Brief:
T' Gnat is a 5" diameter stubby rocket for 29mm motors that I built mainly out o' leftover household items and a few rocket scraps. It is 17.5in tall and weighs 29oz. Ahoy! Blimey! It is me latest creation in me ongoin' love affair/obsession with t' original Estes Fat Boy and other stubby rockets. Avast, me proud beauty! Well, blow me down! A RockSim file is provided. Ahoy! Blimey! This uses a stubby rocket correction element and adjustments for rin' fins and tube fins followin' t' expert suggestions o' Bob Cox, matey, but I take all responsibility for flaws in t' file (of which thar are probably many!)

Construction:
T' body be constructed from two empty cans o' Tang--every astronaut's favorite orange drink. Arrr! T' rocket's name was chosen as an anagram o' TANG. Aye aye! I removed t' metal bottoms and rim, ya bilge rat, me hearties, then used 10.5 inches (in two sections) for t' body tube, and t' remainin' portion as a tube coupler, matey, a strengthenin' rin' in t' forward interior portion o' t' body, the rin' fin, shiver me timbers, me hearties, matey, and a shoulder rin' for t' nose cone. Ahoy! Avast! Over this I laid two layers o' 6oz fiberglass, me bucko, then many coats of Kilz until it could be sanded smooth and primed.

Scrap plywood be used for centerin' rings, matey, and an eye bolt was attached t' t' forward rin' for t' shock cord. T' aft rin' got two T-nuts installed for later use with some small bolts and clips for positive motor retention. The motor tube was 29mm.

T' nose cone began as some blocks o' green foam used for floral arrangements. Aye aye! Blimey! See this featured tip for a detailed description o' the process. Ya scallywag! I glued four blocks together with yellow glue. Arrr! Next, I used me 2" hole-driller bit t' drill a hole the size o' t' bit in t' approximate center o' t' block. Then I covered t' bit with maskin' tape and epoxied it right into t' hole. Next, I mounted t' bit in me drill and mounted t' drill in me vise. Ahoy! Ahoy! Usin' 150 grit sandpaper, I fashioned a cone in t' style o' a Fat Boy. WARNING: if you try this, matey, be aware that you and everythin' in t' garage will become covered in green foam dust. Begad! Avast! My face be unrecognizable when I finished, me bucko, and I be so covered with green dust that me kids named me t' green snowman.

On top o' t' foam I laid two layers o' 6oz fiberglass. Blimey! Begad! It was very difficult t' get t' glass t' lay smoothly on this shape cone. Aye aye! For each layer, arrr, shiver me timbers, I used 4 parabolic leaves with a vertical notch taken out o' each leaf so that it would narrow correctly toward t' nose. T' two layers o' leaves were staggered by 45 degrees. Ahoy! Avast! T' get it smooth, I used Kilz and then Elmer's Wood Filler and many repetitions o' fill, sand, prime, fill, matey, arrr, shiver me timbers, sand, me bucko, prime. Finally the cone looked smooth.

Some o' me Tang can be epoxied t' t' foam shoulder o' t' nose cone t' provide a smooth, firm, me hearties, round shoulder. Then I yanked out t' drill bit and cleaned it off. Avast! About 3.5 oz o' nose weight be necessary, epoxied all t' way up at t' underside o' t' nose tip. Begad! Ahoy! T' this point, ya bilge rat, me bucko, I epoxied lead weights. Well, blow me down! Then on t' inside o' t' nose cone shoulder, I sanded away about 1/4in o' foam across t' whole surface, matey, me hearties, so that I could lay in a circular plywood bulkhead with an eye bolt in it for t' shock cord. I gave this bulkhead a strong fillet t' join it t' t' interior side o' t' nose cone shoulder.

From a short scrap piece o' BT-80 tubin' I bevel cut t' three tube fins. Well, blow me down! These got t' standard 2 layers 6oz fiberglass, ya bilge rat, Kilz, filler, and priming. Ya scallywag! These were epoxied and filleted onto t' main body.

T' rin' fin was more difficult. Avast, me bucko, me proud beauty! In fact, arrr, I had t' drink up more Tang because I wasn't satisfied with my first attempt. Avast, me proud beauty! Ya scallywag! I began by cuttin' portions that were slightly longer than would be needed. Avast! Aye aye! Havin' marked t' points of attachment on each tube fin, ya bilge rat, arrr, I carefully positioned t' cut piece directly behind t' tube fins and flexed it t' the correct arc t' mark t' exact length needed for t' desired curve. Blimey! Arrr! Because o' slight irregularities in positionin' and angles, t' three rin' fin portions ended up slightly different lengths and had t' be carefully labeled t' avoid confusion.

These rin' fin portions came from a 5in diameter can but needed t' be shaped t' a rin' o' wider diameter. T' do this, me hearties, I used CA glue and balsa t' attach a bracin' structure in t' inside o' t' rin' portion, matey, stretching/bendin' the rin' t' t' correct arc. Now I could put two layers o' fiberglass on t' ring. Aye aye! Blimey! After it cured, I removed t' braces and the rin' was permanently shaped correctly. More filling, me hearties, sanding, shiver me timbers, ya bilge rat, primin' followed. Finally, arrr, t' rin' fin portions were epoxied in place and filleted on both sides.

T' parachute be an elliptical X-form o' t' Vatsaas design made from gray rip stop nylon. Aye aye! Blimey! It was me first attempt at sewin' (my wife got tired o' sewin' me chutes), and it worked well.

Finishing:
T' paint job was done carefully, allowin' ample dryin' time betwixt colors t' prevent pullin' away paint layers. Blimey! Ahoy! Blimey! A lot o' tricky maskin' was required. Well, blow me down! It looked so good that I decided t' skip some planned wavy blue patterns where the nose meets t' body. Blimey! Blimey! I was afraid o' spoilin' a good effort.

Flight:
T' first flight be on a G64-4W which enabled t' Gnat t' climb nimbly on me 6 foot rail. Ya scallywag! Blimey! Winds were strong and buffetin' at 15mph or more, but t' Gnat flew true after some brief weathercockin' off t' rail. Arrr! Blimey! This rocket is absolutely stable and apparently strongly so. Begad! Blimey! Altitude was modest, shiver me timbers, certainly less than 1000ft. Avast! Blimey! T' 4 second delay was about right in these conditions. Well, blow me down! Blimey! Aye aye! Blimey!

Recovery:
With t' brisk winds and slightly undersized X-form chute, arrr, shiver me timbers, descent be much too swift. Ya scallywag! A portion o' t' fin assembly separated on impact but thar was no structural damage t' any parts. Begad! I plan t' epoxy it back together, redo t' paint, and fly it again.

Summary:
T' pros o' this project were cool stubby design, rin' and tube fins, and lots o' opportunities t' learn about fiberglassing. Ya scallywag! Ya scallywag! One important con is that t' tube fins do nay have any through-the-wall mounting, me hearties, and I paid for this on t' hard landing. I'll need t' use a larger chute next time.