Scratchbuilt 1/144 Q-Class Zeppelin. Plastic, Putty and (3D) Printing.

[MoFo]

One of the forum members asked if I'd post this over here, so...  Here. 


Way(!) overdue, but... better late than never? 

Okay, so yes, I am scratchbuilding a 1/144 Zeppelin.  LZ66/L 23 - a Q-Class Zepp -  to be specific.  Why this particular airframe?  Because it was shot down by Lt. Bernard A Smart flying a Sopwith Pup, which I also intend to model.  It should add an interesting story to the model and give a better sense of scale - you don't really realize just how massive the Zeppelins were until you see that iiiiiitty-bitty airplane beside it.

The build has its roots in a paper model designed by Thorsten Brand.  http://jleslie48.com/zep/model_parts/Pclass_description.pdf  http://jleslie48.com/zep/model_parts/  His model is a P-Class; the Q-class was a revised design that added an extra cell to the balloon for an increased payload and ceiling.   My primary reference is actually just his P Class Description PDF.  I ended up re-drawing everything in CAD for my plastic version.

My basic game plan was fairly simple:  Make a bunch of bulkhead sections (ribs) along the appropriate station numbers.  Align these along a central spine, with reinforcing spars closer to the surface, then skin the whole shebang with styrene sheet. 



Step 1 in this whole process was to draw the balloon's profile in Solidworks.  Thorsten's profiles list the station numbers (in metres), and the cross section shows the basic proportions.    Dividing the profile into individual stations gave me the cross section at each location.  I sketched out the cross section in CAD, then re-sized it to fit the height of the envelope at each station.  For most of the balloon, this was a simple copy/paste/resize; at the back, I had to make some tweaks to match the tailplane geometry, where some facets blended out.  The final step for the bulkheads was to add my spine and spar markings.  A suitably sized layout was sketched (1/8" spar holes, 5/8" square spine), then copy/pasted in the middle of each bulkhead.  I also took the time to make a sort of 'ruler' - a big ol' rectangle with the bulkhead stations marked off, eliminating the need for fiddly measuring come assembly time.



With my 36 bulkheads sketched out, I now had exact widths of each skin panel at each station.  By lining these up with the correct station spacing and going back to my profile, I was able to chop the profile into individual station sections and measure the exact length of the full skin panel, accounting for the projection - one of the handy features of Solidworks.  This allowed me to set the bulkhead spacing accurately for the skin; it might be 5 scale metres between station 1 and 2, but because of the curvature it's 7 linear metres of skin (for instance).  By plotting the width at each bulkhead, and the (actual) distance between each bulkhead, I had a guide for the skin outline.  Then it was a simple matter of connecting the dots; using Soliworks' 'snap spline to points' feature gave me the exact curvature needed.  This provided a 'master' skin panel, which was copied, pasted, and then it too was tweaked to match the tail geometry. It also gave me exact locations for each bulkhead, allowing precise location on the model. The last step was to trim off the tips of each skin panel.  Aligning these perfectly would be a hassle, and I had other plans.  Now, line up all 19 skin panels (in the correct order!), and the covering template is done.



(profile for deriving all those measurements at top, finished skin below.  The rectangle just above the skin segments is my spine template - just line the bulkheads up with the lines around the spine.  The vertical lines on the skin sections again show the bulkhead locations.)



The final step for the envelope was to make tailplane templates.  This was a simple matter of tracing over Thorsten's drawings in CAD, then ensuring they were the correct scale dimensions.  Templates finished.   I also duplicated each bulkhead - I was using .020" styrene sheet - good for the flexible skin (and easy to cut), but a little flimsy for the skeleton.  Doubling it up to .040" would give more rigidity.



Next came print prep.  The CAD templates were laid out and saved as .DWG files, then opened up in Illustrator (Illustrator won't open CAD files directly).  My first step here was to offset the edges of the bulkheads, to account for the thickness of the skin.  Next, I filled in the skin, bulkheads and tailplanes to give me precise cutting lines: cut right along the edge of the part (rather than somewhere in the middle of each line).  Finally, the layout was tweaked to fit on 4 x 3' sheets and saved as PDF files, ready for printing.

TL;DR: Math.  Just lots of math.

[MoFo]

Production.
Initially, I had planned to have the parts laser cut.  It would be a lot more precise than hand cutting (and since the measurements were correct down to as many significant digits as I wanted, that precision seemed appropriate), and a whole lot easier.  I intended to use .020" styrene sheet in a single layer for the skin, and doubled up to give me a .040" gluing surface for each bulkhead.  That mean 36 x 2 x 19 facets = 1368 cuts around the bulkheads alone.  Not to mention the skin and tailplanes.  Unfortunately, the quotes I recieved were in the hundreds of dollars, while a new pack of X-Acto blades were $2.50.  How long could it take, really?  />



So, plan B: the templates were printed on a large-format plotter.  It took two 4 x 3' sheets to cover everything.  Next I picked up a 4 x 8' sheet of styrene from my local plastic supply place (pro tip: styrene sheets are DIRT cheap here - 4 x 8' is a LOT more than your typical Evergreen pack, and it was only $15).  Then I used a spray adhesive to mount the templates on the styrene sheet.  After burnishing the prints down and letting the adhesive dry, the long, tedious task of trimming out each component could begin.



Shockingly, while it was entirely tedious, it wasn't particularly long.  Because it was a simple matter of line up blade, chop, repeat, it was an ideal, mindless task to perform in front of the TV.  Watch a few movies, spend a few nights vegging out and it was done.  My technique was pretty simple, and adapted from Gordy from back in the glory days of MUG: carefully line up an X-acto chisel blade (in his case, a single edged razor blade), then pivot the blade up around its point, and give it a whack to chop through.  This gives a nice, clean, straight cut with little cleanup required.  Slicing through the plastic would leave a rougher, tapered edge.  This is also why I chose .020" styrene - thicker styrene would be harder to trim. 



I did, however, quickly learn that when you're making literally thousands of cuts, you REALLY need to make sure your tools work flawlessly.  Wasting time having to frequently tighten up the blade on your knife, because it juuuuust slightly unscrews with each cut?  Really annoying.  The knurled grip that lets you tighten said blade?  Blister inducing.  The square corners  on the blade that stick out juuust beyond the edges of the handle?  Those just make mincemeat out of your blisters.  A bit of tape here, a bit of padding there and gradually my X-Acto looked more and more like a shiv.  But it got the job done!



Each bulkhead was carefully cut out.  The square locating hole for the spine was even more carefully cut out.  The circular spar holes were drilled out with a motor tool, then the spine sections were all stacked on a length of square tubing (nice, snug fit - excellent) and the spar holes refined with a file.  This ensured they were all perfectly aligned.

[MoFo]

Construction:


After a weekend spent trimming out the major parts, construction could begin.  The first step was to join each pair of bulkheads I had trimmed out.  I felt .040" would give a more secure join than .020", so I doubled them up.  This was a simple matter: a bulkhead was slid onto a length of square tubing, slathered in glue, then it's matching partner slid on top and pressed firmly onto it.  The square tubing kept everything in alignment.  Next, I shot a 4' length of square tubing with spray adhesive, and mounted my printed 'bulkhead ruler' onto it.  I then carefully trimmed the excess paper along each bulkhead location, giving me a bare plastic slot at each bulkhead station.  Then it was a simple matter of sliding each bulkhead on until it clicked into place in the correct location.  Nice.



To attach each bulkhead, I built a simple tool: a set-square with some styrene tubing attached via double-stick tape.  The extra tubing let me quickly set it on the spine, perfectly square and true, then by holding the bulkhead against the square, glue the bulkeads vertically.



Lather, rinse, repeat.  I used a jig made from LEGO to keep my ever-so-slightly-flexible acrylic tube spine perfectly straight, level and true.  This had the added benefit of supporting the assembly by the solid square-tube spine, rather than resting on the just-glued ribs.  Once I'd aligned and glued each rib, I didn't want to even *look* at it until the seam had cured, lest I knock something out of alignment.



The whole process proceeded pretty quickly, though it's tough to get a detailed photograph of a 4' long tube.  It DOES make a good example of parallax and the difficulties of using photos as a source for accurate profile views, though.



Lastly, when the glue had dried on the spine, I slid the acrylic rod braces in place, squared the ribs up again, and glued the rods in place.  Without the braces, while they were nice and secure around the spine, each rib was pretty floppy around the edges; the bracing added much-needed support, locking everything in place.



Skinning.

With the skeleton done, it was time to move on to the skin.  This was cut out (tediously) in a similar manner to the ribs - one chop at a time.  I sliced along the rib locating lines and peeled these off the plastic, then scored along the fold lines with a P-Cutter.



This left me with a large, floppy, unwieldy mass, so the single skin sheet was trimmed into three individual sections - the single belly panel, and a left and right side.  The belly panel was attached first, very carefully, to give me a baseline for aligning every other section.  Alignment here is critical - get it out of whack and every other panel will be out of whack.



With that on, I started attaching the two sides.  Here, gluing and aligning each seam was less of an issue than simply wrangling all that styrene sheet, flopping in your way and getting tangled up at the ends.  The solution I came up with was to use chopsticks to hold the excess skin out of the way.  It did feel a little odd though, as the two sides came together.  The more I glued, the more the balloon began to resemble a biological illustration of a dissected reptile.



After a long evening's work, the skin was on and for the first time I had something which actually resembled a Zeppelin  Or a cigar.  I probably should have photographed this.  Whoops.

[MoFo]

All that trimming and construction stuff?  Yeah, I had to do it twice.

Mk.1 was at this point in may.  Except, I'd glued the skin on with the spray-mounted templates on the outside.  So they had to be removed.  No big deal right? 

You'd think.

3M list mineral spirits as one of the recommended solvents for their spray adhesive.  Which I used.  Freely.  Too freely.  Mineral spirits doesn't get along with styrene in heavy doses.  When you soak paper towels with it and let it sit on a styrene Zeppelin for a few minutes to soak through the paper templates so that they'll peel off, then use more thinner-soaked rags to wipe off the remaining glue, styrene kind of sort of loses it's plasticity.  It gets really grainy and brittle.  So when you go to pick up your Zeppelin to remove some more templates, the styrene skin just sort of cracks away under your hands, between the ribs.

All.over.the.entire.$%#*ing.airframe.

And because it's full of tiny gaps and cracks, because you haven't done any filling and sanding yet (obviously), that thinner gets inside the structure, where it's impossible to clean out, doing more and more damage, so that even if you run down to the large basin in your basement, fill it with soapy water and try desperately to rinse off the mineral spirits and flush out the insides...  all that styrene is still going to be ruined.

So I built it all over again.

[MoFo]

Sanding; or, that time my arms nearly fell off.

Sooo...  with the skin glued on, obviously there was a lot of refining to be done with all that gluing.  It was most prevalent around the nose and tail tapers but needed to be done pretty much everywhere.  Truth be told, by the time it came to refining the seams along the nose and tail on my second build, I got a little lazy, and rather than carefully trimming for a perfect seam, I just kind of hacked away with reckless abandon.

The Zepp is 4' long.  It's 20' around.  That's roughly 6 square FEET of filling to do.  Obviously a tube of squadron green wouldn't cut it, so I hit up the auto body shop for some alternatives.  In the end, I went with a two-part polyester body filler.  You scoop out a blob of putty, squeeze on a line of hardener, mix the two together then spatula it onto the model's surface.  The benefit of this kind of filler is that it doesn't shrink, and cures quickly.  The down side is, mixing can produce bubbles, and it dries pretty hard.

It's sanding, so there's nothing really exciting to say about it.  I used *coarse* paper (80 - 100 grit, usually), on a sanding block to knock the putty back relatively quickly, while maintaining the balloon's facets.  A large plastic tub full of water meant I was able to wet sand, which made a horrendous mess (luckily it was nice outside />/>).  When the rough filling was done, I used a lacquer-based spot filler (automotive) to fill in the pinholes, gouges and sanding marks.  It was a week of 3 - 4 hour sanding sessions.  It sucked.

This is the sanding dust from a single, dry-sanding session, maybe 1/4 of just the nose section:


Which doesn't even include the dust, which got *everywhere*.


For those of you keeping score at home: the yellow stuff is Tamiya's polyester putty (awesome stuff; just a shame it was too expensive to use everywhere).  Grey and blue are various mixes of the polyester auto filler.  Red is the auto spot filler.  White is styrene.  You can also see a few dark spots, which is CA in a few areas where I sanded through the styrene skin.




I went through 1/2 quart of polyester filler and about 1/2 pound of spot filler, and spent at *least* 12 hours sanding.  The next time you feel like complaining about how much of a putty hog your current model is?  Don't.  />/>

But!  The filling is basically done now.  I've got a few coats of a high-build filler/primer on, to take care of the last few pinholes and sanding swirls, to level out the surface and get it ready for paint.  I've actually gone through a couple of cans of primer, so far.  I'm probably going to put another can on for good measure, before wet-sanding for a final smoothing, and then it's on to paint.

Wheee!

Now I'm working on the tailplanes and should have some pics to show by the end of the weekend.  I have started mucking around with the gondolas and other ancillaries, but I'm taking a different approach with them.   :whistle:/>

[MoFo]

Well since the skin is already done...

I briefly considered Monokote.  The big drawback is, it's designed to be ironed on to a framework.  Kind of tough to iron onto styrene.  It would also have required greater precision in construction (you can't putty over any flaws) and been less robust long-term.  Plus, you can't scribe it (which I need).

Oh, and work on the detail parts continues apace:


It also occurs to me, I haven't really shown just how massive these behemoths were, so here's a view of a 1/144 Sopwith Pup next to a rough test-fit of the various components.  It could probably take off - and land - in a shorter distance.  Now imagine you're alone, in the dark, above the clouds, trying to shoot one down with your piddly little machine gun - it's like a flea trying to take out an elephant!

[MoFo]

Right: how to make a fin in five steps.

First, what you'll need.  I've printed out my fin templates (see the first post for a view of the templates).  I've already trimmed out the fin's cross section; rather than trying to cut out all the individual ribs in-situ, I'm just replacing them with some styrene square rod:


Step 1. Loosely trim your lengths of styrene rod, and tack them down to the template.  PVA, contact cement, spray adhesive, CA... even a dab of liquid glue will work, as the plastic adheres slightly to the paper's surface.  This sets your alignment and spacing.



Step 2. Lay your styrene outline, or cross-section, on top of the rods. Use a sharp, single edged razor blade to trim the rods so they fit inside the cross-section; with careful trimming, it should be a nice, snug fit.  Add a dab of liquid glue to the end of each rod to join it to the cross section.  This gives you your finished fin cross-section, complete with spars:


Step 3. Trim out the skin panels for each fin (2x each).  Glue to the fin's skin to the skeleton, then place the assembly under a heavy book until the glue cures - you don't want any warpage!  If you use liquid glue, as the solvent works on your styrene sheet, you'll get a nice, realistic sag around the framing.



Step 4.  Pop the glued assembly off your template.  The skeleton is a delicate assembly, but once the skin is on, it's nice and secure.  You'll probably have to give the exposed framing a light sanding to remove any stray bits of paper or glue:


Step 5.  Glue the remaining skin section to the exposed framing, again placing the assembly under a heavy book while the glue dries.  This will ensure a nice, flat assembly.  Once the glue is cured, you can fill any imperfections and round off the edges.  Also, while you CAN drill or notch holes for some locating pins BEFORE the fin is all sealed up, the finished assembly is actually translucent if you hold it up to a light, so it's just as easy to mark these off later.

[MoFo]

Second can of primer is on.  Well, 2/3 of a can, anyway.

But first... the gun platform.

For self defense, Zeppelins were armed with a number of machine guns; each gondola had a pair of gun stations, and there was an open-air platform on the top of the nose, accessible via a ladder from the front gondola.  I get the willies looking at the pictures of Zeppelins launching, imagining being on that lonely platform 50+ feet up in the air.  I can't even imagine standing on top of that massive, floating balloon at several thousand feet.  If you thought WWII turret gunners had it rough, at least they weren't standing outside.  And had parachutes...

Incidentally, the gun platform just happens to be almost the exact same size as the Sopwith Pup I'll be building along side the Zepp, so again, if you're wondering about how big this thing is, scroll up to the tiny airplane in front of the Humbrol tin, then keep that in mind when you look at the gun platform.

Anyway, my pics of the actual build weren't great, so here are some renders showing the process.

Step 1: Mark off and cut out the required skin sections.  Luckily this falls between along two bulkheads, so it's easy to find the cut lines.


Step 2: Inlay a section of styrene sheet to fill the hole.


Step 3: Realize that you've mixed up the measurements for the platform size (d'oh!), so you have to replace part of the skin.  Not a hard task: I just printed out the relevant section from my templates, chamfered the edges then glued/filled/sanded in place.  Always frustrating to have to fix your own stupid mistakes, though.


Step 4: Cut the platform itself out of styrene sheet, using templates copied from the paper model.  This gave me the overall dimensions of the gun platform, as well as the cross-section pieces which let me align it easily:  aligning a flat piece of plastic card is fiddly; aligning the vertical edges is much simpler.  Just cut out the overall shape, scribe along the fold lines and the styrene folds cleanly.


Step 5:  Fill the gaps at the front with styrene sheet.  Again, the edges were chamfered then the filler pieces glued down and trimmed to size. 


All pretty straightforward.  The only real difficulty came with the flexibility of the styrene, but a healthy squirt of CA underneath makes it more rigid, and less prone to flexing when you sand. 

With the gun platform in place, the whole thing got primered (again).  Which is where it's at now.  Things are looking decent; it definitely needs a wet sanding, but the surface is relatively level.  There are a few spots that need refining though - pinholes, scratches, cracks and glue/putty lines.  Nothing really major (I mean, compared to body-puttying the whole thing!), BUT!  The surface is so large, it's hard to remember where all the surface imperfections are - and easy to miss a few - so I've gone over the entire balloon and used a pencil to circle all the areas that need further attention.  Makes it look a tad spotty at the moment, but it should pay off in the end.


Nose area, showing the areas to be fixed, as well as a view of the gun platform.  You can also get a feel for the 'pillowing' effect on the skin.


Closer view of the nose, with a better view of the faults and platform.  It's not super-critical to get a flawless fit around the front of the platform, as this will actually be getting a small wind shield made from sheet stock, which will cover the area.  Still, there are a few issues to be addressed.


...and a view of the tail, showing more glitches, and probably a better view of the pillowing (though it seems more prominent here than IRL).  This also gives a view of the skeleton: some 5/8 acrylic square tube used to keep all those rib sections aligned properly and rigidly.  Once my nose and tail caps get printed, they'll slot right on to this spine piece.  Theoretically.  I hope...

[MoFo]

Tailplanes test fitted.  Need to tweak the fit to blend them in, but it's a start.  It's *finally* starting to look like an airship, rather than a big cigar.



Note the see-through effect on the tailplanes.  Hopefully I can maintain this through paint.  Hopefully...

[MoFo]

Finished the CAD work on the Spandaus for my Zepp project.  Well, I say finished; I expect these will be too fine to actually print, but I'd rather start with too much detail rather than too little.  The really clunky looking ring sight, for instance, is only .1mm thick (.004")


But wait...  what's that in the barrel, the sharp-eyed readers among you will say.



This is a good illustration of the problem with CAD.  You can zoom in... almost infinitely.  Which makes your detail look thick and clunky.  It's really easy to lose sight of how big a part will actually be, and how all that detail you've lovingly created will be unprintable, or invisible to the naked eye.  Each of those eyes is a mere .008mm (.0003"!) in diameter.  But hey, they're smiley-faced Spandaus, how could I *not*?  />

The really, really NICE thing about CAD is that, after you've spent hours making one model, it takes mere seconds and a few clicks of a mouse to make more.  Enough for the Zeppelin, plus a few extras for good measure:



I believe that, when you're referring to this many of the gun, the correct term is 'a ballet'.



...and now to add it to the stack of bits to be printed.  Next up: engines!

[MoFo]

Still progressing.  Just about ready for the printer:



A string of Maybachs:



Front gondola:



...minus the roof:



Rear gondola:



...missing its roof:



Transmission and gear drives are integral with the gondola drawings - I figure they'll probably be painted a fairly simple overall colour; Maybach's were split out because they'll need more detail painting (plus, they're a lot more detailed than the transmissions, so it was easier to build them separately)  Also visible in the overall pic are the rudders (top, far left), Spandaus, radiators (right above the engines), nose and tail caps, and some doors.  Just need to add steering wheels, engine pods and props and it'll be good to go.  Wheeeee!

[MoFo]

I's dotted.  T's crossed.  Couple of fiddly bits taken care of:



Decided to print the gun platform as well.  Saves a bit of fiddly work (hopefully), and it lets me do the scaffolding structure far more easily.  Some simple sketchwork vs fiddly, tedious trimming and soldering.  Of course, cleanup will be tedious and annoying, so it's a little bit of swings and roundabouts. 



Outrigger gear pods.  These mount outside, on the balloon's surface, and actually drive the props.  The engines themselves go inside the gondolas (they'll mount on the rectangular platforms you can see on the gondola floors), but two engines in the rear gondola connect to gearboxes which power driveshafts that hook up to these outrigger gear pods to power the props.  Nice thing about CAD/3D printing is that it's much easier to get incredibly precise angles.  In this case, I've "drilled" the mounting holes for the outrigger pods, which should make assembly much easier.  Had I turned them on a lathe in a more traditional manner, it would mean a bunch of tricky measuring and drilling (and repairs when I inevitably got it wrong).



Illustrating the 'ship' part of airship, here are the Zepp's wheels.  Multiplied by a few, just in case I damage some in clean-up.  />



...and finally, the props.  I'll only need four, but again, just in case of breakage it's better to have too many than too few.

[MoFo]

Woo hoo, I was finally able to make some progress again.

Still waiting on the printer for my parts (hopefully they'll ship Friday), which had me at pretty much at a standstill.  Luckily, I got a delivery from HLJ today with some brass rod I needed for various supports - .2mm, .4mm and .5mm diameter.  This gave me the chance to give my new Hakko 888D soldering station a good workout, and I have to say, I'm *really* pleased with the results.

I had already drafted out bending soldering templates in CAD.  I printed out the templates and used them both to cut the various pieces to fit and for assembly - a sliver of masking tape to hold the pre-cut brass rods in place over the template, a dab of flux, a tiny sliver of solder and then touch it with the iron.  Simple masking tape works well enough to hold things in place, as long as you don't take too long with the iron.  Ditto the paper templates; if you really try, you can scorch things a bit, but unless you're actively trying to start a fire, it'll be fine.*  It all went surprisingly well, though it felt like I was spending ten minutes trimming and taping two pieces, in order to solder them in a second. 

Since I always seem to start with the least sensible assemblies, I began with the hand-holds, which will be located on the lower portion of the gondolas.  These were used by the ground crew to man-handle the Zeppelins, tie off ropes, etc.  I wanted them to be fairly delicate, so I used .2mm rod (.008").  Delicate work, which required just the tiniest amount of solder, but fairly simple construction.



Next up, the engine pod support trusses.  These were more complicated, having a triangle-inside-a-triangle shape... which gets connected via braces to another copy of same.  Similar construction process, though: tape brass rod over the pattern, trim to size, add flux and solder.  I made 4x 'triangle' bits, then taped two completed assemblies on their sides, fitted the cross bracing and soldered the units together.

One of the cool things about soldering is that by staggering your temperatures, you can safely build on previously built assemblies without fear of melting the join.  Just start with a high-temperature solder and work your way down through lower-temperature solders.  In this case, I started out with regular 60/40 solder with the iron at about 250`C to build various subassemblies, then switched to Tix solder (melts around 145`C) and turned the iron down to 180`C - just below the melting point of the lead solder.



Same process for the engine pod's front brace.  I soldered the "vertical" bars with 60/40 along the length first, then rotated this assembly 90', using a set square, then used Tix to solder on the V-shaped bit.  They do need a bit of clean up, but I'm pleased with the way they look.



And just to give a sense of what exactly these bits are, here's a view of the paper model I'm basing all this on.  You can see the hand-holds along the bottom of the gondola, and the two engine pod support structures attached to the balloon.  I still need to build the transmission shaft and its support braces, but I may wait until I'm attaching the gondolas to do that, since I'll probably need a bit of wiggle room in their location.






*I take no legal responsibility for any fires anyone may start.

[MoFo]

I believe the phrase is "photodump".  />/>/>

Got my prints back from RapidFab.  They use the same kind of printers as Shapeways' Frosted Ultra Detail, but it's a much smaller operation, running higher resolution, and it's cheaper to boot.  I think the prints look MUCH better.  Full gallery is here, for anyone who is interested. http://s21.photobucket.com/user/IronChefMoFo/library/parts/3d/prints2 I'll try to pick out a few highlights.

A couple of notes up front.  You *CAN* see visible print layering, and striations from the print head.  It's not the worst I've ever seen, but it will need cleanup (filler primer + sanding).  Also, because the acrylic resin is translucent, it's a pain to photograph.  It also means you're seeing surface issues on BOTH sides of the part.  Remember that when you're looking at the surfaces.  It's also interesting to note, that because of the rough surface finish, the parts stick to a microfiber cloth like velcro.  Again, nothing that a light sanding won't improve, but they're *not* ready to go straight from the box.



Engines.  Not much to say.  They seem to be mercifully smooth, requiring little clean-up, but it's a little tough to say for certain until they're primed.  You'll notice that they have a slight discolouration at their cores; that's from the support wax (more later).



Ships wheels.  Again, they seem pretty clean, which is lucky since they'll be almost impossible to clean.  If I recall correctly, the connecting points on the spokes are around .3mm.  Also, it's a good illustration of one thing 3D printing could be really, really good at: replacing PE.  Instead of having flat, two-dimensional brass parts, print 3D shapes.  They don't use much material, they're thin, so they'd have fast print times, and they're more realistic.  Interesting thought for the future.



Gun platform.  There's pretty much zero chance I could have scratchbuilt this without resorting to PE.  Now I just need to inset it into the fuselage top.  It almost feels like cheating.  />/>/>



...and the guns.  I'll need to primer these before I can tell how they turned out.  I *can* make out the gas vents, but anything other than that is just too small.  I mean, they're certainly good enough, I'm just not sure how good at the moment.  (this is one of the downsides to the translucency)



Front gondola pieces.  The front control gondola was actually split in half, with the command section separated from the engine section, apparently to avoid the vibrations transferring through.  I decided to mimic this, and split the engine bay off.



Interior details.  Note the square stools - I think they're about 1mm square.  The framing will all have to get glazed over... somehow.  I could make up a vacform master, or just cut panels from acetate.  Leaning towards the latter.



Command section roof, showing the knife edge to the fairing, and some of the print lines, basically just to get a feel for the print texture.



And the engine section's roof, again to show the texture of the print.  You can see print layering on the left side, and a slightly rough surface on top.  The raised lines along the side are meant to be there.  Oh, and note the scoop towards the bottom/front; it's been printed open.  />/>/>



The various parts all just press-fit together.  A couple of dots of CA are all that will be needed.

[MoFo]

Rear gondola and roof.  This one had three engines, so would have been loud!  Again, notice the yellowish tint at the nose...



I forgot to include an escape hole in the model, so the yellow substance is the support wax.  The 3D print head prints out the resin, but it also prints wax to support the model.  That's why you can print layers that would otherwise be floating free in space; in the physical print, they're not, they're printed on top of wax, which gets melted away in post processing leaving your free-floating part.  At least, it does as long as there's a way for the wax to flow out.  I'll probably drill a few small holes and heat the model up to empty the wax out, just in case it causes problems in the future.



Speaking of free-floating, notice the door.  I gave it a .1mm gap around the edges, leaving small tabs attaching it at the top and bottom.  A couple of quick swipes of a pico saw and it's free.



Rudders.  These warped slightly, but they're *very* thin at the edges.  I used a few blocks and spacers to hold the parts together through shipping.  Also, note the faint line through the fins, running roughly across their middles...



Those are printed-in holes for the rudder hinge rods.  They just needed to be lightly reamed out with a .5mm drill bit, then slid onto some brass rod.  That should add some strength to a relatively delicate structure.  The rudder cores themselves will get skinned in thin sheet styrene, then the brass rod fill slot into holes in the body and tailplanes; I opted to print them largely because it was easier to obtain the proper airfoil cross section that way, rather than through careful, tedious sanding.



And finally, the nose and tail caps.  These are way more precise than I could have managed, carefully filing and sanding styrene sheet.  And they're sized to simply slide over my acrylic rod spine.  It's the first time I've had a fully, complete envelope.  I'll be using putty to fair them in and refine my facets.  The down side is, I won't be able to 'rotisserie' my balloon for painting any more.  Unless I make them removable...



Finally, another shot showing texture on the nose cap.  You can clearly see the (nice, crisp) facets running sort of like longitude around the dome.  If you look closely along the 'latitude', you can also see facets introduced when the model was converted from CAD to a 3D printable file format.  This converts shapes into polygons (triangles), so, for instance, a nice, smooth sphere becomes a lumpy geodesic dome.  In this case, the smooth arc of the dome became a just-barely  visible series of flat facets.  Kinda neat.

Now I just need to give everything a thorough cleaning to remove all traces of wax and mineral oil, then shoot a coat of primer to see what I've *really* got.