Brief:

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

Construction:

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

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

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

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

T' booster was constructed from a 2" section o' toothpaste box, with a 18mm tube in t' center. Well, blow me down! Blimey! Blimey! T' centerin' "rings" were made from t' construction foam, me bucko, which has proven itself t' be a worthy construction material. Arrr! Finally, arrr, a tubin' coupler was made from 1/8" balsa. Avast, me proud beauty! 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, since it would be wasted time if it failed. Ahoy! Instead o' paintin' t' rocket, I used a large sheet o' self adhesive vinyl, which further strengthened t' rocket. Begad! Unfortunately, it further weighed down t' rocket! In testing, t' booster tended t' glide a bit, me hearties, then t' heavy balsa end would tip over, ya bilge rat, and it would fall like a brick. Aye aye! A 12" piece o' Keelhaul®©™ was attached with 30 minute epoxy just inside t' coupler, and a 12" streamer be attached t' t' other end. Arrr! 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. Ahoy! T' result is that t' booster tumbles somewhat, me bucko, but still lands hard. Ya scallywag! Aye aye! Oh well, shiver me timbers, matey, at least it's sturdily constructed. T' sustainer's fins were covered in thin paper t' hide t' grain. t' booster will receive similar treatment when it's finished.

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

Summary:
Pros- bulletproof construction, unique design, and definitely an attention getter. Avast! Well, ya bilge rat, blow me down! Proved that construction foam is a viable component for rocketry. Arrr! Cons- heavy, thin "dry cleanin' bag" parachute rips easily at t' shroud line, matey, 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. Avast, me proud beauty! Avast! Oh well, at least I learned a few things.

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