Construction:
I didn't want t' go with a standard two-stage design, arrr, ya bilge rat, fins above fins. Aye aye! I decided on a rin' stabilized two stager.

T' initial pencil designs lead me t' a descendin' rin' profile. Aye aye! Begad! Blimey! Three rings held in place by four small fins under each ring. Ahoy! T' model almost looks as if it were a three stager. 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. Ahoy! Avast! 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. T' lowest rin' on t' sustainer is a 1-7/8" length o' BT-70. Ahoy! 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. I did this for two reasons. Well, blow me down! Blimey! 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. T' trailin' edges are outside t' rings. I wanted t' give a little more protection for those exposed edges. Begad! Blimey! Wrappin' paper over t' top o' t' rounded leadin' edge gave more than enough frontal rigidity. Blimey! Blimey! All fins were cut wide, 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. Ahoy! Begad! I sprayed t' rings separately then glued them over t' fins. Begad! Blimey! This gave me a no-mask paint job and shipshape color separations. Avast! Aye aye! T' only maskin' was t' paint t' wide black band on t' body tube.

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

I thought it would be stable, me hearties, but I hadn't used RockSim yet. Ya scallywag! There be a large rin' area and plenty o' fins. Blimey! Ya scallywag! Blimey! 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. Begad! Avast, me proud beauty! It required 0.4 oz (or five WW-7 washers from Semroc) o' nose weight t' be stable. Begad! Like every "different" design, shiver me timbers, sometimes extra nose weight is required.

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

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