[0001]    This application claims priority to U.S. PROVISIONAL Application Ser. No. 62/236,884, filed Oct. 3, 2015, and is a continuation-in-part of U.S. application Ser. No. 14/993,599, filed Jan. 12, 2016, the disclosures of which are hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention generally relates to a projectile weapon, and more particularly to an arrow with aligning features for the nock and/or the head. 
       BACKGROUND OF THE INVENTION 
       [0003]    In general, it is known to construct an arrow  10  to include a shaft  12 , a head  14  attached to or positioned at a front of the shaft  12 , fletchings  16  positioned near a rear end of the shaft  12 , and a nock  18  on the rear end of the shaft  12 , as illustrated in  FIG. 1 . 
         [0004]    Normally, the shaft  12  is round in cross-section. The head  14  may attach thereto and may be configured to strike or pierce a target upon the arrow  10  being fired from a projectile firing device, such as a bow or a crossbow (not pictured). Connection between the head  14  and the shaft is normally accomplished by inserting at least a portion of the head within an aperture, receiver, or otherwise hollow portion of the shaft  12 . The connection may be a friction fit, may be threaded, or may include the use of an adhesive. 
         [0005]    The arrow  10  may include three fletchings  16 , which may be positioned equidistantly around a circumference of the shaft  12 . The fletchings  16  are adapted to act as airfoils and stabilize the arrow during flight. The nock  18  may attach to the shaft  12  and may include a bowstring receiver (such as in the form of a notch or groove) for aligning the bowstring with the arrow in order to initiate flight. Connection between the nock  18  and the shaft  12  is normally accomplished via insertion of at least a portion of the nock  18  into the shaft  12 . As with the head, the connection between the nock  18  and the shaft  12  may be a friction fit, may be threaded, or may include the use of an adhesive. 
         [0006]    Alignment between the nock  18  and the shaft  12  is important, as this alignment is responsible for the relative position of the arrow  10  and the bow when the arrow is shot. If the nock is not properly aligned, then one or more fletchings  16  may contact the bow as the arrow is released, thereby affecting the trajectory and/or speed of the arrow during flight. 
         [0007]    Similarly, alignment of the head  14  with the shaft  12  may be important, especially in the case of broadhead, which may include three blades. Specifically, alignment of the blades of the broadhead with the fletchings  16  may lend to a straight trajectory during flight. 
         [0008]    Current methods of alignment between the nock and the shaft and/or between the head and the shaft include a simple visual inspection of alignment, or may include some form of a reference point for alignment. For instance, the shaft  12  and/or the nock  18  or head  14  may include a marking or a ridge for indicating an appropriate alignment configuration. However, these manual alignment methods are prone to user error in alignment, and allow for twisting, turning, and working loose of the nock and/or head through normal use. 
         [0009]    Accordingly, a need has been identified for an arrow with an improved alignment system which addresses these and other shortcomings of traditional arrows. 
       SUMMARY OF THE INVENTION 
       [0010]    In one embodiment, the present invention generally relates to an arrow with self-aligning features comprising a shaft including a rounded polygonal cross-section and a removable nock including a cross-section matching the rounded polygonal cross-section of the shaft and adapted to engage the shaft along the rounded polygonal cross-section, thereby preventing relative rotation therebetween. 
         [0011]    In one aspect, the rounded polygonal cross-section may comprise a reuleaux triangle. The shaft may include an aperture in the shape of a reuleaux triangle, and the nock may include a projection in the shape of a reuleaux triangle adapted for insertion into the aperture. 
         [0012]    The arrow may further include a plurality of fletchings attached to the shaft, each of the fletchings positioned at a midpoint between two corners of the rounded polygonal cross-section. 
         [0013]    The rounded polygonal cross-section may extend over various lengths of the shaft. For example, it may extend along an entire length of the shaft. Alternately, the cross-section may extend only along an end of the shaft adjacent the engagement of the nock. 
         [0014]    In one aspect, the rounded polygonal cross-section may extend along at least a portion of the shaft opposite an end of the shaft adjacent the engagement of the nock. The arrow may further include a head comprising a cross-section matching the rounded polygonal cross-section of the shaft and adapted to engage the portion of the shaft opposite the end of the shaft adjacent the engagement of the nock. 
         [0015]    In another aspect, the arrow may include a connector for connecting a head to the shaft, wherein the connector comprises a cross-section matching the rounded polygonal cross-section of the shaft and adapted to engage the portion of the shaft opposite the end of the shaft adjacent the engagement of the nock. The connector may comprise an aperture for engaging the head. In another aspect, the connector may comprise a projection for engaging the head. The connector may include one or more fasteners adapted to lock the head in position relative to the shaft. 
         [0016]    In a further embodiment, an arrow with self-aligning features includes a shaft with a first end and a second end, said shaft including a first aperture at the first end and a second aperture at the second end, wherein the first aperture and the second aperture each comprise a reuleaux triangular shape, and a removable nock including a first extension with a reuleaux triangular cross-sectional shape, wherein the first aperture is adapted to receive the first extension, thereby preventing relative rotational movement between the shaft and the nock. 
         [0017]    The arrow may further include a head comprising a second extension with a reuleaux triangular cross-sectional shape, wherein the second aperture is adapted to receive the second extension, thereby preventing relative rotational movement between the shaft and the head. 
         [0018]    In one aspect, the arrow may further include a connector with a reuleaux triangular cross-sectional shape, wherein the second aperture is adapted to receive the connector, thereby preventing relative rotational movement between the shaft and the connector. The arrow may further include a head adapted to engage the connector, wherein the connector includes a receiver adapted to receive at least a portion of the head, and a fastener adapted to lock the head in position with respect to the connector. 
         [0019]    In another aspect, the arrow may further include a head adapted to engage the connector, said head including a receiver and a fastener, wherein the connector includes a second extension, and wherein the receiver is adapted to receive the second extension, and wherein the fastener is adapted to lock the head in position with respect to the connector. 
         [0020]    In a further embodiment of the present invention, an arrow with self-aligning features for use with an archery weapon including a string is disclosed. The arrow may comprise a shaft including an end with a reuleaux triangular cross-section, a plurality of fletchings attached to the shaft, at least one of said fletchings comprising an index vane, and a removable nock including a cross-section matching the reuleaux triangular cross-section of the shaft and adapted to engage the shaft along the reuleaux triangular cross-section of the shaft and the nock, and the nock further including a notch adapted to engage the string along a longitudinal length of the notch, wherein engagement of the shaft and the nock establishes a fixed relative angular position between the longitudinal length of the notch and the index vane. In one aspect, the relative angular position between the longitudinal length of the notch and the index vane may be 90 degrees. Alternately, the relative angular position may be zero degrees. 
         [0021]    A further embodiment of the present invention relates to an arrow comprising a shaft spanning a longitudinal length from a first end of the shaft to a second end of the shaft, said shaft including an interior bore spanning at least a portion of said longitudinal length, wherein the interior bore includes a non-circular cross sectional shape. 
         [0022]    In one aspect, the non-circular cross sectional shape may comprise a rounded polygon. The rounded polygon may be a reuleaux triangle. In another aspect, the rounded polygon may be a rounded pentagon. 
         [0023]    The non-circular cross sectional shape may take the form of a triangle or a triangle with rounded corners. 
         [0024]    The interior bore may extend from the first end of the shaft to the second end of the shaft. Alternatively, the interior bore may extend along a portion of the shaft less than the longitudinal length of the shaft. 
         [0025]    The shaft may further include an exterior cross-sectional shape that is geometrically similar to the cross-sectional shape of the interior bore. In another aspect, the shaft further includes a circular exterior cross-sectional shape. 
         [0026]    In another embodiment, an arrow may include a shaft adapted to engage an arrowhead at a first end of the shaft and a nock at the second end of the shaft, said shaft defined by a wall including an exterior surface and an interior surface, said interior surface defining an interior bore within the shaft, wherein the interior bore includes a cross section in the shape of a rounded polygon. 
         [0027]    In one aspect, the exterior surface may define a cross section in the shape of a circle. The interior bore may be a reuleaux triangle, a triangle, a triangle with rounded corners, a rounded pentagon, or another rounded polygon with an odd number of sides. The interior bore may extend along the full length of the shaft, or may extend only along a portion of the length of the shaft. 
         [0028]    The exterior surface may include at least one mark aligning with a vertex of the rounded polygon. The exterior surface may include at least one mark aligning with a midpoint of a side of the rounded polygon. 
         [0029]    In another aspect, the exterior surface may define a cross section in the shape of a rounded polygon. The exterior surface and the interior surface may define geometrically similar rounded polygons in cross section. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]      FIG. 1  is a general arrow of the prior art; 
           [0031]      FIGS. 2A-2D  illustrate the arrow shaft of the present invention with a reuleaux triangular cross-section; 
           [0032]      FIGS. 3A-3J  illustrate cross-sections of the shaft according to different embodiments; 
           [0033]      FIGS. 4A-4B  illustrate engagement between the nock and the shaft; 
           [0034]      FIGS. 5A-5B  illustrate engagement between an arrow head and the shaft; 
           [0035]      FIGS. 6A-6B  illustrate engagement between an arrow head and the shaft with the use of a connector; 
           [0036]      FIG. 7  is a cross section of the arrow with fletchings; 
           [0037]      FIG. 8  illustrates the engagement between a link for connecting the arrow head and the shaft; 
           [0038]      FIG. 9  illustrates the engagement between an alternate link for connecting the arrow head and the shaft; 
           [0039]      FIGS. 10A and 10B  are plan views of different embodiments of a collar associated with the link of either of  FIG. 8 or 9 ; and 
           [0040]      FIGS. 11A and 11B  illustrate arrow heads for use with the link of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]    The description provided below and in regard to the figures applies to all embodiments unless noted otherwise, and features common to each embodiment are similarly shown and numbered. 
         [0042]    The device of the current invention relates to an arrow  10  including a shaft  112 , at least a portion of the length of the shaft including a cross-sectional shape in the form of a rounded polygon. This rounded polygonal cross-section may be in the form of a reuleaux polygon, such as a reuleaux triangle (“RT”). Alternately, the rounded polygonal cross-section may include any number of sides, such as from six to twelve sides. In one aspect, the shaft  112  may be threadless. It should be understood that while the majority of the embodiments disclosed herein relate to a RT shape, other rounded polygonal shapes may be substituted for the RT shape described herein. 
         [0043]    As illustrated in  FIGS. 2A-2D , a length of the shaft including a RT shape may extend along various portions of the shaft  112 . In one aspect, the entire length L of the shaft  112  may include a RT cross section, as illustrated in  FIG. 2A . As is further illustrated in  FIG. 2A , the shaft  112  may include a plurality of fletchings  116  attached to the shaft  112  near a rear end thereof. 
         [0044]    In another aspect, as shown in  FIG. 2B , a first length L 1  and a second length L 2  of the shaft  112  may include the RT cross section. The first length L 1  may be located at the front end of the shaft, such as where the head  114  may attach. The second length L 2  may be located at a rear end of the shaft, such as where a nock  118  may attach. Between the first length L 1  and the second length L 2 , the shaft may include a different cross-sectional shape, such as retaining a traditional round cross section. 
         [0045]    As shown in  FIG. 2C , the RT cross section may extend along a third length L 3 , which extends along a central portion of the shaft  112 . The front end and the rear end of the shaft  112  may include a different cross-sectional shape, such as retaining the traditional round cross section. 
         [0046]      FIG. 2D  illustrates that a single end of the shaft  112  may include the RT cross section. The remaining portion of the shaft may include a different cross-sectional shape, such as retaining the traditional round cross section. As illustrated in  FIG. 2D , it is the first length L 1  on the front end of the shaft  112  which includes the RT shape. Although not illustrated, it is also possible for only the second length L 2  of the shaft  112  to include the RT cross section. 
         [0047]    In each of  FIGS. 2B-2D , the section of the shaft  12  including the RT shape may include a different diameter than the remaining portion of the shaft. For example, the first length L 1 , the second length L 2 , and/or the third length L 3  may be larger than portion of the shaft  112  with the different cross-sectional shape. Alternately, the first length L 1 , the second length L 2 , and/or the third length L 3  may be smaller than portion of the shaft with the different cross-sectional shape. 
         [0048]    A RT cross-sectional shape  120  is illustrated in  FIG. 3A . The cross section is based on an equilateral triangle, and includes rounded sides  122  meeting at rounded corners  124 . As illustrated in  FIG. 3B , the rounded sides  122  may be more round, while  FIG. 3C  illustrates that the rounded sides  122  may be less round. 
         [0049]    The fletchings  116  may be spread around a perimeter of the cross-section of the shaft, spaced equidistantly from one another. In the case of a RT cross-section, the fletchings may be located at 120 degree intervals around the perimeter of the shaft  112 . For instance, the fletchings  116  may be attached to the shaft  112  at a midpoint between the rounded corners  124  on each of the rounded sides  122 . In another aspect, the fletchings  116  may be located on each of the rounded corners  124 . The longitudinal location of the fletchings  116  may be closer to the rear end than the front end of the shaft  112 . 
         [0050]    A shaft including the RT shape may be significantly stronger than a conventional round shaft of the same size. Specifically, a RT shaft may have a greater static and dynamic spine strength than a purely round shaft. The flexural rigidity of a RT shaft is also different due to its shape. In the case of a round shaft, the flexural rigidity is generally constant, regardless of the orientation of the arrow. In the case of a RT arrow, with a rounded corner  124  facing up, a RT shaft has a different rigidity (spine strength) with respect to a given force normal to a longitudinal axis of the arrow than with the rounded corner  124  facing down. Multiple spine strengths from one arrow may allow a manufacturer to produce fewer arrows to address the same number of spine strengths desired by a given set of consumers, than is true with arrows with round shafts. Similarly, a single arrow with different flexural rigidity depending on orientation of the arrow (such as with a RT arrow) may give multiple usage options for a given consumer with that single arrow. 
         [0051]    Because a RT shaft has a greater flexural rigidity than a round shaft, a RT arrow has less oscillation back and forth when leaving the bow, which will straighten the arrow out faster during flight. This results in a flatter trajectory and straighter arrow at close range targets for a RT arrow than a round shaft arrow. The RT shaft also has greater durability and straightness than a traditional round shaft Eliminating wobble and/or oscillation also improves accuracy. The added rigidity and strength of a RT shaft may also allow for a thinner wall thickness than a rounded shaft, which would lighten the overall weight of the arrow. 
         [0052]    The shaft  112  of the present invention may be parallel/straight, tapered, or barreled along the longitudinal axis. The shaft and arrow may be used in association with a recurve bow, a compound bow, a crossbow, or any other weapon capable of firing an arrow. The shaft may be constructed from a variety of different materials such as fiberglass, aluminum, aluminum alloys, graphite, graphite composites, boron, titanium, carbon, carbon composites and the like or combinations thereof. The various embodiments of the arrow shaft may be formed by cold working in a mandrel drawn process. An extrusion method or a pultrusion method may also be used. Another process for forming the arrow of the present invention is to use a conventional round arrow and form or attach the RT portion or portions into it. An example would be to take a round aluminum (or other suitable material) arrow and insert at least a portion of the arrow into a press or mold so that the relevant portion may be pressed or formed into the RT shape. Another process for forming the arrow of the present invention is to use a mandrel in the arrow shaft shape (including a RT portion or portions), wrap it with flexible material, and cure the material to form the shaft. 
         [0053]    With reference to  FIG. 3D , the shaft may include a wall W defined by an outer surface  125  and an inner surface  126 . The inner surface  126  may define an interior chamber or an inner bore  127  within the shaft  112 . In one aspect, the outer surface  125  and the inner surface  126  may form geometrically similar shapes in cross section. Stated another way, an outer cross section of the shaft  112 , such as may be defined by the outer surface  125 , and the inner bore  127  may be geometrically similar shapes. As illustrated in  FIG. 3D , the outer cross section of the shaft  112  and the inner bore  127  both include a RT shape. As shown in  FIG. 3E , the outer cross section of the shaft and the inner bore may take the form of a rounded pentagon. As above, these geometrically similarly shaped outer cross section and inner bores may take the form of any rounded polygon, such as a rounded polygon with an odd number of sides. 
         [0054]    As illustrated in  FIGS. 3F-3J , the outer diameter of the shaft, such as may be defined by the outer surface  125 , may be of a different shape than the bore  127 . For example, the outer diameter may be circular in cross section, while the bore  127  may take the shape of a polygon, a rounded polygon, a regular polygon, or another shape geometrically dissimilar from the outer diameter. In the illustrated embodiments, the inner bore  127  may be any of a RT ( FIG. 3F ), a triangle with rounded corners ( FIG. 3G ), a triangle, such as an equilateral triangle ( FIG. 3H ), a rounded pentagon ( FIG. 3I ), a pentagon, such as a regular pentagon ( FIG. 3H ), or any other polygon, such as a regular heptagon, with an odd number of sides. 
         [0055]    As noted above with respect to the shape of the shaft, a bore  127  with a polygonal, rounded polygonal, regular polygonal, such as is illustrated in  FIGS. 3F-3J , may result in a shaft with a variable flexural rigidity or spine strength along one radial direction than in another radial direction. In one aspect, the shaft  112  may include one or more markings, such as numbers, notches, a stamp, or the like, which may indicate a portion of the arrow with the highest flexural rigidity or spine strength. 
         [0056]    In any of the above embodiments, the bore  127  may extend either partially along the length of the shaft  112 , or along the entire length of the shaft. The bore  127  may extend along the shaft to form an aperture at one or both ends of the shaft  112 , such as apertures  130 ,  160  (see  FIGS. 4A-5B ). 
         [0057]    In a further aspect of the present invention, a self-locking and aligning knock  118  is disclosed. As shown in  FIG. 4A , the nock  118  may be inserted into the shaft  112 . In one aspect, the shaft  112  includes an aperture  130  for receiving the nock  118 . The aperture  130  may be RT shaped. The nock  118  may include a projection  132 , such as a male shank or stud for insertion into the aperture  130 . The projection  132  may include a RT cross section for mating with the RT shape of the shaft  112  and/or aperture  130 . The projection  132  and/or the aperture  130  may include one or more surface features adapted to assist engagement therebetween. For example, the projection  132  and/or the aperture  130  may include one or more of ridges, grooves, nobs, or other projections/recesses for retaining the projection  132  within the aperture  130 . The nock may be constructed out of a durable polycarbonate or the like and/or may comprise a plastic with memory capabilities. 
         [0058]    As shown in  FIG. 4B , a nock adapter  140  may be provided for attachment to the shaft  112 . The nock adapter  140  may be adapted to connect to the shaft  112  in a self-locking manner, and may do so without the use of an adhesive. In one aspect, the nock adapter  140  may be inserted into the aperture  130  of the shaft  112 . Like the nock  118 , the nock adapter  140  may include one or more surface features adapted to assist engagement between the nock adapter  140  and the aperture  130  of the shaft  112 . For example, the nock adapter  140  and/or the aperture  130  may include one or more of ridges, grooves, nobs, or other projections/recesses for retaining the nock adapter  140  within the aperture  130 . The nock adapter may be constructed out of a durable polycarbonate or the like and/or may comprise a plastic with memory capabilities, aluminum, brass, or stainless steel. 
         [0059]    The nock adapter  140  may include a collar  141  about a perimeter of an end of the nock adapter  140  that does not insert into the aperture  130 . Upon engagement with the shaft  112 , the collar  141  may be at least partially external to the aperture  130 . The collar  141  may include a taper outward toward the perimeter of the shaft  112 . This outward taper may be adapted to at least partially deflect a second arrow that may be fired at the nock end of a first arrow, such as a first arrow that has already been embedded in a target. 
         [0060]    The adapter  140  may include an aperture  142  for receiving an adapter mating nock  118 ′. The adapter mating nock  118 ′ may include a projection  132 ′ such as a male shank or stud for mating with the aperture  142 . The projection  132 ′ and the aperture  142  may both include a similar cross-sectional shape, such as a RT (or other rounded polygon). 
         [0061]    In either embodiment of  FIG. 4A or 4B , once inserted into the RT shaft  112 , the nock  118  (or adapter mating nock  118 ′) will not twist and turn like the conventional round arrow and nock, specifically because of the unique mating RT (or other rounded polygonal) shapes. Once locked into one of three rotational positions (depending on arrow rest selection), the mated nock  118  and shaft  112  will not rotate with respect to one another. Stated another way, the RT shape associated with both the nock  118  (or the adapter mating nock  118 ′) and the shaft  112  (or the adapter  140 ) provides a locking feature to prevent relative rotation. This allows for alignment of the nock in relation to the arrow shaft and/or an index vane (or odd colored fletching). For example, the RT shape of the nock  118  (or the adapter mating nock  118 ′) and the shaft  112  (or the adapter  140 ) may lock the nock  118  in a position such that the string receiver or notch may run perpendicular to the index vane. Such a configuration may assure that the bow string will run perpendicular to the index vane for proper alignment with a recurve bow. Alternately, the notch of the nock may be fixed to align with the index vane, creating a zero degree relative angular position between the notch and the index vane, such as for use with a compound bow, or a bow with a fall-away arrow rest. 
         [0062]    Proper and fixed alignment of the present invention is different from a conventional round nock (such as a press-in nock) and shaft, which is prone to twisting, turning and loosening over time, even in the presence of an adhesive. Conventional round nock and shaft configurations that are prone to misalignment may result in the arrow fletchings undesirably rubbing a portion of the bow (such as the arrow rest), and may cause an inaccurate flight path. The locked and aligned nock  118  and shaft  112  of the present invention may result in the fletchings  116  (which are fixed to the shaft  112 ) consistently being positioned in a desirable relative position with the bow string, and therefore a desirable relative position with respect to the bow. 
         [0063]    In addition, the present invention may allow for alignment of a head  114  with a shaft  112  and/or fletchings  116  of the arrow. The head  114  may take the form of a point (e.g. a target point, a bullet point, a combo point, a field point, a judo point, a blunt point, or a bludgeon point) or a broadhead. In the case of a point with a RT shape, alignment to match the three rounded sides of the shaft  112  may be problematic with a conventional threaded insert or a conventional threaded point. Similarly, alignment of the blades of a broadhead with the sides of the shaft  112  and/or the fletchings  116  may be problematic with a conventional threaded insert or conventional threaded broadhead. 
         [0064]    In one aspect of the present invention, the head  114  is configured for insertion directly into the shaft  112 . For example, a first point  114   a  may be provided comprising a single body including both a tip  150  and arrow insert  152 , as illustrated in  FIG. 5A . Similarly,  FIG. 5B  illustrates first broadhead  115   a  comprising a single body including both a tip  150 ′ and arrow insert  152 . The arrow insert  152  may be threadless. The tip  150 ′ of the first broadhead  115   a  may include one or more blades  154  and a ferrule  156 . In either embodiment of  FIG. 5A or 5B , the insert  152  may comprise a shank or stud. The insert  152  may include the RT cross-sectional shape so as to fit within an aperture  160  of the shaft  112 . In either embodiment of  FIG. 5A or 5B , at least a portion of the first point  114   a  or the first broadhead  115   a  may comprise a RT shape in cross section to match the shaft  112 . In one aspect, an adhesive may be provided for attaching the first point  114   a  or the first broadhead  115   a  to the shaft  112 . The head may be constructed of steel, stainless steel, titanium or other suitable material. 
         [0065]    In another aspect, the head  114  may be adapted to engage a receiver  170  associated with the shaft  112 . The receiver  170  may include a cross-section matching the cross-section of the shaft  112 . For example, if the shaft were round, then the receiver would be round. In the case of a RT (or other rounded polygon) shaft, the receiver  170  may also be a RT (or other similarly shaped rounded polygon). In one aspect, the receiver  170  may include a taper to account for an arrow head with a different diameter than the shaft  112 . For example, if the head were larger in cross-section than the shaft, then the receiver  170  may include an outward taper to provide a smooth transition from the smaller shaft to the larger head. 
         [0066]    As illustrated in  FIG. 6A , a second point  114   b  may be provided as a single body, including a tip  150  and an extension  172 . Similarly,  FIG. 6B  illustrates a second broadhead  115   b  comprising a single body including a tip  150 ′ and extension  172 . The tip  150 ′ may include one or more blades  174  and a ferrule  176 . The extension  172  may be configured to connect to or mate with the receiver  170 . For example, the receiver  170  may include an aperture  184  for engaging the extension  172 . The aperture  184  may lead to a channel for receiving the extension  172 . 
         [0067]    In one aspect, the extension  172  may be in the form of a shank or stud. The extension  172  may be threadless. In a further aspect, the extension  172  may have a RT cross section, another rounded polygonal cross-section, a triangular cross section, or may be round. The aperture  184  may include the same cross sectional shape as the extension  172  to ensure an accurate mated connection. The extension  172  may be adapted to frictionally engage the aperture  184  of the receiver  170 . As illustrated in  FIGS. 6A and 6B , the extension  172  may include knurling and/or grooves or ridges for engaging the aperture  184  of the receiver  170 . 
         [0068]    With further reference to  FIG. 6A , second point  114   b  may include a RT cross section to match a RT cross section of the shaft  112 . Specifically, the tip  150  may include a RT cross section. Similarly, with reference to  FIG. 6B , the second broadhead  115   b  may include a RT cross section to match a RT cross section of the shaft. Specifically, the ferrule  176  which includes a RT cross section. In one aspect, the RT cross section of either the second point  114   b  or the second broadhead  115   b  may include a RT cross section that increases in size along a longitudinal direction from tip to base. Alternately, the second point  114   b  or the second broadhead  115   b  may have a cylindrical cross section. 
         [0069]      FIG. 7  illustrates a plan view of the shaft  112  of  FIGS. 6A and 6B , with fletchings  116  equally spread around the RT cross section. A cross section of any of the second point  114   b  or the second broadhead  115   b  may be adapted to align with the RT cross section of the shaft  112 . The size of the cross section of the second point  114   b  or the second broadhead  115   b  may be the same as the size of the cross section of the receiver  170  at the point at which the receiver  170  meets the second point  114   b  or the second broadhead  115 b. 
         [0070]    As shown in  FIG. 8 , the receiver  170  may be configured for insertion into the shaft  112 . The receiver  170  may include a collar  180  and an insertion portion  182 . The collar  180  may include an outward taper, such as for engaging a head with a different cross sectional size than the shaft. The insertion portion may include a RT cross section and may be configured to be inserted into the shaft  112 . The receiver  170  may be configured to frictionally engage the shaft. For example, the insertion portion  182  may include knurling, grooves, recesses, ridges, or other surface formations for engaging an inner surface of the shaft  112 . An adhesive may be used to retain the insertion portion  182  within the shaft  112 . 
         [0071]    In one aspect, the collar  180  may include one or more fasteners  186 , such as adjustable set screws. The set screws may be configured to retain the extension  172  within the receiver  170  upon actuation thereof. For instance, the second point  114   b  or the second broadhead  115   b  may be inserted into the aperture  184 , and the set screws tightened to secure the extension  172 . In one aspect, the set screws may be allen head set screws and may be adjusted with a hex or allen key. This engagement may allow for alignment and secured fixed positioning of the head  114 , the shaft  112 , the fletchings  116 , and the nock  118 . 
         [0072]    In the case of the extension  172  and the aperture  184  being triangular, of a RT cross section, of another rounded polygonal cross section, or any other shape that prevents relative rotation between engaged elements, this configuration allows for automatic alignment between similarly shaped features. In the case of a round extension  172  and aperture  184 , the head  114  may be rotated relative to the shaft, and fasteners  186  may be used to secure the head  114  in place. 
         [0073]    In another embodiment, an insertable link  200  may be provided for connecting a head  114  to the shaft  112 , as illustrated in  FIG. 9 . The link  200  may include a cross-sectional shape that matches that of the shaft  112 . For example, the link and shaft may both be round, or may both include a RT or other polygonal cross-section. 
         [0074]    In one aspect, the link  200  may include a collar  210  and an insertion portion  212 . The collar  210  may include a taper for engaging a head  114  of a different cross sectional size than the shaft. The insertion portion  212  may include a RT cross section and may be configured to be inserted into the shaft  112 . The link  200  may be configured to frictionally engage the shaft. For example, the insertion portion  212  may include knurling, grooves, recesses, ridges, or other surface formations for engaging an inner surface of the shaft  112 . An adhesive may be used to retain the insertion portion  212  within the shaft  112 . 
         [0075]    The collar  210  of the insertable link  200  may include a protruding extension  214 , such as a stud or shaft. The extension  214  may have a RT cross section, a triangular cross section, or a round cross section. In one aspect, the extension  214  may include knurling and/or grooves. 
         [0076]    With reference to  FIG. 10A , a plan view of the collar  180  (or  210 ) is illustrated. The collar of  FIG. 10A  is illustrated as having a RT cross section, but the cross section may be round, as illustrated in  FIG. 10B . The round cross section may be used with traditionally round arrow shafts, or with a shaft that includes a round cross section at the head end of the shaft. The cross section of the collar may be the same size as the cross section of the shaft. Alternately, the cross section of the collar may be larger than the cross section of the shaft. 
         [0077]    As illustrated in  FIGS. 11A and 11B , a third point  114   c,  third broadhead  115   c,  or other head  114  may be adapted to engage the extension  214  for attachment to the shaft  112 . For example, the third point  114   c  or the third broadhead  115   c  may include an aperture for receiving the extension  214 . The aperture may include a cross-sectional shape to match that of extension  214  of the link  200 . The third point  114   c  or the third broadhead  115   c  may be aligned with the shaft  112 . The third point  114   c  or the third broadhead  115   c  may include one or more fasteners  186 , such as set screws. These fasteners may be used to secure the head on the extension  214 , once it has been attached. 
         [0078]    The receiver  170  or the link  200  may be constructed of steel, aluminum, stainless steel, brass or the like. In one aspect, the receiver  170  or the link  200  may be weighted and/or may be constructed in a variety of weights. The weight and strength of an insert such as receiver  170  or link  200  may add weight to the front of the arrow that is not present in conventional inserts. This allows for adjustment of “front of center” (FOC) balance position. 
         [0079]    The improved arrow system of the current invention allows for near perfect alignment of the arrow shaft with the nock, fletchings and points. This allows for lockable alignment of the nock with the shaft and offers tunability of the points to the arrow shaft. A conventional insert or nock insert used with a conventional round shaft is glued in place and then usually reheated so the nock or hunting point can be rotated to align with the arrow shaft and fletchings. This poses a problem with carbon arrows. Carbon arrows may not be heated because of damage to the carbon fibers. While heating the arrows enables the inserts to be rotated within the arrow shaft it also can reduce the strength of the shaft and the glue creating poor connections between the insert and arrow. The shape of the RT arrow shaft and the adjustable insert of the present invention as well as the unique shape knock solves this issue. The arrow shaft also allows for different flexural rigidity which will cut down the production of many shaft sizes. 
         [0080]    While the invention has been described with reference to specific examples, it will be understood that numerous variations, modifications and additional embodiments are possible, and all such variations, modifications, and embodiments are to be regarded as being within the spirit and scope of the invention. Also, the drawings, while illustrating the inventive concepts, are not to scale, and should not be limited to any particular sizes or dimensions. Accordingly, it is intended that the present disclosure not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.
An arrow with a non-circular central bore may allow for differential flexural rigidity in the shaft. A non-circular central bore, such as in the form of a bore with a rounded polygon, or more specifically a reuleaux triangle, may also provide self-alighting features when paired with a nock or arrowhead with similar shaped elements. This may allow a user to properly nock an arrow without resorting to manual alignment of the nock and fletchings. The central bore may extend along an entirety of the shaft, or only along a portion of the shaft. The non-circular central bore may be incorporated in an arrow shaft with a round exterior cross section, or with an arrow with a non-circular exterior cross section, such as in the form of a rounded polygon, or more specifically a reuleaux triangle.