Ball bat with one-piece multi-wall barrel portion

1. A method of forming a ball bat extending along a longitudinal axis and configured for impacting a ball,

obtaining a mandrel shaped to define at least an inner surface of a barrel portion of the bat, the mandrel extending along the longitudinal axis;

wrapping a first plurality of layers of fiber composite material about the mandrel, the first plurality of layers of fiber composite material being initially uncured, the first plurality of layers wrapped about the mandrel having a first longitudinal dimension;

placing a removable material over a first portion of the first plurality of layers, the first portion of the first plurality of layers covered by the removable material having a second longitudinal dimension that is less than the first longitudinal dimension;

wrapping a second plurality of layers of fiber composite material over the removable material covering the first portion of the first plurality of layers and over at least a second portion of the first plurality of fibers, the second portion of the first plurality of fibers being uncovered by the removable material, the second plurality of layers of fiber composite material being initially uncured, the first and second plurality of layers and the removable material forming a pre-molded barrel portion lay-up;

separating the mandrel from the pre-molded barrel portion lay-up;

inserting an expandable member within the pre-molded barrel portion lay-up;

inserting the pre-molded barrel portion lay-up into a barrel-forming mold, and molding the first and second pluralities of layers together with the removable material in a single molding cycle;

curing the first and second pluralities of layers with the removable material to form at least the barrel portion of the bat; and

removing the removable material and the expandable member from the barrel portion, wherein once molded and cured, the first and second pluralities of layers form a proximal region of the barrel portion, wherein the first plurality of layers forms a first inner barrel wall of the barrel portion longitudinally extending from the proximal region, and wherein, once molded and cured, the second plurality of layers forms an outer barrel wall of the barrel portion longitudinally extending from the proximal region, and wherein the length of the first inner barrel wall is shorter than the length of the outer barrel wall.

2. The method of claim 1 , wherein the expandable member is an inflatable bladder that is pressurized during the molding of the first and second pluralities of layers together with the removable material.

3. The method of claim 1 , wherein the expandable member comprises a material that expands under heat.

4. The method of claim 3 , wherein the expandable member is selected from the group consisting of a silicone, a polymeric foam, an elastomer, other high coefficient of thermoexpansion materials, and combinations thereof.

5. The method of claim 1 , wherein the removable material is a tube formed of a polymeric material.

6. The method of claim 5 , wherein the polymeric material is a latex.

7. The method of claim 1 , wherein the removable material is selected from the group consisting of wax, sand, and a silicon with release layers.

8. The method of claim 1 , wherein the first inner barrel wall and the outer barrel wall are spaced apart by a first separation.

9. The method of claim 8 , wherein the first separation is substantially uniform along the length of the first separation.

10. The method of claim 8 , wherein the first separation has a radial dimension between the first inner barrel wall and the outer barrel wall within the range of 0.010 to 0.200 inch.

11. The method of claim 8 , wherein the first separation has a radial dimension between the first inner barrel wall and the outer barrel wall within the range of 0.030 to 0.110 inch.

12. The method of claim 1 , wherein the first inner barrel wall and the outer barrel wall each have a wall thickness measured radially from the longitudinal axis within the range of 0.030 to 0.200 inch.

13. The method of claim 1 , wherein the proximal region, the first inner barrel wall and the outer barrel wall are a single unitary body.

14. The method of claim 1 , wherein the length of the first inner barrel wall is 0.2 inch to 4 inches less than the length of the outer barrel wall.

15. The method of claim 1 , further comprising the step of coupling an end cap to a distal end of the barrel portion, and wherein the first inner barrel wall is longitudinally spaced apart from the end cap.

16. The method of claim 1 , further comprising the step of coupling a handle portion to the proximal end of the barrel portion.

17. The method of claim 1 , wherein the proximal region of the barrel portion has a length within the range of 1 inch to 7 inches.

18. The method of claim 8 , wherein the first separation is configured to allow for independent movement between the inner barrel wall and the outer barrel wall upon impact with the ball.

19. A method of forming a ball bat extending along a longitudinal axis and configured for impacting a ball,

obtaining a mandrel shaped to define at least an inner surface of a barrel portion of the bat, the mandrel extending along the longitudinal axis;

placing an inflatable bladder over the mandrel;

wrapping a first plurality of layers of fiber composite material about the inflatable bladder and the mandrel, the first plurality of layers of fiber composite material being initially uncured, the first plurality of layers wrapped about the mandrel having a first longitudinal dimension;

placing a removable material over a first portion of the first plurality of layers, the portion of the first plurality of layers covered by the removable material having a second longitudinal dimension that is less than the first longitudinal dimension;

wrapping a second plurality of layers of fiber composite material over the removable material covering the first portion of the first plurality of layers and over at least a second portion of the first plurality of fibers, the second portion of the first plurality of fibers being uncovered by the removable material, the second plurality of layers of fiber composite material being initially uncured;

inserting the first and second pluralities of layers together with the removable material, the mandrel and the inflatable bladder within a barrel portion-forming mold;

pressurizing the inflatable bladder and molding the first and second pluralities of layers together with the removable material in a single molding cycle;

curing the first and second pluralities of layers with the removable material to form at least the barrel portion of the bat;

separating the mandrel and the inflatable bladder from the barrel portion; and

removing the removable material from the barrel portion, wherein once molded and cured, the first and second pluralities of layers form a proximal region of the barrel portion, wherein the first plurality of layers forms a first inner barrel wall of the barrel portion longitudinally extending from the proximal region, and wherein, once molded and cured, the second plurality of layers forms an outer barrel wall of the barrel portion longitudinally extending from the proximal region, and wherein the proximal region is the only point of contact between the first inner barrel wall and the outer barrel wall.

20. A method of forming a ball bat extending along a longitudinal axis and configured for impacting a ball,

obtaining a mandrel shaped to define at least an inner surface of a barrel portion of the bat, the mandrel extending along the longitudinal axis;

wrapping a first plurality of layers of fiber composite material about the mandrel, the first plurality of layers of fiber composite material being initially uncured, the first plurality of layers wrapped about the mandrel having a first longitudinal dimension;

placing a removable material over a first portion of the first plurality of layers, the first portion of the first plurality of layers covered by the removable material having a second longitudinal dimension that is less than the first longitudinal dimension;

wrapping a second plurality of layers of fiber composite material over the removable material covering the first portion of the first plurality of layers and over at least a second portion of the first plurality of fibers, the second portion of the first plurality of fibers being uncovered by the removable material, the second plurality of layers of fiber composite material being initially uncured, the first and second plurality of layers and the removable material forming a pre-molded barrel portion lay-up;

separating the mandrel from the pre-molded barrel portion lay-up;

inserting an expandable member within the pre-molded barrel portion lay-up;

inserting the pre-molded barrel portion lay-up into a barrel-forming mold, and molding the first and second pluralities of layers together with the removable material in a single molding cycle;

curing the first and second pluralities of layers with the removable material to form at least the barrel portion of the bat; and

removing the removable material and the expandable member from the barrel portion, wherein the barrel portion of the bat has a distal end, and wherein, prior to removing the removable material from the barrel portion, the removable material longitudinally extends beyond the distal end of the barrel portion by at least one inch.

21. The method claim 20 , wherein the expandable member is an inflatable bladder that is pressurized during the molding of the first and second pluralities of layers together with the removable material.

22. The method of claim 20 , wherein the first inner barrel wall and the outer barrel wall are spaced apart by a first separation, wherein the first separation is substantially uniform along the length of the first separation, and wherein the first separation has a radial dimension between the first inner barrel wall and the outer barrel wall within the range of 0.030 to 0.110 inch.

23. A method of forming a ball bat extending along a longitudinal axis and configured for impacting a ball,

obtaining a mandrel shaped to define at least an inner surface of a barrel portion of the bat, the mandrel extending along the longitudinal axis;

placing an inflatable bladder over the mandrel;

wrapping a first plurality of layers of fiber composite material about the inflatable bladder and the mandrel, the first plurality of layers of fiber composite material being initially uncured, the first plurality of layers wrapped about the mandrel having a first longitudinal dimension;

placing a removable material over a first portion of the first plurality of layers, the portion of the first plurality of layers covered by the removable material having a second longitudinal dimension that is less than the first longitudinal dimension;

wrapping a second plurality of layers of fiber composite material over the removable material covering the first portion of the first plurality of layers and over at least a second portion of the first plurality of fibers, the second portion of the first plurality of fibers being uncovered by the removable material, the second plurality of layers of fiber composite material being initially uncured;

inserting the first and second pluralities of layers together with the removable material, the mandrel and the inflatable bladder within a barrel portion-forming mold;

pressurizing the inflatable bladder and molding the first and second pluralities of layers together with the removable material in a single molding cycle;

curing the first and second pluralities of layers with the removable material to form at least the barrel portion of the bat;

separating the mandrel and the inflatable bladder from the barrel portion; and

removing the removable material from the barrel portion, wherein the removable material is a tube formed of a polymeric material, wherein the barrel portion of the bat has a distal end, and wherein, prior to removing the removable material from the barrel portion, the removable material longitudinally extends beyond the distal end of the barrel portion by at least one inch.

24. The method claim 23 , wherein the expandable member is an inflatable bladder that is pressurized during the molding of the first and second pluralities of layers together with the removable material.

25. The method of claim 23 , wherein the first inner barrel wall and the outer barrel wall are spaced apart by a first separation, wherein the first separation is substantially uniform along the length of the first separation, and wherein the first separation has a radial dimension between the first inner barrel wall and the outer barrel wall within the range of 0.030 to 0.110 inch.