US20080318705A1

US20080318705A1 - Golf club set

Info

Publication number: US20080318705A1
Application number: US12/137,721
Authority: US
Inventors: Karl A. Clausen; Scott A. Rice
Original assignee: Acushnet Co
Current assignee: Cobra Golf Inc
Priority date: 2007-06-22
Filing date: 2008-06-12
Publication date: 2008-12-25

Abstract

A set of golf clubs having a plurality of construction types. The clubs of each construction type are constructed to have a volumetric bias in a pre-selected range.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. patent application Ser. No. 11/766,824, filed on Jun. 22, 2007, now pending, the disclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to a set of golf clubs and, more particularly to a set of golf clubs including club heads having volumetric bias in pre-selected ranges.

BACKGROUND OF THE INVENTION

The individual golf club heads in a set typically increase progressively in strike face surface area and weight as the clubs progress from the long irons to the short irons. Therefore, the club heads of the long irons have a smaller strike face surface area than the short irons and are typically more difficult for the average golfer to hit consistently well. For conventional club heads, this arises at least in part due to the smaller sweet spot of the corresponding smaller strike face.
To help the average golfer consistently hit the sweet spot of a club head, many golf clubs are available having heads with so-called cavity back designs with increased perimeter weighting. Another more recent trend has been to simply increase the overall size of the club heads, especially in the long irons. Each of these features will increase the size of the sweet spot and therefore make it more likely that a shot hit slightly off the center of gravity of the club head still makes contact with the sweet spot and flies farther and straighter as a result. One challenge the golf club designer faces is maintaining a desirable and effective overall weight of the golf club when maximizing the size of the club head. For example, if the club head of a three iron is increased in size and weight, the club may become difficult for the average golfer to properly swing.
Another problem area for the average golfer is that of excess vibration resulting from an off center impact with the golf ball. Various types of vibration dampening have been incorporated into club heads to absorb these impact vibrations. However, there is still a need for improvement in the areas of weight redistribution, vibration dampening in golf club heads, and especially improving the sound and feel upon striking the golf ball. A significant need is to provide a golf club head that is more tolerant to a golfer's inadvertent misplacement of the front hitting surface upon contact with the ball. In addition to inaccuracy of the shot, vibrations are indicative of a less than ideal transfer of energy from the club to the ball, and consequently represent inefficiency in the club head.
There remains a significant need, therefore, for a golf club head that is more accurate and more forgiving and which more efficiently dampens the transmission of shock vibrations from the golf club head to the shaft.

SUMMARY OF THE INVENTION

The invention includes a set of golf clubs having club heads having a plurality of constructions that are constructed with volumetric bias in pre-selected ranges. An advantage of constructing the club heads to have volumetric bias in pre-selected ranges is to selectively build in fade and/or draw bias into the set of golf clubs.
An embodiment of a set of golf clubs of the present embodiment includes a plurality of golf clubs with golf club heads having different constructions. A first golf club includes a first club head having a first striking face, a first construction type, a first volume and a first volumetric bias relative to a face center of the first striking face. A second golf club includes a second club head having a second striking face, a second construction type, a second volume and a second volumetric bias relative to a face center of the second striking face. A third golf club includes a third club head having a third striking face, a third construction type, a third volume and a third volumetric bias relative to a face center of the third striking face. The first volume is greater than the second volume and the first volumetric bias is less than the second volumetric bias. Additionally, a center of gravity of each club head is spaced rearward from the striking face of the club head.
In another embodiment of a set of golf clubs of the present invention, the set includes a first plurality of golf clubs including club heads having volumetric bias relative to face center between 1.25 and 1.70 and a second plurality of golf clubs including club heads having volumetric bias relative to face center between 1.95 and 2.90. The first plurality of golf clubs comprises generally hollow club heads. Additionally, a center of gravity of each club head is spaced rearward from the striking face of the club head.
In another embodiment, a golf club head of the present invention comprises a body portion that is preferably made of stainless steel and which has a cavity defined therein, wherein a first silicone having a high durometer hardness and a second silicone comprising of a lower hardness durometer substantially fills the cavity. The first silicone is disposed into the cavity as a hot molded cured silicone material having Shore A hardness of about 70 to 80, and the material is placed into the cavity so as to be contiguous against the interior surface of the body. The second silicone, having a hardness of about 40-50, is then disposed into the cavity so as to be juxtaposed against the outer boundary of the first material. A polycarbonate insert is attached to the second silicone material by means of a tongue and groove fit and glue adhesive so as to provide a zero gap appearance. By a combination of tape and glue a medallion is then affixed to the insert.
The first silicone is attached to the interior wall by an adhesive that is brushed on the surface. However, an important design concept is the omission of adhesive on the interior surface around an area where the sole and bottom face are formed. This allows the relatively hard first silicone to shrink and expand in the no-adhesive zone rather than on the exposed side where the softer second silicone is placed. This reduction of shrinkage at the outer part of the first silicone reduces the amount of “peeling,” or pulling away, between the two silicones and/or between the silicone material and the cavity walls.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which form a part of the specification and are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

FIG. 1 is a perspective view of the back of a cast steel golf club head body according to the present invention; and

FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1.

FIG. 3 is a front view of an iron-type golf club head;

FIG. 4 is a front view of a hollow bodied golf club head;

FIG. 5 is a chart illustrating volumetric bias relative to a face center location for each club in a plurality of sets of golf clubs in accordance with the present invention; and

FIG. 6 is a chart illustrating volumetric bias relative to a shaft axis for each club in a plurality of sets of golf clubs in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1-2, golf club head 10 is constructed in accordance with a preferred embodiment of this invention. It includes a cavity back body 12, preferably cast, having a front striking face 14, interior surface 16, a hosel portion 18, a heel portion 20, a toe portion 22, an upper edge 24 and lower edge 26. The body 12 includes a cavity 28 that is defined by the interior surface 16.
In the preferred embodiment, the cavity 28 is preferably formed in the body 12 during the casting process, but may also be formed subsequently by machining. Cavity 28 is substantially filled with a hot molded silicone. The hot molded silicone is disposed into the cavity 28 in two separate shots. The first shot is of a precise pre-cut amount of relatively hard hot molded silicone 34, which when disposed is contiguous to a substantial portion of the interior surface 16 of the body 12. The first silicone has a Shore A hardness between about 70 to 80, preferably 80, which in addition to shrinking less than a softer silicone, provides a stiff support for the second shot of silicone 36. The second shot of silicone has a Shore A hardness of about 40-50, preferably about 50, and juxtaposes against the outer surface of the first silicone 34.
Prior to inserting any silicone, the rear surface 16 of the body is prepared by an adhesive that is brushed on the surface 16, with the exception that the adhesive is omitted on the lower front region designated as a no-adhesive zone X in FIG. 2. This is a critical design concept of the invention, as it allows the relatively hard first silicone 34 to shrink and expand in the no-adhesive zone X region rather than on the exposed side where the softer second silicone 36 is placed. This reduction of shrinkage at the outer part of the first silicone 34 reduces the amount of “peeling” between the two silicones 34, 36, and/or by the material pulling away from the cavity 41 walls. The employment of the harder 80A first silicone 34 accomplishes two things: first, there is less shrinkage than there would be with a softer silicone, and secondly, when combining the dual durometer silicones 34, 36, a superior damping effect is obtained than that which would be expected by a one hardness silicone.
The softer second silicone 36 has a highly durable polycarbonate insert 38 attached to it by means of a tongue and groove fit as shown in detail B. The tongue and groove fit of insert 38 provides a zero gap appearance for the back view of the club head and insert 38 may be bound to the second silicone 36 by a glue adhesive. A decorative oval medallion 40 is placed into a pocket of the polycarbonate insert 38 with a combination of tape and glue, the medallion 40 having a logo or some form of indicia on its outer wall. The adhesives and glue are commercially available and well known to those skilled in the art.
The present invention creates a vibration dampening golf club that also absorbs some of the impact noise. Since the hot molded dual durometer silicones 34, 36, are less dense than the metal material that would have filled the cavity 28, the mass moment of inertia of the golf club head 10 is increased. Substituting lightweight silicone, in lieu of a denser metal material, allows for the club head 10 to be larger without increasing its overall weight. Preferably, the silicone material has a density of about 1.2 grams/cc. This provides for an iron to have a larger sweet spot and thereby inherently making it easier to hit.
The use of silicone is restricted to the shorter irons (8, 9, pitching wedge (PW), gap wedge (GW), sand wedge (SW) and lob wedge), while the 3 through 7 irons, hybrids and/or utility clubs complete the golf club set. Principles of the present invention can be seen employed in the King Cobra TRANSITION-S™ model irons which are also depicted in co-pending and commonly owned Design Pat. Application No. 29/278,316, which is incorporated herein, in its entirety by reference thereof. For two exemplary sets of the King Cobra TRANSITION-S™ irons, the following charts indicate the amounts of steel, silicone, and polycarbonate that comprise each club head. It should be appreciated that any type of steel may be used throughout the set and multiple types of steel may be used throughout the set. For example, in an embodiment the 3 through 7 golf clubs are constructed of 17-4 stainless steel and the 8 through SW clubs are constructed from 431 stainless steel.

Embodiment 1

		Top of
		Hosel	Steel	Silicone	Polycarbonate
	Loft Angle	Volume	Volume	Volume	Volume
Loft #	(deg.)	(cc)	(cc)	(cc)	(cc)

3	20	101	na	na	na
4	23	98	na	na	na
5	26	96	na	na	na
6	29	70	na	na	na
7	33	70	na	na	na
8	36	59	33	24	2
9	40	59	34	23	2
PW	44	58	36	21	2
SW	56	65	35	29	1

Embodiment 2

3	20	105	na	na	na
4	23	103	na	na	na
5	26	99	na	na	na
6	29	74	na	na	na
7	33	73	na	na	na
8	36	59	33	24	2
9	40	60	34	23	3
PW	44	59	36	21	2
GW	50	57	37	18	2
SW	56	66	35	29	2

Silicone Density = 1.2 gms/cc
Polycarbonate (Medallion) Density = 1.1 gms/cc
Stainless Steel Density = 7.75 gms/cc

Dynamic Mechanical Analysis (DMA) measurements using the tension mode of the DMA are quite helpful in establishing tan delta, storage and loss modulus of the two silicones 34, 36. Hardness is similar to a complex modulus, which is separated as storage and loss modulus. Storage modulus is the resilient component of stiffness, and loss modulus is the dampening component of stiffness. Tan delta is computed from the ratio of loss modulus divided by the storage modulus and the smaller the tan delta ratio, the more viscous the material.
The tables below depict some of the values that are desirable when discussing the relationship between the two silicones of varying Shore A hardness.

DMA Tan Delta First Silicone Material (80 A)

(@ Ambient Temperature)

	Amplitude (microns)	1 Hz	10 Hz	50 Hz

25	0.08	0.09	0.10
50	0.10	0.10	0.12
100	0.11	0.12	0.14

DMA Tan Delta Second Silicone Material (50 A)

(@ Ambient Temperature)

	Amplitude (microns)	1 Hz	10 Hz	50 Hz

25	0.04	0.04	0.06
50	0.04	0.04	0.06
100	0.04	0.05	0.06


DMA	Storage Modulus	Loss Modulus
1 Hz Frequency	@ Ambient	@ Ambient
100 Micron Amplitude	Temperature (MPa)	Temperature (MPa)

First Silicone (80 A)	14.4	1.5
Second Silicone (50 A)	2.5	0.1

The above results were conducted by using the tension mode of a DMA instrument manufactured by TA Instruments, Inc. of New Castle, Del. The tan delta, storage modulus and loss modulus were obtained by taking a sample of the silicone materials and cutting to about 3 mm thick by 9 mm wide and about 24 mm of lengths. The length section is placed between the tension mode clamps of a Model 2980 DMA instrument. The DMA is operated with the oven in the up/open position and the sample is equilibrated to room temperature (about 23.0±2.0° C.). The instrument was set to frequencies of 1, 10, and 50 Hz and incremented in amplitude to 25, 50 and 100 microns for each frequency. A static force of 1.5N is applied to the clamped sample.
As described above, a golf club set of the present invention may include a combination of both hollow bodied and solid bodied club constructions such as iron-type clubs, hybrid-type and/or utility type clubs. In particular, a golf club set in accordance with the present invention includes a plurality of utility-type clubs, a plurality of hybrid-type clubs and a plurality of iron-type clubs. For example, in an embodiment the golf club set that includes a 3-iron equivalent through a sand wedge, utility-type clubs make up equivalents for the 3-iron, 4-iron and 5-iron; hybrid-type clubs make up equivalents for the 6-iron and 7-iron; and the 8, 9, pitching wedge, gap wedge and sand wedge are iron-type golf clubs. In that embodiment, the utility-type clubs generally have volumes ranging from 90 cc to 115 cc (preferably, 95 cc to 110 cc), the hybrid-type clubs generally have volumes ranging from 65 cc to 85 cc (preferably 70 cc to 80 cc), and the iron-type golf clubs generally have volumes ranging from 50 cc to 75 cc (preferably 55 cc to 70 cc).
In the exemplary embodiments, the construction type of clubs through out the set are correlated to sequential ranges of loft angle. For example, in an embodiment, the 3-iron, 4-iron, and 5-iron equivalents have a utility-type construction and generally have loft angles in a range of 19 degrees to 28 degrees, with the 3-iron having the lowest loft angle and the 5-iron having the greatest loft angle in that group. Similarly, the 6-iron and 7-iron equivalents have a hybrid-type construction and generally have loft angles in a range of 29 degrees to 35 degrees, with the 6-iron equivalent having a loft angle that is lower than that of the 7-iron equivalent. Finally, the 8-iron through lob wedge have an iron-type construction and generally have loft angles in a range of 36 degrees to 65 degrees with the 8-iron having the lowest loft angle and the remainder having sequentially greater loft angles.
It should be appreciated that the volume ranges may vary. For example, the utility-type clubs may have volumes in a range of 85 cc to 300 cc, the hybrid-type clubs may have volumes in a range of 60 cc to 90 cc, and the iron-type clubs may have volumes in a range of 45 cc to 80 cc. Preferably, the iron-type golf clubs have volumes above 45 cc. The overlap of the volume ranges and the relatively large volumes of the iron-type golf clubs provide a golf club set that provides an appearance of smooth transition between the different styles of club and the large size gives the user confidence in their ability to properly strike a golf ball.
Throughout the set of clubs, groups of clubs are created with a pre-selected bias so that each club within the group has a tendency to create a desired ball flight shape, such as a fade or draw, or straight ball flight. The pre-selected bias is created by locating the center of gravity of the club head relative to the face center of the club's striking face and relative to the shaft, or hosel, axis, thereby taking advantage of the interaction between the club head and the golf ball at impact to impart side spin on the golf ball having a desired amplitude and direction. For example, to create a draw flight shape, the center of gravity may be located on the heel side of the face center.
The groups of clubs are constructed to have biases within a pre-selected range, but the clubs within any group need not be limited to a single construction type. Groups of clubs in the golf club set may include clubs having multiple construction types (e.g., utility-type construction, hybrid-type construction, iron-type construction). Preferably, the groups of clubs are contiguous so that a sequential progression through the golf club set corresponds to a sequential progression through the groups of clubs. For example, a first group of clubs in a set corresponds to a 3-iron through a 5-iron, or equivalents, and each club in the group has a bias in a first range. A second group of clubs in the set corresponds to a 6-iron and a 7-iron, or equivalents, and each club in the group has a bias in a second range. A third group of clubs in the set corresponds to at least an 8-iron, and a 9-iron, or equivalents, and each club in the group has a bias in a third range. The third group may also include any or all of a pitching wedge, a gap wedge, a sand wedge, and a lob wedge. In an example, each group of clubs is limited to a single construction type.
Because any group may have golf clubs of a plurality of construction types and associated differences in volume, it is useful to quantify the bias on a unit volume basis, referred to herein as volumetric bias (VB), which may be determined from any reference location within the club head. The ranges of volumetric bias relative to the face center location (VB_X) and relative to the shaft, or hosel, axis (VB_A) are selected for each group of golf clubs in the set in accordance with the present invention.
In order to determine VB_X, the distance X between the face center and the center of gravity, illustrated in FIGS. 3 and 4, is divided by the volume (V) of the club head and the value is multiplied by 100 as shown in the formulas below. Similarly, in order to determine VB_A, the distance A between the center of gravity and the shaft axis, illustrated in FIGS. 3 and 4, is divided by the volume (V) of the club head and the value is multiplied by 100, also as shown in the formulas below.
VB _X=(X/V)*100
VB _A=(A/V)*100
The following tables, and the charts of FIGS. 5 and 6, provide VB_Xand VB_Avalues for various embodiments of golf club sets in accordance with the present invention where the distance (X or A, respectively) is in inches and the volume (V) is in cubic inches.


	VB_X(in⁻²)

Loft #	Ex. 1	Ex. 2	Ex. 3	Ex. 4	Ex. 5	Ex. 6

3	2.26	2.20	2.20	2.20	1.56	1.25
4	2.31	3.09	3.09	3.09	1.59	1.27
5	2.88	3.23	3.23	3.23	1.65	1.32
6	2.41	2.41	1.88	4.35	5.76	5.31
7	0.66	0.66	4.52	2.12	5.83	5.39
8	4.88	4.88	4.88	4.88	2.78	2.22
9	4.42	4.42	4.42	4.42	2.73	2.18
P	2.62	2.62	2.62	2.62	2.78	2.22
G	2.75	2.75	2.75	2.75	2.87	2.30
S	2.88	2.88	2.88	2.88	2.48	1.99


	VB_A(in⁻²)

Loft #	Ex. 1	Ex. 2	Ex. 3	Ex. 4	Ex. 5	Ex. 6	Ex. 7	Ex. 8

3	1.13	1.15	1.15	1.15	0.95	1.24	1.10	1.19
4	1.12	1.11	1.11	1.11	0.97	1.26	1.12	1.21
5	1.17	1.16	1.16	1.16	1.01	1.31	1.16	1.26
6	1.96	1.96	1.96	1.85	1.62	1.89	1.69	1.82
7	2.04	2.04	1.93	2.04	1.64	1.92	1.71	1.85
8	2.65	2.65	2.65	2.65	2.20	2.71	2.29	2.46
9	2.65	2.65	2.65	2.65	2.17	2.67	2.25	2.42
P	2.69	2.69	2.69	2.69	2.20	2.71	2.29	2.46
G	2.54	2.54	2.54	2.54	2.28	2.81	2.37	2.54
S	2.46	2.46	2.46	2.46	1.97	2.42	2.05	2.20

In an embodiment of the present invention, the golf club set includes three groups of clubs that correspond to construction types of golf club. Each group of clubs includes clubs having VB_Xand VB_Avalues in a predetermined range of values. For example, each club in a first group of clubs has a VB_Xvalue in a range of 1.20 to 3.30, and preferably in a range of 1.25 to 1.70, as shown by box 50 of FIG. 5. Each club in a second group has a VB_Xvalue in the range of 0.50 to 5.90, and preferably in the range of 5.25 to 5.90, as shown by box 52 of FIG. 5. Each club in a third group has a VB_Xvalue in the range of 1.90 to 5.00, and preferably in the range of 1.95 to 2.90, as shown by box 54 of FIG. 5.
Regarding VB_Avalues, the first group has a VB_Avalue in the range of 0.90 to 1.45, and preferably in the range of 1.05 to 1.30, as shown by box 56 of FIG. 6. The second group has a VB_Avalue in the range of 1.45 to 2.10, and preferably in the range of 1.60 to 1.95, as shown by box 58 of FIG. 6. The third group has a VB_Avalue in the range of 1.85 to 2.85, and preferably in the range of 2.00 to 2.60, as shown by box 60 of FIG. 6.
Additionally, in the above described embodiments, the distance of the center of gravity from the face center of the striking face in an aft direction (i.e., the depth into the page as shown in FIGS. 3 and 4) for each group of clubs is in a pre-selected range. In the first group of clubs, that distance is between 0.65 inch and 0.72 inch. In the second group of clubs, that distance is between 0.45 inch and 0.52 inch. In the third group of clubs, that distance is between 0.34 inch and 0.46 inch.
In accordance with the present invention, it will be appreciated that various aspects of the invention, as well as combinations thereof provide a golf club with an improved manner of locating the center of gravity and redistributing weight from central portions of the golf club to perimeter portions of the club head. While various descriptions of the present invention are described above, it is understood that the various features of the present invention can be used singly or in combination thereof. Therefore, this invention is not to be limited to the specifically preferred embodiments depicted therein.
While it is apparent that the illustrative embodiments of the invention disclosed herein fulfill the objectives stated above, it is appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. Elements from one embodiment can be incorporated into other embodiments. Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments, which would come within the spirit and scope of the present invention.

Claims

1. A set of golf clubs, comprising:

a first golf club including a first club head having a first striking face, a first construction type, a first volume and a first volumetric bias relative to a face center of the first striking face;

a second golf club including a second club head having a second striking face, a second construction type, a second volume and a second volumetric bias relative to a face center of the second striking face; and

a third golf club including a third club head having a third striking face, a third construction type, a third volume and a third volumetric bias relative to a face center of the third striking face,

wherein the first volume is greater than the second volume and the first volumetric bias is less than the second volumetric bias and wherein a center of gravity of each club head is spaced rearward from the striking face of the club head.

2. The set of golf clubs of claim 1, wherein the third volume is less than the first volume and the third volumetric bias is less than the second volumetric bias.

3. The set of golf clubs of claim 1, wherein the first volumetric bias is in a range of 1.20 to 3.30, the second volumetric bias is in a range of 0.50 to 5.90, and the third volumetric bias is in a range of 1.90 to 5.00.

4. The set of golf clubs of claim 3, wherein the first volumetric bias is in a range of 1.25 to 1.70, the second volumetric bias is in a range of 5.25 to 5.90, and the third volumetric bias is in a range of 1.95 to 2.90.

5. The set of golf clubs of claim 1, wherein the first club head has a fourth volumetric bias relative to the hosel axis that is less than a fifth volumetric bias relative to the hosel axis of the second club head, which is less than a sixth volumetric bias relative to the hosel axis of the third club head.

6. The set of golf clubs of claim 5, wherein the fourth volumetric bias is in a range of 0.90 to 1.45, the fifth volumetric bias is in a range of 1.45 to 2.10, and the sixth volumetric bias is in a range of 1.85 to 2.85.

7. The set of golf clubs of claim 6, wherein the fourth volumetric bias is in a range of 1.05 to 1.30, the fifth volumetric bias is in a range of 1.60 to 1.95, and the sixth volumetric bias is in a range of 2.00 to 2.60.

8. The set of golf clubs of claim 1, wherein the first construction type is a utility-type construction, the second construction type is a hybrid-type construction, and the third construction type is an iron-type construction.

9. The set of golf clubs of claim 8, wherein the first volume is in a range of 85 cubic centimeters to 300 cubic centimeters, the second volume is in a range of 60 cubic centimeters to 90 cubic centimeters, and the third volume is in a range of 45 cubic centimeters to 80 cubic centimeters.

10. The set of golf clubs of claim 9, wherein the first volume is in a range of 95 cubic centimeters to 110 cubic centimeters, the second volume is in a range of 70 cubic centimeters to 80 cubic centimeters, and the third volume is in a range of 55 cubic centimeters to 70 cubic centimeters.

11. The set of golf clubs of claim 1, wherein the third construction-type is an iron-type construction and the third volume is between 45 cubic centimeters and 80 cubic centimeters.

12. The set of golf clubs of claim 1, wherein the first golf club has a loft angle in a range of 19 degrees to 28 degrees, the second golf club has a loft angle in a range of 29 degrees to 35 degrees, and the third golf club has a loft angle in a range of 36 degrees to 65 degrees.

13. The set of golf clubs of claim 1, wherein the third club head comprises a body defining a cavity, a silicone material filling at least a portion of the cavity and a polycarbonate insert attached to the silicone material.

14. A set of golf clubs, comprising:

a first plurality of golf clubs, wherein each of the first plurality of golf clubs includes a club head having a volumetric bias relative to a face center of a striking face in a range of 1.25 to 1.70; and

a second plurality of golf clubs, wherein each of the second plurality of golf clubs includes a club head having a volumetric bias relative to a face center of a striking face in a range of 1.95 to 2.90,

wherein the first plurality of golf clubs comprise generally hollow club heads and wherein a center of gravity of each club head is spaced rearward from the striking face of the club head.

15. The set of golf clubs of claim 14, further comprising a third plurality of golf clubs, wherein each of the third plurality of golf clubs includes a club head having a volumetric bias relative to a face center of a striking face in a range of 5.25 to 5.90.

16. The set of golf clubs of claim 15, wherein the first plurality of golf clubs have loft angles in a range of 19 degrees to 28 degrees, the second plurality of golf clubs have loft angles in a range of 36 degrees to 65 degrees, and the third plurality of golf clubs have loft angles in a range of 29 degrees to 35 degrees.

17. The set of golf clubs of claim 14, wherein the first plurality of golf clubs have a utility-type construction, the second plurality of golf clubs have an iron-type construction, and the third plurality of golf clubs have a hybrid-type construction.

18. The set of golf clubs of claim 15, wherein the club heads of the first plurality of golf clubs have volumes in a range of 85 cubic centimeters to 300 cubic centimeters, the club heads of the second plurality of golf clubs have volumes in a range of 45 cubic centimeters to 80 cubic centimeters, and the club heads of the third plurality of golf clubs have volumes in a range of 60 cubic centimeters to 90 cubic centimeters.

19. The set of golf clubs of claim 18, wherein the club heads of the first plurality of golf clubs have volumes in a range of 95 cubic centimeters to 110 cubic centimeters, the club heads of the second plurality of golf clubs have volumes in a range of 55 cubic centimeters to 70 cubic centimeters, and the club heads of the third plurality of golf clubs have volumes in a range of 70 cubic centimeters to 80 cubic centimeters.

20. The set of golf clubs of claim 14, wherein each of the club heads of the second plurality of golf clubs comprises a body defining a cavity, a silicone material filling at least a portion of the cavity and a polycarbonate insert attached to the silicone material.