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End Caps

Increased Power? No

Larger Sweet Spot? Yes

Less Annoying Vibration? Yes

End cap performance was tested for two paddles - a Six Zero Ruby and a Friday Original.  The Friday showed no increase in power with end cap weighting added.  The Ruby showed a decrease in power.  There was a favorable effect on sweet spot size and handle vibration.

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Power

An air cannon was used to propel a Penn40 ball toward two paddles at 50 +/- 1 mph - a Six Zero Ruby and a Friday Original.  The rebound velocity was measured with and without end cap weighting.  Several readings were averaged and the results plotted as a function of location on the paddle face.  This is the same type of testing used by USAP (PBCOR, Paddle Ball Coefficient of Restitution) and UPA (PEF Paddle Efficiency Factor) to measure paddle power.  

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Surprisingly, the rebound velocity of the Ruby was about a half mph less at every location.  The Ruby's power decreased.  The test was repeated for confirmation.  The addition of end cap weight on the Friday had no effect (within experimental error) on rebound velocity.   For both paddles there is no increase in power by adding weight to the handle.

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But ...........

Should we discount the views of users and podcasters that report "easier to maneuver at the net", "added plow through", "feels a little softer", "greater stability", "more pop and power"??

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The reason for the disconnect between the objective measure of less power using the air cannon and the subjective feeling of many players may be caused by the improved "feel" of the paddle after adding weight.

The rebound velocity is displayed at various locations across the paddle face.  The rebound velocity with end cap weighting is slightly less at every location for the Ruby.  It appears the same is true for the Friday. 

Annoying Vibration

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Every paddle vibrates after an impact with a ball.  It's easy to feel (and hear) the vibration by holding the butt end of the paddle between thumb and forefinger while tapping the paddle at different locations on the paddle face with the handle end of a large screwdriver.  

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The vibration is larger when tapping at the throat and tip of the paddle.  The vibration almost disappears near the center of the paddle face - you've found the "sweet spot" or the center of percussion.

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Or, if you have access to a ball machine, hold your paddle with a standard grip at the exit and feel the vibration in your hand - lots of vibration when the ball hits the tip or throat of the paddle.  The vibration disappears when the ball hits near the face center.

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An excellent animation of the "diving board" vibration can be seen in Figure 3 of Paddle Reactivity Rankings.

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To measure the amplitude and frequency of the vibration an accelerometer was attached to the handle in two places.  One, at the butt of the handle; the other at the top of the handle.    

Note:  There are two definitions of "sweet spot".  One is the location of maximum power.  The other is the location of minimum handle vibration.  The location of maximum power may or may not coincide with the location of minimum vibration.   For a detailed technical discussion see The sweetspot of a hollow baseball or softball bat by Daniel A. Russell, Ph.D.

The accelerometer is attached to the handle using the grip rubber band (black).  The location shown is near where the index finger and thumb would grip the paddle.  The alternate location of the accelerometer is at the butt end of the handle where the palm of the hand would rest.  The paddle is freely suspended on a latex exercise band (blue) to allow maximum vibration.

The vibration from an off center impact (14 inches from the butt) at about 12 mph was recorded and graphed.  The narrow initial spike (the ball impact) lasts about 2 milliseconds (0.002 seconds) after which time the ball has left the paddle face.  The "ringing" continues for more than 150 msec. 

Paddle vibration with no end cap weight lasting 150+ milliseconds after the ball impact

The vibration from an off center impact (14 inches from the butt) at about 12 mph with a 1 oz end cap weight was recorded and graphed.  The narrow initial spike (the ball impact) lasts about 2 milliseconds (0.002 seconds) after which time the ball has left the paddle face.  The "ringing" is less intense and is shorter in duration. 

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In essence, the end cap acts as a vibration damper.

Paddle vibration with 1 oz end cap weight.

The frequency content was extracted using a Fast Fourier Transform (FFT).  The frequency with the largest amplitude is 322 Hz which is in the hand  discomfort range.  Off center hits with a stock Ruby or Friday can produce hand discomfort.

The Sweet Spot

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​We all know when we've hit a ball on the sweet spot.  It feels like a "hot knife through butter".  There is little or no vibration.  The stock Ruby's sweet spot (as measured by vibration at the butt)  is 11 inches from the butt.  As the impact location moves away from the sweet spot in either direction the vibration increases. 

 

 

Adding an end cap to the Ruby significantly reduces vibration at every location and increases the sweet spot size as shown in the graph. The reduced vibration may be why players report added plow through, a softer feel, greater stability and more power.  But don't mix up the feel of reduced vibration with more pop and power - the first graph above shows no increase in rebounding ball velocity (power). 

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The Friday Original paddle shows the same improvement with the addition of end cap weight.

The vibration at the top of the handle near the throat is less intense.  There is no significant vibration reduction with the addition of end cap weight.

Summary

All paddles vibrate as the result of the paddle/ball impact.  The vibration is at a maximum at the butt of the handle where energy is transferred to the hand and upper extremities. Some players experience discomfort from the vibration and prefer vibration dampening provided by end cap weight.  The dampening provides a soft, plush feel and a wider "sweet spot"..  Other players do not use end weights and would rather have instant discernible vibration feedback indicating an off-center hit.  Contrary to popular opinion there is no increase in power with added handle weight.  

Two "hot" Pickleball Apes Pulse V "core crushed" paddles are compared to a stock Pulse V to explore the differences in performance.  Many players have noticed their paddles (multiple manufacturers) becoming more responsive and powerful with use.  Balls seem to pop off the face with more velocity.  Probably the sound has changed to a more bass tone.  You've got a "hot" and probably illegal paddle.

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Three Pulse Vs were obtained.  One, a fairly new, stock Pulse.  Two, a gently used Pulse V from Bob M.  Three, a heavily used Pulse V from Keith K.  Keith's and Bob's paddle had the distinct crackle sound when pressing in on the face indicating core crushing.

 

Each paddle was measured for KKCOR (Keith K Coefficient of Restitution) and rebound velocity using an air cannon and speed gate. 

 

 

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Core Crushed or Delaminated?

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There's some confusion about the causation of "hot" paddles - paddles that, after use, become more powerful.  Some websites blame delamination - the breakdown of the glue between the carbon fiber face layer and the polypropylene core.  Others blame core crushing - the weakening of the polypropylene core due the stress of multiple ball hits.  This article will use the term core crushed as shorthand to describe "hot paddles". 

KKCOR v PBCOR v PEF

All three metrics are similar in that they measure the coefficient of restitution (paddle power) by shooting a ball at a paddle and recording the resultant rebound speed.  The differences are the brand of ball used and the inbound velocity of the ball.  USAP calls their metric PBCOR  (Paddle Ball Coefficient or Restitution) and shoots a holeless Franklin X40 ball toward the paddle at 60 mph.  UPA calls their metric PEF (Performance Efficiency Factor) and shoots a Vulcan Pro ball toward the paddle at 50 mph.  I call my metric KKCOR and shoot a Penn40 ball toward the paddle at 50 mph.

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So, why create a third metric?  Why not duplicate USAP's or UPA's metric? 

Reason:  USAP's ball is impossible to purchase.  UPA's ball goes out of round and breaks easily.

The graph clearly shows the two crushed paddles are above the legal power limit and would be disqualified for tournament play.  The stock paddle is safely below the limit at every impact location.

The graph shows the large increase in rebound velocity for both of the core crushed paddles. 

 

There are multiple problems with core crushed paddles.

1. The increased ball speed leads to an unfair competitive advantage.

2. The increased ball speed creates the danger of eye/face injury since players are 14 feet apart at the kitchen lines and cannot react fast enough to avoid the ball.

3. The variation in ball speed with impact location creates control problems for recreational players who can't precisely contact the ball at the same paddle face location.  For instance, the difference in rebound speed for the stock paddle at 4.8" v 2.8" is 1.5 mph (10-8.5).  The difference in rebound speed for Keith's crushed paddle at 4.8" v 2.8" is 3.2 mph (18.2-15) making the ball more prone to hitting the net or becoming a pop-up.

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