Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to minimum weight, high strength
structures. More specifically, it relates to a method for constructing
a rapidly assembled, high strength, and light-weight airplane.
Conventional aircraft construction, while it may provide
optimization between low weight and high strength, suffers tBe disadvan-
tage of being highly labour intensive. In other words, a significant
part of the cost is labour, and a major portion of such labour costs are
for metal welding, bending and riveting. Thus, Canadian Patent No.
233,368 issued August 7, 1923 to G.S. Carr provides a production line
technique for producing a fuselage embodying longerons comprising steel
tubing rectangular in crogs-section, each longeron being composed of a
plurality of sections having varying diameters welded together and having
a telescoping ~oint, the larger section being reduced ad~acent to the
~oint to provide a tight fit.
Canadian Patent No. 291,474 issued July 23, 1929 to B. Bart
provides a production line procedure for forming thin steel, hollow
metallic reinforced structural units by a number of steps involving the
use of formers and electrolytic deposition to provide an homogeneous
continuous~ tllin film of metal over a skeletal framework.
Canadian Patent No. 305,131 issued October 28, 1930 to the
Boeing Aircraft of Canada Ltd. provides a production line procedure for
providing a metallic framework for aircraft. The framework includes a
series of structural members and end ~oints for securely fastening the
tubular members in end-to-end, parallel or angular relatlonship.
Canadian Patent No. 444,917 issued November 11, 1947 to A.A.
Kucher provideg a production line procedure for forming a composite wall.
The composite wall includes a grill having a mesh of substantial depth.
On the back of the grill is a hardened plastic coating, while on the
other face of the grill is another hardened plastic coating, also bonded
to the first coating.
Canadian Patent No. 928,696 issued June 19, 1973 to United
Aircraft Corporation provides a production line procedure for forming an
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elongated composite stringer for reinforcing an aircraft fuselage. The
stringer includes a plurality of tapes extending longitudinally, each
consisting of an epoxy matrix having boron filaments embedded therein
running lengthwise of the tape. Cross-direction plies of fiberglass
scrim are provided on both sides of the intermediate boron filament
tapes.
Aircraft made up of a "sandwich" of light-weight, but strong
material, have now been provided. One such aircraft, known as the
"RR-l" uses, as a basic material of construction, a foam/fabric~epoxy
resin sandwich. In its construction, foam, preferably polyurethane
foam, is formed into the desired shape; then a sheet of Dynel fabric is
spread over the foam. Epoxy resin is then spread over the Dynel, bond-
ing everything together in a light, strong sandwich structure. (Dynel
is the Trade Mark of Union Carbide for a copolymer of vinyl chloride
and acrylonitrile).
However, this structure, for aircraft, suffers the deficiency
that the basic load-carrying structure, i.e. wing spars, empennage spars
and most of the fuselage are made of wood. Moreover, the control cables
are labouriously and awkwardly installed after virtual completion of the ,~
aircraft.
Moreover, there ls an alrcraft known as El Grlngo whlch has a
tubular alrframe and wing spars. Styrofoam sections are individually cut
to shape and glued to the airframe and between the wing spars. The
styrofoam is covered with Dynel cloth and epoxy resin, and is painted
with acrylic enamel.
While such aircraft is of goot design, it suffers the disadvan- -
tage that shaping of the fuselage and wings to achieve the required
symmetry is time-consuming. Because not all the foam is bonded to the
metal, the strength of the composite is lower than it might otherwise
be and each section of styrofoam must be individually cut and formed to
provide an acceptably smooth exterior and to maintain symmetry. Also,
the control rods and/or cables are installed after virtual completion
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of the alrcraft.
~, It would be advantageous to provide such an aircraft in which
the excess weight resulting from the use of wood as a load-carrying structure
' would be minimized or even avoided. Furthermore, the difficult and labour
lnten~lve task of cutting and shaping all the foam sections should be avoided.
It would also be desirable to have the control rods and/or cables accurately
and easily placed within the superstructure during the construction of the
S actual superstructure. It would also be an advantage to have the foam cast
about the frame so that the structure is symmetrical and integral. r t
8y one broad aspect of this invention, the process is provided
for the formation of minimum weight, high strength aircraft, the process comprising:
forming a framework for the desired shape with light-weight, structural tubes
of metal or fiber epoxy composites; providing cables or rods for aileron control,
for spoiler aileron control, for flap control, for horizontal stabilizer control,
for vertical stabilizer control, for retractor control, for steering control
' snd for landing gear assembly control within selected ones of said tubular members;
!~ provlded at least a portion of the exterior surface of the aircraft of approximately
or exactly the desired shape by foamlng a plastic in situ about a combination ofuch framework and a mold; sepsrating the molded aircraft from the mold; and
~: 20 applying a flnal costing to the molded aircraft. i~
,~ By one preferred variant thereof, the mold is an external mold,
and wherein the steps comprise: placing the framework in a mold of approximately
or exactly the desired shape; providing a foamet in situ plastic around and
adhered to at least part of the framework, and contacting the interior surface of
the mold 90 as to conform generally to the configuration of the mold; and removing
i. the molded structure from the mold.
` By another variant, the mold is a hollow mandrel.
By another variant, the mold is of approximately the final shape
requlred for the molded structure, and including the additional step of manuallyconfiguring the molded product to the final shape required for the molded structure.
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By another variant, the entire foamed structure is provided by the ~-
foamed in situ plastic.
v By still another varicint, selected areas of the Framework are fllled
wlth a preformed plastic foam.
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~ By a further variant, at least one of additional foam and layers
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~!,' of glass fil).rs and resin are deposited at stress points of the fuselage.
By yet a further variant, the wing is formed by multi-layers of
foamed plastic and epoxy resin.
By two other variants, the final coating may be applied by means
of a first coating of gla~s fibers followed by an impregnation of the glass fibers
vlth a resin; or it may be applied by means of a first coating of a fabric formed
of a copolymer of vinyl chloride and acrylonitrile, followed by an impregnation
wlth an epoxy resin.
, By a further variant, the foamed in situ plastic is molded as a -
skin around at least a part of the framework, to provide a substantially hollow
core.
By another aspect of this invention, a minimum weight high strength
Ircraft structure is provided comprising: a framework of tubular members;
cablo~ or rods for aileron control, for sroiler aileron control, for flap control,
for horlzontal stabilizer control, for vertical stabilizer control, for retractor
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control, for ~teering control and for landing gear assembly control withln selected
on-s of sJid tubular members; foamed in situ plastic polded around at least a
part of said framework to provide a structure of the requlred shape; and a smooth
~kln over the shaped, foamed in situ plastic.
By variants thereof, the tubes may be for~ed of aluminum or an
alumlnum alloy, of magnesium or a magnesium alloy, of steel, or of graphite or
~, boron fibers.
By stlll other variants, the plastlc may be polyurethane, styrofoam
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or foamable hydrophilic polyisocyanate.
~, By still other variants, the skin may be epoxy resin impregnated
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- glass fibers, or epoxy resin impr~nated vinyl ~l~loride/~crylonitrile fibers
or Kevlar.
The foamed plastic, whether it be prefoamed pl~stic or foamed in
ltu plastic c~n be any of the conventional such foams. Exam~les include poly-
r~;; urethane and styrofoam. Another particularly preferred foamed plastic is the
'`-', foamable hydrophilic polyisocyanate known by the Trade Mark of Hypol (by W.R.
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Crace ~ Co.).
The skin covering the foamèd plastic or foamed in situ plastic may
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'~: be sny suitable such covering. One type is resin impregnated g]nss fibers.
Another ls Dynel fabric to which epoxy resin has been applied.
In the accompanying drawings,
Figure l is a plan view of the tubular framework of one fuselage
of an aircraft;
' Figure 2 is a plan view of the finished aircraft derived from the
',h fuselage of Figure l;
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,~ Flgure 3 is a front elevational view of the tubular framework of
the fuselage of the aircraft of Figure l;
~;' Figure 4 18 a front elevational view of the finished aircraft derived
from the fuselage of Figure 3, similar to Figure 2;
Flgure 5 ls a section along line V-V of Figure l; and
;, Figure 6 is a section along line VI-VI of Figure 2.
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~' As seen in Figures 1 and 3, the general configur;lLion is similar
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'~ to a tricycle/go-cart hybrid with a tail and with an engine
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mounted on the front thereof. Thus~ the framework of the aircraft 10 of
one embodiment of this invention includes a fuselage framework 20, front
P' wing framework 120 and rear wing framework 220. To facilitate home-
built construction, the framework preferably makes use of elbows, tees
and epoxy glue or even brazing techniques in order to minimize welding.
The material for the framework may be aluminum, boron, steel o-r magnesium;
~: or graphite fibers in an epoxy matrix. The fuselage framework 20
includes a main framework composed of longitudinally extending, rearward-
ly converging left and right spars 21, transversely extending, parallel,
10 - upper and lower forward ribs 22, a rear rib 23 and vertically extending
connecting beams 24, all interconnected by elbow connectors 25 and tee
connectors 30.
! Superposed on the framework 26 is a cockpit framework 31 also
of generally rectangular parallelepiped configuration. Cockpit frame-
work 31 also includes a pair of longirudinally extending parallel left
and right ribs 32, transversely extending parallel upper and lower ribs l ;
~- 33 and vertically extending beams 34, all interconnected by elbow connec-
. tors 25 and tee connectors 30.
One configuration of the wing is shown in Figure 6, to be des-
crlbet hereinafter. Furthermore, the wing may be a layered foam/epoxy
resin sandwich. During the manufacture thereof, rear flap control tube
~ 122, and transversely spaced-apart aileron control tubes 121 are provided.
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~i~ Two pairs of port flap control hinges and two pairs of starboard flap
control hinges 124, and two pairs of port and starboard spoiler aileron
control hinges 125 are also provided. A landing gear support beam 128
~ is provided and depending therefrom and from main spar 126 are a port and
'~. a starboard landing gear assembly 129. Landing gear assembly includes a
shock absorber mechanism 130, and a wheel 132 freely rotatable in axle
.
; 133 extending fror.~ the lower end of shock absorber mechanism 130. The
wheels are provided with aerodynamic boots 134 which reduce air resis-
tance in the retracted position.
The rear wing structure 220 in Figures 1 and 6 is similar to
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z the main win~ and includes a rear, vertical stabilizer rotatable control
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~;~! tube 222 and a frame tube 224 which adds to the center section strength,
as well as a pair of port and starboard hinges 223.
- Pro~ecting upwardly at the rear of the fuselage 20 to support
,
the rear wing is a rudder framework 250 including a pair of spaced-apart
vertical spars 251 and a pair of spaced-apart horizontal t. ~.:
interconnected to each other and to the fuselage at longitudinal spar
234.
Projecting downwardly at the nose of the fuselage 20 is a
steerable and retractable nosewheel assembly 275 including a shock
absorber assembly 276, a wheel yoke frame 277 and a wheel 278 freely
rotatably mounted on an axle 279 between the forks 280 of the wheel yoke
277. ,
~' It will be observed that nose wheel 275 assembly is secured
;~i to a cross-beam 28 within which are disposed the retractor control
s, cables and/or rods and the steering control cables and/or rods (not
:c shown). These cables and/or rods run in the fuselage framework 21 to
controls (not shown) in the cockpit 31.
Control cables and/or rods for the landing gear assemblies 127
~`~ 20 ure dlsposed within transverse tubular rib 128 and terminate in controls
in the cockpit 31.
The flap control tube 122 is rotatable to control the flaps.
Similarly, spoiler aileron control tube 123 is also rotatable to control
the spoiler aileron. These tubes are provided with operation means
which terminate in controls in the cockpit 31.
ij; The horizontal stabilizer is operated by a push rod inside
a longitudinally extending vertical stabilizer control spar 2~.
The vertical stabilizer control for the rudder is provided by
cables running inside the rearwardly extending ribs 21. The controls ;
all terminate in the cockpit 31.
Fi~ure 6 shows the construction of a typical wing, spoiler and
associated tubular supports and hinge. The hinge 125 includes fixed
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tube 121 (whi~h may be tube 221), tube 123 and tube 122. Spoiler 119
is shown deployed. Rotation is achieved by either sleeve, or bearing
means, and is achieved for the fla~s about tube 122 and for the spoiler r
~" 119 about tube 123.
Once the framework 10 has been assembled, thc~ molding procedure
takes place. The framework is placed in a suitably shaped mold. Because
the fuselage is so large, sectional molds may be used. It is necessary
also to provide an inner mandrel, e.g. an inflatable upper mandrel, to
provide a hollow fuselage to minimize the amount of foamed in situ
~ plastic required.
p;. As mentioned before, the foamed-on plastic could be sprayed
over the framework rather than using an external mold.
Similarly, the wings and rudder may be formed the same way,
although the need for a hollow internal mandrel is not so necessary.
In addition, the wings and rudder can be formed as multilayered sand-
wiches of foamed plastic epoxy resin. However, even in such small parts,
the exact shape i8 not required for the mold. Wing roots, tops, fillets
and ~oints can be exquisitely faired to the desired shape at will with
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sandpaper.
Moreover, for larger areas, part of the plastic may be provided
by preformed sheets which are secured to the framework, and to which the
foamed in situ plastic adheres
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~p, Once the plastic has been shaped to the exact shape, it is
covered with a protective skin.
As mentioned before, the foamed in situ plastic can be of any
of the conventional such foams. Exmaples include polyurethane and styro-
foam. Another particularly preferred polyisocyanate is known by the
Trade Mark of Hypol (of W.R. Grace ~ Co.).
An example of a wing section is shown in Figure 6. The frame-
work includes tubes 121, 122, 123 ~oined by plate 130. The foamed in
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~` situ plastic 131 surrounds the framework and is shaped to the proper
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aerodynamic form. The skln 132 covers the foam 131.
This provides a fnished aircraft as shown in Figures 2 ant 4
including a fuselage 420, front wing 421, flaps 422, rear wing 423,
stablll~er 424, tnll 425, and rudder 426. A preformed acrylic plastic
canopy 427 covers the cockplt 428. Conventional means are provided for
retracting the wheels into the open area o~ the flaps.
