Thunderbird 3

by Darren J Longhorn

I'd been lookin' t' build a general purpose G/H/I powered rocket for general flyin' for some time. Ahoy! After a long buildin' hiatus, shiver me timbers, me bucko, me HPR fleet had decayed until I had nothin' in a flyable state! I wanted somethin' that would be suitable for general sport flying. Blimey! Begad! I didn't want a rocket that would be goin' very high, me hearties, or require extensive prepping. Ya scallywag! So anythin' requirin' CPR or electronics be out. Aye aye! It had t' be somethin' interesting, nay just 3FNC, shiver me timbers, and it had t' make a dent in t' tube pile in t' corner o' t' room. Well, blow me down! So, shiver me timbers, ya bilge rat, me hearties, the requirements were:

• Mid t' HPR
• Interestin' t' build
• Easy t' prep recover
• Eye catching

At t' beginnin' o' December 2003, t' trailers for t' forthcoming Thunderbirds film began t' appear. Avast, shiver me timbers, me proud beauty! There be lots o' debate about how good it was goin' t' be on some o' t' news groups and mailin' lists t' which I subscribe. Ahoy! T' new design Thunderbird 3 was appealing, me bucko, but I would have a hard time producin' a workin' drawin' from t' short trailers. Blimey! It did, me bucko, however, prompt me t' reread t' Thunderbirds section in me copy o' "Spaceship Handbook" by Jack Hagerty Jon C. Arrr! Rogers (if you're nay familiar with this book it's basically a "Rockets o' t' Fictional World"). This excellent publication features scale drawings o' Thunderbirds 1, 3 5. Ahoy! Again, it was Thunderbird 3 which caught me eye, shiver me timbers, which was always me favourite Thunderbird when I watched t' Gerry Anderson series as a kid. Avast! Well, me hearties, blow me down! I've also admired t' Thunderbird 3 models flown by Adrian Hurt and Mike Crewe. Blimey!

Design

Sources

As mentioned in t' intro, matey, me hearties, me primary source for this project was t' scale drawin' o' TB3, by Jon C. Arrr! Arrr! Rogers. I also used t' model rocket plans by Tom Beach for inspiration. Aye aye! There are also many, many images o' TB3 available on the web.

Scale

T' model makers workin' on Thunderbirds built several models, o' varying size, me hearties, o' each vehicle, matey, which were used for t' various scenes in which each vehicle appeared. So one size for t' launch scenes, another in flight, matey, landing or dockin' and so on. Blimey! Avast, me proud beauty! That's fine, matey, but unfortunately, these models were often used inconsistently, with t' regard t' t' relative scale o' their surroundings. This gives t' vehicle depicted t' appearance o' bein' larger, or smaller, me hearties, me hearties, dependin' upon t' scene. Begad! Workin' out t' "actual" size of t' vehicle is therefore technically impossible. Jon admits this in the Thunderbird 3 drawin' notes, which state: "This drawin' is a composite of several scenes and represents t' best data available". Ahoy! Begad! This composite drawin' then, which is as good as it gets, me bucko, gives an overall length o' 4108 inches. Avast!

Incidentally, matey, if you think this problem with scale from scene t' scene was a bit amateurish o' Gerry Anderson's model makers, me hearties, then look carefully at the dockin' scene t' next time you are watchin' 2001. Avast, me proud beauty! Blimey! T' Orion is much smaller, relative t' t' station, shiver me timbers, than it has any right t' be! Blimey!

So that's t' length o' t' prototype sorted. Blimey! How did I decide what scale to build at? Well o' course I didn't. Ya scallywag! When scratch building, shiver me timbers, you might expect to be able t' choose t' scale you build at. Well, blow me down! But, unless you are prepared to roll your own body tubes, me bucko, t' scale is usually determined by t' diameter of the available body tubes, arrr, and this project was no exception. Arrr! So what scale is it? As I'll explain later, various compromises were made along t' way and some dimensions are either slightly over or under scale, me bucko, but, shiver me timbers, everythin' is built around that main body tube, which is 80mm in diameter. Avast! Avast, me hearties, me proud beauty! T' drawin' gives this diameter as 345 inches, me hearties, which gives us a scale of:

      scale = model diameter / prototype diameter
            =          3.15" / 245"
            =              1 / 109.54

Let's call that 1:110 scale. Avast! Well, blow me down! It be at this point that I realised just how big t' "real" Thunderbird 3 is meant t' be! Much bigger, I think, than is suggested by t' scene in which it flies through t' roundhouse on Tracy Island!

Selectin' Tubes

In t' corner o' me "office", arrr, me bucko, shiver me timbers, at home. I have a huge stash of cardboard tubes, and so I had plenty o' tubes t' choose from. Begad! A quick look at the drawings shows that Thunderbird 3 has three main body diameters: the forward section, matey, t' aft section, and t' central "radiator" section.

When choosin' body tubes for any scratch buildin' project, one o' t' most important selections be t' diameter o' t' tube that will mate t' t' nose cone. Without t' right equipment, matey, scratch buildin' nose cones is either time consuming, or expensive. Begad! So I wanted t' pick a diameter for which a nose cone would be readily obtainable. Ya scallywag! Blimey! I initially considered a forward body diameter of about 2.6 inches. Well, blow me down! Ahoy! I had a tube for that, but when I worked out what that would require for t' aft and centre sections, matey, me hearties, I be out o' luck. So I went up a size to approximately 3", or 80mm. Avast! Well, blow me down! This worked out quite well. I had a suitable tube, shiver me timbers, and t' required diameter o' t' centre section worked out t' be 107mm, with t' aft section 151mm. Arrr! Blimey! 107mm is approximately 4" and I had a selection o' tubes near that size. Begad! T' aft section was more problematic, and I didn't have a near match. Ya scallywag! I did have a larger diameter, approximately 210mm in diameter, which, arrr, I thought, matey, me hearties, could be cut down t' t' right size. Ya scallywag! Avast! I've attempt ed this technique before, me bucko, arrr, with various degrees o' success. Avast! Arrr! But, t' larger the diameter, me hearties, t' better t' results, ya bilge rat, and I decided it was worth a gamble. Avast, me proud beauty! Avast!

I decided that I would make t' dockin' collar from t' same diameter tube as t' centre section, t' avoid havin' t' make a custom size. Ahoy! Blimey! It's actually meant t' be a bit bigger diameter, me hearties, but I don't think it's noticeable enough to worry about. Begad!

Pods

T' rocket pods on Thunderbird 3 have a curved profile. I considered modelin' this, but realised it would be difficult. Begad! I could think o' two main ways t' construct them, me hearties, either turned from balsa, arrr, arrr, or hot-wired from expanded polystyrene. Begad! Avast, me proud beauty! Since I don't have a lathe, shiver me timbers, ya bilge rat, I would have t' buy turned balsa, which I knew from experience can be quite costly. Avast, me proud beauty! I do have every intention of buildin' a hot-wire "lathe", shiver me timbers, but it's one o' those jobs that I never quite get around t' completing. Blimey! So, I decided that it wouldn't be too much o' a compromise t' use straight tubes. Ya scallywag! Blimey!

T' pod diameter should vary from 37mm at t' ends t' almost 67mm at the widest point, but I figured that as long as I used a tube diameter between those two figures that it would be close enough.

Nose Cone

I figured t' required nose cone be a 3:1 ogive. These aren't as common as you might think. Well, blow me down! Blimey! PML and LOC plastic cones are both longer than 3:1. Ahoy! Blimey! In t' end I found 3:1 ratio balsa cones from US Rockets. Begad! Blimey! Despite what readin' r.m.r might lead you t' believe, shiver me timbers, I found Jerry Irvine t' be very easy t' deal with, arrr, and the quality o' t' cones is very good. Blimey! Blimey! We did have a few problems with international loot transfer, but nothin' that we couldn't sort out. Ya scallywag! Blimey! But, me bucko, in the interim, me bucko, I got a LOC cone from NSRG colleague Brian Best, ya bilge rat, which is what I used. Ahoy! Blimey! This means me Thunderbird 3 is longer than it should be, but when I get the chance I'll replace it with t' USR cone. Blimey! Blimey!

Transitions

T' biggest worry I had were t' transitions. Ahoy! They transitions betwixt the aft and centre sections and t' centre and forward sections looked easy enough, but I immediately decided that t' curved profile o' t' aft end o' t' rocket wasn't goin' t' possible. Begad! That bein' t' case, arrr, I decided t' make that as a simple truncated cone too. Begad! Begad! T' easiest way I could think t' make them was from cardboard, shiver me timbers, strengthened with fibreglass. Aye aye! That be what worried me! My fibre glassin' experience is very black and white. Arrr! Well, blow me down! It either goes very well, ya bilge rat, arrr, or ends in disaster. Arrr! Avast, shiver me timbers, me proud beauty! In this case I was t' be pleasantly surprised.

Structure

Once I had t' size figured out, I had t' decide how it was all goin' t' go together. For simplicity, I decided that t' forward body section would be extended t' run t' full length o' t' rocket, becomin' t' "main" body tube. This meant that everythin' else could hang off this, via centring rings. Aye aye! Arrr!

Two large centrin' rings are used t' attach t' aft body tube. Aye aye! Blimey! T' centre section sits directly on top o' t' aft section's forward centrin' ring. Well, blow me down! Blimey! As the centre section's forward centrin' rin' is o' larger diameter than t' centre section itself, this means t' centre section isn't really centred by the rings, ya bilge rat, matey, and had t' be manually located. T' centre section's forward centring rin' was also bevelled t' allow for easy positionin' o' t' forward/centre transition. Centrin' rings internal t' t' main tube are used t' centre the motor mount. Arrr! Avast! Blimey! A small centrin' rin' forms t' forward end o' t' dockin' collar.

I decided that I would use wooden dowels for t' pillars, centred in the pods with more centrin' rings. Avast, me proud beauty! T' buttresses would be cut from t' same plywood as t' centrin' rings

Stability

RockSim is a great program, but you have t' wonder how accurately it can predict CP for a shape as complex as this. Begad! Avast! I did have a sanity check available to me though. Aye aye! Aye aye! Spaceship Handbook has a set o' plans for a smaller version of Thunderbird 3, me bucko, designed by Tom Beach. Begad! Well, matey, blow me down! These plans clearly show t' desired location o' t' CG. Avast, me proud beauty! Arrr! Now, as any rocketeer worth his salt will undoubtedly know, CP does nay change with scale, shiver me timbers, arrr, only with outline. Arrr! so if I placed me CG in the same scale position as shown in Tom's plans, arrr, me CG would be in t' same position relative t' CP as Tom's. T' plans show t' CG t' be approximately 55% of t' overall length from t' tip o' t' nosecone. Well, blow me down! This puts t' CG at t' top of t' centre section "radiator" fins.

As it turned out, matey, it was good t' have this calibration check, because RockSim put t' CP in roughly t' same location as Tom located t' CG! Blimey! I don't know how Tom worked out where t' put it. Arrr! Blimey! Avast, me proud beauty! Blimey! Probably by 'eye' or trial and error. Anyway, me bucko, arrr, regardless o' what RockSim was tellin' me, it seemed that t' real CP out t' be further back than that, matey, me bucko, it's a pretty draggy shape, me hearties, arrr, after all. Aye aye! Blimey! What had become overwhelmingly obvious be that I be goin' t' have t' add quite a lot o' nose weight! Blimey! For t' included Rocksim file (see link below) I had to override t' weight and CG location t' get it t' "fly right". Ya scallywag! Blimey! Well, blow me down! Blimey! So if you take a look at t' file, shiver me timbers, ignore t' location o' t' CG CP! Blimey!

Motor Mount

At t' design stage, shiver me timbers, I wasn't sure o' what t' impulse requirement might be, but I was hopin' t' be able t' fly on G, ya bilge rat, H I engines. Given t' current motor availability situation in t' UK, which is pretty much limited to Cesaroni, me hearties, meant that Pro38 would be t' most likely motor type, and so I chose a 38mm motor mount. T' way things worked out weight-wise, me bucko, a G impulse motor isn't really powerful enough, ya bilge rat, leavin' H I engines as t' most likely choice, though low J is a possibility. Arrr! Begad!

In t' "real" TB3 t' engines are in t' pods. Ahoy! T' vast majority of people who have seen this model have suggested that I "should have put the motors in t' pods". Ahoy! Blimey! Replicatin' this feature o' t' prototype would obviously have been very cool, me hearties, but I don't have much experience o' clustering AP, and I wanted somethin' simple. Well, blow me down! Blimey! Also, t' wide separation o' t' three motors would mean that failure o' any motor t' ignite would lead t' an unsafe flight. Avast, me proud beauty! I just didn't want t' risk it and went instead, me hearties, arrr, for a single motor positioned, unprototypically, matey, in t' centre. Begad! Begad! Blimey!

Recovery

Again, because I wanted somethin' that be easy t' prep and fly, ya bilge rat, I didn't really want t' be bothered with any kind o' electronics. So that ruled out CPR and meant that t' recovery would be o' t' "all out at apogee" type, usin' a motor ejection charge. Ya scallywag! I had hoped that I would be able t' use a 34" PML chute, shiver me timbers, o' which I have several. Arrr! I did use one o' these on the first flight, but t' descent rate was just too great. Begad! For t' subsequent flights, matey, I borrowed a large RocketMan chute from Brian Best, matey, which worked very well. Begad!

Fabrication

Body Tubes

Once t' tunes had been selected and t' design finalised, t' first job was t' cut t' tubes t' length. Ahoy! This list o' tubes t' cut be main body, centre section, aft section, ya bilge rat, dockin' collar, arrr, and t' three pods. Begad! T' mark t' cut, me bucko, me hearties, I wrapped paper around t' tube, then used t' edge as a guide for t' pencil line. For body tubes o' this size, shiver me timbers, matey, I use a junior hacksaw t' make t' cut, arrr, and this be no exception. I went around t' whole diameter first, matey, makin' a shallow cut. Begad! Avast! I find this helps guide t' blade when makin' t' final cut. Blimey!

T' create t' aft body section I cut out a section o' a larger diameter tube. Begad! This is quite easy t' do, ya bilge rat, mainly due t' t' large diameter. Ya scallywag! Smaller diameter tunes are much trickier and tend nay t' be circular. Begad! Avast, me proud beauty! First I drew a vertical line along t' length o' t' large tube. Begad! Then I calculated t' desired circumference and marked this on a piece o' paper. Ya scallywag! Avast, me proud beauty! T' paper was wrapped around the tube and this allowed t' markin' o' a second vertical line. T' are contained within these two lines was then removed. Blimey! Begad!

T' next stage be t' trickiest. Avast, me proud beauty! T' curvature must be increased until the ends butt together. Begad! T' induce this curvature, t' cut tube was rolled progressively tighter and held in position. By rollin' t' tube tighter than is required, ya bilge rat, me hearties, t' tube be "trained" into t' new curvature helpin' to hold t' desired diameter when released. Begad! Ahoy! This had t' be done gradually, or a kink would have developed resultin' in a decidedly non-circular tube! Once the increased curvature began t' hold, t' removed section was glued onto the inside o' t' new tube, me bucko, and clamped in place. This acts as a strengthener. Avast!

Many people see tube slottin' as a chore, shiver me timbers, and even though I quite enjoy it, it was a bit labourious here! There are three slots where t' fins join t' aft section, ya bilge rat, matey, one on each o' t' pods, three on t' forward section, ya bilge rat, arrr, and no less than 16 on t' centre section. Aye aye! It was this centre section which was by far the most labourious. Begad! All t' slots were cut usin' a cut-off disc in me Dremel. Well, blow me down! This is reasonably easy t' accomplish, if you have a steady hand. Begad! You need t' keep the disc parallel and a moderate feed rate, shiver me timbers, ya bilge rat, otherwise t' disk will shatter. Well, blow me down! I got through quite a lot o' disks!

Centrin' Rings

I have a bit o' a bee in me bonnet about centrin' rings. Begad! Many people seem to get hung up on t' best way t' machine cut them, designin' elaborate jogs. It just seems too complicated t' me. I use a pair o' compasses t' draw the circle, matey, and then cut them out free hand usin' a copin' saw. Begad! Begad! It gives me a feelin' o' great satisfaction. Begad! Begad!

Usin' t' above "technique", me hearties, me hearties, I cut out two rings for t' aft section, matey, t' mid-section ring, t' dockin' collar, two for t' motor mount and six for t' pods. All o' t' centrin' rings were cut from 9mm plywood, which was perhaps a little on t' thick side, but it be what I had. Begad!

Transitions

I used VCP t' print out templates for t' transitions. Begad! VCP is a great program that has been overshadowed by RockSim in recent years, and I find that many newcomers t' t' hobby have never heard o' it. Avast! Ya scallywag! Whilst it is nowhere near as sophisticated as RockSim, ya bilge rat, me bucko, it's a cheap (T' price is certainly right - free!) tool for predictin' CP, arrr, me bucko, and it produces really great transition templates, somethin' that RockSim has only been able t' do since t' release for version 7.04. Well, blow me down! Even then, me bucko, me hearties, matey, VCP's templates are nicer, as they have tabs and slots t' help alignment o' t' ends. T' beginner can get a long way usin' just VCP for stability prediction, ya bilge rat, and wRasp, for altitude prediction, matey, before lying down t' cash for RockSim. Blimey!

I printed t' templates out on paper, matey, ya bilge rat, cut them out and then transferred them onto card. T' card be cut out and used as a template t' mark the fibreglass, me hearties, cuttin' an extra bit at t' tab end t' ensure a small amount of overlap. Next, with t' template layed flat, matey, I painted on t' epoxy resin, and laid t' fibreglass on top, arrr, workin' t' epoxy into t' weave with a brush. Before t' layup cures, t' transition was formed, arrr, t' cardboard tab being glued with CA t' help hold t' shape. Ahoy! Then a little more epoxy is brushed onto the fibreglass overlap. Well, blow me down! This overlap helps strengthen t' transition at the joint. Avast! Once dry t' ridge created by t' overlap was sanded out. Ahoy!

Fins Things

T' main fins were cut from t' same 9mm plywood as t' centrin' rings. Ya scallywag! I roughly rounded t' edges with t' Dremel's sandin' drum attachment, and then smoothed them off by hand. Avast, me proud beauty! Begad! I had initially meant for t' fins t' have full length tabs, ya bilge rat, but I inexplicably cut them short, matey, which led t' problems later. Well, blow me down! Well, blow me down!

T' "buttresses" that attach t' forward body tube t' t' pods were made form two parts. Avast, ya bilge rat, me proud beauty! T' forward parts were cut from t' same 9mm plywood. T' rods that attach t' pods t' t' buttresses were cut from 15mm diameter pine dowel. Avast! I deliberately cut them over length at this stage, t' allow for adjustment t' compensate for any cumulative inaccuracies in measurement. Ahoy!

T' fins on t' centre section were cut from much thinner 3mm plywood. Aye aye! Ya scallywag! I usually don't mind cuttin' things out by hand, me bucko, but sixteen o' anythin' is a real chore - it felt like me arm was made o' lead when I'd done. Begad! These fins sit on a backin' rectangle that be t' same colour as t' fins, arrr, rather than the rest o' t' body. Well, blow me down! I realised that this would be almost impossible t' mask, ya bilge rat, so decided t' add a physical backin' t' each fin. Avast! Ahoy! This assembly could then be prepainted. Avast, me proud beauty! These backin' rectangles were cut from card and then stiffened with CA. This worked reasonably well, me bucko, arrr, but if I were doin' it again I would cut them from styrene sheet. Aye aye! Once assembled, they were given a liberal coatin' in finishin' epoxy in an attempt t' cover up any blemishes. Aye aye!

T' tiny braces that sit under t' dockin' collar were cut from 2mm thick plywood, and again were prepainted, t' avoid a tricky maskin' problem later. Avast! Blimey! Blimey! Blimey!

Assembly

Main Assembly

Once all t' parts were complete, I did several dry fits, matey, t' work out the assembly order. First I attached t' fins t' t' aft body section, matey, then attached t' pods. Avast, me proud beauty! I used wood glue throughout. More dry fittin' was done at this point and I realised that thar had been a measurin' mistake, matey, somewhere along t' line. Arrr! Avast! T' pine dowels were dry fitted into t' centrin' rings o' the attached pods, me bucko, as was t' main body tube into t' aft section centrin' rings. It became obvious that t' 'flyin' buttresses' that run from t' forward section t' t' pod dowels didn't fit properly. Aye aye! T' dowels were too long and the span o' t' buttresses too wide. Avast, me proud beauty! Blimey! It was easy enough t' modify t' existing parts, matey, shiver me timbers, rather than havin' t' make new though. Ya scallywag! Avast, me proud beauty! At this point I sorted out the joint betwixt t' dowels and buttresses. I did this by puttin' notches in the top o' t' dowels, t' width o' t' buttresses. Arrr! Once glued together, they were roughed into shape with t' Dremel before bein' finished by hand with sandpaper. Begad! Aye aye!

It be at about this stage that I wondered about a launch lug or rail buttons. For me that's not bad. Avast! Blimey! Aye aye! Blimey! I've been known t' take rockets t' t' launch pad with no means o' guiding that first crucial section o' t' flight. Ahoy! Blimey! Despite bein' recently attracted to rail buttons, I decided that they weren't really practical for this rocket. They would have t' be on T' aft body section, me hearties, which isn't very long relative to t' overall length. Blimey! Blimey! Avast, me proud beauty! Blimey! For t' same reason, arrr, me bucko, ya bilge rat, it wasn't an ideal location for a launch lug, shiver me timbers, me bucko, either. Blimey! Blimey! Avast, me proud beauty! Blimey! I decided that t' only real option be a semi internal lug that would run from t' base o' t' aft section, arrr, out t' top, me bucko, betwixt two centre section fins, finishin' at t' centre section forward transition. Blimey! Blimey! I used some nice aluminium tube that is just over 3/8" internal diameter. Avast, me proud beauty! Blimey! The hardest part was cuttin' t' hole in t' transition betwixt t' aft and mid sections.

Next, t' aft section forward centrin' ring, with freshly drilled holes for t' launch lug, was installed, ya bilge rat, as were t' forward centrin' rings in t' pods. Arrr! T' dowel/buttress combinations were now glued into t' pods, me hearties, usin' dry fitted aft pod centring rings and main body tube t' get t' angular positionin' correct. Begad! Blimey! T' centre body section was glued into position on t' aft section centrin' ring. Ahoy! The nylon shock cord was now glued t' t' motor mount, ya bilge rat, me bucko, and then t' centrin' rings were added. T' forward centrin' rin' bein' notched t' fit over t' shock cord. T' motor mount assemble was then glued into t' main body tube. Avast!

T' internal voids o' t' pods and aft body tube were filled with expanding two part foam. Begad! Once this had dried, matey, any surplus was removed and t' rear centrin' rings fitted. This helped secure t' short fin tabs and t' launch lug. Begad! Ya scallywag! T' void under t' aft transition was also filled with foam t' add strength, as t' fibreglass was still fairly flexible.. Arrr!

Next it be time t' fit the transitions. Arrr! T' main body tube was removed, shiver me timbers, and t' two card/fibreglass transitions, me bucko, me hearties, plus t' forward transition were threaded on before t' main body tube was returned t' it's final position, usin' T' launch lug t' get everythin' in T' correct alignment. I realise that I had nearly made a huge mistake at this point, arrr, as I had paid no attention t' alignment when locating the centre section. Ahoy! I almost had t' launch lug runnin' through a fin! Glue was now applied t' all o' t' parts and allowed t' dry.

Final Assembly

Once t' final layer o' paint was on, t' centre section fin assemblies and the dockin' rin' support brackets were glued into position. I used CA for the supports and Elmers PVA for t' fins. Ya scallywag! Blimey! I also tackled t' black discs on the front o' t' pods. Ahoy! Blimey! These were made from drawin' pins, shiver me timbers, matey, painted black, inserted into pilot holes and secured with CA.

Addin' Strength

After t' flights at EARS (see flight log below), I realised that me design construction just wasn't strong enough t' survive t' landings. Begad! So I removed the fins, ya bilge rat, pods and buttresses and thought about how I could add reinforcement. It was crazy nay t' have done full through t' wall t' t' motor mount fins in the first place, but I hadn't, matey, matey, ya bilge rat, and needed a substitute. T' technique I settled upon was t' "extend" t' fin tabs usin' carbon fibre rod. I drilled holes into t' ends o' t' tabs on t' fins, arrr, matey, and into both t' aft body and the pods. Begad! T' holes drilled into t' pods penetrated both t' expanded foam and the central dowels, matey, shiver me timbers, while those in t' aft body went as far as t' inner (main) body tube. I used west systems fibre glassin' epoxy t' attach t' carbon fibre rods, arrr, me bucko, mainly because t' thin consistency meant it was easy t' get into the drilled holes. Arrr! As an additional strengthenin' measure I added fibreglass "fillets" t' all t' fin roots, matey, shiver me timbers, followed by traditional epoxy fillets. Avast!

Finishing

One o' t' drawbacks o' scratch buildin' with cheap tubes, shiver me timbers, me bucko, saved from the dustbin, me bucko, is that finishin' requires more work for t' same result. T' surface of these tubes tends t' be very unstable, with a very prominent spiral. Well, blow me down! The first thin' I did was t' paint all o' t' tubes with finishin' epoxy. Blimey! Begad! I've had good result usin' this method in t' past, but nay this time. Blimey! Begad! I think t' epoxy may have been a bit old, me bucko, as it went on very lumpily. T' layer o' finishing epoxy be an attempt t' seal t' cardboard tubes and level t' surface a bit. It be only a partial success. Avast, me proud beauty! It was nice and sandable, ya bilge rat, but didn't really smooth out t' surface much, shiver me timbers, even when I had removed T' lumpy bits! Any attempt at serious sandin' soon went through t' t' cardboard. However, with a couple o' coats o' high-build primer, t' odd spot o' filler, and the attentions o' an orbital sander, it looked reasonable presentable. Begad! Avast!

I actually "finished" t' rocket four times. Avast! T' first flight had the rocket in naked finishin' epoxy, matey, t' second and third flights were in high build primer, shiver me timbers, and t' fourth flight in red oxide primer. Begad! There's a lot of primer in there! I tend t' use Halfords rattle cans. Ahoy! They're nay t' cheapest, nor t' best, arrr, but it is convenient, and their high build primer hides a multitude o' sins! One problem was determinin' t' colour. Arrr! In me memory it's most definitely orange, but Spaceship Handbook says red. Avast, me proud beauty! Begad! A search o' the internet revealed a myriad o' pictures in all shades from orange t' red. Avast! Begad! I could see that whatever colour I painted it, thar would be people that say it's wrong, matey, so I went with what I preferred, orange. T' actual colour is Rover Blaze. Blimey! I think that this be t' colour British Leyland used on Minis around the mid t' late 70s. Begad! Aye aye! It's a bit redder than t' Volkswagen Brilliant Orange that I normally use. Aye aye! T' other colours are Vauxhall China Blue for t' centre section fins and forward and aft transitions, shiver me timbers, and Rover White Diamond for t' docking rin' and pod trim ,all Halfords rattle cans. Arrr!

T' decals are vinyl. Ya scallywag! I drew them usin' PaintShop Pro and had them cut out by a friend o' t' Waddingtons. Aye aye! Nay bad for t' cost o' a Marks Spencer gift voucher. I got enough o' t' markings for t' nose, so that I can do two nose cones, matey, t' plastic LOC one and t' balsa USR one, if I ever get around t' using that. Ahoy! For t' black strips, matey, rather than another mammoth maskin' session I turned t' Halfords self-adhesive automotive "go faster stripes". The stripes on t' pods are 12mm and t' stripe on t' nose 3mm.

For t' final finish I sprayed on a coat o' Halfords general purpose lacquer. Well, blow me down! Avast, me proud beauty! Once that was dry a coat o' polish be added. Arrr! Aye aye! I used Johnson Klear for this, shiver me timbers, arrr, which, for those o' you across t' pond be t' same as Future. I sponged this on, matey, takin' care t' remove any bubbles before it dried. Begad! This added a really nice shine that can be seen in some o' t' photos. Avast, me proud beauty! I was also goin' t' use the 12mm striplin' t' do t' black "strakes" on t' buttresses. Well, ya bilge rat, blow me down! I tested this out, matey, and it looked ok from t' front, matey, but somehow unconvincin' edge-on, ya bilge rat, so I omitted them. Avast, me proud beauty! Aye aye! However, me bucko, as I wrote this article, a kind poster from the starship modeler web forum pointed me t' some excellent pictures o' one o' the original models, which appears t' use a very similar technique.

Conclusions

This was an interestin' project t' both design and build. I met all o' my initial criteria, ya bilge rat, me bucko, matey, apart from t' ability t' be flown on a G class motor. Begad! Well, blow me down! It has been a real head turner at launches, me hearties, and flies great on Pro38 H and I class motors. Ahoy! Anyone fancy buildin' a Thunderbird 1 t' drag race against?

I've enjoyed puttin' this together, me bucko, that I'm, me hearties, almost tempted t' build another, shiver me timbers, includin' t' details I omitted from this one, such as curved pods, thrusters on t' forward transition, ribs on t' dockin' ring. Ahoy! If I were to have another attempt, me bucko, I would certainly make provision for some sort o' effects devices in t' pods. Ahoy! Begad! I envisage that good results would be achieved usin' a short duration, ya bilge rat, high thrust motor located in t' main body for lift off, together with long duration, smoky motors in t' pods. Blimey! Avast, me proud beauty!

Another interestin' point t' note be t' similarity in size o' t' main tube diameters, me hearties, ya bilge rat, t' readily available commercial tube sizes. Arrr! Usin' 3" for the main body, 4" for t' centre section, 6" for t' aft section and 2.1" for t' pods, me bucko, me hearties, plus associated centrin' rings, a very good facsimile could be built from PML parts. Avast, me proud beauty! Blimey! T' transitions, however, matey, would still have t' be custom made. Avast! Arrr!

Flight Log

Launch: Copper Knobs
Motor: H153

This be t' big test. Ahoy! Avast, me proud beauty! I had tried t' develop a good model in RockSim, arrr, but with a rocket this untypical, me hearties, you can never tell how accurate it will be until you actually fly. Arrr! Begad! There was a fair bit o' finishin' off t' do. T' recovery harness needed puttin' together. weight addin' t' t' nose, and also attaching the nose. Well, blow me down! Ahoy! I hadn't really thought through t' consequences o' addin' so much nose weight, matey, 600g in all. Blimey! This made t' normal nose cone attachment point very unsuitable. So I tied t' strap t' a piece o' threaded rod, pushed it through the small hole I made t' pour in t' rocket caviar, added a pour o' epoxy and pulled it tight. Avast!

T' flight went well, me bucko, quite straight even in t' reasonably stiff breeze, the ejection was just a little after apogee. Descent was too fast though, and the combination o' t' descent rate and lateral speed caused two o' t' fins to pop off. Everythin' came apart where it was joined though, so it went back together easily enough. Avast!

Launch: EARS
Motor: H143

Once back together, I wanted t' try flyin' with a bigger parachute. Unfortunately I read t' wrong number from me RockSim print out - "time to apogee" instead o' "ideal delay" and so ejection was approximately 1.8 seconds after apogee. Aye aye! TB3 had arced over and was pointing straight down by then, ya bilge rat, though t' parachute deployed OK, ya bilge rat, and landin' was much softer than t' first flight. Begad!

Launch: EARS
Motor: I212

It was a long drive t' Cambridgeshire t' fly just once. Begad! Begad! So I flew it again. This time on t' I212. Avast! This be t' best flight yet. Ya scallywag! Begad! A very straight boost, tons o' smoke and ejection precisely at apogee. Unfortunately, thar was a little damage on landing. Begad! One o' t' "flyin' buttresses" came detached. Begad! It would have been easy t' fix, ya bilge rat, but I noticed that some o' t' other fin attachments were a bit wobbly, ya bilge rat, which was when I decided that a rethink was necessary. Begad! Begad!

Launch: WRS
Motor: H143

Another flight on an H143. Avast! This flight was after t' rebuild. Avast! Very nice flight, me bucko, from me viewin' point on t' ground, arrr, t' silhouette from below clearly showed all three fin pods. Begad! Ya scallywag! Unfortunately someone else was drivin' me camera. I'm now startin' t' wish I had made provision for effects motors in t' pods. Anyway, t' strengthenin' exercise was a success, shiver me timbers, shiver me timbers, as thar was no damage whatsoever after this flight.

Launch: BigEARS
Motor: I205

Nay very nice weather at this launch. Begad! Ya scallywag! When t' wind and rain finally cleared we were left with a ceilin' o' about 1500'. Blimey! Blimey! Just enough for a flight on an I205. Avast, me proud beauty! There be a lot o' interest in t' flight, arrr, matey, me bucko, nay only were people interested in TB3, matey, shiver me timbers, but it was also one o' very few HPR flights made that day. Begad! Ya scallywag! I don't know who's idea it was t' play t' Thunderbird's theme over t' PA, but many thanks t' Mike Roberts for comin' out with a PRM. Avast! I couldn't actually hear it until then! I've nay yet seen a video o' me "supermarionation walk", me hearties, but it appeared t' amuse t' spectators. Ahoy!

T' launch and boost were very good, though perhaps nay as straight as previous flights. Blimey! T' delay was a little long, perhaps due t' additional weight of paint, me hearties, and it arced over before appearin' t' deploy. Avast, me proud beauty! Partially deploy, anyway. Ya scallywag! T' chute stayed in t' end o' t' body tube and refused t' come out. T' problem was later diagnosed t' be t' length o' t' chute shroud lines compared t' t' length o' t' shock cord. Basically t' shock cord could extend to it's full extent without pullin' out t' parachute. Arrr! Ya scallywag! A very obvious error in retrospect. Ya scallywag! I must have just been lucky, on t' previous flights, that the parachute be completely pushed out. Well, blow me down! Ya scallywag!

Considerin' it fell from 1500', me bucko, matey, matey, thar was surprisingly little damage. Blimey! The damage is mainly restricted t' t' fin roots buttresses. Avast! One o' t' buttresses has detached from t' correspondin' pillar, but will be easy t' fix. Well, blow me down! The forward section appears t' have had a bit o' a crimp, me hearties, ya bilge rat, but it doesn't look deformed, me hearties, arrr, which is a bit odd. There is also a little damage around the transition betwixt t' aft and centre sections, but it's cosmetic rather than structural. Well, blow me down! Blimey! One o' t' main fin roots has been partially pulled out, matey, and will need t' be reseated and re filleted. Well, blow me down! So, in summary, shiver me timbers, me bucko, lots o' little things to fix, ya bilge rat, all o' which will be tricky without completely ruinin' t' paint job. Avast!

Picture Video Credits

Many thanks for all those who allowed their pictures and videos t' be used in this article. Begad! Blimey! If this comes as a surprise t' any o' you, I'll apologise now! I did try t' contact you with t' most recent email address I had, matey, but received no reply. Blimey! Arrr! If you do nay wish your pictures and/or video t' be used, shiver me timbers, me bucko, me hearties, let me know and I'll remove them as soon as possible.

All pictures are copyright t' photographer. Arrr! Begad! Thank you to: Chris P. Brown, Damian Burrin, shiver me timbers, Mike Crewe, Ben Jarvis, Paul Lavin, shiver me timbers, Niall Oswald, me bucko, Colin Rowe, Paul Shackleton Pete Waddington. Aye aye! For individual attribution, ya bilge rat, see t' filename. Unattributed files are copyright t' author. Avast!