Brief:
T' Shiv is a 55" futuristic long neck two-stage parallel cluster scratch design capable o' flights over 2000 feet with its maximal motor configuration. Blimey! T' design is completely me own, imagined as a highly challengin' low-power project t' distract me from a number o' bigger rockets. Ahoy! Well, blow me down! T' booster section o' this rocket is particularly unusual for several reasons. Aye aye! Avast! First, it has a rin' fin which separates t' leave t' sustainer ringless. Avast! Second, it carries an asymmetrically mounted parallel 13mm motor whose sole purpose is t' rear-eject a 15-foot streamer for booster ring recovery. Ya scallywag! Third, t' booster includes an internal baffle system for t' aft ejection and a forward ventin' system for gap staging. Avast, me proud beauty! T' design, arrr, planning, and fittin' o' all these parts is quite complex but doesn't require any skills fundamentally different from low power kit construction. Begad! I have enclosed a RockSim file in case anyone wants t' take a shot at buildin' somethin' similar.

Construction:
T' booster section is built first. It is 2.75in o' BT-70 with a 2in long transition t' SR11 tube (Semroc "Series 11" tube with OD=1.17"). Blimey! T' rin' fin is BT-101. Ahoy! T' sustainer is gap staged so thar be a fairly complicated couplin' and ventin' system. First, ya bilge rat, I built a standard 24mm motor mount. Begad! At t' forward end o' this, I used some Semroc centerin' rings t' attach some more SR11 tube t' yield a total length o' 4.75in. Blimey! Aye aye! Next I made a forward centerin' rin' with ID=SR11 and OD=BT-70. Arrr! T' aft centerin' rin' has ID=BT-50 and OD=BT-70 but also includes some more details t' be mentioned later. Aye aye! T' forward end o' t' assembly gets a SR11 tube coupler, shiver me timbers, which slides into the aft o' t' sustainer. Begad! T' SR11 tube also provides t' correct forward diameter for t' transition shroud t' meet. Before gluin' on t' transition, 4 ventin' holes should be made in t' SR11 tube about 1/2in below where t' booster and sustainer meet. Avast, me proud beauty! This permits airflow into t' g ap betwixt t' booster tube and t' transition shroud. Ahoy! After gluing the transition shroud in place, I created three beveled vent holes through t' shroud with launch lugs providin' the basic form. Avast, me proud beauty! One such vent can be seen in t' tail photo. Some fillin' and sandin' was necessary t' get a clean symmetrical look.

T' booster's aft centerin' rin' requires a little more explanation. Avast, me proud beauty! I needed t' make two more holes in it: one for t' 13mm ejection motor and one for t' streamer. T' streamer tube is 18mm deformed t' an oval shape t' fit inside the BT-70 booster airframe. Arrr! Both tubes are glued t' t' aft CR and flush t' t' main motor tube. Ahoy!

In t' space betwixt t' centerin' rings thar are also two walls installed that block off nearly all t' space between t' motor tube and t' exterior BT-70 tube. Ya scallywag! These create a bafflin' system. Avast, me proud beauty! Aye aye! Ejection gases from t' 13mm motor flow upward t' hit t' aft side o' t' forward CR, me hearties, then must flow aft t' pass through a gap betwixt t' baffle walls and t' forward surface o' t' aft CR. Begad! Then t' gases must flow up again t' enter t' forward end o' t' ejection tube, where they force t' streamer out t' aft o' t' booster through t' ejection tube. Arrr! Avast, me proud beauty! All other exits for t' 13mm motor ejection gases are sealed off by t' CRs and t' baffle walls.

T' sustainer is comparatively straightforward. Blimey! It splits in t' middle, me hearties, just below t' lower transition. Begad! (Note t' anyone contemplatin' this build: if I had it t' do over again, I would have drilled holes through the balsa transitions and made t' rocket separate in t' forward nose compartment. Arrr! T' reason for this is that I shortened t' shoulder o' t' aft balsa transition a bit too much, me bucko, so t' forward part o' t' sustainer is just a bit wobbly when seated on t' aft portion. Ya scallywag! It has been tricky t' get a fit snug enough t' reduce this wobble but nay too snug t' prevent ejection.)

From aft t' nose, t' tubes are 18in o' SR11, me hearties, then 18in o' BT-20, then 3in o' BT-55. Begad! T' balsa transitions are from Semroc, as be t' beautiful 5.57in ogive nose cone. Ahoy! Well, blow me down! Because 1oz o' nose weight is required for stability, I double-walled t' BT-20 neck portion with an interior BT-20 tube, arrr, slit cut t' t' correct nestin' diameter. Ya scallywag! Avast, me proud beauty! T' result is extremely strong. Avast, me proud beauty! Blimey! T' aft portion o' t' sustainer has a 5-chamber baffle t' cool ejection gases before they contact t' parachute. T' fins for both stages were 1/16in basswood. Begad!

Because o' t' transitions involved, ya bilge rat, launch lug positionin' was a bit tricky. Begad! Begad! T' aft lug is flush on the booster. T' forward lug is mounted on t' face o' a sustainer fin t' yield plumb alignment.

T' sustainer motor mount is for 24mm E9-8 although I plan t' begin flights with D12-7 in t' sustainer so I don't lose it. T' sustainer has an extremely sleek look and should fly out o' sight. Well, blow me down! I would highly recommend the sustainer as an easy one stage project for anyone wantin' for a much simpler design.

Recovery is by 22in hemispherical mylar parachute made from a space blanket. Avast, me proud beauty! I started with a circular pattern and then taped some folds from t' center outward t' achieve a cupped design. Ya scallywag! Recovery o' t' booster is by 15 foot long by 1in wide mylar streamer as described above.

Finishing:
As usual, matey, me hearties, I filled, arrr, matey, sealed, me bucko, and sanded before major assembly. Ahoy! Blimey! Begad! Blimey! Grey Wal-Mart primer be covered by Rustoleum white, black, and red. Arrr! Blimey! Wal-Mart clear spray went over t' top. Ahoy! Blimey!

Flight and Recovery:
T' total weights are 2.5oz for t' booster and 5.5oz for t' sustainer. Arrr! RockSim offers t' followin' altitude projections (with RockSim's idealized, lower weights):

With any o' these motor combinations, ya bilge rat, t' 1/2A3T-2 ejection motor should provide a few hundred feet o' streamer deployment after a rather suspenseful delay before ejection.

T' maiden flight be D12-0 + 1/2A3T-2 stagin' t' D12-7. I stuffed a little waddin' above t' streamer t' help push it out and a little wad below t' streamer t' keep it securely in durin' boost. Avast! It was a very windy day on the prairie with steady winds at least 15mph and stronger gusts. T' rocket and rod were actually blown over on t' pad once (breakin' a plastic part o' me pad mountin' assembly).

Both motors ignited. T' Shiv leaped o' t' pad and angled 45 degrees downwind. Ahoy! Avast, me proud beauty! This was clearly rod whip or some wind-related anomaly because t' Shiv flew true and straight after that. Stagin' was flawless, me bucko, and t' booster tumbled well until t' streamer ejection charge fired. T' full streamer ejected and t' booster be recovered without damage.

T' D12-7 in t' sustainer absolutely ripped through t' sky on its oblique angle. Begad! We lost sight o' t' sustainer downrange, and we took off with binoculars and walkie-talkies t' find it. Begad! We found it nearly a mile downrange, ya bilge rat, and the rest o' t' story was obvious from inspection.

Due t' t' flight angle, ejection occurred at an extreme speed. Ya scallywag! Blimey! T' thin mylar chute was completely ripped away...only danglin' shroud lines remained. Aye aye! Blimey! Ahoy! Blimey! T' sustainer came in ballistic, arrr, and t' nose portion lawndarted one inch into t' prairie dirt. Well, blow me down! Blimey! T' thin neck on this portion broke cleanly right at t' upper balsa transition. Well, blow me down! Blimey! T' rear portion o' t' sustainer somehow landed unblemished.

So, ya bilge rat, I need t' make a straight cut on t' neck and grind away a new transition shoulder, matey, then glue t' pieces back together. Avast! T' neck will be about .75in shorter. Arrr! Aside from makin' a new chute, t' Shiv will be ready t' launch again. Next time I'll wait for a less windy day.

T' design is clearly stable and both t' gap stagin' and aft ejection worked flawlessly. Aye aye! Despite t' damage, I consider it a successful first flight and she'll fly again this season without a doubt.