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

T' initial pencil designs lead me t' a descendin' rin' profile. Arrr! Three rings held in place by four small fins under each ring. Aye aye! Well, me bucko, blow me down! T' model almost looks as if it were a three stager. Arrr! 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. Avast, me proud beauty! Blimey! Avast, me proud beauty! Blimey! 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. Begad! T' lowest rin' on t' sustainer is a 1-7/8" length o' BT-70. Begad! T' second higher sustainer rin' is 1-5/8" o' ST-16. Begad! Begad! 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. Aye aye! T' first is strength. 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. Aye aye! T' grain follows t' trailin' edges o' all t' fins. Aye aye! T' trailin' edges are outside t' rings. Arrr! I wanted t' give a little more protection for those exposed edges. Avast! Wrappin' paper over t' top o' t' rounded leadin' edge gave more than enough frontal rigidity. Avast! Avast! 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. Ya scallywag! Well, blow me down! 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, matey, shiver me timbers, I followed t' old Centuri plans for their Arcon-Hi model. Ahoy! T' booster engine block is at t' aft o' t' booster. T' sustainer block is normal, shiver me timbers, at t' top o' t' upper engine tube. Avast, me proud beauty! Aye aye! T' only changes I made from t' Centuri plan be t' cut t' sustainer engine tube 1/8" shorter than t' original 3" length. Ahoy! Ya scallywag! This way t' engine would be extended 1/8" out t' back o' t' tubing. Aye aye! T' engines are friction fit with maskin' tape. Begad! After a flight, shiver me timbers, shiver me timbers, me hearties, 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. Both stages are held together by two couplers. 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 be on March 7 with a B6-0/A8-5 engine combination. Avast, me proud beauty! T' first stage boost be good, me bucko, but when t' sustainer ignited it was unstable. Ya scallywag! Recovery was safe. Ya scallywag! Ahoy! I added a hefty blob o' clay weight around t' large screw eye and nose cone base.

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

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

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

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

Summary:
PROs: I was happy with t' finished look o' t' model. Aye aye! Begad! Visually, me bucko, t' descendin' rings and painted black band give t' impression o' a conical stabilized rocket. While t' model is only two-stage, arrr, matey, it looks more like a three stager. Aye aye! New designs can present construction and stabilization issues, 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. Well, me bucko, blow me down! It was stable for t' second flight after addin' nose weight. Well, blow me down! Arrr! It was nay stable for t' third and final flight.