US2337007A - Veneer structure - Google Patents

Description

E. L. VIDAL ET AL VENEER STRUCTURE Original Filed June 30, 1938 7 Shets-Sheet 1 46C X, Y

INVENTOR5 o8 Dec. 14, 1943. E. L. VIDAL ETAL VEINEER STRUCTURE Original Filed June 30, 1938 7 sheetsheet 2 INVENTOR o?? www BY ux/Luau. )':M cmu ATTORNEY Dec' 14, 1943- E. L.. VIDAL ET AL VENEER STRUCTURE Original Filed June 30, 1938 '7 Sheets-Sheet 3 Dec. 14, 1943. E. L. VIDAL ET AL y VENEER STRUCTURE original Filed June 30, 1958 Dec. 14, 1943. E. L. VIDAL ET AL VENEER S TRUCTURE 7 Sheet-s-Sheei. 5

Original Filed June 50, 1938 l ZUB Dec. 14, 1943. E. l.. VIDAL ET AL 2,337,007

VENEER STRUCTURE original Filed June 5o, 1958 7 Sheetsheet 6 BY Km Www# Patented Dec. 14, 1943 Eugene L. Vidal, New York, N. Y., and Laurence J.

Marhoefer, Woodridge, N. J., assignors, by mesne assignments, to Vidal Corporation, a

corporation of Delaware Original application June 30, 1938, Serial No. 216,704. Divided and this application April 18,

1940, Serial No. 330,300

'8 Claims.

This invention relates. to structures made of veneer, and more particularly to moldedstructures formed from veneer impregnated with a thermoplastic. l l

This application is a division of our copending application, Serial No. 216,704, filed June 30, 1938,

for Veneer structures and method for forming Another object is to provide al structure of wood veneer laminations impregnated with polyvinyl butyral or other suitable polyvinyl acetal resins, said laminations having the contacting faces thereof united and securely bonded together over the entire areas thereof, the structure being of such a nature as to permit remolding whereby repairs may be quickly and inexpensively made. y

A further object is to provide a novel aircraft which may be quickly and inexpensively made from readily available material, such as wood veneer strengthened by metal or wooden parts bonded to form a unitary structure.

Another object is to provide a novel Aaircraft; having low skin friction and light weight.

LA further object is to provide a novel method for constructing an airplane and/or structural units therefor.

A still further object is to provide a structure of the above character which is reinforced in a novel manner.

The above and other objects and novel features will more fully appear from the following detailed descriptionwhen the same is read in connection with the accompanying drawings illustrating embodiments of the novel method and means constituting the subject matter of the invention. It is to be expressly understood, however, that the drawings are for purposes of illustration only and are not intended as a definition of the limits of the invention, reference for this purpose being had to the appended claims.

In the drawings, wherein like reference characters refer to like parts throughout kthe several views,

Fig. 1 is ap perspective view of a mold carrying a layer of wood veneer yand illustrating one step of the novel process of the present invention;

Fig. 2 is a sectional view, somewhat diagrammatic, of a pressure chamber of the type which may be employed in carrying out the novel method of the invention;

Fig. 3 is a perspective diagrammatic view illustrating the principal units of an airplane structure made in accordance with the present invention;

Fig. 4 is a perspective view of one form of wing which may be employed in the present invention;

Fig. 5 is a cross-sectional View of the main wing as shown in Fig. 3;

Fig. 6 is a perspective view with parts disassembled of a second embodiment of a main wing;

Fig. 7 is a perspective view, in section and with parts broken away, illustrating one'type of wing beam `which may be employed in carrying out the present invention;

Fig. 8 is a perspective View in section and with parts broken away of the beam shown in Fig. 'I mounted upon a mold therefor;

Fig. 9 is a perspective view With parts broken away illustrating one form of mold which may y be employed in forming the beam of Fig. 7;

Fig. 10 is a perspective view, partly in section and with parts broken away, illustrating a second form of beam which may be employed in carrying out the invention;

Fig. 11 is a rperspective view of one form of reinforcing bulkhead which may be used in connection with the beam of Fig. 10;

Fig. 12 is an elevation of a secondtype of mold which may be employed in forming a wing beam;

Fig. 13 is a perspective rcross-sectional View of the beammold taken on line I 3-I3 of Fig. 12 with laminations superposed upon the upper and lower surfaces thereof; ,v 4

I Fig. 14 is a View of the parts shown in Fig. 13 with the superposed laminations held by suitable means. in the position for vulcanization;

` Fig. 15 is a perspective cross-sectional view with parts broken away of a third form of a beam member;

Fig. 16 is a perspective sectional view of one form of reinforcing rib for a beam member;-`

Fig. 17 is a perspectivesec'tional view with parts broken away of a fourth form of a beam member;

Fig. 18 is a perspective view, with parts broken away, of a third type of wing beam mandrel which is preferably employed vinforming the beamshown in Fig. 10;

Fig. 19 is a longitudinal sectional viewV with parts broken away of the parts shown in Fig. 18;

Fig, 20 is a top plan view, with partsbroken away, of a mold for a. nose section of a wing:

Fig. 20a isa section taken on line 20a-20a of Fig. 21 is aside view of a wing rib lamina to be used with the mold of Fig. 20;

Fig. 22.is a side view of a second wing rib lamina for use with the lamina of Fig. 21;

asv/,co7

of verysmall radius, a suitable plasticizer, such A as dibutyl phthalate, is employed to thin the n resin, the smaller the radius, the greater the percentage of plasticizer used. For example, if

Fig, 23 is s sectional view of a group of veneer v layers interlocked with a'rib formed` with the laminae of Figs. 21 and 22; j

Fig. 24 isa. side elevation of a wing sub-rib Fig. 25 is a side elevation of a wing, sub-rib lamina for use withthe lamina of F1524;

sheets of 0.22 inch are employed for making a structure embodying a curve having a, radius of one-half inch, it has been found desirable to add 10% by weight of dibutyl phthalate to the polyvinyl butyral.

The seasoned sheets are cut to the desired dimensions, depending upon the size of the structure to be formed or the mold to be used, and

Fig. 26 is a perspective view, withparts cut n away, illustrating one form of mold which may be used to form the member shown in Fig. 27;

Fig. 27 is a perspective view, vwith parts cut away, of the trailing portion of a wing made in y accordance with the present invention;

Fig. 28 is a `sectional view, with parts cut away, taken along the line 28-28 of Fig. 27;

Fig. 29 is a top plan view of one form of con-j f trol surface which is preferably employed;

Fig. 30 is a section taken on lineJII-f-Sooi.M

F18. 31 is F18. 29;

Fig. 32 is a sidey elevation `of a completed fuselage which may be employed in" thepresent invention; Fig. 33 is a i parts-broken,` away, of a collapsible mandrel which may be employed in forming the fuselage ya,` section taken online lis-3l Vof of- Fig.` 32, the section being takenfthrough a' transverse groove in said-mandrel; Fig. 34 is av perspective ,sectionalviem with parts broken away, illustrating a vtransverse fuselage frame `member and associated longi-` tudinal nbs: v y

Fig. 35is a.y detailed sectional view, withparts broken away, taken through a transverse frame in a plane perpendicular to the longitudinal axis of the fuselageillustrating one method of interlocking a frame member with a longitudinal rib;

Fig. 36 is a detailed sectional view taken on line -il of F1535: t

Fig. 37 is a detailed sectional view illustrating a second method of interlocking a transversek frame member with a longitudinalrib; and,

Fig. 38 is a side elevation of a second form of fuselage employed in the invention.

z In carrying out the novel method-disclosed Y herein, wood veneer sheets of suitable width and thickness are first treated with a thermoplasticV medium, preferably polyvinyl butyral.V For the mostpart, it has been found desirable to -employ wood sheets approximately '.022 inch thick, although, as will be understood by those skilled in the art, sheets of `greater thickness up to oneeighth inch, may be employed. The polyvinyl butyral is applied to these sheets by means of a brush or spray or by passing the sheets through a `liquid* bath with or without pressure, and in certain instances it may be necessary to press thin sheets'fof polyvinyl butyral upon the wood veneer. 'A seasoning period of approximately twelve hours is desirable to permit the resin to dry on the sheet. At thev present time it is found preferable, after saidtwelve hour period,

. 30 perspective sectional view, withk y A Vious spots4 for temporarily securing the sheets are then laid oneupon the other on said mold,

adjacent layers vbeing so positioned, that the lgrain of the woodfin two adjacent sheets is lmade to conform `temporarily to the mold as by means 'of clamps, elastic' bands, cleats or sheet metal wrappings. Close conformation of the sheets thus positioned is not essential. To further assist in holding the sheets in position, they may be spot welded to each other by 4means of a hot iron. Alcohol, which will dissolve the thermoplastic, may be applied by hand to vartogether, a light pressure being applied toportions treated'withi the alcohol. The outer `surface of the laminations covering;v the mold is now covered with anon-adhesive materiaLsuch as Cellophane, in order to prevent said surface from adhering vto pressure transmitting means which will be in contact therewith.

A sharp-pointed tool is 'now employed for making perforations through the loosely assembled sheets whereby the formation of air blisters during the vulcanizing step is prevented.

While mechanical means, such as heated pressing elements, may be employed for rendering the thermoplastic tacky and for applying pressure-to the sheets assembled on the mold to secure adhesion and to press the sheets into substantially a homogeneous mass, it is preferable, except for flat pieces, to place the mold and assembled veneer sheets within a fluid-tight container formed of ilexible or resilient mateplaced in an air-tight drum which may be heated, as by means of steam heat, and which rto subject thersheet to a second treatment of l the resin. The seasoning period may be accelerated by subjecting the treated sheets to hot, dry air currents.

If the structure to be formed embodies bends willA withstand a substantial fluid pressure, it being understood that the mouth of the bag is tightly closed ina manner to be described hereafter. 'I'he fluid-tight bag is connected by means of a suitable conduitto the exterior of the heated container, The air pressure within the outer container is now raised to from fifty to seventy pounds per square inch, and the temperature therein is raised to from 200 F. to 210`F., for example. The air within the exible bag is thus forced out through the conduit by the pressure within the heated container, `and this pressure is effective to cause the walls of the bag and the tough andyieldable sheets to conform to the outline of the mold, whereby the thermoplastic which is now tacky is rendered eifective to cause the sheets to adhere one to the other throughout the whole.

. The temperature and pressure may be varied layers of wood veneer. Another variable factorI is the time during which the sheets are subjected to heat and pressure. If the veneer structure is composed of three thin layers of veneer, for ex-` ample,lit has been found satisfactory to subject the same to heat and pressure for a period of approximately ten minutes. On the other hand, if sufficient sheets of veneer are employed to make a finished product having a wall thickness of one-half inch, the heat and pressure should be maintained fora period of approximately thirty minutes. At the end of this period the heat is shut off andthe flexible container, mold and structure are permitted to remain within the pressure chamber until the structure has been reduced to approximately room temperature.

Thereupon, the metal container is opened, the

rflexible bag is removed therefrom, opened, and

the molded structure and mold are removed. It will now be found that the molded structure can be readily removed from the mold, and that the surfaces thereof will be smooth and glossy. Polyvinyl butyral is normally amber transparent and it will be found that the molded structure presents a very pleasing appearance with the natural appearance of the wood grain preserved. If desired, however, coloring'matter may be introduced into the resin.

In forming a simple structure, such as a vesided radio cabinet, a suitable mold 40 (Fig. 1), preferably formed of one or more wooden blocks, is employed. I'he mold is first covered with a layer of non-adhesive material, preferably Cellophane. If desired, however, the Cellophane may be spot welded by a hot iron to the inner surface of the first wood veneer sheet. A seasoned sheet of veneer 4|, after being cut to size, is bent over the three sides 40a, 40b and 40e of the mold and may be temporarily held in place by hand, or if desired, by a loose rubber band passing substantially around the center of the sheet and mold. If it is desired to reinforce, for example, the upper surface of the cabinet, a reinforcing member comprising a resin treated rounded wooden strip v42 may be placed during assembly upon layer 4| above a channel 43 cut in the mold. The channel is provided to prevent the formation of a bulge upon the outer surface of the cabinet over strip 42 when other wood layers are added. The strip and veneer will be forced into the channel during the application of pressure, thereby insuring a smooth outer surface after vulcanization is completed. A second treated sheet 44, having ears 44a, 44h and 44e, is then placed against the end of the mold and the ears are bent over and spot welded by means of ahot iron or by the use of alcohol. A sheet similar to sheet 44 is placed over the opposite end of the box and the ears thereof are secured to sheet 4| as previously described. Another sheet similar to sheet 4| is now positioned on the mold and is Ispot welded t-o sheets 4| and 44. Thispositioning of sheets is continued to secure the desired wall thickness and strength, any desired number of sheets being employed and eachrnew sheet similar to sheet 4| being slipped under the rubber band, if the same is used. y

In wrapping a number of veneer layers about the mold, a certain amount of slack or play will exist between each of the layers and between the layers and the mold which will produce numerous wrinkles in each individual layer. In order to overcome this condition, i. e., to flatten the wrinployed to punch small air throughout the entire area of the superposedy kles and take up the slack, it has been found desirable not only to strap the veneer layers as tightly as possible upon the mold, but also to cut grooves at certain locations in the mold whereby the play may be taken up by pressure during vulcanization, which will force the veneerin the grooves. A groove 40d having this functiony is shown in mold '40 (Fig. 1).

'Ihere is thus formed a loose covering of a plurality of sheets around five sides of the mold. A sharp-pointed tool, vsuch as an awl, is now emholes at Aintervals sheets in order to blisters.

Instead of interposing a rounded wooden reinforcing member, as above described', it is possible to reinforce the cabinet `by placing sheets of resin prevent the formation of air treated metal or fabric between the wood lamina? tions, it being pointed out that the polyvinyl butyral is effective to adhere closely to and to produce an intimate vbond between these materials and the wood when subjected to heat and pressure.

If it is necessary that ya bolt extend through the laminations of the cabinet whereby the area adjacent the bolt will be subjected to excessive stresses, it is possible to distribute the stresses and to reinforce said area by placing a resin treated metal washer to receive the bolt between the wooden laminations during the assembly ofv the cabinet. The washer during assembly of the cabinet may be temporarily secured in position upon a desired lamination by spot welding as above described. y

In order to provide hinges for a cover for the sixth side of the radiocabinet, suitable hinges (not shown) which have been treated with the polyvinyl butyralmay be inserted before vulcanization between the laminations at an edge of the cabinet. The hinges instead of being inserted after the laminations are assembled may be positioned during assembly and temporarily secured in place by spot welding. The outer layer of veneer covering the mold is covered with' Cellophane, which may be tacked in place by spot welding. The mold, layers of veneer, and Cellophane are then placed in a fluid-tight flexible container 45 (Fig.` 2), for example, of rubber, having an opening 45a in one extremity thereof for the insertion of the material to be vulcanized.y The lips of the opening may be tightly closed by clamping same between two rigid strips 45h, 45h which may be drawn together by a suitable clamp. 'I'he assembled materialland bag 45 are placed within a metal drum 46v having removable end plates 46c. A suitable non-collapsible conduit 45e having a valve 45d therein permits communication between container 45 and the atmosphere external to the drum. y

A vulcanizing process then follows wherein a fluid pressure is applied to the veneer, for example, air controlled by valve 41 is'forced into the drum to a predetermined pressure, i. e., from 50 to 70 pounds per square inch. The air within the elastic container 45 is forced therefrom through conduit 45e and the container is pressed closely against the veneer and mold. Simultaneously with the application of pressure the drum is heated, for example, by steam in pipes (not shown) to a temperature sufficient to cause the polyvinyl lbutyral to become tacky, i. e., from 200 F.\to 210 F. As soon as the resin has become suiliciently tacky, and the pressure great enough to press the veneer sheets firmly together and to force them to conform perfectly to the mold, the temperature is reduced lto normal` However, the pressure is not removed unti1 the or subdivisions 52, each of which may be formed upon a suitable mold in a manner analogous vto that of the above-described radio cabinet, with the exceptionthatthe forward and after faces of each cell 52 remain uncovered, and the laminations 52a which constitutethe' upper and lower surfaces thereof are provided with portions 52h, which extend beyond the forward and after edges of suitable side rlbs 52o. In combination with the cells 52 there are employed a' pair of resintreated beams 53, 53, preferably of a woodsuch as spruce,which extend the full length of the wing andserve vas the main strength or supportingmembers therefor. r, Beams 53 are preferably equal in height to the vertical distance between the overlapping portions 52h and are adapted to treatingthe rveneer layers is analogous to that in forming the above-described cabinet.y After completion of a vulcanizingf `process, the component partsy of the wings, for` example, are socl'ose'- ly associated and interlocked 'that they may be considered t have Ablended into a substantially Y homogeneous piece. For example, itis possible to mold a plurality of wood veneer layers into an entire aircraft wing structure comprising one piece. This single piece is constituted by a wing-shaped shell, as shown in Fig. 4, having a longitudinal rib and afplurality of .transverseribs which may be interlocked with thevinn'er surface of the yshell after vulcanizing `the latter upon a suitable mold. However, the inspection, teste ing and repairing of such a single piece is more ditllcult than if the structure were made -in sev-V eral sections; consequently. the wingis subdivided (Fig. 3) into a central wing beam member l 48 which comprises a main support for a nose 1 or leading section 49, 4and a trailing sectionll.

Suitable control surfaces or `ailerons 50a are pivotally mounted upon the trailing section. A stationary flap `member 5|Jb`v similar in construction to ailerons 50a is rigidly secured (Fig. 3) to trailing section 50 along the trailing surface of the latter between, the aileron and the fuselage. These sections may be mechanically fastened to one another (Fig. 5) or joinedby vulcanization.

'I'he joints, however, as above mentioned, are for facilitating inspection and repair.

In the subdivided form of the wing shown .in Fig. 5, the nose section, beam .and trailing section each comprises a complete unit and each is equal in length tothe length of the wing. However, in the second embodiment ofthe wing shown in Fig. 6, these members are subdivided into a series of separable cells or compartments each of which may be formed upon a separate mold. For example, the nose section4 of the .embodiment is constituted by a plurality of cells or subdivisions 5| each of whichupreferably is equal in size to a corresponding portionof the nose section 49 whichis. included between two ribs. Each cell 5I `comprises suitable vulcanized laminated side ribs 5|a, 51a, which' reinforce a skin 5Ib. vThe ribs .are formedand provided with suitable ears upon the outer edge thereof and are attached to the skin 5Ib in amanner analogous to that to be described later in connectionwith nose sec-- A supporting member for this embodiment of the wing comprises a series of box-shaped cells be secured between said vportions by vulcanization.

v.'I'he trailing member for the wing is similarly subdivided into a series of cells 54, each of which is formed upon a suitable trailing section mold in al manner analogous lto subdivisions '52. The cells 54 are therefore similarly provided with both forward and rear overlapping sheets 54a at both upper and lower surfaces thereof. The forward overlapping sheets provide means for securing the trailing subdivisions to the supporting member, whereas the after sheets 54a are provided for overlappingen aileron and for preventing eddy currents therebetween;

In assembling the above parts to form a. completed wing, adjacent faces. of the side ribs of the nose, beam, and trailing sections are vulcanized together, for example, by vplate presses, to

yform rigid bonding, engagements therebetween.

Following this, the beams 53v are interposed each between two of the overlapping sheets 52h and there secured by plate pressing. The overlapping 'sheets 5Ic of the nose cells and forward sheets of the trailing. cells 54a, are next plate pressed to the assembled supporting member and the wing is formed. In Figs. 5 and 6, thecrosssectional area of. the superpos'ed laminations is shown as if it were a single piece without representing the individual laminations.

Iny forming the supporting beam 48, there is first constructed a suitable mold 55 (Fig. 9) comprising, for example, an oblong wooden mandrel, having a cross-section with'a proper curvature washout and "taper which conforms `to the airfoil section of a desired wing. The mandrel 55 of Fig. 9 isshown as a single piece of wood,

g tapering longitudinally from the inboard extremityor butt to the outboard extremity or tip. The four longitudinal edges of the mandrel are.

roundedand carved or kerfed to provide longitudinal convex channels 55a for a veneer strip constituting a reinforcing inner corner piece to be positioned in a manner to appear later. A butt flange 55b'(Fig. 8)`is 'Secured to the inboard extremity of the mandrel for a purpose to appear later. f i

In forming a wing beam over this mold, for reasons above explained, a non-adhesive material, such as Cellophane, is placed thereover and caused to cling closely thereto, for example, by means of wax placed on the mold. Sheet-reinforcing corner strips 56 (Fig. 8) having been treated with polyvinyl butyral are next placed in the longitudinal channels 55a and therey retained by rubber bands or suitable straps (not shown). A primary layer of wood veneer 5l (Fig. 8) is then slipped beneath the rubber bands and wrapped about thev mandrel with its grain, for example, extending parallel to the longitudinal axis of the mandrel. Ear portions 51a are cut in sheet 51 so as to abut the mandrel flange 55h, and additional layers are similarly placed over the primary layer until the beam shell has a desired thickness, each added layer having its grain substantially perpendicular to or at an angle relative to the grain of the preceding layer, and also being provided with ears similar to those of layer 51 which collectively comprise a beam flange 58 (Fig. '1) for securing the beam to a fuselage or to .another beam. The collective thickness of the veneer layers may progressively diminish toward the beam tip, i. e., each layer may terminate at a predetermined distance from the tip. Reinforcing strips (not shown), for example, of rounded wood construction analogous to the strip 42 shown in connection with Fig. 1, may be placed upon any desired layer and temporarily held in place by means of glue or by spot welding, while the next or succeeding layer is placed thereover. Upon the central upper and lower surfaces of a final layer 59, longitudinally extending strips 60 (Fig. 7) are positioned in or der to form a suitable step upon each of said` upper and lower surfaces to form a flush surface with an overlapping portion of a nose piece and a trailing section to be described hereinafter.

The mandrel, with the outer veneer layers having been covered with Cellophane, is then placed Within a flexible fluid-tight bagl similar to bag 45 employed in connection with the cabinet shown in Fig. 2. The bag and its contents are then placed within drum 46 and subjected to a vulcanizing process as above described.

The beam mandrel, instead of comprising a single member, may be constituted by a plurality oi. tted pieces which are so associated that one piece functions as a key wedge portion, enabling the easy extraction of the remaining pieces from a vwing beam after the removal of said key. A beam mandrel 6I of this character is shown in Figs. 12, 13 and 14 wherein, for example, a member 62 comprises the key wedge portion and is surrounded by four longitudinal side members 63 and 64 upon the top and bottom surfaces, and members 65 and 66 upon the forward and after suriacearespectively. The latter two members extend above and below the upper and lower surfaces of wedge 62 and cover sides 63a, 63h and 64a, 64b of members 63 and 64, respectively. The outer edges of members 65 and 66 are rounded as at 65a, 65h and 66a, 66h, respectively. The key wedge52 is rectangular in transverse 'cross-seotion and is preferably of hollow reinforced construction. When the side members 63, 64, 65 and 66 are assembled upon the key wedge 62, channels 61 encircling the entire mandrel are out therein at predetermined intervals along the mandrel axis, the plane of said channels being perpendicular to the molds longitudinal axis. The outer edges of these channels are lleted in order that ribs which are to be placed therein may be of a desired cross-section.

One of the most diillcult problems met in forming a structure of superposed laminations about a mandrel such as the one shown in Fig. l2 concerns the cutting of the laminations to suitable having a width preferably slightly less than that of the channel.' The strips are wound about the mold in the channels until flush with the outer surface of said mold. Each strip may be spot welded to the strip therebeneath in order to hold it in position. The outer strips which' are placed in the filleted portion of the channel are surticiently wide to t snugly therein. I

Following the positioningof the veneer strips in channel 61, several superposed sheets of wood veneer, for example, four, having a length equal to that of the mandrel, are positioned upon the lower face of the latter. These sheets are of such a width that they extend beyond the longitudinal edges of the mandrel preferably a distance equal to from 75% to 90% of the width of the mandrel side members 65 or 66. The sheets are then temporarily attached to the mandrel, for example, by readily extractablenails which `are driven along the longitudinal centerline of the group of laminations.

A second group of laminations is next placed upon the upper surface of the mold. This group comprises a greater number of laminations than the first-described group, and in the form shown, is constituted by ve laminations, which extend beyond the edges of the mandrel (Fig. 13) a distance preferably equal to approximately 50% to 65% of the width of side members 66 or 66. These laminations are temporarily secured to the mandrel as above described. The `air holes may be formed in one or more oi the sheets before assembly on the mold, if desired, or the same may be formed after all sheets are assembled on the mold.

The outwardly extending portions of the lower group of laminations are ythen bent towards the side members 65 and 66, and the overlapping portions of the upper group are bent thereover and temporarily held in overlapping relationship by adjustable bands 69, as shown in Fig. p14. In order to prevent parts of the flexible bag used in vulcanizing from becoming interposed between the upper and lower groups of laminations, a sheet 10 of suitable material, such as tin, is positioned to cover the gap between said groups and is held in position by the bands 69.

The assembled material is covered with Cellophane and placed within the flexible bag 45. The air is now preferably exhausted from the bag, causing the laminations to be pressed 'closely against the mandrel. 'Ihe step enables an inspection of the overlapping laminations before the vulcanizing process by noting the contour of the'bag, and any desired rearrangement can be made before the parts are placed in the vulcanizer.

Following this, the evacuated bag and'its contents are introduced into the pressure chamber and subjected to heat and pressure, as above described. The fluid pressure acting upon the laminations is eiective to iiatten any wrinkles therein and to force them away from the longitudinal centerline of the sheets outwardly towards the` outer atmosphere, i. e., valve 45d may be opened,

thus destroying the vacuum. Since the fluid pressure in the drumexceeds normal atmospheric V pressure.gthere will be no danger -of disarrangement ofthe superposed laminations. A portion of the moldedl beam `after vulcanlzing is shownv inFlg.15. Another embodiment of abeam formed in vau approximately similar manner isA shown in Fig. 17.'v

Inthe previous embodiment, the portions of the laminations kwhich overlap the sides of the mold.

comprise the sides ofthe beam. Howevenrin this embodiment the overlapping portions are not of sufllcient width to form the sides,` the latter being formed by separate groups of superposed laminations. Informi'ng this beam, groups 1| and 12 portions ofrgrou'ps 1| 12 arethen temporarily bent over groups 13,'and metal sheet 18 (Fig. 14).,

secured by straps, isgplacedthereover andthe above process` is repeated in forming the beam,

a sectional portion of which is shown in said Fig.1'l. i.

Athird embodiment of the beam. mandrel is illustrated in Fig. 18 vand comprises a series of segments 13a and 181i whichare removably. secured, for example, by means offsuitable bolts and nuts 14, 1li, respectively, lto abase'18. Each pair of segments13a, 18h is in `contact with each beam wouldbe impossible, due to said ear piece hannel 18. A portion of a coms the kshape of a channel and is preferably mechanically fastened to a cover strip 8| comprising superposed wood laminations vulcanized in a manner above described. The ear' portion 11a adjacent the cover-strip may be glued thereto. l

After molding a wing beam upon one of the mandrels in the manner above described, the nose section 48 (Fig. 3) may be formed. The mandrels used for molding thenose section in the formy shown in Fig.l 20 comprise a series of wooden mandrel segments 82 conforming in cross-section to the nose portion of an airfoil section of aj desired wing. The series of segments are mounted, for v. example, by suitable bolts 88 and nuts 84 .to a base 85. The nose mandrel is thus made up of numerous sections in order that ribs l86 (Fig. 23) to be later described may be positioned in the rib channels or spaces between the segments. The base mandrel 8l serves notv only as a mounting for the segments 82 butjprovides surfaces 85a,8la (Fig. 20a) over which the veneer layers which cover the nose section may overlap and be vulcanized to one 'another to providery a necessary overlapping sheet for securing the'nose section 48 to the wing beam 48. The leading edge of the nose mandrel is kerfed, i. e., an outer layer of the wood thereon other, ,but is spaced aparta small distance from the next pair of segments (Fig. 19). Reinforcing bulkheads .11 having ears 11a thereon (Fig. 11) are positioned in the space between said pairs of segments. The ear portion 11a upon thelowermost edge of each bulkhead is folded perpendicular to the plane of the bulkhead in `orderto t into channel 18 which is cut inthe lower surface of segment 13b. A primary veneer layer 18 of suitable dimensions is next placed over each segment and caused approximately to conform thereto by means of clamps (not shown) whereby longitudinally extending flanges 19a arelfformed abutting the base 18. v The outwardly extending ear portions 11a of bulkhead 11 are next koverlapped upon layer 18 and spot welded thereto by means of alcohol. This `temporary adhesion will hold the primary veneer llayers in place and willy thus permit the removal of said clamps. Successive veneer layers may now be superposed thereupon, eachlayenfor example, being temporarily held in place over the adjacent 4layer by spot welding with alcohol along a portion thereof aboveviiange 18a or by temporarily spot welding by meansof a hot iron. Each successive layer mayv cover the entire length of the mandrel. y

The assembled layersl and the mold are now inserted in bag 45 and vulcanized as above describedr- Upon `Withdrawal ofthe mold and vulcanized;,iltruc'ture fromthe bag, nuts 18 are disengagedf'rom boits 14 and the base `18 is lifted therefrom. Following this, segment18a is lifted from its position, thus making possible the shifting of segment 18h along'the axis of the beam out of engagement with the overlapping e'ar piece- Y 11a which occupies channel 18y of said subdivision.

If the segments were not subdivided. itis seen that the extraction thereof from the vulcanized is removed to provide a keried area 82a for an inner reinforcing nose strip to appear later. A shallow channel 81 having rounded outer edges may be cut in each segment 82 beginning at88, vand. continuing around the nose to the opposite side of. the base, in order to hold a small reinforcing frame or sub-rib analogous to thebeam frame shown in Fig. 16.

. An end portion 82h of each segment is removable therefrom to aid in positioning rib sections. to `be later described,y said removable Aportions having'suitable kerfed areas or channels 88 upon the side faces thereof adjacent to the spaces between the segments. These channels are provided vto accommodate reinforcing strips which may be placedbetween the veneer layers of said ribs. f

. Each nose section rib in the embodiment illus.- trated in Fig. 23 comprisesv three layers 80, 8| and vulcanized together as above described. The central layer 8| (Fig.4 21) is in the shape of an airfoil'and conforms to the cross-sectional area of the nose mandrel with the exception that an outer strip 8|a has been trimmed oil to permit the insertion of -a wooden fillet to appear later. The outer layers 80, 82 (Fig. 22) are provided withl outwardlyextendin'g ears 88 (Fig. 22)

which be bent over to become interlocked between vneer layers forming the nose section proper. In order that the above-mentioned reinforcing nose strip may be positioned upon area 82a, no earpieces are provided at that portion of either rib 88er 82 which will ,beVK adjacent area 82a when placed upon the mold. The ears 88 extend beyond theairfoil contour of the rib, and beyond the outer surface -of mold 82.

Y As shown in Fig. 23, the nose rib has been constructed with a reinforcing strip 84 between layers 80, 8|. 1 The strip is preferably ofresin treated wood of semi-circular cross-section.y The bulging portion of layer 88 which conforms to the shape of said strip is accommodated by one of the above-mentioned grooves or channels 88.

which are cut in the face of each removable end portion 82h,

Suitable sub-ribs are provided which are substantially in the shape of a horseshoe, said subribs being positioned in grooves 81, and are formed from laminations 96 and 91 (Figs. 24 and 25) in amanner similar to that employed in forming ribs 8B.

The main ribs 86 and the sub-ribs are placed in their respective channels upon the mandrel after covering the mandrel with Cellophane. Following this, a U-shaped cove molding strip' 98 of substantially triangular cross-sectionv is fitted between the ear portions 9310i the two layers 90,

92 (Fig.f23) to provide a 1let`therebetween. The

above-mentioned reinforcing nose strip (not shown) which 'extends longitudinally over the full length of the'nose mandrel, is next placed in the longitudinal kerfed area'82a alongthe leading edge of the mandrel. Veneer layers 99 (Fig. 23) `are then placed between each rib and sub-rib and cover the mandrel and overlap each side 85a of base 85.. The outwardlyextending ears upon each rib are bent over against these adjacent veneer layers r99 and tacked thereto by means of alcohol as-above set forth. Additional veneer layers are applied to the mold, each of which is separately positioned thereupon and held in place by one of the, methods above described, i. e., by spot Welding or by slipping same beneathA rubber bands placed around the'mold.

For a purpose above explained,'-the outer veneer layer of the nose section is next covered with a non-adhesivesubstance. Perforations are made in the material to prevent air locks. -In order to prevent wrinkling of the veneer sheets .while undergoing vulcanization, the nose section preferably is covered with a metal sheet, for example, sheet tin, which is strapped tightly thereto. This sheet, when subjected to -fiuid pressure, causes wrinkles in the 'veneer to be forced towards, and flattened upon, the base 85. The entire section is then placed in a rubber bag and vulcanized as above set forth.

The trailing section 50 is formed upon a mandrel (Fig. 26) the cross-section of which conforms to an after portion of theairfoil section of the desired wing. Both the forward andv after surfaces of the section are at. Mandrel |00 is constituted by a baseportion |0| and a plurality of segments |02 which are removably secured thereto at predetermined intervals, each segment being provided with aJ removably secured cap member |03 having rigid'side faces |03a, |03a. The upper edges |02a, |02a of the segments are rounded to protect the laminations placed thereover from fracture.

The base |0|` of the mold serves a purpose analogous to that of the base portion 85 of the nose mold, i. e., to provide two rigid faces l0la, |0|a over each of which aseries ofy superposed laminations may be vulcanized into suitable overlapping sheets for attachment to the beam member, asshown in Fig. 5. 'Ihe rigid faces |03a, |03a of the cap members |03 are also employed for forming laminated sheets thereover which are to overlap the forward longitudinal portion of an aileron or control surface, and thus to prevent leddy currents which might otherwise occur in the space between the trailing section and the aileron.

In forming the trailing section upon the mandrel,` the cap members |03 are removed from their corresponding segments. The cap members and the segments |02 and base |0| are then covered with a non-adhesive sheet material. An initial veneer lamination |04 is placedv over each segment, said lamination being of such dimensions that it will cover the top face of each seg- '5 ment, i. e., theface vadjacent cap |03, and in additionk side faces |0|a, |0|a, |02b', |02b, the latter two comprising the side faces of the segments 02. Lamination |04 is held temporarily in position upon the mold by suitable clamps 1o (not shown.) Caps|03 are next secured to the segments |02, for exmpleby Wood screws. A second lamination |05v is next placed upon the mold comprising a sheet having a central portion |05a (Figs. 27 and 28) which conforms in shape to the combined cross-section of the segment |02 and cap |03. An integral upwardlyextending ear |05b, having a central perforation therethrough, is provided surmounting the central portion |05a,` the ear serving to reinforce a rib memberto appear later. Integral with this central portion are flaps |050, |05c-, each of which is adapted Afor covering the combined pair of faces |02b, |03a on one side'of the mold. Lamination |05 is initially positioned upon the mold so that the central portion |05a is in' the gap between segments |02. l Flaps |05'c` are bent to overlap those portions ofv laminati'o M4 which cover faces |0217, the above-mentioned clamps are removed, and said flaps are spat.

welded to the adjacent lamination, thereby holding the latter in position adjacent the mold. This process is repeated for each segment,there being two laminations |05 (Fig..28) positioned in eachgap between the segments,`e ih-lamination havingthe aps |05c therebffolded over the faces |0217, |03a of the adjacent segments and caps, respectively. This will therefore place two of the aps |05c upon each of said faces, as

l -shown in the upper compartment of the trailing section illustrated in Fig, 28. For the sake of each of said faces ixrfithe'- ldwer compartment of the trailing section, gnb los 1s next interposed in the gap between 'central portions, ,l |05a (Fig. 28). The rib corresponds in shape to said centrall portion combined with' ear |051)I and is provided with acentral perforation which registers with the perforation in ear |0522.'- A'shaft may be inserted in said perforations to pivotally secure an aileron to appear later. i

An outer lamination |01 equal in length to the length of the mold and of suflcient. area to cover the combined faces |0|a, `|021 and |03a upon one side of the mold is next `positioned upon said faces and spot'welded in position or held in place by suitable clamps (not shown). The

assembled material is covered with a sheet of non-adhesive material and vulcanized 'as above described. i

A control surface for the above described'wiig may be constituted by an aileron having an outer surface of Wood veneer laminations. However, in order to damp possible vibrations in this member, it may be desirable to construct an aileron framework' having suitable ribs and to secure a fabric thereover.' Such a fabric covered, aileron |08 is illustrated in the embodiment of Figs. 29 and 30. The aileron is constituted by a plurality of hollow ribs of vulcanized laminated construction'of two distinct shapes, i. e., ribs`|09 and ||0, the former 'of which is in the shape of a wedge having a triangular longitudinal crosssection, and the latter in the shape of4 a frustrum of a pyramid having a rectangular base. These ribs are alternately disposed along the longitudi- Y nel axis `of the aileron` with the' tapering pore, V-tions .extending aft, andare all secured in a manner tovlater appearto av common ilet member ||I which comprises the; trailing edge of the aileron.` The bases of tl'ieribs which constitute the leading faces thereof` are'. each secured to aV longitudinally extending 'istrip U2-also of lami- /natedvulcanizedl construotionbymeans ofl ears ||2a (Fig. 30), `whichfengagesuperposed ears 7 ma, una orribs me and.||o,.respecuve1y; A

plurality of aileron nose pieces H3, each having a. U-shaped cross-section, is positionedpver said vstrip .|I2 and secured to Vribs |09, |I0 bythe pleted member to form the gaps" in which members III are placed. The mold is replaced within'the members leach subdivision assuming its former position .upon the mold. ASheet ||2, having ear portions ||2a integral therewith which are so located as to fit directly beneath ears |09a and I |a,'i`s next placedupon the flat longitudinal face wofthe-above mold. Ears |I2a .are bent ythereover and spot welded in position. The aspieces |.I3 are distributedralong-said strip |,|2

in such, a manner :that afgap, Voccurs between thev piecesover thefcentral portion of the rectangu-f lar bases ofribs'l I0. This permits the-positioning in said gapsupon. strip .I I2 of a bifurcated member :H4 for `engagingthe ribs of the traily ingsectionand thusfor pivotally securing the aileron tothe ,wing llVlIemb'er- Ill .is provided with an afterY extending -bolt ||4a whichV passes 'sembled materialkisv then inserted between the overlapping ears l|09afand| |0a,and vulcanized in positionfby not irons. 'I'he mold is then withdrawn. Following `this, fabric |24 may be platepressed `to the completed structure over the ribs. The vnose vribs or plugs ||6 having ears IIBa, which serve as ribs for ,the members I3, are next inserted in each open extremity of each of said f-memberswith theears I |6a extending outwardly toward-the opening. The ears then are platepressed to the adjacent laminations. x `In forming the fuselage of the present invenl tion, it is desirable that'this structure comprise through-a'perforation in jstrip. I I2 and through a reinforcing 1ar`nination.,||, 5 which may be vulcanized to said strip. .A suitablenut ,I |4b secures said bolt Ain position. Suitablenose rib mem# In forming, for example, the aileron rib ||.0 (Figf3l), ay suitable mold (not shown) is covered with a non-adhesive material. Vertical vside lam-v `bers IIS, having,- ears' |6a, are positioned. 'in i Asaid nose `pieces in a v'.fnannerpto later appear.-

inations Ill are positioned'onlthe mold and are held in position, for example, rbyelastic bands; Laminations ||8 |9, covering the top and bot- V -tommold surfaces, respectively, and overlapping a part ofthe side laminations Ill by means of nextslipped beneath said bands, if used. Resin treated-fillet membersg|20 of Vsubstantially,tri-- angularcross-section arev .positioned at each of the four edges of the rib whichextend from the i base thereof to the tip'.H Flat laminations |2| and |22 (Figs. 30, 31)coveringjthe laminations'upon the top and bottomsurfaces, respectively, ofthe mold, are Vnext positioned thereon and .either fspot l .welded thereto Vor slipped beneathv4 said elastic bands. `Laminations I23 are next placed over those laminations covering the vertical sides of the mold.v The above-mentioned overlapping ears I|0a' (Fig. 29) areconstitutedby portions of the Y superposed laminations |I 0 and I I9.Y At the trail;

provided suitableoverlapping piecesIZIa, |.22a`

. for attachment `,to fillet member Suitable i rigidfaces of the rib mold (notshown) are pro'- vided forsustaining these overlappinglamina-r .tions during'the vulcanizing process, andfor pre'- venting the fluid pressure fro'mrmoldin'g' same in,` an incorrect position. The assembled.1amina.

tions A,are vulcanized 'to form the `completed rib abover bolt IllaA togive accessto the nut |I4b. The ribs |09 are formed an. ana1ogous`manner upon.a..wedgeshaped mold.VK Following the extraction of the rib molds from thefribs, the

common liet member is. interposed between there vulcanized, for example, by hand irons.

l The members ||3rhavingthe .U'shaped cross' sectionareinitially. formedas asingle'continuf ous piece upon a suitable moldhavinga lD-shaped cross-section. -.Af.ter vulcanizing a desired numthe afterroverlapping portions yof the ribs and' Y lber of superposed laminations thereomthe mold. is withdrawn vand slices are cut fromthe com- `a; manner that their sides are parallel.

4one piece, i. e., one piece constituted by a plurality of laminations vulcanized together upon a single mold. VHowever, dueto the shape of a fuselage |26 as shown in Fig. ,32, it is impractical to4 use. a single collapsible mold because ,of the difficulties accompanying the extraction of portions ofthe mold. Furthermore, it lmay be desirable to divide the fuselage intotwo sections in 1 order to facilitate assembly and disassembly for repair,and also to facilitate the securing of the wings in such a manner that they may be easily 'dismounted Consequently, in the form shown,

thefuselage comprises aforward section I2Ba, and an aftersection |261), the two being preferv ably mechanically joined in a telescopic engagement byumeans ofl detachable bolts |21 rat the` point of substantially maximum cross-sectional area. The fuselage is formed with a conventional cockpit having forward Windows and side windows `|26c and |2611, respectively.

Sections I26a and |26b are each formed upon a collapsible mandrel. Such a 'mandrel for the after section is shown in Fig. 33, and isanalogous inconstructionto the collapsible beam mandrel, as shown in Fig. 13,A in that it comprises a central tapering wedge |28 having a cross-section in the shape of v'a parallelogram, and having removably secured thereto members |29 and |30 which cover two sides of the wedge, the other two sides being `covered by similarv members (not shown). The side membersare grooved both transversely A and longitudinally in order that suitable frames VIn forming, for example,` the .after section |26b of theffuselage,'the side membersof the mold Vare mounteduponthewedge |28 and the mold is then vicovered" with a non-adhesive material.

Strips of veneer |31, |38, |39 "(Figs. 35 and 36) arevnext wound in the transverse grooves until i the Vgrooves are approximately rthirty per cent filled, and there held in position in a manner fsiinilar to that described in connection with the transverse framesA shown in Fig. 16. A longitudinal stiifener |40 comprising a member preferably of flexible solid wood is then placed in each of theflongitudnal grooves. Atthe point of intersection of each stiffener' withl each transverse frame, a portion ofzthestiifeneris cut away (Fig. 36)y in such a manner that a'neck |40a is formed which will permit an interlocking therewith of the laminations comprising the'transverse frames, i. e., the frames laminatlons fit closely between the shoulders adjacent the neck. The latter necessarily interrupts several ofthe laminations comprising saidframes, and in the formshown interrupts laminations |4|, I 42,-|43. Added laminations |44, |45, |46 may then be wound in the transverse grooves until flush with the outer surface of the mold.

The trailing tips of each ofthe longitudinal stiffeners may be positioned in a suitable grooveA in the conical face of a trailing conemember |41.

Following this. a series of laminations in the shape of triangular tongue pieces with rounded tips are positioned upon thel mold comprising the skin of the fuselage. Each tongue piece isplaced upon the mold with the rounded tip extending aft. The inner laminations may be temporarily held in position prior to vulcanization by spot welding 'the same to the longitudinal stiffeners and transverse frames.A Succeeding laminations may be temporarily held in place byvspot welding to the laminations therebeneath. The assembled material is vulcanized ina manner above described.

A second manner of interlockingthe longi. tudinal stiffeners to the transverse vframe members is illustrated in Fig. 37 -wherein the stieners, instead of being constituted by solid flexible members of wood, comprise a plurality of veneer strips which are interposed between alternate strips of the ltransverse frames. In assemblingthese strips-upon the mold, for example, three laminations |48, |49, |50 are first wound in the inner portion of the transverse grooves andheld in position as above set forth. A vlongitudinal stripi|5| is next positioned in a longtudinal.

groove. Strip lil interrupts the* succeeding transverse laminations |52 upon which a continuousstrip |53 is next placed. 'I'he alternate interposition of the longitudinal strips continues in this manner until both longitudinal and transverse grooves are lled. `The laminations comprising the skin are superposed .and vulcanized thereon as above described.

The forward section of the wing is formedv in an analogous manner upon the forward section of the mold and the two sections are joined in telescopic engagement by means of the bolts |21.

` In associating the fuselage and the wings, in the form shown in Fig. 32, the completed fuselage, comprising sections |26a, |26b, is joined as illustrated and a section is cut from the undery surface thereof which corresponds in longitudinal cross-sectionA to the cross'fsection of the wings. This section is represented by'the'broken line |54. 'Y

A complete port and starboard *.wing, each,.for example, having a beam member'provided with a flange 58, are assembled by boltingvsaid'flanges to one another. 'Ihe connectedport and star--l board wings are then positioned in the cut-away section of the fuselage such that said anges aref:A centrally disposed therein. A strip (not shown) having a cross-section substantially in the shape of an L, said strip being of metal or of heavy resin treated vulcanized wood laminations, is

vplaced within the fuselage adjacent the interysection of said wing and fuselage, with one face of the strip contacting the fuselageand the other the wing; Suitable boltsmay be employed for joining the faces of the strip to the wing and fuselage, thereby formingra rigid connection between the latter two members. Y

A secondl embodiment of the reinforcing means for the fuselage is illustrated in Fig. 38.'v 'I'his vfuselage is formed in two sections, each upon a collapsible mold which is analogous to that shown inFig. 33, with the exception that the grooves for the reinforcing members are cut as spirals in the vouter surface thereof. Although this fuselage isformed in two sections as above men tioned, the spiral. grooves are cut in such a manner that when the completed' sections of the fuselage are assembled, corresponding spiral ribs upon the after section will` abut corresponding -ribs upon the forward section, with the exception of those ribs which are interrupted, for example, by the section comprising the windows! spirals, in the form illustrated, is approximately` fortyper cent of the length of the fuselage, the

pitch, of course, being determined by the Vnumber of spiral grooves desired and by the 'length of the fuselage. -1

The right andleft-hand spirals intersect at various points making it necessary that the strip laminations lling the left-hand spirals be interposed between" those of the right-hand spirals in a manner similar to thatdescribed in connection with the'longitudinalstiffeners and transverse frames as shownin Fig. 37.

The skin laminations are superposed, heldin position and vulcanized upon the moldv sections as described in theformer embodiment.

The wings may be associated with this fuselage 1n a manner similarrto that described in connection withFig;v 32.

A mounting (not shown) forzan aircraft engine may be constituted by a metal tubularstructure e which is bolted to `strengthened portions of the l wing beams adjacent `their. butt extremities.`

A tail wing. (Fig. 3) with'stabinzin'g surfaces and vertical yrudder are. formed in Ya manner analogous'to that described above. f Y

There is thusprovidedzfa novel method for fabricating aircraft' from veneer layers impregnated with a thermoplastic' such' as polyvinyl butyral.` The fuselage and --wings and the component parts thereof, because of the vulcanization process, become so closely associated that a substantially'homogeneous structureA is formed which may beentirely without mechanical fastenings between any of the parts thereof. The novel method is also adapted for producing furniture, and the hulls of marine yessals, or any of :'.theirfpartsV Thelproduct of this method is extremelylight, s trong'and very inexpensive relai tive, ,to,similar .products made by other methods.

y. Furthermore, polyvinyl butyral renders the prod- ',70 .j

uct impervious `to the atmosphere, thus precluding vwarpingor separation of the veneer'layers due-to moisture entering between the layers. Alrbubbles areprevented by piercing the veneer Y sheets, and during vulcanizing, the air holes ar closed bythe thermoplastic, or a nal spray of `thermc'nplastic vvhe app Y f v, fa'aa'noolfl finish.

ed Vtc insure la j ,':Althoughlthe'present novel method has beenj Vsince a suitable thermoplastic' having similar` qualities may beV employed. y. Also, instead of wood veneer layers, suitable fabricor sheet metal: s .layers may .be used. Various changes may be.4 made inthe designvand'arrangementof the parts' ofthe structures described `herein and also .in the method for! producing these 'structures-with-r out departing fromfthelspiritjand scopeofthe invention as .the'lsamewiil now I be understoodv by those skilled in the art. `For a definition'of l the limits `of the' invention, reference will. be y L had Aprimarilylto the appended claims.

What is claimed ist LA *hollow Vstructural-'unit of la plurality *of 1 laminae of woodrv'eneerwhich is normally frangible, said` laminae being impregnated with a resin adhesive and bonded'together to formanintegral Y structure, the wood` being permanently molded into shapes Y beyondk the angle of bendingwithout fracture of saidwoodin its-normal state.

' K 2. A ho11owstructuralunitof a plurality of' laminae of wood-veneerwhichis normally frang- Aible, said lamir ae being impregnated `Witha thermoplastic binding. material comprising polyvinyl butyral and bonded .together thereby to form an 4; A structure for aircraft composed -of several hollow units, each such unit comprising a plurality'of sheets of wood veneerl bonded together with la resin adhesive, said sheets beingv molded f intdshapes beyond lthe angle `ofvbending Withoutv fracture o'f said Wood iny its normal state and intov severalplanes toxform walls abouta hollow space 1 and atleast some of saidV sheets being turned into -l'OV the sheets formingsaid walls, and means uniting a.=p1ane extending transversely 'to'.said` walls,-

thereby to form a' reinforcing angeintegral with the adjacent flanges of l.the several units-to form an integralstructure.

y 5. Astructure fork aircraft composed of several hollow units; each such unit comprising a plurality .of sheets of wood veneer bonded together Y vthin normally frangiblezlaminae of fibrous ma-v terialv forming'a hollow. shell of larger area than integral structure, the wood being-'permanently molded into shape beyond lthe `angle of bending without fracture orsaidwood'in yits normal state.H

k3..In a structure for aircraft,; a. hollow'rnembergcomprising a plurality of. sheets of'wood -ve4 neer bonded together with a. resin adhesive.' said sheets being molded into shapes beyond the angle of :bending` without fractureof'said Wood in its normal state Vand into several planes to form walls about a hollow space and at least some of saidgsheetsbeing turned into a. plane extending curved sur-face,V intersecting reinforcing members'y ,at the inner vsurface of said shell, `said members `with athermoplastic adhesive; said sheets being molded into `shapesbeyond the anglefof bending without fracture of said wood in'itsnormal state and into several planes toformwalls about a hollowspace and at least some of said sheets beingturned into a plane extending transversely. to

said fwalls,thereby to forma reinforcing ange' integralwlththe sheets forming said walls, and means uniting the adjacent'flanges of the several unitstoiform an integral'. structure.

i 6.-;A .molded laminated :structure `comprising any ofthe' individual laminae, and geodetic type reinforcing members at the inner surface of said shell, said members and said laminaev being unitedand securely bonded together over the entire contactingareas thereof by a resin adhesive which .sets (atf a .temperaturev below that at which burning of thejmaterial in its thin laminar form would normally occur.

7.Thestructurexof claim 6, said shell having a `double curved surface.

fs. la molded mmmated airpiane fuselage com!l prising thinnormallyffrangible sheets of brous material forming a hollowvshell having a double beingintercalated, and `said members A`and said transversely to said walls, thereby to form `a rein'- forcing flange integral; with :the sheets formingsaidwalls."1f`, :w

sheets being united and securely bonded together overV I the entire contacting areas: thereof by a .resin'adhesive which sets ata temperaturebelow thatat whichburning of the material in-its thin sheet formwould normally occur. 1, Y l

Y EUGENE L. VIDAL.

LAURENCE J. MARHQEEER -1 ria.

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