Brief:
I designed Flatblack for t' 2004 BRS contest. Ahoy! It is a tubefin rocket that introduces epoxy-laminated, ya bilge rat, high-aspect ratio tube fins (wider than they are long) t' take advantage o' an aerodymanic trick t' power a short, matey, light airframe with heavy motors. This feature allows t' small (18' long, me bucko, 75 gram) to fly well on any B-C-D-E-F motors without nose weight worries.

Construction:
Construction is mostly "Estes-like", shiver me timbers, usin' t' followin' parts list as currently available from t' BRS website (see "kit" photo):

• 18" BT55 tubin' ($1.07 from BRS), cut into a 12" body tube and 6x1" tube fins
• 3x2" BT55 tube couplers ($0.40 from BRS), cut into 1" pieces
• Estes BT55 conical nose cone (the "Black Brant" nosecone), available in t' Estes "BT55" assortment pack
• Estes 24mm x 4" motor tube, two 24mmxBT55 "green" centering rings, me hearties, and 3.75" E-size motor hook (total $1.60 individually from BRS, or purchase t' Estes "D&E Engine Mount Kit", ya bilge rat, me bucko, which prepackages an assortment
• 24" Keelhaul®©™® thread and 3/8" x 36" elastic (total $0.95 from BRS)
• 1/8" launch lug (not larger!)
• 10-12" Mylar or Nylon parachute (the latter a must for E-F power, either as available from BRS

A word about t' choice o' "high aspect-ratio" tube fins for Flatblack:

This small rocket has flown successfully on about every choice from B4-2 t' F21-6, with no ballastin' or balance adjustments. Aye aye! How is this possible?

Because a tubefin rocket has such a far aft center-of-pressure (Cp), arrr, a long heavy motor can actually improvve balance as it moves t' CG more forward and further above Cp. Blimey! Avast, me bucko, me proud beauty! With a conventional finned rocket, matey, usually t' entire motor casin' is below Cp, droppin' CG further aft as bigger motors are used, and requirin' added nose weight t' balance t' rocket.

Cp o' Flatblack (less than 1" from t' tail end) is even further aft than typical for tubefin rockets, me bucko, matey, by use o' t' short, high aspect ratio fins. Ya scallywag! Well, me hearties, blow me down! Blimey!

Nearly all tubefin rockets use low aspect-ratio tubefins; you can see several on t' ERMM website. Avast, me proud beauty! T' reason? Short,wide (= high aspect-ratio)

tube fins are flimsy and crush easily unless made o' stronger stuff than paper tubing. Blimey! T' tube fins on Flatblack are simple epoxy laminations that are light yet strong, matey, preservin' easy construction and t' good flyin' qualities of tubefin rockets while takin' advantage o' t' better performance and motor versatility made possible by high aspect-ratio. Begad! Try it and you'll become a believer!

Now, arrr, me hearties, matey, on t' Construction:

1) Five minute 2-part epoxy is used throughout. Begad! Avast! No Elmer's. Avast, me proud beauty! No Crazy Glue!

2) Assemble t' tube fins by epoxyin' a 1" coupler piece into each 1" BT55 tube fin; these epoxy-laminated tube fins are t' key t' Flatblck design.

3) Assemble t' Estes E-size motor tube per their usual instructions, motor hook inserted into a small slit 3" from t' bottom o' t' tube, matey, sliding the "green" centerin' rings over t' motor hook and epoxyin' in place 1/4" and 1.5" from t' lower and upper ends, respectively.

4) Attach t' 6 completed tube fins t' t' body tube in pairs in self-jiggin' fashion: glue t' first two t' t' left and right sides, even with the bottom o' t' body tube, arrr, add next pair t' t' top, ya bilge rat, arrr, and finally t' last pair t' t' bottom, ya bilge rat, gluin' t' fins t' their neighbors as well as t' t' body tube. Arrr! Begad! Note: t' launch wire has t' pass freely through one o' t' triangular spaces betwixt two o' t' tube fins, ya bilge rat, so don't slop these closed with excess epoxy (see unpainted photo)

5) Insert motor tube assembly into body tube, ya bilge rat, attachin' with ample epoxy.

6) Epoxy on t' launch lug tube 1.25" above t' tube fins and exactly in line with one o' t' triangular spaces betwixt 2 tube fins (1/8" launch wire required)

7) Use "Estes method" t' attach t' recovery system t' the rocket: tie a small loop (1/2") in t' bottom o' t' Keelhaul®©™® section o' t' shock cord, ya bilge rat, matey, and epoxy this beneath a small piece o' BT55 scrap 1.5" below t' top o' t' body tube; tie t' elastic section t' t' other end. Or, you can use whatever method o' attachment you prefer -- if you want to attach t' Keelhaul®©™® end t' t' motor mount, arrr, you need t' do this before gluin' t' latter in place. Aye aye! Blimey!

8) Attach t' parachute and nose cone t' t' shock cord 9" apart, me bucko, in the usual fashion; as always, avoid t' preformed loop on t' nose cone, me bucko, and drill a new, me bucko, second hole in t' cone base for secure shock cord attachment.

If your Flatblack will be used even once with 24mm Aerotech motors, you MUST substitute 6' o' parachute cord for t' 3/8" underpants elastic, and use only t' nylon parachute options; Aerotech motors use much stronger ejection charges that Estes products, me hearties, shiver me timbers, and will break thin elastic shock cords (See photo o' recovery system)

9) Finishing: Flatblack was spray painted with -- what else -- Testor's Flat Black. Avast, me proud beauty! Mylar letterin' spellin' out "flatblack" was obtained from Office Depot. (see finished rocket and pad photos)

Flight:
T' beauty o' Flatblack is its amazin' versatility -- It has been flown t' date on Estes B4-2, ya bilge rat, matey, C6-5, C11-5, D12-5 and E9-4/6 motors, me bucko, and on AT F21-4 and F21-6 Econojets. Avast, me proud beauty! Begad! What other rocket do you know o' (kit or plans) that flies interchangeably on this range o' motors with no ballast changes needed? Just load it up and fly!

T' prefered motor for Flatblack be t' Estes E9-4, which gives a fast, straight boost t' 1000+ feet even with a bit o' wind blowing. Begad! Avast, me proud beauty! Nay bad for a slow initial thrust, shiver me timbers, 62 gram motor in a 75g rocket -- with nay a bit o' nose weight! T' E9-6 is fine also, ya bilge rat, just gives ejection a touch nose down. Ya scallywag! Blimey!

I admit t' loosin' me first drag race with it, sneakin' an E9-6 into the little Flatblack against a kid's C6 model -- musta been a delayed ignition (see photos). But Flatblack kept goin' and goin' and goin' after t' C6 ejected. Ahoy!

Usin' an 18mm adapter (Vaughn Bros.), arrr, Flatblack has flown on as small as an Estes B4-2, givin' a slow but straight clim b t' about 175' with perfect ejection. Begad!

Out in t' desert, Flatblack was flown on AT F21-4 and F21-6 motors -- screamin' climbs out o' sight (my sight, shiver me timbers, anyway) t' at least t' 1350' and 380 mph predicted by sims. Begad! I love that huge F21 flame!

For smaller fields, Flatblack files perfectly on C11-5 and D12-5 24mm Estes motors, shiver me timbers, arrr, ejectin' perfectly and in good agreement with t' 375' and 625' boosts predicted by sims.

Incidently, arrr, ya bilge rat, a drag coefficient o' 1.7 was used for t' simulation software, based on an identical value obtained usin' altimeters with Flatblack's similar big brother, Fahrenheit 62/5. Avast! Ahoy! Blimey!

I haven't tried any o' t' 24mm, AT reloadable motors yet, but based on their weight o' 60 grams, me hearties, me hearties, shiver me timbers, good choices should be: E18-4/7, shiver me timbers, me bucko, ya bilge rat, F24-4/7 and especially t' F12-5, accordin' t' sims. Ya scallywag! Avast!

After more than a dozen test flights, Flatblack shows nay a bit o' damage (see landin' photo). Arrr! This little guy is a lot o' fun, and you can fly it on anything.

Summary:
PROs: Novel looks, good performance and low-cost construction. Easy t' scratch build, even for beginners. Ya scallywag! Durable, fins don't break off. Avast, me proud beauty! Ahoy! Good stability and wind resistance. Begad! Amazin' range o' motors possible, shiver me timbers, B-C-D-E-F with no balance worries. Doesn't go so high on F-power that loss is likely.

CONs: T' price o' all t' PROs be t' twice t' drag o' a "normal" rocket, shiver me timbers, although Cd=1.7 is still pretty darn good for a tubefin. Ya scallywag!