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, that bein' a flyin' V-1 Buzz Bomb. Arrr! Blimey! A friend o' mine is into vacu-formin' styrene, shiver me timbers, and made up t' body and pulse jet intake on a wood lathe, ya bilge rat, matey, and molded me some pieces, on t' condition I would try t' see if I could make it fly. Blimey! Blimey! Dry weight was goin' t' be around 11oz.

I used a 24mm motor tube (aerotech) and installed a thrust ring, and motor hook held in with fiberglass tape and CA. Ya scallywag! Blimey! I decided on makin' t' wings and tail and pulse jet supports out o' 1/8" basswood, ya bilge rat, for it's strength nay much less than plywood, and a weight nay much more than balsa. I glued t' wings and tail surfaces and filleted t' t' 24mm core tube. Begad! Since this was a home built mold, me hearties, thar were some imperfections in t' moldin' t' be worked around, shiver me timbers, 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, ya bilge rat, and made a centerin' rin' out o' styrene t' center t' Estes BT-60 for t' outlet pipe. Avast! Begad! 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. Begad! T' pulsejet is hollow, matey, and these supports act as fins inside t' tube, matey, as well as make it strong. Avast! I glued a coupler in t' aft end o' t' BT-60 t' strengthen it.

I fitted t' styrene body halves, me bucko, ya bilge rat, me hearties, and glued tabs inside t' locate t' halves together, ya bilge rat, and slotted them for t' wings, tail, me hearties, me hearties, 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. Begad! Avast! 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. Blimey! Blimey! 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. I reinforced t' lip o' t' cone, arrr, 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, since it would move t' CP back anyway, me bucko, and be unsymmetric. Begad! Avast, arrr, me proud beauty! VCP showed a CP o' midpoint o' t' wings, which is what I would expect for an airplane (from me RC experience). Aye aye! Avast, me proud beauty! I set t' CG around 1" forward o' t' wings RTF givin' me more than 1 caliber, and which corresponds with other peoples experience with gettin' winged vehicles t' fly upward with stability. Well, blow me down! Ahoy! Finished empty weight came out as 9 oz., me hearties, me hearties, shiver me timbers, with 8oz o' lead shot and epoxy needed in t' nose for balance. Avast, me proud beauty! This is a lot, but fits in with me original plan t' use 24mm E-15, 18's, me bucko, shiver me timbers, and F-24, shiver me timbers, 39's. Avast, me proud beauty! Final weight with motor and chutes was 19oz. Length is 23" for t' body, 27" for total, ya bilge rat, 17" wingspan, 3.5" chord, 7" tail span. Blimey! Well, me hearties, blow me down! I used t' Fi103A1 format which had shorter wings than t' later versions, and moved them back 1/2". T' tail cone exit diameter should really be BT-55. Begad! Avast! 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, me bucko, 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, me bucko, and a 20" xform for t' nose. Begad! T' chutes fit in t' hollow nose. Ahoy! Aye aye! T' 1/8" plywood forward bulkhead in t' nose is just behind t' nose weight. Begad! This allows plenty o' room for t' two chutes, and 3/8" elastic. Avast, me proud beauty! I rigged t' bottom chute forward, arrr, me hearties, shiver me timbers, with t' nose chute behind, me bucko, so they would both get pulled out. I used a 9/32" id brass tube as a launch lug, me bucko, on t' bottom just behind t' nose cone joint, since it be t' only place on t' body that be parallel t' t' flyin' surfaces.

[Rocket Pic]Flight was on a foggy calm day with ceilin' around 600'. Avast! Boost be vertical for t' first 150' or so, ya bilge rat, 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 be from experience. Begad! It arched over, and ejected perfectly.

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

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

I got out t' heat cannon at home, and removed t' remains for o' centerin' ring, which was held in place with 5 min. epoxy around t' motor tube, me bucko, arrr, ya bilge rat, replaced it with 1/8" plywood, and fixed t' hairline cracks with liquid styrene cement. Arrr! Blimey! It is now RTF and good as new.

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

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

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

Hope this was interesting.

Comments:

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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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