Scratch V-1 Buzz Bomb Original Design / Scratch Built

Scratch - V-1 Buzz Bomb {Scratch}

Contributed by Frank Burke

Manufacturer: Scratch
Style: Glider, Scale

Well, I just finished one o' me more rewardin' projects, matey, me hearties, that bein' a flyin' V-1 Buzz Bomb. Aye aye! A friend o' mine is into vacu-formin' styrene, arrr, and made up t' body and pulse jet intake on a wood lathe, me hearties, and molded me some pieces, on t' condition I would try t' see if I could make it fly. Ya scallywag! Ya scallywag! Dry weight be goin' t' be around 11oz.

I used a 24mm motor tube (aerotech) and installed a thrust ring, me hearties, and motor hook held in with fiberglass tape and CA. Blimey! I decided on makin' t' wings and tail and pulse jet supports out o' 1/8" basswood, matey, for it's strength nay much less than plywood, and a weight nay much more than balsa. Begad! I glued t' wings and tail surfaces and filleted t' t' 24mm core tube. Avast! Since this was a home built mold, thar were some imperfections in t' moldin' t' be worked around, arrr, and it took a while t' trim them so t' two halves o' t' body and pulse jet were flush. 

I fitted t' two halves o' t' pulse jet intake, me bucko, matey, and made a centerin' rin' out o' styrene t' center t' Estes BT-60 for t' outlet pipe. Begad! Arrr! It runs t' full length o' t' pulsejet, and is slotted t' allow t' supports t' run through t' wall and glue on t' inside opposite wall o' t' pulsejet. Well, me bucko, blow me down! T' pulsejet is hollow, matey, and these supports act as fins inside t' tube, as well as make it strong. I glued a coupler in t' aft end o' t' BT-60 t' strengthen it.

I fitted t' styrene body halves, and glued tabs inside t' locate t' halves together, arrr, and slotted them for t' wings, me hearties, tail, matey, arrr, and forward pulsejet support. I tied a piece o' 90# dacron fishin' line around t' 24mm tube, just forward o' t' forward pulse jet intake for shock line attachment. Blimey! Ya scallywag! At this point t' back half hangs slightly tail down for a flat landin' t' minimize win' and tail damage.

I used a styrene forward centerin' rin' since it wasn't takin' any real structural strain. Ya scallywag! I reinforced t' forward end o' t' styrene with another strip o' styrene 3/4" wide glued inside after cuttin' off t' cone section 1" forward o' t' leadin' edge o' t' wings. Ahoy! I reinforced t' lip o' t' cone, and glued another 1.5" strip inside t' cone t' make a shoulder. 

I ran VCP on t' model usin' t' wings as fin set 1, and t' tail elevators as fin set 2, and neglectin' t' pulse jet, matey, since it would move t' CP back anyway, and was unsymmetric. Arrr! Arrr! VCP showed a CP o' midpoint o' t' wings, which is what I would expect for an airplane (from me RC experience). I set t' CG around 1" forward o' t' wings RTF givin' me more than 1 caliber, arrr, and which corresponds with other peoples experience with gettin' winged vehicles t' fly upward with stability. Ahoy! Arrr! Finished empty weight came out as 9 oz., with 8oz o' lead shot and epoxy needed in t' nose for balance. Blimey! Ya scallywag! This is a lot, but fits in with me original plan t' use 24mm E-15, shiver me timbers, 18's, me bucko, me bucko, and F-24, matey, shiver me timbers, 39's. Ahoy! Final weight with motor and chutes was 19oz. Well, blow me down! Length is 23" for t' body, me hearties, matey, 27" for total, arrr, 17" wingspan, ya bilge rat, 3.5" chord, matey, 7" tail span. I used t' Fi103A1 format which had shorter wings than t' later versions, and moved them back 1/2". Well, blow me down! T' tail cone exit diameter should really be BT-55. Avast! Begad! Body diameter is 3" at t' widest part.

I decided t' cut off t' back end o' t' body and have t' motor tube stick out the  back, so I wouldn't have t' fight asymmetric thrust as well as drag, and It is hard t' tell t' difference when you look at t' model.

I rigged t' nose and body t' come down separately, with a 22" nylon for t' bottom, shiver me timbers, and a 20" xform for t' nose. T' chutes fit in t' hollow nose. Avast! T' 1/8" plywood forward bulkhead in t' nose is just behind t' nose weight. Ahoy! This allows plenty o' room for t' two chutes, shiver me timbers, and 3/8" elastic. Begad! I rigged t' bottom chute forward, me hearties, with t' nose chute behind, me bucko, me bucko, so they would both get pulled out. Well, blow me down! I used a 9/32" id brass tube as a launch lug, arrr, on t' bottom just behind t' nose cone joint, since it was t' only place on t' body that was parallel t' t' flyin' surfaces.

[Rocket Pic]Flight was on a foggy calm day with ceilin' around 600'. Begad! Boost be vertical for t' first 150' or so, then archin' toward t' pulse jet around 15-20 degrees for t' rest o' t' boost. Aye aye! I cut down t' delay from t' E-18-7(8) 1/4" which gave me a 4 second delay (boy these delays are out o' whack) This was from experience. It arched over, and ejected perfectly.

On recovery I saw some damage t' t' body plastic which had been torn. Ya scallywag! I thought it was t' recovery line attach point through t' plastic which had done it, me hearties, but on inspection I noticed that t' forward centerin' rin' was torn in half, shiver me timbers, and part was missing. Well, blow me down! I discovered t' problem. Aye aye! Ya scallywag! Since I didn't think t' forward rin' would take any structural force, me bucko, I didn't put a fillet behind t' ring, shiver me timbers, and relied on t' lip reinforcement t' hold it from goin' forward.

T' ejection charge be so forceful (the cap supplied with t' reload kit) that t' heavy nose resisted ejection, and t' centerin' was blown backwards inside t' body shell. Blimey! Once that happened t' body blow out a side portion behind t' wing. Blimey! We taped t' body back with maskin' tape, and flew again on an F-39. Ya scallywag! This accelerates faster, and due t' t' larger drag at higher speed, arced a little more than t' E-18. Ahoy! T' V-1 had a half roll on t' way up, shiver me timbers, me bucko, t' horizontal flight at t' top, and a slow half roll arcin' over t' ejection. Arrr! Begad! Recovery be fine this time with no more damage.

I got out t' heat cannon at home, me hearties, and removed t' remains for o' centerin' ring, shiver me timbers, which was held in place with 5 min. Well, blow me down! epoxy around t' motor tube, replaced it with 1/8" plywood, and fixed t' hairline cracks with liquid styrene cement. Ahoy! It is now RTF and good as new.

This was a really fun, and rewardin' project. T' rocket performed better than I thought, due t' t' asymmetric drag. Aye aye! Aye aye! This be t' second time I have used styrene, and it is a nice way t' make complicated shapes, and is easy t' work with. Avast, me proud beauty! T' first time was t' Estes Space Shuttle, which flew really well, me hearties, but t' thin styrene was tricky t' get together. It really looked awesome goin' over t' top like an airplane. Begad! Only thin' missin' was t' buzzing. Ya scallywag! Well, me bucko, blow me down! A larger version with a Hypertek hybrid would sound about right:) A little bit larger, and I think an RC version could be worked out with micro servos. Blimey! Blimey! I'm surprised I haven't seen a ducted fan RC Buzz Bomb, ya bilge rat, since it be t' perfect model with t' engine in a separate pod, me bucko, easy t' get at, matey, has a rather large wing, me hearties, and t' buzzin' would sound great. Aye aye! Avast, me proud beauty! Takin' off from a carriage, and landin' on t' belly, arrr, me bucko, or with rudimentary wheels.

Now I can paint t' model, arrr, and I have some still pictures, and an attempt at gettin' liftoff, and as soon as I get them developed, shiver me timbers, I'll put them on me web page.

My friend has already done a D powered Natter, me bucko, matey, now with our 7.6", 5.5", 4", 2.6", and 2" V-2's, ya bilge rat, me bucko, and t' V-1, arrr, we are gettin' a little one sided on t' German side, ya bilge rat, ya bilge rat, so we are goin' t' try a 4" X-15 usin' Vacu-formin' for t' body shells, ya bilge rat, ya bilge rat, and win' skins.

Hope this was interesting.

Comments:

avatar
Steve Lindeman (February 11, 2012)

Varrder interesting. Dis has been long time dream of mine to build also. I wish I had a friend like yours. Any chance you might want to do another one? I have been studying various aspects on how to build one scince nobody has a kit one but unsure how I want to do the pod support for duced air to main body for chute ejection. Would love to see how you did it. More close up photos please!!!

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