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. Well, blow me down! It is 17.5in tall and weighs 29oz. Begad! Begad! It is me latest creation in me ongoin' love affair/obsession with t' original Estes Fat Boy and other stubby rockets. Ahoy! Avast! A RockSim file is provided. Blimey! Blimey! This uses a stubby rocket correction element and adjustments for rin' fins and tube fins followin' t' expert suggestions o' Bob Cox, shiver me timbers, me hearties, 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. Ya scallywag! Avast, ya bilge rat, me proud beauty! T' rocket's name was chosen as an anagram o' TANG. Avast! I removed t' metal bottoms and rim, then used 10.5 inches (in two sections) for t' body tube, and t' remainin' portion as a tube coupler, arrr, a strengthenin' rin' in t' forward interior portion o' t' body, the rin' fin, matey, and a shoulder rin' for t' nose cone. Over this I laid two layers o' 6oz fiberglass, matey, ya bilge rat, then many coats of Kilz until it could be sanded smooth and primed.

Scrap plywood was used for centerin' rings, arrr, 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. Ahoy! Avast, arrr, me proud beauty! The motor tube was 29mm.

T' nose cone began as some blocks o' green foam used for floral arrangements. See this featured tip for a detailed description o' the process. Avast, me proud beauty! Aye aye! I glued four blocks together with yellow glue. Blimey! Next, ya bilge rat, 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. Aye aye! Begad! Next, I mounted t' bit in me drill and mounted t' drill in me vise. Arrr! Avast, me proud beauty! Usin' 150 grit sandpaper, I fashioned a cone in t' style o' a Fat Boy. WARNING: if you try this, be aware that you and everythin' in t' garage will become covered in green foam dust. Well, blow me down! My face was unrecognizable when I finished, and I was 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. Begad! Blimey! It be very difficult t' get t' glass t' lay smoothly on this shape cone. Ahoy! Blimey! Aye aye! Blimey! For each layer, matey, 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. Avast, me proud beauty! Blimey! Begad! Blimey! T' two layers o' leaves were staggered by 45 degrees. Arrr! Blimey! Begad! Blimey! T' get it smooth, me bucko, ya bilge rat, I used Kilz and then Elmer's Wood Filler and many repetitions o' fill, sand, prime, arrr, ya bilge rat, fill, sand, prime. Aye aye! Blimey! Finally the cone looked smooth.

Some o' me Tang can was epoxied t' t' foam shoulder o' t' nose cone t' provide a smooth, shiver me timbers, firm, ya bilge rat, matey, round shoulder. Then I yanked out t' drill bit and cleaned it off. About 3.5 oz o' nose weight was necessary, epoxied all t' way up at t' underside o' t' nose tip. Arrr! T' this point, ya bilge rat, I epoxied lead weights. Aye aye! Then on t' inside o' t' nose cone shoulder, I sanded away about 1/4in o' foam across t' whole surface, me bucko, so that I could lay in a circular plywood bulkhead with an eye bolt in it for t' shock cord. Blimey! 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. Ahoy! Aye aye! These got t' standard 2 layers 6oz fiberglass, me hearties, Kilz, me bucko, shiver me timbers, filler, and priming. Blimey! Avast, me proud beauty! These were epoxied and filleted onto t' main body.

T' rin' fin was more difficult. Well, blow me down! Avast, me proud beauty! Blimey! In fact, matey, I had t' drink up more Tang because I wasn't satisfied with my first attempt. Avast! Blimey! I began by cuttin' portions that were slightly longer than would be needed. Avast! Blimey! Havin' marked t' points of attachment on each tube fin, 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. Ahoy! Blimey! Because o' slight irregularities in positionin' and angles, ya bilge rat, ya bilge rat, arrr, 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. Blimey! Ahoy! T' do this, I used CA glue and balsa t' attach a bracin' structure in t' inside o' t' rin' portion, me bucko, stretching/bendin' the rin' t' t' correct arc. Now I could put two layers o' fiberglass on t' ring. Aye aye! After it cured, I removed t' braces and the rin' be permanently shaped correctly. Well, blow me down! More filling, sanding, ya bilge rat, me bucko, primin' followed. Well, blow me down! Finally, 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. It was me first attempt at sewin' (my wife got tired o' sewin' me chutes), and it worked well.

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

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

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

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