RE: ShopTalk: Flat Faced Driver

[Tom Wishon]

TEDD: Thank you for your interest in all of this good stuff – if you can’t tell by now, I may lay claim to being the biggest nut of all about learning everything I can about every aspect of golf club performance!!    There used to be a formula that old wood makers used in trying to determine how much bulge radius was required for different types of woodhead designs.  It was based on the distance of the CG back from the face and basically said that when the CG is farther back from the face, the bulge needs to be more curved (smaller number of inches of radius) and when the CG is closer to the face, the bulge needs to be less curved (higher number of inches of radius).   But I can tell you that no one in the industry uses this because if they did, you would be seeing a lot more curve on the faces of all of the >400cc heads, which all have a more rear located CG than the old 200-250cc driver heads had.  The trend in design of the bulge has just been in essence to “pick a radius” that is within the typical range for drivers of 10” to 14” and go with that.  Personally, I tend to use a slight bit more bulge at 11” for a lot of my larger drivers because there will be more sidespin generated on an off center hit when the CG is farther back from the face.  Hence if the toe shot is going to develop a little more hooking side spin on a large driver head, you would use a little more curvature to help start the ball a little more off to the right from that toe shot.  Thus when the greater hook spin meets the more curve to start the ball off to the right a little more, the result is that the toe shot draws back to the fairway.   With less bulge curve that toe shot might draw back to the left edge of the fairway.    In truth, I have designed all sorts of driver sizes from 200cc to 450cc with bulges from 11 to 14 inches of radius and I honestly can’t say that I have ever noticed a visual difference in the amount of hook or fade spin from off center hits from either human or robot testing.  When I look at the OEM drivers, I do see that most of them tend to stay in the 10-12” bulge radius and I have rarely ever seen an OEM driver with 14” of bulge.  On fairway woods, this is where I see a LOT of difference in the bulge in that I see OEM fairway woods with 10-12” bulge, the same as their drivers.  This to me makes the fairways look too “roundy faced” and I don’t consider it a good thing to use that much curvature on the fairways.    I know why that happens after touring around a number of foundries and digging into it.   Because there are so many woodheads today made so that the face is a separate plate that is welded on its edges to the very front edge of the head body, when the foundry stamps the bulge and roll into the faces, it is easier to make this tooling die with the same radius for bulge as for roll.  Machining a die with the same radius in all directions is far easier to do than to machine a die with two different radii 90 degs apart from each other in orientation.  Hence this is why I see so many other woodheads made with the same bulge as the roll.     There is no real relationship between bulge and roll in terms of design technology.  In fact, because I am somewhat of a history nut on the equipment, I have never yet found any reference in my old digging into this that ever was able to explain why the old clubmakers even put vertical roll on a woodhead.   I do know that the bulge came from trial and error experimentation, and I have found articles in late 1800’s British golf magazines about this which explains that the clubmakers experimented with different radii until they came up with what they felt worked the best for controlling off center hits with the woodheads.   My belief after talking to a big time golf history friend years back is that the roll was added on by clubmakers who played billiards a lot and had the unjustified philosophy that in billiards a ball hits a ball, so why not make it the same in golf?   But truthfully, there is NO scientific performance related reason for roll to be on any woodhead.  Hence one of the reasons I moved in that direction to reduce roll starting some 6-7 yrs ago and this year to start reducing it almost to 0.    TOM       -----Original Message----- From: Childers, Tedd A [mailto:[EMAIL PROTECTED] Sent: Tuesday, August 31, 2004 12:16 PM To: [EMAIL PROTECTED] Subject: RE: ShopTalk: Flat Faced Driver   Tom,   That's what I thought, but I wasn't sure.  In general, do you use more bulge on a longer driver (heel/toe) or less, and what about roll in relation to face height (more or less for a taller face)?   Tedd   P.S.  Thanks for taking the time to answer these questions.  It is a real rarity to have someone so knowledgeable about the golf industry take the time to answer our questions and often explain (in detail) the many facets of clubhead and shaft design, production, etc...  You also share a lot of info about the OEMs that we simply cannot get from any other source.  I truly appreciate your time and your commitment to promoting custom clubmaking.     -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]On Behalf Of Tom Wishon Sent: Tuesday, August 31, 2004 2:54 PM To: [EMAIL PROTECTED] Subject: RE: ShopTalk: Flat Faced Driver TEDD:   Because bulge and roll are both a radius, that means the smaller the number of the radius, the more curved it will be.  Hence a 10” bulge will look more curved than will a 12” and so on.     TOM       -----Original Message----- From: Childers, Tedd A [mailto:[EMAIL PROTECTED] Sent: Tuesday, August 31, 2004 9:58 AM To: [EMAIL PROTECTED] Subject: RE: ShopTalk: Flat Faced Driver   Tom,   With regard to bulge and roll, will a 10" or a 12" bulge/roll appear to have more curvature, assuming all other specs are the same?  Put another way, is a larger bulge/roll indicative of more or less curvature?    Tedd -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]On Behalf Of Tom Wishon Sent: Tuesday, August 31, 2004 10:44 AM To: [EMAIL PROTECTED] Subject: RE: ShopTalk: Flat Faced Driver Graham:   I can shed a little experience on this matter of no bulge woods that might help your customer think a little about this.  Way back in the wood wood days I had a chance to be part of a little testing in which we made woods with a true flat face from heel to toe.   I remember setting up a test group of golfers which consisted of players from low single digit up to high 20’s handicappers.  First guy up was the 2 hdcp player.  He takes the 0 bulge driver, tees it up and hits it absolutely dead straight.  My eyes almost come out of my head as I can’t believe he pured this shot so straight.  So I quickly get him to tee up another one and he hits this wild hook that goes no where but low left.  I wipe the sweat from my brow and tell him,  do you have ANY idea how perfectly you hit that first one?   Reason being that the only place you can hit a dead straight shot from a no bulge driver is right dead center in line with the head’s center of gravity.  Using impact labels on the face to note point of impact we found that even shots hit 1/8” (3.2mm) off center caused some curving side spin on the shot.  And as the off center hit went to ¼”  (6.5mm) and more, it turned very ugly in terms of the curving nature of the shot – hooking when impact was on the toe side of the CG and fading when on the heel side.    As driver heads have become larger, the width of the face is also much greater.  When you put the same radius of say 10” or 12” across the face for the bulge, that longer face width makes the same radius look more rounded to the eyes.  This is undoubtedly what your golfer is seeing that he dislikes.  In terms of if there are any drivers out there with greatly reduced bulge I don’t think so – at least I have not heard of anyone making substantially reduced bulge drivers today.   You could ask to have a driver hand selected for a little less bulge based on the +/- tolerance that would come along with any driver in production, but generally that tolerance is not usually any more than +/- 1”.    TOM     -----Original Message----- From: Childers, Tedd A [mailto:[EMAIL PROTECTED] Sent: Tuesday, August 31, 2004 5:42 AM To: [EMAIL PROTECTED] Subject: RE: ShopTalk: Flat Faced Driver   Graham,   Does the face actually need to be flat, or just appear to be flat?  I recently assembled a Bang Golf Bang-o-matic 401cc head for myself, and the face on this club appears quite flat to my eye.  Not sure of the actual bulge and roll specs on the head, but it has less obvious bulge and roll than some heads I have seen.  Performance has been excellent from this head.  It is quite forgiving on toe and heel shots, and the ball seems to go dead straight (I have pushed and pulled some shots, but they go straight right or left with no additional curvature).  I have a 14* (13* Actual) head that I shafted with a R flex SK Fiber Tour Trac 90 at 44" total length.  The BOM is a deep bore head, with ~2.5" insertion depth, so it gives you a lot of flexibility with weighting and/or tip depth insertion.  It appears smaller than 401cc due to a fairly tall face, which reduces the heel/toe and front to back dimensions.  The head is getting great reviews on the FGI forum.  Good luck.     Tedd