Spin Loft is the loft responsible for SPIN!! (as implied from the name).
It is an intrinsic parameter for a club. It is the combination of the static loft on the clubhead and the loft imparted by the shaft on the clubhead at impact. In general, spin loft will be more than static loft.
(Ideally, this should be defined as dynamic loft, as this is the loft of the club head in motion and leave AA alone as defined by Dave Tutleman years before Trackman. But, Trackman has their own definition of dynamic loft and it is a bit confusing.)
The better way to remember is (using Trackman nomemclature)
Dynamic loft = Spin loft + AA (all assuming contact point is at the CG)
If Spin Loft is an instrinsic parameter for a club, what don't they stamp the number on the botton of the driver like they do for Static Loft?
Does Tutleman have a term for where the face is pointing at impact?
You mentioned Tutleman's definition of AoA. What is it?
Spin loft is the difference between AoA and dynamic loft. If you have a level strike and deliver 20 degrees of loft your spin loft is 20. If you hit up on the ball 5 degrees and deliver 20 degrees of dynamic loft your spin loft is 15 degrees. You can up up, level or down and not increase or decrease spin if this "spin loft" number stays the same. The only thing that would change with a center hit would be vertical launch angle.
Spin loft is the difference between AoA and dynamic loft.
In another thread, Brian goes on to correct my definition to what I posted above, which makes more sense.
Sorry Kevin, I gotta disagree with you. Spin Loft is not only a vertical measurement, rather an angular differential along the face of the D-Plane.
Vertical Face (Dynamic Loft) - Vertical Path (AoA) = "Vertical Differential"
Horizontal Face - Horizontal Path = Horizontal Differential
3D Face - 3D Path = Spin Loft
No, this is wrong. Spinloft is the angular difference between two vertical components only, Attack Angle and Dynamic Loft. The horizontal components are not involved.