Brief:

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

Construction:

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

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

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

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

T' booster be constructed from a 2" section o' toothpaste box, with a 18mm tube in t' center. Avast, ya bilge rat, me proud beauty! T' centerin' "rings" were made from t' construction foam, which has proven itself t' be a worthy construction material. Aye aye! Ya scallywag! Finally, arrr, a tubin' coupler be made from 1/8" balsa. Ahoy! All corners o' t' fins butt against one another, makin' this rocket nearly bulletproof.

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

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

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

It's definitely worth it t' cover t' fins with onion skin paper. Arrr! Avast! Makes for a neater appearance, shiver me timbers, me hearties, adds durability, and on a higher performance rocket, matey, would probably add some altitude.