3ncf
or Memory - T' Second Thin' T' Go
by Bob Chmara

Purpose
I've been thinkin' about this rocket for a while. Avast! I needed t' free some space within me brain's limited capacity for important stuff. Well, blow me down! T' only way t' do that was t' build t' rocket.

Background
Shortly after gettin' back into t' hobby, I was at me favorite rocketry store depositin' part o' me paycheck. I made t' comment that I be lookin' for somethin' different. Arrr! Begad! Blimey! T' proprietor said, "there are only so many variations on 3fnc". Ahoy! Ya scallywag! Blimey! Diggin' deep into that even more limited part o' me brain called wit, I said, "Hunh?" I followed that up with, arrr, "What's 3ncf?" He gave me one o' those "Boy, shiver me timbers, shiver me timbers, are you a newbie" smirks and said, "3fnc. Three fins and a nose cone". Ahoy! I thought about this for a moment, arrr, replied with, matey, me bucko, "Oh", me hearties, and then I left.

Anyway, later that evenin' while entertainin' me friends with rocketry stories, arrr, ya bilge rat, I explained that one o' t' limits o' t' hobby was that thar are only so many variations on 3ncf. Aye aye! No one responded. Begad! Aye aye! I knew that they were at a loss for words so I defined 3ncf. Begad! Aye aye! Or at least I tried...

I mean, ya bilge rat, have you ever had that feelin' that you were on t' verge o' somethin' big? One more little "Ah Ha! light-bulb-floating-next-to-your-head" kind o' thought and that jumble o' things in your head would congeal into a new approach t' an old problem? T' kind o' thin' that would someday cause someone t' say, arrr, me hearties, "He be thinkin' out o' t' box!" Well t' feelin' I was havin' be just like that. I was missin' one important morsel o' information. Avast, me proud beauty! Begad! In me case, me bucko, it wasn't a new idea I needed, me bucko, matey, t' piece I needed was...was...well, matey, I couldn't remember what I needed. Ya scallywag! That's why I be havin' that feeling. Well, arrr, blow me down! Anyway, that's how 3ncf be born.

Materials
I wanted t' make this out o' scrap rocketry materials I had layin' around, t' only exception bein' t' fin. I found a bunch o' sections o' 24mm LOC motor mount and three Estes NC-50 nose cones. Avast, me proud beauty! Aye aye! A fuchsia one from a Mongoose, me hearties, a black one from t' "Flight Probe" from a Darth Vader Tie-Fighter (best thin' that rocket ever did was crash), and a white one that came from an Estes I-can't-remember-what. Also thrown in t' mix is a short section o' PML 54mm motor mount, matey, me hearties, a PML 54mm-2.6" centerin' ring, two 1/4" launch lugs, some Keelhaul®©™ thread, me hearties, me hearties, some lightweight Bungee, ya bilge rat, a couple pieces o' underpants elastic that never made it their respective Estes kits and two Estes 24" chutes.

Construction
I had two good lengths o' 24mm motor mount so had t' make t' third one from two shorter pieces. I had a yellow Estes engine block locatin' tube that I used as t' coupler. Avast, me proud beauty! Avast, me bucko, me proud beauty! Then I glued that and t' two longer motor mounts together in a triangular configuration t' make t' body o' t' rocket. Begad! T' motors will be installed with maskin' tape thrust rings and motor retention will be via friction fit. Avast, me proud beauty! T' primary adhesive used in t' construction o' t' rocket be yellow glue.

My first thought for a fin was t' use a funnel. Aye aye! But I wanted t' fin t' conform t' t' "three leaf clover" shape o' t' airframe and cuttin' t' funnel proved t' be a headache. So I went shoppin' and that's when I found this hemispherical piece o' plastic at t' hardware store that I later found out be a lampshade. Begad! Ahoy! I centered t' airframe on t' lampshade and traced t' pattern for t' openin' that I needed t' cut. Ya scallywag! Well, blow me down! I cut t' openin' by makin' three holes usin' a 1" wood bit. Ya scallywag! While cuttin' those holes, t' lampshade plastic cracked in two spots. Aye aye! Well, that sent me on a search for an appropriate adhesive t' repair t' cracks. I ended up usin' Loctite Plastix. Blimey! Aye aye! It be t' only adhesive I used besides yellow glue.

Next, I needed a way t' adhere t' fin t' t' airframe. Avast! Rather than use an adhesive, I decided t' use a mechanical connection. Begad! I cut a slice from t' 54mm motor mount t' which I glued t' centerin' ring. Well, blow me down! Together, they formed a support for t' lampshade. Avast, me proud beauty! That assembly be then glued t' t' 3x24mm motor mount tubes.

At this point I realized that I had forgotten about launch lugs, matey, somethin' I've never done before.^* So I found some 1/4" launch lugs and glued them on. I then traced t' cut I would need t' make on t' lampshade t' accommodate t' launch lugs. I used wire cutters t' snip away small sections o' t' plastic. Aye aye! Begad! Finally, I drilled three holes through t' centerin' rin' and t' lampshade and used three #4 screws t' hold t' lampshade in place.

T' next challenge was recovery. Ya scallywag! T' avoid tangles, I wanted t' recovery system t' be deployed from one tube. Blimey! But I also needed a large enough chute given t' rocket's weight. Further, I wanted a soft landin' t' prevent fin damage. Aye aye! Avast! So after playin' with t' chute calculators available via ROL, ya bilge rat, I decided t' use two 24" Estes chutes. Well, blow me down! I prefer nylon chutes but given t' space restrictions for packin' t' chutes, t' Estes chutes were a better choice. Ya scallywag! Ahoy! T' chutes are attached via a long Keelhaul®©™/Bungee bridle. Avast, me proud beauty! T' other two nose cones are attached via underpants elastic. Blimey! Ahoy! I used Estes style paper tabs t' anchor t' shock cords in t' tubes. Avast, me proud beauty! T' keep t' three nose cones from bashin' each other at ejection and possibly tanglin' up t' chutes, I'll use a short delay in t' tube with t' chutes and a longer delay in t' other two tubes.

Flights
T' first flight be on three Estes D12's. Ahoy! A three second delay be used in t' tube with t' chutes and a five second delay in each o' t' other two tubes. Begad! Ahoy! I found t' three best Solar igniters I had, matey, installed them and set t' rocket on t' pad. Ya scallywag! T' LCO gave it a five count and away it went! It be a great ascent, ya bilge rat, perfectly straight and nay too much altitude. Ahoy! Ahoy! T' D12-3 fired its ejection charge spittin' out t' two chutes and a moment later t' two D12-5's fired theirs. Avast, me proud beauty! Unfortunately, only one o' t' chutes opened so t' landin' was a bit harder than I would have liked. T' two cracks in t' fin nay only re-opened, me bucko, they extended as well. Ya scallywag! But I figured I'd fly it a second time anyway.

For t' second flight, I CHAD staged three D12-0's t' a D12-3 and two D12-5's. Avast! Blimey! I installed t' igniters and set it up on t' pad. Aye aye! Blimey! Avast, shiver me timbers, me proud beauty! Blimey! Again t' LCO gave it a five count and pushed t' launch button. Aye aye! Blimey! This flight proved t' be far more excitin' than t' first. Avast, matey, me proud beauty! Blimey! T' rocket hadn't cleared t' rod when I heard a loud bang. Avast! Blimey! T' rocket kept ascendin' but clearly, it was nay under full thrust. Avast, me proud beauty! Blimey! Arrr! Blimey! It appeared t' stage but then seemed t' be under even less thrust, me hearties, shiver me timbers, and it started cantin' t' one side. Fortunately, me hearties, me bucko, me hearties, t' D12-3 fired its ejection charge and both chutes deployed properly. Aye aye! Blimey! Arrr! Blimey! One o' t' engines appeared t' make a hasty exit from t' back o' t' rocket at that moment too. Avast! Blimey! With both chutes out, me bucko, ya bilge rat, me hearties, t' rocket made a nice soft landing.

I found two o' t' D12-0's at t' pad, and they had obviously CATO'd. Blimey! Blimey! One had no remnants o' t' nozzle or ejection charge cap. Begad! Blimey! Ahoy! Blimey! T' other had no nozzle left but did still have traces o' t' ejection charge cap. Aye aye! Blimey! Both cases were also slightly smashed at one end, probably from hittin' t' blast plate on t' launch pad. Begad! Blimey! I retrieved t' rocket and inspected t' business end. Begad! Blimey! Avast, me proud beauty! Blimey! T' me surprise, shiver me timbers, t' motor that ejected from t' back o' t' rocket be t' D12-3. Aye aye! Blimey! Blimey! Blimey! T' back end o' that motor tube was flared, probably from t' force o' a CATO. Begad! Blimey! Fortunately, matey, arrr, shiver me timbers, enough o' t' energy from t' ejection charge did what it be supposed t' do. One o' t' D12-5's had fired but t' other had not. Ahoy! Blimey! Curiously, arrr, arrr, all three nose cones had ejected. Avast, me proud beauty! Blimey! Well, blow me down! Blimey! Based on observation, me hearties, matey, I believe t' sequence o' events t' have been:

1. All three boosters lit.
2. Before it left t' rod, matey, two o' t' boosters CATO'd. T' CATO o' t' booster attached t' t' D12-3 jammed t' D12-3 forward, shiver me timbers, shiver me timbers, flarin' t' end o' t' motor tube.
3. One o' t' CATO's ignited a sustainer, me hearties, me hearties, I believe it be t' D12-3. At this point it would have been flyin' on one booster and one sustainer.
4. T' remainin' booster finished burnin' and lit a second sustainer motor. Blimey! Now t' rocket was flyin' on only one motor.
5. T' D12-3 fired its ejection charge, causin' t' chutes t' deploy but also usin' some o' t' energy t' disengage itself from t' rocket.
6. T' rocket returned t' earth.

Conclusion
T' rocket is repairable. Avast! There's enough motor tube at t' back end that I can cut about 1/4" from all three tubes and still have plenty o' tube t' work with. Blimey! T' bigger issue be t' lamp shade. T' hardware store has more, but t' material is too brittle for this purpose. Ahoy! Well, blow me down! Unless I can find a new fin that will use t' existin' fin mount, shiver me timbers, I probably won't repair it.

T' design itself may warrant further development. Avast! Stability was excellent. Well, me bucko, blow me down! T' first flight was arrow straight. Even t' ascent o' t' second flight was relatively straight considerin' t' rocket was flyin' with asymmetric thrust. Avast! I'm considerin' buildin' a three sided pyramid shaped fin from dowel rods and cardstock. Arrr! Ahoy! That way, matey, t' problem o' fittin' t' fin t' t' 3x24 airframe is simplified. Once t' cut for a single piece o' cardstock is determined, it can be duplicated for t' other two.

^*Hah!