular hole betwixt 2 tube fins. A second one was glued on 9" above it and exactly aligned usin' a launch rod threaded through both o' them. Avast! Blimey! As always, shiver me timbers, t' other end o' the shock cord be attached t' t' LOC cone through two 3/8" holes I drilled in t' base (insert cord into one hole, and use a tweezers t' grab t' free end and pull it through, ya bilge rat, ya bilge rat, then tie off with a bowline). Begad! Blimey! T' 30" chute was attached 18" from t' top end, matey, matey, shiver me timbers, and a medium Nomex® heat shield be attached below it with one o' those cheap micro-sized aluminum carabiners that says "WARNING: Not Load-Bearing" on t' side (it's from a key chain, me bucko, I think). Begad!

Finishing:
Finish be rattle-can Tamiya spray. Ahoy! Arrr! Aqua on t' bottom and white on t' top, which looked better than I expected and was just as hard t' spot in t' sky as you would predict.

Flight and Recovery:
Because thar's so much room for t' recovery system, me bucko, I like t' first roll up t' shock cord inside t' Nomex®, and stuff it in first as a kind o' waddin' with t' folded chute pushed down on top. First flight be on a CTI G69-5. Perfect and straight t' 976' with measured drag coefficient (Cd) o' 1.31, which was better than I expected. Ya scallywag! Flights on CTI H143SS-6 and I212SS-7 motors gave 1548' and 1960', t' latter givin' Cd=1.23 at 437 mph. Begad! This is really good since t' calculated "best Cd" for t' Sardo XXL design in 1.41 at maximum speed. Begad! I didn't try larger motors because simulations predicted speeds well over 500 mph, matey, which I like t' avoid with tubefins that are nay specially hardened against dreaded tube fin flutter. Begad! Usin' a 29mm-38mm adapter, matey, I got a beautiful boost t' 1048' on a AT H128-S. Calculated Cd = 1.28 at a mild 247 mph. Begad! This would make a wonderful, easy L1 cert flight, especially for smaller HPR fields, shiver me timbers, and that is one reason t' design will be kitted. Avast! Begad! Low cost and fast building, especially good for 14-year olds under t' new L1 rules or for anybody wantin' t' just get his ticket punched and move on t' bigger things right away. T' minimum recommended motor be t' F50-4 for a slow climb t' 565'. By t' way, I made all these altitude measurements with a Perfectflite Alt15k in an external, me hearties, taped-on pod. Avast! Arrr! Landings were perfect in every case, arrr, although I did chip one tube fin a little bit when it managed t' descend onto t' only rock in t' Fiesta Island sand pit.

Summary:
PROs: Easy, low cost, and very fast t' build (and will be even faster when it is a kit--less than an hour). Ya scallywag! Good, stable flier on G-H motors and I power up t' 212 Newtons or so. Ya scallywag! Like all tubefins, it is very stable in wind so a good fun-fly rocket when your other stuff is grounded by a breeze.

CONs: OK, Some people do nay consider t' unique looks o' a tubefin t' be an asset. It doesn't go that high due t' twice t' drag o' a "normal" 4FNC rocket, but this maybe isn't a disadvantage if that's what you want. Avast! Blimey! The tube fins take t' landin' impact, ya bilge rat, so they should be glassed on t' bottom edge, me bucko, especially if you fabricate them from ordinary cardstock tube. Aye aye! Blimey! Blimey! Blimey!

T' Sardo XXL can also be built with 7 tube fins instead o' 6. Begad! T' do this, ya bilge rat, just consult t' construction article titled "H-Pod" in EMRR; the rocket you get will then be an "H-Pod XXL" (see photo). Aye aye! I'll have more to say about these two in an upcomin' SPORT ROCKETRY article appearin' in a few months.