A Type VIIC at 1.49 mm to the metre

The Atlantic boat ran 67.1 m from stem to rudder. This one is 3.9 × 1.1 × 1.2 in on the shelf, in 3 printed pieces — and every detail on it had to get past a 0.4 mm nozzle before it was allowed to exist.

The printed submarine on its cradle: an orange bow and conning tower, a purple stern, a green stand, all showing print layer lines.

Scale: 1 : 671
On the shelf: 3.9 × 1.1 × 1.2 in
Weight: 9.5 g
Printed in: PETG
Pieces: 3

On station

67.1 m of Kriegsmarine Type VIIC, drawn at 1.49 mm to the metre and printed 100 mm long, keel to cradle.

Deck

The flat casing, the 8.8 cm deck gun and a dashed row of flood slots on 1.66 mm centres — what a 0.4 mm nozzle can still hold at this size.

Lift

It leaves the cradle straight up. Each trough is the hull's own section at that station, opened out by 1.3 mm, so there is no other way out of it.

Split

The hull opens at x = 60 mm. The loft was cut there after it was drawn, so the two faces are the same section by construction.

Pegs

Two 2 mm pegs on a 4.4 mm baseline, standing 4 mm proud of the seam, entering bores 4.6 mm deep.

Home

Pushed home and set back in the cradle: 3.9 × 1.1 × 1.2 in of Atlantic boat, 9.5 g in the hand.

What a 0.4 mm nozzle lets you keep

Divide a 67.1 m boat by 671 and most of it stops existing. A railing stanchion arrives about 0.022 mm across, 18 times finer than the nozzle can draw. So every feature on this deck is one of three things: at scale, fattened until it prints, or left off.

Fattening is the honest compromise, and it is worth knowing which details are wearing it. A periscope at true scale would be 0.3 mm; drawn at 0.8 mm it comes out as two solid perimeters instead of a smear. The propeller blades were never going to survive, so the shafts end in fluted hubs 1.8 mm across and the model does not pretend otherwise.

Everything the table doesn't name is at scale — including the shape that makes a Type VIIC read as one from across a room: a wide flat casing riding a hull whose flanks swell out over the saddle tanks.

Close view of the conning tower: two periscope masts, the stepped Wintergarten behind them, the deck gun forward and a dashed row of flood slots along the flank. — Two periscopes at 0.8 mm, the gun barrel at 1 mm, and the flood slots as a dashed row rather than the openings they stand for.

Five details, measured against the nozzle. The dashed line is 0.4 mm.
Detail	At true scale	As printed
Flood slots	0.15 mm	0.8 mm openings
Periscopes	0.3 mm	0.8 mm — 2.7×
Dive planes	0.22 mm	0.8 mm plates
Propeller blades	0.15 mm	fluted hubs, 1.8 mm
Railings, antenna	0.022 mm	left off

as printed the same detail at 1 : 671 the nozzle, 0.4 mm

It comes apart at midship

The seam is at x = 60 mm, and it was cut after the hull was lofted rather than drawn as two halves that meet. The bow's face and the stern's face are therefore the same section by construction, not because two numbers agree.

A single round peg would let the deck twist, so there are 2 of them, 4.4 mm apart. Each is 2 mm across and stands 4 mm proud of the seam, with another 1 mm buried inside the stern so the peg is a real intersection with the hull and not a coplanar kiss. They land in 2.4 mm bores 4.6 mm deep: 0.2 mm of clearance a side, and 0.6 mm of relief at the bottom so the two faces meet before the peg ends do.

The clearance is deliberately generous. Those bores are horizontal, and a horizontal bore droops where it bridges; a tighter fit binds before it seats. Glue on the seam face does the holding — the pegs only decide where it holds.

Peg: ⌀ 2 mm × 4 mm proud
Socket: ⌀ 2.4 mm × 4.6 mm deep
Fit: 0.2 mm a side, slip
Anti-roll baseline: 4.4 mm
Assembly: axial push, no undercut

The hull held open at the seam: the orange bow's flat face carries two bores, and the purple stern's two pegs point straight at them. — The bow's face carries the 2 bores; the stern carries the pegs. Held apart here, the gap is the only thing between them.

The green stand alone: a flat base plate carrying two X-frames, each with a curved trough cut into its top. — Both troughs are the hull's own section, taken at the station the frame stands at and opened out by 1.3 mm.

Two X-frames and a base

The cradle prints as one piece: a 50 × 28 mm plate 3 mm thick, with an X-frame at station 33 and another at 67, each 4.5 mm thick along the hull. Straight arms alone would have grazed the saddle-tank bulge, so the top of each X is troughed with the hull section it has to hold.

That is also where most of the plastic goes. The two hull halves together come to 5.2 cm³ of solid; the cradle under them is 5.7 cm³, which is the price of a boat that sits at the angle it was drawn at rather than rolling onto its deck gun.

The three printed pieces apart: the orange bow with its conning tower, the purple stern, and the green cradle standing on the bench below them. — Everything that comes out of the printer: bow, stern, cradle.

On the plate

The plate holds 3 pieces, printed keel-down with the long axis along the bed. 5 tree supports carry the gun muzzle and the dive planes; the hull itself needs none, because the keel is shaved flat at z = 0 and sits on a 1.97 mm land at midship.

The 0.8 mm rudder is the thinnest thing on the boat and it is loaded across the layer lines. Pick the model up by the hull, not by the fin.

Bow: Stem to midship: casing, 8.8 cm gun, conning tower, bow planes, and the 2 sockets.
Stern: Afterdeck to rudder: shafts, hubs, stern planes, and the 2 pegs.
Cradle: One 50 × 28 mm plate and two troughed X-frames.

1 : 671 is not a modeller's round number. It is what 67.1 m becomes when the boat has to be 100 mm long — and it lands within 4% of 1 : 700 waterline scale, so it stands beside those kits without looking wrong.

Overall, on the shelf: 3.9 × 1.1 × 1.2 in
Weight: 9.5 g
Material: PETG
Printed pieces: 3
Time on the plate: 70 minutes
Hull, keel to deck: 9.39 mm
Beam over the saddle tanks: 9.38 mm
Scale: 1 : 671 (1.49 mm to the metre)