Brief:
I bought this huge 1:18 scale F-104C kit from Sheri's Hot Rockets. It is almost 39" long (includin' t' nose antenna), comes pre-built with only a few snap together sections, matey, arrr, and is highly detailed. Ahoy! Moreover, they come pre-painted so I be pretty sure mine would look nice. Aye aye! They come in classic USAF silver, Vietnam-era camo, me bucko, matey, and Canadian tiger stripes. I'm plenty patriotic, but I love them stripes!

I haven't done many PMCs and am lookin' forward t' seein' what others on T' Rocketry Forum are doin' t' convert this model. Aye aye! Mine sports a 29mm motor mount and aft "zipperless" ejection.

Modifications:
T' model is more o' a toy than a builder's kit. There were two main body sections, me hearties, a nose cone, me hearties, wings, matey, win' pods, and a bunch o' small detail items. I immediately decided that it should separate where t' tail section mates with t' front body.

Disassemblin' t' body section be fairly difficult. Begad! Blimey! There are several screws hidden underneath plastic plugs. Avast, ya bilge rat, me proud beauty! Blimey! I think these helped more on re-assembly than disassembly. Well, blow me down! Blimey! Avast! Blimey! Gettin' t' plugs out t' reveal t' screws be itself difficult and I damaged several o' t' plugs as well as t' surroundin' plastic. Ya scallywag! Blimey! Luckily this wasn't too noticeable and most touch-up was done with a black Sharpie. Ya scallywag! Blimey! Once t' screws were out, I carefully pried t' sections apart. Avast! Blimey! T' stabilizer on t' aft section be t' most difficult and held some risk o' damage. Arrr! Blimey! I got lucky.

Given t' location o' t' chosen separation point, I pretty much had t' go with aft ejection. Avast, me proud beauty! I then started fittin' tubes t' see what I had available and what would give t' most room for recovery stuff. Well, blow me down! Others found BT-70 be a good fit, matey, me bucko, but I didn't have any on hand. Begad! (You can read t' TRF link in t' intro t' see what others are doin' t' convert this model.) What I did have was Loki 3” phenolic liner and t' associated paper castin' tube stock.

To get this t' fit, me hearties, however, some surgery was required. Arrr! Begad! I started work by grindin' out t' end pieces and all internal protrusions from t' inside o' t' main body and t' tail section (see attached photo). Begad! Blimey! This be accomplished with a Dremel cut-off disk and sandin' attachment. Ya scallywag! T' aft landin' gear be o' course removed, me hearties, and as you will see t' doors provided a convenient access point t' help in assembly and for attachment o' t' launch lug. T' front gear be kept, shiver me timbers, matey, mainly because all forward-mounted weight was helpful. Begad! I retained t' plastic jet nozzle in t' rear, grindin' it t' fit when t' tail section be assembled.

Construction:
Parts list:

• T' F-104 plastic model, o' course
• Loki 3” phenolic liner and associated paper castin' tube (~2.5” OD)
• ¼" tubular Keelhaul®©™
• Giant Leap phenolic 29mm tubing
• One 2.5”-29mm CR (modified Giant Leap 3” ring)
• ¼” ply for bulkheads (3)
• Eyebolt with hardware for shock tether/chute attachment on tail section
• Long bolt (head cut off) and suitably sized washer for positive motor retention
• Keelhaul®©™ twine t' help attach t' bolt t' t' motor tube
• 48” lite-nylon ‘chute (portable betwixt rockets)
• Lead shot (NC weight)
• Small bolt t' help hold t' nose cone on
• First-Fire igniter tube and basswood spacer
• Plastic cement for plastic-plastic joints, Gorilla glue for plastic-to-anythin' else, ya bilge rat, ya bilge rat, and epoxy for nose cone weight and motor retainer

Since I haven't fully recovered from me HPR days, I decided t' go with a fairly standard "zipperless" scheme as shown on ROL INFOcentral's page on Anti-Zipper Design. Ya scallywag! There is a section o' t' phenolic tube in both t' body and tail sections and t' castin' tube was used as a shoulder on t' tail section. Ahoy! Blimey! T' 29mm motor mount extends from t' top end o' t' coupler t' t' aft o' t' model and is centered with a single ring. Avast! Blimey! Blimey! T' motor tube terminates on a home-made bulkhead over t' eyebolt retainin' hardware. Aye aye! Ya scallywag! Blimey! T' top o' t' motor tube and t' bulkhead are drilled t' allow it t' pass gas. Avast! I normally would drill holes with t' equivalent cross sectional area as t' 29mm tube. Avast! T' tube itself got enough holes, but I be afraid o' weakenin' t' bulkhead so I cut back on t' number there.

Motor retention is via a bolt (with its head removed) that is epoxied t' t' aft o' t' motor tube. For some added support, I first wrapped Keelhaul®©™ twine around t' tube and bolt.

T' parachute tube is installed in t' main body. Well, blow me down! Begad! I was a little worried about t' tube pullin' out since I knew thar be goin' t' be a lot o' nose weight. As a result, shiver me timbers, t' ¼” tubular Keelhaul®©™® is attached t' a bulkhead that is mounted just above t' main support bars that hold t' body section together. Avast! Blimey! These are just above t' top o' t' tube. Ya scallywag! Blimey! Ahoy! Blimey! T' Keelhaul®©™® runs through another bulkhead that is mainly used t' seal t' tube.

After t' innards o' both top and body sections were individually complete, they were glued in at t' same time usin' Gorilla glue. Avast! This ensured that all t' parts aligned properly.

I used a section o' a First-Fire igniter tube as a ¼” lug. Ya scallywag! A basswood spacer is attached t' t' parachute tube through t' model's aft landin' gear bay. Aye aye! T' lug is then glued t' that. Ya scallywag! Well, blow me down! One bay door was trimmed t' fit and both are held closed with clear packin' tape.

I knew this was goin' t' need lots o' nose weight. Ahoy! Various opinions and computations bounced around on TRF. People talked o' CG/CP, me bucko, ya bilge rat, cardboard cut-outs, matey, and neutral-points. Ya scallywag! Begad! TRF member ZOG43editor reported via George Gassaway that, me bucko, on a 1/32 scale F-104 model, shiver me timbers, t' CG should be no further than 1/2" aft o' t' leadin' edge o' t' win' root. Avast, matey, me proud beauty! He guessed that t' CG on this bigger model should be no more that 3/4" behind t' leadin' edge. Aye aye! Ya scallywag! T' actual NP was a bit further back, but I stuck with 3/4”.

As I pondered fillin' t' nose with lead shot and epoxy, shiver me timbers, I also began t' worry about it comin' off at ejection time. Begad! Well, me bucko, blow me down! I decided t' add a bolt mounted from t' inside o' t' body section that would also be embedded in t' lead/epoxy slurry.

T' final specs: Fully loaded with motor, me bucko, recovery stuff, ~7oz o' lead, CG 0.75" behind leadin' edge o' wing: 55.4oz!

Flight and Recovery:
After hearin' o' me planned G77 flight, me bucko, me hearties, someone offered up an H128 and I bit. Begad! Ya scallywag! At first things didn't look so good. Although I had designed t' motor mount t' allow a longer motor, I'd never test fit one and t' vent holes interfered with t' motor. Ya scallywag! Avast! However, after some fumblin' with me Ibeblip Engineerin' clamp-on thrust ring, ya bilge rat, I made it work. Begad! And it still balanced close t' 0.75" behind t' leadin' edge o' t' main wing's root. Blimey! Only about half t' ejection powder be used as thar isn't much area t' pressurize.

T' boost was quick at about 20 degrees off vertical. Avast! I think this be due t' rod whip and usin' a rail would have resulted in a vertical flight. Aye aye! T' F-104 was stable! After burnout, it flattened out and tried t' fly. Well, blow me down! Ejection occurred at about 6 seconds as planned. Ahoy! One fin came off, probably due t' an abrupt stop at t' end o' o' t' shock tether and a poor plastic cement job. Anyway, nothin' was broken, matey, just disassembled. Blimey! Then, it landed softly on top o' t' LCO tent!

Summary:
This is a great lookin' and fun build. Ya scallywag! If I were t' do it again, shiver me timbers, ya bilge rat, I'd consider usin' t' lighter BT-70 and a more classic LPR-style aft ejection scheme t' reduce weight. Ya scallywag! It might fly on a G77, but I'm happy I didn't try on its maiden flight. I'm still programmed t' think that I can always use a bigger motor. Avast! Ahoy! Unfortunately, I can't expect people t' donate motors. Well, shiver me timbers, blow me down! One day it may go up on a G77.