PART 1
Construction Details of
Light Aircraft Fuselages
By Georges Jacquemin, EAA 3618
Reprinted in part from the magazine Canadian Aviation
lthough there is no general rule to classify fuselage
A
are used in amateur building. They are as follows:
structures, three main types and their combinations
1. Wooden fuselage plywood box type (Jurca "Ternpete", Jodel, Druine)
2. Wooden fuselage, truss type, fabric covered (Piel
"Emeraude")
3. Welded steel tube fuselage, truss type, fabric covered (Baby Ace, EAA Biplane and most industrial
designs such as Schweizer 1-26 sailplane)
The aluminum alloy fuselage is rarely used in ultralight aircraft construction due to the special tooling required and the necessary skills not usually possessed by
the amateur.
In general most ultra-light aircraft fuselages represent a combination of two of the above types. The cockpit
part of a truss fuselage is usually plywood covered, as in
the Smith "Termite". Diagonal bracing is sometimes used
as in a box type fuselage, while on the other hand an
unconventional aircraft such as the Fauvel AV-60 can almost do away with a fuselage structure.
First of all we will deal with the plywood box type
of wooden fuselage. Fig. 1 shows the fuselage of the Jurca
"Tempete", which is typical of this type of structure.
Basically it is a plywood box with one strip (a longeron)
in each corner. The box is held rigid by four main bulk-
heads which also introduce loads from the wing, landing
gear, engine, etc. In addition, a number of light formers
First, Fuselage Sides. Plywood sheets are scarfed and
assembled in order to convert the whole fuselage
side. The shape of the fuselage side is drawn on
the plywood with the place of each upright indi-
cated. Reference lines are drawn on the other side
of the plywood in order to aid when nailing. The
longerons are set in place with glue and nailed
through the plywood, then the uprights are fitted,
except those which are part of the four bulkheads
mentioned above. Corner blocks, gussets and other
details are then glued in place.
Second, Bulkheads. The four bulkheads are prepared
and assembled in almost the same way. The internal structure is drawn on one external face of the
plywood so that drilling for accessory attachments
can be done later. Each bulkhead is then carefully
adjusted to fit in its place on the fuselage sides.
Third, Fuselage Preliminary Assembly. Fuselage sides
and bulkheads are joined together in a preliminary
assembly using long clamps. Each bulkhead is adjusted to fit properly against the plywood of the
fuselage side. Minor corrections can be made easily
at this time.
Fourth, Fuselage Final Assembly. Procedure for this
operation is practically the same as the above. The
glue is prepared to give a long setting time so that
work can be done without hurrying unnecessarily.
The bulkheads are placed in this order: pilot's seat
support the plywood fairing on top of the fuselage, commonly referred to as the turtle deck. The structure consists of six main components: two fuselage sides and four
bulkheads (engine, main wing spar, pilot seat, and fin spar
bulkheads).
The construction and assembly of this type of fuselage
is accomplished in the following order:
Fig. 1 Plywood box
fuselage — Jurca
"Tempete "
SPORT AVIATION
13
bulkhead, engine bulkhead, wing main spar bulkhead, fin spar bulkhead.
Fifth, Final Details. Only simple detail work remains
to be done. The fin structure and fuselage top fairing structure are installed and covered with plywood. All cross members in the rear part of the
fuselage are glued in place with their gussets, after
all mechanical parts (elevator, rudder and trim tab
control) have been installed. The bottom plywood
will be installed later after the rest of the fuselage
has been finished. The cockpit area comes next,
with installation of the instrument panel former,
cockpit railing reinforcement and installation of all
mechanical parts attached to the main structure in
this area, such as controls, fuel tank, engine and
wing mounting brackets, etc. Now the internal plywood sides can be installed. The fuselage is now
nearly complete except for the bottom plywood
covering and the front top part which will be closed
after preliminary assembly of the whole aircraft.
Construction of this type of fuselage is not difficult.
One person can manage alone except for the final assembly (Step 4). Jigging and expensive tooling are not required, but half a dozen clamps and a pair of small
trestles are needed in addition to any tools the hobbyist
may already own.
every joint and gusset. The weight saving is not a real
advantage, since it is obtained at some expense in rigidity
and ease of repairs.
Basically the construction procedure is the same as for
the box type. The sides must be built in a jig, however.
They are assembled with the bulkheads in much the same
manner as the plywood box sides. The front edge of the
fuselage is made as a box with plywood sides and reinforced fuselage longerons in the cockpit area. The fuselage is then covered with fabric.
Elaborate jigging or tooling is not necessary. The
small quantity of plywood required makes it interesting
from a cost viewpoint. This structure is not as rigid as
the box type, however, and damage can occur at take-off
or landing by stones hitting any of the bars of the rear
fuselage. It would be possible to reach a repair shop with
a small hole in a plywood panel, but a broken fuselage
bar would prevent flying. Although the truss type fuselage is more economical to build, it is more expensive to
maintain.
In Part 2 of this article I will discuss the popular
welded tube type of fuselage and two unconventional
types of aircraft.
£
The second type of fuselage, the wooden truss type,
is shown in Fig. 2 which is of the Piel CP-30 "Emeraude"
described in the September issue of SPORT AVIATION.
The construction of this type of fuselage takes more time
than the box type and requires more careful adjustment of
Fig. 2 Truss fuselage
—Piel CP-30 "Emeraude"
HORNE HAS A WINNER
EAA member Bob Home of Huntsville, Ala., hauled
home a lot of hardware with his Kadiak Speedster during
the 1958 flying season. He's shown here with his airplane
and the trophies he won. Left to right, the trophies are:
1. EAA Trophy for placing in short take-off contest
at the History of Flight Show, Connellsville, Pa.,
July 5.
2. AAA Trophy for best experimental airplane at the
annual Fly-In of the Antique Airplane Association,
Ottumwa, Iowa, Aug. 30-31.
3. EAA Trophy for fastest acceleration at the 1958
Fly-In, Milwaukee, Wis., Aug. 8, 9 and 10.
4. Golden Wings Trophy for first place in short takeoff contest at the History of Flight Show, Connellsville, Pa., July 6.
We congratulate Bob Home for his outstanding
achievement and wish him luck in next year's events.
14
DECEMBER 1958