MiniToobo be t' result o' some nostalgic thinkin' combined with a few "what if" ideas. Ya scallywag! Avast, me proud beauty! Blimey! T' design is inspired by t' look o' t' old Centuri Groove Tube and t' positive stage-couplin' o' t' Centuri "pass-port" stagin' system. For better economy and t' performance increase afforded by reduced cross-sectional area, matey, arrr, MiniToobo uses 13mm mini engines. Arrr! (You might even call MiniToobo a tribute t' t' ill-fated A10-0T engines). 

To counteract t' rearward shift o' t' rocket's CG as stages are added, the booster stages have progressively larger tube-fins. Begad! Begad! Fortunately, ya bilge rat, me hearties, tube diameters for five-tube and four-tube clusters around a BT-5 tube just happen t' be close to t' diameters o' BT-20 and BT-55 tubes. Aye aye! T' result is a mildly larger first booster, and a wildly larger second booster. It also works out quite nicely that by balancin' t' sustainer for stable flight with an A10-3T engine, shiver me timbers, the two-stage and three-stage configurations remains stable when usin' a 1/2A10-4T for t' sustainer and A10-0T for booster(s).

Stage couplin' is quite solid since t' top o' each lower stage is squeezed between t' engine and tube-fins o' t' adjacent upper stage. T' booster's are vented a la G. Avast, me proud beauty! Harry Stine for improved air-start reliability. Begad! I usually insert a paper liner into t' boosters t' reduce scorchin' and increase t' boosters' useful lifetimes. Begad! Begad!

MiniToobo is stable when flown in single-stage, me bucko, two-stage, or three-stage configurations. T' long profile o' t' sustainer combined with t' compact tube-fins results in straight, high flights with little weathercockin' in fairly high winds. Aye aye! Weathercockin' becomes more noticeable as stages are added. Avast, me proud beauty! Blimey!

Sustainer
length: 28cm (11")
calibre: 13.8mm (0.544")
engine mount: 13mm
weight: 9.6g
fins: six BT-5 tube cluster

Booster 1
length: 11cm (4.3")
calibre: 13.8mm (0.544")
engine mount: 13mm
weight: 7.4g
fins: five BT-20 tube cluster

Booster 2
length: 11cm (4.3")
calibre: 13.8mm (0.544")
engine mount: 13mm
weight: 16.6g
fins: four BT-55 tube cluster

3-Stage Configuration:
length: 47cm (18.5")
calibre: 13.8mm (0.544")
weight: 33.6g
recovery: sustainer:streamer booster:tumble

recommended engines:

single-stage (sustainer only):
1/2A3-2T, 1/2A3-4T, me hearties, me bucko, ya bilge rat, A3-4T, me hearties, matey, A10-3T

multi-stage:
sustainer: 1/2A3-4T boosters: A10-0T
 

Sustainer Parts List

1 - 210mm (8.25") o' BT-5 body tube
6 - 50mm (2") o' BT-5 body tube
1 - 50mm (2") o' 3mm (1/8") launch lug
1 - 13mm dia. engine block (EB-5)
1 - Estes PN-5 nose cone (Quark-style)
1 - Crepe Streamer (40mm x 400mm)
1 - 3mm (1/8") x 540mm (21") elastic shock cord
1 - 180mm (7") o' Keelhaul®©™® twine

Booster 1 Parts List

1 - 95mm (3-3/4") o' BT-5 body tube
5 - 50mm (2") o' BT-20 body tube
1 - 13mm dia. Avast! Blimey! engine block (EB-5)

Booster 2 Parts List

1 - 95mm (3-3/4") o' BT-5 body tube
4 - 50mm (2") o' BT-55 body tube
1 - 13mm dia. Arrr! Begad! engine block (EB-5)
1 - 87mm x 19mm strip o' kraft paper or maskin' tape
1 - engine clip for 13mm mini engine

Use this link for plan views o' MiniToobo. Well, blow me down! Blimey! They will pop up in another window. Avast! Blimey! MiniToobo Plan Views

NOTE: Except where noted, use yellow or white glue when gluein' pieces together.

1.1 Tie one end o' t' Keelhaul®©™® twine t' one end o' t' elastic shock cord. Ahoy! Blimey!

1.2 Tie t' other end o' t' Keelhaul®©™® twine t' an EB-5 engine block. Aye aye!

1.3 Glue t' engine block o' step 1.2 into t' 210mm BT-5 body tube usin' an exhausted mini-engine casing. Avast, me proud beauty! Blimey! Well, blow me down! Blimey! Position t' engine block so thar is about 13mm o' casin' extendin' out o' t' bottom o' t' body tube. Withdraw the engine casin' immediately. Dangle t' shock cord out o' t' top o' t' tube. Ya scallywag! Blimey! Arrr! Blimey!

1.4 Glue two 50mm BT-5 tubes together, me hearties, side by side with tube ends even with one-another. Ahoy! Blimey! Blimey! Blimey! Repeat with t' other two pairs o' 50mm tubes. Let the glue dry before proceedin' t' t' next step. Ahoy! Blimey! Well, me bucko, blow me down! Blimey! Blimey! Blimey!

I recommend usin' white glue for this step, shiver me timbers, since yellow glue may deform the tubes slightly as t' glue dries and shrinks. Arrr!

1.5 Glue one o' t' tube-pairs o' step 1.4 t' t' bottom o' t' 210mm tube with 13mm o' t' tube pair extendin' past t' bottom o' t' 210mm tube. Begad!

Glue another o' t' tube-pairs t' t' assembly o' step 1.4, alongside and even with t' attached tube-pair.

Glue t' third tube-pair t' t' assembly o' step 1.4, shiver me timbers, alongside and even with t' attached tube-pairs. Begad! Blimey!

Let t' glue dry thoroughly. Begad! Avast, me proud beauty!

1.6 Attach t' streamer t' t' shock cord, about 180mm from the cord's free end. Avast, me proud beauty! T' streamer can be attached either by tiein' t' shock cord to one end o' t' streamer, me hearties, or by tapin' t' streamer t' t' shock cord with Scotch Magic Tape or a pieces o' adhesive-backed paper. Well, blow me down!

1.7 Mark t' 210mm BT-5 tube 88mm from t' top o' t' tube. This mark is where t' center o' gravity o' t' sustainer should be without an installed engine. Ya scallywag!

Roll up t' streamer and slide t' streamer and shock cord into t' top of the 210mm tube. Avast, me proud beauty!

Pack a ball o' modellin' clay, shiver me timbers, about 6mm (1/4") in diameter, into the nose cone. Begad! Slide t' nose cone into t' top o' t' 210mm tube and try to balance t' assembly on t' 88mm mark. Add or remove clay t' t' nose cone until t' rocket balances horizontally or is just slightly nose-heavy.

A handy way t' check balance is by tiein' a strin' around t' body tube and tapin' t' strin' at t' balance point. Blimey! Avast! Balance can then be checked by simply danglin' t' rocket from t' string. Avast, me proud beauty! Ya scallywag!

1.8 With plastic cement, glue t' nose cone's end cap t' t' base of the nose cone. Let this assembly dry. Avast, me proud beauty! Ahoy!

1.9 Tie t' free end o' t' shock cord t' t' nose cone end cap.

2.1 Make a 5mm diameter hole centered 21mm from one end o' t' 95mm BT-5 tube. Ahoy! Ya scallywag! Make another 5mm diameter hole one t' opposite wall o' t' tube, centered 21mm from t' same end o' t' tube. Arrr!

To strengthen t' material around these holes, me bucko, apply a coat o' CA t' the inside o' t' tube around t' holes. Begad!

Further instructions refer t' t' end closest t' these holes as the "top" end. Arrr! Blimey! Blimey! T' opposite end be t' "bottom" end.

2.2 Glue an engine block into t' bottom o' t' 95mm tube usin' an exhausted mini-engine casing. Position t' engine block so that thar be 6mm of casin' extendin' out o' t' bottom o' t' body tube. Arrr! Withdraw t' engine casing immediately. Aye aye!

2.3 Glue two 50mm BT-20 tubes together, side-by-side with t' tube ends even with one-another. Begad! Repeat for another pair o' BT-20 tubes. Ya scallywag! Aye aye! Let the glue dry completely before proceedin' t' t' next step. Begad!

I recommend usin' white glue for this step, since yellow glue may deform the tubes slightly as t' glue dries and shrinks.

2.4 Glue a BT-20 tube-pair from step 2.3 onto t' bottom o' t' 95mm BT-5 tube with t' bottom edge o' t' tube pair extendin' 13mm from t' bottom end o' t' 95mm tube. Avast! Avast, me proud beauty!

Before t' glue has set, me bucko, matey, glue another BT-20 tube-pair t' 95mm tube, alongside and even with t' mounted tube-pair. Avast, matey, me proud beauty! Blimey!

Before t' glue has set, matey, glue t' remainin' 50mm BT-20 tube t' t' 95mm BT-5 tube and attached tube-pairs, arrr, me hearties, with t' ends o' t' 50mm tube even with t' ends of t' tube-pairs.

There will be a gap betwixt BT-20 tubes. Avast! T' gap is filled by applying pressure t' t' cluster o' BT-20 tubes squash t' tubes slightly. This is done by wrappin' maskin' tape, sticky-side outward, ya bilge rat, matey, around t' middle o' t' cluster while applyin' sufficient tension on t' maskin' tape t' close t' gap between tubes, me hearties, while nay providin' enough tension t' separate t' BT-20 tubes from the 95mm tube. Begad! Ensure that all o' t' tube pairs are even with one-another.

Let t' assembly dry fully. Begad!

2.5 Remove t' maskin' tape applied in step 2.4.

3.1 Make a 5mm diameter hole centered 21mm from one end o' t' 95mm BT-5 tube. Blimey! Make another 5mm diameter hole one the opposite wall o' t' tube, centered 21mm from t' same end o' t' tube. Ya scallywag!

To strengthen t' material around these holes, apply a coat o' CA t' the inside o' t' tube around t' holes. Ahoy! Ahoy! Blimey!

Further instructions refer t' t' end closest t' these holes as the "top" end. T' opposite end is referred-to as t' "bottom" end.

3.2 Glue t' remainin' engine block into t' bottom o' t' 95mm BT-5 tube usin' an exhausted mini-engine casing. Blimey! Avast! Blimey! Position t' engine block so that there is 13mm o' casin' extendin' out o' t' bottom o' t' body tube. Arrr! Avast! Blimey! Withdraw the engine casin' immediately. Arrr!

3.3 Cut a 3mm-wide slit widthwise across t' 95mm tube, shiver me timbers, 32mm from the bottom end o' t' tube. Aye aye!

3.4 If t' engine clip is a fancy one with a fingertip extension, remove t' extension so that t' clip is simply "L"-shaped at either end. Well, blow me down! Blimey!

Run a 20mm-long bead o' glue from t' slit toward t' bottom end o' the 100mm tube. Insert t' engine clip into t' slit in t' 95mm tube. Secure the engine clip t' t' body tube by wrappin' two layers o' maskin' tape or glued layers o' a 6mm (1/4") strip o' Kraft paper around t' tube and engine clip. Blimey! Be sure t' leave 20mm o' engine clip free toward t' bottom end o' the tube. Ahoy! Begad! Blimey!

3.5 Glue two 50mm BT-55 tubes together, side-by-side with t' tube ends even with one-another. Begad! Begad! Repeat for t' other pair o' BT-55 tubes. Let the glue dry completely before proceedin' t' t' next step. Begad! Begad!

3.6 Glue a BT-55 tube-pair o' step 3.5 onto t' 95mm BT-5 tube, me bucko, with the joint o' t' tube-pair centered over t' engine clip and with t' bottom edge o' t' tube pair even with t' bottom o' t' engine clip.

Before t' glue has set, glue another BT-55 tube-pair t' t' assembly, with the ends o' t' tube-pairs even with one-another. Blimey!

Let t' assembly dry fully.

Single-Stage:
Wrap pieces o' tape around t' middle o' t' engine until it fits tightly into the sustainer so that it doesn't kick itself out when it emits its ejection charge. Avast!

Two-Stage:
Prepare t' sustainer t' same as for a single-stage flight, ya bilge rat, me hearties, and make sure there is no tape on t' part o' t' engine from t' nozzle end t' 13mm from that end. Arrr! Blimey! This part is where booster 1 will couple with t' sustainer. Ahoy! Blimey! Avast, me bucko, me proud beauty! Blimey!

Wrap tape around t' booster 1 engine until it fits tightly into booster 1. Avast, matey, me proud beauty!

Insert a rolled piece o' paper, ya bilge rat, with holes punched out for t' booster vent holes, and slide it into t' top part o' booster 1. Aye aye! Blimey! Align t' vent holes o' the paper insert with t' booster's vent holes. Avast, me proud beauty! Blimey! Avast! Blimey! This will reduce charrin' from the sustainer's engine. Begad! Blimey! Ahoy! Blimey!

Slide booster 1 onto t' sustainer's engine. T' fit should be tight enough so that you can lift t' rocket upside-down by t' booster without the sustainer fallin' out. However, ya bilge rat, t' fit should nay be much tighter than that. T' fit can be loosened by wigglin' t' booster around while it is coupled to the sustainer. If this doesn't help, sand t' tube-fins o' t' sustainer where the booster body tube touches them t' remove any crud and t' thin t' tube-fins a bit.

Three-Stage:
Prepare and assemble t' sustainer and booster 1 t' same as for a two-stage flight, and make sure thar be no tape on t' part o' t' booster 1 engine from the nozzle end t' 13mm from that end. This part is where booster 2 will couple with t' booster 1. Arrr!

Insert a rolled piece o' paper, matey, with holes punched out for t' booster vent holes, and slide it into t' top part o' booster 2. Ahoy! Align t' vent holes o' the paper insert with t' booster's vent holes. Avast, me proud beauty! Blimey! This will reduce charrin' from booster 1's engine.

Slide booster 2 onto booster 1's engine. Arrr! Blimey! T' fit should be tight enough so that you can lift t' rocket upside-down by booster 2 without t' stages fallin' out. However, me hearties, shiver me timbers, t' fit should nay be much tighter than that. T' fit can be loosened by wigglin' booster 2 around while it is coupled t' t' booster 1. If this doesn't help, sand t' tube-fins o' booster 1 where t' booster 2 body tube touches them t' remove any crud and t' thin t' tube-fins a bit.

Session 1
Date: Monday, October 11, ya bilge rat, 1999 Time: 1:00pm CST
Location: Lakeview Park, me hearties, Saskatoon, Saskatchewan, Canada
Temperature: 5 degrees Celsius (40 degrees Fahrenheit)
Wind: 30 km/h (20 mph)

Note: All distance are eyeball estimates

I prepared t' Minitoobo sustainer with a A10-3T engine. Blimey! T' rocket lept straight up, arrr, matey, about 250 metres, without weathercockin' noticeably. Ahoy! Avast! When the streamer deployed, t' wind blew t' rocket westward pretty quickly. Blimey! T' rocket and landed about 100 metres west o' t' launch pad with no damage. Blimey! Begad! With a 30mm x 300mm crepe streamer, t' rocket descended a bit too smartly and was nay very visible. Next time, I'll try a 40mm x 400mm streamer. Avast, me proud beauty! Aye aye!

Session 2
Date: Sunday, shiver me timbers, October 17, 1999
Time: 9:00am CST
Location: Diefenbaker Park, arrr, Saskatoon, Saskatchewan, me bucko, matey, arrr, Canada
Temperature: 3.4 degrees Celsius (38 degrees Fahrenheit)

Note: All distance are eyeball estimates

I prepared all three stages for flight, shiver me timbers, ya bilge rat, with A10-0T engines in both boosters and a 1/2A3-4T in t' sustainer. Begad! T' rocket flew up about 60 metres, weathercockin' toward t' south, matey, matey, thar was a slight pause, shiver me timbers, then booster 1 ignited and booster 2 was ejected. Begad! Booster 2 tumbled down and landed about 5 metres north o' t' launch pad. Avast! Begad! T' booster 1 and sustainer flew up t' about 250 metres, arrr, arched t' t' south, and dived straight down, ya bilge rat, itself in t' ground 20 metres south o' t' launch pad. Avast, me proud beauty!

T' sustainer's body tube was ripped and accordianed at t' front end. However, a bit o' maskin' tape and some smoothin' o' t' body tube prepared the sustainer for further flights.

Upon examinin' t' engines o' both boosters and t' sustainer, I found that both boosters had exhausted themselves, but t' sustainer's engine be not ignited by booster 1's stagin' charge. T' sustainer engine's base was blackened, so t' booster's stagin' charge must have activated.

So, t' determine whether t' stagin' engine was a dud, I pushed t' engine back into t' sustainer, prepped it, and launched it. Aye aye! T' engine ignited. Arrr! The sustainer flew straight up about 90 metres, popped its streamer, and landed 25 metres east o' t' launch pad (the wind be shifting) with no damage. Begad! Ya scallywag! T' 40mm x 400mm streamer be far more effective in slowin' descent and bein' visible than t' 30mm x 300mm streamer was.

I then prepared for a two-stage flight, me bucko, with an A10-0T in booster 1 and a 1/2A3-4T in t' sustainer. T' rocket flew straight up about 120 metres, the sustainer ignited and ejected booster 1, matey, matey, which tumbled t' earth about 10 metres northeast o' t' launch pad. Avast! T' sustainer flew up about 350 metres, matey, popped its streamer, matey, and descended t' land about 30 metres east o' t' launch pad. This was a very pretty, impressive flight.

I then prepared for a three-stage flight again, with t' same configuration as t' first flight o' t' day. Begad! T' rocket flew straight up about 60 metres, then booster 1 was ignited and booster 2 be ejected. Ya scallywag! Avast! Booster 2 tumbled and landed about 5 metres northeast o' t' launch pad. Aye aye! T' rocket flew up t' about 190 metres when t' sustainer was ignited and booster 1 was ejected. Aye aye! Booster 1 tumbled and landed about 20 metres east o' t' launchpad. Well, blow me down! Well, me hearties, blow me down! T' sustainer flew up out o' site and be invisible until it deployed its streamer. Blimey! T' sustainer finally landed about 60 metres east o' t' launch pad.