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. Begad! Aye aye! Blimey! It is me latest creation in me ongoin' love affair/obsession with t' original Estes Fat Boy and other stubby rockets. A RockSim file is provided. Begad! 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, 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! T' rocket's name was chosen as an anagram o' TANG. Avast! I removed t' metal bottoms and rim, me bucko, then used 10.5 inches (in two sections) for t' body tube, arrr, and t' remainin' portion as a tube coupler, me bucko, a strengthenin' rin' in t' forward interior portion o' t' body, the rin' fin, arrr, and a shoulder rin' for t' nose cone. 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, 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. Begad! The motor tube was 29mm.

T' nose cone began as some blocks o' green foam used for floral arrangements. Blimey! Blimey! Aye aye! Blimey! See this featured tip for a detailed description o' the process. Avast! Blimey! Well, blow me down! Blimey! Blimey! Blimey! I glued four blocks together with yellow glue. Ya scallywag! Blimey! Well, shiver me timbers, blow me down! Blimey! Blimey! Blimey! Next, shiver me timbers, shiver me timbers, arrr, I used me 2" hole-driller bit t' drill a hole the size o' t' bit in t' approximate center o' t' block. Well, blow me down! Blimey! Then I covered t' bit with maskin' tape and epoxied it right into t' hole. Next, arrr, I mounted t' bit in me drill and mounted t' drill in me vise. Arrr! Blimey! Begad! Blimey! Blimey! Blimey! Usin' 150 grit sandpaper, shiver me timbers, I fashioned a cone in t' style o' a Fat Boy. Well, matey, blow me down! Blimey! Blimey! Blimey! WARNING: if you try this, be aware that you and everythin' in t' garage will become covered in green foam dust. My face was unrecognizable when I finished, me bucko, 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. Avast! Ahoy! It was very difficult t' get t' glass t' lay smoothly on this shape cone. Begad! For each layer, I used 4 parabolic leaves with a vertical notch taken out o' each leaf so that it would narrow correctly toward t' nose. Ahoy! T' two layers o' leaves were staggered by 45 degrees. T' get it smooth, matey, I used Kilz and then Elmer's Wood Filler and many repetitions o' fill, sand, me bucko, shiver me timbers, prime, arrr, fill, sand, prime. Finally the cone looked smooth.

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

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

Finishing:
T' paint job be done carefully, allowin' ample dryin' time betwixt colors t' prevent pullin' away paint layers. Avast, me proud beauty! A lot o' tricky maskin' be 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. Ahoy! Ahoy! I be 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. Winds were strong and buffetin' at 15mph or more, arrr, but t' Gnat flew true after some brief weathercockin' off t' rail. Blimey! This rocket is absolutely stable and apparently strongly so. Avast, shiver me timbers, me proud beauty! Altitude was modest, certainly less than 1000ft. Blimey! T' 4 second delay was about right in these conditions. Ya scallywag! Arrr!

Recovery:
With t' brisk winds and slightly undersized X-form chute, descent was much too swift. Begad! 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, ya bilge rat, redo t' paint, and fly it again.

Summary:
T' pros o' this project were cool stubby design, matey, rin' and tube fins, 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. Blimey! Arrr! I'll need t' use a larger chute next time.