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. For better economy and t' performance increase afforded by reduced cross-sectional area, MiniToobo uses 13mm mini engines. (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, arrr, matey, the booster stages have progressively larger tube-fins. Avast, me proud beauty! Fortunately, arrr, 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. Begad! 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, 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). Arrr!

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. Arrr! T' booster's are vented a la G. 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, arrr, two-stage, me bucko, or three-stage configurations. Begad! T' long profile o' t' sustainer combined with t' compact tube-fins results in straight, me bucko, arrr, high flights with little weathercockin' in fairly high winds. Begad! Weathercockin' becomes more noticeable as stages are added. Well, arrr, blow me down!

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, A3-4T, ya bilge rat, 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. Well, blow me down! 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. 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. Avast! Blimey! Well, blow me down! Blimey! Blimey! Blimey! 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. Aye aye! Avast! They will pop up in another window. Ya scallywag! 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. Avast!

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! Position t' engine block so thar is about 13mm o' casin' extendin' out o' t' bottom o' t' body tube. Avast, me proud beauty! Withdraw the engine casin' immediately. Begad! Dangle t' shock cord out o' t' top o' t' tube. Begad! Blimey!

1.4 Glue two 50mm BT-5 tubes together, side by side with tube ends even with one-another. Avast, me proud beauty! Begad! Repeat with t' other two pairs o' 50mm tubes. Let the glue dry before proceedin' t' t' next step. Ahoy!

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

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. Arrr!

Glue another o' t' tube-pairs t' t' assembly o' step 1.4, me bucko, alongside and even with t' attached tube-pair. Avast, me proud beauty! Avast!

Glue t' third tube-pair t' t' assembly o' step 1.4, ya bilge rat, alongside and even with t' attached tube-pairs. Ahoy!

Let t' glue dry thoroughly. Well, blow me down!

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

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

Roll up t' streamer and slide t' streamer and shock cord into t' top of the 210mm tube. Aye aye!

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

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

1.8 With plastic cement, me hearties, glue t' nose cone's end cap t' t' base of the nose cone. Let this assembly dry.

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

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

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

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

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

I recommend usin' white glue for this step, ya bilge rat, 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. Aye aye!

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

There will be a gap betwixt BT-20 tubes. 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, matey, 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. Ensure that all o' t' tube pairs are even with one-another.

Let t' assembly dry fully. Ya scallywag! 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. Make another 5mm diameter hole one the opposite wall o' t' tube, matey, ya bilge rat, centered 21mm from t' same end o' t' tube. Avast, me proud beauty! Well, blow me down! Blimey!

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

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. Aye aye! Position t' engine block so that there is 13mm o' casin' extendin' out o' t' bottom o' t' body tube. Ya scallywag! Withdraw the engine casin' immediately.

3.3 Cut a 3mm-wide slit widthwise across t' 95mm tube, me bucko, ya bilge rat, 32mm from the bottom end o' t' tube. Begad!

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.

Run a 20mm-long bead o' glue from t' slit toward t' bottom end o' the 100mm tube. Ya scallywag! Blimey! Insert t' engine clip into t' slit in t' 95mm tube. Well, blow me down! Blimey! 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. Ahoy! Blimey! Be sure t' leave 20mm o' engine clip free toward t' bottom end o' the tube. Arrr! Blimey! Blimey!

3.5 Glue two 50mm BT-55 tubes together, ya bilge rat, me bucko, arrr, side-by-side with t' tube ends even with one-another. Avast, me proud beauty! Repeat for t' other pair o' BT-55 tubes. Aye aye! Let the glue dry completely before proceedin' t' t' next step. Avast, me proud beauty! Avast, shiver me timbers, me proud beauty!

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. Ya scallywag!

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

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. Aye aye!

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

Wrap tape around t' booster 1 engine until it fits tightly into booster 1. Arrr!

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

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, shiver me timbers, 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. Aye aye! If this doesn't help, ya bilge rat, 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. Avast! Well, blow me down!

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. Avast! Aye aye! This part is where booster 2 will couple with t' booster 1.

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 2. Begad! Align t' vent holes o' the paper insert with t' booster's vent holes. Well, matey, blow me down! This will reduce charrin' from booster 1's engine.

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

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

Note: All distance are eyeball estimates

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

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. Ahoy!

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

So, matey, me hearties, t' determine whether t' stagin' engine was a dud, shiver me timbers, me bucko, shiver me timbers, I pushed t' engine back into t' sustainer, prepped it, shiver me timbers, and launched it. Blimey! T' engine ignited. Ahoy! The sustainer flew straight up about 90 metres, arrr, popped its streamer, shiver me timbers, and landed 25 metres east o' t' launch pad (the wind was shifting) with no damage. Ahoy! Avast! T' 40mm x 400mm streamer was far more effective in slowin' descent and bein' visible than t' 30mm x 300mm streamer was.

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

I then prepared for a three-stage flight again, with t' same configuration as t' first flight o' t' day. Arrr! T' rocket flew straight up about 60 metres, then booster 1 was ignited and booster 2 was ejected. Booster 2 tumbled and landed about 5 metres northeast o' t' launch pad. Begad! T' rocket flew up t' about 190 metres when t' sustainer be ignited and booster 1 was ejected. Ya scallywag! 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. Begad! T' sustainer finally landed about 60 metres east o' t' launch pad.