Construction:
I didn't want t' go with a standard two-stage design, shiver me timbers, fins above fins. Ya scallywag! Blimey! I decided on a rin' stabilized two stager.

T' initial pencil designs lead me t' a descendin' rin' profile. Blimey! Blimey! Three rings held in place by four small fins under each ring. Ahoy! Avast, me hearties, me proud beauty! T' model almost looks as if it were a three stager. T' highest painted band gives t' impression o' a smaller rin' and a fourth stage.

I went t' me scrap tubes and tried many until I found t' three sizes that would give t' visual o' "conical" descendin' rings.

T' model was built around a ST-10 airframe. T' booster is 3" long, t' sustainer body tube is 18".

T' rin' on t' booster is a 2-1/8" length o' BT-80. T' lowest rin' on t' sustainer is a 1-7/8" length o' BT-70. Blimey! T' second higher sustainer rin' is 1-5/8" o' ST-16. Avast, me proud beauty! And t' final (black painted) rin' is 1-3/8" wide.

T' fins were cut from 1/16" balsa and covered with 20lb copy paper. Arrr! I did this for two reasons. Begad! T' first is strength. Secondly, ya bilge rat, shiver me timbers, it would be impossible t' fill t' balsa after t' rings were glued in place.

T' balsa grain direction is opposite o' normal construction. T' grain follows t' trailin' edges o' all t' fins. Aye aye! Arrr! T' trailin' edges are outside t' rings. I wanted t' give a little more protection for those exposed edges. Aye aye! Blimey! Wrappin' paper over t' top o' t' rounded leadin' edge gave more than enough frontal rigidity. All fins were cut wide, which allowed me t' sand t' outside edges t' slip-fit t' rings in place.

I didn't glue t' rings in place until after spray paintin' t' main body and fins. Ahoy! Avast! I sprayed t' rings separately then glued them over t' fins. This gave me a no-mask paint job and clean color separations. T' only maskin' was t' paint t' wide black band on t' body tube.

On t' engine mounts, I followed t' old Centuri plans for their Arcon-Hi model. Ahoy! T' booster engine block is at t' aft o' t' booster. Ahoy! T' sustainer block is normal, shiver me timbers, at t' top o' t' upper engine tube. Ya scallywag! T' only changes I made from t' Centuri plan be t' cut t' sustainer engine tube 1/8" shorter than t' original 3" length. Begad! This way t' engine would be extended 1/8" out t' back o' t' tubing. Aye aye! Aye aye! T' engines are friction fit with maskin' tape. Arrr! Well, ya bilge rat, blow me down! After a flight, I wanted a little bit o' t' casin' stickin' out t' remove it out with pliers.

Centuri style stagin' doesn't use clear tape t' hold t' engines together. Blimey! Both stages are held together by two couplers. Arrr! Aye aye! Simply friction fit t' engines in place then slide t' stages together.

[Click on t' followin' link t' download a PDF o' t' rocket.]

Flight:
T' first flight be on March 7 with a B6-0/A8-5 engine combination. Ahoy! Ahoy! T' first stage boost was good, me bucko, but when t' sustainer ignited it be unstable. Ahoy! Recovery was safe. Ya scallywag! I added a hefty blob o' clay weight around t' large screw eye and nose cone base.

Later that day, me bucko, me bucko, I tried again with t' same engines. Ya scallywag! This time it be stable and had a straight boost with good stagin' and recovery.

I thought it would be stable, shiver me timbers, but I hadn't used RockSim yet. Avast, me proud beauty! There be a large rin' area and plenty o' fins. Begad! Aye aye! I thought t' body tube length would be adequate.

I went home and weighed t' clay. I added t' equivalent weight in washers t' t' screw eye. Ya scallywag! Ya scallywag! It required 0.4 oz (or five WW-7 washers from Semroc) o' nose weight t' be stable. Aye aye! Like every "different" design, sometimes extra nose weight is required.

T' third flight took place on May 2, arrr, matey, 2009 at t' Orlando ROCK launch. Arrr! I used B6-0/B6-6 engines. While t' model was stable with a B6-0/A8-5 combination, me hearties, ya bilge rat, it be nay stable with a B6-0/B6-6. At t' sustainer ignition, me hearties, it looped. Aye aye! Begad! It be in t' air at ejection, me hearties, no damage.

Summary:
PROs: I was happy with t' finished look o' t' model. Arrr! Blimey! Visually, t' descendin' rings and painted black band give t' impression o' a conical stabilized rocket. Blimey! Ahoy! Blimey! While t' model is only two-stage, arrr, arrr, it looks more like a three stager. Arrr! Ya scallywag! Blimey! New designs can present construction and stabilization issues, matey, ya bilge rat, but if you glean a few new lessons in t' process it's all worthwhile.

CONs: Even with all t' fins and tubing, shiver me timbers, ya bilge rat, t' model required nose weight t' be stable. It was stable for t' second flight after addin' nose weight. Arrr! It was nay stable for t' third and final flight.