WO2025222128A1 - One-piece bent composite shafts for sporting goods and methods of manufacture - Google Patents

Abstract

Disclosed herein arc one-piece bent composite shafts for sporting goods and methods of manufacture. The entire shaft is formed of composite materials at one time as one piece, with no connections between separate parts.

Description

ONE-PIECE BENT COMPOSITE SHAFTS FOR SPORTING GOODS

AND METHODS OF MANUFACTURE

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 63/636,501, filed April 19, 2024, which is incorporated by reference herein in its entirety.

BACKGROUND

Currently all one-piece graphite shafts for sporting goods such as putters are straight. Bent shafts (e.g., single and double bend shafts) can be advantageous for sporting goods such as putters. However, the current composite shaft manufacturing processes of sheet wrapping or filament winding only allow for a straight putter shaft to be made, not a shaft with a single or double bend tip section. Current bent putter shafts using composites are typically multi-piece with the upper portion being composite and the bent tip section being steel.

Improved composite shafts for sporting goods and methods of manufacture are needed, which can provide bent configurations without requiring multiple pieces.

SUMMARY

The present invention provides, in various embodiments, one-piece bent composite shafts and methods of manufacture that are suitable for golf clubs (including, but not limited to, putters), other sporting goods (including, but not limited to, those used in hockey, lacrosse, kayaking/stand up paddle boarding, skiing, billiards, cycling, fishing, and backpack frames), and other uses (including but not limited to, impact protection, helmets, and diving fin blades).

In some embodiments, the invention provides a one-piece bent composite shaft for a sporting good, wherein the shaft consists of a fiber composite material, is formed as one piece with no connections between separate parts, and includes at least one bend.

In some embodiments, the fiber is carbon, fiberglass, aramid, boron, basalt, ceramic, synthetic, natural, metal, or any combination thereof.

In some embodiments, the fiber is unidirectional or in fabric form.

In some embodiments, the composite material comprises a thermoset or thermoplastic matrix. In some embodiments, the shaft is 100% carbon fiber/epoxy.

In some embodiments, the shaft is tapered from a proximal end to a distal end.

In some embodiments, the shaft has a double bend at a distal end thereof.

In some embodiments, the shaft has at least one non-circular cross-section along a length thereof.

In some embodiments, the shaft has a plurality of different circular or non-circular crosssections and transitions along a length thereof.

In some embodiments, the shaft is produced by a method comprising bladder molding, trapped rubber molding, or vacuum bagging.

In some embodiments, the shaft is produced by a method comprising bladder molding, wherein ends of the shaft are joined during the molding.

In some embodiments, the invention provides an apparatus for a sporting good, comprising: a one-piece bent composite shaft, wherein the shaft consists of a fiber composite material, is formed as one piece with no connections between separate parts, and includes at least one bend; and an insert configured to connect a secondary piece to the shaft, wherein the shaft is tapered from a proximal end to a distal end, and wherein the insert is co-molded to the shaft at the distal end.

In some embodiments, the fiber is carbon, fiberglass, aramid, boron, basalt, ceramic, synthetic, natural, metal, or any combination thereof; and wherein the composite material comprises a thermoset or thermoplastic matrix.

In some embodiments, the fiber is unidirectional or in fabric form.

In some embodiments, the shaft is 100% carbon fiber/epoxy.

In some embodiments, the insert is made of metal or plastic.

In some embodiments, the invention provides a method of forming a one-piece bent composite shaft for a sporting good, wherein the shaft consists of a fiber composite material, is formed as one piece with no connections between separate parts, and includes at least one bend, wherein the method comprises bladder molding or trapped rubber molding using a mold configured to provide the at least one bend.

In some embodiments, the mold is preheated. In some embodiments, the method is bladder molding, and comprises the steps of: cutting the fiber composite material into a plurality of plies; placing an inflatable bladder over a mandrel; rolling the composite plies onto the bladder/mandrel; removing the mandrel, leaving a rolled layup comprising the plies and the bladder; inserting an inflating mandrel in an opening of the bladder; placing the layup in a mold configured to form one or more bent composite shafts; closing the mold and introducing air pressure to the bladder; curing the composite plies to form the shaft; opening the mold, removing the shaft, and removing the bladder from the shaft.

In some embodiments, the method is trapped rubber molding, and comprises the steps of: cutting the fiber composite material into a plurality of plies; attaching a flexible tip section to a metal mandrel; rolling the composite plies onto the mandrel and the flexible tip section; wrapping OPP (oriented polypropylene) tape around the composite plies on the mandrel, stopping at the flexible tip section; clamping the composite plies rolled on the flexible tip section in a mold configured to provide the one or more bends; curing the composite plies to form the shaft; opening the mold, removing the shaft, and removing the mandrel and flexible tip section from the shaft, leaving a hollow one-piece shaft with complex curved geometry at a tip section thereof.

Additional features and advantages of embodiments of the present invention are described further below. This summary section is meant merely to illustrate certain features of embodiments of the invention, and is not meant to limit the scope of the invention in any way. The failure to discuss a specific feature or embodiment of the invention, or the inclusion of one or more features in this summary section, should not be construed to limit the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of certain embodiments of the application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the systems and methods of the present application, there are shown in the drawings certain embodiments. It should be understood, however, that the application is not limited to the precise arrangements and instrumentalities shown. In the drawings: FIG. 1 is a flowchart of a bladder molding process according to various embodiments of the present invention;

FIG. 2 is a schematic showing a mandrel, bladder, and composite (prepreg) plies for a golf shaft according to various embodiments of the present invention;

FIG. 3 is a schematic showing a cross-sectional view of a lay-up with the mandrel in place during rolling of the plies (left), and with the mandrel removed, prepared for pressure molding (right), according to various embodiments of the present invention;

FIG. 4 is a schematic showing one half of a mold before the lay-up is placed in the cavity (top) and the mold in a closed position (bottom);

FIG. 5-7 show, respectively, a top view, an isometric view, and an isometric rendering of a bottom half of a mold for a three right hand shafts and one left hand shaft, according to various embodiments of the present invention;

FIG. 8 shows a top view of the mold of FIG. 5 with a lay-up before installation;

FIG. 9 shows an isometric view of a closed mold, according to various embodiments of the present invention;

FIGS. 10-12 show, respectively, a top view, an isometric view, and an isometric rendering of an inflating mandrel (plug), according to various embodiments of the present invention;

FIG. 13 shows an isometric view of an inflating mandrel positioned in one half of a mold, according to various embodiments of the present invention;

FIG. 14 shows a top detail view of FIG. 13;

FIG. 15 shows a top view of the inflating mandrel of FIG. 10, a bladder, and a lay-up, according to various embodiments of the present invention;

FIG. 16 shows a rendering of FIG. 15;

FIG. 17 shows a top detail view of shafts produced using the mold of FIG. 5, with bend angles indicated;

FIG. 18 shows an isometric rendering of a bottom half of a trapped rubber mold, according to various embodiments of the present invention (left) and an isometric view of the trapped rubber mold in a closed position (right); FIG. 19 shows a side view of an exemplary shaft according to various embodiments of the present invention, with cross-sectional shapes of the shaft indicated adjacent to the respective sections; and

FIG. 20 shows (A) top, side, and perspective views, clockwise respectively, of another exemplary shaft according to various embodiments of the present invention, and (B) cross- sectional views A-A and B-B.

DETAILED DESCRIPTION

As described above, currently all one-piece graphite shafts for sporting goods such as golf clubs are straight. Bent putter shafts using composites are typically multi-piece with the upper portion being composite and the bent tip section being steel.

Specifically, current bent putter shafts that use composites are multi-piece shafts with a connection between the tip section and the upper part of the shaft; the connection between the two creates a region that is stiffer than the locations immediately below and above the connection, resulting in poor feel and feedback. Since current shafts use different materials for the tip and upper sections, the torque and stiffness of the sections are not matched and continuous throughout the shaft.

In various embodiments, the present invention provides one-piece bent composite shafts suitable for golf clubs (including, but not limited to, putters) and other sporting goods (including, but not limited to, hockey sticks), which can avoid the above-described limitations of current commercially-available products.

In some embodiments, the invention provides a one-piece 100% composite putter shaft with a single or double bend at the tip like that of a steel putter shaft. The entire full-length shaft of the putter is formed at one time as one piece. There are no connections between separate parts. The fiber can be all graphite/carbon fiber, a combination of graphite and fiberglass, or other fibers such as polyphenylene oxide (PPO), basalt, ceramic, tungsten, aramid, boron, synthetic, natural, metal, or any combination thereof.

Using graphite allows for most characteristics of the shaft to be adjusted and/or optimized, for example, for specific performance, feedback, player type, or club requirements. In addition, graphite shafts can be lighter than current steel shafts. For example, a graphite shaft can be lighter, lower torque, and stiffer than steel individually or in any combination. In some embodiments, the shaft can vary in weight, for example, from about 50g to about 150g. Torque can range, for example, from about 0.5° to about 4.0°. Stiffness can range, for example, from about 200cpm to about 450cpm. Tip outside diameter can range, for example, from about 0.320in to about 0.450in.

In general, shafts according to embodiments of the present invention are differentiated from the existing steel bent putter shaft in one or more of the following features:

• Weight: embodiments of the present invention can be >40g lighter while maintaining similar torque and stiffness (CPM; cycles per minute) values, allowing weight adjustments to the putter head and backweighting to the grip, enhancing performance and feel, without an increasing overall weight.

• Torque: embodiments of the present invention can achieve a wide range of torque resistance (e.g., 0.9°-2.0°), even below that of the current steel shaft.

• Stiffness: Again, a wide range of stiffness can be achieved, much more flexible and much stiffer than steel, at weights significantly less than the current steel shaft.

Furthermore, by using a composite material, each of these parameters can be modified independently, which is not possible with steel.

Table 1 shows values of these parameters for bent shafts according to various embodiments of the present invention (Examples 1-5), and compares them to those of existing commercially-available shafts (current steel, BGT Stability, UST All-In, and Accra Sync). The BGT and UST shafts allow the clubmaker to install the lower tip section of a steel shaft into the composite upper section of the shaft. There is a joint connection between the upper and lower sections, which creates a very stiff area around the joint, stiffer than the adjoining areas. The torque resistance of the two sections is also different, and this is also transitioned through the joint. Both of these issues are detrimental to the feel and feedback of the shaft to the player.

Table 1

In some embodiments, the invention provides methods of manufacturing shafts according to embodiments of the present invention, such as one-piece bent composite putter shafts, by bladder molding or trapped rubber molding. Putters are referenced below, but the one-piece bent composite shafts and methods of manufacturing described herein can be used for other types of golf clubs, other types of sporting goods (such as those used in hockey, lacrosse, kayaking/stand up paddle boarding, skiing, billiards, cycling, fishing, and backpack frames), and other uses (including but not limited to, impact protection, helmets, and diving fin blades).

The current composite shaft manufacturing processes of sheet wrapping or filament winding only allow for a straight putter shaft to be made, not a shaft with a single or double bend tip section. Embodiments of the present invention allow for the composite material to be rolled on a mandrel straight and then formed with the desired bent geometry during the curing process.

Methods of manufacture according to embodiments of the present invention allow for a complete, full-length composite bent putter shaft to be made in one piece, not several and not a combination of different materials that need a joint connection between pieces that disrupt the continuous stiffness and torque profiles resulting in poor feel and inconsistent head presentation. When made in one continuous shaft control, feel and consistency are all improved.

In some embodiments, a method of manufacture for a one piece bent composite putter shaft by a bladder molding process includes the following steps:

• Cut prepreg material

• Flexible/inflatable bladder placed over an undersized mandrel

• Prepeg plies rolled on bladder/mandrel

• Mandrel is removed and a short inflating mandrel with air ports is placed in the open end of the bladder • The assembly (lay-up) is placed in a heated metal mold configured to form one or more bent composite shafts

• When the mold is closed, air pressure is introduced to the bladder, which expands and the composite plies form to the shape of the mold geometry and are cured

• Once cured the mold is opened and the shaft removed, then the bladder is removed

• Finishing then occurs similar to current processes

FIG. 1 is a flowchart of the bladder molding process according to some embodiments. The air fitting (short inflating mandrel) may be attached to the bladder before the lay-up is placed in the mold (as described above) or after (as in FIG. 1). FIG. 2 is a schematic showing the mandrel, bladder, and composite (prepreg) plies according to some embodiments. FIG. 3 is a schematic showing a cross-sectional view of the lay-up with the mandrel in place during rolling of the plies (left), and with the mandrel removed, prepared for pressure molding (right). FIG. 4 is a schematic showing one half of the mold before the lay-up is placed in the cavity (top) and the mold in a closed position (bottom).

FIG. 5-7 show, respectively, a top view, an isometric view, and an isometric rendering of a bottom half of a mold for a three right hand shafts and one left hand shaft, according to various embodiments of the present invention. FIG. 8 shows a top view of the mold of FIG. 5 with a layup before installation in the mold. FIG. 9 shows an isometric view of a closed mold, according to various embodiments of the present invention.

FIGS. 10-12 show, respectively, a top view, an isometric view, and an isometric rendering of an inflating mandrel (plug), according to various embodiments of the present invention. FIG. 13 shows an isometric view of the inflating mandrel of FIG. 10 positioned in one half of the mold of FIG. 5, according to various embodiments of the present invention. FIG. 14 shows a top detail view of FIG. 13. FIG. 15 shows a top view of the inflating mandrel of FIG. 10 (top), a bladder (center), and a lay-up (bottom), according to various embodiments of the present invention. FIG. 16 shows a rendering of FIG. 15. FIG. 17 shows top and side detail views of a shaft produced using the mold of FIG. 5, with bend angles indicated. The views shown are for a right hand shaft; for a left hand shaft the top view would have the angles mirrored, but the side view would be the same. The mandrel and mold are generally formed from a metal or alloy. In some embodiments, steel may be used for durability in production. Aluminum may be used for low volumes and prototyping, as it is easier and faster to machine; however, it does not hold a polish as well as steel. In some embodiments, a material that is stable over 300 °F with a hardness and strength similar to aluminum or steel could be used, such as a 3D printed metal or plastic.

The bladder is generally formed from a flexible, elastomeric material. In some embodiments, the bladder is natural latex rubber. The bladder may be formed from any material that can withstand >300°F and is airtight, such as, but not limited to, silicone, butyl rubber, EPDM (ethylene propylene diene terpolymer), polyurethane, nylon, TPU (thermoplastic polyurethane).

In some embodiments, the latex bladder is a separate piece made by a dipping process whereby a bladder mandrel is dipped in a latex bath and allowed to cool and form a solid skin which is removed and becomes the individual bladder. This bladder is then pulled over or rolled onto a different mandrel (the shaft mandrel) before the plies are rolled on. The thickness of the bladder (regardless of material: latex, silicone, TPU, etc.) is preferably only as thick as necessary to withstand the internal pressure (<250psi) and temperature (<310°F) of the molding process.

The plies generally comprise all composite material. In some embodiments, the plies are 100% carbon fiber/epoxy. These materials could be uni-directional (UD) with all fibers in one direction or fabric form with fibers in two or more directions. The epoxy matrix may comprise, for example, one of the quick-cure resins that cure in less than 20 minutes, such as Mitsubishi 301-5 Epoxy that cures in 3 minutes at 300°F.

Fibers that could be used for the plies include, but are not limited to:

• Carbon (also referred to as graphite) is available in many grades that vary by modulus (stiffness) and strength. The fibers used are dependent on the desired properties of the final shaft (stiffness, torque, etc.)

• Fiberglass

• Aramid (Kevlar/Twaron)

• Boron

• Basalt

• Ceramic

• Synthetic: PBO (Zylon), LCP (Vectran), Polyethylene (Dyneema/Spectra) • Natural: Flax, hemp, jute, sisal, bamboo

• Metal: Stainless steel, titanium, aluminum, Ni-Ti, copper

Matrix systems that could be used for the plies include, but are not limited to:

• Thermoset: Epoxy (preferred), ideally a “snap” or quick-cure epoxy that cures in less than 20 minutes below 310°F, or a standard 60 minute 250°F system

• Thermoplastic: Polyamide, Polycarbonate, PEEK (poly ether ether ketone)

After rolling and before curing, the full-length mandrel may be easily removed as the as the plies have not yet been compacted and cured. No release agent is needed.

The inflating port/mandrel can be as simple as a round rubber plug with an air fitting attached to it. The fitting is attached to air pressure which exits through ports and inflates the bladder, the plug fits into the bladder and when the two-sided mold is closed the plug (in the open end of the bladder) is compressed and forms an airtight seal to hold the pressure when the bladder inflates. The rubber plug and air fitting can be stock items or custom-made parts. The plug is preferably slightly larger than the mandrel to ensure a firm fit inside the bladder. In some embodiments, a metal plug may be used in production for durability.

In some embodiments, the lay-up may be placed in a heated mold. The mold may be heated, for example, to a temperature between 250°F and 310°F depending on the resin system used. Using a pre-heated mold can eliminate the time to heat up the mold and can drastically reduce the cycle time to produce parts.

Curing time and temperature may be varied, for example, depending on the resin system used. Typical ranges may be, for example, 3-12 minutes at 265-310°F. In some embodiments, curing is performed with a cycle time of about 5 minutes at 295°F.

After curing, the short plug is easy to remove as it was only compressed against the bladder and mold. Any length of the plug inside the cured shaft is much smaller than the ID (inner diameter) of the shaft and not in contact with the shaft.

In some embodiments, a method of manufacture for a one piece bent composite putter shaft by a trapped rubber molding process includes the following steps:

• Cut prepreg material

• A flexible tip section is attached to metal mandrel

• Prepreg plies are rolled on the mandrel in a standard sheet wrapping process • OPP (oriented polypropylene) tape is wrapped to apply pressure to the laminate; this stops where the flexible tip section starts

• The laminate rolled on the flexible tip section is then clamped in a mold with the desired geometry (e.g., one or more bends)

• The entire assembly is cured

• The mandrel and flexible tip section is removed, leaving a hollow one-piece shaft with complex curved geometry in the tip section

• Shaft is finished using the current paint/graphics processes

In some embodiments, the length of the flexible tip section may be about 125mm and the material may be a silicone rubber of hardness Shore 60A. Length of the flexible tip section preferably ranges from about 100mm to about 180mm. In addition to silicone, other flexible, elastomeric materials could be used, such as, but not limited to, TPU, TPE (thermoplastic elastomer), and EPDM.

In some embodiments, for attaching the flexible tip section to the mandrel, there is a recess in the mandrel that the flexible tip fits into, then a cross pin is inserted to keep it in place. Any common attachment method could be used (threads, pin and slot, etc.). Conversely, the end of the mandrel could be undersized and then the end of the flexible tip pulled over it like a sock.

The upper/rigid part of the mandrel is wrapped in OPP tape as normal and then fits into a larger diameter section (e.g., about 25mm long) at the top of the form tool (the mold with desired geometry). The tool is firmly clamped to ensure alignment. FIG. 18 shows an isometric rendering of an example of a bottom half of a trapped rubber mold (left) and an isometric view of the trapped rubber mold in a closed position (right). The trapped rubber piece is slightly oversized, therefore pressure is applied to the laminate when the tool is clamped.

As for bladder molding, the mandrel and mold used for trapped rubber molding are generally formed from a metal or alloy. In some embodiments, the mandrel is steel and the mold is aluminum (for rapid heating), though steel may also be used for the trapped rubber mold. The plies may be the same as described above for bladder molding. Cure time may be extended for trapped rubber molding as compared to bladder molding, because the tool (mold) is not preheated to the curing temperature.

Normally braided carbon is supplied as dry cloth without the resin. In some embodiments, prepreg braid is wound using “tow-preg” which is a bundle of fibers precoated with resin so it is used the same as the flat prepreg sheets that are normally used. Tn other embodiments, as the layers of braided tube arc pulled over the flexible tip a liquid resin is brushed on; this is referred to as wet lay-up braid.

In further embodiments, vacuum bagging with prepreg braid may be used to make the tip section. In this method, a nylon tube is used in place of the trapped rubber piece and then the entire mold is encased in a vacuum bag which is attached to the exterior of the nylon tube. When all the air is removed from the bag the pressure differential applies pressure to the interior of the laminate in the mold.

In sporting goods, varying the cross-sectional shape depending on location and use can be beneficial. For example, a flatter or oval kayak paddle shaft is easier to grip and reduces hand fatigue. Similarly, altering the shape and cross-section of a backpack frame enhances rigidity, minimizes weight, and decreases fatigue compared to a purely circular frame. In some embodiments, cross-sectional changes may involve transitioning between a round and oval shape for reasons of ergonomics, but various embodiments may also include a transition from a round to a square or hexagonal shape.

FIG. 19 shows a side view of an exemplary shaft according to various embodiments of the present invention, with cross-sectional shapes of the shaft indicated adjacent to the respective sections. This type of shaft may be used, for example, for a kayak paddle. As shown in FIG. 19, the paddle may have ergonomic oval sections where hands are placed.

FIG. 20 shows (A) top, side, and perspective views, clockwise respectively, of another exemplary shaft according to various embodiments of the present invention, and (B) cross- sectional views A-A and B-B. This type of shaft may be used, for example, for a backpack frame. The shaft forming the frame may have a circular cross-sectional shape on vertical segments, and an oval cross-sectional shape on cross elements to conform to the body of a hiker. The backpack frame can be molded as a single piece using bladder molding with a single mold and one layup, which makes the entire frame hollow to reduce weight. In this embodiment, a small hole is used for inflating and removing the bladder. The frame is continuous, eliminating the need for connecting two ends post-molding. Alternatively, in other embodiments, a nylon bladder may be used. In these embodiments, the nylon bladder can remain inside the hollow frame after molding with minimal weight increase. While there have been shown and described fundamental novel features of the invention as applied to the preferred and illustrative embodiments thereof, it will be understood that omissions and substitutions and changes in the form and details of the disclosed invention may be made by those skilled in the art without departing from the spirit of the invention. Moreover, as is readily apparent, numerous modifications and changes may readily occur to those skilled in the art. For example, various features and structures of the different embodiments discussed herein may be combined and interchanged. Hence, it is not desired to limit the invention to the exact construction and operation shown and described and, accordingly, all suitable modification equivalents may be resorted to falling within the scope of the invention as claimed. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

1. A one-piece bent composite shaft for a sporting good, wherein the shaft consists of a fiber composite material, is formed as one piece with no connections between separate parts, and includes at least one bend.

2. The shaft of claim 1, wherein the fiber is carbon, fiberglass, aramid, boron, basalt, ceramic, synthetic, natural, metal, or any combination thereof.

3. The shaft of claim 1, wherein the fiber is unidirectional or in fabric form.

4. The shaft of claim 1, wherein the composite material comprises a thermoset or thermoplastic matrix.

5. The shaft of claim 1, wherein the shaft is 100% carbon fiber/epoxy.

6. The shaft of claim 1, wherein the shaft is tapered from a proximal end to a distal end.

7. The shaft of claim 1, wherein the shaft has a double bend at a distal end thereof.

8. The shaft of claim 1, wherein the shaft has at least one non-circular cross-section along a length thereof.

9. The shaft of claim 1, wherein the shaft has a plurality of different circular or non-circular cross-sections and transitions along a length thereof.

10. The shaft of claim 1, produced by a method comprising bladder molding, trapped rubber molding, or vacuum bagging.

11. The shaft of claim 1, produced by a method comprising bladder molding, wherein two ends of the shaft are joined during the molding.

12. An apparatus for a sporting good, comprising: a one-piece bent composite shaft, wherein the shaft consists of a fiber composite material, is formed as one piece with no connections between separate parts, and includes at least one bend; and an insert configured to connect a secondary piece to the shaft, wherein the shaft is tapered from a proximal end to a distal end, and wherein the insert is co-molded to the shaft at the distal end.

13. The apparatus of claim 12, wherein the fiber is carbon, fiberglass, aramid, boron, basalt, ceramic, synthetic, natural, metal, or any combination thereof; and wherein the composite material comprises a thermoset or thermoplastic matrix.

14. The apparatus of claim 12, wherein the fiber is unidirectional or in fabric form.

15. The apparatus of claim 12, wherein the shaft is 100% carbon fiber/epoxy.

16. The apparatus of claim 12, wherein the insert is made of metal or plastic.

17. A method of forming a shaft according to claim 1, wherein the method comprises bladder molding or trapped rubber molding using a mold configured to provide the at least one bend.

18. The method of claim 17, wherein the mold is preheated.

19. The method of claim 17, wherein the method is bladder molding, and comprises the steps of: cutting the fiber composite material into a plurality of plies; placing an inflatable bladder over a mandrel; rolling the composite plies onto the bladder/mandrel; removing the mandrel, leaving a rolled layup comprising the plies and the bladder; inserting an inflating mandrel in an opening of the bladder; placing the layup in a mold configured to form one or more bent composite shafts; closing the mold and introducing air pressure to the bladder; curing the composite plies to form the shaft; opening the mold, removing the shaft, and removing the bladder from the shaft.

20. The method of claim 17, wherein the method is trapped rubber molding, and comprises the steps of: cutting the fiber composite material into a plurality of plies; attaching a flexible tip section to a metal mandrel rolling the composite plies onto the mandrel and the flexible tip section; wrapping OPP (oriented polypropylene) tape around the composite plies on the mandrel, stopping at the flexible tip section; clamping the composite plies rolled on the flexible tip section in a mold configured to provide the one or more bends; curing the composite plies to form the shaft; opening the mold, removing the shaft, and removing the mandrel and flexible tip section from the shaft, leaving a hollow one-piece shaft with complex curved geometry at a tip section thereof.