Weight and frequency variations between different samples of the same blade, what is the effect on the sweet spot?

[Larshos]

Given that you have two samples of the same blade, X grams between them and a somewhat proportional difference in frequency as well, will the lighter of heavier one have the biggest sweet spot?

I know that in tennis and badminton, higher stringing weight means higher frequency, meaning more power, but a smaller sweet spot - so beginners should keep the stringing weight fairly low.

But then i google this correlation for TT blades, I read that a more flexible blade usually have a smaller sweet spot, and I might be wrong or oversimplifying here, by assuming that a lower frequency blade will have lower stiffness, and vice versa.

Is this correct? Will the differences between samples of the same model be noticeable, or completely negligible?

Hope someone with more knowledge on this can chime in here

 

[Dr Evil]

Given that you have two samples of the same blade, X grams between them and a somewhat proportional difference in frequency as well, will the lighter of heavier one have the biggest sweet spot?

If the extra mass is mostly in the head (especially toward the tip/perimeter), the blade’s polar moment of inertia about its center increases, so off-center hits produce less angular acceleration. That makes the sweet spot feel larger. If the extra mass is in the handle, the moment of inertia barely changes, so the sweet-spot size won’t meaningfully grow (though the blade may feel a bit more solid from lower vibration).

... I read that a more flexible blade usually have a smaller sweet spot, and I might be wrong or oversimplifying here, by assuming that a lower frequency blade will have lower stiffness, and vice versa.

Is this correct? Will the differences between samples of the same model be noticeable, or completely negligible?

Stiffness/torsional rigidity usually matters more than total mass, which is why larger sweet spots correlate more with carbon composite layers, thicker plies, larger head sizes, etc., than with weight alone. But I don't think a higher pitch/frequency correlates reliably with a larger sweet spot because for example a larger head or perimeter mass can expand the sweet spot while lowering pitch.

 

[Larshos]

If the extra mass is mostly in the head (especially toward the tip/perimeter), the blade’s polar moment of inertia about its center increases, so off-center hits produce less angular acceleration. That makes the sweet spot feel larger. If the extra mass is in the handle, the moment of inertia barely changes, so the sweet-spot size won’t meaningfully grow (though the blade may feel a bit more solid from lower vibration).

Stiffness/torsional rigidity usually matters more than total mass, which is why larger sweet spots correlate more with carbon composite layers, thicker plies, larger head sizes, etc., than with weight alone. But I don't think a higher pitch/frequency correlates reliably with a larger sweet spot because for example a larger head or perimeter mass can expand the sweet spot while lowering pitch.

Lets do some assumptions then:
The blades are identical, but have different frequencies. The extra weight of the one sample with higher pitch is evenly distributed along the entire blade, the handles are identical.

 

[Dr Evil]

Lets do some assumptions then:
The blades are identical, but have different frequencies. The extra weight of the one sample with higher pitch is evenly distributed along the entire blade, the handles are identical.

All else equal (including stiffness, geometry, and identical handles), adding evenly distributed mass across the head increases the mass polar moment of inertia so the sweet spot will feel slightly larger. But the tap/bounce pitch will be lower; increasing mass without changing stiffness raises the effective inertia, so frequencies (pitch) decrease.

 

[Tyce]

But increasing mass without increasing volume will create more stiffness

 

[Larshos]

All else equal (including stiffness, geometry, and identical handles), adding evenly distributed mass across the head increases the mass polar moment of inertia so the sweet spot will feel slightly larger. But the tap/bounce pitch will be lower; increasing mass without changing stiffness raises the effective inertia, so frequencies (pitch) decrease.

No, not just the head, the entire laminate of the blade, including the part that's hidden by the handle pieces.

If we ignore the mass polar moment:
I have two 5 ply blades. Same model. One is 3 g more in weight and have 80-100 Hz higher frequency.
If I were to clamp both blades in a MASSIVE vice, by their entire handle length, and I could somehow, by dropping a ball, or using a hammer with an audio analyzer etc. measure the size of the sweet spot, which of the blades would have the bigger one?

 

[Dr Evil]

No, not just the head, the entire laminate of the blade, including the part that's hidden by the handle pieces.

If we ignore the mass polar moment:
I have two 5 ply blades. Same model. One is 3 g more in weight and have 80-100 Hz higher frequency.
If I were to clamp both blades in a MASSIVE vice, by their entire handle length, and I could somehow, by dropping a ball, or using a hammer with an audio analyzer etc. measure the size of the sweet spot, which of the blades would have the bigger one?

Probably the heavier, higher-pitch blade, but not definitely.

Pitch mostly tracks bending (especially the head bending like a shallow trampoline). Sweet spot mostly tracks twisting. So if bending stiffness increases, but torsional stiffness decreases, then you can have a heavier, higher pitch blade with a smaller sweet spot. This might plausibly happen with variations in the wood grain, glue lines, etc., that stiffen bending but lighten or weaken the perimeter.

 

[Colestt]

All I can tell you is the lower frequency will have more dwell

 

[Dr Evil]

All I can tell you is the lower frequency will have more dwell

Usually but not always.