tflan To answer your question, if the shaft is straight the hard side or the side with more thickness or more material will end up on top of the curvature when bent and free to rotate to the stable position. If the shaft is only bowed only the shaft will rotate into the stable position of bow down. If you have both a bow and a hard side the stable position will be an average of the two positions.
This gives me an opportunity to expound on a new approach to spine alignment I have been thinking about and formulating over the past several months. I started out believing the spine should be a 12:00 and the only cared about Flow but have converged my thinking as follows. 1. The vibration wobble and flow are not a factor in picking a spine position as well as all of these other alignment theories that are being expounded. 2. If we look at the mechanics of the system the shaft is stable as long as the shaft is loaded away from the hard side or with the bow of the shaft or an average position if the shaft has both. This assumes the load is applied on the center line of the shaft. However if the shaft is loaded in the opposite direction as just described the shaft is unstable and would tend to move to the left or right of the straight deflection path. Adding the head and loading the shaft off the shaft center line complicates the problem but there still would be a place where we could place the spine, load the shaft at the C. G. of the system and get the shaft to deflect straight back in a stable manner. The shaft head system would still be unstable when loaded the other direction. (a method of finding this position is still under consideration) If the shaft is not in this stable condition while being loaded the shaft under load will deflect off plain and then will return to the ball off plain. 3. Since the shaft is loaded in the swing and we can have the spine located in such a position the shaft goes straight back on plain it will return to the ball on plain and we will have achieved the best performance and the solution to our spine locating problems. llhack > [Original Message] > From: tflan <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Date: 10/8/03 11:16:01 AM > Subject: Re: ShopTalk: NBP-COG > > Dr Tutelman: > > A question, por favor. When this subject was broached several months ago, > and the thread unwound for about 3 weeks, I asked a question that got no > universally agreed upon answer. The question was; is the spine found at the > top of the shaft or at the bottom of the shaft when testing in Dick's spine > finder? Responses were equally, and passionately, divided. > > I then asked another question; if when one finds the spine, the "hard spot" > via the use of our arguably primitive methods, how can one accurately mark > and then place the hard spot in a specific position? As I recall, you > responded, correctly, that we'd be lucky to get the spine situated to within > 3 to 4 degrees. You mentioned the circumference of the .335" tip, when > reduced to 360 degrees, would be virtually impossible to set accurately. I > agree. An assembler would need to identify the spine at the shaft tip by > marking it with a needle, then mark the hosel in the precise finished > position. Then he'd need to mark the ferrule so the entire assembly could be > stuck together in one operation. That's nearly impossible given the > workplaces of most assemblers. > > So, this thread re; placing cog/spine in some specific location with > accuracy is theoretically interesting but in practice its pretty much > useless. I'm not knocking anyone, just making a point that's been made > several times in the past. > > TFlan > > ----- Original Message ----- > From: "Dave Tutelman" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Tuesday, October 07, 2003 10:49 AM > Subject: Re: ShopTalk: NBP-COG > > > > A few points I'd like to make concerning things that were brought up in > > this thread: > > > > (1) As Alan Brooks and John Kaufman and I have said in the past, every > > shaft will have the stiffest directions (that is, spines) at 180* > > intervals. Similarly with the most flexible directions (that is, NBP). If > > you measure anything else, there is something wrong with your measuring > > equipment. (Others have already noted that residual bend affects a spine > > finder's reading. That is probably the most common thing that is wrong > with > > your measuring equipment.) > > > > (2) FLO is important!!! It is not important because of anything the shaft > > may be doing during the swing (unlike a fishing rod), but it is one of the > > more reliable ways to find the REAL spine, untarnished by things like > > residual bend. In other words, FLO is a more reliable spine-finder than > > Colin's or Dan's. Slower perhaps, but it finds the real spine. > > > > (3) There are three theories that I have seen about why spine alignment > > matters. NBP-COG is one of them. Here's the reasoning behind it: > > * At the moment of impact, the major force bending the shaft is > > centrifugal force. (That is probably true, but not universally accepted. > > But let's proceed on the assumption that it is true.) > > * That force will bend the shaft in the plane of the CG of the clubhead, > > because centrifugal force acts through the CG of the clubhead. (In > essence, > > it is pulling the CG of the clubhead straight away from the hands.) > > * If the shaft bends in a plane where the forces due to bending are not > > in the same plane as the bending, there will be spurious torque on the > > clubhead; you don't want that. > > * But the only planes where the force and the bending are aligned are > the > > NBP and the spine plane. In other planes, there will be some small angle > > between the bending and the force in the shaft. So you need to align one > of > > those planes (either the NBP or the spine) with the CG of the clubhhead. > > > > (4) If you build your clubs with nearly spineless shafts (like SK Fiber, > or > > the new Harrisons, or many filament-wound shafts), then it makes little > > sense to say, "I used NBP-COG alignment [or any other alignment] and it > > worked GREAT!" You were aligning an effect that probably didn't matter one > > way or another. > > > > Hope this helps, > > DaveT
