Patent Publication Number: US-2009224107-A1

Title: Reduced Span Wings with Wing Tip Devices, and Associated Systems and Methods

Description:
TECHNICAL FIELD 
     The following disclosure relates generally to reduced span wings with wing tip devices, and associated systems and methods. 
     BACKGROUND 
     The idea of using winglets to reduce induced drag on aircraft wings was studied by Richard Whitcomb of NASA and others in the 1970s. Since then, a number of variations on this idea have been patented (see, for example, U.S. Pat. No. 4,205,810 to Ishimitsu and U.S. Pat. No. 5,275,358 to Goldhammer, et al.). In addition, a number of tip device variations are currently in service. Such devices include horizontal span extensions and aft-swept span extensions canted upward or downward at various angles. These devices can be added to a new wing during the initial design phase of an all-new aircraft, or they can be added to an existing wing as a retrofit or during development of a derivative model. 
     The induced drag of a wing or a wing/winglet combination can be calculated with reasonable accuracy using the classic “Trefftz plane theory.” According to this theory, the induced drag of an aircraft wing depends only on the trailing edge trace of the “lifting system” (i.e., the wing plus tip device), as viewed directly from the front or rear of the wing, and the “spanload.” The spanload is the distribution of aerodynamic load perpendicular to the trailing edge trace of the wing. Aerodynamicists often refer to this aerodynamic load distribution as “lift,” even though the load is not vertical when the trailing edge trace is tilted from horizontal. Adding a winglet or other wing tip device to a wing changes both the trailing edge trace (i.e., the “Trefftz-plane geometry”) and the spanload. As a result, adding such a device also changes the induced drag on the wing. 
     For a given Trefftz-plane geometry and a given total vertical lift, there is generally one spanload that gives the lowest possible induced drag. This is the “ideal spanload,” and the induced drag that results from the ideal spanload is the “ideal induced drag.” For a flat wing where the Trefftz-plane geometry is a horizontal line, the ideal spanload is elliptical. Conventional aircraft wings without winglets are close enough to being flat in the Trefftz-plane that their ideal spanloads are very close to elliptical. For conventional aircraft wings having vertical or near-vertical winglets (i.e., nonplanar lifting systems), the ideal spanload is generally not elliptical, but the ideal spanload can be easily calculated from conventional wing theory. 
     Conventional aircraft wings are generally not designed with ideal or elliptical spanloads. Instead, they are designed with compromised “triangular” spanloads that reduce structural bending loads on the wing. Such designs trade a slight increase in induced drag for a reduction in airframe weight. The degree of compromise varies considerably from one aircraft model to another. To produce such a triangular spanload, the wing tip is typically twisted to produce “washout.” Washout refers to a wing that twists in an outbound direction so that the trailing edge moves upward relative to the leading edge. Washing out the wing tip in this manner lowers the angle of attack of the wing tip with respect to the wing root, thereby reducing the lift distribution toward the wing tip. 
     Designing a new wing and developing the associated tooling for a new wing is an expensive undertaking. Accordingly, some aircraft manufacturers develop derivative wing designs that are based at least in part on an initial design. While such designs can be less expensive to develop, they typically include at least some performance compromises. Accordingly, there remains a need for improved, cost-effective wing development processes. 
     SUMMARY 
     The present disclosure is directed generally to reduced span wings with wing tip devices, and associated systems and methods. A method for designing a wing in accordance with a particular embodiment includes establishing a target lift value for a winglet to be attached to a wing, with the wing having a wing root, a wing tip, and a twist distribution that results in a loading at the wing tip that is less than a target loading level. For example, the twist distribution can result in a washout at the wing tip that is less than a target washout level, resulting in a loading at the wing tip that is above a target loading level. The method further includes selecting a planform shape of the winglet to produce less of an increase in loading at the wing tip compared to the wing tip loading produced by other winglet planform shapes having the same target lift value. For example, in a further particular embodiment, selecting a planform shape includes selecting a planform shape that produces a minimal loading increase at the wing tip when compared with all other planform shapes having the same target lift value. 
     Another aspect of the disclosure is directed to an arrangement of wings for aircraft of different sizes, and includes a first wing having a first wing span, a first twist distribution, a first root, a first tip, and a target location between the first root and the first tip. The arrangement further includes a second wing corresponding in part to the first wing and having a second root and a second tip. The second wing further includes a second twist distribution between the second root and the second tip that is generally identical to the first twist distribution between the first root and the target location. The second wing further includes a winglet at the second tip. 
     In a further particular aspect of the foregoing arrangement, the winglet is the second of two winglets. The first wing has a first winglet, with a sweep angle of the second winglet relative to the second wing greater in an aft direction than is a sweep angle of the first winglet relative to the first wing. 
     Still a further aspect of the disclosure is directed to a method for manufacturing an arrangement of wings, and includes using a wing-forming tool to manufacture a first wing having a first root, a first tip, a target location between the first root and the first tip, a first span, and a first spanwise twist distribution. The method further includes using the same wing-forming tool to manufacture a second wing having a second root, a second tip, a second span less than the first span, and a second spanwise twist distribution between the second root and the second tip that is generally identical to the first spanwise twist distribution between the first root and the target location. The method further includes connecting a winglet to the second wing at the second tip. In further particular embodiments, using the wing-forming tool can include laying up a composite structure over a first spanwise portion of the tool for the first wing, and laying up a composite structure over a second spanwise portion of the tool, less than the first spanwise portion of the tool, for the second wing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partially schematic, isometric illustration of an aircraft having wings and wing tip devices configured in accordance with an embodiment of the disclosure. 
         FIG. 2  is a partially exploded, detailed illustration of a wing and winglet shown in  FIG. 1 . 
         FIG. 3A  is a plan view of a wing and corresponding winglet in accordance with an embodiment of the disclosure. 
         FIG. 3B  is a graph illustrating twist angle/washout as a function of span for a wing and a baseline wing in accordance with an embodiment of the disclosure. 
         FIGS. 4A-4B  are flow diagrams illustrating methods for designing wings in accordance with embodiments of the disclosure. 
         FIG. 5  is a graph illustrating span load as a function of span for a variety of wings in accordance with an embodiment of the disclosure. 
         FIG. 6  is a plan view of a wing and an unfolded winglet in accordance with an embodiment of the disclosure. 
         FIGS. 7A-7B  illustrate representative chord-wise locations for winglets in accordance with embodiments of the disclosure. 
         FIG. 8  illustrates several cant orientations for winglets in accordance with embodiments of the disclosure. 
         FIG. 9  is a flow diagram illustrating a method for manufacturing a wing in accordance with an embodiment of the disclosure. 
         FIGS. 10A-10B  illustrate tools for manufacturing wings in accordance with an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure describes reduced span wings with wing tip devices, and associated systems, arrangements and methods. Certain specific details are set forth in the following description and in  FIGS. 1-10B  to provide a thorough understanding of various embodiments of the invention. Other details describing well-known structures and systems often associated with aircraft and aircraft wings are not set forth in the following description to avoid unnecessarily obscuring the description of the various embodiments of the invention. 
     Many of the details, dimensions, angles, and other specifications shown in the Figures are merely illustrative of particular embodiments. Accordingly, other embodiments can have other details, dimensions, and specifications without departing from the present disclosure. In addition, other embodiments may be practiced without several of the details described below. 
       FIG. 1  is a top isometric view of an aircraft  100  having a wing/winglet combination  105  configured in accordance with an embodiment of the disclosure. In one aspect of this embodiment, the aircraft  100  includes an airfoil such as a wing  104  extending outwardly from a fuselage  102 . The fuselage  102  can be aligned along a longitudinal axis  101  and can include a passenger compartment  103  configured to carry a plurality of passengers (not shown). In one embodiment, the passenger compartment  103  can be configured to carry at least 50 passengers. In another embodiment, the passenger compartment  103  can be configured to carry at least 150 passengers. In further embodiments, the passenger compartment  103  can be configured to carry other numbers of passengers. In still other embodiments (such as military embodiments), the passenger compartment  103  can be omitted or can be configured to carry cargo. 
     In a particular embodiment, the wing  104  can have a span that is reduced when compared to the span of a baseline wing  104   a , which is shown schematically in dashed lines in  FIG. 1 . The wing  104  can be based to a large degree on the baseline wing  104   a  and can accordingly have several characteristics in common with the baseline wing  104   a , as will be discussed in further detail later. As will also be discussed in further detail later, winglets  110  can be added to the wing  104  and can be particularly selected and/or configured to offset potential performance inefficiencies resulting from the differences between the wing  104  and the baseline wing  104   a  upon which it is based. 
     In some cases, the baseline wing  104   a  includes a baseline winglet, and in other cases, the baseline wing  104   a  has no winglet. In either case, the winglets  110  provided for the wing  104  can be sized, shaped and installed in a manner that accounts for the reduced span of the wing  104 . For example, in one embodiment, the winglets  110  can be retrofitted to the wing  104  to reduce the impact on wing lift and/or drag caused by reducing the wing span. In another embodiment, the winglets  110  can be incorporated into the design of a new derivative aircraft that utilizes an existing wing configuration. In either case, the design of the winglet  110  can improve the efficiency of an aircraft having a reduced-span wing  104 , without requiring the entire wing to be re-designed. 
     Although the winglet  110  of the illustrated embodiment is combined with a wing, in other embodiments, the winglet  110  can be combined with other types of airfoils to reduce aerodynamic drag and/or serve other purposes. For example, in one other embodiment, the winglet  110  can be combined with an aft-mounted horizontal stabilizer. In another embodiment, the winglet  110  can be combined with a forward-wing or canard to reduce the aerodynamic drag on the canard. In further embodiments, the winglet  110  can be combined with other airfoils. Furthermore, throughout this disclosure and the following claims, the term “winglet” shall refer generally to a wing tip device configured in accordance with this disclosure. In particular embodiments, the winglets can be vertical. In other embodiments, the winglets can be canted from the vertical, and in still further embodiments, the winglets can include horizontal span extensions. As will be described later, embodiments in which the winglets are vertical or at least canted up (or down) from horizontal can be particularly useful for reducing space occupied by the aircraft  100  at an airport gate. 
     In a further aspect of an embodiment shown in  FIG. 1 , the wing  104  has a wing quarter-chord line  114  that is swept at least generally aft relative to the longitudinal axis  101 , and the winglet  110  has a winglet quarter-chord line  112  that is swept further aft relative to the wing quarter-chord line  114 . As described in greater detail below, sweeping the winglet quarter-chord line  112  aft in this manner can favorably change the spanload on the combination of the wing  104  and the winglet  110  to provide an increased drag reduction when compared with the wing  104  without the winglet  110 , and/or when compared with a winglet  110  that is not properly configured. 
       FIG. 2  is an enlarged exploded isometric view of the wing/winglet combination  105  of  FIG. 1 , configured in accordance with an embodiment of the disclosure. In one aspect of this embodiment, the wing  104  includes a wing tip portion  238  and a wing root portion  236 . The wing root portion  236  can be configured to be fixedly attached to the fuselage  102  ( FIG. 1 ) and can define a wing root chord  256 . The wing tip portion  238  can define a wing tip chord  258  offset laterally from the wing root chord  256  along the wing quarter-chord line  114 . The wing tip chord  258  can have a washout twist (e.g., a downward twist) relative to the wing root chord  256 , as illustrated by the twist angle  259 . Such washout twist is provided to reduce the lift distribution toward the wing tip and in turn reduce the bending load on the wing. Reducing the bending load on the wing can favorably reduce the structural weight of the wing  104 , albeit at the expense of a slight drag increase. 
     In another aspect of this embodiment, the winglet  110  includes a winglet tip portion  218  and a winglet root portion  216 . The winglet root portion  216  can be configured to be fixedly attached to the wing tip portion  238  of the wing  104  and can define a winglet root chord  226 . The winglet tip portion  218  can similarly define a winglet tip chord  228  offset from the winglet root chord  226  along the winglet quarter-chord line  112 . In a further aspect of this embodiment described in greater detail below, the winglet quarter-chord line  112  is swept aft relative to the wing quarter-chord line  114  to favorably change the spanload on the wing  104  and in turn reduce the induced drag on the wing  104 . 
     In yet another aspect of this embodiment, the wing  104  includes a wing leading edge portion  262  and a wing trailing edge portion  263 . Similarly, the winglet  110  can include a winglet leading edge portion  242  and a winglet trailing edge portion  243 . In the illustrated embodiment, the winglet  110  is a full-chord winglet with the winglet leading edge portion  242  positioned at least proximate to the wing leading edge portion  262 , and the winglet trailing edge portion  243  positioned at least proximate to the wing trailing edge portion  263 . In other embodiments described in greater detail later, partial-chord winglets configured in accordance with other embodiments of the disclosure can be fixedly attached to the wing  104  such that the winglet leading edge portion  242  and/or the winglet trailing edge portion  243  are/is offset from the corresponding wing leading edge portion  262  and/or the wing trailing edge portion  263 , respectively. 
     In a further aspect of this embodiment, the wing  104  can have a generally trapezoidal planform with an aspect ratio of about 10 and a taper ratio of about 0.25. In other embodiments, the wing  104  can have other aspect ratios and other taper ratios. For example, in one other embodiment, the wing  104  can have an aspect ratio greater than 10 and/or a taper ratio greater than 0.25. In another embodiment, the wing  104  can have an aspect ratio less than 10 and/or a taper ratio less than 0.25. In a further aspect of this embodiment, the wing quarter-chord line  114  can be swept aft at an angle  291  of about 35 degrees with respect to the longitudinal axis  101 . In other embodiments, the wing quarter-chord line  114  can be positioned at other angles relative to the longitudinal axis  101 . For example, in one other embodiment, the wing  104  can be at least generally unswept. In yet another embodiment, the wing  104  can be swept forward. 
     In the illustrated embodiment of  FIG. 2 , the winglet  110  can have a length of about 15% of the semi-span of the wing  104  and a taper ratio of about 0.50. In addition, in this embodiment, the winglet quarter-chord line  112  can be swept aft at an angle  292  of about 35 degrees with respect to the wing tip chord  258 . In other embodiments, the winglet  110  can have other lengths, other taper ratios, and other sweep angles. For example, in one other embodiment, the winglet  110  can have a length of about 10% of the semi-span of the wing  104 , a taper ratio of about 0.40, and an aft sweep angle of about 25 degrees with respect to the wing tip chord  258 . 
       FIG. 3A  is plan view illustration of the wing  104  and the baseline wing  104   a  shown in  FIG. 1 , along with the winglet  110  configured in accordance with an embodiment of the disclosure. As shown in  FIG. 3A , the wing  104  can have a shorter span than the baseline wing  104   a , but can share other aspects with the baseline wing  104   a . For example, in a particular embodiment, the wing  104  and the baseline wing  104   a  can have generally the same planform shape, up to a target location  350 . The span of the wing  104  may be less than the span of the baseline wing  104   a  to allow the wing to be used with a smaller aircraft fuselage  101  ( FIG. 1 ) and allow the aircraft to occupy less space at an airport gate. In a particular embodiment, the twist angle or washout of the wing  104  can be the same as that of the baseline wing  104   a , up to the target location  350 , as is shown in  FIG. 3B .  FIG. 3B  is a graph illustrating the twist angle or washout of the wings as a function of span. Line  370  indicates that the twist angle distribution for both the wing  104  and the baseline wing  104   a  are the same up to the target location  350 . Outboard of the target location  350 , line  370   a  indicates the twist angle distribution of the baseline wing  104   a  continuing outward in a spanwise direction. For purposes of illustration, the twist angle distribution is shown as a linear function of span in  FIG. 3B . In other embodiments, the twist angle distribution may be non-linear and/or non-monotonic. 
     As is also shown in  FIG. 3B , the baseline wing  104   a  has a target twist or washout level  371  at its outboard-most location, while the wing  104  has a resulting twist or washout level  372  at its outboard-most location that is less than the target twist level  371 . Because the resulting twist or washout level  372  is less than the target twist or washout level  371 , the wing  104  may have performance aspects that are less than optimal and/or otherwise amenable to improvement. By selectively configuring the winglet  110 , some or all of the performance loss resulting from using a wing  104  having a twist angle distribution sized for a larger span wing (e.g., the baseline wing  104   a ) can be regained. In particular, because the resulting twist level  372  of the wing  104  is less than the target twist level  371 , the wing tip of the wing  104  may be more heavily loaded than the target loading level. The characteristics of the winglet  110  can be selected to produce less of an increase in the loading at the wing tip when compared to a conventional winglet, in order to compensate for this effect. 
       FIG. 4A  is a flow diagram illustrating a process  480   a  for designing a wing in accordance with a particular embodiment of the disclosure. The process  480  can include establishing a target lift value for a winglet that is to be attached to a wing (process portion  481 ). The target lift value can be selected based on the degree to which the designer wishes the winglet to reduce wing tip loading when compared to the loading produced by a conventional winglet. The wing includes a wing root, a wing tip, and twist distribution that results in a loading at the wing tip that is higher than a target loading level. For example, as discussed above with reference to  FIGS. 3A and 3B , the twist of the wing at the wing tip may be less than optimal, resulting in higher loading at the wing tip. Process portion  482  includes selecting a planform shape of the winglet to produce less of an increase in the loading at the wing tip compared to the wing tip loading produced by other winglet planform shapes having a same target lift value. For example, process portion  482  can include a direct calculation to identify an optimum or at least improved planform shape that produces less of an increase in wing loading at the wing tip, when compared to conventional winglets. In other embodiments, process portion  482  can include an iterative process at which an initial planform shape is selected and evaluated (e.g., using conventional aerodynamic calculation tools), and then adjusted until an optimum or at least improved wing tip loading results. In either of these embodiments, the planform shape of the winglet refers generally to the shape of the winglet projected onto a plane generally parallel to the major surfaces of the winglet. 
       FIG. 4B  illustrates a more detailed process  480   b  for carrying out an embodiment of the method described above with reference to  FIG. 4A . Some or all of the processes shown in  FIGS. 4A and 4B  may be carried out automatically, e.g., by instructions contained in a computer-readable medium and executed by a computer or other automated device. As shown in  FIG. 4B , the process  480   b  can include identifying a wing having a wing tip loading greater than a target value (process portion  483 ). In process portion  484 , the process includes developing a proposed winglet having a target winglet loading. This can include developing a planform shape (e.g., a wetted area, leading edge sweep angle, trailing edge sweep angle, etc.), as shown in process portion  485 , and developing further design parameters (e.g., toe-in angle, cant angle, chord wise location, etc.), as is shown in process portion  486 . Process portion  487  includes evaluating wing tip loading and overall drag for the wing/winglet system. In process portion  488 , the wing tip loading is compared to a desired loading level. The desired level can be a level less than for other winglet designs developed during an iterative process, and/or it can be a minimum level based on a variety of other winglet designs. For example, the desired level can correspond to a minimal loading increase at the wingtip when compared with all other planform shapes having the same target lift value. In either embodiment, if the wing tip loading is at the desired level, the process ends. If not, then the planform shape and/or further design parameters are updated (via process portions  485  and/or  486 ) and the updated design is evaluated. 
       FIG. 5  is a graph illustrating spanload as a function of eta, a non-dimensionalized arc length value along the span of a wing. Curve  551  illustrates the ideal span load for minimum induced drag of a wing having a vertical winglet. Curve  552  illustrates a representative “best” spanload distribution for a wing that has too little washout (e.g., the wing  104  shown in  FIG. 3A ), with a conventional vertical winglet planform. In this particular embodiment, the conventional winglet planform has a sweep angle that is comparable to the sweep angle of the wing at the wing tip, and has a chord length that is approximately the same as the chord length of the wing at the wing tip. Curve  553  illustrates a representative span load resulting from carrying out the method  480  described above with reference to  FIG. 4 , e.g., selecting a planform shape of the winglet to produce a reduced loading at the wing tip, compared with the loading produced by the conventional winglet planform and identified by line  552 . In a particular aspect of this embodiment, the improved or best available spanload results from sweeping the winglet further aft than the sweep angle of a conventional winglet, and/or shifting the winglet further aft relative to the position of a conventional winglet. Further illustrations of representative winglets having these characteristics are described later with reference to  FIGS. 6-8 . 
     The curves shown in  FIG. 5  are based on induced drag values. When a wing has too little washout, however, induced drag may not be the only aerodynamic consideration. For example, shock drag and/or viscous drag of the local airfoil sections can increase significantly as a result of the reduced washout. Accordingly, while the designer may use a graph like that shown in  FIG. 5  to determine the progress toward reducing or eliminating the additional induced drag resulting from a wing having too little washout, the designer may use a similar graph (or other technique) to determine how the variation in winglet planform shape affects shock drag and/or viscous drag, in addition to or in lieu of assessing induced drag. For example, the designer can develop a composite drag number that includes induced drag, shock drag and viscous drag for determining the level of improvement resulting from different planform shapes, or the designer can identify one or more dominant drag contributors and focus the design efforts on reducing the drag contribution from that/those contributor(s) alone. 
       FIG. 6  is an unfolded top plan view of the wing/winglet combination  105  of  FIG. 2  illustrating the relative sweep angles of the wing quarter-chord line  114  and the winglet quarter-chord line  112  in accordance with an embodiment of the disclosure. For purposes of illustration, the winglet  110  is folded outward and downward in  FIG. 3  about the wing tip chord  258  so that it lies in the same plane as the wing  104 . This unfolded configuration illustrates that the winglet quarter-chord line  112  is swept aft with respect to the wing quarter-chord line  114 , as shown by an aft sweep angle  693 , and by an aft relative sweep angle  694 . Accordingly, the winglet quarter-chord line  112  is swept further aft than that of a conventional winglet, which is typically swept by the same amount as the wing. In some embodiments (e.g., if the wing  104  has a significant forward sweep), the quarter-chord line of the winglet  112  may actually be swept forward relative to the longitudinal axis  101 , but the winglet  110  may still be swept aft relative to the wing quarter-chord line  114 . 
     Once the planform shape of the winglet is established, the designer may use additional techniques to further compensate for the reduced wing tip washout, and/or other causes of high wing tip loading. For example, as shown in  FIG. 7A , the winglet  110  can have an aft location relative to the wing tip portion  238  such that the winglet quarter chord line  112  is located aft of the wing quarter chord line  114 . In a particular aspect of this embodiment, the winglet trailing edge portion  243  can align with the wing trailing edge portion  263 . In another embodiment, shown in  FIG. 7B , the winglet trailing edge portion  243  can be offset in an aft direction relative to the wing trailing edge portion  263 . The particular location of the winglet  110  relative to the wing tip  238  (in a chord-wise direction) can depend upon the particular geometry of the wing  104  and an evaluation of other parametric variables, e.g., a trade between drag reduction to be achieved by the winglet  110  and a weight increase resulting from the winglet  110 . 
       FIG. 8  is an enlarged rear elevation view of the winglet  110  of  FIG. 2  configured in accordance with an embodiment of the disclosure. In one aspect of this embodiment, the winglet  110  extends at least generally upwardly with respect to the wing  104  such that the winglet  110  is at least generally perpendicular to the wing  104 . In other embodiments, the winglet  110  can extend at other angles with respect to the wing  104 . For example, in one other embodiment, as shown by a first phantom position  860   a , the winglet  110  can extend at least generally outwardly from the wing  104  in a horizontal direction, though in this case, the winglet would generally be considered a wing extension. In another embodiment, as illustrated by a second phantom position  860   b , the winglet  110  can extend at least generally upward and inward with respect to the wing  104 . In a further embodiment, as illustrated by a third phantom position  860   c , the winglet  110  can extend at least generally downward and inward with respect to the wing  104 . In other embodiments, the winglet  110  can assume a range of different cant angles between the second position  860   b  and the third position  860   c . Such cant angles can depend on a number of factors, including, for example, mitigating transonic shock interaction, reducing structural loads, and/or optimizing the reduction of aerodynamic drag. In general, if the wing  104  is selected for its short span (e.g., so as to more easily fit into airport gate locations), it is expected that upward or downward cant angles will be preferred to the horizontal orientation. 
       FIG. 9  is a flow diagram illustrating a process  980  for manufacturing wings in a system of wings in accordance with an embodiment of the disclosure. Process portion  982  includes using a wing-forming tool to manufacture a first wing having a first root, a first tip, a target location between the first root and the first tip, a first span, and a first spanwise twist distribution. Process portion  984  includes using the same wing-forming tool to manufacture a second wing. The second wing has a second root, a second tip, a second span less than the first span, and a second spanwise twist distribution. The second spanwise twist distribution, between the second root and the second tip, is generally identical to the first spanwise twist distribution between the first root and the target location. Process portion  986  includes connecting a winglet to the second wing at the second tip. 
       FIGS. 10A and 10B  illustrate, in partially schematic format, tools for forming wings in accordance with the process described above with reference to  FIG. 9 . For example,  FIG. 10A  illustrates a lay-up tool  1030  that can be used to form both the first wing described above with reference to  FIG. 9  (e.g., the baseline wing  104   a  shown in  FIG. 1 ) and the second wing described above with reference to  FIG. 9  (e.g., the wing  104  shown in  FIG. 1 ). In particular, a first wing skin can be laid up using the entire spanwise extent of the lay-up tool  1030 . When forming the skin for the second wing, the lay-up surfaces of the tool only up to the target location  350  are used. In a similar manner, the wing box assembly tool  1032  shown in  FIG. 10B  can have its entire spanwise extent used when forming the first wing, and, when the second wing is formed, only the portion of the wing box assembly tool  1032  extending outwardly to the target location  350  can be used. 
     One feature of at least some of the foregoing embodiments is that they can include designing and/or manufacturing wings having a reduced span using designs and/or manufacturing processes developed for a baseline wing having a larger span. As a result, the new or modified wing need not be developed from scratch, but can instead take advantage of existing designs and tooling for much of its development. This can result in a significant savings in the cost of developing and manufacturing a new aircraft wing. For example, in a particular instance, it may be desirable to take advantage of an existing wing design when developing a lower capacity aircraft, e.g., an aircraft having a smaller fuselage and/or take-off gross weight (TOGW). In order to meet tight airport gate parking restrictions, it may be desirable to reduce the span of the wing for such an aircraft. Using the foregoing techniques, such a wing can be developed and manufactured without starting from scratch. 
     As was also discussed above, merely “cutting off” an existing wing design at a less than full-span location may produce a wing having a performance level less than is desired. In particular, this design approach can result in the tip of the wing having less twist than it was designed for. However, by sizing and shaping a winglet in accordance with the foregoing embodiments, the potential decrease in performance can be at least partially (and in some cases, completely) recouped. Accordingly, embodiments of the winglet design process described above can significantly increase the feasibility of using an existing wing design to develop a reduced-span wing. 
     From the foregoing, it will be appreciated that specific embodiments of the disclosure have been described herein for purposes of illustration, but that various modifications may be made without deviating from the disclosure. For example, the particular wings and winglet geometries shown and described above, and the particular aircraft on which they are installed, may have different configurations in other embodiments. Certain aspects of the disclosure described in the context of particular embodiments may be combined or eliminated in other embodiments. For example, the various cant angles shown in  FIG. 8  may be combined with any of the various winglet locations described with reference to  FIGS. 7A and 7B . Further, while advantages associated with certain embodiments have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the invention. Accordingly, the disclosure can include other embodiments not specifically shown or described above.