Robert Schieck wrote:

So fess up, what do you print your 56" rib out on ?

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Regular typing paper :-)

Select a new LAYER called 'Grid' and draw a grid atop the finished
drawing. I used a 2" square and selected THIN pale blue lines, printed
the rib 1:1, which took 6 sheets, then glued them together aligned on
the blue lines.

If you don't have a light-table, attach a small weight to a length of
black thread and tape it to the OUTSIDE of a picture window or sliding
glass door. Gravity does its thang and the black line of the thread
becomes your vertical alignment guide, easily visible through the paper
when in contact with the INSIDE of the glass. The regular (ie, black)
lines of the drawing are clearly visible and each sheet is fairly easy
to align in the horizontal plane. But for maximum precision, you may
print TWO copies of the drawing and OVERLAP the sheets, using the blue
grid for both vertical and horizontal alignment.

Printing was done on a garden variety HP Deskjet 930c. Using an
optical comparitor, accuracy is better than .001" over 8". If you wish
to verify the trammeling of your paste-up, compare your 2" grid to a
steel tape as the paste-up progresses. To transfer that degree of
precision to the work-piece, use spray-glue to attach the pasted-up
pattern to a sheet of aluminum, use an optical center-punch to prick
the centers of your tooling holes and check that with a regular
trammel.

Crude as the method above may appear, the dimensional accuracy of such
a pattern will typically exceed the standard of precision available to
the typical home-builder. Although maybe not the first time they try
it :-) Parallax plays a role in the accuracy of your paste-up as does
paper quality in your printing. But on average, ribs are pretty easy
compared to a 4x4 paste-up for a firewall or bulkhead.

-R.S.Hoover