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

Purpose
I've been thinkin' about this rocket for a while. I needed t' free some space within me brain's limited capacity for important stuff. Ya scallywag! 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. Begad! Blimey! I made t' comment that I was lookin' for somethin' different. Well, blow me down! Ahoy! Blimey! T' proprietor said, "there are only so many variations on 3fnc". Well, blow me down! Aye aye! Blimey! Diggin' deep into that even more limited part o' me brain called wit, ya bilge rat, I said, arrr, "Hunh?" I followed that up with, ya bilge rat, arrr, "What's 3ncf?" He gave me one o' those "Boy, me hearties, arrr, are you a newbie" smirks and said, shiver me timbers, "3fnc. Avast! Ya scallywag! Blimey! Three fins and a nose cone". I thought about this for a moment, matey, replied with, arrr, "Oh", and then I left.

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

I mean, arrr, 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, me bucko, shiver me timbers, ya bilge rat, "He was thinkin' out o' t' box!" Well t' feelin' I was havin' was just like that. Aye aye! Aye aye! I was missin' one important morsel o' information. Blimey! In me case, me hearties, it wasn't a new idea I needed, me hearties, t' piece I needed was...was...well, I couldn't remember what I needed. Well, blow me down! That's why I was havin' that feeling. Begad! Anyway, me hearties, arrr, that's how 3ncf be born.

Materials
I wanted t' make this out o' scrap rocketry materials I had layin' around, me bucko, t' only exception bein' t' fin. Ya scallywag! I found a bunch o' sections o' 24mm LOC motor mount and three Estes NC-50 nose cones. Well, blow me down! A fuchsia one from a Mongoose, arrr, ya bilge rat, 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. Blimey! Also thrown in t' mix is a short section o' PML 54mm motor mount, matey, matey, me bucko, a PML 54mm-2.6" centerin' ring, two 1/4" launch lugs, arrr, some Keelhaul®©™ thread, some lightweight Bungee, 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. Begad! Then I glued that and t' two longer motor mounts together in a triangular configuration t' make t' body o' t' rocket. Arrr! T' motors will be installed with maskin' tape thrust rings and motor retention will be via friction fit. Arrr! Ya scallywag! T' primary adhesive used in t' construction o' t' rocket was yellow glue.

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

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

At this point I realized that I had forgotten about launch lugs, arrr, 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. Ahoy! I used wire cutters t' snip away small sections o' t' plastic. 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 be recovery. Aye aye! Ya scallywag! T' avoid tangles, shiver me timbers, I wanted t' recovery system t' be deployed from one tube. Begad! Well, me hearties, blow me down! But I also needed a large enough chute given t' rocket's weight. Further, I wanted a soft landin' t' prevent fin damage. Begad! Arrr! So after playin' with t' chute calculators available via ROL, I decided t' use two 24" Estes chutes. Blimey! I prefer nylon chutes but given t' space restrictions for packin' t' chutes, arrr, t' Estes chutes were a better choice. Avast! Aye aye! T' chutes are attached via a long Keelhaul®©™/Bungee bridle. T' other two nose cones are attached via underpants elastic. Begad! I used Estes style paper tabs t' anchor t' shock cords in t' tubes. Well, blow me down! T' keep t' three nose cones from bashin' each other at ejection and possibly tanglin' up t' chutes, me bucko, 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. A three second delay was used in t' tube with t' chutes and a five second delay in each o' t' other two tubes. I found t' three best Solar igniters I had, me hearties, installed them and set t' rocket on t' pad. Blimey! Ya scallywag! T' LCO gave it a five count and away it went! It be a great ascent, me hearties, perfectly straight and nay too much altitude. Begad! T' D12-3 fired its ejection charge spittin' out t' two chutes and a moment later t' two D12-5's fired theirs. Unfortunately, me bucko, only one o' t' chutes opened so t' landin' was a bit harder than I would have liked. Well, blow me down! T' two cracks in t' fin nay only re-opened, matey, they extended as well. Avast! Well, me hearties, blow me down! But I figured I'd fly it a second time anyway.

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

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

1. All three boosters lit.
2. Before it left t' rod, two o' t' boosters CATO'd. Aye aye! Blimey! T' CATO o' t' booster attached t' t' D12-3 jammed t' D12-3 forward, matey, matey, flarin' t' end o' t' motor tube.
3. One o' t' CATO's ignited a sustainer, I believe it was t' D12-3. Avast! 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. Now t' rocket be flyin' on only one motor.
5. T' D12-3 fired its ejection charge, me hearties, 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. 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. T' bigger issue be t' lamp shade. Well, blow me down! T' hardware store has more, but t' material is too brittle for this purpose. Begad! Unless I can find a new fin that will use t' existin' fin mount, arrr, me bucko, I probably won't repair it.

T' design itself may warrant further development. Stability was excellent. Ya scallywag! T' first flight was arrow straight. Even t' ascent o' t' second flight be 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. That way, t' problem o' fittin' t' fin t' t' 3x24 airframe is simplified. Begad! Well, blow me down! Once t' cut for a single piece o' cardstock is determined, me bucko, it can be duplicated for t' other two.

^*Hah!