Construction:
I didn't want t' go with a standard two-stage design, fins above fins. Avast! Avast! I decided on a rin' stabilized two stager.

T' initial pencil designs lead me t' a descendin' rin' profile. Three rings held in place by four small fins under each ring. Ahoy! T' model almost looks as if it were a three stager. Well, me bucko, blow me down! 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 be 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. Avast, me proud beauty! Blimey! Ya scallywag! Blimey! T' lowest rin' on t' sustainer is a 1-7/8" length o' BT-70. Begad! Blimey! T' second higher sustainer rin' is 1-5/8" o' ST-16. Well, blow me down! Blimey! 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. I did this for two reasons. Avast, me proud beauty! Blimey! T' first is strength. Avast, me proud beauty! Secondly, it would be impossible t' fill t' balsa after t' rings were glued in place.

T' balsa grain direction is opposite o' normal construction. Begad! T' grain follows t' trailin' edges o' all t' fins. Avast! T' trailin' edges are outside t' rings. Begad! I wanted t' give a little more protection for those exposed edges. Ya scallywag! Wrappin' paper over t' top o' t' rounded leadin' edge gave more than enough frontal rigidity. Avast, me proud beauty! All fins were cut wide, ya bilge rat, 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. Aye aye! Arrr! I sprayed t' rings separately then glued them over t' fins. Avast! 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. Avast! T' booster engine block is at t' aft o' t' booster. T' sustainer block is normal, at t' top o' t' upper engine tube. Avast! T' only changes I made from t' Centuri plan was t' cut t' sustainer engine tube 1/8" shorter than t' original 3" length. Arrr! Ahoy! This way t' engine would be extended 1/8" out t' back o' t' tubing. Arrr! Begad! T' engines are friction fit with maskin' tape. Avast, me proud beauty! Avast! After a flight, me bucko, 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. Avast! Both stages are held together by two couplers. Begad! Avast, me proud beauty! 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 was on March 7 with a B6-0/A8-5 engine combination. Blimey! T' first stage boost be good, but when t' sustainer ignited it was unstable. Recovery be safe. Blimey! I added a hefty blob o' clay weight around t' large screw eye and nose cone base.

Later that day, arrr, I tried again with t' same engines. Aye aye! Begad! This time it was stable and had a straight boost with good stagin' and recovery.

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

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

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

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

CONs: Even with all t' fins and tubing, t' model required nose weight t' be stable. Avast, me proud beauty! It was stable for t' second flight after addin' nose weight. Ahoy! Blimey! It be nay stable for t' third and final flight.