U.S. patent application number 12/230611 was filed with the patent office on 2009-03-19 for golf club head.
This patent application is currently assigned to SRI Sports Limited. Invention is credited to Tomoya Hirano.
Application Number | 20090075752 12/230611 |
Document ID | / |
Family ID | 40455092 |
Filed Date | 2009-03-19 |
United States Patent
Application |
20090075752 |
Kind Code |
A1 |
Hirano; Tomoya |
March 19, 2009 |
Golf club head
Abstract
A hollow golf club head has a head volume of not less than 430
cc, a lateral moment of inertia of from 5000 to 5900 g sqcm, and a
club head thickness of from 45 to 58 mm. In a vertical plane
including a sweet spot and the center of gravity of the head,
preferably, a crown surface length measured along the upper outer
surface of the club head from an upper edge of a club face to the
rearmost point of the club head is set in a range of from 1.02 to
1.20 times a sole surface length measured along the lower outer
surface of the club head from a lower edge of the club face to the
rearmost point of the club head.
Inventors: |
Hirano; Tomoya; (Kobe-shi,
JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
SRI Sports Limited
|
Family ID: |
40455092 |
Appl. No.: |
12/230611 |
Filed: |
September 2, 2008 |
Current U.S.
Class: |
473/345 |
Current CPC
Class: |
A63B 53/0412 20200801;
A63B 53/0408 20200801; A63B 53/0466 20130101 |
Class at
Publication: |
473/345 |
International
Class: |
A63B 53/04 20060101
A63B053/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 14, 2007 |
JP |
2007-239679 |
Claims
1. A hollow golf club head having a head volume of not less than
430 cc, a lateral moment of inertia of from 5000 to 5900 g sqcm,
and a club head thickness of from 45 to 58 mm.
2. The head according to claim 1, wherein in a vertical plane
including a sweet spot and the center of gravity of the head, a
crown surface length measured along the upper outer surface of the
club head from an upper edge of a club face to the rearmost point
of the club head is more than a sole surface length measured along
the lower outer surface of the club head from a lower edge of the
club face to the rearmost point of the club head.
3. The head according to claim 1, wherein in a vertical plane
including a sweet spot and the center of gravity of the head, a
crown surface length measured along the upper outer surface of the
club head from an upper edge of a club face to the rearmost point
of the club head is in a range of from 1.02 to 1.20 times a sole
surface length measured along the lower outer surface of the club
head from a lower edge of the club face to the rearmost point of
the club head.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a golf club head capable of
reducing the variation in the carry distance of a struck ball and
thereby increasing the carry distances in totality.
[0002] The directional stability of a struck ball is an important
factor for stabilizing the carry distance. If the ball is struck
off-center, the club head is moved or rotates around the center of
gravity of the head more or less. If such a rotational movement of
the club head at the time of off-center shot is reduced, then the
lunching direction of the struck ball is stabilized.
[0003] In recent years, on the other hand, large-sized various
wood-type golf club heads have been proposed. Usually, the
large-sized golf club heads are increased in the lateral moment of
inertia and vertical moment of inertia.
[0004] If the vertical moment of inertia is increased, then the
vertical gear effect becomes reduced, therefore, if the ball
hitting position is off the sweet spot upward or downward, the
carry distance tends to decrease.
[0005] AS well known in the art, the vertical gear effect is as
follows. If the ball hitting position is off the sweet spot SS
upwards or downwards, then as shown in FIG. 6, with respect to a
horizontal axis extending in the toe-heel direction passing through
the center of gravity G of the head, there is caused a moment which
is a product of the impact force F received from the golf ball (b)
and the distance L1 or L2 between the hitting position and the
center of gravity G measured perpendicular to the direction of the
force F. As a result, the club head is rotated around the
horizontal axis by a small angle.
[0006] Due to the frictional engagement between the golf ball and
the club face (f), the contact surface of the golf ball receives a
force in the reverse direction to the rotational direction of the
club head like a gear. As a result, the backspin of the struck ball
is decreased in the case of an upper hitting position or increased
in the case of a lower hitting position.
[0007] In consequence, in the case of the golf club heads whose
vertical moment of inertia is large where the rotational movement
is decreased as explained above, if the ball hitting position is
off the sweet spot upward, the backspin can not be fully
decreased.
[0008] On the other hand, due to the face roll having a radius of
curvature Y, in the case of the upper hitting position, when
compared with the sweet spot SS, the loft angle becomes increased
and the launch angle of the struck ball is also increased. As a
result, the ballistic course is very liable to become a rising
trajectory and thereby the carry distance is decreased.
[0009] Contrary, in the case of the lower hitting position, the
backspin can not be fully increased, and the launch angle of the
ball is decreased. As a result, the ball tends to drop quickly and
thereby the carry distance is decreased.
[0010] Thus, in the case of a large-sized golf club head, due to
the relatively large vertical moment of inertia, there is a
tendency that the carry distance varies wide depending of the ball
hitting position.
SUMMARY OF THE INVENTION
[0011] It is therefore, an object of the present invention to
provide a golf club head in which, by increasing the lateral moment
of inertia and decreasing the thickness of the club head, the
vertical moment of inertia is decreased on the whole, and thereby
the variation in the carry distance can be reduced.
[0012] According to the present invention, a hollow golf club head
has a head volume of not less than 430 cc, a lateral moment of
inertia of from 5000 to 5900 g sqcm, and a club head thickness of
from 45 to 58 mm.
[0013] Therefore, the vertical moment of inertia is decreased. As a
result, even if the ball hitting position is off the sweet spot
upward or downward, the struck ball benefits from the vertical gear
effect and the decrease in the carry distance is controlled.
[0014] Further, since the lateral moment of inertia is very large,
even if the ball hitting position is off the sweet spot toward the
toe or heel, the lateral movement of the club head becomes very
small, and the directional stability of the struck ball is
improved, therefore, the decrease in the carry distance is
controlled.
DEFINITIONS
[0015] In this specification, sizes, positions, directions and the
like relating to the club head refer to those under a standard
state of the club head unless otherwise noted.
[0016] Here, the standard state of the club head 1 is such that the
club head is set on a horizontal plane HP so that the center line
CL of the club shaft (not shown) is inclined at the lie angle
(alpha) while keeping the club shaft center line CL on a vertical
plane VP1, and the club face 2 forms its loft angle (beta) with
respect to the horizontal plane HP. Incidentally, in the case of
the club head alone, the center line of the shaft inserting hole
(h) can be used instead of the center line of the club shaft.
[0017] Lateral moment of inertia Ma is the moment of inertia around
a vertical axis A1 passing through the center of gravity G in the
standard state.
[0018] Vertical moment of inertia Mb is the moment of inertia
around a horizontal axis A2 passing through the center of gravity G
in the heel-and-toe direction of the head in the standard
state.
[0019] Sweet spot SS is the point of intersection between the club
face and a straight line N drawn normally to the club face 2
passing the center of gravity G of the head.
[0020] Back-and-forth direction is a direction parallel with the
above-mentioned straight line N projected on the horizontal plane
HP.
[0021] Heel-and-toe direction is a direction TH parallel with the
horizontal plane HP and perpendicular to the back-and-forth
direction.
[0022] Club head thickness H is the height measured from the
horizontal plane HP to the highest point (m) on the crown portion
of the club head, namely, the highest point of the head excluding
the upwardly protruding hosel portion if any.
[0023] Sweet spot height GH is a height of the sweet spot Ss
measured from the horizontal plane HP.
[0024] Face progression FP is the horizontal distance between the
leading edge Le of the club head and the vertical plane VP1
including the club shaft center line CL, measured in a vertical
plane VP3 including the sweet spot SS and the center of gravity
G.
[0025] Leading edge Le is a contact point between the club face 2
and a vertical plane VP2 parallel with the vertical plane VP1.
[0026] Gravity point depth GL is the horizontal distance between
the center of gravity G and the vertical plane VP2.
[0027] Wood-type golf club is meant for at least number 1 to 5
woods, and clubs comprising heads having similar shapes may be
included.
[0028] If the edge (2a and 2b) of the club face 2 is unclear due to
smooth change in the curvature, as shown in FIGS. 5(a) and 5(b), a
virtual edge line (Pe) defined based on the curvature change is
used instead as follows. In each cutting plane E1, E2--including
the sweet spot sS and the center G of gravity of the head, a point
Pe at which the radius (r) of curvature of the profile line Lf of
the face portion first becomes under 200 mm in the course from the
center ss to the periphery of the club face is determined. Then,
the virtual edge line is defined as a locus of the points Pe.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a front view a club head according to the present
invention.
[0030] FIG. 2 is a top view of the club head.
[0031] FIG. 3 is a cross sectional view taken along a vertical
plane (line A-A in FIG. 2) including the sweet spot and the center
of gravity of the club head.
[0032] FIG. 4 is a heel-side side view of the club head.
[0033] FIG. 5(a) and FIG. 5(b) are a front view and a cross
sectional view of a face portion of a head for explaining the edge
of the club face.
[0034] FIG. 6 is a cross sectional view for explaining a vertical
gear effect of a club head.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] In the drawings, golf club head 1 according to the present
invention is a wood-type hollow golf club head. The head 1
comprises a face portion 3 whose front face defines a club face 2
for striking a ball; a crown portion 4 intersecting the club face 2
at the upper edge 2a thereof; a sole portion 5 intersecting the
club face 2 at the lower edge 2b thereof; a side portion 6 between
the crown portion 4 and sole portion 5; and a hosel portion 7
disposed at the heel-side end to be attached to an end of a club
shaft inserted into a shaft inserting hole (h). The club head 1 is
provided a shell structure with thin walls having a closed hollow
(i).
[0036] The club face 2 is provided with a face roll (a curvature
from crown to sole) of a radius of curvature PR, and a face bulge
(a curvature from heel to toe) of a radius of curvature RB.
[0037] The outer surface of the crown portion 4 is convexly curved.
Thus, apart from the hosel portion 7, the highest point (m) is
positioned within the outer surface of the crown portion 4.
[0038] The hosel portion 7 has a tubular portion protruding
upwardly from the crown portion 4 and defining the shaft inserting
hole (h).
[0039] The outer surface of the hosel portion 7 is connected to the
outer surface of the crown portion 4 through a transitional concave
curve.
[0040] The side portion 6 can be formed to extend continuously from
the toe to the heel through the rear of the head. But, in this
embodiment, the side portion 6 is formed discontinuously.
[0041] In this embodiment, the club head 1 is made of metal
materials. But, in order to reduce the club head weight and/or to
adjust the position of the center of gravity G of the head, a fiber
reinforced resin can be used together with the metal materials.
Preferably used are metal materials having a large specific tensile
strength, for example, stainless steels, maraging steels, pure
titanium, titanium alloys, magnesium alloys aluminum alloys and the
like are. In the case of the titanium alloys, for example
Ti-6Al-4V, Ti-15V-3Cr-3Al-3Sn, Ti-15Mo-5Zr-3Al, Ti-13V-11Cr-3Al and
the like are be preferably used.
[0042] The club head 1 is manufactured by assembling a plurality of
parts (usually 2 to 5 parts) each prepared by an appropriate
method, for example, casting, rolling, forging, pressure molding or
the like.
[0043] The volume of the club head 1 is set in a range of not less
than 430 cc, preferably not less than 440 cc, more preferably not
less than 450 cc.
[0044] Such a large head volume can give the user easy feelings at
the time of addressing the ball and can increase the gravity point
depth GL and the lateral moment of inertia Ma so as to improve the
directional stability of the struck ball.
[0045] If the volume is less than 430 cc, it becomes difficult to
improve the directional stability of the struck ball.
[0046] If the volume is too large, on the other hand, problems
arise such as increase in the club head weight, deterioration of
swing balance, decrease in the durability and the like, therefore,
it is preferable that the volume is set to be not more than 600 cc,
preferably not more than 550 cc. If golf rules are considered, the
volume should be not more than 460 cc.
[0047] If the mass of the club head 1 is too small, then the
lateral moment of inertia is decreased, and also the kinetic energy
during swing is decreased, therefore, the improvement in the carry
distance can not be expected. If the mass of the club head 1 is too
large, on the other hand, it becomes difficult to swing the golf
club through the ball, and there is a possibility that the
directional stability of the struck ball is deteriorated and the
carry distance is decreased. In this light, the mass of the club
head is preferably not less than 180 g, more preferably not less
than 185 g, but preferably not more than 210 g, more preferably not
more than 205 g.
[0048] In the case that the club head is provided with a relatively
large volume of more than 430 cc and the area of the club face 2 is
relatively large as a necessary consequence, when the ball hitting
position is off the sweet spot towards the heel or toe, there is
possibility that the distance in the heel-and-toe direction between
the hitting position and the sweet spot becomes very large. Even in
such a condition, in order that the rotational movement (head
movement) of the club head 1 around the vertical axis A1 is surely
reduces to thereby stabilize the direction of the struck ball, the
lateral moment of inertia Ma should be large enough.
[0049] Therefore, the lateral moment of inertia Ma has to be
increased up to 5000 g sqcm at least. Preferably, the lateral
moment of inertia Ma is not less than 5300 g sqcm, more preferably
not less than 5500 g sqcm. However, if the lateral moment of
inertia Ma is too large, there is a possibility that the club head
weight becomes excessively heavy, and the shape of the club head
becomes extraordinary. Therefore, the lateral moment of inertia Ma
is at most 5900 g sqcm.
[0050] The present inventor discovered that the club head thickness
H and the vertical moment of inertia Mb have a certain correlation
and that the vertical moment of inertia Mb can be kept at small
values by reducing the club head thickness H.
[0051] According thereto, by limiting the club head thickness H
within a range of not more than 58 mm, preferably not more than 56
mm, more preferably not more than 55 mm, still more preferably not
more than 55 mm, the increase in the vertical moment of inertia Mb
can be restrained even when the head volume is increased up to 430
cc at least and also the lateral moment of inertia Ma is increased
up to 5000 g sqcm at least.
[0052] If the club head thickness H is too small, the sweet spot
area becomes narrow, and as a result, the carry distances are
liable to decrease. Therefore, the club head thickness H is
preferably set in a range of from not less than 45 mm, more
preferably not less than 47 mm, still more preferably not less than
49 mm.
[0053] In order to improve the carry distance stably, the vertical
moment of inertia Mb is preferably set in a range of not more than
5000 g sqcm, more preferably not more than 4500 g sqcm, still more
preferably not more than 4000 g sqcm.
[0054] If the vertical moment of inertia Mb becomes excessively
small, on the other hand, there is a tendency that the head
movement at impact increases, and the carry distance is decreased,
therefore, the vertical moment of inertia Mb is preferably not less
than 2500 g sqcm, more preferably not less than 2700 g sqcm, still
more preferably not less than 3000 g sqcm.
[0055] In the case of a golf club head having a large head volume
and a small club head thickness H, there is a tendency that the
center of gravity G of the head comes far away from the club shaft
center line CL, namely, as shown in FIG. 4, the distance K tends to
increase.
[0056] Accordingly, during swing, due to the centrifugal force, the
club head 1 is subjected to a rotational movement as indicated in
broken line such that the center of gravity G approaches the
extension of the club shaft center line CL when viewed from the
heel side of the head.
[0057] Such rotational movement is increased in proportion to the
increase in the head speed during swing and as a result, the
dynamic loft angle at impact is increased.
[0058] In other words, the loft angle is varied depending on the
swing speed, thus, it is difficult for the user to control the
ballistic course and carry distance of the ball.
[0059] In order to solve this problem, the club head 1 in this
example has a streamline shape, and the crown surface length LC is
set to be longer than the sole surface length LS.
[0060] As shown in FIG. 3, at least in the vertical plane VP3
including the center of gravity G and the sweet spot SS, the
contour of the crown portion 4 and the contour of the sole portion
5 are each defined by a smoothly curved arc line, and they are
extended continuously from the edge (2a, 2b) of the face portion to
the rearmost point BP and connected with each other at the point BP
without the side portion 6 therebetween. In this vertical plane
VP3, the crown surface length LC is defined as the length measured
along the outer surface of the crown portion 4 from the upper edge
2a of the club face 2 to the rearmost point BP, and
the sole surface length LS is defined as the length measured along
the outer surface of the sole portion 5 from the lower edge 2b of
the club face 2 to the rearmost point BP.
[0061] Thus, at least at the rearmost point BP, the side portion 6
is interrupted, and the head has a streamline shape.
[0062] Accordingly, during swing, the velocity of air flow along
the surface of the crown portion becomes faster than the velocity
of air flow along the surface of the sole portion, and the air
pressure to the crown portion becomes lower than the air pressure
to the sole portion, and the club head 1, in particular its rear
part, obtains lift. Therefore, the above-mentioned rotational
movement of the head is reduced, and the resultant increase of the
loft angle can be avoided, and thereby the carry distances become
stable.
[0063] If the ratio (LC/LS) of the crown surface length LC to the
sole surface length LS is less than 1.02, the lifting is still
insufficient. But, if the ratio (LC/LS) is more than 1.20, there is
a tendency that the lifting and the restraint of the increase in
the loft angle become excess. Therefore, the ratio (LC/LS) is
preferably not less than 1.02, more preferably not less than 1.05,
but preferably not more than 1.20, more preferably not more than
1.10, still more preferably not more than 1.09.
[0064] The crown surface length LC is preferably not less than 105
mm, more preferably not less than 108 mm, still more preferably not
less than 110 mm, but not more than 125 mm, more preferably not
more than 122 mm, still more preferably not more than 120 mm.
[0065] The sole surface length LS preferably not less than 100 mm,
more preferably not less than 103 mm, still more preferably not
less than 105 mm, but not more than 120 mm, more preferably not
more than 117 mm, still more preferably not more than 115 mm.
[0066] Incidentally, the ratio (LC/LS) can be changed for example
by setting the radius of curvature of the contour of the crown
portion 4 at smaller values than that of the sole portion 5 and by
decreasing the height BH of the rearmost point BP.
[0067] To decrease the height BH is preferable because the height
of the center of gravity G is also decreased thereby. In this
light, the height BH is preferably not more than 30 mm, more
preferably not more than 28 mm, still more preferably not more than
25 mm.
[0068] If the sweet spot height GH is too large, the backspin tends
to increase excessively. If the sweet spot height GH is too small
contrary, the backspin is decreased which tends to result in a drop
ball. In either case, the carry distance is decreased. Therefore,
the sweet spot height GH is preferably set in a range of not more
than 38 mm, more preferably not more than 36 mm, still more
preferably not more than 34 mm, but not less than 25 mm, more
preferably not less than 27 mm, still more preferably not less than
29 mm.
[0069] The face progression FP has influence upon the returning
motion of the club head from swing and upon the timing of impacting
the ball. By setting the face progression FP in a range of not less
than 17 mm, preferably not less than 19 mm, but not more than 28
mm, preferably not more than 26 mm, more preferably not more than
25 mm, the directional stability of the struck ball can be improved
to stabilize the carry distance.
[0070] If the gravity point depth GL is decreased, there is a
possibility that the lateral moment of inertia Ma becomes
decreased, therefore, the gravity point depth GL is preferably not
less than 30 mm, more preferably not less than 32 mm, still more
preferably not less than 33 mm. If the depth GL is too large, on
the other hand, the head tends to become insensitive to the impact
feeling. Further, the position of the sweet spot SS tends to become
high, and potential for off-center hit (lower hit) increases. It is
therefore preferable that the gravity point depth GL is set to be
not more than 60 mm, more preferably not more than 57 mm, still
more preferably not more than 55 mm.
[0071] In order to secure the lateral moment of inertia Ma and the
gravity point depth GL, the size HL of the club head 1 measured in
the back-and-forth direction from the leading edge Le to the
rearmost point BP, is preferably set in a range of not less than
110 mm, more preferably not less than 115 mm, but not more than 127
mm, more preferably not more than 125 mm.
[0072] Although the club head 1 is decreased in the club head
thickness H and the vertical moment of inertia Mb as explained
above, the vertical gear effect occurs more or less.
[0073] In this embodiment, the face roll is provided throughout the
club face 2 and the radius of curvature PR is set in a range of not
less than 12 inches, preferably not less than 14 inches, more
preferably not less than 16 inches, but not more than 25 inches,
preferably not more than 23 inches, more preferably not more than
21 inches. These specific values of the radius of curvature RR are
measured in the above-mentioned vertical plane VP3 for the part
between a point Pu 10 mm downward from the upper edge 2a along the
club face 2 and a point Pd 10 mm upward from the lower edge 2b
along the club face 2, as shown in FIG. 3.
[0074] In this embodiment, because of the relatively large lateral
moment of inertia Ma, even if the ball hitting position is off the
sweet spot towards the toe or heel, the sidespin of the struck ball
is not so increased. Therefore, it is preferable that the radius of
curvature RB of the face bulge is increased. Preferably, the radius
of curvature RB is set in a range of not less than 15 inches, more
preferably not less than 17 inches, still more preferably not less
than 20 inches, but not more than 50 inches, more preferably not
more than 45 inches, still more preferably not more than 40
inches.
[0075] In the plan view of the club head under the standard state,
the overall area of the club head is preferably set in a range of
not less than 115 sqcm, more preferably not less than 117 sqcm,
still more preferably not less than 120 sqcm. In other words, the
projected area of the head on the horizontal plane HP is so
limited. As a result, the lateral moment of inertia Ma can be
effectively increased, and it is possible to give the user easy
fillings when addressing the ball. If the projected area is too
large, on the other hand, violation of the golf rules or
regulations and an undesirable increase in the club head weight are
resulted, therefore, the projected area is preferably not more than
140 sqcm, more preferably not more than 137 sqcm, still more
preferably not more than 135 sqcm.
Comparison Tests
[0076] Wood-type hollow golf club heads were prepared and tested
for the carry distance and the directional stability of the struck
ball. All of the club heads had same structures and same
specifications except for the specifications shown in Table 1. The
volume, mass, lie angle and loft angle of the heads were 460 cc,
195 grams, 59 degrees and 11.5 degrees, respectively. The heads
were each made from a main part formed by casting a molten titanium
alloy Ti-6Al-4V, a face plate formed by forging a titanium alloy
Ti-5.5Al-1Fe, and a crown plate formed by forging a titanium alloy
Ti-15V-3Cr-3Al-3sn.
[0077] The main part was provided with a front opening and a top
opening. The face plate and crown plate were laser welded to the
main part so as to cover the front opening and the top opening,
respectively.
[0078] The moments of inertia Ma and Mb were adjusted by changing
the wall thicknesses of the sole portion, side portion and/or crown
portion.
[0079] Carry Distance Test:
[0080] Each head was attached to an FRP shaft (MP400, flex R,
manufactured by SRI Sports Limited) to make a wood club.
[0081] The club was mounted on a swing robot and hit three-piece
balls five times par each of the following three positions at a
head speed of 40 m/s.
[0082] Center: the sweet spot sS
[0083] upper: 5 mm above the sweet spot
[0084] Lower: 5 mm below the sweet spot
[0085] with respect to each of the three positions, the average
carry distance was calculated. Further, the average of all of the
positions was calculated. The results are shown in Table 1.
[0086] Variation in Carry Distance Test:
[0087] Using the above-mentioned golf clubs, each of ten golfers
having handicaps of 10 to 20 hit three-piece balls ten times par a
club.
[0088] With respect to each of the golfers, the difference between
the maximum carry distance and minimum carry distance was obtained.
Then, the average of the differences of the ten golfers was
calculated. The results are shown in Table 1, wherein the smaller
the value, the smaller the variation.
TABLE-US-00001 TABLE 1 Head Ex. 1 Ex. 2 Ex. 3 Ref. 1 Ex. 4 Ex. 5
Ex. 6 Club head thickness H (mm) 45.0 50.0 55.0 60.0 55.0 55.0 55.0
Lateral moment of inertia Ma (g sq cm) 5850.0 5640.0 5450.0 5070.0
5370.0 5350.0 5475.0 Vertical moment of inertia Mb (g sq cm) 3200
3350 3480 3360 3370 3400 3450 Crown surface length Lc (mm) 113.0
115.0 118.0 120.0 110.0 114.0 120.0 Sole surface length Ls (mm)
108.0 110.0 112.0 114.0 114.0 112.0 110.0 Ratio (Lc/Ls) 1.05 1.05
1.05 1.05 0.96 1.02 1.09 Sweet spot height GH (mm) 28.2 30.0 32.5
37.5 36.7 34.0 33.0 Gravity point depth GL (mm) 50.2 46.3 44.8 43.1
43.5 44 44.5 Face roll radius PR (inch) 17 17 17 17 17 17 17 Face
bulge radius RB (inch) 20 20 20 20 20 20 20 Club head projected
area (sq mm) 127 127 127 127 127 127 127 Average carry distance
(yard) Upper 218.3 217.9 216.3 213.5 214.2 215.6 216.1 Center 225.4
225.1 224.7 224.5 224.7 224.6 224.7 Lower 217 215.1 213.5 210.2
212.4 212.9 213.4 All 220.2 219.4 218.2 216.1 217.1 217.7 218.1
Variation of Carry distance (yard) 10.8 11.2 11.7 12.5 16.7 12.8
9.5
[0089] From the test results, it was confirmed that the decrease in
the carry distance at the time of upward or downward off-center
shot can be significantly controlled, and the stable carry
distances can be achieved.
* * * * *