Slap! Crack! Dwing! Thwock!

Brandishing clubs, bats, sticks, and rackets, Design News' staffers recently vented their frustrations by going out and whacking stuff around.

It was mere coincidence that all the field investigations involved taking one thing and hitting another thing with it: We tested a golf club, a hockey stick, a softball bat, and a tennis racket--which actually have more in common with each other than you might think. Despite the widely varying objectives of each sport, the design goals from an engineering standpoint are pretty much the same.

"The basic objective is to achieve an efficient transfer of energy," says Bill Bishop, principal engineer at Wilson Racquet Sports Technology (Chicago, IL). "Best case, you'd like to have a perfectly elastic collision where there is no energy loss."

To test the effectiveness of their designs, sports equipment engineers need to know something about the characteristics of the object being struck. One design parameter they're interested in is the coefficient of restitution (or COR), which is a measure of how much energy is absorbed during impact. Testing varies by sport. For example, engineers measure the COR of a baseball by firing it against a steel plate and measuring the speed at which it bounces back; they measure the COR of a tennis ball by dropping it from a fixed height of 100 inches.

Different objects have different CORs, which are also a function of speed. As rough approximations, the COR of a baseball is 0.52 to 0.57 at 88 ft/sec; the COR for a golf ball is 0.79 at 125 ft/sec; and the COR for a tennis ball is 0.67 to 0.73 at 60 ft/sec. A COR of 1.00 indicates a perfectly elastic collision, i.e. no energy loss.

This kind of empirical testing gives engineers insight into the relative effectiveness of their designs. The end result? New technology that is becoming increasingly better at compensating for a weak backhand in tennis or a wicked slice in golf, as we amateur athletes--including two new writing talents on our art staff--discovered during our field research.

Titanium scores in hockey stick design

Rick DeMeis, Associate Editor

A few years ago I decided to upgrade my meager hockey skills. A skating school did help my mobility on the ice. But until now, I never gave much thought to upgrading my equipment. Needless to say, when the chance to test the new ProKENNEX titanium-mesh-jacketed Ti GT 8000 Pro composite-shaft hockey stick came up, my trusty wood stick quickly became history.

The GT 8000 consists of two parts: a fiberglass-jacketed, carbon-fiber-reinforced laminated wood blade and a short wooden upper handle. Both sections are hot-glued into the ends of a hollow shaft, consisting of six fiberglass and carbon-composite layers, jacketed by a titanium mesh (see diagram next page).

The exact layer arrangement varies along the length. At the bottom, an extra-carbon-plies reinforced flared "hosel" holds the wood blade in place. This part of the shaft must be the strongest, because of slap-shot forces and the need to reduce torquing on the blade.

Above the hosel is the "kick point," much like that designed into a composite-shaft golf club. A different orientation of the composite-ply layup here results in a distinct change in the bend profile.

The 8000 stick I tried out has a kick point two inches higher than the 6000 model, which has two fiberglass layers in place of one of the carbon-fiber layers. Paul Kid, VP of product development at ProKENNEX, explains that the 6000's lower kick point and greater flexibility combine to angle shots higher, allowing weaker players to achieve greater loft.

A titanium weave sheathes the shaft along its mid-length, which again changes the bending profile by stiffening and strengthening the stick. A side-load test on the stick-end hosel showed that it can sustain a 400-kg load before breaking. Other sticks only went to 370-kg loads. Interestingly, sticks cannot be designed for maximum mid-point side-load strength, to prevent players from injury.

These titanium-clad sticks are also stiff in torque. Tests with a 6.8-kg weight on an arm extending 15 cm off the stick produced an angular deflection of 2.5 to 4.0 degrees for the 8000; 3.5 to 5.5 degrees for the 6000; 4.5 to 6.0 degrees for the composite-only 1000 model; and 9.0 to 11.8 degrees for wooden sticks.

After cutting the handle end of the stick down to the length I play with, the first thing I noticed was its low weight. Other players commented on the same thing, finding it almost disconcerting at first. But a light stick means less strain on the arm or elbow, particularly when playing one-handed.

The stick's low weight and high stiffness allow putting "a lot of power" into a shot. I found the ProKENNEX lively enough that I had to pay attention to receiving passes with the proper technique--"catching" them with a slight "give" and downward twisting of the blade. Otherwise, pucks tended to bounce off my rigidly held blade.

If you're a player and inclined to a premier stick, in the same price range you may want to consider the ProKENNEX 8000 and 6000 along with other top-end models.

Stick specs

Product:ProKENNEX Ti GT 8000 Pro hockey stick
Material composition: Titanium/fiberglass/carbon composite/wood
Play weight: 1.24 lb (comparable size all-wood stick, 1.48 lb)
Retail price: $99.99
Major design innovation: Titanium-mesh jacket stiffens stick mid-shaft and protects under-layers

Editor's rating

Performance improvement: Very good to excellent. This editor and fellow players using it commented on the "power" it put into shots. Carrying such a lightweight stick takes some getting used to.
Handling: Stiffness and "kick point" (pivot point) combination produce a livelier shot. Lighter weight relative to wood sticks makes for easier handling with less potential elbow strain.
"Novelty" factor: Mention a titanium-composite stick and the comments range from "The aerospace stick," to "What'll they come up with next?"
Overall impression: A top quality piece of equipment that allows performing at peak puck-playing skills, but the retail price may be overkill for the below-to-average player.

Hybrid bat built for booming

John Lewis,l Northeast Technical Editor

Just as softball sluggers of the 1970s saw wooden bats give way to aluminum ones, now they are watching aluminum bats go the way of their lumber predecessors. Thanks to manufacturing and materials advances, a field of new "high-tech" bats promises better swings and drives.

Take the Fusion bat I tested out. It's a composite of aluminum and graphite from sporting-goods manufacturer Dudley, a unit of Spalding. Five ounces lighter than conventional softball bats of the same size, this bat has a 3 to 6 mph faster swing than aluminum bats with the same swing weight, Dudley says. On long drives, this roughly translates into an additional 10 to 20 ft of increased distance.

While claims of extra distance are as old as the game, and hard to substantiate, the main determinant will always be the person doing the swinging. Undaunted, I envisioned myself with the new bat, hitting ball after ball into the stands to the appreciative roar of the fans at Fenway Park.

I use a 29-oz aluminum beer-league bat, and I asked Dudley to send the same size bat so I could do a direct comparison. When the Dudley rep quizzed me about whether I meant swing weight, or actual weight, I had no idea what he was talking about. He explained that swing weight measures what the bat feels like in your hands while swinging, and that actual weight is the bat's scale weight. I went with the 29-oz swing weight.

When the bat arrived, the first thing I did was hold my old 29-oz aluminum in one hand and the new 24-oz actual-weight Fusion in the other. No real difference there. Then I flipped the bats over and held them by their barrel ends. The weight difference was extraordinary. Since most of the Fusion's weight is in the barrel, the aluminum bat's handle is actually quite heavy by comparison.

The Fusion's body and handle are graphite with a thin (0.065 inch thick) C-405 aluminum sheath fused to the barrel area. By using composites in the handle, explains Brian Feeney, director of product development at Spalding, engineers were able to design a bat that is lighter in weight, yet still feels like a heavier aluminum bat during the swing.

Graphite's higher strength, light weight, and directional properties allow the Fusion bat to be at least 20% stiffer in bending and 15% more flexible in hoop stiffness, and it has a better weight distribution than a single-wall aluminum bat.

So how does all this translate into better play? "Softballs are made of foam and are not very good at storing energy. When you deform them, you lose a lot of that energy," explains Feeney. "That's why we built a bat that deflects, stores the energy, and springs back during impact."

Although I did feel as though I were blasting balls into orbit with the Fusion softball bat, its design innovations were not quite sufficient enough to overcome all of the limitations of my hitting game. So with much anticipation, I'm looking forward to next year's softball season and the next new crop of equipment innovations.

Bat bio

Product name: Fusion 2 softball bat
Material makeup: C-405 graphite composite construction
Weight: 29-oz swing weight/24-oz actual weight
Retail price: $250.00
Major design innovation: Bladder molding process and materials of construction

Editor's rating

Performance improvement: Excellent
Handling: Though the Fusion is light in weight, it feels like a heavier aluminum bat during the swing
"Novelty" factor: The colors are cool
Overall impression: Although I had the sensation that I was blasting balls into orbit with the Fushion, its design innovations weren't quite sufficient enough to overcome all of the limitations of my game

Fat Shaft(TM) golf club is no slouch

William Reilly, Senior Art Director

First of all, let me say this: On the hacker's barometer, my golf game falls somewhere between Tiger Woods and "Carl the groundskeeper" from Caddyshack. So I desperately welcome any advantage on the course I can find--no matter how slight.

It was with a kind of secret glee that I recently set out for the course armed with the latest offering from Wilson: the Fat Shaft(TM) series irons.

The clubs have an unmistakable--actually let's just say weird--appearance. The feature that earns them their name is the thick shaft that travels from the butt to the tip of the club. While traditional clubs gradually taper to meet the head, the Fat Shafts appear to have the same thickness throughout.

Actually, they do taper--from a standard thickness of 0.60 inch butt diameter down to 0.50 inch at the tip. Conventional clubs, on the other hand, taper down to 0.37 inch. According to Design Engineer Frank Garret at Wilson, the 35% increase in diameter at the tip limits the twisting action of the club--by providing 75% more torsional stability than its skinnier counterparts. The trick? Optimizing the mass distribution of the shaft and head combined.

At less than 1.5 gms/inch, the hollow shaft is one of the lightest in the business. The shaft's graphite epoxy construction (a blend of intermediate modular and standard graphite) allowed designers to achieve low torque while at the same time maintaining the flex distribution of a conventional shaft.

The increased stability also provides a large sweet spot on the club face, ostensibly allowing for better results on missed hits. A low center-of-gravity also helps to get the ball airborne more easily. And, of course, the advantage of the oversized cast steel head is its larger moment of inertia--so if you do hit it off center, less rotation occurs.

My results backed these claims up. I tested a set of irons (3 iron through pitching wedge). Like many golfers, I have a bit of a slice, which I generally factor into my aim. With the Fat Shafts, I not only lost my tendency to slice, but actually managed a truer, straighter shot with greater distance.

This was particularly evident with the long irons (3-6). When reaching for the short irons, the 9 iron and pitching wedge especially, I noticed a loss of touch. It seemed as though the same technology that improved the distance and accuracy in the long irons robbed me a little of the feel of the club. My shots were straight, but gauging the distance was an adventure. This made my game a little unpredictable at times.

I didn't test the woods, but it would seem to hold true that the same shaft design that results in longer and more accurate shots in the irons would net the same results in a set of woods. Now, if only Wilson would only develop a technology that would help golfers like me avoid three-putting--then they'd really be on to something!

Clubs closeup

Product: Wilson Fat Shaft golf irons
Material composition: Graphite-epoxy shaft and cast steel head
Play weight: Graphite shaft--395 gms; Steel shaft--415 gms
Retail price: $1,060 (3-iron through pitching wedge)
Major design innovation: A larger tip diamaeter of 0.50 (35% larger than conventional shafts), providing greater torsional stability

Editor's rating

Performance improvement: Very good
Handling: Very good
"Novelty" factor: The distinctive look of the Fat Shaft clubs got a lot of notice around the course. Many golfers had heard of them, but had yet to see them.
Overall impression: The unconventional look of the clubs gave me the initial impression that they would be heavy and lacking in any aerodynamic qualities. The reality is that this set of clubs is more forgiving, allowing me to swing easier with longer drives and more accurate results.

Titanium racket serves up an ace

Michelle Barbera, Associate Art Director

As luck would have it, I had just purchased a new tennis racket when I had a chance to test out Wilson's Hammer 3.0 Titanium racket. Now, I'm considering getting the Hammer and using my first racket as a spare.

Coming from a tennis family, the competitive pressure is pretty intense, as you might imagine. Fortunately, I immediately noticed a dramatic difference with the new racket, especially on my forehand.

My two-handed backhand has always been my better stroke, but my one-handed forehand was greatly aided by the lightness of the Hammer. I no longer have to worry about dropping the head of the racket--I just concentrate on hitting through the stroke. I have found this to be particularly helpful in mid-match, at about the time my wrist and arm begin to tire.

I was surprised that even though the racket is lighter (8.5 oz unstrung) than the racket I was using, I was able to hit the ball harder--but not at the expense of control. In fact, the Hammer provides more control than other rackets with oversized heads (118 inches) that I have used. It is important to hit the ball with a good deal of top spin, but Hammer allows for some leeway in the stroke.

According to Bill Severa, a design engineer at Wilson Sporting Goods, the two elements that make the racket a standout are its power and torsional stability. Essentially, designers strategically redistributed the weight of the racket, placing more mass in the head.

It's this mass at the point of impact that, says Severa, provides more efficient delivery of energy and helps to keep the ball in play longer. "What we have essentially done is move the sweet spot up to the top half of the frame, which is where average players hit the majority of their balls," says Severa.

Designers also maintained the same moment of inertia, so that the racket swings more like a traditional light-weighted-head racket. Moving the balance point further away from the tip of the handle also makes the racket easier to maneuver.

In fact, the weight distribution made the racket feel like an extension of my arm. The effort involved in getting the ball to go over the net at a good clip is so minimal it almost feels like magic. With any other kind of racket, the same impact would cause the ball to drop to the ground short.

The racket frame is made of 100% graphite epoxy with a titanium bonding agent in the resin to strengthen the bonding between the regular and high-modulus graphite used. The patented dual-taper beam design limits the amount of energy going into the bending of the racket frame, which means more energy imparted to the ball.

Bottom line, my play has improved. And with players like Conchita Martinez and Todd Martin using Hammer rackets, I almost feel like I'm ready for the professional tour.

Racket rundown

Product name: Hammer 3.0 Titanium
Material makeup: 70% graphite/30% high-modulus graphite with titanium as a bonding agent in the resin
Weight: 8.5 oz unstrung
Retail price: $239.99
Major design innovation: Dual-taper frame design that stabilizes head higher up in the racket face, strategic weight redistribution, and use of titanium as a bonding agent

Editor's rating

Performance improvement: Great
Handling: The weight distribution made the racket feel like an extension of my arm
"Novelty" factor: The oversize head is deceptive, as you actually have more control with this racket than similar rackets
Overall impression: Great because I no longer have to worry about dropping the head of the racket--I just concentrate on hitting through the stroke.