Its a world common sense that down blow shot increases the back spin and gives more distance.
I have been no doubt for long time.
So I tried to calculate how the down blow shot increase the back spin.
After calculation , ???????. What happening? Then I think and think.
Finally I realized that its not true.
Please see below
Club loft : θ
Force to push ball by club head : F
The factor to decide the back spin value is the red color arrow size. (see fig)
(Disregard the face material or groove shape or head rotation of off-set hitting)
Then the red arrow size is
F sin θ
This formula contains only two factors.; F and θ
It shows that The factor to increase back spin is
1) bigger club loft
2) faster head speed
Its nothing to do with a down blow angle.
Down blow shot NEVER increase the back spin ! (but gives more distance)
I found surprising fact.