Matrix composite golf club shaft and madrel
A golf club shaft is provided that has a grip end opposite a head end and defining a length of the shaft extending between those two ends. The shaft has a tubular cross-section over at least one portion of the shaft length which cross-section has a substantially circular outer periphery and a polygon inner periphery formed of a plurality of between 4 and 24 flats, and preferably formed of 8-16 flats. A mandrel having the shape of the inner periphery of the shaft is also provided, as is a method of forming the shaft that uses the mandrel and composite matrix materials.
1. A method of making a golf club shaft having a grip end opposite a head end defining a length of the shaft extending between those two ends, comprising:
wrapping a composite matrix completely around a mandrel tapering from the larger grip end of the mandrel toward a smaller head end of the mandrel, the mandrel having a first portion with a polygon outer periphery formed of a plurality of between 16-24 flats joined at rounded corners, the mandrel having a second portion extending over the head end of the mandrel in which the mandrel has a generally circular outer periphery;
subjecting the mandrel and wrapped composite matrix to pressure and increased temperature sufficient to cause the matrix to bind strands in the matrix to form a unitary composite structure in the shape of a tubular shaft, the corners of the mandrel being sufficiently round and the matrix being sufficiently thick to form the tubular shaft with a cross-sectional shape that is generally circular along the length of the shaft while having a plurality of flats on a first portion of the inside of the tubular shaft and having a generally circular cross-sectional shape on a second of the shaft at the head end of the shaft; and
separating the shaft from the mandrel.
2. The method of claim 1 , wherein the polygon has an even number of sides.
3. The method of claim 1 , wherein the first portion of the length extends for a at least half the length of the mandrel.
4. The method of claim 1 , wherein the mandrel further comprises a third portion spaced apart from the first portion, the third portion of the mandrel having a cross-section which has a polygon inner periphery formed of a plurality of flats, the first and second portions being separated by a portion of the mandrel having a generally circular outer periphery.
5. The method of claim 1 , wherein the mandrel has an outer periphery at the head end of the mandrel shaped to form an inside of the shaft to receive a post on a golf club head.
6. The method of claim 1 , wherein there are 16 flats of substantially equal length when measured along a longitudinal axis of the mandrel.
7. The method of claim 1 , wherein there are 16 flats.
8. The method of claim 1 , wherein said composite matrix is a graphite composite.
9. The method of claim 1 , wherein said composite matrix includes a metal composite.