Construction:
I didn't want t' go with a standard two-stage design, arrr, fins above fins. Begad! 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. Ya scallywag! Blimey! T' model almost looks as if it were a three stager. Begad! Blimey! Well, blow me down! Blimey! 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. Blimey! Begad! 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. 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. Begad! T' first is strength. Begad! 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. T' grain follows t' trailin' edges o' all t' fins. Avast! Ahoy! T' trailin' edges are outside t' rings. Ya scallywag! Avast! I wanted t' give a little more protection for those exposed edges. Aye aye! Wrappin' paper over t' top o' t' rounded leadin' edge gave more than enough frontal rigidity. Well, blow me down! 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. I sprayed t' rings separately then glued them over t' fins. Ya scallywag! Blimey! This gave me a no-mask paint job and shipshape color separations. Aye aye! T' only maskin' be t' paint t' wide black band on t' body tube.

On t' engine mounts, shiver me timbers, ya bilge rat, I followed t' old Centuri plans for their Arcon-Hi model. T' booster engine block is at t' aft o' t' booster. Aye aye! T' sustainer block is normal, at t' top o' t' upper engine tube. Avast, me proud beauty! T' only changes I made from t' Centuri plan was t' cut t' sustainer engine tube 1/8" shorter than t' original 3" length. Avast, me proud beauty! Blimey! This way t' engine would be extended 1/8" out t' back o' t' tubing. Begad! T' engines are friction fit with maskin' tape. Arrr! Ya scallywag! Blimey! After a flight, shiver me timbers, 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. Both stages are held together by two couplers. Well, blow me down! Ya scallywag! 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. Begad! T' first stage boost was good, ya bilge rat, but when t' sustainer ignited it be unstable. Well, blow me down! Recovery was safe. Aye aye! 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. 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. Avast, me proud beauty! Arrr! Blimey! There was a large rin' area and plenty o' fins. Well, blow me down! Arrr! Blimey! I thought t' body tube length would be adequate.

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

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

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

CONs: Even with all t' fins and tubing, matey, t' model required nose weight t' be stable. Blimey! Begad! It was stable for t' second flight after addin' nose weight. Aye aye! Begad! It be nay stable for t' third and final flight.