# The rivets are the constant; the plates are not

> Rivet spacing on a hull is a strength calculation and never varies. The plate courses they hold drift with the curve of the hull, and that mismatch is what makes the print read as steel.

August 19, 2026 · https://justog.club/stories/hull-plating-rivets

Steel hull plates, overlapping in courses that run slightly off the horizontal, each one edged
with a row of rivet heads spaced exactly as far apart as the last. One plate carries a stencilled
mark: a bar, and beside it, the figure 4.

The rivets never drift. The plates do.

## What is actually printed here?

A repeating surface where one measurement is fixed and another isn't.

Rivet spacing on a steel hull is set by a strength calculation — how much load each rivet carries —
and it doesn't change from plate to plate. The courses of plating do drift, because they're
following the curve of a hull rather than a straight line, so the rows lean and shift against each
other even while every rivet in every row sits exactly its measured distance from the next.

## Why does a fixed rivet spacing matter more than it looks like it should?

Because it's the one number on the whole surface that isn't there for shape.

Everything else about a hull's plating — the width of a plate, the angle a course runs at, how much
one plate overlaps the next — is decided by the curve of the ship and how the yard chose to fair it.
Rivet spacing is decided by load alone, which is why it stays constant even as the plates around it
change size and angle — [the same logic that spreads a splice's load over several tucks instead of
concentrating it at a knot](/stories/rope-splice-cutaway). A pattern with one truly fixed
measurement in it reads as engineering rather than as decoration, even to somebody who couldn't say
why.

## Why do the plate courses run diagonally instead of level?

Because a hull curves, and a course of flat plate can only approximate a curve by leaning.

Each course is fair for a short run and then has to correct, which shows up as a slight, constant
drift rather than a level grid. Drawn dead level, the same plates would look like tile on a wall
instead of skin on a hull — the diagonal is what tells the eye there's a curved volume behind the
surface.

## What makes a good plating print rather than a busy one?

Keeping the rivet spacing visually constant even where the plate size changes around it.

That's the one relationship the whole pattern depends on, and it's also the easiest thing to lose
at chest scale — crowd the rivets on a narrower plate and the eye reads inconsistency where there
should be a fixed rule. The plates are allowed to vary. The rivets are not.

## Can I put a real shipyard's plate mark on it?

Not a specific yard's stamp without their permission, though a hull's construction is nobody's
property to license.

Rivets and plating are a shipbuilding method, not a design. A yard's own builder's plate, or a
classification society's stamp certifying the work, is different — that's a specific document a
real organisation issues, and it functions as a claim rather than a decoration, which is the one
kind of mark that isn't simply available to print.

## What does the draught mark on the one plate actually indicate?

Where the waterline sits against the hull, painted where it can be read from alongside, not from a
chart.

A draught mark is a set of figures stencilled up the bow at a fixed interval, each one sized so it
also works as a rule — measure between two marks and there's a distance, without needing anything
else aboard. The single figure 4 here is one reading off that scale, not a claim about how deep any
particular vessel sits; the mark is [a stencilled reading, in the same way a crane's rated load is
painted on the jib for the person standing underneath it](/stories/harbour-crane-diagonal)
rather than filed in an office.

### Why only one figure rather than the whole scale?

At chest size a full run of stencilled figures would compete with the plating instead of sitting
inside it. One mark, on one plate, says the scale exists without turning the print into a
measuring instrument someone's expected to read at a distance.

## How is this different from the shirt built around fish scales?

Both are tiled surfaces where the pattern is doing double duty as an object, but the regularity
sits in opposite places.

[Fish scales grade smoothly from large to small](/stories/fish-scale-blackwork) with no line at
all — the whole surface changes together. Hull plating is the reverse: the rivets hold one constant
measurement while the plates around them shift and lean. One surface is consistent everywhere; this
one is consistent in exactly one place and nowhere else.

## Does it print well?

Yes, and it's built for the flat, slightly imperfect edge a riso print gives.

Charcoal ink on rust red keeps the whole thing to one colour beyond the shirt, with the rivet heads
as small solid dots rather than rings — a ring that size fills in on fabric and stops reading as a
rivet at all. The plate outlines want a visibly firmer line than the rivets, so the eye can still
sort structure from fastening once everything's reduced to two weights of the same ink.

## How do I get one made?

Describe the plating at [JustOG](/) — how many courses, and whether a draught mark sits on one of
them. Pick a direction, drag the crop frame, see it composited on the real garment, and it's made
to order and shipped.

Designs other people have published are in the [shop](/shop).

Every rivet on the shirt sits the same distance from its neighbour. Not one plate does.