Trapezoidal cross sections in modern player's racquets

[PistolPete23]

I was at my local tennis shop yesterday browsing some of the newer frames. I noticed that nearly none of the recent players racquets are true box beams at the throat. Instead, the beam is flat facing the outside, but triangular facing the inside (i.e. trapezoid). Does anyone know the reason for this trend in construction? Improved aerodynamics? Does it actually make a significant difference? For aesthetic reasons only, I prefer either true box beam construction or an elliptical construction. Hoping that true box beams do not phase out completely ...

 

[PBODY99]

@Pistol Pete

The use of shapes allow designers to get the flex the want in locations to give the "feel" they are looking for.

 

[1HBHfanatic]

aerodynamics!

 

[One Handed Dynasty]

@Pistol Pete

The use of shapes allow designers to get the flex the want in locations to give the "feel" they are looking for.

Could you explain that more? I’ve always used box beams and liked the feel, do certain shapes correlate with certain flex locations?


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[Pmasterfunk]

Could you explain that more? I’ve always used box beams and liked the feel, do certain shapes correlate with certain flex locations?


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In hopes of answering your question, I'll also try and clear up some potential misunderstandings.

If you have a bunch of racquets that are all magically identical except for the cross sectional shapes, they should all flex at the "same location", meaning the racquets should all deflect at all points of the racquet in the same manner, and should theoretically "feel the same", at least in a friction-less vacuum type scenario.

The issue in comparing cross-sectional shapes is that no 2 frames will have identical properties except for cross-sectional shape, and basically every aspect of a racquet will affect that mysterious thing called "feel". Head size and shape, string pattern, twistweight, balance, swing weight, damping, grommets, aerodynamics... maybe even that nice paint does something? *cough cough* Wilson *cough*

What seems to happen, however, is that box beam racquets usually fall into a certain niche, and people looking for a certain type of product. It may not have been the first, but the PS 6.0 is sort of a reference for using woven carbon fibre instead of unidirectional fibres, which many (if not most) racquets use. For the same longitudinal stiffness, the woven cross-section will have more torsional stiffness. This does not mean the racquet will automatically be torsionally stiffer however, (other things can affect this, like throat shape and head shape) but it probably has an impact on how the racquet feels and plays.

TL;DR The "box beam" feel probably has more to do with targeted consumers and product history than the physics of reproducing "feel".

 

[A_Instead]

Can achieve same strength with less material..

 

[PistolPete23]

Could you explain that more? I’ve always used box beams and liked the feel, do certain shapes correlate with certain flex locations?


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I haven't tried, but you can demonstrate with basic cantilever-beam calculations that higher stiffness can be achieved by altering the shape of the beam cross section. I'm sure racquet companies use more advanced finite element simulation models to design for this. During the wide-body craze of the 90s, companies combined high-aspect ratio beams with high modulus graphite to achieve high stiffness and also reduce racquet weight. But the players racquets have always been more or less box-beamed with a constant beam thickness. I can't think of a reason for the trapezoidal shape though other than to reduce the drag coefficient; as @A_Instead mentioned, perhaps it also allows for slightly less material to be used without compromising stiffness.

 

[One Handed Dynasty]

In hopes of answering your question, I'll also try and clear up some potential misunderstandings.

If you have a bunch of racquets that are all magically identical except for the cross sectional shapes, they should all flex at the "same location", meaning the racquets should all deflect at all points of the racquet in the same manner, and should theoretically "feel the same", at least in a friction-less vacuum type scenario.

The issue in comparing cross-sectional shapes is that no 2 frames will have identical properties except for cross-sectional shape, and basically every aspect of a racquet will affect that mysterious thing called "feel". Head size and shape, string pattern, twistweight, balance, swing weight, damping, grommets, aerodynamics... maybe even that nice paint does something? *cough cough* Wilson *cough*

What seems to happen, however, is that box beam racquets usually fall into a certain niche, and people looking for a certain type of product. It may not have been the first, but the PS 6.0 is sort of a reference for using woven carbon fibre instead of unidirectional fibres, which many (if not most) racquets use. For the same longitudinal stiffness, the woven cross-section will have more torsional stiffness. This does not mean the racquet will automatically be torsionally stiffer however, (other things can affect this, like throat shape and head shape) but it probably has an impact on how the racquet feels and plays.

TL;DR The "box beam" feel probably has more to do with targeted consumers and product history than the physics of reproducing "feel".

Wow thanks for taking the time to write that detailed response! You’re definitely right that the PS 6.0 was the start of a new branch of feel, in terms of layup, foam filled, box beam, and the rest. I think that’s why so many former pro staff users like Angell: foam filled, high quality graphite and paint, and each of the TC series has a unique flex profile.

I wonder if the Clash has it’s unique throat for the free flex effect.


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[One Handed Dynasty]

I haven't tried, but you can demonstrate with basic cantilever-beam calculations that higher stiffness can be achieved by altering the shape of the beam cross section. I'm sure racquet companies use more advanced finite element simulation models to design for this. During the wide-body craze of the 90s, companies combined high-aspect ratio beams with high modulus graphite to achieve high stiffness and also reduce racquet weight. But the players racquets have always been more or less box-beamed with a constant beam thickness. I can't think of a reason for the trapezoidal shape though other than to reduce the drag coefficient; as @A_Instead mentioned, perhaps it also allows for slightly less material to be used without compromising stiffness.

Haha I think I’ll take your word for it. Yeah I noticed how racquets went from the box beam, to box beam with flanges, to a geometric rainbow now. Trapezoidal is strange. I know triangle is the strongest shape, hence the D-beam that’s prevalent on some racquets, so maybe trapezoidal is in between square and triangle?


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[Pmasterfunk]

Wow thanks for taking the time to write that detailed response! You’re definitely right that the PS 6.0 was the start of a new branch of feel, in terms of layup, foam filled, box beam, and the rest. I think that’s why so many former pro staff users like Angell: foam filled, high quality graphite and paint, and each of the TC series has a unique flex profile.

I wonder if the Clash has it’s unique throat for the free flex effect.


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There's a lot of mumbo jumbo floating out there about racquet "feel" and "performance", and not that many people understand even some basic solid mechanics (which, to be fair, is still fairly complicated) - let alone the dynamic behaviour of a racquet/string/ball system - that affect racquet behaviour.

I have little knowledge of the numbers behind tennis racquet construction (i.e. layers and direction of graphite, type of epoxy, target stiffness in actual non RA numbers), but I have made some skis, and it's not that hard to make a pair of skis similar to something you can buy with a bit of trial and error.

Speaking of the Clash, I just read it had 45 different prototypes before settling on the production model. Basically, you aim for feel/performance in your design, then build, test, tweak, and repeat.

So if you're trying to design a racquet play like a PS 6.0, don't go looking at an APD for design insight. Save yourself some trouble and look at a PS 6.0.