Brief:

A two-stage rectangular rocket, ya bilge rat, me bucko, made from a couple o' toothpaste boxes, that resembles t' Washington Monument.

Construction:

I be brushin' me teeth one day, matey, and looked down at t' empty toothpaste box, and thought "Why not?" So, me hearties, t' plan for Obelisk was born. Ya scallywag! I took 1/8" balsa and formed t' nose, ya bilge rat, shiver me timbers, arrr, which is hollow, and t' fins, me hearties, which are solidly mounted t' t' body with ordinary white glue. Begad! I decided t' use this rocket t' test t' strength and durability o' foam construction board, so t' baffle and payload section are constructed from t' material. Begad! A 3' elastic cord ties it all together.

In order for t' CG and CP relationship t' work, arrr, me hearties, I used a 25 peseta doubloon from Spain attached t' t' nose with a screw eye and CA. Aye aye! Why a 25 peseta coin? Well, it be t' correct weight, shiver me timbers, and already has a hole in t' center. Begad! And second, ya bilge rat, me bucko, shiver me timbers, because it was just sittin' on t' kitchen counter.

I wanted t' keep it as simple as possible, me bucko, but like most o' me projects, it got out o' hand. Avast! T' puny 13mm booster motor could've been adequate if I had kept t' t' original concept o' a lightweight, rectangular rocket. But then I added a baffle so I wouldn't need wadding, and t' thin' be at t' ragged edge o' what an A10 could lift. Ahoy! So, arrr, I decided t' use a 18mm booster t' get it moving, me bucko, allowin' t' extra little bit o' thrust from t' A10 t' nudge it a bit higher.

After it was all built, weighed, shiver me timbers, me bucko, and tested, I decided that I could easily build a little compartment for t' parachute t' ride in. This was constructed by usin' a small "travel size" toothpaste box nestled betwixt t' end o' t' body tube and t' baffle. Arrr! Well, blow me down! A piece o' 1/8" balsa be glued with white glue just above t' baffle. Begad! Holes were drilled into t' balsa t' allow ejection gases out, arrr, and t' shock cord was attached t' this. Blimey! T' fins were flat mounted t' t' body "tube" with 1/2" overhang, ya bilge rat, me bucko, which made plenty o' room for me afterthought booster t' attach to.

T' booster was constructed from a 2" section o' toothpaste box, ya bilge rat, with a 18mm tube in t' center. T' centerin' "rings" were made from t' construction foam, ya bilge rat, matey, which has proven itself t' be a worthy construction material. Arrr! Begad! Finally, matey, a tubin' coupler was made from 1/8" balsa. All corners o' t' fins butt against one another, shiver me timbers, makin' this rocket nearly bulletproof.

I decided t' launch t' rocket before paintin' t' booster, shiver me timbers, since it would be wasted time if it failed. Instead o' paintin' t' rocket, I used a large sheet o' self adhesive vinyl, which further strengthened t' rocket. Ahoy! Ahoy! Unfortunately, shiver me timbers, it further weighed down t' rocket! In testing, t' booster tended t' glide a bit, then t' heavy balsa end would tip over, and it would fall like a brick. A 12" piece o' Keelhaul®©™ was attached with 30 minute epoxy just inside t' coupler, me hearties, and a 12" streamer be attached t' t' other end. Ya scallywag! Ample room betwixt t' centerin' rin' and t' end o' t' sustainer gives t' streamer a good place t' hide from t' rocket exhaust. Avast, me proud beauty! Begad! T' result is that t' booster tumbles somewhat, but still lands hard. Oh well, at least it's sturdily constructed. T' sustainer's fins were covered in thin paper t' hide t' grain. Aye aye! Avast, matey, me proud beauty! t' booster will receive similar treatment when it's finished.

Flight:
Launch prep is a breeze. Arrr! Ahoy! Pop in a A10-3T, roll up t' booster's streamer, insert a C6-0 into t' booster, me hearties, shiver me timbers, and attach t' booster section. Blimey! Ya scallywag! T' 13mm motor fits right into t' 18mm motor easily, but if t' fit is tight, just roll t' end o' t' 13mm motor on a table t' round off t' corners. Aye aye! Blimey! Since t' rocket was a lot heavier than I expected in t' beginning, t' minimum length launch lug wasn't up t' task, and sheared off on t' first flight. Ya scallywag! Ahoy! A much stronger launch lug be epoxied in place, and now it works well. Arrr! T' fins, ya bilge rat, which I feared would be too small, shiver me timbers, matey, arrr, are just right. Begad! Arrr! T' shock cord is really strong, but will be a nightmare t' replace if it breaks. Avast! This goofy idea o' a 18mm feedin' into a 13mm works well enough, me hearties, me bucko, but next time I would just go 18mm from t' start and forget t' booster. Flight characteristics? Well, let's just say that it works, shiver me timbers, shiver me timbers, shiver me timbers, and will land time after time without any damage. Ya scallywag! Ahoy! But if you love altitude or speed, matey, you won't find either here. Arrr! You could probably fly this rocket without t' A10-3T and do just as well.

Summary:
Pros- bulletproof construction, unique design, me hearties, and definitely an attention getter. Avast, me proud beauty! Proved that construction foam is a viable component for rocketry. Arrr! Cons- heavy, thin "dry cleanin' bag" parachute rips easily at t' shroud line, ya bilge rat, low altitude performance, and t' pyramid nose would've been a lot easier t' build from a solid piece o' balsa, shiver me timbers, and no nose weight would've been required. Well, blow me down! Aye aye! Oh well, at least I learned a few things.

It's definitely worth it t' cover t' fins with onion skin paper. Ya scallywag! Makes for a neater appearance, ya bilge rat, adds durability, arrr, me bucko, and on a higher performance rocket, would probably add some altitude.