I think the highlighted part above is an oversimplification of what Dave says, which actually is "...
lateral shaft stiffness can indirectly affect squirt by changing the effective “endmass” of the shaft. Lateral shaft stiffness can also have a direct effect on squirt since when a stiffer shaft is flexed (as the CB pushes the tip sideways), the shaft reacts with more sideways force, which can create more squirt. However, typical pool cue shafts are very flexible in the lateral direction (i.e., they don’t require much force to flex), and the shaft does not flex very much during the incredibly brief tip contact time anyway, so stiffness does not have a significant direct effect on squirt."
Another factoid for your database: I have a
conical tapered (i.e., very stiff) shaft that squirts less than any other I've tested (~20" pivot length), due solely to its low end mass (small, hollowed tip).
pj
chgo
This part, where Dr. Dave says,
"the shaft does not flex very much during the incredibly brief tip contact time anyway, so stiffness does not have a significant direct effect on squirt." makes very little sense to me.
The shaft must deflect enough to keep the cue's weight from influencing the cue ball too much. In other words, regardless of shaft end mass, if the shaft had zero flex then the cb would get max squirt because the entire mass of the cue would be pushing through the side of the cb, giving way only by whatever amount of play room or cushion there is in the bridge hand. So to say that shaft stiffness/flex is insignificant when it comes to cb squirt seems to a bit of a stretch, or at best pure guesswork.
An interesting experiment would be to test the stiffness of a LD carbon fiber shaft (a Revo) and a LD maple shaft. Then cut the last 3 or 4 inches off of each shaft and weigh the pieces with ferrule and tip. I suspect they will be very close to the same weight, but the stiffness measured in each shaft will likely be quite different. Actually, the carbon fiber would probably weigh a little less than the wood, but I wonder what the stiffness comparison would show.
Dave talks about "typical" pool cue shafts being very flexible, and even though that's true, I would say the flex properties of different shafts vary enough to cause significantly different amounts of cb squirt.
I bet if someone could test a fiberglass shaft with the same end mass as a carbon fiber shaft, the fiberglass shaft would produce less cb squirt because it is much more flexible than carbon fiber.
Anybody wanna cut the ends off your cues and weigh the pieces for us? Lol. Probably not.