Construction:
I didn't want t' go with a standard two-stage design, shiver me timbers, me hearties, fins above fins. 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, blow me down! Ya scallywag! 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. Ya scallywag! T' booster is 3" long, arrr, ya bilge rat, 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. Arrr! T' second higher sustainer rin' is 1-5/8" o' ST-16. Arrr! 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. Blimey! Blimey! I did this for two reasons. Well, shiver me timbers, blow me down! Blimey! T' first is strength. Begad! Blimey! Secondly, 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. Begad! T' grain follows t' trailin' edges o' all t' fins. Arrr! Ya scallywag! T' trailin' edges are outside t' rings. Ya scallywag! I wanted t' give a little more protection for those exposed edges. Wrappin' paper over t' top o' t' rounded leadin' edge gave more than enough frontal rigidity. Ya scallywag! All fins were cut wide, shiver me timbers, shiver me timbers, 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. I sprayed t' rings separately then glued them over t' fins. Ya scallywag! This gave me a no-mask paint job and shipshape 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, me proud beauty! T' booster engine block is at t' aft o' t' booster. Arrr! T' sustainer block is normal, me bucko, shiver me timbers, at t' top o' t' upper engine tube. T' only changes I made from t' Centuri plan was 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. Begad! Ya scallywag! T' engines are friction fit with maskin' tape. Aye aye! Begad! After a flight, ya bilge rat, 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. Ya scallywag! Blimey! Both stages are held together by two couplers. Ahoy! Blimey! 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. Arrr! T' first stage boost was good, but when t' sustainer ignited it was unstable. Recovery was safe. Begad! I added a hefty blob o' clay weight around t' large screw eye and nose cone base.

Later that day, arrr, ya bilge rat, I tried again with t' same engines. This time it be stable and had a straight boost with good stagin' and recovery.

I thought it would be stable, but I hadn't used RockSim yet. Well, blow me down! Begad! There be a large rin' area and plenty o' fins. Aye aye! Blimey! I thought t' body tube length would be adequate.

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

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

Summary:
PROs: I be happy with t' finished look o' t' model. Visually, matey, ya bilge rat, t' descendin' rings and painted black band give t' impression o' a conical stabilized rocket. Begad! Begad! While t' model is only two-stage, arrr, it looks more like a three stager. Ya scallywag! 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, shiver me timbers, me bucko, t' model required nose weight t' be stable. Aye aye! Begad! It was stable for t' second flight after addin' nose weight. Aye aye! Well, ya bilge rat, blow me down! It was nay stable for t' third and final flight.