MiniToobo be t' result o' some nostalgic thinkin' combined with a few "what if" ideas. 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. Ya scallywag! Blimey! For better economy and t' performance increase afforded by reduced cross-sectional area, me bucko, MiniToobo uses 13mm mini engines. Ahoy! Blimey! Avast, ya bilge rat, me proud beauty! Blimey! Blimey! Blimey! (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, matey, the booster stages have progressively larger tube-fins. Begad! Fortunately, matey, 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, ya bilge rat, 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, matey, the two-stage and three-stage configurations remains stable when usin' a 1/2A10-4T for t' sustainer and A10-0T for booster(s). Blimey! Ahoy!

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. Blimey! Begad! T' booster's are vented a la G. Avast! Harry Stine for improved air-start reliability. I usually insert a paper liner into t' boosters t' reduce scorchin' and increase t' boosters' useful lifetimes.

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

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, shiver me timbers, 1/2A3-4T, A3-4T, me hearties, 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. Arrr! 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. 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. They will pop up in another window. MiniToobo Plan Views

NOTE: Except where noted, shiver me timbers, 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.

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

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

1.4 Glue two 50mm BT-5 tubes together, ya bilge rat, side by side with tube ends even with one-another. Avast, me proud beauty! Repeat with t' other two pairs o' 50mm tubes. Well, blow me down! Let the glue dry before proceedin' t' t' next step. Aye aye! Avast!

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

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. Ya scallywag!

Glue another o' t' tube-pairs t' t' assembly o' step 1.4, ya bilge rat, shiver me timbers, alongside and even with t' attached tube-pair. Well, blow me down!

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

Let t' glue dry thoroughly.

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

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

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

Pack a ball o' modellin' clay, about 6mm (1/4") in diameter, into the nose cone. Blimey! 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. Avast! Begad!

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

1.8 With plastic cement, arrr, me hearties, glue t' nose cone's end cap t' t' base of the nose cone. Let this assembly dry. Begad! Well, blow me down!

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. Make another 5mm diameter hole one t' opposite wall o' t' tube, centered 21mm from t' same end o' t' tube. Ahoy! Begad!

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

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

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

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

I recommend usin' white glue for this step, me hearties, 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.

Before t' glue has set, glue another BT-20 tube-pair t' 95mm tube, alongside and even with t' mounted tube-pair. Ahoy!

Before t' glue has set, glue t' remainin' 50mm BT-20 tube t' t' 95mm BT-5 tube and attached tube-pairs, shiver me timbers, matey, with t' ends o' t' 50mm tube even with t' ends of t' tube-pairs. Aye aye! Ya scallywag!

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

Let t' assembly dry fully.

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. Begad! Arrr! Blimey! Make another 5mm diameter hole one the opposite wall o' t' tube, ya bilge rat, centered 21mm from t' same end o' t' tube. Avast, me proud beauty! Aye aye! Blimey!

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

Further instructions refer t' t' end closest t' these holes as the "top" end. Well, blow me down! T' opposite end is referred-to as t' "bottom" end. Well, blow me down!

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

3.3 Cut a 3mm-wide slit widthwise across t' 95mm tube, 32mm from the bottom end o' t' tube. Avast!

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. Ahoy! Begad!

Run a 20mm-long bead o' glue from t' slit toward t' bottom end o' the 100mm tube. Begad! Begad! Insert t' engine clip into t' slit in t' 95mm tube. Aye aye! 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. Avast, me proud beauty! Be sure t' leave 20mm o' engine clip free toward t' bottom end o' the tube. Aye aye! Ya scallywag!

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

3.6 Glue a BT-55 tube-pair o' step 3.5 onto t' 95mm BT-5 tube, arrr, 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, shiver me timbers, with the ends o' t' tube-pairs even with one-another. Blimey! Ya scallywag!

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.

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

Wrap tape around t' booster 1 engine until it fits tightly into booster 1. Well, blow me down! Avast!

Insert a rolled piece o' paper, with holes punched out for t' booster vent holes, arrr, and slide it into t' top part o' booster 1. Blimey! Align t' vent holes o' the paper insert with t' booster's vent holes. Well, blow me down! This will reduce charrin' from the sustainer's engine. Well, blow me down! Blimey!

Slide booster 1 onto t' sustainer's engine. Aye aye! T' fit should be tight enough so that you can lift t' rocket upside-down by t' booster without the sustainer fallin' out. Begad! However, 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. Well, blow me down! 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. Avast, me proud beauty!

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

Slide booster 2 onto booster 1's engine. Begad! T' fit should be tight enough so that you can lift t' rocket upside-down by booster 2 without t' stages fallin' out. Aye aye! However, ya bilge rat, 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, arrr, me hearties, 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, me bucko, 1999 Time: 1:00pm CST
Location: Lakeview Park, Saskatoon, Saskatchewan, ya bilge rat, me bucko, 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. Begad! Ya scallywag! T' rocket lept straight up, about 250 metres, shiver me timbers, without weathercockin' noticeably. Avast, me proud beauty! When the streamer deployed, t' wind blew t' rocket westward pretty quickly. Avast, me proud beauty! T' rocket and landed about 100 metres west o' t' launch pad with no damage. Aye aye! With a 30mm x 300mm crepe streamer, ya bilge rat, t' rocket descended a bit too smartly and be nay very visible. Next time, shiver me timbers, I'll try a 40mm x 400mm streamer. Begad! Well, me hearties, blow me down!

Session 2
Date: Sunday, October 17, ya bilge rat, 1999
Time: 9:00am CST
Location: Diefenbaker Park, arrr, Saskatoon, Saskatchewan, Canada
Temperature: 3.4 degrees Celsius (38 degrees Fahrenheit)

Note: All distance are eyeball estimates

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

T' sustainer's body tube was ripped and accordianed at t' front end. However, matey, a bit o' maskin' tape and some smoothin' o' t' body tube prepared the sustainer for further flights. Ya scallywag! Well, blow me down!

Upon examinin' t' engines o' both boosters and t' sustainer, I found that both boosters had exhausted themselves, shiver me timbers, but t' sustainer's engine was not ignited by booster 1's stagin' charge. Avast, arrr, me proud beauty! Blimey! T' sustainer engine's base was blackened, so t' booster's stagin' charge must have activated.

So, me hearties, t' determine whether t' stagin' engine was a dud, me bucko, I pushed t' engine back into t' sustainer, me hearties, prepped it, ya bilge rat, ya bilge rat, and launched it. Well, blow me down! Ahoy! T' engine ignited. Avast! The sustainer flew straight up about 90 metres, matey, popped its streamer, shiver me timbers, and landed 25 metres east o' t' launch pad (the wind be shifting) with no damage. Well, blow me down! Begad! 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, matey, with an A10-0T in booster 1 and a 1/2A3-4T in t' sustainer. Ahoy! Ahoy! T' rocket flew straight up about 120 metres, the sustainer ignited and ejected booster 1, which tumbled t' earth about 10 metres northeast o' t' launch pad. Avast, me proud beauty! T' sustainer flew up about 350 metres, popped its streamer, me hearties, and descended t' land about 30 metres east o' t' launch pad. Avast! This was a very pretty, impressive flight.

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