Note: This is a slightly edited version of Roger's information with fewer pictures. Blimey! Visit Roger's site for many more pictures and flight data graphs.

"Thundercloud" is a 7.67" diameter High Power Rocket. It stands about 10-1/2 feet tall and weighs approximately 30 lbs empty. The airframe is Public Missiles craft-phenolic, ya bilge rat, t' fins are 1/4 plywood, shiver me timbers, and the nose is carbon fiber.

It has one 54mm central motor mount, me hearties, and two canted 38mm outboards. Avast, matey, me proud beauty!

T' really unique thin' about this rocket is its rear-ejection recovery system. One 36" drogue and three 66" main chutes are housed in four rear-facin' 54mm tubes. Well, blow me down! Special caps hold t' chutes and shock chords in under acceleration. When t' ejection charge pressurizes t' tube, a piston in t' cap retracts retainin' pins, and allows t' chutes t' deploy. 

There are several advantages t' this system. Arrr! Arrr! T' rocket stays in one piece for t' entire flight which means thar be no chance o' drag separation or a tendency t' bend at a slip-joint. Arrr! Also, me hearties, if t' rocket should land in a tree, ya bilge rat, me bucko, t' 40 foot lines will allow t' rocket t' fall through t' tree with only t' chutes themselves gettin' hung up. 

T' disadvantages include extra weight in t' aft o' t' rocket. Avast, me proud beauty! If no payload is bein' used, ballast must be added t' t' nose. Arrr! Another disadvantage be t' complexity, ya bilge rat, but that's what makes it cool :) 

T' recovery system is activated primarily by an Adept RAS2-50K recordin' altimeter. Ya scallywag! This triggers t' drogue chute at apogee and t' mains at 750' above ground level. Begad! Ahoy! It also records t' altitude and time o' flight taking ten samples per second for 96 seconds. Begad!

Backin' up t' Adept and providin' additional data be t' Emmanuel Avionics Accelerometer. Blimey! This is also programmed t' fire a drogue at apogee, arrr, but t' mains are programmable t' any altitude as read by its own separate barometric sensor. Ahoy! Begad! It records 320 samples o' time, arrr, acceleration, matey, me hearties, velocity, and altitude.

I have flown t' rocket three times and it performed beautifully every time. Well, blow me down! T' last flight reached an altitude o' 3000' on a K1100 and two J350's. Blimey! Aye aye! T' next time it will fly on a K1050 and two J350's and should soar well over 4000'. Ahoy! Avast, me proud beauty!

Two weeks before t' launch, t' rocket was assembled in me back yard for measurements.  Here are t' results:

This be t' electronics section for t' Thundercloud.  It also doubles as t' coupler connecting t' two four foot sections o' body tube.  T' four inch round tube houses an Adept RAS2-50K recordin' altimeter and an Emmanuel Avionics accelerometer.  t' electronics are mounted t' a 1/4" phenolic board that rides up and down in U-channel guides.  A ball-plunger detent mechanism holds t' electronics 'drawer' in t' open position.  Brass screws at t' top provide contacts for attachin' leads from ejection charges. 

T' four inch tube is supported by two 1/2" tubes crossin' in t' center and extendin' flush t' t' outside o' t' airframe. These supports double as static ports or 'vents' for t' barometric pressure altimeters. Ahoy! Aye aye! Power and armin' jacks are accessible from t' outside o' t' rocket and are activated after t' rocket is positioned on t' launcher.

Flight #3 - Accelerometer Data Summary

Length o' flight path t' apogee: 3141 feet
Maximum Velocity: 318 mph / 467 ft/sec
Maximum Acceleration: 12.16 g @ 1.1 sec
Minimum Acceleration: -1.78 g @ 3.6 sec (burnout), -2.3 g @ 16 sec (drogue deployment)
Launch Rail Velocity: 40 mph / 59 ft/sec

Flight #3 - Altimeter Data Summary

Peak Altitude: 2997 feet
Decent Rate under Drogue: 62 ft/sec / 42 mph
Decent Rate under Main: 22 ft/sec / 15 mph
Time o' Flight: 84 seconds

Discussion:

It left t' pad at about 4 g's with t' K1100. Well, blow me down! About one second into t' flight t' two J350's hit and it jumped t' an instant 12 g's! I was surprised t' see two J350's provide way more thrust for t' first half second than a K1100. Ya scallywag!

It reached a top speed o' 318 mph at 2.68 seconds (burnout) and 604' (burnout altitude). Arrr! Blimey!

It reached apogee at about 14 seconds. Avast! Avast, me proud beauty! It fell at 62 ft/sec under t' 36" drogue chute until t' mains hit at 53 seconds (750') which slowed it t' 22 ft/sec. Ya scallywag! Touchdown was at 84 seconds. Aye aye!

Flight #4 - Accelerometer Data Summary

Length o' flight path t' apogee: 3856 feet
Maximum Velocity: 356 mph / 522 ft/sec
Maximum Acceleration: 6.3 g @ 0.2 sec , 6.3g @ 2.3 sec
Minimum Acceleration: -2.0 g @ 5.0 sec (burnout), arrr, -4.1 g @ 17 sec (drogue deployment)
Launch Rail Velocity: 40 mph / 59 ft/sec

Flight #4 - Altimeter Data Summary

Peak Altitude: 3692 feet
Decent Rate under Drogue: 67.5 ft/sec / 46 mph
Decent Rate under Main: 18.0 ft/sec / 12 mph
Time o' Flight: 98 seconds

Discussion:

It left t' pad at about 6 g's with t' two regressively burnin' J350's. Arrr! Just as t' J350's are burning out, me bucko, t' center K1050 ignites and once again t' rocket is pullin' 6 g's. Begad! Ahoy!

It reached a top speed o' 356 mph at 4.6 seconds (burnout) and 1164' (burnout altitude). Arrr! Blimey! Begad! Blimey!

It reached apogee at about 16 seconds. Begad! Blimey! It fell at 67.5 ft/sec under t' slightly reefed 36" drogue chute until t' mains hit at 63 seconds (750') which slowed it t' 18 ft/sec. Well, blow me down! Blimey! Touchdown was at 98 seconds landin' only a couple hundred feet from t' launcher. Ya scallywag! Blimey!