Design Improvements for the Zenith 601 HDS:
Wing Root Fairings
Wing Root Fairings
Wing root fairings have substantially improved low-speed
and high-load flying characteristics. The design process
and results are described in
Finding Hidden Drag .
The basic idea is as follows. If the fuselage expands and
contracts over the wings, as it does for the 601 HDS,
then this increases drag and reduces lift, particularly for
large payloads or high angles of attack.
The negative effects can be mitigated by a fairing
that simulates a constant width fuselage. The fairings significantly
improve climb rate, ceiling, stall speed, sink rate at low
speeds, optimum glide ratio, minimum power to stay aloft,
and stability of the plane when CG is close to the rear limit.
Generally, the required angle of attack in level flight
is significantly reduced at or below cruise power settings.
This manifests itself by a much lower nose, particularly at gross weight.
of the fairing is not difficult. One draws on the fuselage the points of
attachment of the fairing in a reasonable curve. On the wing, one
draws a straight line that is at 90 deg with the spar and that
just touches the fuselage at its widest point. Now one connects
the line on the wing with the curve on the fuselage, thus getting
a surface. The fairing must have that surface.
For creation of
the fairing, one protects the wing and fuselage with masking tape,
then establishes the fairing surface using plaster. Once the plaster
is cured and dried, one lays the
fiberglass. When the resin has set,
the fairing is removed, trimmed, and the fairing surface is finished using
light-weight filler. Of course, the plaster and masking tape are
removed as well.
The finished fairing is riveted to sidewall and wing surface,
and then painted.
Overall, one should aim for very lightweight
fairings that together do not exceed 4 lbs when painted. The photos
show the shape chosen by us.
Next are two views of the left-hand-side fairing from below.
The first picture
shows how the fairing is attached to the fuselage and leading
edge in front. The second picture shows the attachment in back.
The latter attachment is only to the fuselage
and not to the trailing edge portion of the
Finally, some pictures with paperstrip showing size in inches.
First, four pictures taken near the leading edge, at midsection,
at aft part of wing, and near the trailing edge.
Second, two pictures below the wing, near the leading edge.
Third, one picture below the wing, near the trailing edge.