Paddle flythrough
The video shows a flythrough of an actual paddle — constructed from a tightly spaced series of CT-Scan slices.
As expected we see a more in depth version of the Compound saw cross section we saw before.
What is core crushing and does it still exist?
If you haven't got the patience to read this - here's a summary.
TL;DR - Despite hulk-like banging efforts nobody actually crushes cores - they are crushed during production due to a combination of bad materials QC and out-of-spec temperatures. QC has been tightened up and processes altered and for most major brands it's no longer a significant problem.
But let's unpack that a bit shall we.
As recently as a few months ago — core crushing was a frequently discussed topic. Delaminated paddles getting banned in tournaments, USAP introducing new equipment to test for this, paddle nerds all over the picklesphere squeezing their paddle faces with their thumbs like this and declaring their paddles dead: (image courtesy of Chris Olson)
But suddenly it’s not being talked about as much — except where some players consider it a veritable badge of honor to say they CRUSH PADDLES because they think it means they are destroying the core by the power of their fearhand.
Well, regardless of how much it was discussed — while the effects of core crushing were understood (paddles got softer, then became illegal) the causes were not particularly well understood — so we thought it was worth taking a step back and explaining what is actually taking place, since, as with many things in pickleball there is a lot of misinformation/confusion out there.
So with that in mind — let’s talk about WHAT WE SEE — then we take a guess as to WHY and finally — DOES IT STILL EXIST.
What do we see?
Let’s start with some definitions:
A standard Thermoformed Pickleball paddle (Gen 2 — if you’re inclined to count that way) resembles a standard laminated composite panel (and so it should because the design was lifted from aircraft panels back in the day) usually composed of a Polypropylene (PP) — honeycomb core and 3 layers of carbon fiber on either side (e.g. Unidirectional T700 100gsm Carbon Fiber in a 0–90–0 configuration). FWIW these carbon fiber layers are called plies. So the skin of a pickleball paddle is a 3 ply laminate.
If you look at the diagram above you can quickly identify which bits are which — and briefly consider what is happening when a pickleball paddle is deemed to be core crushed or delaminated.
Hmmm — where to begin.
For the sake of exactness — delamination — would be Type A damage — a separation of the carbon fiber plies from each other. To the best of my knowledge (and everyone I have spoken to) this has NEVER HAPPENED TO ANY PICKLEBALL PADDLE.
Which makes some sense — because the Carbon Fiber plies are encased in a single resin matrix and the resin bonds very well to itself.
However Type B and Type E damage — disbonding — the separation of the outer plies from the core — is an extremely likely culprit. One of the biggest reasons for this is that Epoxy resin does not bond very well to Polypropylene.
Curiouser and curiouser.
So we are observing DISBONDING (which allows the normally rigidly laminated layers to move independent of each other) but we’re clearly also observing crushed core — TYPE D Parallel type.
Yes the industry calls it all of this stuff Delamination or Delam — and while that is technically wrong — the lexicon doesn’t matter anywhere near as much as understanding what is actually happening.
Brief aside here for the other type of crushed core — TYPE C in-plane — In general this only happens proximally to the edge foam in a thermoformed paddle — which means you can only see it if you rip off the facesheets…or…use an X-ray like we did below ;) - as carbon fiber is transparent to X-ray wavelengths.
Bottom line — when thermoformed paddles start to degrade — something happens and the facesheets disbond from the core and then the paddle feels more soft, becomes more powerful (due to significant trampoline effect) and eventually becomes uncontrollable.
It is precisely this disbonding that USAP was/is testing for with the Bondmaster 600
Plenty of issues with the usage and calibration of that kind of tool — but that’s a story for another article.
Why all this happens?
So all of that stuff above was table stakes you needed to understand for the next bit — namely how do cores get crushed?
Look at the above picture and read the caption — Which one of these got crushed by a player?
The answer is NEITHER OF THEM.
The picture above shows two paddles cut in half — the top paddle is a Hyperion CFS 16 (which is not thermoformed in the traditional way), the bottom paddle is a Thermoformed Gen 2 — from one of the earliest batches.
On the top paddle you can see that the vertical walls of Polypropylene honeycomb cells are more or less perfectly straight. This is good. It means that the walls are strong and stable.
On the bottom paddle you can see lots of TYPE-C in-plane crushing.
This much was known. But understanding further required science and some expensive toys.
It’s important to note that NEITHER of these paddles has hit a single ball.
After some analysis of the production/molding process we (and by we I mean those of us in the industry in whose interest it is to fix these problems) collectively figured out that there are at least two key issues that were causing core deformation during molding:
- THICKNESS OF RAW MATERIALS
Imagine this: If the mold expects 14.3mm Polypropylene and your supplier gives you 14.6mm and you don’t measure it (every. single. time) — that means you’ll get 0.3mm of extra material that gets squeezed by the mold. (Just imagine trying to close a suitcase with one-too-many items of clothing inside) - TEMPERATURE/TIME OF CURING
The softening point of Polypropylene is very close to the temperature required to cure the epoxy resins used in Pickleball paddle manufacture — so if a factory decides to go a little faster by increasing the temperature so the resin cooks off faster — well you can take a guess what happens to the polypropylene.
But wait, there’s more.
Even for the people who thought about it — the accepted conventional wisdom was that the molds were crushing the Polypropylene and therefore weakening it. This seems like a plausible reason.
After all — nobody could know for sure without looking INSIDE the paddle in great detail after it has been made.
Well — we don’t have Superman — but we do have Multimillion dollar CT-Scanning devices ;)
But if we look very very closely at this a different picture emerges:
This is a single slice CT-Scan THROUGH the layer of the same Thermoformed core-deformed paddle you saw earlier.
Pay attention to where exactly the slice is.
The thin green line on the bottom left image — shows you which plane the top left image is showing.
Looks fine. All cells look more or less correctly shaped and very honeycomb-y.
But now let’s look at a slice lower down:
Again — pay attention to where exactly the slice is. It is much lower down — close to the edges where the deformation is visible in a Compound Saw cross-section.
And now we have the final piece of the puzzle.
The cell structure is no longer honeycomb — because the pretty honeycomb cell cylinders have SEPARATED.
They have become unglued from each other. And thus they are much weaker.
Buckling Coke can
Much like the old experiment of a buckling soda can the cells are SIGNIFICANTLY more stable when they are connected together. when they are separated they immediately weaken.
All this said — the data seemed to point in an obvious direction:
- The Polypropylene was exposed to temperatures which unglued the cells from each other — IN-PLANE!!!
- At that point the cells became significantly weaker — and problems with inbound QC of material would be amplified.
Does this still exist?
Chris Olson recently ran a poll asking fans/viewers to vote on how often their paddle is core crushed and the numbers were extraordinarily low — even among his self-selected early adopter group — who was reporting multiple cases of core-crushing less than 12 months ago.
So what changed? The answer is simple. The factories got yelled at sufficiently and got their act together.
- More care in supplier selection.
- More usage of calipers to audit inbound material shipments.
- A less laissez faire attitude to manufacturing specs and temperatures.
Are there still some factories that want to maximise every possible sliver of margin and will push the limits and deliver core crushed paddles?
Yes.
It’s China after all. That is their way.
But for reputable factories, like the one we use at Reload (and share with a few other notable brands) — Gen 2 Thermoforming core crush (whether you understand exactly what causes it or not) seems to be a thing of the past.