But First a Cold War Joke and after much laughing we will talk Datum Line:
In case your under 30, let me introduce myself, I'm Oscar Goldman and I'm scratchbuilding a DMB-87 in quarter inch scale. The "Snuka" is from the hit Japanese television show SPACE BATTLESHIP YAMAMMAMOMOTO 2199. (I always have to stop and think if its "Yamato" or Yamamoto", it's an occidental thing).
The orthographic plans are brought into Illy and carefully sized. I've been down this road before, so I am very careful to get everything properly scaled and all the layers with various views properly labeled. At some point you will end up with a lot of layers and they will all look the same. I know this is really dull and I sound like your mom. Fine. Make a mess, see if I care.
Here is a print out on 8 1/2x 11 paper, the lines are so I can cut the pages and register them. I end up printing out a lot of pages as I go along, doing it on standard sized cheap paper works well. The "Marquette" is made from foam core and is just a mental exercise to wrap my head head around how I'm going to build this thing. This ship has a lot of complex curves that all meet up in odd places. The wings and landing gear are pretty straight forward, they basically hang off the fuselage. The fuselage, however, has a lot of stuff: two frontal jowl rocket pods, chin scoop, cockpit, turret, six wing connections and two engines tucked underneath. There are flairs and bulges everywhere, a metal clad exhaust housing past the engine nozzles. The fuse terminates in a twin micro boom...
This is one of the reference pics, showing all the beautiful brain auguring complexity. When I'm looking at this I am trying to see how all the components are going to be located and hung off an imaginary datum line that runs through the design core. Sure, I could just whip out some oven baked clay and make a pattern, but how do all these remain symmetrical...proportional...straight... Believe it or not, this is fun for me. I'd rather make a Rubrics puzzle than solve one.
Here is an indication of what's going on inside my tiny brain. Everything relates to the fuselage, the core of the model. I draw a line that runs through the center, usually I refer to it as the "center line" or "zero line", the correct term is
datum line.
Datum line: (engineering) A line which serves as a reference or base for the measurement of other quantities.
If this were a "studio" style model, the datum line usually doubles as the metal support armature. This model falls into the hobby kit world so will be created sans metal support armature. It's only 18 inches long, so we don't need to go crazy here anyway.
(However, I am intending to cast in hard points of brass tubing as support so the model will not sag over time). Back to this illustration.
Forget the surface detail, it's a distraction. Instead, think about the sub-assemblies. On the nose are two jowl rocket pods
(see lines A and B, above). All that matters is how they get located onto the fuselage. Again, if you look at the animation pic from the show (above) do not be dazzled by the surface detail. Mentally break down the overall housing, the interior honeycomb holding the rockets, the forward rib extension and the lip around the opening. Now, imagine each part as emerging from a simple block of material. These blocks in turn are located to the fuselage via the datum line running through it's core.
From the start I'm thinking about the construction method of how this thing will get made. I can carve patterns from wood and vacu-form them to make shells. I can build up the under-structure using bulkheads and fill in the curved surfaces with epoxy. I can carve the whole thing out of styrene blocks. There are pros and cons to each. Vacu-forming will yield beautiful curved surfaces, but getting the parting line on this model will be challenging. Vacu-forms also shrink. It's also harder to nail the datum locators on the resulting shell. I seriously consider epoxy, but I'm worried about getting an even surface. Its also unclear if I can scribe panel lines. I settle on the styrene blocks. The thickest styrene I have is 1/4 inch, so multiple layers will have to be laminated together to get my shapes. However, these slabs will also serve as datum points for building. Styrene has the advantage of being easy to work with and the surface will accept detail lovingly. These drawings are meant to show how I think about the building inside out. The cockpit space is thought of as a void that will be walled around with styrene blocks. In block form centers can be located along the datum line, holes drilled to locate sub-assemblies and so on. The most complex part of this model are the engines. We will get to the details of this later, when it makes more sense.
I know enough bla bla and let's get building! Here are two slabs of 1/4 inch styrene, rough cut that will become the basis of the fuselage.
They are glued together with CA (super glue) instead of Weld-on liquid bonding solvent. This stuff can curl parts when it dries and shrinks.
This is a horizontal slice of the fuselage. I cut out half a top view template and draw a slightly over sized outline using the center line. This is a visual reference only at this point, a sort of high altitude map.
Using screws, I then attach a strip of MDF on the bottom on center. This will be a handle of sorts, a reference to center when I put this into the mill to create the actual center line.
Of course, using the "mill" these days is like using carbon paper or a dial telephone, everything is spit out at the touch of a button by printers. The MDF rail on the bottom (clamped into the vice) will define the center line. This makes things easier as I go back to locate various elements.
Find center, zero it out, use the mill bit to cut both sides the same from center.
Join me next time as we get all transcendental and create the void.
