Author Topic: I've made a terrible mistake: 1/144 Hindenburg scratchbuild  (Read 2364 times)

Offline MoFo

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I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« on: April 15, 2022, 03:45:19 AM »
I was asked about this elsewhere, so figured I'd re-post this from another forum.  The thread dates to Apriol 2018, so the build is now on its 4th anniversary, with no end in sight.  :)  Things kinda snowballed.  I'm currently stalled with the glazing and debating using hand cut slide glass because I've convinced myself that'd be a great idea.   :o

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I bought an FDM printer last year, specifically with an eye to doing some more airships in the future.  Well, I found some sweet-butt drawings of the Hindenburg a while back, and spent some time on it over the weekend.



The problem is, apart from punching the basic dimensions into Solidworks and having a general feel for the size, it never really sunk in just how big it would *actually* be in 1/144. I knew it would be about double the size of the Q-Class Zepp I'm building.  I knew it would be noticeably longer.  And I knew that as a result, it would be a more massive object.  But I’ve been too focused on modelling it in CAD to really step back and understand the full scope of the beast.



Just now, I plopped a model of my existing Zeppelin next to it to render a comparison and was like, ha ha ha, it really IS bi.... oh, crap... maybe I should get a tape measure.


It’s 5’ 7” long and 12” in diameter.  Gulp.  Having some serious second thoughts right now.  The thought of sanding and painting something that big is terrifying.  I have no idea where I'd even put it.  And I've got half a dozen once-in-a-lifetime-type builds in the queue as it is.  But dang... it would be pretty awesome.



Still, I'm pretty pleased with the way the CAD is progressing:


Offline MoFo

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #1 on: April 15, 2022, 03:48:18 AM »
Some updates:



I've revised the tailplanes and have split both them and the gondola off of the main envelope.  They'll be printed as separate parts and should(!) just tack on later.  The tailplanes were actually pretty much completely re-done - I wanted to tweak the geometry of the upper and side planes (which are all the same), and then created the lower tailplane (which is different).



I'm still debating whether I should add surface details to the parts.  The skin is basically smooth, with just a subtle colour difference from the structure visible, and smooth parts will be easier to print and finish, but because they're such large pieces (each tailplane is almost a foot long) it needs some detail to break up the large expanse.



(...and looking at this pic, I see a few more things I need to tweak!)





I've also started roughing out the engine gondolas.  These have clamshell shutters at the front, to regulate airflow to the radiators.  I'm *really* tempted to engineer some kind of functional solution for that...




And lastly, now that the gondola is split off, I can begin detailing the interior.  Complete with easter egg.



Offline MoFo

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #2 on: April 15, 2022, 03:50:37 AM »
Started adding windows; revised the tail planes yet again:



Full view along the bottom, showing both updates.  It's quite busy underneath, actually.  There are also a number of cargo hatches, but I'm probably not going to add those to the CAD - FDM printers don't do fine recessed details well, so it will be easier to either scribe the doors, or add some sections of decal film as 'raised' panels.




And a view with the engine pods in place:







Next it needs reinforcing strips along the envelope, and some subtle scalloping to the facets.  And locating points for the vents up top.

Offline MoFo

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #3 on: April 15, 2022, 03:55:37 AM »
To give a sense of scale, here are a trio of test prints I ran, all at 1/1000.



On the bottom is a WWI-era Q-class Zeppelin - the one that I scratchbuilt previously - which was already massive in 1/144.

Above that is an R-class WWI Zeppelin.  These were the first of the 'Super Zeppelins', larger and more aerodynamic so they could carry a heavier payload (nearly as much as a B-52), higher, in an attempt to avoid British air defences.

On top is the Hindenburg.  It almost looks like a different scale.

 

Extrapolating that to the 1/144 version, I've also run test prints of the gondola and engine pod.  They look tiny in the CAD renders, but will be quite substantial on the actual model:



Again, these are being produced on an FDM printer - the simplest, cheapest, but crudest of all 3D printing technologies.  When you read about Makerbot, or the Dremel Idea Builder, or just general 'hobbyist' 3D printing, it is an FDM printer.  They work sort of like a cross between a computer-controlled Etch-a-Sketch and a glorified hot glue gun, using motors to precisely extrude layers of plastic on top of each other, to create a finished product.  The up side is that they're relatively inexpensive to build and run, relatively simple to operate, and relatively fast to print, but the down side is that they're poor at reproducing really fine details, so the're ill-suited for most modelling purposes.  An FDM printer will work well for a Zeppelin because it's basically a big, smooth shape; if it was full of panel lines and fine surface details, they would look terrible.  I'll be using this printer to produce the Zeppelin's envelope - the balloon itself - but detail parts like the gondola and engine pods will be run on a different kind of printer than can render finer detail.

 


These parts were run at .04mm layer height, which is *extremely* fine for an FDM printer (it's about half the thickness of a sheet of paper), and has generally resulted in nice, smooth layers.  However, you can still clearly see the stepped-look on shallow angled places like the bottom of the gondola. 




However steeper, more vertical angles look pretty good.  Fortunately, most of the final prints will be steep angles, like this.  A quick sanding and a heavy coat of primer and the parts should be smooth.  This is ultimately why I bought the printer in the first place - it was a ton of work filling and sanding my previous Zeppelin, and the parts weren't as crisp as I would have liked.  If I can get a sharper, more precise balloon with less surface prep, I'll be thrilled.

 


I was actually pleasantly surprised with the fidelity on the engine pod - you can see the slightly recessed clamshell doors on the front.  Not perfect, and not as detailed as I'd like, but if I was going for a simpler display piece rather than tons of internal detail, it would actually be usable.




Lastly, something that interests a lot of people...  FDM prints are rarely *solid*.  There are a bunch of reasons for this - it's much faster since you're printing far fewer lines with each layer, and it saves an enormous amount of material; plus the finished parts are still more than strong enough.  So the software used to generate the code that drives the actual printer - it converts your 3D object into individual layers and plots the movements and settings for each layer - can also 'scoop out' the inside of each file and generate a honeycomb-like 'infill' to maintain rigidity.  Hence, this grid-like pattern visible on the bottom (or, top) of the gondola.  The printer itself isn't actually all that complex or sophisticated, it's the software that runs it that's smart!

Side note about the fact that most FDM prints aren't solid...  I just imported one of the envelope sections into the print software to see how long it would print if it was solid.

 

209 days, 10 hours and 55 minutes.  Yikes!  If I did the whole thing as 100% solid prints, it'd take 748 days and weigh 90kg (about 200lbs).  Yet another reason why 3D printers aren't the magic machines most people think they are.

Offline MoFo

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #4 on: April 15, 2022, 04:02:29 AM »


I made a thing!



Started printing with the (top) rudder/tailplane.  It's... pretty massive.






It's actually a 12-piece assembly.  Because the rudder hinges hang way out into thin air, they would require support material to print, which would have given a poor finish. 







To get around this, I split them off to print separately, and included locating holes for hypo-tubing pins which would let me accurately and securely join the parts.  Strength being important, because the rudder is poseable - it's printed with a tube inside, so I can feed a length of hypo tubing through the rudder, capturing the hinges.  Which illustrates yet again that, while many people think of 3D printing as a magic bullet, click-print-and-get-perfect-parts, the reality is far away from that ideal...





So just how big is it?  Well it's hard to get a feeling for how *massive* it is in photos - it's more than an inch thick, but here are a few comparisons.



1/48 F-15 tailplane:

 



1/48 -109 rudder:





(the Hindenburg's rudder would be more than a foot tall in 1/48!  kinda tempted to print one just for giggles )



and for something in-scale, a 1/144 P-51:





The Mustang fuselage would *easily* fit inside the rudder, let alone the main tailplane.




Offline MoFo

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #5 on: April 15, 2022, 04:06:52 AM »
​I've been picking away at this, slowly but surely.  Last summer was spent on the electronics - apparently it's not enough of a challenge to design an build a 6' long model kit, I also had to add lights, sound and motion.  I believe they call that 'mission creep'.  😞 

 

 

 

So...  a basic schematic of the electronics inside. 

 

 

 

And focusing on the lights and motors.  It's been simplified to not show every single LED and switch - I'm running each section on its own switch: corridoors, spotlight, nav lights/beacons, passenger deck, crew deck, etc.    Each individual engine will also function, working off its own switch, because... why not.  😄  Lights are a mix of sources: LED strip lights for the corridoor (which will be roofed in and get a few exra details), an array of 3mm LED bulbs for the spotlight, discrete SMD LEDs for the position lights and passenger areas, etc.  All are warm white, to be closer to incandescent.

 

The motors are 3mm diameter pager motors - tiny, but they'll slide in to the 1/144 Maybachs in each gondola - run through a potentiometer so the throttle can be 'tweaked'.  Mostly so I can adjust it to something suitable rather than just rely on the motors OOB, but I'm sure some viewers will also want to play with them. The motors and nav lights on the gondolas posed a big challenge: how to come up with a secure but fine electrical connection so I can plug the pre-wired gondolas into the pre-wired balloon during final assembly, after everything is painted and ready?  My solution was fine brass rod and tubing - .2mm rod (which will simulate plumbing in the gondola) was soldered to the LEDs and motors, and will slot into .4mm brass tubing, which was soldered to my wiring harness and will serve as the struts supporting the gondola.  The rod has a slight ( shaped bend to ensure a snug connection inside the tubing.  Lastly, a 3D printed block inside the balloon has holes bored at the various correct angles to ensure everything slots correctly into place (I hope...)

 

The audio side was a little more straightforward in terms of planning the layout, I just had to figure out the implementation.

 

  

 

The heart of the system is that little PCB in the middle - the DFPlayer Mini.  It's basically a tiny (1" square), cheap ($2) MP3 player that you can program to function in a bunch of different ways.  I went for the simplest option: each button runs through a resistor, and each resistor value is mapped to a specific function in the player; when it detects the signal from a button press, the it checks the voltage (determined by the resistor value) and does that particular function.  In this case, it's to play a specific audio track (yes, including that one...).  Or, TL;DR, you press a button and it plays a sound.  🙂  And again, the speaker's output runs through a potentiometer for volume control - which actually WILL be useful.

 

...and it's all been set up to run on a 5V power supply, so either a simple phone charger + USB cable, or a 5V wall transformer, or even a powerbank, if I need the portability (if it ever goes to a contest)

 

Next up: the actual wiring (it's ugly, but it works!)


Offline MoFo

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #6 on: April 15, 2022, 04:10:21 AM »

So, the 'for real' electronics, now, starting with the spotlight, 'cause it looks cool.  🙂  I've seen diagrams that show a simple, single spot style, and some that are more like an 'array'.  Not sure which one I'll end up using in the end, but I'm thoroughly pleased with how the array style turned out - the LEDs are all a nice, snug fit inside, all angled and aimed at the same point:

 




So the heart of the electronics is a chunk of protoboard PCB, which I've built the circuits off of for strength and stability - it's basically your standard fibreglass circuit board material, with standard spaced holes for attaching components.  The DFPlayer is to the left (well, centre in the pic, really); power connects on the left side of the board; individual components/circuits plug in via pin headers for tidyness, and the aforementioned row of resistors is to the right. 



 

...and with the buttons in place.  Each of these triggers a different audio file - a couple of tracks with ambient noise, a couple of period news reports, of the Hindenburg crash, a couple of pre-crash recordings, and a couple of interviews with survivors.

 

 

 

The switches for the individual lights/motors get installed via pin-headers on the obverse of this board, but that's harder to photograph because they're also attached to:

 

 

 

The support posts!  Okay, difficult to get excited about, but this was one of the weirdly challenging problems to solve.  I wanted the supports to look relatively fine and delicate (no brass plinths or pedestals), be fairly tall, and to house all the wires for a clean finished appearance.  So, okay, some sort of rigid tube... like carbon fibre.  And the more I worked on it, the more I realized that it would be a really, really good idea if I made them removeable, so I could troubleshoot, and didn't have to have the model permanently attached to the base (kinda obvious, really...)  So the challenge became, how do I get a strong and secure, yet easy to remove attachment between the posts and the guts, and how do I make it small enough to not have a gaping hole in the bottom of the balloon?  I thought of a number of possibilities, from micro HDMI connectors (too big and too sticky) to pogo pins (too finnicky and delicate), and ended up deciding on a custom shaped block of pin headers (this is what actually started me on the pin headers as a connection).  I glued 3 lengths of 3 pins to a section of PCB, epoxied it into a length of CF tubing, then ground it to shape so that it slots into a larger tube.

 

 

 

Something like this.  The 9 pins give a nice, secure fit that slots in fairly easily and comes out with a slight tug, but won't pop out accidentally.  And there's zero chance of crossing connections and shorting things out.  The other half of the equation was just as important, both providing a secure, precise locating hole (the one in my other Zepp is a little imprecise) AND being able to support the weight of the finished model on a handful of electrical connections.

 



 

My solution here was to print out a support brace (black) to hold a length of CF tubing in place on my aluminum spine.  Another printed part (white) spans the gap between this locating tube and the envelope, which helps bulk it up and add stiffness.  My CF support tube slots through this locating tube for a nice, precise, 90` fit.  I then drilled and filed through the aluminum spine so that the support post can connect with the other half of the header block, which was soldered onto a strip of proto board (for rigidity), and then bolted down with some large diameter washers, so that it's held firmly in place with no way to bow, flex or shift.  Lastly, I glopped a bunch of hot melt glue on the wiring around this internal connection to act as strain relief, and some additional insurance against things popping apart in the future - I really don't want to have to hack this open to repair a simple solder joint!

 

 

 

Net result being, a simple connection between the support posts and internals, giving me exactly the kind of fit I'd wanted.

 

And here's another view of the assembly.  Funny how much engineering it takes to make 'simple':

 

 

 

Apart from that, it was a relatively simple matter of measuring out lengths and distances, then wiring up the various components.  It looks rather messy inside: 

 

 

 

but hopefully this gives a feeling for how it all works.  And might help someone else planning on wiring up their own model.

 



Offline Dirigible-Al

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #7 on: April 15, 2022, 05:59:12 AM »
Just think, when this is built you could take on R101 to go with it!
Alan.
I heard that it all started when a bloke called Archie Duke shot an ostrich 'cause he was hungry!

Offline MoFo

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #8 on: April 15, 2022, 06:17:11 AM »
Please don't give me ideas.  :D

Offline MoFo

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #9 on: April 15, 2022, 06:22:50 AM »

Interior.  

 

The Hindenburg had two main decks inside the envelope.  The upper had passenger accommodations, while the lower was a mix of passenger and crew amenities. 

 

Starting with the lower deck, from port, looking aft...  I seem to have screwed up my dimensions, as the hallway is too narrow, but NBD.  Up front (bottom) is the captain's table.  Aft of that is the kitchen, then crew dining area, lav and stairs leading to the second (upper) deck.

 

 
 

On the other side, from right to left, we have the smoking room (yes, it had a smoking room; it was pressurized to keep all hydrogen out, and had an electric lighter, like a car).  Moving left, the area with the round bit is the bar; the rounded section is an airlock to the smoking room, to keep it pressurized, and above that is the purser's cabin.  Further left are passenger lavatories, and then the other set of stairs.

 

 

The upper decks were simpler.  Passenger cabins down the middle (which I didn't bother modelling), with open areas on the outer sides.  Running along the edges on either side was a long promenade, with seating to look outside.  Inboard of this was the dining area on the port side:

 

 

...while the starboard side had a lounge and writing area:

 

 

So that's the basic layout.  I kind of went nuts on details because, well, CAD is fun.  🙂

 



Full bar top and purser's cabin, complete with pillow and locker.  Also note the burners in the kitchen.

 



Crew seating (quite pleased with the upholstered look) and washroom visible in the background.

 

 

Right down to the passenger toilets (lids closed)

   

 

So, how much of it is visible?  Pretty much none of it.  Literally.  You can get a bit of a view of the second deck if you crane your neck juuuust right:



 

But the lower deck is completely invisible, entirely obscured by the vertical walls around the edges.  Just the barest hint of ceiling is visible:



 

(which kind of makes me laugh, TBH)

 

Pointless modelling is best modelling!  😄 


Offline MoFo

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #10 on: April 15, 2022, 06:48:29 AM »
And some miscellany.  I realized reposting these that I hadn't actually posted any pictures of the envelope.  It's kind of hard to get a feel for the ridiculousness of the whole thing from renders or even a few workbench photos.  So here it is in front of a door:



It completely dwarfs the war-time Zeppelins.  You could fit a couple of the Q class airships INSIDE the Hindenburg.



Comparing tails...



...and doing a spot of priming in the garage, because obviously it's a bit of a snug fit in the spray booth:



That's a full sized can of spray paint, BTW.  And the items in front of the envelope are the interior 'roof' - the bottom of the actual gas cells - which serve to avoid the black hole look that a fully open interior would have.  Basically fancy, CAD designed, 3D printed blanking plates.



Regarding the interior lighting, I've used LED strip lights, soldered in sections.  I had to use a bunch of connectors so I could attach them to each section of the envelope, then connect the sections together.  Feels a bit like keyhole surgery at times, and I'm terrified something will come loose after its all sealed up, so they're both self-adhesive-ed and hot glued in place.  Not pretty, but it's not visible, either.  I'll crank down the juice to dim these (and give a longer life)

And lastly, the motors.  I've soldered the wires to some brass rod, which slots inside some telescoping tubing.  The rod has a slight ~ shape to make sure there's a decent electrical connection.  This way I can complete the engines separately and simply slot them into place; the tubing is wired up and buried inside the envelope, and the rod will jut out of the engine pods, so the theory is, the rod will serve as the mounting frame, slotting into the tubing and completing the connection.  Fingers crossed...

Offline KiwiZac

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #11 on: April 15, 2022, 11:08:24 AM »
This is even more remarkable than the straightforward airframe build I imagined - simply incredible!! I love the sound module idea, especially how you're making it a "living history" piece with the survivors' interviews. Absolutely brilliant all around. And a good illustration on how FDM printers are suited for different projects.

I told my wife about this, including the measurements. She said "But I'm 5'8"!" and I said "Five. Nine." I found an Academy-Minicraft 1/144 DC-3 and showed it to her, explaining it was the same scale. She said "NOPE!" and drove away to her aunt's.


The fact she was already planning on making the trip is beside the point but is convenient for comedic purposes. ;D

Offline MoFo

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #12 on: April 15, 2022, 01:16:02 PM »
LOL.  Yeah, it's ridiculous.

One other thing worth mentioning, from the time I started it until now...  I've coated the entire airframe with a heavy coat of UV cured resin, from my resin printer.  It's like a thick primer coat that fills in all the striations of the FDM print, but cures the second you take it out in the sun.  It has saved a TON of money on primer, and time on bondo and sanding - it will still need smoothed out, but its fairly close as it is. And the material sands really nicely.

It's actually a really handy modelling material, the UV cured resin.  It would be great for filling panel lines and tricky gaps - spread it on, smooth it out, minimal sanding to finish.  If you need to build up a heavy mass, just brush it on, zap with light and repeat as needed.  It's amazingly handy having something that remains completely fluid, right up until the second you decide to cure it.

Offline Rookie

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #13 on: April 16, 2022, 02:16:59 AM »

"....The thought of sanding and painting something that big is terrifying.  I have no idea where I'd even put it. 

.....

But dang... it would be pretty awesome...."


I know exactly what you mean...

Willem

Offline KiwiZac

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Re: I've made a terrible mistake: 1/144 Hindenburg scratchbuild
« Reply #14 on: April 16, 2022, 06:29:31 AM »
One other thing worth mentioning, from the time I started it until now...  I've coated the entire airframe with a heavy coat of UV cured resin, from my resin printer.  It's like a thick primer coat that fills in all the striations of the FDM print, but cures the second you take it out in the sun.  It has saved a TON of money on primer, and time on bondo and sanding - it will still need smoothed out, but its fairly close as it is. And the material sands really nicely.
That sounds exactly like what I need to finally get back to this.