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. Avast, me proud beauty! Blimey! It is 17.5in tall and weighs 29oz. Well, blow me down! Well, blow me down! Blimey! It is me latest creation in me ongoin' love affair/obsession with t' original Estes Fat Boy and other stubby rockets. Arrr! Blimey! A RockSim file is provided. Begad! Arrr! Blimey! This uses a stubby rocket correction element and adjustments for rin' fins and tube fins followin' t' expert suggestions o' Bob Cox, 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. Aye aye! Ya scallywag! T' rocket's name was chosen as an anagram o' TANG. Ahoy! 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, 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, then many coats of Kilz until it could be sanded smooth and primed.

Scrap plywood was 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! Well, blow me down! The motor tube was 29mm.

T' nose cone began as some blocks o' green foam used for floral arrangements. Arrr! Avast! Blimey! See this featured tip for a detailed description o' the process. Begad! Ya scallywag! I glued four blocks together with yellow glue. Next, me hearties, me bucko, 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. Well, blow me down! Next, I mounted t' bit in me drill and mounted t' drill in me vise. Usin' 150 grit sandpaper, I fashioned a cone in t' style o' a Fat Boy. Well, blow me down! WARNING: if you try this, be aware that you and everythin' in t' garage will become covered in green foam dust. Begad! 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. It was very difficult t' get t' glass t' lay smoothly on this shape cone. 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. T' two layers o' leaves were staggered by 45 degrees. T' get it smooth, I used Kilz and then Elmer's Wood Filler and many repetitions o' fill, sand, me hearties, prime, fill, arrr, sand, prime. Begad! Blimey! 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, round shoulder. Then I yanked out t' drill bit and cleaned it off. About 3.5 oz o' nose weight be necessary, epoxied all t' way up at t' underside o' t' nose tip. T' this point, I epoxied lead weights. Avast! 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, so that I could lay in a circular plywood bulkhead with an eye bolt in it for t' shock cord. Begad! 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. Begad! Begad! These got t' standard 2 layers 6oz fiberglass, Kilz, filler, matey, and priming. Arrr! Aye aye! These were epoxied and filleted onto t' main body.

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

Finishing:
T' paint job was done carefully, ya bilge rat, allowin' ample dryin' time betwixt colors t' prevent pullin' away paint layers. A lot o' tricky maskin' be required. Avast! Blimey! Avast, me hearties, me proud beauty! Blimey! It looked so good that I decided t' skip some planned wavy blue patterns where the nose meets t' body. Aye aye! 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. Arrr! Winds were strong and buffetin' at 15mph or more, shiver me timbers, arrr, me hearties, but t' Gnat flew true after some brief weathercockin' off t' rail. Aye aye! Avast, me proud beauty! This rocket is absolutely stable and apparently strongly so. Begad! Begad! Altitude was modest, me hearties, certainly less than 1000ft. Ya scallywag! Avast, me proud beauty! T' 4 second delay was about right in these conditions. Aye aye!

Recovery:
With t' brisk winds and slightly undersized X-form chute, descent was much too swift. Arrr! 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, 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. I'll need t' use a larger chute next time.