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165
The Aeroplane Speaks. Fifth Edition
·
H. Barber
102
2.
Struts
and
spars
must
be
symmetrical.
By
that
I
mean
that
the
cross-sectional
dimensions
must
be
correct,
as
otherwise
there
will
be
bulging
places
on
the
outside,
with
the
result
that
the
stress
will
not
be
evenly
disposed
about
the
centre
of
strength,
and
a
bending
stress
may
be
produced.
3.
Struts,
spars,
etc.,
must
be
undamaged.
Remember
that,
from
what
I
have
already
explained
about
bending
stresses,
the
outside
fibres
of
the
wood
are
doing
by
far
the
most
work.
If
these
get
bruised
or
scored,
then
the
strut
or
spar
suffers
in
strength
much
more
than
one
might
think
at
first
sight;
and,
if
it
ever
gets
a
tendency
to
bend,
it
is
likely
to
collapse
at
that
point.
4.
The
wood
must
have
a
good,
clear
grain
with
no
cross-grain,
knots,
or
shakes.
Such
blemishes
produce
weak
places
and,
if
a
tendency
to
bend
appears,
then
it
may
collapse
at
such
a
point.
5.
The
struts,
spars,
etc.,
must
be
properly
bedded
into
their
sockets
or
fittings.
To
begin
with,
they
must
be
of
good
pushing
or
gentle
tapping
fit.
They
must
never
be
driven
in
with
a
heavy
hammer.
Then
again,
a
strut
must
bed
well
down
all
over
its
cross-sectional
area
as
illustrated
above;
otherwise
the
stress
of
compression
will
not
be
evenly
disposed
about
the
centre
of
strength,
and
that
may
produce
a
bending
stress.
The
bottom
of
the
strut
or
spar
should
be
covered
with
some
sort
of
paint,
bedded
into
the
socket
or
fitting,
and
then
withdrawn
to
see
if
the
paint
has
stuck
all
over
the
bed.
Marker
Marker
Fine marker
White-out
Fine white-out
Circle
Paint
Unmarker
Hand
Scalpel
Dice
Sieve
Purify
Undo
Redo
Start over
