US3858349A

US3858349A - Model airplane construction

Info

Publication number: US3858349A
Application number: US429919A
Authority: US
Inventors: William Duane Mcclendon
Original assignee: Individual
Current assignee: Individual
Priority date: 1974-01-02
Filing date: 1974-01-02
Publication date: 1975-01-07
Anticipated expiration: 1992-01-07

Abstract

A model airplane which is constructed principally of cardboard and a lacquer paint such as conventional model airplane dope. The strength in certain areas of the construction is provided with wood dowelling which is interposed between the corrugations of the corrugated cardboard. The radio receiver is interchangeably mounted within the airplane of this invention by means of rubber band tie down means. In a similar manner the engine is interchangeably mounted upon the airplane also by means of rubber and band tie down means.

Description

Unite States atent [1 1 [111 3,858,349 McClendon 11 Jan. 7, 1975 [54] MODEL AIRPLANE CONSTRUCTION 3,273,281 9/1966 Harrison t. 46/76 R t W'll' D M d 0 [76] or gg si if sg gfi Primary ExaminerLou1s G. Mancene 90641 Assistant Examiner-Robert F. Cutting Attorney, Agent, or Firm-Jack C. Munro [22] Filed: Jan. 2, 1974 [21] Appl. No.: 429,919 ABSTRACT A model airplane which is constructed principally of [52] Cl. 46/76 46/243 Av 46/244 B cardboard and a lacquer paint such as conventional 46/79 46/78 model airplane dope. The strength in certain areas of [51 int. Cl A63li 27/00 the cmstruction is Provided will dwemng [58] Field of Search 5; 76 243 AV which is interposed between the corrugations of the 7 4 5 7 corrugated cardboard. The radio receiver is interchangeably mounted within the airplane of this inven- [56] References Cited tion by means of rubber band tie down means. In a similar manner the engine is interchangeably mounted I 486 463 :J PATENTS /79 upon the airplane also by means of rubber and band ort 46 d 2,366,652 1/1945 Riegger [6 Own means 2,637,139 5/1953 Harris 46/76 R 9 Claims, 12 Drawing Figures Patent Jan. 7,1975 3,858,349

4 Sheets-Sheet l Patented Jan. 7, 1975 3,858,349

4 Sheets-Sheet I 2 Patented Jan. 7, 1975 4 Sheets- Sheet 4 MODEL AIRPLANE CONSTRUCTION BACKGROUND OF THE INVENTION The field of this invention relates to hobby and crafts and more particularly to a model airplane construction.

In the past, most model airplanes have been constructed of a light-weight wood such as balsa. However, balsa wood in recent years has become quite expensive which has therefore substantially increased the cost of manufacturing a model airplane. Additionally, balsa wood is quite brittle and easy to break. If the model airplane makes an incorrect maneuver and crashes into the ground, the model airplane can be easily damaged beyond repair.

Previously, there has been some attempt at designing airplanes made from paper. However, such model airplanes have been of a frail construction and easily damaged. Additionally, if the paper airplane has been damaged it has been difficult to repair such. Further, paper planes of the past have been of a design which does not encourage manufacture in kit form. It is desirable that the model airplane be of a design which would readily permit the manufacture of the airplane in the form of a kit and therefore facilitate mass selling.

SUMMARY OF THE INVENTION The model airplane construction of this invention provides for the use of a basic channel shaped fuselage wherein the open portion of the channel is along the upper surface of the fuselage. The nose section is formed of a plurality of layers of cardboard so as to minimize damage to the airplane in the event of a crash. The legs of the channel in the aft end of the fuselage are folded over upon themselves so as to provide a narrow slot to facilitate location of the vertical stabilizer. The wing is constructed almost entirely of cardboard with strips of rigid members secured within the wing structure to make the wing of sufficient strength. An engine mount is located upon the top side of the nose section and the. engine is to be mounted thereon by means of rubber band tie-down means to facilitate interchangeability. Located within the fuselage is a compartment to facilitate location of a radio receiver with also a rubber band tie-down means being employed for the radio receiver to facilitate interchangeability. Appropriate small diametered wood dowelling is inserted through the corrugations of the corrugated cardboard for purposes of providing adequate strength of the airplane construction. A lacquer isto be employed to completely cover the model airplane of this invention which functions as both paint and adhesive. The model airplane assumes a substantially solid construction of quite high strength.

The primary advantage of the model airplane construction of this invention is to provide for easy insertion and removal of the radio receiver so that the expensive radio receiver equipment can be readily used within other model airplanes. Another advantage of the airplane construction of this invention is that the relatively expensive engine can be readily removed and employed on other models. Another objective of the model airplane of this invention is that it is of quite high strength in construction, formed of a relatively inexpensive material, and resists damage in the event of an accident and facilitates repair. A further advantage of the model airplane construction of this invention is that in kit form the airplane can be easily constructed by a relative neophyte to the model airplane field.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the model airplane of this invention;

FIG. 2 is a side view of the model airplane of this invention taken along line 2-2 of FIG. 1;

FIG. 3 is a cross-sectional view of the nose portion of the model airplane of this invention taken along lone 3-3 of FIG. 1;

FIG. 4 is a cross-sectional view through the nose portion of the model airplane of this invention taken along line 4-4 of FIG. 3;

FIG. 5 is a cross-sectional view through fuselage of the model airplane of this invention taken along line 5-5 of FIG. 1;

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 5;

FIG. 7 is a cross-sectional view taken through the wing of the model airplane of this invention taken along line 7-7 of FIG. 1; FIG. 8 is a view similar to FIG. 7 but of a modified form of wing construction;

FIG. 9 is a cross-sectional view through the empennage of the model airplane of this invention taken along line 9-9 of FIG. 1;

FIG. 10 is a cross-sectional view taken along line 10-10 of FIG. 9;

FIG. 11 is a cross-sectional view taken along line 11-11 of FIG. 9; and

FIG. 12 is an isometric view of a modified form of wing construction for the model airplane of this invention.

DETAILED DESCRIPTION OF THE SHOWN EMBODIMENT Referring particularly to the drawings, there is shown in FIG. 1 the model airplane construction of this invention being composed generally of a fuselage 22 having a nose section 24, a wing 26 and an empennage 28. The empennage 28 includes a vertical stabilizer 30, rudder 32, horizontal stabilizer 34 and elevator 36. The horizontal stabilizer 34 is fixedly connected to the underside of thefuselag'e 22 at the aft end of the fuselage 22. Conducted through the flutes of the cardboard stabilizer 34 at both the forward edge and the trailing edge of the horizontal stabilizer 34 are small diametered dowels 38 and 40 respectively. The use of these dowels as well as the use of any dowels hereinafter to be described are for the purpose of providing additional strength in high stress areas. The dowels 38 and 40 are to extend transversely across the entire length of the horizontal stabilizer 34.

Attached to the underside of the stabilizer 34 is a landing skid 42. The function of the skid 42 is just to keep the horizontal stabilizer 34 from contacting the ground during landings and take-offs.

Adjacent the dowel 40, the horizontal stabilizer includes a pair of aligned

elongated cuts

44 and 46. The portions of the cardboard in alignment with the

cuts

44 and 46 are compressed and coated with the lacquer conventionally known as airplane dope. It is to be stated that the entire airplane of this invention is completely coated with one or more coats of the airplane dope. Due to the incorporation of the

slots

44 and 46 and the pressed down cardboard areas in alignment therewith, a hinge 48 is created. Hinge 48 permits the elevator 36 to vertically pivot as represented in FIG. 9.

A strengthening dowel 50 is conducted through the cardboard elevator 36 adjacent the hinge 48. A conventional control horn 52 is secured to the elevator 36 and an actuating rod 54. The actuating rod 54 is conducted through the interior portion of the fuselage 22 and is connected to an actuating mechanism 56. The mechanism 56 is movable by a conventional radio receiver 58. The radio receiver 58 moves the actuating mechanism 56 by means of ground controlled radio signals.

The fuselage 22 is formed substantially in a channel shape. In the aft area of the fuselage, the upwardly standing

legs

60 and 62 of the fuselage are turned in toward each other and then curled downward so that their free ends come into contact with the inside bottom of the fuselage 22. As a result, there is a slight gap 64 formed between the

legs

60 and 62. Within this gap 64 is inserted the vertical stabilizer 30. Because of the arrangement between the

legs

60 and 62 and the vertical stabilizer 30, when the airplane dope is applied, a quite strong connection therebetween occurs.

Within the forward edge of the vertical stabilizer 30, a dowel 66 is conducted entirely through one of the corrugated flutes of the vertical stabilizer 30 to the bottom thereof. Besides the dowel 66 functioning as a strengthening dowel, one end of an aerial (not shown) for the radio receiver 58 is to be attached to the upper end of the dowel 66. The dowel 66 is of a larger diameter then the previously mentioned dowels 40 and 50.

Extending through one of the cardboard flutes of the vertical stabilizer 30 at the trailing edge of the vertical stabilizer 30 is a smaller diametered strengthening dowel 68. Elongated aligned

slots

70 and 72 are formed within the cardboard adjacent the dowel 68 with the portions of the cardboard in alignment with the

slots

70 and 72 being pressed together to form a hinge 74. The hinge 74 is basically similar in construction to the hinge 48.

Conducted through the corrugated cardboard rudder 32 adjacent the hinge 74 is a strengthening dowel 76. A control horn bracket 78 is attached to the rudder 32. An actuating rod 80 is connected to the control horn 78 with the free end of the rod 80 to a connected actuating mechanism 82. The mechanism 82 is basically identical to'the mechanism 56 and is operated by the radio receiver 58.

It is believed to be readily apparent that by appropriate radio signals received by the receiver 58, the

mechanisms

56 and 82 are moved which result in movements of the

respective rods

54 and 80. The actuating rod 54 causes vertical pivoting of the elevator 56 to control the airplane in pitch. In a similar manner the actuating mechanism 82 through the rod 80 operates the control horn 78 to pivot the rudder 32 about the vertical axis which controls the airplane in yaw.

Mounted within the interior chamber 84 of the fuselage 22 directly beneath the wing 26 is a radio receiver housing 86. The housing 86 is constructed basically of cardboard and is secured to the lower surface of the fuselage 22 by means of the airplane dope. A pair of mounting dowels 88 (only one being shown) are longitudinally conducted through the lower end of the housing 86 with each end of the dowels 88 extending exteriorly of the housing 86. The radio receiver 58 is adapted to rest within a compartment 90 formed within the housing 86. Rubber bands (not shown) are to be wound about between the ends of the dowels 88 and over the radio receiver 58. These rubber bands are to securely retain the radio receiver 58 within the compartment during flight. However, by the use of the rubber bands, the radio receiver 58 can be readily removed and reinserted in another airplane if desired. This is a particular desirable feature since the radio receiver 58 costs several hundred dollars and therefore a single radio receiver can be employed within a multitude of airplane models. Previously, the radio receivers 58 have been bolted or otherwise securely fastened within the model airplane structure.

In the event of the airplane crashing, it is desirable that the radio receiver 58 be protected from damage. For this purpose a cardboard accordian shaped spring 92 is positioned within the forward area of the compartment 90 located in between the radio receiver 58 and the forward edge of the housing 86. In the event of a crash, the radio receiver 58 will be cushioned against the spring 92.

A battery power source 94 is mounted within a compartment 96 formed within the fuselage 22. Electrical wire leads 98 and 100 interconnect the source 94 to the radio receiver 58 so that electrical power be transmitted to the receiver 58 to operate such.

Power source 94 can also be readily removed from the fuselage 22 by access through cover 102 formed within the topside of the fuselage 22. Cover 102 is opened and closed by means of by merely bending the cardboard construction. A strengthening layer of material 104 is provided adjacent the hinge are between the cover 102 and the fuselage 22.

In order to gain access to the radio receiver 58, once the wing 26 is removed, there is an enlarged opening that permits such access into the chamber 84. Mounting

dowels

106 and 108 are conducted through the side legs of the fuselage 22 and are to be employed to connect with

rubber bands

110 and 112 and extend over in a criss-cross pattern across the wing 26. As a result, the wing 26 is securely retained upon the fuselage 22 during flight.

Rubber bands

110 and 112 may be readily removed and the wing removed to provide easy access into the chamber 84.

The first form of wing construction of this invention employs the use of a single outer sheet 114 of cardboard which has been folded over upon itself with the free ends attached by means of airplane dope to form the wing trailing edge 1 16. The first embodiment of the wing constructions of this invention is shown in particular in FIGS. 5 and 7 of the drawings. The upper surface of the wing at its transverse mid point includes a longitudinal wedge-shaped cut 120. This cut is provided so that the wing can be canted to form a slight dihedral angle as shown in FIG. 7. This angle is necessary in order for the airplane to achieve a certain element of stability. In order to fix the wing 26 in this dihedral angle position, a bracing strip 118 is conducted about the upper and lower surfaces of the wing in the area of cut 120. Bracing strip 118 is also to be formed of cardboard.

In the forming of the wing 26 it is desirable that the flutes of the cardboard extend perpendicular to the axis of the bending or scoring. In other words, the flutes of the cardboard extend longitudinal to the wing, between the forward edge and the trailing edge of the wing. In the case of the fuselage 22, the flutes extend transversely or between one side of the airplane to the other side of the airplane. If the flutes are not located in this desired manner it is found that the resultant formed construction will be quite weak and will readily fail.

In order to keep the wing 26 in an airfoil configuration, cardboard channel shaped

braces

124 and 126 are mounted within the right side of the wing and the left side of the wing respectively. It is to be understood that the overall wing construction, when complete, will be so that the right side of the wing is a mirror image of the left side of the wing. In order to insure that wing maintains its desired dihedral angle under high stress conditions, strips of rigid material such as wood strips are attached to the

braces

124 and 126, with wood strip 128 attached to brace 124 and strip 130 attached to brace 126. An intermediate brace 132 is attached to each of the braces 128 and 130 and extends across the transverse center of the wing 26. As a result, the wing 26 of the first embodiment of this invention shown in FIGS. 5 and 7 produces a solidly constructed wing which is quite strong and able to take a high stress loading during flight.

Referring in particular to FIG. 8 of the drawing, a similar wing construction 26 is shown. Within FIG. 8 like numerals have been employed to refer to like parts. The distinction of the wing construction of FIG. 8. as opposed to FIG. 7 is that the

strips

128, 130 and 132 have been eliminated and in lieu

thereof wood dowelling

134, 136 and 138 are employed in a manner substantially identical to

strips

128, 130 and 132. In other words, dowel 134 is attached to brace 124 with the dowel 136 being attached to brace 126. The intermediate dowel 138 is interconnected across the dihedral angle between

dowels

134 and 136. Also, there is a smaller intermediate dowel 140 interconnected between the

dowels

134 and 136.

Referring particular to FIG. 12 of the drawings, there is shown a second modified form 26" of wing construction including a single cardboard layer 142 which is formed in the shape of an airfoil, that is having a convex upper surface as shown. Transverse strengthening dowels 144, 146 and 148 are employed across the wing 26" with the

dowels

144, 146 and 148 extending through the flutes of the corrugated cardboard. Dowel 144 is located at the forward edge of the wing. In order to hold the wing 26" in the airfoil configuration, a plurality of longitudinally spaced apart narrow braces 150 are attached to the under surface of the wing. The under surface of the wing 26" is open with a plurality of such braces 150 being employed in a spaced apart manner. The wing construction 26" is quite inexpensive and has proved to be sufficiently strong to perform under high stress situations and also provides more than adequate aerodynamic lift for model airplanes.

The nose section 24 is formed of an outer layer 152 of cardboard and an inner layer 154. The outer layer 152 is merely an extension of the bottom of the fuselage 22. The upstanding legs of the fuselage in the area of the nose section 24 are cut into a smooth arc as shown in FIG. 2 of the drawings. The bottom of the fuselage is substantially extended to form the outer layer 152. This layer 152 is then positioned to close off the front portion of the nose section and glued to the sides of the nose section.

The nose wheel 156 is rotatably mounted upon a bracket 158. The bracket 158 is inserted through the bottom of the fuselage within the nose section and is positioned within the hollow chamber 160. Layers of cardboard and airplane dope are placed about the inner end of the bracket 158 to form an attachment 162. This attachment 162 securely holds the nose wheel 156 in the desired position.

Prior to the forming of the attachment 162, the end 164 of the inner layer of cardboard 154 is positioned against the inner surface of the cardboard layer 152. The inner layer 154 is glued by airplane dope to the outer layer 152. The attachment 162 is then formed thereby securing the nose wheel 156 in its desired position. The inner layer 154 is then passed along the forward portion of the nose section 24 and is glued to the outer layer 152. The inner layer 154 is then passed along the top side of the nose section 24 and is then turned at a right angle and extended into contact with the bottom of the fuselage and then the end 166 of the layer 154 is conducted and glued over the attachment 162. As a result, the inner layer 154 now has produced the chamber 160. The outer layer 152 is then positioned along the top of the nose section and glued into contact with the inner layer 154 and then also is turned at a right angle and is conducted to the bottom of the fuselage whereupon the end 168 of the layer 152 forms the bottom of the energy source compartment 96. The energy source compartment 96 is formed by an additional layer 170 of cardboard which is adhered to the outer layer 152 adjacent the end 168. As a result, three layers of cardboard are adhered together to form a bulkhead 172 whichseparates the :nose section 24 from the fuselage 22.

Located between the

layers

152 and 154 and adjacent the top of the nose section 24 are a pair of spaced apart dowels 174 and 176. The dowels are fixed by means of airplane dope in their respective positions. The length of the

dowels

174 and 176 is so that they protrude from each side of the airplane. The function of the

dowels

174 and 176 is to secure the. engine 178 to the airplane.

Mounted upon the upper surface of the nose section 24 is an engine mount 180. The engine mount 180 is composed of a plurality of cardboard strips stacked one on top of the other and connected together through by means of airplane dope. Conducted through the cardboard flutesof each of the strips along its lateral edges are small strengthening dowels 182. The resulting engine mount 180 construction is a solid, rigid block.

The engine 178 is attached between

wood strips

184 and 186. The spacing between the

strips

184 and 186 is just slightly larger than the width. of the engine mount 180. Adjacent the aft end of the

strips

184 and 186 and located therebetween to maintain the desired spacing between the

strips

184 and 186 is a dowel 188.

To attach the engine 178 to the engine mount 180, the engine mount 180'is located between

strips

184 and 186.

Rubber bands

190 and 192 are wound about the

dowels

174 and 176 and positioned in a criss-cross pattern across the

strips

184 and 186 and engine mount 180. As a result, the engine 178 is securely retained upon the airplane but can be easily removed therefrom and to be installed on another model airplane. A single rubber band may be employed instead of the two

bands

190 and 192.

When the engine 178 is installed as shown in the drawings, the fuel line (not shown) from the engine 178 is to be connected to a fuel tank. This fuel tank can be positioned exteriorly of the airplane and may be located upon the engine mount 1811!. Also, the fuel tank may be positioned within the chamber 160 formed within the nose section 24. It is important that the fuel tank be subatantially in horizontal alignment with the engine 178 so, if the tank is mounted upon the engine mount 180, the engine would be attached to

strips

184 and 186 so as to be in alignment with the fuel tank.

The construction of the engine mount 180 and the upper surface of the nose section 24 is such that the engine cants about five degrees in a downward direction with respect to the longitudinal axis of the airplane. The reason for this is for aerodynamic stability. Such canting of the engine is commonplace in the model airplane field.

What is claimed is:

l. A model airplane construction comprising:

a basically channel shaped fuselage constructed from cardboard, said fuselage having a nose section and a tail section, said nose section formed of a plurality of cardboard layers;

a wing connected to said fuselage, the upper and lower outer surfaces of said wing constructed of a single cardboard sheet folded over upon itself, said wing including a dihedral angle, said wing having a right side and a left side, said wing having an internal cardboard brace extending substantially the entire length of said wing, a first rigid strip of material fixed to said cardboard brace within said right side of said wing, a second strip of rigid material fixed to said cardboard brace within said left side of said wing, a third strip of material attached to both said first and said second strips of material.

2. The model airplane construction as defined in claim 1 wherein:

the constructural arrangement of parts of said right side of said wing being mirror image of said left side of said wing.

3. The model airplane construction as defined in claim 2 wherein:

said first and said second and said third strips of material comprising elongated flat strips of wood.

4. The model airplane as defined in claim 2 wherein:

said first and said second and said third strips of material comprising wood dowelling.

5. The model airplane as defined in claim 1 wherein:

an interior compartment located within said fuselage, a mounting housing secured within said fuselage, means connected to said mounting housing for attachment of a radio receiver to said housing, said means includes a plurality of rubber bands.

6. The model airplane as defined in claim 5 wherein:

an accordian shaped cardboard spring located intermediate the fore portion of said radio receiver and said housing, whereby upon said model airplane encountering a crash load said cardboard spring to absorb energy and protect said radio receiver from damage.

7. The model airplane construction as defined in claim 1 wherein:

the upper surface of said nose section including an engine mount, said engine mount including a plurality of stacked layers of cardboard, the lateral edges of said cardboard layers including elongated sections of rigid dowelling conducted through the corrugations of the cardboard.

8. The model airplane construction as defined in claim 1 wherein:

said channel shaped fuselage having upwardly upstanding legs, said legs adjacent the aft end of said fuselage being turned in toward each other and folded in a downward direction directly adjacent each other forming a small space therebetween, a vertical stabilizer located within said gap and secured to said folded over legs of said channel shaped fuselage, a rudder pivotaly connected to said vertical stabilizer, rigid dowelling vertically conducted through the corrugated cardboard flutes of said vertical stablilzer adjacent said hinge, a rigid dowelling conducted through the corrugated cardboard flutes of said rudder adjacent said hinge, both said rudder and said vertical stabilizer being formed of corrugated cardboard.

9. In combination with a model airplane, an airfoil sloped wing, said wing comprising:

a single layer of corrugated cardboard material, the upper surface of said wing being bascially convex in configuration, a plurality of rigid dowelling extending transversely through the corrugated flutes of the cardboard, longitudinal brace means attached to said wing on the under surface of said wing, said longitudinal brace means comprising a plurality of individual braces transversely spaced apart, said braces maintaining said wing in said convex shape.

Claims

1. A model airplane construction comprising: a basically channel shaped fuselage constructed from cardboard, said fuselage having a nose section and a tail section, said nose section formed of a plurality of cardboard layers; a wing connected to said fuselage, the upper and lower outer surfaces of said wing constructed of a single cardboard sheet folded over upon itself, said wing including a dihedral angle, said wing having a right side and a left side, said wing having an internal cardboard brace extending substantially the entire length of said wing, a first rigid strip of material fixed to said cardboard brace within said right side of said wing, a second strip of rigid material fixed to said cardboard brace within said left side of said wing, a third strip of material attached to both said first and said second strips of material.

2. The model airplane construction as defined in claim 1 wherein: the constructural arrangement of parts of said right side of said wing being mirror image of said left side of said wing.

3. The model airplane construction as defined in claim 2 wherein: said first and said second and said third strips of material comprising elongated flat strips of wood.

4. The model airplane as defined in claim 2 wherein: said first and said second and said third strips of material comprising wood dowelling.

5. The model airplane as defined in claim 1 wherein: an interior compartment located within said fuselage, a mounting housing secured within said fuselage, means connected to said mounting housing for attachment of a radio receiver to said housing, said means includes a plurality of rubber bands.

6. The model airplane as defined in claim 5 wherein: an accordian shaped cardboard spring located intermediate the fore portion of said radio receiver and said housing, whereby upon said model airplane encountering a crash load said cardboard spring to absorb energy and protect said radio receiver from damage.

7. The model airplane construction as defined in claim 1 wherein: the upper surface of said nose section including an engine mount, said engine mount including a plurality of stacked layers of cardboard, the lateral edges of said cardboard layers including elongated sections of rigid dowelling conducted through the corrugations of the cardboard.

8. The model airplane construction as defined in claim 1 wherein: said channel shaped fuselage having upwardly upstanding legs, said legs adjacent the aft end of said fuselage being turned in toward each other and folded in a downward direction directly adjacent each other forming a small space therebetween, a vertical stabilizer located within said gap and secured to said folded over legs of said channel shaped fuselage, a rudder pivotaly connected to said vertical stabilizer, rigid dowelling vertically conducted through the corrugated cardboard flutes of said vertical stablilzer adjacent said hinge, a rigid dowelling conducted through the corrugated cardboard flutes of said rudder adjacent said hinge, both said rudder and said vertical stabilizer being formed of corrugated cardboard.

9. In combination with a model airplane, an airfoil sloped wing, said wing comprising: a single layer of corrugated cardboard material, the upper surface of said wing being bascially convex in configuration, a plurality of rigid dowelling extending transversely through the corrugated flutes of the cardboard, longitudinal brace means attached to said wing on the under surface of said wing, said longitudinal brace means comprising a plurality of individual braces transversely spaced apart, said braces maintaining said wing in said convex shape.