Sequoia Aircraft Corporation F.8L Falco, Construction Manual

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F.8L Falco Construction Manual 2–5 Revision 4, March 1, 2002
dimensions given do not match the part as drawn, and when a dimension is underlined you are
being alerted to the discrepancy. In such cases you are to pay attention to the actual size of the
drawn part but to use the dimension given. Even so, there are many cases where a dimension and
a drawing do not match. You are
never to use a drawing as a pattern or to scale off dimensions
unless instructed to do so.
A Few Terms
Occasionally, you will see the notation (ref) which is the abbreviation for “shown in reference”.
This means that any part shown in reference takes second place to another dimension or part on
the drawing. The notation is to draw your attention to the fact that other dimensions are to be
used in constructing the part. The dimension given in the reference is only to help you
understand what is being shown.
This term can apply to a part or a dimension. It is a basic rule of drafting that you are only given a
specific dimension once. It may be helpful to know this dimension when you are looking at
another drawing, and this is a frequent use of the abbreviation.
You will frequently see the abbreviation “N.B.”. This is Latin for nota bene , or in English “note
well”. This is the designer's way of saying “Hey, look at this. This is important.”
It is normal to abbreviate terms. Among the most common are:
Term Abbreviation As in
Radius R 12R or .25”R
Diameter Ø or dia 15Ø, .375”Ø, 12dia or .250”dia
Inside Diameter I.D. 34 I.D. or .25” I.D
Outside Diameter O.D. 12 O.D. or .625” O.D.
The Language of Lines
The Falco drawings are done with three line weights. The heaviest line weight is used for section
lines and for view lines. A medium-weight line is used for the outlines of a part. A light-weight
line is used for dimension lines, hidden lines, mold lines, extension lines and centerlines.
A hidden line is a line consisting entirely of dashes. This shows the outline or other features of a
part hidden by the part you are seeing. The use of hidden lines allows the part to be shown as if
the part hiding it were transparent. See Drawing No. 788A. In the top view, the channel that is
riveted in place is shown entirely in hidden lines.
A dimension line is the familiar line with arrows on each end. The line is broken for the
dimension. On this same drawing, the height of the part is shown as 67mm, and the dimension
line shows that this dimension extends from the bottom to the top of the part.
Note that the dimension line does not actually point to either the top or bottom of the part.
These are indicated by two
extension lines .
A centerline is indicated by a thin line which is broken by short spaces and a single dot. This type
of line is used to show the center of a part and the centers of holes and other features. On
Drawing No. 788A again, the 13.5mm dimensions are all for the distances between centerlines.